CA1095964A - Radiant energy to electrical power conversion system - Google Patents
Radiant energy to electrical power conversion systemInfo
- Publication number
- CA1095964A CA1095964A CA286,102A CA286102A CA1095964A CA 1095964 A CA1095964 A CA 1095964A CA 286102 A CA286102 A CA 286102A CA 1095964 A CA1095964 A CA 1095964A
- Authority
- CA
- Canada
- Prior art keywords
- cathode
- anode
- transducer
- face
- housing
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
Classifications
-
- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02N—ELECTRIC MACHINES NOT OTHERWISE PROVIDED FOR
- H02N3/00—Generators in which thermal or kinetic energy is converted into electrical energy by ionisation of a fluid and removal of the charge therefrom
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
- H01J45/00—Discharge tubes functioning as thermionic generators
Abstract
"Abstract of the Disclosure"
A radiant energy to electrical power thermionic conversion system using a transfer structure with very closely spaced cathode and anode elements in a vacuum to minimize space charge buildup and to optimize cross transfer of elements from cathode to anodes. The materials chosen are for a high work function high melt temperature cathode, tungsten for example with a work function of 4.52 volts, and an anode with a relatively low work function, typically a silver-oxide substrate with a coating of cesium as an anode face deposited in a copper heat sink conductor yielding, with the anode face, a work function approximating .75 volts.
A radiant energy to electrical power thermionic conversion system using a transfer structure with very closely spaced cathode and anode elements in a vacuum to minimize space charge buildup and to optimize cross transfer of elements from cathode to anodes. The materials chosen are for a high work function high melt temperature cathode, tungsten for example with a work function of 4.52 volts, and an anode with a relatively low work function, typically a silver-oxide substrate with a coating of cesium as an anode face deposited in a copper heat sink conductor yielding, with the anode face, a work function approximating .75 volts.
Description
5~36~
This invention relatl-s in general to solar energy and, in particular, to highly efficient radiant-energy-to-electrical-power transducer equipped solar energy systems.
The recent energy crisis anril fuel shortagès have re~ulted in a considerable amount of attention being focused on energy, i~s availabil;ty an~ use. The primary reason for this is because it is finally being realized that energy ultimately determines the very life style of each individual with energy being a primary element determining financial systems, governrr~ents, and nations.
The two basic reasons for the increased attention on energy are supply and risk. Supply in the realiz~tion that the source, now being used most extensively, is not inexhuustible. In fact some nations are completely without oil except forimports; others import more than they pn~duce; and finally, since the petroleum pr duction cycle is not self regenerative, at some time ir~ the future, ail oil could be totally consumed. The other raason for increased attention, risk, is brought about by the realization o~ the threat to the environment s~nd, in some cases, the possibility of catastrophic ex~losions by some energy forms. The residue from the combusrion of coal and gasoline pollute the air and thermal and other wastes from nuclear energy pollute water in streams and rivers.
For the a~ove concerns and reasons, it would be highly desirable to find another source of energy and the means to transduce, control, and to use it to replace and augment the energy supplies now in use. Such an energy source shouldnot only alleviate the concerns expressed above~ but also compete successfully with the advantages ~erived from the energy sources presently in use such as low cost, reliability, conven;ence, versatility, and efficiency.
Solar energy is much more available than any other form of energy. The radiation from the sun falls on every square foot of the earth's surface. The radiation intensity may vary ~ith the declination angle of the sun, !atitude, claud cover,time of day, etc. Howeve, these parameters only vary the amount of energy.
The total supply is inexhau!itible, or if not, ther~ will be no need for energy. Further, there are no by-products oF the solar process to pollute the atmosphere, and the process is not danaerously critical, such as to present explosion and/or radiation catas-trcphe problems.
Any product using electricity as an energy inptJt is a suit~-~ble candidate fol a solar energy to electrical eriergy conversion process and wilh highly efficient solar energy processing many products previcusly not designed for electric powermcy be chan~ed to use electricity.
An erfit ient solar energy process can prove to ~e much m~r~ convenient than ~ther erlergy sources in many areas. For example, if a building is heated by the solar process, it would not require deliveryr stc,rage, and there would be no running out of fuel as there would be with coal and fuel oil. If an irrigation pum~
is needed in a remote location and it i5 desired to move the pump to different locations, the solar energy proce~s would provide much more convenience than either an electric pump with energy supplied by the power company or an internalcombustion engine driven pump. Power company wouid requira distribution lines to each location with the exact site located, whereas, the solar process would be completely versatile to any location. The internal combustion engine powered pump could be pluced in remote locations, but would require the fuel to be replenished after a given time of use, while some solar energy process systems would be completely self-sustaining. Efficiency of systems has been a major palameter that has been used primarily in connection with size and temperature constraints. This is still the case and the new solar process compares quite fa~orably with other processes ancl it is especially true if the refining plant and storage areas for gasoline and the generating plants ancl transmission lines fore!ectricity are taken into account.
The cost of the basic supply for solar energy is free. The maintenance cost for the transducer is very low and life is extremely long, making the life cyeleco~t of the product very low. This makes thq cost of this process much less thanpetroleum where there is cost involved in geo-physical exploration to find o!l, cost of buying the oil from the owner; cost of drilling and pumping the oil; cost of trartsporting, storing and refining ~he oil; and the cost of distribution of the refined 9596~L
product. A similar analysis could be made for generating electricity by a power company. All of the above costs for petroleum would only adcd up to the fuel cost at the input to the power generation station. To this cost would have to be added the cost of the generating plant, transmission and distribution. Since 5 the solar energy is available at the location of use, i~ is easily seen that solar energy is inherently cheaper than petroleum or commercial electricity.
It is, therefore, a principl object of this invention to provide highly efficient radiant energy to electrical power conversion transducers suitable foruse in solar energy systems.
Another object with use of such energy conversion transducers in solar energy systems is to reduce dependency on other form~ of energy.
A further object is to reduce poluticn and energy material hazard problems through use of applicant's relatively safe solar energy system.
Another object is to provide an energy power system p!aceable almost 1:~ anywhere having minimal maintenance and substantially no supply requirements.
Any product using electricity as an energy input is a suitable candidate for a solar eneray conversion process and with highly efficient solar energy processing many produts previou~ly not designed for e`ectrical power may be changed to use electric ty.
Still another object is to provide an energy source which can supply most househoid power demands, thus releasing th~t portion of the limited petroleum derived supply now used for power generation and heating for use in transportation or other fields.
Features of the invention useful in Qccomplishing the above objects include,
This invention relatl-s in general to solar energy and, in particular, to highly efficient radiant-energy-to-electrical-power transducer equipped solar energy systems.
The recent energy crisis anril fuel shortagès have re~ulted in a considerable amount of attention being focused on energy, i~s availabil;ty an~ use. The primary reason for this is because it is finally being realized that energy ultimately determines the very life style of each individual with energy being a primary element determining financial systems, governrr~ents, and nations.
The two basic reasons for the increased attention on energy are supply and risk. Supply in the realiz~tion that the source, now being used most extensively, is not inexhuustible. In fact some nations are completely without oil except forimports; others import more than they pn~duce; and finally, since the petroleum pr duction cycle is not self regenerative, at some time ir~ the future, ail oil could be totally consumed. The other raason for increased attention, risk, is brought about by the realization o~ the threat to the environment s~nd, in some cases, the possibility of catastrophic ex~losions by some energy forms. The residue from the combusrion of coal and gasoline pollute the air and thermal and other wastes from nuclear energy pollute water in streams and rivers.
For the a~ove concerns and reasons, it would be highly desirable to find another source of energy and the means to transduce, control, and to use it to replace and augment the energy supplies now in use. Such an energy source shouldnot only alleviate the concerns expressed above~ but also compete successfully with the advantages ~erived from the energy sources presently in use such as low cost, reliability, conven;ence, versatility, and efficiency.
Solar energy is much more available than any other form of energy. The radiation from the sun falls on every square foot of the earth's surface. The radiation intensity may vary ~ith the declination angle of the sun, !atitude, claud cover,time of day, etc. Howeve, these parameters only vary the amount of energy.
The total supply is inexhau!itible, or if not, ther~ will be no need for energy. Further, there are no by-products oF the solar process to pollute the atmosphere, and the process is not danaerously critical, such as to present explosion and/or radiation catas-trcphe problems.
Any product using electricity as an energy inptJt is a suit~-~ble candidate fol a solar energy to electrical eriergy conversion process and wilh highly efficient solar energy processing many products previcusly not designed for electric powermcy be chan~ed to use electricity.
An erfit ient solar energy process can prove to ~e much m~r~ convenient than ~ther erlergy sources in many areas. For example, if a building is heated by the solar process, it would not require deliveryr stc,rage, and there would be no running out of fuel as there would be with coal and fuel oil. If an irrigation pum~
is needed in a remote location and it i5 desired to move the pump to different locations, the solar energy proce~s would provide much more convenience than either an electric pump with energy supplied by the power company or an internalcombustion engine driven pump. Power company wouid requira distribution lines to each location with the exact site located, whereas, the solar process would be completely versatile to any location. The internal combustion engine powered pump could be pluced in remote locations, but would require the fuel to be replenished after a given time of use, while some solar energy process systems would be completely self-sustaining. Efficiency of systems has been a major palameter that has been used primarily in connection with size and temperature constraints. This is still the case and the new solar process compares quite fa~orably with other processes ancl it is especially true if the refining plant and storage areas for gasoline and the generating plants ancl transmission lines fore!ectricity are taken into account.
