Renewables Research: A Progress Report
June / July 2006
Volume 4 Number 3
Oil, coal and natural gas won't be enough. Nuclear energy won't do it alone, nor will wind power or solar energy. We will need a diverse portfolio of existing sources of energy over the coming decades, while revving up the research and development of promising new technologies.
Today's world has an insatiable appetite for energy, and it has become clear that fossil fuels alone cannot meet the energy requirements of the coming generations. Worldwide, energy consumption is expected to increase 50 percent over the next two decades, from 12 terawatts to 18 terawatts. By 2050, an additional 20 terawatts of energy will be required to meet the demands of the billions of people moving from "low impact" lifestyles to "high impact" lifestyles.
This has enormous implications for the environment, and, as demand rises and conventional energy supplies dwindle, the cost of everything will be affected.
This is where the U.S. Department of Energy's National Renewable Energy Laboratory has much to contribute.
NREL's mission is to develop renewable energy and energy efficiency practices and to advance related science and engineering. The laboratory is charged with transferring that knowledge and subsequent innovations to the market to address America's energy and environmental goals.
NREL's scientists and engineers work in more than 50 programs on a wide variety of sources of energy and ways to use that energy more efficiently. Four areas of significant research effort—€”solar, wind, bioenergy and hydrogen—€”illustrate the promise and challenges ahead.
Solar
The potential of solar energy is tremendous. The solar resource is good in every state; even Alaska has the equivalent solar resource of Germany, the largest solar market in the world today. Scientists estimate that worldwide as much as 600 terawatts of solar energy could be captured.
R&D has greatly reduced the cost of solar electricity over the past 30 years, from several dollars a kilowatt-hour to less than 25 cents per kilowatt-hour. Through developing better manufacturing techniques, higher efficiency photovoltaic devices and new solar nanomaterials, NREL and the industry expect to bring that cost down much further, to 4 to 6 cents a kilowatt-hour by 2025.
Concentrating solar power—€”using the sun's heat to produce electricity—€”might even come in a little cheaper.
The approach to reducing costs is twofold. One route is to work on short-term applied R&D to bring down the costs of existing processes and manufacturing methods.
NREL has partnered for more than a decade with the U.S. PV industry to reduce manufacturing costs and scale up production capacity. The results have been significant—€”a cost drop of 58 percent from 1992 to 2004—€”and PV manufacturers expect better fabrication methods and economies of scale to reduce costs even further.
Efforts to improve the efficiencies of thin film solar cells also are paying off. These technologies use films of far less semiconductor material than silicon wafers. Thin film devices can be made in large runs, using mass-production techniques. In addition, they are perfect for specialty and building integrated applications. Right now, efficiencies for thin film PV range from 5 percent to 11 percent, but higher efficiencies are being realized in the laboratory that, when translated to manufacturing, could lead to 4-cent per kilowatt-hour electricity.
The second course to reducing cost is to continue work on longer term research that industry can't afford on its own, to identify and develop the next generation of renewable energy technologies.
In solar, this may come in the form of nano-structured materials beginning to be explored at NREL and elsewhere. The development of these materials, along with work toward increasing solar cell efficiencies through using multiple layers of semiconductors could very well lead to extraordinarily low-cost solar materials that could be used in a wide variety of applications to make electricity.
Wind
In the windiest places, wind energy now competes on a cost basis with electricity from other sources. Wind is a great renewable energy success story, with costs coming down from 40 cents a kilowatt-hour in 1981 to about 4 cents a kilowatt hour today.
The challenge for wind energy today is transmission. Most of the nation's population doesn't live in the country's windiest places. NREL R&D is focusing on two approaches to using the wind resource closer to population centers.
First is research into low-speed wind machines; turbines that will produce reasonably priced power—€”around 3 cents a kilowatt hour—€” at sites where the average annual wind speed is 13.5 miles per hour as compared to the 15 miles per hour needed now. That would increase the land in the nation with cost-effective access to wind power by more than 20 times.
