Energy Mini-Reviews

In the face of this dire threat, we urgently need to explore the full range of fossil fuel alternatives. The following articles focus on renewable energy sources. Many are continually sustained by the sun—the largest and most obvious of which is the sunlight striking the planet’s surface at a rate 10,000 times greater than global energy consumption. If all the sunlight falling on the Earth in less than an hour could somehow be captured then mankind’s total energy requirements for an entire year could be satisfied.

Renewable energy assumes various guises. Sunlight taken in by plants stores energy that can later be converted to “biofuels.” The uneven solar heating of the Earth’s surface contributes to atmospheric winds and ocean currents that might be harnessed. Wind, in turn, creates waves and boosts currents whose energy might also be utilized. The sun’s rays evaporate water that may be deposited at high elevations from which it flows downward, perhaps to be exploited as hydroelectric power.

A variety of renewable energy sources will be presented, along with technologies for tapping into them. The practicality of utilizing such diffuse and intermittent sources, as well as the environmental desirability of doing so will be addressed. The fact that a source is “renewable” does not guarantee it is benign. A distributed, composite approach is needed, which will involve picking the right blend of sources and technologies to meet our energy needs in a sustainable way with minimal harm to the environment.

Currently, renewable energy sources comprise just 7 percent of America’s total energy supply. But renewable advocates trust the outcome will soon be different, driven by high oil prices, fears of global warming, and intervening technological progress. This time, many would argue, neither society nor the planet as a whole can afford failure.

The parallel is apt because Gorlov’s invention, which resembles a giant eggbeater, is a modified wind turbine that can convert 35 percent of water’s kinetic energy into electricity, regardless of which way the water is moving. This makes the technology well-suited to unidirectional rivers or tidal currents that change directions four times a day. It can do all this, Gorlov claims, without disturbing fish or boat traffic. The device, which has been tested in the Brazilian Amazon, the Cape Cod Canal, the Uldolmok Strait off of South Korea, and other sites, is now close to commercialization—part of a budding industry that aims to change hydropower as we know it.

While conventional hydropower provides about 7 percent of America’s electricity—and accounts for about 75 percent of the electricity supplied by renewable sources—prospects for future growth appear scant owing to the environmental toll of large dams. The U.S. Energy Department estimates that “free-flow” hydro technologies could supply 15,000 megawatts of generating capacity (comparable to 15 large nuclear plants), but Gorlov considers the potential much greater. Worldwide, he says, “more than 90 percent of the energy in moving water is in sites where you can’t build dams”—places like rivers with low-grade currents, tidal estuaries, and ocean currents in general. Tapping into the water flowing beneath the Golden Gate Bridge, for example, could yield two times more electricity than San Francisco’s peak demand.

In 2003, a 300-kilowatt turbine installed in a Norwegian strait became the first free-flow hydro system to deliver electricity to a power grid. Also in 2003, a “watermill” of similar capacity began operating in a tidal channel a mile offshore from Lynmouth, England. Since then, prototypes have been placed in New York’s East River, Nova Scotia, and other sites.

Meanwhile, plans are being laid for America’s biggest river, the Mississippi. Texas-based Hydro Green Energy now has two turbines mounted from a barge in Hastings, Minnesota, continuously feeding 70 kilowatts into the power grid. Hydro Green is investigating other spots along the Mississippi, as is Free Flow Power of Massachusetts, which has secured federal permits to explore 50 different sites. Ultimately, Free Flow president Dan Irvin envisions 200,000 turbines spread along the length of the river, generating 2,000 megawatts. All without approximately impacting river flow.

Various methods have been proposed over the years to harness waves. Some devices channel waves directly through turbines; others utilize the bobbing vertical motions of buoys stationed in a wave’s path. Other devices sit on the shoreline, where they’re pounded by waves that, in turn, force air through a turbine. As a whole, the wave industry is still in the fledgling stage, lagging behind wind technology—in terms of performance and cost—by a good 25 years. Although extracting usable energy from waves has proved challenging, and lacks the centuries-long tradition associated with windmills, ocean energy backers believe wave systems will eventually make their mark. To them, it’s a question of "when", rather than "if".