The cost of the basic supply for solar energy is free. The maintenance cost for the transducer is very low and life is extremely long, making the life cyeleco~t of the product very low. This makes thq cost of this process much less thanpetroleum where there is cost involved in geo-physical exploration to find o!l, cost of buying the oil from the owner; cost of drilling and pumping the oil; cost of trartsporting, storing and refining ~he oil; and the cost of distribution of the refined 9596~L
product. A similar analysis could be made for generating electricity by a power company. All of the above costs for petroleum would only adcd up to the fuel cost at the input to the power generation station. To this cost would have to be added the cost of the generating plant, transmission and distribution. Since 5 the solar energy is available at the location of use, i~ is easily seen that solar energy is inherently cheaper than petroleum or commercial electricity.
It is, therefore, a principl object of this invention to provide highly efficient radiant energy to electrical power conversion transducers suitable foruse in solar energy systems.
Another object with use of such energy conversion transducers in solar energy systems is to reduce dependency on other form~ of energy.
A further object is to reduce poluticn and energy material hazard problems through use of applicant's relatively safe solar energy system.
Another object is to provide an energy power system p!aceable almost 1:~ anywhere having minimal maintenance and substantially no supply requirements.
Any product using electricity as an energy input is a suitable candidate for a solar eneray conversion process and with highly efficient solar energy processing many produts previou~ly not designed for e`ectrical power may be changed to use electric ty.
Still another object is to provide an energy source which can supply most househoid power demands, thus releasing th~t portion of the limited petroleum derived supply now used for power generation and heating for use in transportation or other fields.
Features of the invention useful in Qccomplishing the above objects include,
2~ in a radiant energy to electrical power conversion system, a transducer structure with very closely spaced cathode and anode such as ta minimize space charge buildup and associated problems and to optimize cross transference of electrons from the cathocle to the anode. The optimized temperature area of operation is quite high approaching the melting point of cathode material in the operating area thereof. This is c~ccomplished with solar radiated energy concentrated by 5~6~
mirror or lens focused beams of energy to a high energy elevated temperature spot on the c~thode of the transducer used in a thermior~ic conversion of solar energy toelectricity. The process is very reliable with no movin~ parts in the solar energy transducer cnd with no pro~:esses inherentl~ unstable ond self~
5 destructive, such as thermal runaway in a transistor. The solar ra~iation driven process is a clean approach making use of the in'!7erent properSies of materials, relatively easy to control, and with iife of components used in the thermioniG process extremely long. The transducer i5 made up of the catt`lode, an anode, and a housing such as to permit a v~cuum to exist lO between the cathode and anode with cathode materials ;elected for advan-tageous work functions and high temperature capabiliti0s. A typical cathode material is tungsten with a work function of 4.52 volts and a melting tempera-ture of ~53 degrees kelvin and an anode face opposite the cathode may be, for example, a silver-oxide base with a coating of .ç~siumwith this composite 15 anode face af,ixed to a copper heat sink conductor. This ,~rovides an anode face work function of .75 valts. With the transducer the value of voltage of the work function of the cathode and the work function of the anode.
Specific embodiments representing what are presently regarded as the best mode of cr~rrying out the invention are illus~;r~ited in the accompanying 20 drawings:
In the drawings:
Figure I represents a side elevation semi schema~ic showing of a solar to electrical power thermionic cor~v~rsion system using a polar axis mounted reflective mirror solar radiation concentrator and transducer supplying electrical 25 pow~r to a load;
Figure 2, a similar system using a lens in place of the mirror as a sola- radiation concentrator;
Figures 3 and 4, cut away and sectioned showin~3s of alternate traniducer embodiments useable in the solar systems of F; gures I and 2 circuit 30 connected to using loads;
Figures 5 and o, end and slde views of yet another transducer embodiment with cooling fins projecting from tihe anode;
Figure 7, a partial cut awuy and sectioned vi~sw of a section of the cathode facing end of an anode useable in the transducer embodiments of Figures 3,4,5 ond 6;
Figures 8,9, and 10, side elevation cut away section, a sectioned view on line 9-9, and the anode connector end view of another transducer;
Figure 11~ a schematic showing of a solar to ~ tric power system with the load in the form of a light;
Figures 12 and 13, alt~rnut~ air conditioning systems driven by solar ther-mionic conversion systems backed up by a convention~l power supply system;
Figure 14, a solar thermionic system driving an electric pump;
Figure 15, a solar thermionic system powering a florescent lamp;
Figure 16, a solar thermionic powered electrical radiant heating system; and, Figure 17, a solar thermionic powered electrical heater to boiler hot water heating system .
Referring to the drawings:
The polar axis mcunt structure 20 for a solar syst~sm 21 of Figure I, mounts a reflective dish 22 focusing solar radiation to a concer~trated beam area impinging on the cathode end 23 of transducer 24. The support structure 20 is equipped to track the sun during daylight hours through appropriate articulatiorl drive and control structure of a conventional nature (detail not shown) so as to keep the focused spot from migration out of the desired transducer 24 cathode opera~ional area limits.
Transducer 24 is mounted in proper focal position by mounting arm; 25 attached to the rim of mirror dish 22, and is shown, schematically, to be elec,rically connected to a load 26.
The embodiment of Figure 2, is much the same as that of F~gure 1, with however, a lens 27 mounted in rim 28 used in place of the mirror clish 22. Sincethe balance of the solar system 21 is substantially the same as with the embodiment of Figure I the identification numb,srs are the same as well as the respective functions thereof.
~L~9~
The transducer 24 of Figure 3, such as may be ~nounted in the soi~r sy~tem of Figure I or Figure ~ is shown to include a housing ~) enclo~ing a cathode 30 und an ~node 31 In an evacuated environment with the catkode 30 qnd the anode 31 electricnlly connected to a using load 20. Housing 25 is generally cylindrical 5 wi,h an innel annular shoulder 32 acting as a spacer fcr the cathode 30 and anode 31 to insure close predetermined spacing between the cathode 30 and anode 31 of no more than 0.002 of an inch ranging down to as little as approximately 0.0002 of an inch. Housing 29 is equipped with a cap 33 holding the anode 21 in place sm:g against ~he anode side of shoulder 32, c2nd also with a cap ~4 holding a gl~ss 10 window disc 3~ in place. Glass disc 35 is held in stacked assembly with cylindrical spccer 36 and cathode 30 against the cathode side of shoulder 32 by cap 34 that is provided with an opening 37 in order that the focused beam may shine through glass disc 35 and impinge on cathode face 3a. The ca,~s 33 and 34 are so sealed in assembly with the housing 29 as by sealants (not shown), or welds as to mainta;n 15 vacuum in the space between the anode 31 and the cathode 30 and between the cathode 30 and glass disc 35. It is important that matcrials used in the housing29 of transducer 24 be of electrical nonconductive material so as not to presentan electric current shorting path between the cathode 30 and anode 31 with the external circuit path through using load 26 being the useful circuit power output 20 path.
The hansducer 24' of Figure 4 is much the same as with the embodiment of Figure 3 except that the anode 31' is extended to the exterior of the housing 29' without a cap like cap 33 at that end for cooling purposes. It is important in the embodiments with anodes 31, 31' and in other embodiments that the anodes be 25 like a heat sink so as to be much cooler at all operational time than the cathode of a transducer in order to optimize the thermionic action developed power output therefrorn. The lines connected to and through load 26 in the embodimentsof Figure, 3 and 4, must obviously be of adequate current carrying capacity and have appropriate connections with anodes and cathodes, and have appropriate 30 housing through wall provisions where passed through a housing wall to meet ~5~6~
housing vacuum requirements through a high temperature operational ranae.
With t~e transducer 24~ of Figures 5 and 6, the ~xtension of ~node 3P~ beyond an end of housing 29" is equipped with a plurality of radially extended cooling fins 39 to optimize cooling of the anode, particularly the anode face closely spaced from the cathode.
A typical cathode material usable for cathodes 38 is tungsten that has a work function of 4.52 volts and a melting temperature ~f 3653 degrees kelvin.
The anode face opposite the cathode such as -.vould be used on anode 31 or 31' anci illustrated in enlarged fragmented sectioned Figure 7 is a silver-oxide base coating 40 deposited on the anode copper heat sink conductor 41 and a top coating of cesium 42. Such an anode has a work function of .75volts. The thermionic process to change solar energy into electrical energy, in a solar system using atransducer 24 with such components, operates in the following manner: An area of solar radiation rays are concentrated into Q small area on the cathode of thetransducer. The transducer cathode material used allows electrons to escape its surface as its internal temperature is increased. These electrons are captured by the anodes which is conn~cted back by an electric current conducting circuit to the cathode.
Since electrons are lost by the cathode and acquired by the anode with this process a potential difference E exists with the cathode being positive qnd the anode nega-tive and if an electrical load is included in a circuit between the cathode and anode an electron stream of magnitude I will flow through it doing work.
The focJsed energy is directed onto one side of the cathode in a transduc~r 24 made up of the cathode, an anode, and a housing constructed to maintain a vacuum between the cathode and anode. On the basis of thermodynamic con-siderations advanced by Mr. V. Lane (1918) and Mr. R.C. Talman (1921), Mr.
5. I)ushman, derived an equation for thermionic emission as follows:
I = AT E ~ bo/T Equation I
where A = 27rmO e k /h mo = rest - mass of the electron e = charge on the electron k = ~oltzmann constant h = Pl~nck constant bo= 11~05 O
~0 = thermionic ~ork func~ion of any ,oarticular metal ~ = aL~soluta temperature, deg l~elvin ~ = emission current, amp/square centimeter If the c~thrde is heatsd up by 50kir energy, the abova equ~tion will defir~ the num~r of electrons (amounP of curren~) ~hat will leovo the eathode. Tha ~wo voriables in ~he eqwtion the clesignor has control o~ ;s the sel~ction of ~hs lyp~
of moterial that, determines the thermionic work fursctlon" and the size of ths c~thcda which influences the magnitude of currant. Other desi~n paramstor-s imposed on the cothod~ are material melt;ng temper~ture, mechanical strength at elevated temperatures, and thermal exp~nsion.
