The power in the sunlight falling on the Earth exceeds civilization's energy needs by almost four orders of magnitude. One of the more attractive ways to utilize the sun's energy is to use photovoltaic cells, which convert light directly to electricity. These cells are safe, have no moving parts, operate at ambient temperatures and last for decades. It turns out that the predominant type of solar panel being produced today cannot solve the world's energy problems any time soon -- simply because the device takes too much energy to manufacture. The inherent problem is that photovoltaic cells are composed of silicon. Although abundant in the form of silicon dioxide, the pure element requires considerable amounts of energy to extract. . Consensus is that it takes three years for a silicon photovoltaic panel to produce the amount of electrical energy that was required to manufacture its equipment in the first place. Having an energy payback time of three years might not seem bad. The problem comes when you consider how much the photovoltaic industry would need to grow in size to compete seriously with other forms of electric power generation. Presently, photovoltaic cells world wide only generates about 6 gigawatts -- a drop in the bucket compared with global electricity use, which demands terawatts of power. Last year the photovoltaic industry increased by 36 percent, and alternative energy advocates would, ideally, like to see such rates maintained. The rub is that with an energy payback time of three years, growing the industry at this pace requires more energy than all the existing photovoltaic cells produce. That is, even if you could somehow harvest all the energy produced by ever single photovoltaic cell existing in the world today for one full year, the total wouldn't be sufficient to keep pace and produce the next year's crop of panels. Andy Black, speaking at the Solar World Congress said, "It's a mathematical oddity. We've got this wonderful, clean industry that's actually using coal to power it." We're not going to make a difference unless we grow fast, (and growing fast requires too much energy)". NOW THE GOOD NEWS. Michael Graetzel, a professor of chemistry, began to work on a way to produce solar cells without silicon. The result is the "Graetzel" or dye-sensitized solar cell. The cell uses a combination of titanium dioxide, and an organic dye immersed in a liquid electrolyte, which has an energy payback time of only a half-year or so. Dye-sensitized solar cells are standing on the threshold of large scale commercialization. G24 Innovations, headquartered in Cardiff, Wales, will be manufacturing the new sensitized cells using a continuous process. Instead of coming off the assembly line in discrete, rigid unites, the dye-sensitized cells are placed on a half mile long roll of flexible metal foil. G24 expects to be able to make enough of the dye-sensitized photovoltaic cells in the first year to provide 30 megawatts of peak generation capacity. Other manufactures are also sprinting very hard to beat out other competitors. (American Scientist) - Millet

That would be good news indeed. Now we only need to develop a better energy storage media so that we can use that solar energy whenever we want, but making it is the first step.

There have been many innovations. Now the CIGS are going into manufacturing and they are orders of magnitude cheaper than silicon based solar cells. However, the cheaper for manufacturers doesn't mean cheaper for consumers. It will be priced according to market forces.

Latest theoretical development can peg the efficiency to around 70% solar to electric conversion. Direct storage to hydrogen are around 50% and the price would be the mirrors and catalysts.

There are exciting news ahead.

Still, even if the solar cells are at 5% conversion efficiency, they're far much better efficiency than any photosynthesizing plants to generate electricity.

I will be gladly holding off buying any solar cells until it has come down in price to the equivalent of 1/10th of today's price per kW power.

Millet, Thank you for that information. I have been keeping and eye on this subject on and off for years. I would like to (someday) become self sufficient in my energy usage (wouldn't we all), and I am very interested in solar for this reason. A 3 year payoff in energy to produce these units seems high, I wonder what the translation is for the consumer based on purchase price. Like Skeet says, the energy storage now becomes the issue.

Could you point me in the right direction on where you found this informaton? My brother and I go back and forth on whether solar will ever be feasible in Pennsylvania as a replacement to other energy for electric and heat. Everything that I have read to date has indicated an energy capture efficiency of 28%. I would like to read more about this.

Thank you in advance, Barbara

Barbara, first the 3 year figure is based on a solar panel located in a high sunlight areas. I assume the payback time would be even worse in areas like Seattle, or in the north eastern section of the country where they enjoy less sunshine, than say the southwest part of the country. At the end of my post I wrote "American Scientist" which stands for the American Scientist magazine, which had the article that I was quoting. - Millet

Here's a very old news about DOE certified world record solar efficiency:

December 5, 2006

New World Record Achieved in Solar Cell Technology
New Solar Cell Breaks the “40 Percent Efficient” Sunlight-to-Electricity Barrier

WASHINGTON, DC – U.S. Department of Energy (DOE) Assistant Secretary for Energy Efficiency and Renewable Energy Alexander Karsner today announced that with DOE funding, a concentrator solar cell produced by Boeing-Spectrolab has recently achieved a world-record conversion efficiency of 40.7 percent, establishing a new milestone in sunlight-to-electricity performance. This breakthrough may lead to systems with an installation cost of only $3 per watt, producing electricity at a cost of 8-10 cents per kilowatt/hour, making solar electricity a more cost-competitive and integral part of our nation’s energy mix.

“Reaching this milestone heralds a great achievement for the Department of Energy and for solar energy engineering worldwide,” Assistant Secretary Karsner said. “We are eager to see this accomplishment translate into the marketplace as soon as possible, which has the potential to help reduce our nation’s reliance on imported oil and increase our energy security.”