To do this, NREL scientists and engineers have considered just about every component of wind energy—€”aerodynamics, understanding turbulence, advanced controls, advanced materials and power electronics. Among the approaches showing promise are taller towers and bigger machines. Researchers also are looking at ways to build huge blades on-site to eliminate transportation costs and exploring lighter-weight materials, such as carbon fiber, for wind turbine blades.
Second, researchers at NREL's National Wind Technology Center are looking at the feasibility of putting wind turbines off-shore in water deeper than 30 meters. Much of the U.S. population lives near the coasts and the wind is steadier and stronger blowing across the ocean, giving this idea two advantages.
There are no wind farms off the coasts of the United States today, but 17 projects in Europe provide 600 megawatts of generating capacity. Those wind turbines are anchored to the ocean floor in shallow water. For deeper water, entirely new designs, perhaps based on floating platforms like those used in off-shore oil and gas drilling, will be necessary.
Bioenergy
Biomass—€”plants and plant-based material—€”can provide fuels and chemicals comparable to those now derived from petroleum. Biomass converted to ethanol provides the best short-term substitute for the gasoline and diesel that powers our cars, trucks and buses.
The goal is to make ethanol 30 percent of the transportation fuel supply by the year 2030. Ethanol made from corn and blended into gasoline is becoming more and more common at U.S. fueling stations and could amount to 13 billion gallons a year by 2015, about 7 percent of the gasoline use. Clearly more is needed.
That's where cellulosic ethanol comes in. This is fuel derived from the sugars locked up in the non-edible parts of plants—€”the stalks, stems, and leaves. Nature has made it fairly easy to get to the sugars stored in the food part of crops such as corn. And those sugars are relatively easy to convert to ethanol.
But, nature has made it much harder to get to the sugars in the other parts of the plant. NREL research has developed effective technologies to thermochemically treat biomass and break it down into component sugars that can be fermented into ethanol.
This opens up the ability to convert a huge amount of biomass into transportation fuel. Estimates are that the U.S. could make nearly 45 billion gallons of cellulosic ethanol from agricultural and crop resources, enough, when added to ethanol made from corn, to reduce the nation's gasoline consumption by 30 percent.
Challenges remain, however. The process needs to be refined to reduce the cost to a level competitive with corn ethanol, from about $2.50 a gallon today to $1.07 a gallon. Progress is being made on several fronts. Reducing the cost of enzymes used to help break down the cellulosic material, producing better fermenting organisms, finding cheaper ways to harvest and transport the biomass feedstock all are promising.
A petroleum refinery produces both fuels and the chemicals that are used to make plastics, pharmaceuticals, fibers and a host of other modern products. So, too, could a biorefinery. Scientists at NREL are working on developing the biological and thermochemical technologies that can use the components of plants as the building blocks for the materials of modern life.
Hydrogen
Hydrogen is the most abundant element in the universe. On Earth, it's found mostly in water. As a gas it is odorless, colorless, tasteless and non-poisonous. As a fuel hydrogen is clean. Hydrogen is versatile. We can make hydrogen in one place to store energy that can be used somewhere else. Hydrogen can generate electricity, provide heat and fuel our cars. No wonder people talk excitedly about the coming hydrogen economy.
When hydrogen is produced from renewable sources—€”solar, wind, biomass—€”and water, the world could have an endless supply of clean, locally produced energy. Much research and technology development will be necessary to get us there. NREL is working with DOE, universities, industry and other national laboratories to outline the steps to realizing the vision of a hydrogen economy.
Demonstrations are now underway to prove hydrogen's potential for use as a transportation fuel, producing electricity, and providing heat. Fuel cells—€”a device like a battery that uses hydrogen to produce electricity electrochemically—€”are being improved. Storage systems for hydrogen, perhaps using carbon nanotubes developed at NREL, are being researched. NREL scientists and engineers are exploring more efficient ways to make hydrogen from water by using electricity generated from wind, solar electricity, or tiny green algae.
The transition to a hydrogen energy economy is beginning, but still is decades away.
Only by developing an entire portfolio of energy sources will we be able to meet the short, medium and long term needs of a nation and world increasingly dependent on inexpensive, reliable energy. For more information on NREL and its programs, go to www.nrel.gov.
George Douglas is media relations manager for the National Renewable Energy Laboratory.
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