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The Current State of Green Energy Technologies

March 11, 2009


In a previous post [The Future of Energy], I indicated that in a later post I would discuss some of the breakthrough technologies that made The Economist feel optimistic about the future of power generation. In a special report on energy published last June, the magazine looked at developments in wind power, solar energy, geothermal energy, and other technologies that it believes will make the future both greener and brighter. Let’s begin with what the magazine had to say about wind power [“Trade Winds“]. The article begins with an apt reference to Don Quixote, whose famous windmills still stand on a ridge in Castile-La Mancha but are now “dwarfed by legions of modern wind turbines that grind out not flour but power.”

“Wind power is no illusion. World capacity is growing at 30% a year and will exceed 100 gigawatts [in 2008]. Victor Abate, General Electric’s vice-president of renewables, is so convinced that by 2012 half of the new generating capacity built in America will be wind-powered that he is basing his business plan on that assumption. Wind currently provides only about 1% of America’s electricity, but by 2020 that figure may have risen to 15%. The one part of the United States that has something approximating a proper free market in electricity, Texas, is also keener than any other state on deploying the turbines. In May [2008], T. Boone Pickens, one of the state’s most famous oil tycoons, announced a deal with GE to build a one-gigawatt wind farm—the world’s largest—at a cost of $2 billion.”

Not everyone is thrilled about the construction of gigantic wind turbine towers in their neighborhood. Perhaps most famous were the objections by residents of Nantucket about plans to build an ocean-based wind farm off their scenic shoreline. In addition to complaints about the unsightliness of wind turbines or the noise they make, there are cries that turbines kill birds. Proponents counter that many more birds are killed annually by cats, vehicles and buildings. Despite the protests, The Economist asserts that wind power is here to stay.

“What was once a greener-than-thou toy has … become a real business (GE alone expects to sell $6 billion-worth of turbines [in 2008])—and one with many advantages. For example, as Lester Brown, the president of the Earth Policy Institute, a think-tank in Washington, DC, points out, a farmer in Iowa who gives up a tenth of a hectare (a quarter of an acre) of land to a turbine might earn $10,000 a year from it (about 3% of the value of the electricity it produces). Planted with maize, the same land would yield a mere $300-worth of bioethanol. Moreover, wind farms can be built piecemeal, unlike most power stations. A half-finished coal-fired or nuclear power plant is a useless waste of money, but a half-finished wind farm is simply a wind farm half the size originally intended—and one that has been providing revenue since the first turbine was completed.”

The Economist notes that great strides have been in wind power technologies which have increased turbine reliability and decreased costs.

“One consequence of this rapidly growing market is a virtuous circle of technological improvement that is pushing wind-generated electricity closer and closer to solving Google’s cheaper-than-coal equation. The first turbines were cobbled together from components intended for ships. Now the engineers are borrowing from aircraft design, using sophisticated composite materials and equally sophisticated variable-geometry blades to make those blades as long as possible (bigger is better with turbine technology) and as smart as possible (a blade that can flex when the wind blows too strongly, and thus “spill” part of that wind, is able to turn when other, lesser turbines would have to be shut down for their own safety). The theoretical maximum efficiency of a turbine, worked out in the early 20th century by Albert Betz, is 59.3%. Modern turbines get surprisingly close to that, being about 50% efficient. They are also more reliable than their predecessors. According to Mr Abate, when GE entered the turbine business in 2002 the average turbine was out of commission 15% of the time. Now its downtime is less than 3%. As a result, the cost of the energy cranked out by these turbines has come down to about 8 cents a kilowatt-hour (kWh) and is still falling. That makes wind power competitive with electricity generated by burning natural gas. Coal power is still cheaper, at about 5 cents a kWh. But according to a study by the Massachusetts Institute of Technology (MIT), that would rise to 8 cents if the CO2 from coal-fired power stations had to be captured and stored underground—or, for that matter, if a carbon tax of $30 a ton were imposed.”

Not only are wind farms scalable, but the cost of the natural resource that powers them is free — that is, if the wind blows. Sailors (I mean real sailors in sailboats) who have found themselves adrift on a windless ocean can attest that zephyrs can be fickle friends. Like all real estate ventures, the value of a wind farm depends on location.