And in a modest way, “when” has already come to northern Portugal where the world’s first commercial wave farm is now in place three miles offshore. The system consists of three, 459-foot-long wave converters (built by Pelamis Wave Power of Scotland), which can produce 2.25 megawatts of electricity, but a proposal has already been filed to expand the system’s capacity 10-fold.

A Canadian company recently signed an agreement to start delivering energy by 2012 from a two-megawatt wave-energy system 2.5 miles from the coast of northern California—the first such commercial agreement in North America.

Meanwhile, even more ambitious plans are being laid in Oregon, where the state has established the goal of getting 25 percent of its electricity from renewable sources by 2025. Energy planners in Oregon see waves as an important part of the mix, with eight wave energy projects already being planned along the state’s 360-mile-long coastline.

Of course, plans are one thing, while reality may be another. For the fact is, building a device that can last in a marine environment under a steady pummeling by waves, as well as withstand the periodic violent storm, takes a substantial engineering feat. A test buoy near Newport, Oregon in 2007 sunk after just two months of operation, even though it was supposed to hold up for a century. That might have been bad luck, or it was a sign that further technical progress is needed before waves can emerge from what the journal Nature has called the “second tier of renewable energy resources.”

According to a researcher at the National Renewable Energy Laboratory, the United States could, in principle, meet all its energy needs by installing photovoltaic systems over 0.3 percent of the continental United States--less than one-fourth the area now devoted to roads--assuming modest 10 percent electrical conversion efficiencies. That area could be reduced, of course, by efficiency gains or by supplanting some photovoltaic cells with wind turbines and other renewable energy technologies.

Despite the encouraging signs, the total contribution from photovoltaic power sources is miniscule—accounting for just 0.15 percent of the world’s electrical generating capacity in 2006--and it would take several years at current growth rates to reach 1 percent of the world’s capacity. The biggest barrier to accelerated deployment is cost. Although solar cells have dropped eight-fold in price from 1980 to 2005, solar electricity remains about five times more expensive than electricity from coal. In the end, we may have to pay more for carbon-free power, but photovoltaic backers still see plenty of room for improvement.

By boosting cell efficiencies, one can achieve the desired power output with a smaller array. Silicon solar cells, the current industry standard, routinely convert about 20 percent of the energy in sunlight into electricity, but face a theoretical limit of 31 percent. However, cells composed of layers of different materials—each “tuned” to a different frequency of the solar spectrum—have already achieved efficiencies above 40 percent.

A 2005 report by the San Francisco-based Energy Foundation claimed that photovoltaic systems installed on the rooftops of residential and commercial buildings, using state-of-the-art silicon cells, could supply a large fraction of America’s electricity needs. More recently, MIT engineers have developed windows that can concentrate sunlight 40-fold and direct it to narrow strips of solar cells along the window’s edge. Rather than building separate structures, the idea is to deploy solar cells on roofs, walls, and windows whenever feasible, preferably integrating them into building materials from the very start.

The widespread implementation of such a strategy would inevitably bring some economies of scale. Yet solar power enthusiasts also hope that continued advances in semiconductors and nanotechnology will lead to the kind of exponential cost reductions that have prevailed for decades in the computer industry.

Prior to their conversion to farmland and other developed tracts, these wetlands served as a vast floodplain - a place for floodwaters to go. But the river is now lined, for some 2000 kilometers upstream of New Orleans, with high concrete levees that trap floodwaters and funnel them toward the city, which is where they ended up, tragically, in 2005. Without a steady influx of freshwater or sediments to sustain them, the surrounding wetlands are not just shrinking, but literally sinking, under their own weight.

So what’s to be done? In 1998, scientists and state and local officials proposed a $14 billion, 30-year engineering plan called Coast 2050 to revive Louisiana’s marshes, swamps and barrier islands, an area over twice the size of the Florida Everglades. The proposal mostly involved pumping river water and sediments back into the delta. So far, the federal government has committed $540 million to such efforts. About $120 million of that sum goes to the Davis Pond Freshwater Diversion project–an attempt to reproduce Mississippi floods by sending water into a three-kilometer-long channel that should sustain more than 130 square kilometers of surrounding marshland.

