We may stand guilty of downplaying the future of crystaline photovoltaics. After all, exponential growth is necessary for alternative energy to take over the world, and after all, it is no simple matter to manufacture crystaline photovoltaics. But as amply documented in our post “The Coming Boom in Photovoltaics,” the only thing thing that stops crystaline photovoltaics from experiencing exponential growth is the supply of polysilicon. And the only raw material inputs required to manufacture polysilicon is silicon, one of the most abundant materials on earth, and electricity, which photovoltaics produce in abundance.
Along with crystaline photovoltaic cells, which are made from slices of crystal silicon ingots, there are two relative newcomers; “thin-film” cells that use far less silicon, and concentrators, that use less photovoltaic material (not necessary silicon) but use mirrors, magnifiers, and solar tracking systems to multiply the amount of light, or “suns,” hitting the photovoltaics. There are many ways to evaluate the relative merits of these three fairly distinct technologies that all promise to deliver a product that is commercially competitive to conventional energy.
How much do the systems cost per photovoltaic array – i.e., what are the dollar costs per watt just for the photovoltaic panels? How much do the systems cost per watt once they are installed – including the “balance of plant” such as the inverter, the wiring, the mounting racks, and of course, the costs to have all of this put in place by skilled technicians? In terms of cost per watt, thin film photovoltaics have achieved manufacturing costs as low as $1.30 per watt (First Solar S-1 Statement 2006). In terms of installed costs, systems with high efficiency have advantages, but then again, there are low efficiency thin film systems that can be unrolled onto a roof like a tarp. In such a scenario, installation is cheap.
How much space do the systems take up – what is their efficiency? Concentrator manufacturers claim their prototypes yield up to 40% efficiency, or about 40 watts per square foot (400 watts per square meter). By contrast thin-film efficiencies range between 5% and somewhat higher than 10%. Crystaline photovoltaics can put out a reliable 15% and some of them can do much more.
When longevity of photovoltaics are taken into account, as well as proven reliability, crystaline photovoltaics are the best photovoltaic technology to-date, and possibly forever. There are crystaline systems that are over 20 years old and still have output at over 80% of their original efficiency. Early thin-film designs have not shown similar durability, although that may have changed. Concentrators are not yet installed in sufficient numbers for meaningful data to have emerged on their longevity.
It appears that thin-film photovoltaics may have the best potential to quickly ramp up manufacturing and make photovoltaic energy a significant contributer to global electricity production. After all, thin-film companies like Nanosolar claim to have a 400 megawatt factory under construction, and Miasole has a 25 megawatt line getting fired up right now, with three more on the way. First Solar’s 40 megawatt plant in Ohio has been operational for over a year now, and they are also on track to vastly increase their capacity.
Meanwhile, crystaline photovoltic technology in 2005 was still responsible for 94% of worldwide photovoltaic production, which was 1.5 gigawatts in that year. So why would we write-off the potential of the crystaline photovoltaic industry to explode? After all, worldwide photovoltaic output only five years earlier was only 300 megawatts, all of it crystaline ingots. Quintupling every five years is not bad growth. SunPower, a premier manufacturer of photovoltaics who have prototype cells that achieve well over 20% efficiency, and who claim they can get the price for crystaline photovoltaics under $1.00 per watt, intend to have their manufacturing capacity over 400 megawatts per year by 2008. Don’t write off crystaline photovoltaic technology just yet.
The photovoltaic industry has been capacity constrained at least since 2001, and will remain capacity constrained well into the foreseeable future. They don’t have to be commercially competitive with conventional energy for this industry to increase in output by at least one order of magnitude, if not more. After all, the five gigawatts of installed photovoltaics in the world represents well under 1% of the world’s supply of electricity. For this reason, no matter how you manage to manufacture photovoltaics, if you can do it you will enjoy high gross profits. Crystalline photovoltaics, with a theoretical maximum efficiency of over 40%, and with a demonstrated history of durability and longevity, are not going to go away.