It is apparent that if the temperature is increased without limit in eqwtion 1, that the current would increase without limit. How0~r, iS is also r~ppar~nt that at some tempercture any material will melt and eguation I has no meaning.
Therefore when c cathade moterial is selected fDr current output, it must simultan-eously be selected to be within or below its melting ternperature .
Cathode to anode spacing is also important, but at this point it is only necessary to accept this and define the characteristics of the cathode that should be determined in order to accomplish it. Those characteristics cre mechanical strength at high temperatures and thermal expansion.
It has ~een shown that the cathode emits o stream of electrons from its surface at elevated temperatures. However, since the presence of even a slight ~race of residual oxygen and many other gc-ses decreases the emission tremen~ously, an efficient high current output can be obtained only from well-cleaned surfacesand in vacu~:m of the order of 10 3)1 or less.
The actual value of the "space current", QS is is often designated, between cathode and anodle, in a good vacuum, is limited either by temperature saturation, see equation 1, or by anode voltage. As shown by Langmuir (1913) the space charge ~l~g~
limi~ed current for parallel plane surfaces is I 5 2.~31 T V3/2 Equation 2 d where I = current in amp per squcire centimeter d = distance between cathode and anode in centimeters V= voltage between cathode and anode in volts In his transducer the value of V is equal to the difference in volts ge of the work function of the c~thode and the work function o~ the anode.
The distance between the cathode and anode, d ~n equa~io~ 2, is critical because by inspec~ion it can be seen thc~t space charge limited current varies 10 inversely as the square of this quantity. Herein before it has been pointed out that certain parameters should be selected for the cathode in orcler to control this distance. The same is also true for the node even though it is not as critical since it is at a much lower temperature.
The anode responcls to equation I with its intrinsic values in the same 15 manner as the cathode. However, the current from the anode will substract from the current from the cathode, and cause a decrease in output current in a pro-cess called secondary er~ission. The design of the trunsducers is such that thissecondary emission is recluced to a minimum by keeping the anods temperature as low as practical.
The primary sources of energy which can cause a rise in temperature of the anode is radiation from the cathode, energy used in overcoming work functionof the anode, and the passage of current through the anode which causesan 12R
loss. The design of the anode is such that the summation of the three energy sources can traverse the anode and be radiated to ambient tempen:lture without 2~ causing the temperature of the anode to rise appreciably.
The value of the work function of the anode should be made as low as possible through selection of correct anode facing material. This is because this work function adversely affects ths operation of the transducer in three ways:
First, since the V in equation 2 is equal to the work function of the cathode 30 minus the work function of the anode, it reduces the magnitude of the space charge ~9sg~
lirr,ited curre.~t.
Second, the usab`~e output power from the transdiJcer is equal to the voltage between the anode and cathode, `~/, times the electron current fr(~m cathode to anode. Since V is equal to the work function of the cathode minus the work function of the anode, it is apparent that the available output power is reducedby an amount equal to ànode work function times the output curr~nt.
Third, the lost of power equal to the anode work function times the output current results in a temperature rise in the anode. If dssign precautions are not exercised ta limit the amount of this temperature rise, secondary emission will occur at the anode and decrease the magnitude of current output~
Using the design constraints, equations, and methods outlired in the pre-ceding paragraphs, a tyaical unit was designed. The cathode material was se-lectod as tungsten which has a work function of 4.æ volts and a melting tempera-ture of 3653 degrees kelvin. The anode face opposite the cathr~de was made From a ;ilver-oxide base with a coating of cesium. This composite face was affixed to a copper conductor. This anods has a work function of .75 volts. Using the above numbers and equations I and 2 simultaneously, the following data was de-rived when - Cathode - anode spacing = .000247 inches cathode temperature= 3o30 degrees Keivin then - output c urrent = 335 .98 amps output power = 1219.11 watts Next the unit was designed and input power determined so lhat the cathode temperature could be reached. The cathode is 0.287 square inch in cross sectional area and at 3630 degrees Kelvin as determined by the equations. This is 23 degrees.
Centigrade below the melting point of tungsten. When at temperature equilibrium,the cathode must absorb power equal to its power losses. These Icsses are radiation J ~1 ~, ol7VZGt:1~
and conduction losses. There are no cathode,~ ~losses since the element is in a vacuum.
The first radiation loss of the cathode to be examined is to the anode. The onode is placed with a spacing o~ .000247 inch~s ~o the cathode ~nd the socond~y emission CurrPn~ is l;mited ~o 1% oF the cathode curten~. This determin~s that the face of the onode nearest the cathode must be os most 662de~re0s Kolvin, preferably less. All of the power absorbed by the tsnode comes from the cothod~
face by radiation~ This power can be akulated by using the following equqtion PRAD =~lAc oT4 ~2AAaT2 Equation 3 where PRAD = Power exchanged cathode-anode (wat~i) ~ = Emissivity of athode = .3784 A = Cathode face area (square inchl s); I sq. in.
~ = Stefon's constant = 37.57~54 X 10 12/inch K
T = Cathode temperature = 3200 de~. Kelvin 2 = Emissivity of anod~ = .78 A = Anode foce areo (s~uare inches) T = ,~node ternperature = 71~ degrees Kelvin This power is calculat~d to be 133û.1 watts and it is conducted thru tne cnode and dissipated to th~ ambient surroundinas by convection and conduction.
The onode conduction coefficient, determined by the kind of material used, is ~9.81 watts/inch/deg Kelvin. it is calculated that the anode mus~ be 1.69 inches 20 in dicmeter and 6.75 inches long in order to reach temperature equilibrium with the input face at 715 deg. Kelvin and a wattage input of 1330.1 watts. With these d;mensions the temperoture at the OUtp~lt face of the anode is 679 deg. Kelvin.
The electrical efficiency is defined as the av~ilable power 2~ from the cothode s~nd equal to the output current times the cathode work function, minus the power loss in the anode in overcoming its work function, equal to output current times the anode work function, divided by the available power. This calculates to be 77.4%. Therefore the operating characteristics of the anode and the rodiation losses of one face ot the cathode have been determined.
~3 ~
~1;995~
Another power loss by the _athode is hy conduction. The cathode is .05 inches thick cnd has a conduction coeFficient of 16.55 watts/inc;h,/deg. Kelvin.The sides of the cathode lose power by radiation to the ambient environment. Using this data it is found that the temperative of tke input face, the cathode face away from the anode, is 3204 degrees Kelvin and the amount of radiation input power necessary to take care of all losses to this point is 1596.8 watts. There are other losses at the cathode input face discussed hereinafter. However, it is convenient at this point, to describe some characteristics of the transducer since at some point in time it might be desireabl~ to compare different transducers.
This transducer has an available elect:ic poweroutput from the cathodec~t a high voltage level resulting from a moderately higher wattage o~ radiated power input taking into account the losses described above. With such a transducer the output voltage, cathode only not including anode, is 4.æ volts and the rneasured output voltage, both cathode and anode, is 3.5 volts. The output çurrent is 393.9 amp~s and the available power from the cathode is 1780.4 watts and the power loss overcoming the anode work functic~n is 401.8 ~Natts with a usable output power of 1378.6 watts. The electrical watts generated at the cathode per degree Kel~in is.55O and a high efficiency is attained on the conversion of radiation input power to cathode electrical power at this point.
The only other power loss t!y the cathcde is at its input face and some methods may be implemented to reducethe magnitude of this loss. The cathode is contained by the housing in a vccuum.
The anode~cathode spacin~ in the thermionic solar to electric power transducers is a critical factor in a~hieving high efficiency through optimization, in the ~hermionic clevice, of two conditions as defined by two equations.
The first equation is for thermionic current limitation duç to temperature saturation and is shown in equation IA:
AMP
T 11 ~05V ~ Equation I A
3û T `
where AMPT= Output Current (Amps/in ) 2 lr M ek A = h r = 2 .71 8281 828459 T = Temperature (degrees Kelvin) Vw= work function of material (volts~
In the equation for A
M = rest - mass of el~ctron = charge on the electr~n k = Boltzmann constant h = quantum constant (Planck's constant) The second equation is fcr current li~niation due to space charge an~l is sh3wn in equation 2A:
AMP = 15 .03~o8 X10 (V ) 3/?
where AMPs= Output current (Amps/in2) 15.03868 = constant for parallel plane surfaces d = distance between electrodes (inches) VD = voltage difference between electrode~ (volts) When these two equations are solved simultaneously, it is found that d can vary from 25 X 10 6 inches to 50~ X 10 6 inches for typical values of volta~e di~ference and work function voltage.
This requirement for smal7 distances and the tolerances associated with those distances create the following problems:
(I) How to set, maintain, and control tolerances on the small distarces.
2~ (2) If spclcers are used, haw to insulate electrically between the electrodes.
mirror or lens focused beams of energy to a high energy elevated temperature spot on the c~thode of the transducer used in a thermior~ic conversion of solar energy toelectricity. The process is very reliable with no movin~ parts in the solar energy transducer cnd with no pro~:esses inherentl~ unstable ond self~
5 destructive, such as thermal runaway in a transistor. The solar ra~iation driven process is a clean approach making use of the in'!7erent properSies of materials, relatively easy to control, and with iife of components used in the thermioniG process extremely long. The transducer i5 made up of the catt`lode, an anode, and a housing such as to permit a v~cuum to exist lO between the cathode and anode with cathode materials ;elected for advan-tageous work functions and high temperature capabiliti0s. A typical cathode material is tungsten with a work function of 4.52 volts and a melting tempera-ture of ~53 degrees kelvin and an anode face opposite the cathode may be, for example, a silver-oxide base with a coating of .ç~siumwith this composite 15 anode face af,ixed to a copper heat sink conductor. This ,~rovides an anode face work function of .75 valts. With the transducer the value of voltage of the work function of the cathode and the work function of the anode.
