The rise of renewable energy

Solar cells, wind turbines and biofuels are on the verge of becoming real energy sources. Establishing new policies could accelerate their development dramatically

By Daniel McMann, Scientific American

It is impossible to plan a plan for a significant reduction of greenhouse gas emissions relying only on increasing the efficiency of energy. Because economic growth increases the demand for energy - more coal to run new factories, more oil to power new cars and more natural gas to power new homes - the rate of carbon dioxide emissions will continue to rise even though the cars, buildings and electrical appliances produced today are more efficient in terms of energy utilization. If the United States wants to address the alarming global warming trend, it must seriously commit to developing renewable energy sources that release little or no carbon compounds.

Renewable energy technologies suddenly came into vogue for a short time thirty years ago, as a response to the oil boycott of the 70s, but interest and support for them did not last long. However, in recent years there has been a dramatic improvement in the performance and economic viability of solar cells, wind turbines and biofuels - ethanol and other fuels that come from plants - paving the way for their mass commercialization. In addition to the environmental benefits, renewable energy sources promise to increase the energy security of the United States, by reducing its dependence on fossil fuels from other countries. The cost of the renewable alternatives also increased as a result of the increase in oil and natural gas prices and the obvious instability of these prices.

Today there are unprecedented opportunities in the field of renewable energy, so this is an ideal time to develop clean energy for future generations. But to meet the challenge, the investment of scientific, economic and political resources will be required. The policy makers and the citizens must demand steps in the direction, and demand from each other to speed up the transition.

 

Give the sun a hand

Solar cells, also known as photovoltaic cells, convert sunlight into electrical current using semiconductor materials. Today they provide only a tiny segment of the world's electricity: their global production capacity is 5,000 megawatts, which is only 0.15% of the production capacity of all sources. But the sunlight could provide 5,000 times the global consumption today. Thanks to technological improvements, a decrease in costs and sympathetic policies of many countries in the world, the annual production of solar cells increased by more than 25% per year in the last decade, and by an impressive rate of 45% in 2005 alone. In 2005, cell manufacturers added 1,727 megawatts to global electricity production capacity, of which 833 were produced in Japan, 353 in Germany and 153 megawatts in the USA.

Today it is possible to produce solar cells from a variety of materials, starting with the traditional wafers of polycrystalline silicon, which still dominate the market, and ending with cells made of thin silicon layers and devices composed of plastic or organic semiconductors. Thin film cells are cheaper to manufacture than crystalline silicon cells, but they are also less efficient at converting light to electricity. In laboratory experiments, the crystalline cells achieved an efficiency of 30% or more. The efficiency of commercial cells of this type currently varies between 15% and 20%. The efficiency of all types of solar cells, both in the market and in the laboratory, has been steadily increasing in recent years, and this shows that expanding the research effort could further improve the performance of the solar cells currently on the market.

Solar cells are particularly easy to use, because they can be installed in many places: on roofs, on the walls of houses and office buildings or in extensive arrays in the desert. You can even sew them into your clothes and use them to power portable electronic devices. The state of California has joined Japan and Germany in leading a global effort to install solar generation facilities. The "Million Solar Roofs" initiative aims to bring a new production capacity of 10,000 megawatts by the year 2016. From studies conducted in my research group, the Laboratory for Research on Renewable and Adequate Energy, at the University of California, Berkeley, it appears that the production of solar cells in the US alone could grow up to 10,000 megawatts in just 20 years, if there is no change in current trends.

The biggest challenge will be reducing the price of solar cells, which are relatively expensive to produce. The total cost of electricity produced using crystalline cells is 20 to 25 cents per kilowatt-hour. This compares to 4 to 6 cents for electricity produced from coal, 5 to 7 cents for electricity produced from burning natural gas, and 6 to 9 cents for power plants burning biomass (it is difficult to state the exact cost of electricity from nuclear reactors, as experts differ on which components should be included Estimates range from 2 to 12 cents per kilowatt-hour. Fortunately, the price of solar cells has decreased consistently over the past decade, largely due to improvements in manufacturing processes. In Japan, which added 290 megawatts of generating capacity in 2005 and has exported even more, the cost of solar cells has fallen 8% annually. In California, 50 megawatts of solar power were installed in 2005, and costs have fallen 5% annually.