“The power companies that buy the turbines are also getting smarter. They employ teams of meteorologists to scour the world for the best places to put turbines. It is not just a question of when the wind blows, but also of how powerfully. A difference of as little as one or two kilometres (one mile) an hour in average wind speed can have a significant effect on electrical output. And another lot of meteorologists sit in the control centres, making detailed forecasts a day or two ahead to help a company manage its power load. For one problem with wind is that if it stops blowing, the turbines stop turning. After cutting costs, that is the second great challenge of the spread of wind power. The third is that people do not necessarily live where the wind blows. Indeed, they often avoid living in such places. Solving these problems, though, is a task not for the mechanical engineers who build the turbines but for the electrical engineers who link them to places where power is wanted. That means electricity grids are about to become bigger and smarter.”

To learn more about “smart grids,” read my posts GE, Google, and Grids and Building Up rather than Bailing Out. The Economist notes that transmitting large amounts of power over great distances means that new grids are likely to use DC rather AC power (Thomas Edison, a proponent of DC, is probably smiling in heaven).

“The new grids would use direct, rather than alternating, current. AC was adopted as standard over a century ago, when the electrical world was rather different. But DC is better suited to transporting power over long distances. Less power is lost, even on land. And DC cables can also be laid on the seabed (the presence of all that water would dissipate an AC current very quickly). In the right geographical circumstances that eliminates both the difficulty of obtaining wayleaves to cross private land and the not-in-my-backyard objections that power lines are ugly. Indeed, there is already a plan to use underwater cables to ship wind power from Maine to Boston in this way. As it happens, Europe already has the embryo of a DC grid. It links Scandinavia, northern Germany and the Netherlands, and there is talk of extending it across the North Sea to the British Isles, another notoriously windy part of Europe. By connecting distant points, this grid not only delivers power to market, it also allows the system some slack. It matters less that the wind does not blow all the time because it blows at different times in different places. The grid also permits surplus power to be used to pump water uphill in Norwegian hydroelectric plants (a system known as pumped storage), ready for use when demand spikes. Smarter grids, however, would help to smooth out such spikes in the first place. The ability to accommodate inherently intermittent sources such as wind is only one of several reasons for wanting to do this, but it is an important one. … Reducing spikes in demand that way will cut the need for what are known in the industry as ‘peakers’—small power plants such as pumped-storage systems that exist solely to deal with such spikes. Parts of America’s existing dumb and fragmentary electricity grid are so vulnerable to load variations that their owners think they may be able to cope with no more than about 2% of intermittent wind power. Clearly peaks will never be eliminated entirely. However, Mr Abate reckons that a combination of smart grids and gas-fired peakers should push the potential for wind power up a long way. To prove the point, GE is collaborating with the government of Hawaii, a state which is served by a series of small, isolated grids highly vulnerable to disruption. The firm’s engineers reckon that clever grid management will allow up to 30% of local power to come from wind without any blackouts. If that improvement can be translated to the grids on the mainland, wind’s future looks assured.”

In a subsequent article in The Economist [“Wind of Change,” 6 December 2008 print edition], the magazine reported that “a study by researchers at Stanford University, [concluded that] global wind-energy potential in 2000 was about 72,000GW—nearly five times the world’s total energy demand.” The Economist next surveyed the state of solar power [“Another silicon valley?]. The article begins by noting that wind power is a byproduct of solar energy [sunlight stirs up the atmosphere and turbines are placed in the resulting airstreams]. The idea behind solar power, of course, is to tap sunlight directly.

“Fortunately, inventors love that sort of problem. Ideas they have come up with range from using the sun to run simple heating systems for buildings, deploying ‘reverse radiators’ painted black, to the sharpest cutting edge of that trendiest of fields, nanotechnology, to ensure that every last photon is captured and converted into electricity. The most iconic form of solar power, the photovoltaic cell, is currently the fastest-growing type of alternative energy, increasing by 50% a year. The price of the electricity it produces is falling, too. According to Cambridge Energy Research Associates (CERA), an American consultancy run by Daniel Yergin, a kWh of photovoltaic electricity cost 50 cents in 1995. That had fallen to 20 cents in 2005 and is still dropping. … Photovoltaic cells (or solar cells, as they are known colloquially) convert sunlight directly into electricity. But that is not the only way to use the sun to make electrical power. It is also possible to concentrate the sun’s rays, use them to boil water and employ the resulting steam to drive a turbine. These two very different approaches illustrate an unresolved question about the future of energy: whether it will be generated centrally and transported over long distances to the consumer, as it has been in recent decades, or generated and consumed in more or less the same place, as it was a century ago.”