Specific embodiments representing what are presently regarded as the best mode of cr~rrying out the invention are illus~;r~ited in the accompanying 20 drawings:
In the drawings:
Figure I represents a side elevation semi schema~ic showing of a solar to electrical power thermionic cor~v~rsion system using a polar axis mounted reflective mirror solar radiation concentrator and transducer supplying electrical 25 pow~r to a load;
Figure 2, a similar system using a lens in place of the mirror as a sola- radiation concentrator;
Figures 3 and 4, cut away and sectioned showin~3s of alternate traniducer embodiments useable in the solar systems of F; gures I and 2 circuit 30 connected to using loads;
Figures 5 and o, end and slde views of yet another transducer embodiment with cooling fins projecting from tihe anode;
Figure 7, a partial cut awuy and sectioned vi~sw of a section of the cathode facing end of an anode useable in the transducer embodiments of Figures 3,4,5 ond 6;
Figures 8,9, and 10, side elevation cut away section, a sectioned view on line 9-9, and the anode connector end view of another transducer;
Figure 11~ a schematic showing of a solar to ~ tric power system with the load in the form of a light;
Figures 12 and 13, alt~rnut~ air conditioning systems driven by solar ther-mionic conversion systems backed up by a convention~l power supply system;
Figure 14, a solar thermionic system driving an electric pump;
Figure 15, a solar thermionic system powering a florescent lamp;
Figure 16, a solar thermionic powered electrical radiant heating system; and, Figure 17, a solar thermionic powered electrical heater to boiler hot water heating system .
Referring to the drawings:
The polar axis mcunt structure 20 for a solar syst~sm 21 of Figure I, mounts a reflective dish 22 focusing solar radiation to a concer~trated beam area impinging on the cathode end 23 of transducer 24. The support structure 20 is equipped to track the sun during daylight hours through appropriate articulatiorl drive and control structure of a conventional nature (detail not shown) so as to keep the focused spot from migration out of the desired transducer 24 cathode opera~ional area limits.
Transducer 24 is mounted in proper focal position by mounting arm; 25 attached to the rim of mirror dish 22, and is shown, schematically, to be elec,rically connected to a load 26.
The embodiment of Figure 2, is much the same as that of F~gure 1, with however, a lens 27 mounted in rim 28 used in place of the mirror clish 22. Sincethe balance of the solar system 21 is substantially the same as with the embodiment of Figure I the identification numb,srs are the same as well as the respective functions thereof.
~L~9~
The transducer 24 of Figure 3, such as may be ~nounted in the soi~r sy~tem of Figure I or Figure ~ is shown to include a housing ~) enclo~ing a cathode 30 und an ~node 31 In an evacuated environment with the catkode 30 qnd the anode 31 electricnlly connected to a using load 20. Housing 25 is generally cylindrical 5 wi,h an innel annular shoulder 32 acting as a spacer fcr the cathode 30 and anode 31 to insure close predetermined spacing between the cathode 30 and anode 31 of no more than 0.002 of an inch ranging down to as little as approximately 0.0002 of an inch. Housing 29 is equipped with a cap 33 holding the anode 21 in place sm:g against ~he anode side of shoulder 32, c2nd also with a cap ~4 holding a gl~ss 10 window disc 3~ in place. Glass disc 35 is held in stacked assembly with cylindrical spccer 36 and cathode 30 against the cathode side of shoulder 32 by cap 34 that is provided with an opening 37 in order that the focused beam may shine through glass disc 35 and impinge on cathode face 3a. The ca,~s 33 and 34 are so sealed in assembly with the housing 29 as by sealants (not shown), or welds as to mainta;n 15 vacuum in the space between the anode 31 and the cathode 30 and between the cathode 30 and glass disc 35. It is important that matcrials used in the housing29 of transducer 24 be of electrical nonconductive material so as not to presentan electric current shorting path between the cathode 30 and anode 31 with the external circuit path through using load 26 being the useful circuit power output 20 path.
The hansducer 24' of Figure 4 is much the same as with the embodiment of Figure 3 except that the anode 31' is extended to the exterior of the housing 29' without a cap like cap 33 at that end for cooling purposes. It is important in the embodiments with anodes 31, 31' and in other embodiments that the anodes be 25 like a heat sink so as to be much cooler at all operational time than the cathode of a transducer in order to optimize the thermionic action developed power output therefrorn. The lines connected to and through load 26 in the embodimentsof Figure, 3 and 4, must obviously be of adequate current carrying capacity and have appropriate connections with anodes and cathodes, and have appropriate 30 housing through wall provisions where passed through a housing wall to meet ~5~6~
housing vacuum requirements through a high temperature operational ranae.
With t~e transducer 24~ of Figures 5 and 6, the ~xtension of ~node 3P~ beyond an end of housing 29" is equipped with a plurality of radially extended cooling fins 39 to optimize cooling of the anode, particularly the anode face closely spaced from the cathode.
A typical cathode material usable for cathodes 38 is tungsten that has a work function of 4.52 volts and a melting temperature ~f 3653 degrees kelvin.
The anode face opposite the cathode such as -.vould be used on anode 31 or 31' anci illustrated in enlarged fragmented sectioned Figure 7 is a silver-oxide base coating 40 deposited on the anode copper heat sink conductor 41 and a top coating of cesium 42. Such an anode has a work function of .75volts. The thermionic process to change solar energy into electrical energy, in a solar system using atransducer 24 with such components, operates in the following manner: An area of solar radiation rays are concentrated into Q small area on the cathode of thetransducer. The transducer cathode material used allows electrons to escape its surface as its internal temperature is increased. These electrons are captured by the anodes which is conn~cted back by an electric current conducting circuit to the cathode.
Since electrons are lost by the cathode and acquired by the anode with this process a potential difference E exists with the cathode being positive qnd the anode nega-tive and if an electrical load is included in a circuit between the cathode and anode an electron stream of magnitude I will flow through it doing work.
The focJsed energy is directed onto one side of the cathode in a transduc~r 24 made up of the cathode, an anode, and a housing constructed to maintain a vacuum between the cathode and anode. On the basis of thermodynamic con-siderations advanced by Mr. V. Lane (1918) and Mr. R.C. Talman (1921), Mr.
5. I)ushman, derived an equation for thermionic emission as follows:
I = AT E ~ bo/T Equation I
where A = 27rmO e k /h mo = rest - mass of the electron e = charge on the electron k = ~oltzmann constant h = Pl~nck constant bo= 11~05 O
~0 = thermionic ~ork func~ion of any ,oarticular metal ~ = aL~soluta temperature, deg l~elvin ~ = emission current, amp/square centimeter If the c~thrde is heatsd up by 50kir energy, the abova equ~tion will defir~ the num~r of electrons (amounP of curren~) ~hat will leovo the eathode. Tha ~wo voriables in ~he eqwtion the clesignor has control o~ ;s the sel~ction of ~hs lyp~
of moterial that, determines the thermionic work fursctlon" and the size of ths c~thcda which influences the magnitude of currant. Other desi~n paramstor-s imposed on the cothod~ are material melt;ng temper~ture, mechanical strength at elevated temperatures, and thermal exp~nsion.
It is apparent that if the temperature is increased without limit in eqwtion 1, that the current would increase without limit. How0~r, iS is also r~ppar~nt that at some tempercture any material will melt and eguation I has no meaning.
Therefore when c cathade moterial is selected fDr current output, it must simultan-eously be selected to be within or below its melting ternperature .
Cathode to anode spacing is also important, but at this point it is only necessary to accept this and define the characteristics of the cathode that should be determined in order to accomplish it. Those characteristics cre mechanical strength at high temperatures and thermal expansion.
It has ~een shown that the cathode emits o stream of electrons from its surface at elevated temperatures. However, since the presence of even a slight ~race of residual oxygen and many other gc-ses decreases the emission tremen~ously, an efficient high current output can be obtained only from well-cleaned surfacesand in vacu~:m of the order of 10 3)1 or less.
The actual value of the "space current", QS is is often designated, between cathode and anodle, in a good vacuum, is limited either by temperature saturation, see equation 1, or by anode voltage. As shown by Langmuir (1913) the space charge ~l~g~
limi~ed current for parallel plane surfaces is I 5 2.~31 T V3/2 Equation 2 d where I = current in amp per squcire centimeter d = distance between cathode and anode in centimeters V= voltage between cathode and anode in volts In his transducer the value of V is equal to the difference in volts ge of the work function of the c~thode and the work function o~ the anode.
The distance between the cathode and anode, d ~n equa~io~ 2, is critical because by inspec~ion it can be seen thc~t space charge limited current varies 10 inversely as the square of this quantity. Herein before it has been pointed out that certain parameters should be selected for the cathode in orcler to control this distance. The same is also true for the node even though it is not as critical since it is at a much lower temperature.
The anode responcls to equation I with its intrinsic values in the same 15 manner as the cathode. However, the current from the anode will substract from the current from the cathode, and cause a decrease in output current in a pro-cess called secondary er~ission. The design of the trunsducers is such that thissecondary emission is recluced to a minimum by keeping the anods temperature as low as practical.
