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Updates on Alternative Energy Sources, Part 6: Solar

March 18, 2010


This is the sixth in a series of posts on alternative energy sources using as a starting point an article by Michael Totty [“The Long Road to an Alternative-Energy Future,” Wall Street Journal, 22 February 2010]. Solar Power is the next topic to which Totty turns [“The Long Road: Solar,” Wall Street Journal, 22 February 2010]. Totty writes:

THE TECHNOLOGY: Energy from the sun can be used to make electricity directly with photovoltaic panels or indirectly using concentrated sunlight to heat a liquid, which produces steam to turn electrical turbines. Concentrating solar plants can be built to store heat and deliver power for several hours without sunlight.

CURRENT STATUS: Solar power (both photovoltaic and concentrating) produced an estimated about 3.2 billion kilowatt-hours of electricity in 2009. Total capacity—the amount of power that could be produced if the sun shone constantly—of solar photovoltaic systems has been doubling every two years, and the pace of increase is expected to rise further: An estimated 2,000 megawatts of solar capacity in 2009 was nearly 45% higher than in 2008. That includes about 980 megawatts of concentrating-solar projects; an additional 81 megawatts are under construction.”

For more detailed descriptions about solar power systems and what’s being developed, read my blogs entailed Latest Solar Power Developments, Update on Solar Energy, and Portable Power. Since solar power has been in use for quite some time, you might wonder why Totty believes that a robust solar power sector is a long way off. He explains:

WHY IT’S GOING TO TAKE SO LONG: Even at [the] rate of growth [discussed above], solar power is still minuscule: Solar generation in 2009 accounted for less than 0.1% of total electricity production in the U.S. Solar capacity remains less than 1% of the total. ‘The biggest obstacle is that we’re starting at such a low level,’ says John Benner, a research manager at the National Renewable Energy Laboratory. The cost of solar installations has fallen in recent years, but remains high, partly because demand continues to keep pace with supply. The cost for average residential installations was about $5.40 a watt of capacity in 2008 and $4.20 a watt for commercial, after a raft of federal, state and local incentives, according to a study by the Lawrence Berkeley National Laboratory. (Solar installations depend heavily on subsidies, which vary widely; without incentives, costs average $7.50 a watt.) Thanks to capital expenses, electricity from solar is expensive: Estimates of solar costs cover a broad range, from 25 to 46 cents a kilowatt-hour for residential and from 17 to 29 cents from a concentrating solar plant. That compares with about 7 cents a kilowatt-hour for coal and natural gas and 10 cents for wind, according to estimates by the Electric Power Research Institute. Like wind farms, utility-scale solar photovoltaic and concentrated-solar projects also require additional transmission connections. Since most aim to build in the environmentally sensitive desert Southwest, where much of the land is publicly owned, they also face lengthy and complicated permitting reviews.”

One thing Totty doesn’t mention is that most large concentrating solar power projects also require a lot of water. In many areas where solar farms can find lots of sun there is a scarcity of water. In stand-offs between those needing water to produce electricity and those requiring it to grow food or for personal use, food and drink generally win. Nevertheless, because the sun shines everywhere (more or less) countries around the globe are interested in harnessing the power of the sun [“Potential of the sun dawns on the US,” by Sheila McNulty, Financial Times, 18 August 2009]. McNulty reports:

“Solar panels may not adorn every rooftop but governments globally could finally be giving the industry the fresh impetus needed for it to fulfil its potential. In spite of record growth, rates over the past five years, high costs (solar energy can be four times as expensive as traditional gas-fired electricity) and the economic downturn mean solar has not become a mainstream energy source. While many solar companies were profitable before the economic downturn, boosted by government subsidies, the credit squeeze and fall in energy demand has hit them along with the rest of the power sector. This has led some component prices to drop, which has heaped pressure on margins at many manufacturers. Germany, Japan and Spain lead the market, mainly because their governments took an early lead in pushing the technology’s development and, as a result, the industry is led mostly by European companies. … However, China and the US are making a concerted effort to make up for lost time. China is already the world’s biggest producer of solar panels but exports 90 per cent of the equipment, while many in the industry expect the US to overtake its rivals shortly following increased attention from Washington.”

How quickly is the U.S. making up for lost time? McNulty reports that a “recent report by Pike Research, the clean technology research group, says the US could well lead the solar industry by 2014. It is currently the fourth largest, behind Germany, Spain and Japan.” One reason that solar may catch on is that major utility companies are starting to get involved. The first full-scale experiment merging solar-generated electricity with a traditional fossil fuel-powered plant is taking place in Florida [“The Newest Hybrid Model,” by Jad Mouawad, New York Times, 5 March 2010]. Mouawad reports:

“Across 500 acres north of West Palm Beach, the FPL Group utility is assembling a life-size Erector Set of 190,000 shimmering mirrors and thousands of steel pylons that stretch as far as the eye can see. When it is completed by the end of the year, this vast project will be the world’s second-largest solar plant. But that is not its real novelty. The solar array is being grafted onto the back of the nation’s largest fossil-fuel power plant, fired by natural gas. It is an experiment in whether conventional power generation can be married with renewable power in a way that lowers costs and spares the environment. This project is among a handful of innovative hybrid designs meant to use the sun’s power as an adjunct to coal or gas in producing electricity. While other solar projects already use small gas-fired turbines to provide backup power for cloudy days or at night, this is the first time that a conventional plant is being retrofitted with the latest solar technology on such an industrial scale.”