Surprisingly, Kenya is the leading country in the world in the number of solar energy systems installed there every year (but not in the number of additional watts). More than 30,000 tiny solar panels, each producing just 12 to 30 watts, are sold in Kenya each year. For an investment of less than $100 in the solar panel and wiring, the system can be used to charge a car battery, so that it can provide enough electricity to light a fluorescent light or a small black-and-white television for a few hours a day. The number of Kenyans who adopt the solar solution each year is greater than the number of those who connect to the national electricity grid. Thin layer cells made of amorphous silicon are often used in these panels. Although the efficiency of these solar cells is less than that of crystalline cells by half, their cost is so low (at least four times), that they are more economical and useful for the two billion people living today in the world without access to electricity. Sales of small solar systems are skyrocketing in other African countries as well, and the trend may accelerate even more due to developments in the production of cheap solar cells.

Furthermore, photovoltaic cells are not the only rapidly developing form of solar energy. Solar heat systems, which collect sunlight to produce heat, are also gaining popularity. Such systems have long been used, such as solar boilers to supply hot water to homes and factories, but they can also be used to generate electricity without the need for expensive solar cells. In one of the models, for example, mirrors focus the sunlight on a Stirling engine, an extremely efficient device that contains working gas that flows from a hot chamber to a cold chamber and back again. The gas expands as a result of being heated by sunlight, and pushes a piston that turns a turbine.

In the fall of 2005, the company "Stirling Energy Systems" from Phoenix announced its plan to build two large power plants in Southern California that operate on the heat of the sun. The company signed a 20-year electricity supply agreement with Edison Southern California to purchase electricity from a 500 megawatt power plant to be built in the Mojave Desert. The facility, which will be spread over an area of ​​18,200 dunams, will include 20,000 concave dish mirrors, which will focus sunlight on Stirling engines the size of an oil barrel. The plant is scheduled to start operating in 2009, and it will be possible to expand it afterwards up to a production capacity of 850 megawatts. Stirling Energy Systems also signed a 20-year contract with the San Diego Energy Company to build a 300-megawatt, 12,000-plate power plant in Imperial Valley. This facility will eventually be upgraded to 900 megawatts.

The financial details of the two projects from California have not been published, but the electricity produced by solar thermal technologies currently costs between 5 and 13 cents per kilowatt-hour, with a first-class concave mirror system. However, because this project involves highly reliable technologies and mass production, production costs are expected to eventually drop to 4 to 6 cents per kilowatt-hour, a price that will successfully compete with current coal electricity prices.

 

The answer is borne in the wind

The growth rate of the electricity industry produced from wind competes with the growth rate of the solar industry. Global electricity generation capacity from wind turbines has grown by an average of 25% per year over the past decade, reaching almost 60,000 megawatts in 2005. In Europe, the growth has been nothing short of amazing: from 1994 to 2005, wind power generation capacity in the European Union jumped from 1,700 to 40,000 MW. Germany alone has a production capacity of more than 18,000 megawatts, thanks to a vigorous construction program. In the Schleswig-Holstein region in northern Germany, 2,400 wind turbines provide a quarter of the annual electricity consumption, and in some months wind energy provides more than half of the electricity consumption in the region. Also, Spain has 10,000 megawatts of generating capacity, Denmark 3,000 megawatts and the United Kingdom, the Netherlands, Italy and Portugal have more than 1,000 megawatts each.

In the United States, the wind energy industry has experienced dramatic acceleration in the last five years. Total generating capacity jumped 43% to 9,100 megawatts in 2005. Although wind turbines currently generate only 0.5% of US electricity, they have tremendous expansion potential, especially in the wind-swept Great Plains states (North Dakota, for example, has Wind energy sources are larger than in Germany, but the production capacity there is only 98 megawatts. If the United States built enough wind farms to fully utilize these resources, the turbines would be capable of generating up to 11 billion kilowatt-hours, or in other words, nearly three times the total electricity produced in the country by all energy sources in 2005. The wind energy industry is developing increasingly large and efficient turbines, each of which can produce 4 to 6 megawatts. And in many places wind energy is the cheapest form of new electricity, costing 4 to 7 cents per kilowatt hour.

