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stormsewer[Edited to correct errors, and add a link to the presentation.]
Last Thursday I went to a talk given by Ryne P. Raffaelle of the Rochester Institute of Technology, entitled "The Past, Present, and Future of Photovoltaics." Dr. Raffaelle is the former director of the National Center for Photovoltaics at the National Renewable Energy Lab, and the talk was given as part of the University of Texas Energy Symposium. The original presentation can be found here for the time being. The following is a write-up of my notes.
The history of photovoltaics begins in 1839, when Becquerel discovered the photovoltaic effect (basically the observation that some materials will generate a voltage when exposed to electromagnetic waves, like sunlight). A Frenchman named Mouchot, who was active from 1860 to 1881, was the first to make a solar-powered engine, which ran a refrigerator. He got a lot of funding from the government, because they were dependent on British coal for energy, and the British were gouging them on prices, so they were looking for alternative sources of energy. (Sound familiar?) But then they worked out a deal, the price of coal dropped, and Mouchot lost all his funding. (Sound familiar?)
In 1873, Willoughby Smith discovered the photoconductivity of selenium. In 1883, Charles Fritts put a layer of gold on it, which is sometimes credited with being the first solar cell.
In 1931, there is a somewhat apocryphal quote from Thomas Edison: "We are like tenant farmers chopping down the fence around our house for fuel when we should be using Nature's inexhaustible sources of energy — sun, wind and tide. ... I'd put my money on the sun and solar energy. What a source of power! I hope we don't have to wait until oil and coal run out before we tackle that."
The solar constant, the amount of sunlight energy reaching the Earth, is about 1.361 kW/m2. There is enough power in one hour of sunlight to power human activity for a year. About 89 petawatts is constantly hitting the Earth's surface; humans use about 20 terawatts of power per hour.
In 1940, Russell Ohl invented the p-n silicon junction, and in 1941 patented a photovoltaic cell that employed it. In 1954, Bell Labs patented the first modern solar cell. Solar cell efficiencies have been increasing about 4% a year for the last 30 years.
If not for the space industry, we might not have a solar industry today. One of the first US satellites, Vanguard 1, launched in 1958, was powered by photovoltaic cells. (Sputnik was battery-powered and died after 22 days; contact was maintained with Vanguard 1 for six years). 1962 saw the first corporate satellite, Telstar. Most satellites from then onward have used solar cells for power. As of the 2009, the International Space Station had 2500 square meters of solar cells.
In 1977, Jimmy Carter initiated the Solar Energy Research Institute (SERI) in response to the oil embargo. By the time Reagan came to office, things had gotten better, and he wanted to cut the program entirely (he did, apparently, uninstall the solar cells that Carter had installed on the White House), but apparently a delegation of Colorado businessmen led by Joseph Coors convinced him not to. In 1991, the name was changed to the National Renewable Energy Laboratory (NREL).
Solar really began to take off in the early nineties. More than 30% efficiency was achieved in 1994. In 1991, 50 megawatts of power was produced from solar cells. In 1997, it was 100 megawatts, and in 2010 it was 10 gigawatts.
The National Center for Photovoltaics was formed at NREL in 1996 to be an independent judge of photovoltaic performance. Their graph of cell efficiencies is the most requested piece of information at NREL.
III-V cells (multijunction photovoltaic cells) have the highest efficiency, and if used with solar concentrators can get efficiencies over 40% (though that then causes them to heat up, which reduces efficiency). They are really expensive- they are cost-effective for putting on satellites or maybe on giant arrays out in the desert, but not for putting on your house.
There have been really phenomenal advances in solar technology in the last 30 years, and it has been estimated that without the investment of the US government, it would cost 66% more today than it does. The US has the best solar-power resources of any industrialized nation, but unfortunately we also have a well-established energy grid that is not designed for it, as well as some of the lowest energy costs in the world. Incidentally, in 2009, world energy consumption decreased for the first time in the modern era, though in 2010 it was on the rise again.