The primary sources of energy which can cause a rise in temperature of the anode is radiation from the cathode, energy used in overcoming work functionof the anode, and the passage of current through the anode which causesan 12R
loss. The design of the anode is such that the summation of the three energy sources can traverse the anode and be radiated to ambient tempen:lture without 2~ causing the temperature of the anode to rise appreciably.
The value of the work function of the anode should be made as low as possible through selection of correct anode facing material. This is because this work function adversely affects ths operation of the transducer in three ways:
First, since the V in equation 2 is equal to the work function of the cathode 30 minus the work function of the anode, it reduces the magnitude of the space charge ~9sg~
lirr,ited curre.~t.
Second, the usab`~e output power from the transdiJcer is equal to the voltage between the anode and cathode, `~/, times the electron current fr(~m cathode to anode. Since V is equal to the work function of the cathode minus the work function of the anode, it is apparent that the available output power is reducedby an amount equal to ànode work function times the output curr~nt.
Third, the lost of power equal to the anode work function times the output current results in a temperature rise in the anode. If dssign precautions are not exercised ta limit the amount of this temperature rise, secondary emission will occur at the anode and decrease the magnitude of current output~
Using the design constraints, equations, and methods outlired in the pre-ceding paragraphs, a tyaical unit was designed. The cathode material was se-lectod as tungsten which has a work function of 4.æ volts and a melting tempera-ture of 3653 degrees kelvin. The anode face opposite the cathr~de was made From a ;ilver-oxide base with a coating of cesium. This composite face was affixed to a copper conductor. This anods has a work function of .75 volts. Using the above numbers and equations I and 2 simultaneously, the following data was de-rived when - Cathode - anode spacing = .000247 inches cathode temperature= 3o30 degrees Keivin then - output c urrent = 335 .98 amps output power = 1219.11 watts Next the unit was designed and input power determined so lhat the cathode temperature could be reached. The cathode is 0.287 square inch in cross sectional area and at 3630 degrees Kelvin as determined by the equations. This is 23 degrees.
Centigrade below the melting point of tungsten. When at temperature equilibrium,the cathode must absorb power equal to its power losses. These Icsses are radiation J ~1 ~, ol7VZGt:1~
and conduction losses. There are no cathode,~ ~losses since the element is in a vacuum.
The first radiation loss of the cathode to be examined is to the anode. The onode is placed with a spacing o~ .000247 inch~s ~o the cathode ~nd the socond~y emission CurrPn~ is l;mited ~o 1% oF the cathode curten~. This determin~s that the face of the onode nearest the cathode must be os most 662de~re0s Kolvin, preferably less. All of the power absorbed by the tsnode comes from the cothod~
face by radiation~ This power can be akulated by using the following equqtion PRAD =~lAc oT4 ~2AAaT2 Equation 3 where PRAD = Power exchanged cathode-anode (wat~i) ~ = Emissivity of athode = .3784 A = Cathode face area (square inchl s); I sq. in.
~ = Stefon's constant = 37.57~54 X 10 12/inch K
T = Cathode temperature = 3200 de~. Kelvin 2 = Emissivity of anod~ = .78 A = Anode foce areo (s~uare inches) T = ,~node ternperature = 71~ degrees Kelvin This power is calculat~d to be 133û.1 watts and it is conducted thru tne cnode and dissipated to th~ ambient surroundinas by convection and conduction.
The onode conduction coefficient, determined by the kind of material used, is ~9.81 watts/inch/deg Kelvin. it is calculated that the anode mus~ be 1.69 inches 20 in dicmeter and 6.75 inches long in order to reach temperature equilibrium with the input face at 715 deg. Kelvin and a wattage input of 1330.1 watts. With these d;mensions the temperoture at the OUtp~lt face of the anode is 679 deg. Kelvin.
The electrical efficiency is defined as the av~ilable power 2~ from the cothode s~nd equal to the output current times the cathode work function, minus the power loss in the anode in overcoming its work function, equal to output current times the anode work function, divided by the available power. This calculates to be 77.4%. Therefore the operating characteristics of the anode and the rodiation losses of one face ot the cathode have been determined.
~3 ~
~1;995~
Another power loss by the _athode is hy conduction. The cathode is .05 inches thick cnd has a conduction coeFficient of 16.55 watts/inc;h,/deg. Kelvin.The sides of the cathode lose power by radiation to the ambient environment. Using this data it is found that the temperative of tke input face, the cathode face away from the anode, is 3204 degrees Kelvin and the amount of radiation input power necessary to take care of all losses to this point is 1596.8 watts. There are other losses at the cathode input face discussed hereinafter. However, it is convenient at this point, to describe some characteristics of the transducer since at some point in time it might be desireabl~ to compare different transducers.
This transducer has an available elect:ic poweroutput from the cathodec~t a high voltage level resulting from a moderately higher wattage o~ radiated power input taking into account the losses described above. With such a transducer the output voltage, cathode only not including anode, is 4.æ volts and the rneasured output voltage, both cathode and anode, is 3.5 volts. The output çurrent is 393.9 amp~s and the available power from the cathode is 1780.4 watts and the power loss overcoming the anode work functic~n is 401.8 ~Natts with a usable output power of 1378.6 watts. The electrical watts generated at the cathode per degree Kel~in is.55O and a high efficiency is attained on the conversion of radiation input power to cathode electrical power at this point.
The only other power loss t!y the cathcde is at its input face and some methods may be implemented to reducethe magnitude of this loss. The cathode is contained by the housing in a vccuum.
The anode~cathode spacin~ in the thermionic solar to electric power transducers is a critical factor in a~hieving high efficiency through optimization, in the ~hermionic clevice, of two conditions as defined by two equations.
The first equation is for thermionic current limitation duç to temperature saturation and is shown in equation IA:
AMP
T 11 ~05V ~ Equation I A
3û T `
where AMPT= Output Current (Amps/in ) 2 lr M ek A = h r = 2 .71 8281 828459 T = Temperature (degrees Kelvin) Vw= work function of material (volts~
In the equation for A
M = rest - mass of el~ctron = charge on the electr~n k = Boltzmann constant h = quantum constant (Planck's constant) The second equation is fcr current li~niation due to space charge an~l is sh3wn in equation 2A:
AMP = 15 .03~o8 X10 (V ) 3/?
where AMPs= Output current (Amps/in2) 15.03868 = constant for parallel plane surfaces d = distance between electrodes (inches) VD = voltage difference between electrode~ (volts) When these two equations are solved simultaneously, it is found that d can vary from 25 X 10 6 inches to 50~ X 10 6 inches for typical values of volta~e di~ference and work function voltage.
This requirement for smal7 distances and the tolerances associated with those distances create the following problems:
(I) How to set, maintain, and control tolerances on the small distarces.
2~ (2) If spclcers are used, haw to insulate electrically between the electrodes.
(3) If spacers are used, how to ~ainimize the power loss due to thermal conduction .
A solution to these problems is embodied in a process and materials.
First of all, spucers are used. The material for these spacers can be ~9~
olvrninum oxide or Hafnium oxide depending upon the opar~ting ~emperaturo.
Aluminum oxid~ can b~ used up to 2~07 degrees Kelvin and Hafnium oxide ~an be used up to 3050 de~arees Kelvih.
The space materiol is deposited ~pon the surface of eith~r th0 c~thods or 5 the anode. This is done by using phoh9raphic masks nnd vacuum d~position processes. Usin~ this process tolerances on thickn~ss ean b~ held to 20 to ~0 onsitroms, well within the tolerance requirorr~nt. This dopositod sp~cg~r c~n ~
used to sotisfy the si5~nificant problem of se~ttin~3, rn~intainin~, the ~istonee b~h~oan elec~rades ~nd controlllng the toleranca on that dishnce.
1~ Either Hafnium oxide or ~.luminum oxido will ati$factorily eiectricclly insulate the two eiectrodes at the hi~h terr~orature required.
The power loss is minimized by controlling the width of the spacer. Power by therrr~ol conduction is given by equation 3A shown below:
P = A ,~ ~T
where P = Power conducted (Wntts) = Thermal conduction Coeff;cient A= Cross sectionl area ~T = Temperature difference ( K) QL = change in length 20 As can be seen by inspection of the above equ~tion, the only variable for a given set of conditions is cross sectional area, A. Thts cross sectional area is equl to the spacing between electrodes, which is s~t as descri~ed above, times the width of the spacer. Therefore, during the deposition of the spacer, if the wid-h is controlled, the power loss will be controlled. It can be shown that 300 X 10 2~ inches or less for width of the spacer will limit the !s~ of pGwer by thermal conduction to less than .1% of the electrical power output by th~ thermionic processO
The showing of the transducer 43 of Figure ô,~ and 10, is more detailed than other transducer 24 embodiments with an anode 44, having heat radiation fins 45 30 to ths exterior of vacuum housing 46. The anode 44 structure includes, typically ~, -14-:~9S~
a silver-oxide substrate coating on a copper heat sink body with an overcoating C~5 ill~
of c~;um, such as ths layered conting shown in Figure 7, to yield a relatively low work function approximately .75 volts at the anode race 47. The copper heat sink body of anode 44 is inches long with housing ciosing wali 48 that is sealed in 5 place closinv an cnd of housing 46 as ~y weldin_ (detail not shown~ and extends back through t~e heat fin 45 area to the anode current buss 49 connection at theend as by scre~ assembly 50. The other end of housing ~;6 is closed by a glass 51, or other media highly transparent to the desired solar radiation energy, held insealing pressure contact with the inside of housing flang~ 52. An alternate sealing 10 Of the glass 51 to the inside of housing flange 52 could be with a ceramic sealant (detail not shown) in order that a vacuum may t~e maintained within the housing 46 that is evacuated through evacuation tube 53. The cathode 54 contained within the evacuated chamber of housing 46 is a relatively thin body of high melt temperature high work function material such as tungsten approximately .04 inches thick with a 15 oenter disc portion approximately 1/2 inch in diameter. Four radially extended current carrying mounting arms 56 extend outwardly from the center disc 55 to mounting stud cnd bolt assemblies 57 that with spacers 5~ mount the cathode 54 at about .16 inches behind the glass disc 51. The stud and bolt assemblies 57 extend through openings 59 in the glass disc 51 to mount a currer~t collector ring 60 to the 2û exterior of housing 46. A center opening 61 is provided ?n the current ring 60 for unimpeded passage of focused radiant energy tc the glass disc 51 and primarily through the glass to impingement c,n the radiant energy input side of the cathode 54. The current ring 60 with a current buss 62 stud and ,~olt assemblies 57, glass disc 51, and cathode 54 are so assembled as to be eleGtricalry insulat0d from direct shorting25 electrical contact with conductive material of llousing 46 and from anode 44.In order to focilitate desired closespacing between the cathode 54 and the face of anode 44 Hafnium oxidc (or Alumin~lmoxide) spacer strips 63 are deposited on the anode side of the cathode 54 starting just outside the higher heat ~one of the cathode center disc portion 55. Tl-e spacer strips 63 thclt are typically .0003 inches wide and 3û .00024 thick extend radially outwardly and are so spaced as to substantially eliminate ~s~
chance of shorting contac.t between cathode and anode. Further, spacer strips b3 extending raclially outward on cathode arms 56 cJre shown to be provicled with arm width widened outer end pads 6~ to additionally insure non-shorting between cathode and anode.
