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Technology Stocks : The *NEW* Frank Coluccio Technology Forum -- Ignore unavailable to you. Want to Upgrade?

To: Curtis E. Bemis who wrote (153)	6/9/2000 10:33:00 PM
From: ftth	Respond to of 46821

I found this on the latest-greatest experimental solar cell efficiency: Nitrogen added to GaAs makes solar cells smaller. Electronics Times, March 20, 2000 p8 Photovoltaic power sources based on indium gallium arsenide nitride (InGaAsN) will have an efficiency twice that of a standard silicon solar cell, say scientists at Sandia National Laboratories in the US. This will result in smaller solar cells for space communications satellites. The addition of 1 or 2% nitrogen in gallium arsenide dramatically alters the alloy's optical and electrical properties, giving it characteristics suitable for satellite photovoltaics and laser applications, says Eric Jones, a Sandia physicist who has been working with the material for three years. Nitrogen, a small atom with high electronegativity, has a large effect on gallium arsenide's bandgap structure: it reduces the material's bandgap energy by nearly a third. Jones said: "In the semiconductor world, this is unheard of. The new material allows designers to tailor properties for maximum current production with different bandgaps." InGaAsN has a potential 40% efficiency rate when put into a state-of- the-art multi-layer cell. That is nearly twice the efficiency rate of a standard silicon solar cell. Jones says an InGaAsN solar cell that could provide power to a satellite will ultimately have four layers. The top layer would consist of the alloy indium gallium phosphide; the second of gallium arsenide; the third of 2% nitrogen with indium in gallium arsenide; and the fourth, germanium. Each layer absorbs light at different wavelengths of the solar spectrum. The absorbed light creates electron-hole pairs. Electrons are drawn to one terminal and the holes to the other, producing electrical current. Existing satellite systems use either silicon for solar cells or a two- layered solar panel made up of the indium gallium phosphide layer and the gallium arsenide layer. Jones said: "With InGaAsN, the size of the solar collecting package can be smaller, meaning the satellite will weigh less, come in a smaller package, and be cheaper to launch." But before InGaAsN can realistically be used in a photovoltaic system, the material must be better understood and a higher quality alloy needs to be developed. Researcher Andy Allerman said: "We are doing a lot of tweaking to try to make the material viable. This includes changing some things in the growth process - like temperature - and then measuring its effects after the InGaAsN is grown. We're trying to understand the optical and electrical properties." InGaAsN could also be used as a laser material that will produce the 1.3 micro m bandgap needed for short-distance fibre optics systems. Without the addition of nitrogen, gallium arsenide's bandgap is too high to serve as a laser source. But with nitrogen, the bandgap falls in the usable range of 0.7 to 1.4 micro m By changing the amount of nitrogen doped into the gallium arsenide, researchers can alter the laser's bandgap. They have already built an edge emitter, which is the first step toward incorporating the material into a vertical cavity surface emitting laser structure. ============= also this snip from another article: Never mind the suntan.... Electronics Weekly, April 28, 1999 i1907 p18(1) By Reynolds, Melanie <snip> "Mason believes that the highest efficiency achieved for solar panels so far is 23 per cent in laboratory conditions. "But they tend to be on very high quality substrate which is expensive." ================================ and 1 more: Australian improvement in PV cell conversion rate. Petroleum Times Energy Report, May 8, 1998 Independent testing by the Sandia National Laboratories of New Mexico has confirmed that Australian research has achieved improved rates of sunlight-to-energy conversion for photovoltaic multicrystalline and monocrystalline cells. At the University of New South Wales Photovoltaics Special research Centre, Martin Green and his team have recorded a conversion efficiency rate of 19.8% for a multicrystalline cell and a 24.4% improvement rate for a monocrystalline cell. The UNSW's research bulletin reports that the Centre's sunlight-to-electricity conversion efficiency has eclipsed the previous world records for these types of cells of 18.6%, set by GeorgiaTech in 1995 and its own old record of 24%, established in 1994. Green said the 19.8% result for multicrystalline cells was encouraging for the development under way at Pacific Solar, the A$64m joint venture between Pacific Power and Unisearch Ltd, the UNSW's technology company. "The lessons we are learning from this 19.8% result are directly relevant to the laser-grooved polycrystalline thin cells that Pacific Solar will soon be manufacturing. They also confirm the accuracy of the theory on which the work at Pacific Solar is based and make the company's target efficiency of 15% look relatively modest." Pacific Solar's managing director, David Hogg, said his company would be in pilot production by the middle of this year. "This plant will produce 30 x 40[cm.sup.2] solar modules and, by the end of 2000, we plan to have our first full scale production plant in operation, producing panels one metre square. We plan ultimately to be competitive with the delivered cost of conventional electricity."

To: Curtis E. Bemis who wrote (153)	6/10/2000 1:32:00 PM
From: Frank A. Coluccio	Read Replies (1) \| Respond to of 46821

Why are you (we?) persisting on discussing the efficiencies at 1550? Is this, in your opinion, the optimal wavelength to pursue for the purpose of energy transport over fiber? Curious. My thoughts are still centered on a paired, second strand that does nothing but handle "contingency powering" and possibly some non-bearer control and network management information at low speeds. The power aspect would be solely for a single voice service for lifeline purposes. It is not the responsibility of an integrated services provider to power all household appliances. All that is required is that which is enough to drive a keypad and the earpiece (possibly an integral speaker for ringer emulation) of a specially-designed high-efficiency phone when the lights go out. FAC oops, I should learn to read the entire thread first, prior to responding...