Types of photovoltaics that are commercially available have increased in efficiency very little in the last ten years, probably because they are more focused on lowering manufacturing costs than on increasing efficiency. Photovoltaic production has been growing at 50% a year for the last ten years, and some economists predict it will be the largest market in the world. Keep in mind that 50% of the world's population is still using wood burning as its primary source of energy. Reliable and affordable electricity could do a lot to make the world a better place.
Worldwide photovoltaic production actually grew by 100% in 2010. He said that the cost of photovoltaics has been "in free-fall," as well. A lot of people will say that solar cells are too expensive to be practical, and cite data from 2008 to back it up, but the data on cost from 2008 is already very outdated. Efficiency has been going up, the scale of production has been going up, and the amount of competition between solar energy companies has been going up, all of which puts downward pressure on prices.
In 2009, photovoltaics began consuming more silicon than microelectronics for the first time. The price of silicon went way up at the time, and First Solar, which uses cadmium-telluride instead of silicon, became the biggest solar power company in the world (though it's not now).
Last year, China invested more in photovoltaics than the rest of the world combined. The US is finally starting to wake up to solar, but currently 80% of photovoltaic production is in Asia, and 80% of deployment is in Europe, though the raw materials often come from the US. At the moment, solar pays itself off within ten years only in a few states (like California and New York) with relatively high sunlight and high energy costs. The goal is to get the cost down to $1 per watt (it's about $5 per watt now), at which point an investment in solar would pay itself off within ten years almost everywhere in the country. Right now the standard is a 25-year warranty that the solar cells will operate at least 80% of their rated capacity. Performance typically degrades about 1% a year. Though you save money over the long-term, the upfront costs are significant, and thus only people with money to burn can afford them. Fifty percent of the cost of installing solar cells is in soft costs like installation and permitting; if those could be lowered, it would be much more economical.
In the future it is unlikely that one type of solar cell will dominate all the others. The type of solar cell used will depend on where it is to be used and how much money the purchaser is willing to spend on it upfront.
Last Thursday I went to a talk given by Ryne P. Raffaelle of the Rochester Institute of Technology, entitled "The Past, Present, and Future of Photovoltaics." Dr. Raffaelle is the former director of the National Center for Photovoltaics at the National Renewable Energy Lab, and the talk was given as part of the University of Texas Energy Symposium. The original presentation can be found here for the time being. The following is a write-up of my notes.
The history of photovoltaics begins in 1839, when Becquerel discovered the photovoltaic effect (basically the observation that some materials will generate a voltage when exposed to electromagnetic waves, like sunlight). A Frenchman named Mouchot, who was active from 1860 to 1881, was the first to make a solar-powered engine, which ran a refrigerator. He got a lot of funding from the government, because they were dependent on British coal for energy, and the British were gouging them on prices, so they were looking for alternative sources of energy. (Sound familiar?) But then they worked out a deal, the price of coal dropped, and Mouchot lost all his funding. (Sound familiar?)
In 1873, Willoughby Smith discovered the photoconductivity of selenium. In 1883, Charles Fritts put a layer of gold on it, which is sometimes credited with being the first solar cell.
In 1931, there is a somewhat apocryphal quote from Thomas Edison: "We are like tenant farmers chopping down the fence around our house for fuel when we should be using Nature's inexhaustible sources of energy — sun, wind and tide. ... I'd put my money on the sun and solar energy. What a source of power! I hope we don't have to wait until oil and coal run out before we tackle that."
The solar constant, the amount of sunlight energy reaching the Earth, is about 1.361 kW/m2. There is enough power in one hour of sunlight to power human activity for a year. About 89 petawatts is constantly hitting the Earth's surface; humans use about 20 terawatts of power per hour.
In 1940, Russell Ohl invented the p-n silicon junction, and in 1941 patented a photovoltaic cell that employed it. In 1954, Bell Labs patented the first modern solar cell. Solar cell efficiencies have been increasing about 4% a year for the last 30 years.