Use of fused silica UV glass, or the substantial equivalent there~f, for housingglass disc 51 is quite effective in helping to reduce radiation losses at the cathode input face.
With a transducer constructed w`th the cathode inside; a housing maintaining c~ high vacuum solc~r rad;cltion is co~centrated ;nto a beam and d;recte~l thru the housing onto the cathode. The energy in the b~am generally has a poedeterrnined distribution with solar w~ve directed onto the cathode ~ (min) _ .0, microns, A(max)~- 3.59 m;crons, an!~ ~ m where max;mum intensity oF radiation occurs is approximately .5 microns. If fuseo silica UV glass, or equivalent, is used as the housing material this band of frequencies will be passed thru with only a 5% to 10% reduction~ This transmitted wave heats the cathode up to a temperature of 2400 Kelvin to 3600 Kelvin. Ex~ct temperature depends upon the cathode material and the thermionic current requirements. The hot cathode will in turn radiate energy following the same waveform distribution. However, now a shift has occurred in the frequ~ncy spectrum with ~ (min) is approximc~tely .25 microns, ~ Imax) is over 6 microns, and ~m is approximately I micron. The fused Silica-uvhousing absorbed a large ~art of this band of radiation. Whereas, when the solarwave passed through the 'lousing - 90% to 95% was transmitted through the housing, approximately 4% was reFlected, and the remaining 1% to 6% absorbed; now with the radiated cathode heat wave-approximately 56% is transmitted Ihrough, 4% is reflected, and 4t)% absorbed. This absorbed energy will raise the temperature ofthe housing. By design the temperature to which the housing is rai,ed can be controlled in the following manner. The losses from the housing ar~ basically radiation and convection losses. They will follow the conventional equations forthes~ losses. Equation A for Radiation and Equation B for Conver tion:
Pr = A~H a ~TH ~ TA ) Equation A
S~
where Pr = Power radiated A= Area of radiation H = Emissivity oF Housing ~s =Constant TH = Temperature of Housing TA = Ambient Temperature PCv =Y A (TH- TA) Equation B
where lQ Pcv = Po~.verof con~ection 'f = constant A = Area TH = Temperature of Housing TA = Ambient Temperature 15 When the sum of these two losses equals the power exch~nge from the cathode to housing, temperature equilibrium is obtained. Also, the power exchange from cathode to hol~Jsing is the only radiated power loss from the cathode input face.
Therefore, as iaid in the initial paragraph, this loss should be minimized.
The equation for power radiated from the cathode is ;hown in Equation C:
2Q P = ~ c ;~Tc Equation C
where P = power radiated from cathode to housing A = Area c = Emissivity of cathode a = constant Tc = Temperature of cathode The energy radiated back from housing to c.athode is given by Equation D:
~s~
P 3 = A~: H ~TH Equation r~
where PH = power radiated from housin~: to cathode A = Area EH = Emissivity of Housing cr= constant TH = Temperature of Housing The energy exchanged from cathode to housi,~g is obtained by substracting equation D from Equation C. The results are 3iven in EqJation E:
1~ EXC A~(c Tc -E~iTH4) Equation E
Inspection of the equation shows that the terms E T 4 and ~ ~iTH4 are the dominating terms because of the fourth power. Also, inspection reveals the closer TH iS to Tc,the smaller the power exchange. Therefore the design is performed to raise the temperature of the housing, as pointed out on pa3e 3. This design makes use of the thermal con-1~ duction equation (Equation F).
P = A ~ ~ T Equation F
cond cr ~ L
where P = Power of conduction cond ~ = Thermal Conduction Coefficient ~ T = change in te mperat ure L = change in length ACr = cross sectional area By selection of the right housing materiai, solar energy is passed through and heat radiated energy is absorbed. This absorbed power is the PCond in Equation F, the higherAT is for a given configuratiorl,~nd the, r vqlue is given by Equation G:
~T =TH ~ TA Equation G
Therefore TA or ambient temperature is a reference point, as ~ T increases the housing temperature TH will increase and as TH increases the power exchanged cathode to Housing will decrease.
Another independent variable in the equation is ACr or the cross-sectional area.
This is not to be c.onfused with Area. Area is the face ~rea of the device and cross-sectional area is the are~ of material in the housi~g and is given by Equation J:
A 1`(21rR) Equation J
where A = cross sectional area cr r= Thicknoss of houstng ~ = Radius at which thermal conduction calculation is needed.
Therefore by reducing the thickness of the housing the housing temperature can also be controlled.
~eduction of this process to practice, give, a housin3 material of Fused Silica- W
glass made by Corning Glass and a thickness ~f .394 ir~ches.other vari~tions have the fused silica welded to other types of glasses with different thicknesses. This combination will allow the housing temperature to be controlled so that the power radiated is minimized. In fact, in the future~ if a material can be found for the housing which has the above characteristics and a melting temperature equal to or gre~ter than t3~e cathode temperature, this power loss can be reduced to a valueapproaching ~ero.
With the solar to electric power system of Figure 11, the thermionic transducer 24 is sopplying power through a line system with switch 65 to a lamp 66.
2û The solar to electric pcwer system of Figure 12 has a transducer 24 connected in paral lel with an AC power supply 67, connected through an AC to DC convertor68 ond isolatcr 6, to supply power through a temperature control 70 employing atemperature sensor 71 for control of power to (lir conditioning unit 72.
'Nith the alternate air conditioning system of Figure 13, the DC power output of transducer 24 is converted to AC via convertor 73 and passed to a switch 74 controlled by a detector 75 for switching between the transducer supply power and power from alternate AC power source 76. These insure po~er supply through temperature control 70' as controlled bytemp~ rature sensor 71' for control of power to air conditioning unit`72'.
3û The transducer 24 in Figure 14 is the power source for an electric pump ;77.
--1~-- " .
5i9~i~
In Figure 15, transducer 24 is feeding DC to a DC to AC conve~tor 78 supplying AC :o a switch 79 controiled power line sysh~m ~o a fluorescent lamp 80. The tran~ducer 24 in the figure 16 system supplies DC through an on and off control 81~
controlled by a temperature sensor r32~ for an electric element 83 heater 84. Then with the system of Figure 17, a heating elemer.t 85 in boiler 86, Gnd when needed auxillary oil or gas heater 87, heati water in the boiler for distribution through heatin,a, system pipes 89 and 89 ~o and from a radiator 90 (or radiators) in an appropriate system.
Whereas, th;s invention is herein illustrated and described with respect to several embodiments thereof~ it should be rea'.ized that various chan~a,es may !~e made without depart;ng from essential contributions to the art made by the teachings hereof .
A solution to these problems is embodied in a process and materials.
First of all, spucers are used. The material for these spacers can be ~9~
olvrninum oxide or Hafnium oxide depending upon the opar~ting ~emperaturo.
Aluminum oxid~ can b~ used up to 2~07 degrees Kelvin and Hafnium oxide ~an be used up to 3050 de~arees Kelvih.
The space materiol is deposited ~pon the surface of eith~r th0 c~thods or 5 the anode. This is done by using phoh9raphic masks nnd vacuum d~position processes. Usin~ this process tolerances on thickn~ss ean b~ held to 20 to ~0 onsitroms, well within the tolerance requirorr~nt. This dopositod sp~cg~r c~n ~
used to sotisfy the si5~nificant problem of se~ttin~3, rn~intainin~, the ~istonee b~h~oan elec~rades ~nd controlllng the toleranca on that dishnce.
1~ Either Hafnium oxide or ~.luminum oxido will ati$factorily eiectricclly insulate the two eiectrodes at the hi~h terr~orature required.
