As the window of our past takes us to our future, we must take a look back into the history of solar power. Conversion of solar energy into electricity originated with solar panels, also referred to as photovoltaic cells, and paralleled advances in the semiconductor industry. Meanwhile, solar heat took a different path.
While based on old technology, thermal power only surfaced after solar panels were well on their way to public acceptance. Solar panels and thermal power are served up from the same caldron of solar energy.
The first photovoltaic solar cell was made in 1883 by American Charles Fritts. He coated a semiconductor metal (e.g., selenium) with a thin coating of gold to join the “cells.” As the first solar cell, it was no more than 1 percent efficient. But it was a start!
The early 1900s was a time for discovery and speculation. In 1908, William J. Bailley invented a solar collector with copper coils and an insulated box—a rough semblance of present photovoltaic designs. In 1921, Albert Einstein won the Nobel Prize for his theories explaining the photoelectric effect.
In the 1950s, American ingenuity gave birth to the first solar cells. Bell Laboratories had produced a silicon solar cell with a solar to electricity conversion efficiency  of 4 percent. They were now ready for the big-time.
- In 1956, photovoltaic cell development was proposed for orbiting satellites.
- In 1958, Hoffman Electronics achieved a solar panel efficiency of 9 percent.
- In 1958, Vanguard 1 space satellite was fitted with a small array (less than 1 watt) to power its radios. The solar cells powered the satellite until 1964 when the system was shut down.
- In 1959, Hoffman Electronics achieved a solar panel efficiency of 10 percent.
- In 1959, Explorer VI was launched with an array of 9600 cells—each cell was less than ½ square inch in size.
Although solar cells had been a smashing success in outer space, there were problems yet to be overcome under the veil of Earth’s atmosphere. At less than 10 percent efficiency, and a price tag of about $100 per Watt of energy, the earlier solar cells were unattainable for the Earth bound minions.
The 1960s touted continued progress in space systems and minimal within the earth’s atmosphere. Improvements and applications remained slow.
- In 1959, Hoffman Electronics achieved a solar panel efficiency of 14 percent.
- In 1962, Bell Telephone launches the first telecommunications satellite with an initial solar power of 14 watts—less than a light bulb.
- In 1963, Japan introduced the first Earth bound photovoltaic array—a 242 watt lighthouse.
- In 1965, NASA launched the first orbiting astronomical observatory supported by 1,000 watts of solar power.
In the 1970s, interest in inner space solar power was renewed. The brief “oil crisis” sparked interest in alternatives energy sources. The Soviets developed of a “more efficient” semiconductor material (i.e., gallium arsenide), and Americans designed a significantly less costly solar cell. Efficiency had doubled to about 14 percent, and cost had been reduced to about $20 per Watt. The world was enchanted!
- In 1972, the French installed a photovoltaic system to operate an educational television in a village school.
- In 1976, the NASA Lewis Research Center installed and tested eighty-three solar power systems around the world for remote applications such as water pumping, grain milling, indoor lighting, vaccine refrigeration, and televisions.
- In 1977, the U.S. Department of Energy launched the Solar Energy Research Institute.
- In 1978, the NASA Lewis Research Center installed the world’s first village photovoltaic system on an Indian reservation in Arizona.
Also, during the 1970s, as the oil crisis devolved, other forms of solar power evolved commercially. Solar cells found a home in small utilitarian items (e.g., calculators and watches) and low-power remote items (e.g., solar-powered outdoor lights and gate openers). These scaled down, niche items were not only affordable but practical and easily attainable. They became popular overnight, and entrepreneurs were encouraged.
In the 1980s, the Happy Days of Solar Gimmicks gave greater publicity to the solar energy concept, and production catapulted to electrifyingly new highs. It went from a total of 500 kWatts in 1977 to 21.3 MWatts (e.g., 21,300 kWatts) in 1983.
- In 1980, the first thin-film solar cell, exceeding 10 percent efficiency, was developed using copper sulfide/cadmium sulfide.
- In 1981, Solar Challenger, the first solar-powered aircraft, flies from France to England with 16,000 solar cells mounted on its wings with 3,000 watts of power.
- In 1982, ARCO Solar built the first photovoltaic power plant went on-line in Hisperia, California with 108 dual-axis tracking modules and a power capacity of 1 MW which could supply about 300 homes. Volkswagen of Germany began testing photovoltaic arrays mounted on the roofs of Dasher station wagons, and their sole purpose was for the ignition system—much ado about very little. Quiet Achiever, the first solar-powered car was race in Autrailia—driving 2,485 miles with a maximum speed of 45 mph, averaging 15 mph.
- In 1983, a 4 kWatt solar-powered home is completed in Hudson River Valley, New York. This is sufficient, during peak daylight hours, to power: (1) an iron and dish washer; (2) a range, refrigerator, and microwave; or (3) a clothes drier.