India is another country that is beginning to embrace solar technologies [“India steps out of shade on solar power,” by Joe Leahy and Varun Sood, Financial Times, 28 September 2009]. Leahy and Sood report:

“India’s Gujarat state is planning to complete the acquisition of thousands of acres of land by the end of this year [2009] for its plan to build the world’s largest solar power complex. The US-based Clinton Foundation will provide support raising financing for the $10bn, 3,000 megawatt project, which if successful will catapult the mercantile western Indian state into the forefront of solar technology. The project underlines how resource-poor India has been galvanised into embracing renewable energy when there is increasing pressure on it to cut its emissions. … The Gujarat cluster will aim to develop a mixture of technologies, from solar panels to solar thermal power plants, which use the sun to heat fluids that drive steam turbines and generate electricity. … Solar power is seen as one of the more promising sources of renewable energy for India, whose demand for electricity is expected to increase fivefold over the next two decades.”

As I’ve stated repeatedly, development requires reliable electrical power. Although solar energy remains costly, it is also reliable (as long as the sun shines) and plants can be located close to where the electricity it produces is going to be used — meaning that the cost of constructing transmission lines can be minimized. I’m sure the Gujarat government is hoping that companies will relocate to places where power supplies are reliable. If the government can eventually provide both reliable and affordable power, all the better. Affordability remains a problem. Spain, which wanted to brand itself as the solar capital of the world, provided generous subsidies to its solar sector which immediately began constructing solar plants. Eventually, however, the Spanish government realized that it “would have to subsidize many of them indefinitely, and that the industry they had created might never produce efficient green energy on its own.” As a result, subsidies were reduced or eliminated and much of Spain’s solar industry collapsed [“Solar Industry Learns Lessons in Spanish Sun,” by Elisabeth Rosenthal, New York Times, 8 March 2010]. Despite setbacks, research on making solar power more affordable continues apace. For example, researchers at the California Institute of Technology are developing a flexible solar panel they believe will be cheaper to manufacture [“Less is more for highly absorbing, flexible, cheaper solar cells,” by Darren Quick, Gizmag, 17 February 2010]. Quick reports:

“Using arrays of long, thin silicon wires embedded in a polymer substrate, a team of researchers at the California Institute of Technology (Caltech) have created a new type of flexible solar cell. Promising enhanced sunlight absorption and efficient conversion of photons into electrons, the new solar cell uses only a fraction of the expensive semiconductor materials required by conventional solar cells, and because they are flexible, they will be cheaper to manufacture. Independently each silicon wire is a high efficiency, high quality solar cell. By bringing them together in an array the researchers were able to make them even more effective, because they interact to increase the cell’s ability to absorb light. So much so that the new solar cells have surpassed the conventional light-trapping limit for absorbing materials, which refers to how much sunlight it is able to absorb. The silicon-wire arrays absorb up to 96 percent of incident sunlight at a single wavelength and 85 percent of total collectible sunlight.”

Quick explains that impressive light absorption properties don’t always translate into great power generation properties. He continues:

“Harry Atwater, Howard Hughes Professor, professor of applied physics and materials science, and director of Caltech’s Resnick Institute, points out, ‘Many materials can absorb light quite well but not generate electricity – like, for instance, black paint. What’s most important in a solar cell is whether that absorption leads to the creation of charge carriers.’ The silicon wire arrays created by Atwater and his colleagues are able to convert between 90 and 100 percent of the photons they absorb into electrons—in technical terms, the wires have a near-perfect internal quantum efficiency. ‘High absorption plus good conversion makes for a high-quality solar cell,’ says Atwater. These conversion rates are surprising given that the wires cover only between two and 10 percent of the cell’s surface area. When light comes into each wire, a portion is absorbed and another portion scatters. According to Atwater it is the collective scattering interactions between the wires that make the array very absorbing despite the sparseness of the wires.”

The team has apparently achieved breakthrough effectiveness with their cell; but they also believe they have achieved a breakthrough in affordability as well.

“Since the silicon material is an expensive component of a conventional solar cell, a cell that requires just one-fiftieth of the amount of this semiconductor will be much cheaper to produce. The composite nature of the solar cells means that they are also flexible, meaning they could be manufactured in a roll-to-roll process. As this is an inherently lower-cost process than one that involves brittle wafers, like those used to make conventional solar cells, costs can be further reduced.”

Sound too good to be true? Quick says the team has not reached all of their goals yet. Team members don’t know if the solar cell is scalable — but they are optimistic.

“The next steps, Atwater says, are to increase the operating voltage and the overall size of the solar cell. ‘The structures we’ve made are square centimeters in size,’ he explains. ‘We’re now scaling up to make cells that will be hundreds of square centimeters—the size of a normal cell.’ Atwater says that the team is already ‘on its way’ to showing that large-area cells work just as well as these smaller versions.”