The power loss is minimized by controlling the width of the spacer. Power by therrr~ol conduction is given by equation 3A shown below:
P = A ,~ ~T
where P = Power conducted (Wntts) = Thermal conduction Coeff;cient A= Cross sectionl area ~T = Temperature difference ( K) QL = change in length 20 As can be seen by inspection of the above equ~tion, the only variable for a given set of conditions is cross sectional area, A. Thts cross sectional area is equl to the spacing between electrodes, which is s~t as descri~ed above, times the width of the spacer. Therefore, during the deposition of the spacer, if the wid-h is controlled, the power loss will be controlled. It can be shown that 300 X 10 2~ inches or less for width of the spacer will limit the !s~ of pGwer by thermal conduction to less than .1% of the electrical power output by th~ thermionic processO
The showing of the transducer 43 of Figure ô,~ and 10, is more detailed than other transducer 24 embodiments with an anode 44, having heat radiation fins 45 30 to ths exterior of vacuum housing 46. The anode 44 structure includes, typically ~, -14-:~9S~
a silver-oxide substrate coating on a copper heat sink body with an overcoating C~5 ill~
of c~;um, such as ths layered conting shown in Figure 7, to yield a relatively low work function approximately .75 volts at the anode race 47. The copper heat sink body of anode 44 is inches long with housing ciosing wali 48 that is sealed in 5 place closinv an cnd of housing 46 as ~y weldin_ (detail not shown~ and extends back through t~e heat fin 45 area to the anode current buss 49 connection at theend as by scre~ assembly 50. The other end of housing ~;6 is closed by a glass 51, or other media highly transparent to the desired solar radiation energy, held insealing pressure contact with the inside of housing flang~ 52. An alternate sealing 10 Of the glass 51 to the inside of housing flange 52 could be with a ceramic sealant (detail not shown) in order that a vacuum may t~e maintained within the housing 46 that is evacuated through evacuation tube 53. The cathode 54 contained within the evacuated chamber of housing 46 is a relatively thin body of high melt temperature high work function material such as tungsten approximately .04 inches thick with a 15 oenter disc portion approximately 1/2 inch in diameter. Four radially extended current carrying mounting arms 56 extend outwardly from the center disc 55 to mounting stud cnd bolt assemblies 57 that with spacers 5~ mount the cathode 54 at about .16 inches behind the glass disc 51. The stud and bolt assemblies 57 extend through openings 59 in the glass disc 51 to mount a currer~t collector ring 60 to the 2û exterior of housing 46. A center opening 61 is provided ?n the current ring 60 for unimpeded passage of focused radiant energy tc the glass disc 51 and primarily through the glass to impingement c,n the radiant energy input side of the cathode 54. The current ring 60 with a current buss 62 stud and ,~olt assemblies 57, glass disc 51, and cathode 54 are so assembled as to be eleGtricalry insulat0d from direct shorting25 electrical contact with conductive material of llousing 46 and from anode 44.In order to focilitate desired closespacing between the cathode 54 and the face of anode 44 Hafnium oxidc (or Alumin~lmoxide) spacer strips 63 are deposited on the anode side of the cathode 54 starting just outside the higher heat ~one of the cathode center disc portion 55. Tl-e spacer strips 63 thclt are typically .0003 inches wide and 3û .00024 thick extend radially outwardly and are so spaced as to substantially eliminate ~s~
chance of shorting contac.t between cathode and anode. Further, spacer strips b3 extending raclially outward on cathode arms 56 cJre shown to be provicled with arm width widened outer end pads 6~ to additionally insure non-shorting between cathode and anode.
Use of fused silica UV glass, or the substantial equivalent there~f, for housingglass disc 51 is quite effective in helping to reduce radiation losses at the cathode input face.
With a transducer constructed w`th the cathode inside; a housing maintaining c~ high vacuum solc~r rad;cltion is co~centrated ;nto a beam and d;recte~l thru the housing onto the cathode. The energy in the b~am generally has a poedeterrnined distribution with solar w~ve directed onto the cathode ~ (min) _ .0, microns, A(max)~- 3.59 m;crons, an!~ ~ m where max;mum intensity oF radiation occurs is approximately .5 microns. If fuseo silica UV glass, or equivalent, is used as the housing material this band of frequencies will be passed thru with only a 5% to 10% reduction~ This transmitted wave heats the cathode up to a temperature of 2400 Kelvin to 3600 Kelvin. Ex~ct temperature depends upon the cathode material and the thermionic current requirements. The hot cathode will in turn radiate energy following the same waveform distribution. However, now a shift has occurred in the frequ~ncy spectrum with ~ (min) is approximc~tely .25 microns, ~ Imax) is over 6 microns, and ~m is approximately I micron. The fused Silica-uvhousing absorbed a large ~art of this band of radiation. Whereas, when the solarwave passed through the 'lousing - 90% to 95% was transmitted through the housing, approximately 4% was reFlected, and the remaining 1% to 6% absorbed; now with the radiated cathode heat wave-approximately 56% is transmitted Ihrough, 4% is reflected, and 4t)% absorbed. This absorbed energy will raise the temperature ofthe housing. By design the temperature to which the housing is rai,ed can be controlled in the following manner. The losses from the housing ar~ basically radiation and convection losses. They will follow the conventional equations forthes~ losses. Equation A for Radiation and Equation B for Conver tion:
Pr = A~H a ~TH ~ TA ) Equation A
S~
where Pr = Power radiated A= Area of radiation H = Emissivity oF Housing ~s =Constant TH = Temperature of Housing TA = Ambient Temperature PCv =Y A (TH- TA) Equation B
where lQ Pcv = Po~.verof con~ection 'f = constant A = Area TH = Temperature of Housing TA = Ambient Temperature 15 When the sum of these two losses equals the power exch~nge from the cathode to housing, temperature equilibrium is obtained. Also, the power exchange from cathode to hol~Jsing is the only radiated power loss from the cathode input face.
Therefore, as iaid in the initial paragraph, this loss should be minimized.
The equation for power radiated from the cathode is ;hown in Equation C:
2Q P = ~ c ;~Tc Equation C
where P = power radiated from cathode to housing A = Area c = Emissivity of cathode a = constant Tc = Temperature of cathode The energy radiated back from housing to c.athode is given by Equation D:
~s~
P 3 = A~: H ~TH Equation r~
where PH = power radiated from housin~: to cathode A = Area EH = Emissivity of Housing cr= constant TH = Temperature of Housing The energy exchanged from cathode to housi,~g is obtained by substracting equation D from Equation C. The results are 3iven in EqJation E:
1~ EXC A~(c Tc -E~iTH4) Equation E
Inspection of the equation shows that the terms E T 4 and ~ ~iTH4 are the dominating terms because of the fourth power. Also, inspection reveals the closer TH iS to Tc,the smaller the power exchange. Therefore the design is performed to raise the temperature of the housing, as pointed out on pa3e 3. This design makes use of the thermal con-1~ duction equation (Equation F).
P = A ~ ~ T Equation F
cond cr ~ L
where P = Power of conduction cond ~ = Thermal Conduction Coefficient ~ T = change in te mperat ure L = change in length ACr = cross sectional area By selection of the right housing materiai, solar energy is passed through and heat radiated energy is absorbed. This absorbed power is the PCond in Equation F, the higherAT is for a given configuratiorl,~nd the, r vqlue is given by Equation G:
~T =TH ~ TA Equation G
Therefore TA or ambient temperature is a reference point, as ~ T increases the housing temperature TH will increase and as TH increases the power exchanged cathode to Housing will decrease.
Another independent variable in the equation is ACr or the cross-sectional area.
This is not to be c.onfused with Area. Area is the face ~rea of the device and cross-sectional area is the are~ of material in the housi~g and is given by Equation J:
A 1`(21rR) Equation J
where A = cross sectional area cr r= Thicknoss of houstng ~ = Radius at which thermal conduction calculation is needed.
Therefore by reducing the thickness of the housing the housing temperature can also be controlled.
~eduction of this process to practice, give, a housin3 material of Fused Silica- W
glass made by Corning Glass and a thickness ~f .394 ir~ches.other vari~tions have the fused silica welded to other types of glasses with different thicknesses. This combination will allow the housing temperature to be controlled so that the power radiated is minimized. In fact, in the future~ if a material can be found for the housing which has the above characteristics and a melting temperature equal to or gre~ter than t3~e cathode temperature, this power loss can be reduced to a valueapproaching ~ero.
With the solar to electric power system of Figure 11, the thermionic transducer 24 is sopplying power through a line system with switch 65 to a lamp 66.
2û The solar to electric pcwer system of Figure 12 has a transducer 24 connected in paral lel with an AC power supply 67, connected through an AC to DC convertor68 ond isolatcr 6, to supply power through a temperature control 70 employing atemperature sensor 71 for control of power to (lir conditioning unit 72.
'Nith the alternate air conditioning system of Figure 13, the DC power output of transducer 24 is converted to AC via convertor 73 and passed to a switch 74 controlled by a detector 75 for switching between the transducer supply power and power from alternate AC power source 76. These insure po~er supply through temperature control 70' as controlled bytemp~ rature sensor 71' for control of power to air conditioning unit`72'.
3û The transducer 24 in Figure 14 is the power source for an electric pump ;77.
--1~-- " .
5i9~i~
In Figure 15, transducer 24 is feeding DC to a DC to AC conve~tor 78 supplying AC :o a switch 79 controiled power line sysh~m ~o a fluorescent lamp 80. The tran~ducer 24 in the figure 16 system supplies DC through an on and off control 81~
controlled by a temperature sensor r32~ for an electric element 83 heater 84. Then with the system of Figure 17, a heating elemer.t 85 in boiler 86, Gnd when needed auxillary oil or gas heater 87, heati water in the boiler for distribution through heatin,a, system pipes 89 and 89 ~o and from a radiator 90 (or radiators) in an appropriate system.
Whereas, th;s invention is herein illustrated and described with respect to several embodiments thereof~ it should be rea'.ized that various chan~a,es may !~e made without depart;ng from essential contributions to the art made by the teachings hereof .