The increase in the number of new wind farms in the US has been accelerated by production tax credits, which provide a modest subsidy of 1.9 cents per kilowatt-hour, allowing wind turbines to compete with coal-burning power plants. Unfortunately, Congress repeatedly threatens to take away these privileges. Instead of introducing a long-term subsidy for wind energy, the US legislature extends the credits on an annual basis, and the ongoing uncertainty slows down investments in wind farms. Congress is also threatening to block the construction of a 130-turbine offshore wind farm off the coast of Massachusetts, which could provide 468 megawatts of generating capacity – that is, enough electricity for almost all of Cape Cod, and the islands of Martha's Vineyard and Nantucket.

The hostility towards wind energy comes partly from the electric companies, who are afraid to adopt the new technology, and partly from "Nimbys" (NIMBY, meaning Not in My Backyard - not in my backyard). Although it is possible that the concerns regarding the effect of the wind turbines on the landscape should not be dismissed out of hand, a balance must be reached between them and the social cost of the alternatives. As American society's energy consumption continues to grow, rejecting the wind farm solution often leads to the construction or expansion of fossil fuel-burning power plants, which will have far more devastating environmental impacts than wind farms.

 

Green fuels

Scientific research also continues to advance in the field of developing biofuels that could replace at least some of the oil currently consumed by cars. The most common biofuel in the US today is ethanol (alcohol), which is mostly produced from corn and mixed with gasoline. Ethanol producers enjoy a considerable tax break: with the help of an annual subsidy of 2 billion dollars, they sold more than 16 billion liters of ethanol in 2005 (almost 3% of the total volume of fuel for cars), and production is expected to increase by 50% by 2007. Some of the policy makers They expressed doubt about the necessity of the subsidy, and cited studies in which it was found that harvesting corn and distilling ethanol consumes more energy than is produced from the fuel obtained in car engines. However, from the analysis of the findings that I conducted with my colleagues recently, it appears that in these studies the by-products produced alongside the ethanol were not properly taken into account. When we considered all inputs and yields, we found that ethanol has a net energy gain of almost five megajoules per liter.

However, we also found that the effect of ethanol on greenhouse gas emissions is not so clear. Our best estimates show that switching from gasoline to ethanol produced from corn reduces greenhouse gas emissions by 18%, but this is a partial and limited analysis, due to significant uncertainties regarding certain agricultural practices, especially the environmental cost of fertilizers. Different assumptions regarding these methods lead to results ranging from a 36% drop in emissions following the switch to ethanol to a 29% increase. So, although corn-based ethanol may help the US reduce its dependence on oil from an outside source, it does not appear that it will contribute that much to stopping global warming, unless the production of the biofuel is cleaner.

But the calculation varies considerably when the source of the ethanol is not the sugar in corn but cellulose from woody plants, such as poplar or millet. Fermenting corn to obtain ethanol requires heating with the help of mineral fuel, and in contrast, the producers of alcohol derived from cellulose heat the sugars in the plant by burning lignin, which is part of the organic material in that plant that cannot be fermented. The burning of lignin does not add greenhouse gases to the atmosphere, as the emissions are offset with the carbon dioxide absorbed by the plants used to produce the ethanol during their growth. Replacing gasoline with cellulosic alcohol can therefore cut 90% or more of greenhouse gas emissions.

Another promising biofuel is known as "green diesel". Researchers produced it by turning some of the biomass into gas (gasification), that is, heating organic material so that it emits hydrogen and carbon monoxide, and then converting these compounds into long-chain hydrocarbons in a chemical process called the "Fischer-Tropsch process" (during World War II, German scientists used the method This is for making synthetic motor fuels from coal). The result is a liquid fuel for motorized vehicles, with economic viability, that will add almost no net addition of greenhouse gases to the atmosphere. The oil giant Royal Dutch/Shell is currently researching this technology.