In another article, Quick reports that an Australian team has combined currently available technology in a new way to produce increased efficiency [“Solar panels made three times cheaper and four times more efficient,” Gizmag, 14 March 2010]. He explains:

“Scientists are using current technology in a new type of concentrating array which they say is four times more efficient and three times cheaper than current solar cells. The technology was originally developed at the Royal Melbourne Institute of Technology (RMIT) and will be commercially produced by a spinoff company called Technique Solar. Each solar module consists of nine ‘troughs’ that feature a concentrating acrylic lens and reflective walls to focus the sun’s rays onto a strip of photovoltaic (PV) cells, which enables the number of PV cells to be cut by 75 percent. The PV cells are used to generate electricity, while a heat exchanger located under them is used to generate heat for circulating water and storage tanks for a hot water system. Additionally, to maximize the sun’s rays the array has a motor drive mechanism with tracking sensor to follow the sun. The company says its Concentrated Universal Energy Solar System (CUESS) makes it possible to deliver solar energy more economically and more efficiently than other current forms of solar energy generation. … Technique Solar says its panels can supply heat load (hot water) and electrical energy at one quarter of the energy costs of conventional solar energy systems. It must be highlighted however that these figures refer to total energy output – which combines both the electrical and heat power – not just electrical output, as is the case with standard solar cells. … Technique Solar doesn’t plan to sell its system as an off the shelf purchase to consumers. Rather it intends the modules to be rolled out as infrastructure complementing existing energy supplies from the grid. The modules will be owned/leased by a Power Utility (or in some instances/countries by local councils, government or large corporations) who will then arrange for installation onto residential, commercial, industrial as well as school premises to complement or substitute existing energy supply.”

Most discussions about solar power technologies are focused on large arrays that can produce enough electrical power to compete with fossil fuel-fired power plants. However, there is also research aimed at producing very minute amounts of solar power [“Gold nanoparticles turn light into electrical current,” by Dario Borghino, Gizmag, 22 February 2010]. Borghino reports:

“Turning sunlight into electrical power is all but a new problem, but recent advancements made by researchers at the University of Pennsylvania have given a new twist to the subject. While not currently aimed at solar panel technology, their research has uncovered a way to turn optical radiation into electrical current that could lead to self-powering molecular circuits and efficient data storage. Professor of materials science Dawn Bonnell and colleagues placed light-sensitive gold nanoparticles on a glass substrate, minimizing the distance between the nanoparticles. The team then stimulated conductive electrons with optical radiation to ride the surface of the gold nanoparticles, creating so-called ‘surface plasmons’ that induce electrical current across molecules. Under these conditions, surface plasmons were found to increase the efficiency of current production by a factor of four to 20. The size, shape and separation of the array of golden nanoparticles can be customized independently of the optical characteristics of the molecule, and optimization of these parameters could, the researchers say, produce enhancement factors of thousands, and the resulting electrical current could be easily transported to the outside world.”

Great! So what can you do with such small amounts of power? Borghino explains:

“The results may lead to better nano-sized circuits that can power themselves, potentially through sunlight. Another interesting application suggested by the researchers could be for data storage, where a photovoltaic circuit could encode bits using wavelengths of light rather than electrical charge.”

One final use of solar power I would like to mention before closing is a hybrid system being developed by Honda. I call it a hybrid system because it involves both solar power and hydrogen fuel cells [“Honda’s next gen solar-powered hydrogen fuel cell station for home use,” by Jeff Salton, Gizmag, 1 February 2010]. Salton reports:

“Honda has begun work on a smaller solar hydrogen station prototype intended for use as a home refueling appliance. Capable of an overnight refill of fuel cell electric vehicles it is designed to be a single, integrated unit that will fit in the user’s garage. Honda’s next generation Solar Hydrogen Station, though not as big as the previous systems, will still produce enough hydrogen (0.5kg) via an eight-hour overnight fill for daily commuting (10,000 miles per year) for a fuel cell electric vehicle. … Designed to work in conjunction with Honda’s FCX Clarity vehicle, the charging station is also compatible with a ‘Smart Grid’ energy system. Honda says its Solar Hydrogen Station would enable users to refill their vehicle overnight without the requirement of hydrogen storage, which would lower CO2 emissions by using less expensive off-peak electrical power. Honda says that during daytime peak power times, the Solar Hydrogen Station can export renewable electricity to the grid, providing a cost benefit to the customer, while remaining energy neutral.”

Interestingly, hydrogen power is not one of the alternative energy sources addressed by Totty. I discuss hydrogen power again in the concluding post of this series. Returning to solar power, I believe that it will eventually play an important role in supporting the global economy. This will be particularly true in the developing world where expensive transmission lines and grid systems are unlikely to be installed for the foreseeable future. Currently, the long pole in the tent is cost. Eventually, affordable systems designed for the developing world will be manufactured. When they are, they will be a great boon to the impoverished populations they will serve.

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