Attaining a 40 percent efficient concentrating solar cell means having another technology pathway for producing cost-effective solar electricity. Almost all of today’s solar cell modules do not concentrate sunlight but use only what the sun produces naturally, what researchers call “one sun insolation,” which achieves an efficiency of 12 to 18 percent. However, by using an optical concentrator, sunlight intensity can be increased, squeezing more electricity out of a single solar cell.

The 40.7 percent cell was developed using a unique structure called a multi-junction solar cell. This type of cell achieves a higher efficiency by capturing more of the solar spectrum. In a multi-junction cell, individual cells are made of layers, where each layer captures part of the sunlight passing through the cell. This allows the cell to get more energy from the sun’s light.

For the past two decades researchers have tried to break the “40 percent efficient” barrier on solar cell devices. In the early 1980s, DOE began researching what are known as “multi-junction gallium arsenide-based solar cell devices,” multi-layered solar cells which converted about 16 percent of the sun’s available energy into electricity. In 1994, DOE’s National Renewable Energy laboratory broke the 30 percent barrier, which attracted interest from the space industry. Most satellites today use these multi-junction cells.

Reaching 40 percent efficiency helps further President Bush’s Solar America Initiative (SAI) goals, which aims to win nationwide acceptance of clean solar energy technologies by 2015. By then, it is intended that America will have enough solar energy systems installed to provide power to one to two million homes, at a cost of 5 to 10 cents per kilowatt/hour. The SAI is also key component of President Bush’s Advanced Energy Initiative, which provides a 22 percent increase in research and development funding at DOE and seeks to reduce our dependence on foreign sources of oil by changing the way we power our cars, homes and businesses.

For more information, visit the Solar America Initiative website at: http://www1.eere.energy.gov/solar/solar_america/

Sorry Millet, I guess I've been a little off my game lately. Should have seen your reference. Thanks, Joe.

I am puzzled as to how the Authors of American Scientist Magazine is able to come up with a Pay-off in just three years. I think they have omitted the biggest part, which is the interest of investment capital. Would you save or earn more money by just investing your money in a stable porfolio and paying off your electric bills instead of buying into solar power?

Let us make some very realistic assumptions here, you can adjust it for your area, depending on typical costs. I am not factoring in subsidies, simply because any subsidy from the government, is also money that could have been much better spent elsewhere. I for one don't like subsidizing people in the oil industry as well as solar industry.

A typical total cost installation in a typical home in our area is $12,000 per installed peak Kilowatt power. The typical roof size and current efficiency, means that a maximum of 4 kW peak power capacity can be installed, thus the typical for our area without any subsidy is $48,000.00. That amount of solar panel will on the average replace only about 25% of our typical electric consumption.

Take note that the rating is 4 kW peak power, which means that averaged over the entire year, you will only get about 15 kWH per day or 456 kWH per month for the $48,000.00 solar investment.

Now compare these realistic data:
Average price of electricity is: 12.82 cents/kWH in California
( http://www.eia.doe.gov/cneaf/electricity/epa/fig7p4.html )
Thus you will save: 456 kWHr/month x $0.1282/kwHr = $58.46 per month.

And now for the shocking fact that may not have been considered by the authors:
Opportunity cost of investment: on the average, low risk, you can get 10% APR.
A 10% APR on $48,000.00 investment would net you $48,000 x 10%/12month = $400/month.

Banging head on the wall: Should you rather lose $400/month in your investment gains to save $58.46 per month on electricity?
Lost Income Opportunity: $341.54/month. Even if the government has subsidized 50% of your total solar installation, you would still lose $141.54 each month of each year even till the end of time.

More realistically, a typical homeowner is not that rich, so he would apply for a loan, and such loans typically would have 12% effective APR. If we applied for a loan at 12% APR, this would mean, it is going to cost us an interest money of $480/month. And if subsidized at 50%, that would still cost you $240/month.

So to point out the obvious:
Amount of electricity produced: $58.46/month
Interest rate of solar power installation: $480/month
Interest rate at 50% subsidy: $240/month

Conclusion: It is a mathematical impossibility to ever reach any payoff, subsidized or not. Thus the three years payoff is really dubious or based on very unrealistic assumptions.

Thus the price of solar power installation has to come down. It should come down to $1,500 per kW peak power capacity installed. Another way which PG and E and the oil tycoons would love is to increase the price of electricity by ten fold, and only then will there be payoff from solar installations.

I keep a closer eye on tracking of technological and political developments in the solar industry. It is still not feasible at this point in time. Thus my best educated guess tells me to check and compare prices after 3 years.

The Bush administration has recently pulled the plug on solar subsidies and research. That's a big youch!

I read the excerpt from American Scientist to say that it was not a 3 year financial payoff, but an energy balance on the actual manufacturing of the unit itself. It would take 3 years for the unit to produce the amount of energy that was used to manufacture it in the first place.

That being said, the only other major fault that I see in your financial argument is that a homeowner with equity can more likely than not get a loan for half to two thirds the rate that you quoted (especially right now). That would not change your conclusion, though. Barbara

Barbara, isn't that exactly what I wrote above. Also, why would anyone take out a loan, just to install solar? Installing solar is an effort to save money, that would only increase the cost, and make the situation even worse. - Millet

Yes, Millet, that is what you said. I was commenting on JoeReal's financial evaluation of the data. I read his position to be based on a 3 year financial recovery, not a 3 year energy recovery. Maybe I misunderstood. I agree with you on the loan, also. Joe presented a loan scenario in his argument, so I just commented on it. Barbara