- In 1986, ARCO Solar introduced the first commercial thin film photovoltaic module.
- In 1988, Applied Solar Energy Corporation began manufacturing the first residential solar panels with an efficiency of 17 percent—a little over half the efficiency that is available for residential use today.
Since the 1990s, researchers have been attempting to increase photovoltaic cell efficiency and reduce costs.
- In 1992, the University of South Florida developed a 15.7 percent efficient thin-film photovoltaic cell of cadmium telluride.
- In 1994, the U.S. National Renewable Energy Laboratory achieved a solar panel efficiency in excess of 30 percent made of gallium arsenide.
- In 1999, Spetrolab and the U.S. National Renewable Energy Laboratory achieves a 32.3 percent efficiency by combining three layers of photovoltaic materials into one single solar cell and concentrating the sunlight with lenses and/or mirrors that are mounted on a solar tracking system—not residential friendly. And the U.S. National Renewable Energy Laboratory achieved 18.8 percent efficiency for thin-film photovoltaic solar panels.
Laboratory findings and practical applications are not one-and-the-same. All efforts to increase efficiencies and reduce cost have run up against a brick wall. Research projected efficiencies could not be duplicated in the real world, and manufacturing is extremely expensive. A few of the efforts to reproduce some of the recent advances and keep the price down have ended in bankruptcy.
Strolling into the new millenium, photovoltaic cell efficiency has not improved. Today’s heavy, glass panels attain an efficiency of 18 percent, and the thin-film panels attain a maximum efficiency of 9 percent. You might ask, “Why the discrepancy between efficiencies reported in press and promotional announcement and the efficiencies reported by the manufacturers?” Once again, the devil is in the details. While the manufacturers rate panel efficiency by Standard Testing Conditions, the media uses “maximum efficiency” that is based on perfect, unattainable conditions. An example of perfect, unattainable conditions is placement of solar panels in a cold environment, on the Equator, clear skies (e.g., no rain), and low humidity (e.g., desert) in the spring and/or fall. Each of these factors affects energy conversion efficiency. The perfect world does not exist!
Since the 1950s, the price of solar panels has come down considerably. Yet, they are still expensive. The heavy glass panels seem to be hovering around $5-8 per watt, and the light weight “thin film” solar panels about half the price of the heavy panels with a required doubling of the area covered. In other words, if the area of coverage is limited, “thin film” is not feasible.*
Also, at the turn of the century, political pressure by the European Union has led to a frantic scramble for European countries to build renewable electricity facilities, or they will suffer severe financial penalties. The pressure is for each country to have 20 percent renewable energy by the year 2020. For this reason, photovoltaic power plants are being built and brought on-line where few other resources are available while solar energy is within the realm of possibilities. The first worldwide photovoltaic plant was built in Germany in 2003. Shortly thereafter, Spain started installing plants and has since become the largest provider of photovoltaic power facilities in the world, and they have the largest capacity facility in the world at 60 MW.** Other European countries who have bought into large scale photovoltaic power include Germany and Portugal. In the United States, there is a 25 MW photovoltaic plant in Florida and a 21 MW plant under construction in California.[i]
The stealth dream arises as some researchers claim they can get solar panel efficiencies up to 42.8 percent. These claims are based upon artificially concentrating solar energy, not on advancements in the semiconductor industry. Concentrating solar energy on solar panels would likely require focused, tracking mirrors and a cooling system—a very costly approach with minimal gain.[iii]
* Contractors are competitive, and residential pricing is highly variable. Costs were excerpted from internet web sites for comparison only. And the less efficient a panel, the greater surface area needed to collect solar energy. Whereas heavy photovoltaic panels are 1.7 times more efficient than thin film solar cells, a 1,000 square feet surface coverage for the heavier units would have to be extended to 1,700 square feet for the thin film cells.
** Solar power capacity is based upon maximum output when the sunlight is at its peak. Actual electricity production is different from capacity, and it differs by geographic location, terrain, atmospheric conditions, and season. Spain, a portion of Italy, and Greece are the only countries in European Union that receive a moderate amount of sun. The rated capacity for the Olmedilla Photovoltaic Park in Spain is 0.16. This means that the annual production of the largest facility in Europe produces only 16 percent of the 60 MW capacity in one year.[ii] In other words, the plant will produce an average of 9.6 MWh, not the 60 MW peak power the facility could produce IF the sun was directly overhead, the skies clear, and atmosphere unpolluted all the time. This, of course, is impossible.
[i]Lenardic, Denis: Large-scale photovoltaic power plants ranking 1-50. (updated: 29 Nov 2009) at http://www.pvresources.com/en/top50-pv.php
[ii] Wikipedia: Photovoltaics. en.wikipedia.org/wiki/Photovoltaics