The most efficient solar cells currently on the market today are also the most expensive. Unlike traditional silicon cells commonly used in photovoltaic consumer power setups, NASA relies on multijunction germanium, gallium-indium-arsenide, and gallium-indium-phosphide cells due to their much higher efficiencies. Unfortunately germanium, a semiconductor like silicon, is far scarcer than silicon, with costs of about $680 per pound. Further, the traditional cutting processes for the germanium cells brass-coated, steel-wire saws typically waste much of the wafer due to cracking, as germanium is a hundred times weaker than silicon.
A new cutting method has been devised by University of Utah engineers that promises to cut costs. In the new approach, researchers used an electrified molybdenum wire 75 to 100 microns thick, often used in machining tools, to cut the cells (in contrast the typical saw is 170 to 180 microns thick). The result was that they were able to cut cells with virtually no cracking and even cut thinner cells, previously infeasible to process, with little to no cracking.
Eberhard "Ebbe" Bamberg, an assistant professor of mechanical engineering, describes, "The idea is to make germanium-based, high-efficiency solar cells for uses where cost now is a factor. You want to do it on your roof."
Currently, the 4-inch wafers in germanium solar cells cost $80 to $100 each. Grant Fines, chief technology officer for germanium wafer-maker Sylarus Technologies in St. George, Utah says the new processing method may reduce costs at his company by more than 10 percent. He states, "Anything that can be done to lower this cost ultimately will lower the cost of solar power per kilowatt-hour, which is beneficial. That's why this technology Ebbe has come up with is very intriguing. (It will) reduce the amount we have to recycle and increase the yield. It has the potential to give good savings, which helps enable this technology here on Earth."
The new method has been extended to a patent pending multiwire approach which Professor Bamberg compares to an egg slicer. This approach should help make the method ready for mass production.
Germanium cells have a maximum theoretical efficiency of over 50 percent. Using concentrators, efficiencies as high as 40 percent can be achieved. With traditional silicon solar cells, 20 percent conversion of sunlight to electricity is about the theoretical maximum.
Using current 300 micron thick wafers, the production yield was increased 30 percent. With thinner 100 micron wafers, production was up a whopping 57 percent. Perhaps most importantly, "kerf", or wasted germanium, was reduced by almost 22 percent.
The one remaining piece of the puzzle is to reduce the time of the cuts. Currently the method takes 14 hours, while traditional cutting takes 6 hours. While the new approach offers the possibility of crack free cutting, it currently has to be done a more ginger speed to avoid such cracking. However, Professor Bamberg and his fellow researcher Dinesh Rakwal, a doctoral student in mechanical engineering, are confident they can reduce the time to 6 hours before long. If this prediction holds true, this would be a very significant development to the solar power industry.
The new research appears in the Journal of Materials Processing Technology.
quote: Most steel engines have a thermodynamic limit of 37%. Even when aided with turbochargers and stock efficiency aids, most engines retain an average efficiency of about 18%-20%
quote: Sterlity and genetic alterations are quite well understood.
quote: Except you couldn't be more wrong -- solar costs have dropped, and dramatically.
quote: it will become cost competitive with fossil fuel technologies in a couple decades.
quote: I heard that over 30 years ago, and it hasn't happened yet.
quote: to disregard renewables as being part of the solution
quote: It's going to take years of marketing to change people mindset on that one.
quote: Forget waiting! Just shove it down peoples throats like solar, wind, and CFL's are doing.
quote: You forgot your original divisor of two, to allow for, as you put it "various inefficiencies and losses". I left it alone, as with the actual coulometric charging losses (30%), inverter conversion losses (20%) and a few other factors, its fairly close.
quote: assume a household size of two and you get a value of 2600 KW-h. That's for a normal household. I assumed a value of nearly half that , since this is a small cabin.
quote: Here's one for you. My usage last month was 4074 Kwh, for a four-person household in a very large, but very-well insulated home (substantially above local construction standards, with low-e argon-filled windows, R-19 walls, R-38 ceilings, and energy-star appliances.
quote: Add in another 1000 peak watts for daytime usage and you get maybe 3000 peak watts total. Add in various conversion losses and you might bump that to 4000, though I doubt it.
