This is a revision, and improvement over an earlier concept for advanced but small-scale solar conversion, not requiring steam nor expensive solar panels.
Here is a rather spectacular image of a "parabolic trough" type of solar collector.... makes a nice 'wallpaper' for you computer desktop: http://www.trec-uk.org.uk/press/brussels/schott_parabolic_trough.jpg And - on my desktop for the past months - it has stimulated an alternative implementation. Typically the tube running down the spine of the trough is filled with a molten salt which collects the heat from focused sunlight. That heat is then converted into steam in an adjoining building, and the steam is then expanded through a turbine to produce electricity at about 23% efficiency. This system is in active and growing usage now; but steam conversion demands a minimum size, and a rather large minimum size - in the range of megawatts. This system is much more cost effective than "printed" nanosolar type panels but the minimum-size is the deterrent for home use. Is there a better way to do this without steam, and one which is feasible for usage on an individual home at about half (or less) the cost of nanosolar printed panels ? Maybe. Here is an alternative concept based on the same kind of parabolic trough, but shorter - and used as the amplifier for a type of "reverse gyrotron" in which terhertz radiation, in addition to microwaves, are employed to accelerate a beam of electrons - thus "reverse teratron" A gyrotron is a high power microwave generating device, consisting of an electron gun and beam accelerator and a resonance chamber in a strong magnetic field. Microwaves are generated by the interaction of the beam and external field (at the gyro-frequency), followed an electron collector to recover some of the energy expended This frequency is spatially matched to the dimensions of the resonance chamber where relativistic electrons interact with the electromagnetic field. The decelerated electron beam reaches a collector where its remaining energy is deposited and recycled. A "reverse gyrotron," on the other hand- operates the other way to convert microwaves back into DC electricity. It can be highly efficient. The key patent (now expired) was owned by Siemens. US3462636: SYSTEM FOR THE CONVERSION OF MICROWAVE ENERGY INTO ELECTRIC DIRECT CURRENT ENERGY UTILIZING AN ELECTRON BEAM TUBE The key component of the converter is the so-called "Cuccia coupler." This coupler is perhaps the least-well-known device in all of energy physics for the high efficiency direct conversion of photons to electrical current. The key missing ingredient - for whether this concept is applicable to solar energy is also in the "coupling" factor. Will terahertz photons couple to microwaves first, and then to an electron beam secondly in a two-step process? That is unknown. The reverse gyrotron begins with an modest electron beam and provides a means of imparting a spiraling linear amplification to it - as is in the TWT (traveling wave tube). This allows for efficient coupling of EM energy in photons to electrons (the beam). The device - as developed by Siemens, a company not known to exaggerate claims, has a reported conversion capability "up to 90%" (for the conversion of microwave energy into DC). As envisioned, this alternative solar converter is a short parabolic trough collector, with a small diameter tube (1/4 wavelength of the modulation wave frequency- 3 cm or so). The tube would be made of graphite, with a metal skin and with a carbon (possibly nanotube) interior wall, which emits semi-coherent terahertz radiation (near IR range). This kind of carbon emitter has already been demonstrated to downshift visible spectrum radiation to semi-coherent terahertz radiation efficiently. It is the secondary coupling which is unknown. The tube is hollow and at a partial vacuum. At one end is a magnetron which emits GHz radiation, and at the other end is collector. 2.45 GHz is the most convenient wl, since it is the FCC permitted frequency used in microwave ovens. Anyway, the modus operandi, as envisioned now, is that semi-coherent terahertz radiation from the tube's interior wall (from the carbon lining) will effectively boost (amplitude) the modulation wave (2.45 GHz) which is traveling down the axis of the tube; and at the same time, the electron beam will be secondarily boosted by the microwaves (or by both). This is an analogy to the principle which is used to boost modulation waves in the gyrotron microwave tube but it involves two steps in order to get the geometry of the wave up to centimeters, where it is most useful. Importantly, there will be electron emission from the tube interior wall, which can enhance by semiconductor techniques. Many carbides have bandgaps of interest. The collector could be an air-cooled direct converter which is really a hybrid microwave antenna and multipactor (original Farnsworth type). The idea (just a hope for now) is that IF say: one kilowatt of RF is emitted by the magnetron, it would be boosted to say 10 kW by the cross-field of the THz emission, and 9 kW collected and 1.5 kW recycled so that the net is 7.5 kW for use by the home during daylight hours. The bottom line is that an electron beam is collected at very high efficiency and without the need for a steam cycle. Jones
