Renewable Energy and Politics: A Tale of Two Technologies
By Lubab Sheet, senior director emerging technologies, SEMI
The role of politics in renewable energy is significant. While government tariffs and subsidies have sparked hockey stick growth in photovoltaic, government policies are hindering fuel cell progress.
Renewable energy accounts for less than 1 percent of the world’s energy demand currently, with solar thermal as the largest segment. Photovoltaic (PV), or solar electricity, is currently the fastest growing segment, followed by wind energy. Solar thermal devices use direct heat from the sun, concentrating it, to produce heat at useful temperatures and are used to heat water and in architecture and building design to control heating and ventilation. Photovoltaics convert energy from the sun into electricity and are used for residential electricity as well as for electricity plants or solar farms.
Government tariffs and subsidies have been critical to “hockey stick growth in PV” and help the industry cut costs through increased volume and innovation. In Japan today, price parity essentially exists for solar compared to traditional (peak) electricity sources, but GT Solar believes it is another 6–8 years away in Europe and 8–10 years away in the U.S. Therefore, further subsidies and policies are required to help bridge the gap and encourage increased demand for solar electricity.
A solar cell produces about a half volt of power, and the price of electricity generated depends on the amount of sun light: $0.40–0.25 per kilowatt hour for 4–6 hours per day of sun (New England versus California for example). According to GT Solar, 94 percent of the PV market is silicon based; multi-crystalline dominates and the balance is thin-film, including about half of this being silicon based such as ribbon silicon, amorphous, and others. “Silicon technology is proven; there is a long way to go to prove thin-film.”
Several processes developed for semiconductor manufacturing can be leveraged in the solar industry, though wafer volumes for PV are several orders of magnitude higher and the value of solar “wafers” are substantially lower than semiconductors. Wet etching is used for texturing surfaces; a variety of methods including CVD; sputtering and screen printing are used for depositing anti-reflective coatings and electrodes; tube furnaces—which are largely horizontal—for doping, annealing and curing steps; lasers for forming junctions; and wet processing stations for cleaning. Cell testing/sorting is typically highly automated, as is putting cells together (stringing) in an array or module. There are a also a variety of inspection requirements. Ion implantation is one process, even with cluster implant, that is not used. “It is too expensive and does not have the necessary throughput,” according to GT Solar.
Silicon is the biggest single cost of the solar modules—with materials representing about 70 percent of the module cost. Metallurgical grade silicon, at about $1 per kilogram, is converted to solar grade polysilicon. It sells currently for $300 per kilogram, with the longer term price of $60–$70 per kilogram. It takes two days to grow a 260–270 kilogram ingot, with development to increase this to 450 kg ingots, which is then sliced up into 156 mm2 wafers, each about 220 μm thick (down from 300 μm a few years ago, and will likely be reduced to 200 μm or less in a year or so). So, not only are the ingots getting bigger, but wafers are getting thinner in order to improve productivity and lower costs.
A fuel cell is an energy conversion device based on electrochemistry, not combustion; and as a result is very quiet. There are many types of fuel cells with alkaline based cells used in each space shuttle mission to produce heat, electricity and the water the astronauts use. Proton exchange membrane (PEM) fuel cells are the focus of many development efforts as they can be made large or small. They are portable and operate at near room temperature. However, they can be costly as they currently require a platinum catalyst to operate. There is certainly opportunity for innovation in identifying alternative catalyst materials that are less expensive as well as electrolyzers. The PEM fuel cell is made up of a bipolar plate-membrane-bipolar plate-membrane sandwich structure. Hydrogen gas or methanol is the input material for the fuel cell and drinking water is the output. Fuel cells operate using DC power and often have to be converted to AC power. Hydrogen storage is another area requiring further innovation, and is a Department of Energy (DOE) grand challenge. The key benefits of fuel cells are green technology and no re-charge time. “Wouldn’t it be nice not to have to search for an electrical outlet to re-charge all of your electronic gadgets?”
Hydrogen is not a fuel, but an energy carrier, so it is re-usable and very abundant. It is very efficient with no emissions. However, hydrogen has a major public perception issue: it explodes. While the Hindenburg explosion was a result of the aluminum coating not hydrogen, the public believes hydrogen poses a major fire risk. In 1910, it was illegal to park a car in an enclosed garage because similar concerns existed for gasoline. With time, this perception issue can be resolved. In the meantime, fuel cell advocates are trying to pass legislation to allow small canisters of methanol onto airplanes to charge fuel cell laptops, etc. They were close, and then the restrictions on carrying fluids onto airplanes emerged, setting efforts back quite substantially. Entegris argued that duty-free perfumes and alcohol from beverage carts offer a far greater fire hazard concern than canisters of methanol for fuel cells, which have an advanced canister design to prevent fires, but politicians have had a change of heart and are not likely to pass legislation allowing methanol on planes.
Early adopters of fuel cells are portable power generators (back-up supplies) as well as the military. A Special Forces soldier currently has to carry 15 pounds of batteries to charge equipment. Fuel cells would not only reduce this weight, but also allow an increase in the length of missions. Fuel cells also afford a single or ubiquitous power source.
Another commercial application today is Winnebagos. Hymer and Smart Power have teamed up to provide fuel cell generators for Winnebagos. Customers don’t want to turn on a smelly and loud diesel generator when they get to the camp site or RV park. Another application is yachts for similar reasons. Farm equipment is one of the first transportation applications, followed by busses. Honda is targeting 2018 for commercial volumes of fuel cell vehicles. Entegris thinks there will be a gradual, incremental transition to fuel cell cars, and does not view hybrid cars as a threat, but rather one-step along this transition.
A few technical hurdles remain, in addition to political ones, for portable fuel cells used for electronics, including system miniaturization and packaging. Specifically with regard to miniaturization, small valves and delivery systems remain technical issues, along with heat dissipation. MEMS may offer a solution.
All of the information contained in this article was derived from content presented at the SEMI New England Breakfast Forum, March 7, 2007 in Billerica, Massachusetts. If you have questions or comments, feel free to contact Lubab Sheet at Lsheet@semi.org or 1.408.943.6921.