Solar Cell Surpasses 40 Percent Efficiency~ (NREL) verified the milestone.

ST. LOUIS, Dec. 06, 2006 -- Boeing [NYSE: BA] today announced that Spectrolab, Inc., a wholly-owned subsidiary, has achieved a new world record in terrestrial concentrator solar cell efficiency. Using concentrated sunlight, Spectrolab demonstrated the ability of a photovoltaic cell to convert 40.7 percent of the sun's energy into electricity. The U.S. Department of Energy's National Renewable Energy Laboratory (NREL) in Golden, Colo., verified the milestone.

"This solar cell performance is the highest efficiency level any photovoltaic device has ever achieved," said Dr. David Lillington, president of Spectrolab. "The terrestrial cell we have developed uses the same technology base as our space-based cells. So, once qualified, they can be manufactured in very high volumes with minimal impact to production flow."

High efficiency multijunction cells have a significant advantage over conventional silicon cells in concentrator systems because fewer solar cells are required to achieve the same power output. This technology will continue to dramatically reduce the cost of generating electricity from solar energy as well as the cost of materials used in high-power space satellites and terrestrial applications.

"These results are particularly encouraging since they were achieved using a new class of metamorphic semiconductor materials, allowing much greater freedom in multijunction cell design for optimal conversion of the solar spectrum," said Dr. Richard R. King, principal investigator of the high efficiency solar cell research and development effort. "The excellent performance of these materials hints at still higher efficiency in future solar cells."

Spectrolab is reducing the cost of solar cell production through research investments and is working with several domestic and international solar concentrator manufacturers on clean, renewable solar energy solutions. Currently, Spectrolab's terrestrial concentrator cells are generating power in a 33-kilowatt full-scale concentrator system in the Australian desert. The company recently signed multi-million dollar contracts for its high efficiency concentrator cells and is anticipating several new contracts in the next few months.

Development of the high-efficiency concentrator cell technology was funded by the NREL's High Performance Photovoltaics program and Spectrolab.

Solar cell roof panels and so on are now available that will supply the average home with power to run all our toys provided the system is part of the mortgage package.
Finannng a solar system at 5 0r 6 percent apr via home mortgage versus financing the same system through personal loans or credit cards at 14 percent plus makes the difference.
I doubt many home lenders are ready to do this.
Many obscure regulations probably exist barring the batteries needed for one thing;neither lead nor cadmium or supposed to be in homes in many cities.

We are really a nation of laws now;too darn many if you ask me.

OK.

Figure it this way.

(Everything depends on your location (higher latitude = less solar incident rays per sq meter than a southern desert test site near Mexico), weather = (compared to a cloudless desert!) will ALWAYS mean you can never get as much power as at this test site , altitude + humidity (anything in the air reduces incident rays on the panel), cleanliness (any dirt or pollution or dust on the surface or in the air reduces incident sunlight.) If you have nearby buildings or trees, they reduce by shading the effective area of the sun's arc that you get usable exposure. If you aren't exposed directly to the south facing sun's arc through the sky all day, you get no power. For me, almost all of my roof is shaded almost all of the day, so I get power only from 11:00 to 1:30 in summer. Less in winter.

They are using a collector (or mirror-like concentrator) so the actual roof area req'd is bigger than the solar area of the cell. So, if your roof was 30 ft x 50 ft, you could cover the entire roof with the concentrator, but the actual cell are might be 50-25% of the collector area.

OK. So this was ideal test site conditions. The news is good (to solar enthusiasts) because previous efficiencies couldn't get over 7-15% in routine production of clean cells, and 20-32% under ideal conditions.

using nominal values, to actually run your a one-story average house from the sun from 9:00 - 3:30 (the maximum actual hours the sun is usably producing power!), you need a cell area about the size of 1/4 - 1/3 your roof - assuming the whole roof faces south at the right angle. To run the house (with "usual" electric loads!) from 6:00 AM to 6:00 pm, you need to add batteries, a DC-AC converter, solar controller (needed anyway really) and a battery system charge controller.

OK. All those converters and controllers reduce efficiency - since you're pulling power from the batteries for half the time, and charging the battery half the time. So you need just about the half the roof to run your house half the day - during daylight hours.

To run solar full time, double the area (less electric power is used at night, but during part of the night almost all of the loads are off. Making up is the greater drain on the batteries and less efficiency of the solar-battery-chemical-DC-to AC conversions.... Daytime hours, much of the solar input doesn't need to get reconverted to battery chemical power first. It's used immediately.

AWhat most (almost all!) solar users do is really eliminate almost all of their electric loads: no AC, high efficiency motors, lights, fewer lights, TV, no instant-on appliances, high efficiency refrigerators, etc, etc. All of these cost a LOT more.

The usual figure for planning is to allow for 4 cloudy and lost days for the storage cvapcaity. That much capacity adds more solar bank req'd to charge it and keep it up - not a lot, but a bunch.

Solar is really only practical (for houses!) where the site is so far from the grid that lines (at 10,000 per mile, if not more) are so expensive that the 25,000 investment is "rational" ....

It makes a nice demo. But you can't run much right now.

Currently, Spectrolab's terrestrial concentrator cells are generating power in a 33-kilowatt full-scale concentrator system in the Australian desert.

"Standard test conditions" for solar energy are 1000 watts per square meter, so you'd need about 83 square meters to produce 33 KW at 40% efficiency, or a 9 m by 9 m array of mirrors and collectors, plus the control capability to keep it pointing at the sun. I'm guessing this would provide the air conditioning power for about 4 or 5 homes in the Australian (or Arizona desert), so Phoenix would need about a quarter million of these things to replace the power required for home air conditioning.

Think of running directly from a converter as hooking your sink up to a tee from a 1" firehose that somebody else keeps turning on and off. (Clouds cover the sun for a few minutes, for example. Your oven and the AC start at the same time, etc.)

IF (big if) you're using more power than the cell is providing all the time, then you're more or less balanced: both the grid and the solar cells (via the AC converter) are providing power.

But the random nature of the loads, and the power available from the converter really make it much better to have a battery charger and 2-4 batteries on-line constantly to balance and stabilize the system. Less surges, less up-and-down in current. The charge controller charges the battery when AC loads go down, or pulls power from the battery when AC loads go up, or when available solar power reduces suddenly.

But there's nothing to balance the system if there's no battery.

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