If not for the space industry, we might not have a solar industry today. One of the first US satellites, Vanguard 1, launched in 1958, was powered by photovoltaic cells. (Sputnik was battery-powered and died after 22 days; contact was maintained with Vanguard 1 for six years). 1962 saw the first corporate satellite, Telstar. Most satellites from then onward have used solar cells for power. As of the 2009, the International Space Station had 2500 square meters of solar cells.
In 1977, Jimmy Carter initiated the Solar Energy Research Institute (SERI) in response to the oil embargo. By the time Reagan came to office, things had gotten better, and he wanted to cut the program entirely (he did, apparently, uninstall the solar cells that Carter had installed on the White House), but apparently a delegation of Colorado businessmen led by Joseph Coors convinced him not to. In 1991, the name was changed to the National Renewable Energy Laboratory (NREL).
Solar really began to take off in the early nineties. More than 30% efficiency was achieved in 1994. In 1991, 50 megawatts of power was produced from solar cells. In 1997, it was 100 megawatts, and in 2010 it was 10 gigawatts.
The National Center for Photovoltaics was formed at NREL in 1996 to be an independent judge of photovoltaic performance. Their graph of cell efficiencies is the most requested piece of information at NREL.
III-V cells (multijunction photovoltaic cells) have the highest efficiency, and if used with solar concentrators can get efficiencies over 40% (though that then causes them to heat up, which reduces efficiency). They are really expensive- they are cost-effective for putting on satellites or maybe on giant arrays out in the desert, but not for putting on your house.
There have been really phenomenal advances in solar technology in the last 30 years, and it has been estimated that without the investment of the US government, it would cost 66% more today than it does. The US has the best solar-power resources of any industrialized nation, but unfortunately we also have a well-established energy grid that is not designed for it, as well as some of the lowest energy costs in the world. Incidentally, in 2009, world energy consumption decreased for the first time in the modern era, though in 2010 it was on the rise again.
Types of photovoltaics that are commercially available have increased in efficiency very little in the last ten years, probably because they are more focused on lowering manufacturing costs than on increasing efficiency. Photovoltaic production has been growing at 50% a year for the last ten years, and some economists predict it will be the largest market in the world. Keep in mind that 50% of the world's population is still using wood burning as its primary source of energy. Reliable and affordable electricity could do a lot to make the world a better place.
Worldwide photovoltaic production actually grew by 100% in 2010. He said that the cost of photovoltaics has been "in free-fall," as well. A lot of people will say that solar cells are too expensive to be practical, and cite data from 2008 to back it up, but the data on cost from 2008 is already very outdated. Efficiency has been going up, the scale of production has been going up, and the amount of competition between solar energy companies has been going up, all of which puts downward pressure on prices.
In 2009, photovoltaics began consuming more silicon than microelectronics for the first time. The price of silicon went way up at the time, and First Solar, which uses cadmium-telluride instead of silicon, became the biggest solar power company in the world (though it's not now).
Last year, China invested more in photovoltaics than the rest of the world combined. The US is finally starting to wake up to solar, but currently 80% of photovoltaic production is in Asia, and 80% of deployment is in Europe, though the raw materials often come from the US. At the moment, solar pays itself off within ten years only in a few states (like California and New York) with relatively high sunlight and high energy costs. The goal is to get the cost down to $1 per watt (it's about $5 per watt now), at which point an investment in solar would pay itself off within ten years almost everywhere in the country. Right now the standard is a 25-year warranty that the solar cells will operate at least 80% of their rated capacity. Performance typically degrades about 1% a year. Though you save money over the long-term, the upfront costs are significant, and thus only people with money to burn can afford them. Fifty percent of the cost of installing solar cells is in soft costs like installation and permitting; if those could be lowered, it would be much more economical.
In the future it is unlikely that one type of solar cell will dominate all the others. The type of solar cell used will depend on where it is to be used and how much money the purchaser is willing to spend on it upfront.