 

The need for R&D

Renewable energy sources, as attractive as they may be, are now generally marginal sources. However, we are now at or near the turning point, that is, at the critical stage where research, investment and access to the market will allow the suppliers of this energy to make a real contribution to the local and global energy supply. At the same time, vigorous policies are being established around the world designed to open the market to renewable energy sources, at municipal, political and governmental levels. Governments have adopted such types of policies for a variety of reasons: to promote market diversification or energy security, to strengthen industry and add jobs, as well as to protect the environment at the local and global level. More than 20 states in the US have adopted standards that set a minimum threshold for the proportion of electricity that will be provided through renewable sources. Germany plans to produce 20% of its electricity from renewable sources by 2020, and Sweden plans to completely give up the use of fossil fuels.

Even the President of the United States, George W. Bush, said in his famous speech to the nation in January 2006, that the USA is "addicted to oil". Although Bush did not discuss the connection between this addiction and global warming, almost all scientists agree that humanity's addiction to fossil fuels is destabilizing the global climate. The right time to act is now, and we finally have the tools to change the energy production and consumption processes, in ways that will benefit both the economy and the environment. However, over the past 25 years, public and private funding for research and development in the US energy sector has dwindled. Between 1980 and 2005, the rate of US spending on R&D (research and development) in the energy sector dropped from 10% to 2%. The annual public funding for R&D in the energy field dropped from 8 billion to 3 billion dollars (according to the dollar exchange rate in 2002). Private R&D decreased from 4 billion to only XNUMX billion dollars (see figure on the next page).

In order to observe these declines in the right perspective, one must take into account that in the early 80s the American energy companies invested more in R&D than the pharmaceutical companies, while today the investments of the energy companies are ten times lower. The total private R&D funding in the entire US energy sector amounts to less than the R&D funding of a single biotechnology company (Amgen, for example, spent $2.3 billion on R&D in 2005). And as the investment in R&D dwindles, the innovations in the field also dwindle. For example, at the same time as the decrease that occurred in the last quarter of a century in R&D funding regarding solar cells and wind energy, the number of patents successfully registered in these areas also dropped. The lack of attention to long-term planning and research has significantly weakened the US's ability to respond to the challenges posed by climate change and disruptions in energy supply.

Today there are widespread calls for large commitments to R&D in the field of energy. A study conducted by the US President's Committee of Advisors on Science and Technology Affairs in 1997, and a report published by the US Interpartisan Committee on Energy Policy in 2004, both recommend that the US government double its spending on R&D in the energy field. But will such doubling be enough? probably not. My research group made a calculation, based on estimates of the cost of stabilizing the amount of carbon dioxide in the atmosphere, and on additional studies that evaluate the degree of success of R&D programs and the savings that will be created as a result of the technologies that will be achieved as a result, and found that public funding of 15 billion to 30 A billion dollars a year, that is, five to ten times the amount allocated today.

Greg P. Nemet, a PhD student working in my lab, and I have found that it is possible, approximately, to compare an increase of this magnitude to the increases required during previous federal R&D initiatives, such as the Manhattan Project (to develop the atomic bomb) or the Apollo program (to land a man on the moon). , each of which produced clear financial gains, apart from meeting the goals. Even if the American energy companies increase their R&D budget tenfold, the amount will still be lower than the average for the entire American industry. Although government funding is essential for supporting technologies in their infancy, R&D in the private sector is a key factor in sifting through the weeds regarding new ideas and reducing barriers to commercialization.

However, increasing spending on R&D is not the only way to make clean energy a national priority. The ability of educators at all levels, from kindergarten to colleges, to stimulate public interest and activity, if they learn about the effects of energy use and production on the natural and social environment. Non-profit organizations can organize a series of competitions that will award a prize to the first company or private group to achieve a challenging and worthy energy-related goal, such as building a building or device that supplies energy to itself, or developing a commercial vehicle that can travel 85 kilometers using a single liter of fuel. It will be possible to plan such competitions according to the model of the "Ashoka" awards for public policy pioneers, or the "Ansari X" award for space vehicle developers. Scientists and entrepreneurs will also be able to concentrate on finding clean and economical ways to meet the energy needs of people in developing countries. My colleagues and I, for example, recently detailed the environmental benefits of improving cooking stoves in Africa.