quote: If you have a specific problem with the numbers of mine that you quote please join in with that
quote: Anyone with the sense God gave a peanut knows you can't power your whole house with a cheap solar system.
quote: As I'd expected, you posted more smartass remarks instead of politely asking questions
quote: You really need to get a life.
quote: I recently went to Canada with my in-laws to visit some friends of theirs who own a couple cabins on a lake.
quote: I was very shocked when we arrived and I saw that both the guest cabin (a very nice A-frame) and the main house were equipped with banks of solar panels, microwaves and indoor plumbing. .
quote: But until then, it belongs in the lab, not the marketplace.
quote: Valid points. But how are renewables going to be a part of the solution in 20 years time without large scale commercial trials and also government subsidies?
quote: Photovoltaic systems installed in the areas indicated by the dark disks on the map would produce an average electric output of 18 TWe, i.e. 3 TWe each when assuming a conversion efficiency from incident sunlight to electricity of 8 %. This corresponds to an energy output of 13,567 Mtoe per year (world total primary energy supply (TPES) in 2003: 10,579 Mtoe ). The following table lists the locations in the map to give an idea of land area requirements and availability, although the particular scenario shown is suboptimal for many political and technical reasons. Location / Desert Desert Size / km2  Irradiation / W m-2 Area required / km2 Africa, Sahara 9,064,960 260 144,231 Australia, Great Sandy 388,500 265 141,509 China, Takla Makan 271,950 210 178,571 Middle-East, Arabian 2,589,910 270 138,889 South America, Atacama 139,860 275 136,364 U.S.A., Great Basin 492,100 220 170,455
quote: Long-distance transmission of electricity (thousands of miles) is cheap and efficient, with costs of US$ 0.005 to 0.02 per kilowatt-hour (compared to annual averaged large producer costs of US$ 0.01 to US$ 0.025 per kilowatt-hour, retail rates upwards of US$ 0.10 per kilowatt-hour, and multiples of retail for instantaneous suppliers at unpredicted highest demand moments). Thus distant suppliers can be cheaper than local sources (e.g. New York City buys a lot of electricity from Canada). Multiple local sources (even if more expensive and infrequently used) can make the transmission grid more fault tolerant to weather and other disasters that can disconnect distant suppliers.
quote: Until we have a few quantum advances in energy storage
quote: and transmission technology,
quote: In several decades, perhaps. Not now
quote: echnology to cheaply transmit power long distances does not exist. HVDC will lose a substantial portion of the energy over continental distances, and superconducting lines can cost tens of millions of dollars per mile.
quote: HVDC links are sometimes used to stabilize against control problems with the AC electricity flow. In other words, to transmit AC power as AC when needed in either direction between Seattle and Boston would require the (highly challenging) continuous real-time adjustment of the relative phase of the two electrical grids. With HVDC instead the interconnection would: (1) Convert AC in Seattle into HVDC. (2) Use HVDC for the three thousand miles of cross country transmission. Then (3) convert the HVDC to locally synchronized AC in Boston, and optionally in other cooperating cities along the transmission route. One prominent example of such a transmission line is the Pacific DC Intertie located in the Western United States.  Grid exit
quote: It only works in the real world, yes. In fantasy-land where "money" is a fuzzily-defined quantity that the government possesses unlimited quantities of, its' no problem at all.
quote: In the Phoenix, Arizona area, for example, the average annual solar radiation is 5.7 kWh/m²/day, or 2080.5 kWh/m²/year. Electricity demand in the continental U.S. is 3.7*1012 kW•h per year. Thus, at 100% efficiency, an area of 1.8x10^9 sq. m (around 700 square miles) would need to be covered with solar panels to replace all current electricity production in the US with solar power, and at 20% efficiency, an area of approximately 3500 square miles (3% of Arizona's land area). The average solar radiation in the United States is 4.8 kwh/m²/day, but reaches 8–9 kWh/m²/day in parts of Southwest.
quote: Unfortunately, cells of even 50% efficiency don't exist,
quote: Your figures also ignore angle of incidence and several other factors (the dangers of quoting Wikipedia