Perhaps the biggest difference between wind and solar power is that the former requires massive grids and the latter does not. Only a billionaire like T. Boone Pickens may be able to afford to build a wind turbine farm, but any relatively well-to-do homeowner can put up a solar panel.

“The idea of solar cells is to keep things local. They are like wind turbines, only more so, in that even a single solar panel can produce power immediately. Put a few on your roof and, if you live in a reasonably sunny place, you can cut your electricity bill. Indeed, you may be able to sell electricity back to your own power company. The problem is that at the moment you may need to take out an overdraft to pay for the solar panels, and you will not get your money back for a long time. Many engineers, however, are working to change that. One of them is Emanuel Sachs of MIT. … Traditional solar cells are made of silicon, like computer chips, and for the same reason. They rely on that element’s properties as a semiconductor, in which negatively charged electrons and positively charged ‘holes’ move around and carry a current as they do so. In the case of a solar cell, the current is created by sunlight knocking electrons out of place and thus creating holes. Dr Sachs’s first contribution to the incremental improvement was a technique called the string ribbon, which halved the amount of silicon needed to make a solar cell by drawing the element (in liquid form) out of a vat between two strings. That invention was marketed by a firm called Evergreen Solar. His latest venture, a firm called 1366 Technologies (after the number of watts of solar power that strike an average square meter of the Earth’s surface), aims to follow this up with three new ideas that should, in combination, bring about a 27% improvement in efficiency. He and his colleagues have redesigned the surfaces of the silicon crystals on a nanoscale in order to keep reflected light bouncing around inside a cell until it is eventually absorbed. They have also managed to do something similar to the silver wires that collect the current. And they have made the wires themselves thinner as well so that they do not block so much light in the first place. Dr Sachs says that these innovations will bring the capital cost of solar cells below $2 a watt. That is closing in on the cost of a coal-fired power station: a gigawatt (one billion watt) plant costs about $1 billion to build.”

Less evolutionary approaches are also being explored.

“Other researchers back a newer technology known as thin-film photovoltaics. Thin-film cells can be made with silicon, but most progress is being made with ones that use mixtures of metals, sometimes exotic ones, as the semiconductor. These mixtures are not as efficient as traditional bulk-silicon cells (meaning that they do not convert as much sunlight to electricity per square metre of cell). But they use far less material, which makes them cheaper, and they can be laid down on flexible surfaces such as sheets of steel the thickness of a human hair, which gives them wider applications. At the moment, the commercial leader in this area is a firm called First Solar, which uses cadmium telluride as the film. But First Solar is about to be given a run for its money by companies such as Miasolé, a small Californian firm, that have gone for a mixture of copper, indium, gallium and selenium, known as CIGS. This mixture is reckoned to be more efficient than cadmium telluride, though still not as good as traditional silicon. And it has the public-relations advantage of not containing cadmium, a notorious poison—though First Solar’s films carefully lock the cadmium up in a way that renders it harmless. At the moment thin-film solar cells are being packaged and sold as standard solar panels, but that could easily change. First Solar applies its films to glass, but Miasolé’s boss, Joseph Laia, points out that his steel-based products are flexible and lightweight enough to be used as building materials in their own right. Greener-than-thou Californians who wish to fall in with their governor’s plan for a million solar roofs, announced in 2006, currently have to bolt panels onto their houses—an ugly, if visible, show of their credentials. If Mr Laia has his way, they will soon be able to use sheets of his company’s CIGS-covered steel as the roofing material itself.”

Making solar panels a little more aesthetic will be a big step in the right direction — at least for city and suburban dwellers. But other innovators are thinking big about solar power and believe that it must be collected differently as well.

