Photovoltaics reaches for respectability

Tuesday, February 21, 2017

By Brad Lang

Solar power came briefly into vogue during the OPEC oil crisis of the 1970s, but as soon as the gas crunch passed, it once again became the province of dreamers. But during the past year or so, two things have* happened to change that forever.

It took years, but the Greenhouse Effect has finally become a recognized phenomenon. It also took a drought, record high temperatures, a violent hurricane, new acid rain findings, and a rise in pollution levels – all of which occurred during the past few years, and most of it can be traced to the use of fossil fuels. And while the ‘70s oil embargo was significant, the environment as crisis is of a different order of magnitude; it's one thing to live without a car, but quite another thing to live without a planet.

Suddenly, solar power is becoming respectable! But it has taken more than just fear of the Greenhouse Effect to give solar power its new-found shine. The change in attitude is also due to a number of important research breakthroughs. Strictly speaking, solar power in the form of wind and hydroelectric power (which ultimately depend upon the sun)has been in use for thousands of years.

The science of photovoltaics – the transformation into electricity – is a more, recent development, though not particularly new. Solar cells have been used in space or more than 40 years to power most communication and military satellites, and small solar cells are employed in watches, radios and calculators.

The U.S. Coast Guard reportedly the single largest user of solar power – employs solar cells in buoys to reduce maintenance. In short, we know how to do it; the problem is that we don’t yet know how to do it inexpensively enough to make photovoltaics a practical, large-scalesource of energy.

Researchers focus on reducing solar power Costs

In order to be competitive with conventional power generation, solar power will have to be produced at a cost of about two dollars or less per watt of power. At the present time, the practical cost of a total system is closer to $8 – $10 per watt.

Reducing the cost further will depend upon lowering the material and labor cost and increasing the energy conversion efficiency. That now appears to be happening, as several groups of companies, universities and government agencies focus their resources on the challenge.

A company called Energy Conversion Devices, Inc. (ECD), based in Troy, Mich, and headed by the brilliant but controversial (Stanford Ovshinsky, has been working in the field of photovoltaics since the early ‘60s. ECD has concentrated on amorphouscrystalline materials with a random arrangement of atoms – an emphasis which was once thought to be scientific heresy, but has since resulted in many practical applications in fields other than photovoltaics.

Last December, the Solar Energy Research Institute (SERI), a U.S. Department of Energy project, announced that ECD had fabricated a triple-junction amorphous silicon panel with an area of 818 square centimeters (88 square feet) that had a sunlight-to electricity conversion efficiency of 8.4 percent.

This is significant because multijunction devices (which use two or more solar cells in combination) can potentially achieve efficiencies of 18 percent, while single junction devices are limited to 12 percent. ECD has since reported achieving efficiencies of better than 13 percent.

What is also significant is that ECD achieved this breakthrough using relatively inexpensive materials. And the company's Sovonics subsidiary already has automated equipment which makes solar celis in thousand foot rolls.

Further south, at Georgia Tech’s Microelectronics Research Center, researchers have come up with a device which concentrates solar rays to an intensity of five hundred to one thousand suns. Scientists at Sandia Laboratories have used this principle with a tandem solar cell made of silicon and gallium arsenide to record a conversion efficiency of 31 percent. The problem is that gallium arsenide is 50 times more expensive than crystalline silicon, and there are still a number of engineering problems.

As the race continues to develop a photovoltaic cells technology which is both efficient and low cost, some very optimistic projections are being made.

Professor Ajeet Rohatgi, a photovoltaics specialist at Georgia Tech, predicts that solar power will be competitive with conventional fuels for large-scale power production sometime soon. According to Byron Stafford, a program manager at SERİ’s Amorphous Silicon Research Project,

“Several companies have projected that large-scale applications, producing megawattage for around 12 cents per kilowatt hour, will be practical soon.” He says that solar technology is now actually quite practical for applications such as the replacement of diesel generators in smals, remote villages which require up to 10 kilowatts of power. Recently, a California manufacturer of solar celis announced plans to build. a $125 million photovoltaics power plant in the desert near Los Angeles, in conjunction with Southern California Edison, When the utility companies start spending that kind of money, it's clear that something important is happening.

Finally, efficient solar cells and improved batteries might be the key to producing practical electric automobiles, thus ridding us of one of the greatest sources of air pollution.

As Stanford Ovshinky, who worked for decades to make solar power a reality, has said, “Ours is an idea whose time has come. Photovoltaics and electric automobiles will become: some of the world’s largest industries, creating new jobs, new business opportunities and a more rapid means of industrialization of the developing nations.” 

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