While a more ambitious venture like Coast 2050 could yield even greater benefits, Columbia University ecologist Stuart Pimm is wary of mammoth water projects that often fail to deliver on their promise. Wetlands management is an uncertain business, given that ecologists still don’t know the amount of water, sediments and nutrients a marsh needs to flourish, or precisely when these ingredients should be supplied. “My rule of thumb when it comes to ecosystems,” Pimm explained in Science Magazine, “is that larger is better than smaller, connected is better than fragmented, and natural is better than managed.”

The overall flow off Miami’s coast is more than 30 times greater than the combined flow of the world’s freshwater rivers. “This is the closest location on the planet of a major ocean current to a significant urban center of electrical demand,” says Rick Driscoll, who directs the Ocean Energy Technology center at Florida Atlantic.

In early 2009, Driscoll’s group hopes to begin testing the feasibility of harnessing this energy source. Assuming the necessary permits are secured, they will place a 10-foot-diameter turbine in the middle of the Gulf Stream, 15 or so miles from shore. The experimental unit will be moored to the ocean floor and sit some 30 feet below the surface. Practical power-generating devices would have much bigger rotors and likely be placed 100 or more feet deeper to reach stronger currents and stay well below boat traffic.

In the late-19th century, Thomas Edison became fascinated with the notion of drawing energy from the Gulf Stream, though it may take 21st-century technology to realize this dream. Ocean current speeds are generally low compared to wind speeds, only averaging about 5 miles-per-hour in the Florida Current. But given that water is more than 800 times denser than air, the amount of energy intercepted by a turbine there would exceed that intercepted by a comparably-sized wind turbine in 45 mile-per-hour winds.

Even if the preliminary tests go well, the plan is to proceed cautiously given that the Gulf Stream moderates temperatures in the United Kingdom and Europe and impacts climate globally. Thanks to the warming ocean waters, Iceland and Scotland aren’t nearly as frigid as Labrador, which is equally far north. Similarly, the Faroe Islands of the north Atlantic average 22 degrees warmer in the winter than Anchorage, Alaska, at the same latitude, and odds are the 50,000 Faroe Islanders would just as soon keep it that way.

One way of avoiding major environmental surprises would be to extract exceedingly modest amounts of energy at first. The U.S. Interior Department estimates it would take less than 1/1000th of the available energy within the Florida strait to meet a third of the state’s electrical demand (which is now about 30,000 megawatts), and it would be awhile before ocean generating devices could reach even a tiny fraction of that mark.

Strictly speaking, nuclear power is not “renewable,” as most reactors in operation today burn (through the process of nuclear fission) uranium fuel that is finite in supply. Nuclear energy is, however, a major source of electricity, contributing about 17 percent of the world’s electric output. The urgency of global warming is largely behind nuclear power’s rehabilitation, but other factors are responsible as well. The economic outlook has improved with the steady rise in fossil fuel prices. Nearly 30 years after the accident at Three Mile Island and more than 20 years after the Chernobyl disaster, the safety record has also improved. The next generation of nuclear reactors should be designed so that they are incapable of suffering a so-called “meltdown” accident.

One problem that hasn’t gone away concerns the disposal of the waste products associated with this type of power generation. This waste remains radioactive for tens of thousands of years and, for some radioisotopes, millions of years. Designated more than 20 years ago as the site of the nation’s high-level waste repository, the Yucca Mountain facility in Nevada remains mired in scientific and political controversy and presently holds not a single ounce of radioactive waste. Additionally, worries about the diversion of fissionable material and the targeting of nuclear power plants by terrorists seem more troublesome in a post 9/11 era than ever.

In light of these unresolved issues, it would be naïve to expect nuclear power to change the worldwide energy picture overnight. Major increases in nuclear production would take a sustained, unprecedented building boom that would surprise even diehard enthusiasts. At the same time, some ardent critics are also softening their stance, realizing that any carbon-free power source, especially one that now provides 20 percent of the nation’s electricity (second only to coal), cannot be dismissed out of hand.