“They want to fill the deserts with steel and glass mirrors and use the reflected sunlight to boil water and generate electricity, then plug into the long-distance DC networks developed for wind power to carry the juice to the cities. Those who worry about the political side of the world’s dependence on oil will be less than delighted to find that one country thinking seriously about such systems is Algeria. With the power-hungry markets of Europe to its north, across the Mediterranean, and a lot of sunshine going to waste in the Sahara desert to its south, Algeria’s government is looking for ways to connect the two. It is now building an experimental solar-thermal power station at Hassi R’mel, about 400km south of Algiers, which if all goes well will open [in 2009]. In April work started on a similar project at Aïn Béni Mathar, in Morocco, and others are in the pipeline elsewhere in north Africa. … America has deserts of it own which are about to bloom with mirror-farms too. There are four competing designs: parabolic-trough mirrors, parabolic-dish mirrors, ‘power towers’ which use an array of mirrors to focus the sun’s rays on to an elevated platform, and Fresnel systems, which mimic a parabolic trough using (cheaper) flat mirrors. All either heat up water to make steam, which drives a generator, or heat and liquefy a salt with a low melting point such as sodium nitrate that is used to make steam. All four of these designs are now either operating commercially in the deserts of south-west America or are undergoing pre-commercial trials. Although the total capacity at the moment, according to CERA, is a mere 400 megawatts, this will grow tenfold over the next four years if all projects now scheduled come to fruition, and probably a lot more after that. Moreover, those plants that melt a salt are able to divert part of the heat they collect into a thermal reservoir that can keep the generators turning at night. The main objection to solar power—that it goes off after sunset—is thus overcome.”

As someone interested in any technology that can complement the Enterra Solutions® Development-in-a-Box™ concept, the idea of emerging market countries being able to tap a free resource of energy and sell the electrical power it generates to more developed nations holds great appeal. I’m also aware that plans to cover large areas of desert habitat with solar power farms is likely to get a rise from some environmentalists. It will be interesting to see how the technology develops.

“Two years ago a task force put together by the governors of America’s western states identified 200 gigawatts-worth of prime sites for solar-thermal power within their territory (meaning places that had enough reliable sunshine, were close to transmission lines and were not environmentally or politically sensitive). That is equivalent to 20% of America’s existing electricity-generation capacity: not a bad start.”

The future of solar power, like the future of wind power, depends on its being competitive in price with electricity produced by coal-fired power plants. Almost all predictions of profitability for alternative sources of energy rely on the government making coal-fired plants pay a price for producing greenhouse emissions. The Economist, however, reports that one technology looks like it might be able to compete on a level playing field.

“The most intriguing technology of all … belongs to SUNRGI, a firm based in Los Angeles. This uses mirrors to concentrate sunlight, but focuses it on a solar cell rather than a boiler. The system is said to turn 37% of the light into electricity. In April the firm claimed it would be able to produce electricity for the magic figure of 5 cents a kWh. That claim has yet to be put to the test, and should be viewed with some scepticism until it has been. But it is a good indication of the way the field is going. Solar power now seems to be roughly where wind was a decade ago. At the moment it contributes a mere 0.01% to the world’s output of electricity, but just over a decade of 50% annual growth would bring that to 1%, which is where wind is at the moment. If SUNRGI is to be believed, … the sky is the limit.”

Having surveyed a power source from above the earth and another that moves across the earth, the final alternative power source in the survey comes from beneath the earth — geothermal power [“Beneath your feet“]. Unlike wind power, which is only available when the wind blows, or solar power, which can only be generated when the sun shines, geothermal power is available around the clock.

“The Philippines are not generally associated with the cutting edge of technological change. In one respect, though, the country is ahead of its time: around a quarter of its electricity is generated from underground heat. Such heat is free, inexhaustible and available day and night. It is also part of a geology that sees parts of the country devastated by volcanic eruptions from time to time. The geysers that turn the generators are merely the gentlest manifestations of this volcanism. The question that exercises Jefferson Tester, a researcher at MIT, is whether it is possible to have the one without the other. The Earth’s depths are, after all, hot everywhere. So if there is no natural volcanism around to bring this heat to the surface, his answer is to create controlled, artificial volcanism—what is known as an engineered geothermal system (EGS). Instead of relying on natural hot springs, you make your own.”

Anyone who has drilled for water or oil knows that drilling is expensive and sometimes unpredictable. But unlike searching for water or oil, geologists know that the Earth’s interior is hot. It’s just a matter of how deep you must drill to find the hot spot.