Claims (21)
1. In an energy to electrical power transducer for a radiant energy to electrical power conversion system, cathode means having a cathode face, anode means having an anode face; housing means structured to hold said cathode and anode faces as closely spaced faces of said cathode means and said anode means in a highly evacuated vacuum state, said cathode means being of high work function high melt temperature material; said anode being a relatively low work function material with said cathode face and said anode face spaced no more than approximately 0.002 of an inch apart to minimize space charge buildup and to optimize cross transfer of electrons from cathode to anode in a thermionic conversion process; wherein said cathode means is a rela-tively thin flat member having said cathode face at one side and a radiation receiving face on a radiation receiving side with both said cathode face and said radiation receiving face held in a vacuum state within said housing means and with said cathode means of high work function high melt tem-perature material of the class including molybdenum, niobium, and tungsten for cathode operation with radiant energy cathode means heating up into the range of approximately 2400° to 3600° Kelvin; and means for focusing solar radiated energy to a high energy elevated temperature spot on said radiation receiving face of said cathode means with said cathode spot area being substantially less than that of the face area of said cathode.
2. The transducer of claim 1, wherein said anode means is in the form of a heat sink of high thermal conductive rate material with a silver oxide coating at said anode face.
3. The transducer of claim 1, wherein Hafnium oxide cathode to anode spacing strips are deposited on said cathode face to a thickness of less than 0.001 inches.
4. The transducer of claim 1, wherein aluminum oxide cathode to anode spacing strips are deposited on said cathode face to a thickness of less than 0.001 inches.
5. The transducer of claim 1, wherein said anode has a heat sink body of high copper Content with high thermal conductivity for conducting heat away from the anode face.
6. The transducer of claim 5, wherein said anode body extends from said anode face positioned within said housing means to the exterior of said housing means.
7. The transducer of claim 6, wherein said anode body is equipped with heat radiating fin means.
8. The transducer of claim 5, wherein said anode body includes fin wall means fastened in place as an end wall of said housing means enclosing a housing vacuum chamber.
9. The transducer of claim 8, including current buss connective means connectable to said anode body.
10. The transducer of claim 1, wherein dielectric material means forms part of said housing.
11. The transducer of claim 10, wherein electric cir-cuit connective means connected to said cathode means is extended through said dielectric material means of said housing means.
12. The transducer of claim 11, wherein said cathode means is a relatively thin flat member of high work function high melt temperature material of the class including molyb-denum, niobium, and tungsten, said cathode is formed with a high temperature portion having a radiation receiving input side upon which a spot of radiated energy may be focused and an electron thermionic emission side, and with said cathode input side and said electron thermionic emission side being spaced at close spacing relative to the lateral expanse area of the high temperature portion of said cathode means and to the area of radiated energy impingement on the high tempera-ture portion of said cathode means.
13. The transducer of claim 12, wherein the input side and the electron thermionic emission side of said cathode high temperature portion are spaced approximately 0.04 of an inch.
14. The transducer of claim 12, wherein the input side and the electron thermionic emission side of said cathode high temperature portion are spaced less than one quarter of an inch.
15. The transducer of claim 12, wherein said cathode means is provided with lateral current carrying and mount arm means; and said electric circuit connective means is connected to said arm means.
16. The transducer of claim 15, wherein said dielectric material means includes a material section substantially transparent to focused solar radiant energy.
17. The transducer of claim 16, wherein said material section is made of fused silica U-V glass.
18. The transducer of claim 17, wherein said material section of fused silica U-V glass is approximately 0.4 inches thick in an area passing focused solar radiant energy.
19. The transducer of claim 18, wherein said electric circuit connective means is in the form of a plurality of conductive stud members extended through said glass, and a current ring connected to said plurality of conductive stud members outside of said housing means.
20. The transducer of claim 10, wherein said dielectric material means is in the form of material highly transparent to radiated solar energy and much less transparent to cathode emitted radiant energy.
21. The transducer of claim 10, wherein said dielectric material is fused silica U-V glass useful in achieving a housing greenhouse effect.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US721,800 | 1976-09-08 | ||
| US05/721,800 US4188571A (en) | 1976-09-08 | 1976-09-08 | Radiant energy to electrical power conversion system |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1095964A true CA1095964A (en) | 1981-02-17 |
Family
ID=24899352
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA286,102A Expired CA1095964A (en) | 1976-09-08 | 1977-09-06 | Radiant energy to electrical power conversion system |
Country Status (3)
| Country | Link |
|---|---|
| US (1) | US4188571A (en) |
| CA (1) | CA1095964A (en) |
| GB (1) | GB1592768A (en) |
Families Citing this family (26)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US20060021648A1 (en) * | 1997-05-09 | 2006-02-02 | Parise Ronald J | Device and method to transmit waste heat or thermal pollution into deep space |
| US5936193A (en) * | 1997-05-09 | 1999-08-10 | Parise; Ronald J. | Nighttime solar cell |
| US5973259A (en) * | 1997-05-12 | 1999-10-26 | Borealis Tech Ltd | Method and apparatus for photoelectric generation of electricity |
| US20040189141A1 (en) * | 1997-09-08 | 2004-09-30 | Avto Tavkhelidze | Thermionic vacuum diode device with adjustable electrodes |
| EP1166369A4 (en) * | 1999-03-11 | 2006-12-27 | Eneco Inc | Hybrid thermionic energy converter and method |
| US6396191B1 (en) | 1999-03-11 | 2002-05-28 | Eneco, Inc. | Thermal diode for energy conversion |
| US7109408B2 (en) * | 1999-03-11 | 2006-09-19 | Eneco, Inc. | Solid state energy converter |
| US6612041B1 (en) * | 1999-08-09 | 2003-09-02 | The Long Now Foundation | Diurnal solar event triggering mechanism |
| FR2819651B1 (en) * | 2001-01-17 | 2006-12-22 | Raymond Charles Etienne Navert | SOLAR CONCENTRATION POWER CURRENT PRODUCTION APPARATUS ACTING ON A VACUUM ELECTRODE ASSEMBLY |
| US6779347B2 (en) | 2001-05-21 | 2004-08-24 | C.P. Baker Securities, Inc. | Solid-state thermionic refrigeration |
| AU2002361643A1 (en) * | 2001-08-28 | 2003-03-18 | Borealis Technical Limited | Thermotunnel converter |
| US20050184603A1 (en) * | 2001-08-28 | 2005-08-25 | Martsinovsky Artemi M. | Thermotunnel converter with spacers between the electrodes |
| US6786422B1 (en) | 2001-10-30 | 2004-09-07 | Detroit Radiant Products Co. | Infrared heating assembly |
| US6946596B2 (en) * | 2002-09-13 | 2005-09-20 | Kucherov Yan R | Tunneling-effect energy converters |
| GB0415426D0 (en) * | 2004-07-09 | 2004-08-11 | Borealis Tech Ltd | Thermionic vacuum diode device with adjustable electrodes |
| US7788393B2 (en) | 2005-02-23 | 2010-08-31 | Cisco Technology, Inc. | Switching a client from unicasting to multicasting by increasing the unicast stream rate to the client |
| US7798268B2 (en) * | 2005-03-03 | 2010-09-21 | Borealis Technical Limited | Thermotunneling devices for motorcycle cooling and power generation |
| US7589348B2 (en) * | 2005-03-14 | 2009-09-15 | Borealis Technical Limited | Thermal tunneling gap diode with integrated spacers and vacuum seal |
| NL1029477C2 (en) * | 2005-07-08 | 2007-04-18 | Innovy | Energy conversion device, generator and heat pump provided therewith and method for manufacturing thereof. |
| GB0518132D0 (en) * | 2005-09-06 | 2005-10-12 | Cox Isaiah W | Cooling device using direct deposition of diode heat pump |
| US7427786B1 (en) | 2006-01-24 | 2008-09-23 | Borealis Technical Limited | Diode device utilizing bellows |
| US8713195B2 (en) * | 2006-02-10 | 2014-04-29 | Cisco Technology, Inc. | Method and system for streaming digital video content to a client in a digital video network |
| US8816192B1 (en) | 2007-02-09 | 2014-08-26 | Borealis Technical Limited | Thin film solar cell |
| WO2008100643A2 (en) * | 2007-10-25 | 2008-08-21 | Emmanuel Miepreyeh Keinkede | Keinkede engine pump (kep) |
| US8656904B2 (en) * | 2009-09-25 | 2014-02-25 | Detroit Radiant Products Co. | Radiant heater |
| CN111473530A (en) * | 2010-09-16 | 2020-07-31 | 威尔逊太阳能公司 | Solar power generation system using solar receiver and related apparatus and method |
Family Cites Families (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US3149246A (en) * | 1958-10-10 | 1964-09-15 | Bell Telephone Labor Inc | Thermoelectric generators |
| US3176164A (en) * | 1958-11-03 | 1965-03-30 | Gen Electric | High vacuum thermionic converter |
| US3462310A (en) * | 1959-08-20 | 1969-08-19 | Albert M Rubenstein | Apparatus for the conversion of solar energy to electrical energy |
| US3509385A (en) * | 1965-01-05 | 1970-04-28 | Teledyne Inc | Thermionic converters |
| US3551727A (en) * | 1967-06-15 | 1970-12-29 | Xerox Corp | Thermionic converter having a low work function collector electrode |
-
1976
- 1976-09-08 US US05/721,800 patent/US4188571A/en not_active Expired - Lifetime
-
1977
- 1977-09-06 CA CA286,102A patent/CA1095964A/en not_active Expired
- 1977-09-08 GB GB37486/77A patent/GB1592768A/en not_active Expired
Also Published As
| Publication number | Publication date |
|---|---|
| GB1592768A (en) | 1981-07-08 |
| US4188571A (en) | 1980-02-12 |
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