Unfortunately, almost all the ethanol produced in this country—about 7 billion gallons per year—is derived from corn. In fact, 20 percent of the corn harvested in 2007 was used to make ethanol, which yielded the equivalent of just 3 percent of total gasoline consumption. Even if the entire corn crop were used, we still would not come close to replacing gasoline. Nor would we want to turn all that food into fuel, since such a move would surely drive food prices sky high, as the costs of milk, beef, pork, and other goods are all tied to the cost of corn. Moreover, the hoped-for environmental gains of this type of biofuel are offset by all the energy and fertilizer it takes to produce corn, as well as the carbon dioxide and other greenhouse gases—namely nitric oxide and methane—released along the way.

There is another choice: rather than growing “energy crops” at great expense and considerable ecological toll, fuels can be produced from agricultural residues like corn cobs or wood wastes. Readily-grown plants like switchgrass could also be cultivated, with little or no fertilizer, on land not presently considered arable. A 2008 report in a National Academy of Sciences journal claimed that switchgrass-derived ethanol could yield six times more energy than is used to produce it, with attendant reductions in greenhouse emissions.

The trick is in converting the cellulose found in plant walls into ethanol, a much more technically demanding task than turning starches from corn kernels into ethanol. Cellulose is sturdy by design, which makes plants strong enough to stand upright and tough enough to ward off animals and the elements.

Although cellulose-derived ethanol is not yet a commercialized industry, more than a half dozen U.S. pilot plants are in the works. The ultimate success of this strategy rests on microbes—bacteria or yeasts—that can efficiently break down cellulose molecules into sugars which can then be fermented into ethanol. The ideal microbe would preferably do both jobs—a feat that could potentially cut processing costs in half possibly making cellulosic ethanol the transportation fuel of the future.

According to the current vision, which is not so different from Verne’s scenario, clean-burning hydrogen, produced via the electrolysis of water, would be dispatched to “gas” stations—either in liquid or gaseous form—to support a nationwide fleet of nonpolluting, fuel cell-powered vehicles. Tantalizing as that picture is, it has progressed slowly over the decades, and many obstacles remain.

First off, it’s important to stress that hydrogen is not an energy source, per se, but rather a form of energy like electricity. While hydrogen can be converted to electric power in a fuel cell with no pollution whatsoever and water vapor the only byproduct, it’s only as clean as the source of energy from which it originally comes. If coal-generated electricity is used to electrolyze water, carbon dioxide and other pollutants will be inevitably produced. The goal then is to generate hydrogen from clean, renewable sources like wind power, in which case hydrogen vehicles would be truly pollution-free (save for the small amounts of nitrogen oxides given off if hydrogen is burned in internal combustion engines). Ethanol-fueled vehicles are not nearly as attractive in this regard, for they contribute about as much smog as gasoline, despite the benefits they confer in terms of carbon dioxide.

In theory, hydrogen has a lot to recommend itself, but in practice, a number of problems still need to be worked out—and that could take decades. Fuel cells, which can turn more than 60 percent of hydrogen’s latent energy into electricity, are quite expensive, presently adding about $100,000 to the price of a “concept car.” Using hydrogen as a pressurized gas requires containers far bigger than gas tanks, whereas liquid hydrogen requires containers that are not only bulky but also refrigerated to –423°F. Chemically storing hydrogen in advanced materials called “metal hydrides” is a promising idea though not yet practical.

Then there’s the matter of overhauling the massive infrastructure now geared to dispensing gasoline. California, with more than a dozen hydrogen fueling stations, has made a start. It’s now possible, in fact, to travel the length of the state in a hydrogen car, though judicious driving—and a vehicle with decent range—is required to bridge the 300-plus-mile gap in hydrogen service lying between San Jose and Burbank.