“In principle, this is easy. Drill two parallel holes in the ground, a few hundred meters apart, and carry on drilling until the rock is hot enough (say 200ºC). Then pump cold water down one hole and wait for it to come back up the other at a suitably elevated temperature. The superheated water turns to steam which you use to power a generator. In Dr Tester’s view, the reason this source of power is neglected is that it is invisible. Everybody feels the wind and the sun, but only miners notice that the Earth’s interior is hot, so no one thinks of drilling for that heat.”

Unlike solar and wind, however, scientists talk about “recoverable” not “renewable” reserves of energy. In addition, there have been concerns raised that constantly extracting resources from beneath the Earth’s surface is going to create new environmental conditions with unknown consequences. The reason that geothermal energy is of interest, however, is because there is so much of it.

“The recoverable heat in rock under the United States is the equivalent of 2,000 years-worth of the country’s current energy consumption, according to a report he and his colleagues published two years ago. A similar assessment of Europe’s heat resources from the Earth suggests that they could be used to generate as much electricity as all of the continent’s nuclear power stations produce now.”

One of the benefits of geothermal energy is that the footprint of the power generation station can be relatively small compared to other types of power plants. Even so, the process is not easy.

“Extracting this subterranean energy is not as easy as it sounds. Until the term EGS was coined, the field was known as hot-dry-rock geothermal energy, a name that encapsulates the problem precisely. A century of data collected by oil companies suggest it is impermeable rocks such as granite that are the most effective reservoirs of heat. Their very dryness increases their heat capacity. But to get the heat out you have to make them permeable. Hence the ‘engineered’ in the new name. Some of Dr Tester’s $1 billion would be spent working out how to drill cheaply and effectively through this sort of rock—something that oil companies tend to avoid because impermeable rocks do not contain petroleum. A lot of the money would go on finding ways to force open fissures in the granite to let the water flow from the injection hole to the exit. The Cooper Basin in South Australia has the hottest non-volcanic rocks of any known place in the world, and Australia leads the field in exploiting subterranean heat, with seven firms snooping around the area. One of them, Geodynamics, recently completed what it claims is a commercial-scale well. And the turbines will also turn soon at an experimental non-commercial project at Soultz, in France. If it can be made to work, EGS has got the lot. No unsightly turbines. No need to cover square kilometers of land with vast mirrors. And it is always on.”

The Economist concluded its survey by admitting that its conclusions and predictions could be famously wrong [“Flights of fancy“].

“As far as predicting the technological future is concerned, people almost always either overshoot or undershoot. … In retrospect, this special report will no doubt be proved to have been guilty of both over- and undershooting. It has begun from the premise that big changes are afoot in the energy field, and has tried to pick the technologies most likely to be important.”

The editors admit that they ignored some technologies in which some people still believe.

“The report has ignored some technologies because they will not get anywhere. Fusion, that favorite of fantasists, is 30 years away, as it always has been and probably always will be. Giant satellites collecting sunlight and beaming the energy to Earth as microwaves are an idea of heroic proportions, but enough sunlight gets through the atmosphere to make them irrelevant. … The idea of floating platforms that capture wave energy is technically feasible, but it seems more trouble than building wind turbines. Tidal power works but, even more than hydro, it depends on geography. … All sorts of wacky but intriguing ideas are being looked into, such as flying turbines that would exploit the high winds of the jetstream. And so are perfectly sensible ones, such as ultracapacitors for storing electricity, that are now niche products but might suddenly blossom, to the embarrassment of prophets. Maybe, too, the hydrogen economy will rear its head again—but only if a way can be found of storing the gas easily and at high density. … This report has also ignored the question of efficiency, except in the special context of smart grids. … Besides, as Robert Metcalfe, the networking guru, said at a recent conference: ‘You are not going to conserve your way out of the problem.’ … It will be a long time before King Coal and Queen Oil are dethroned completely, but their reigns as absolute monarchs of all they survey are coming slowly to an end.”

The Economist’s special report was published just before the global economy nosedived. Various stimulus packages enacted around the world may provide impetus for developing green technologies faster and pushing them further. There remains a strong belief that energy sector (especially the renewable energy sector) is going to be a source of new, well-paying jobs. If the global economy is going to grow and emerging markets are going to develop, we know that the demand for electrical power must grow. I’m sure The Economist‘s editors feel fairly comfortable that sanguine predictions for the energy sector will eventually prove mostly accurate.

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