The resource, itself, is undeniably vast. The state of North Dakota alone has greater wind reserves than Germany—the current world leader in wind generating capacity (22,000 megawatts)—yet North Dakota’s potential remains virtually untapped, according to Daniel Kammen of the University of California, Berkeley. While Kammen estimates that U.S. wind farms could generate three times more electricity than the nation consumes, the practical obstacles are formidable.

Various objections have been raised to wind farms: they are unsightly, noisy, lethal to unsuspecting birds and bats, and, for ocean-based systems, a hazard to boaters, fishermen, and marine life. Such concerns need to be investigated thoroughly in advance, as all sites are not created equal. But these potential problems must also be balanced against the drawbacks of competing electricity sources, which for fossil fuel-burning power plants are likely to be considerable. In some cases, even the carbon-free, pollution-free benefits of wind power may not be enough to counter the oft-powerful “not-in-my-backyard” sentiment.

A plan to build 130 wind turbines in the waters of Nantucket Sound is a case in point. The proposal for America’s first offshore wind farm has elicited fierce opposition–primarily from Cape Cod homeowners concerned about their views and the value of their beachfront property–ever since a company called Cape Wind Associates announced its intentions in 2001. After surmounting a barrage of environmental and legal challenges for seven years, the project has come closer to the construction stage though victory is still uncertain.

Advocates of the Cape Wind plan may find encouragement in Europe, where the experience with offshore wind has been much more favorable. Denmark, for instance, now gets about 20 percent of its electricity from wind turbines, and it exports surplus offshore wind power to its neighbors, Sweden, Norway, and Germany. Rather than being regarded as eyesores, the towering turbines in places like Copenhagen Harbor have become tourist attractions that are commonly featured on postcards.

“I have never seen an opportunity for the country like the one that’s emerging now,” Al Gore claimed in July 2008, while urging the nation to get all its electricity from carbon-free sources within 10 years.

The tiny Danish island of SamsØ, with a population of 4,300, shows what might be done. A decade ago, the homes were mostly heated by oil, drawing on electricity from coal-burning power plants on the mainland. But the island now produces more energy from renewable sources than it consumes, from 11 large land-based wind turbines and 10 offshore ones. Doing something like this worldwide would involve duplicating SamsØ’s efforts a million-fold, in areas where changes would not come so readily. Nevertheless it demonstrates that things can happen quickly when there’s a will and a way.

Switching to a renewable energy system will take not only new energy sources but a whole new paradigm. Instead of relying on a handful of fuels—oil, coal, natural gas, and uranium—we’ll need a large, diversified mix of technologies that vary depending on the resources indigenous to a given region. One area may be endowed with the sun and wind, another with tides and waves, yet another still with flowing streams and fields amenable to switchgrass cultivation. We’ll need new ways of powering transportation vehicles and new ways of transporting and storing energy—the latter being essential for sources intermittent in nature. We’ll need to use energy with the utmost efficiency, with conservation being first and foremost. Finally, we’ll need to weigh the environmental merits of renewable energy sources and technologies with a critical eye, applying as much vigilance as should be applied to conventional approaches.

Many skeptics argue that we cannot pin our hopes on such diffuse and fickle energy sources as the sun and the wind that aren’t always around when and where you need them. Others would argue that, in view of the climate change unfolding at a pace unprecedented in our planet’s history, we can’t afford not to.

EAF operates two programs to support the advance of innovation and entrepreneurship in the rural energy space, the Knowledge Exchange and Cluster Development Program & the Innovation Funding program.

The Knowledge Exchange and Cluster Development Program has organized meetings and communications among leading rural energy entrepreneurs around the developing world to help identify needs and establish working relationships.

The Innovation Funding Program makes funds available to support the innovations of enterprises to accelerate access to clean energy. Projects can include such efforts as developing applications to meet energy needs or supporting linkage with microfinance to increase affordability. The EAF has funded projects that link microfinance and energy products in the Philippines, replace kerosene lamps with solar lighting for fishermen on Lake Victoria, Tanzania and introduce solar-powered refrigerators for rural stores in Nicaragua.

If you are interested in learning more about Energy Access Foundation’s work, please contact:

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