But perhaps the most important step towards a sustainable energy economy is the introduction of market-based programs that aim to incorporate the social cost of carbon fuels into their prices. The use of coal, oil and natural gas has a huge collective price that society pays in the form of health expenses for diseases caused by air pollution, military expenses to secure the supply of oil, environmental damage from mining and the potentially devastating economic effects of global warming. A tax on carbon emissions would be a simple, logical and transparent way to give an advantage to renewable and clean energy sources, over sources that are harmful to the economy and the environment. The income from the tax could be used to finance part of the social costs of carbon emissions, and part of it would be dedicated to compensating low-income families who spend a large portion of their income on energy. In addition to this, the taxation can be combined with a cap and trade plan, which will limit carbon emissions, but also allow the cleanest energy providers to sell emission permits to their polluting competitors. The US government has already used such programs with great success, which are designed to cut emissions of other pollutants, and some Northeastern US states are already experimenting with trading in greenhouse gas emissions.

Such measures will give the energy companies enormous financial incentives to promote the development and commercialization of renewable energy sources. Bottom line - the US has an opportunity to embrace a whole new industry. The threat posed by climate change can be used as a lever for the clean energy revolution, a revolution that will strengthen the US manufacturing base, create thousands of jobs and cover its international trade deficits. Instead of importing oil from foreign countries, the US could export vehicles, appliances, wind turbines and highly efficient solar cells. Such a metamorphosis could transform the US energy sector into what was once thought impossible: a vibrant, sustainable and environmentally friendly engine of growth.
 Overview
Thanks to technological progress, renewable energy sources will soon be able to make a significant contribution to global energy.
To speed up the transition, the US must greatly increase its spending on energy R&D.
In addition, the US should impose a tax on carbon, which would give an advantage to energy from clean sources over energy from sources that are harmful to the environment.

Growing up fast, but still a baby
Solar cells, electricity generated from wind energy and biofuels are quickly gaining a foothold in the energy markets, but they are still marginal compared to fossil fuel sources such as coal, natural gas and oil.

 

The breakthrough of the renewablesSince the year 2000, the commercialization of renewable energy sources has gained tremendous momentum. Production of solar cells (also known as photovoltaics) jumped 45% in 2005. The construction of new wind farms, especially in Europe, increased the capacity to produce electricity from wind energy in the world tenfold during the previous decade. The production of ethanol, the most common biofuel in the US, soared to 36.5 billion liters last year, and most of it was distilled from corn grown in the US.

 

The onslaught is forwardThe renewable energy providers must overcome several technological, economic and political challenges before they can challenge the mineral fuel providers. For example, solar cell prices must rise and fall so that they can compete with coal-burning power plants. Wind farm developers must deal with environmental issues and local opposition. Among the other promising renewable sources are generators powered by geothermal steam as well as power plants that burn biomass, i.e. wood and agricultural waste.

 

Heat energy from mirrorsSolar heat systems, which are already used to supply hot water to homes and factories (like solar boilers), can also generate electricity. Since these systems generate electricity from the sun's heat and not from sunlight, they avoid the need for expensive solar cells.

 

The solar concentratorA solar heat array consists of thousands of plate-shaped solar concentrators, each of which is connected to a Stirling engine, which converts heat into electricity. The mirrors of the solar concentrator are arranged to focus the sunlight reflected from them on the receptor of the Stirling engine.

 

Stirling engineAn efficient Stirling engine does the work by flowing a substance, such as hydrogen gas, between two chambers (a). A regenerator separates the cold cell (in blue) from the hot cell (in orange). and maintains the temperature differences between the cells. The solar energy, received in the collector, heats the gas in the hot cell, so that it spreads and moves the hot piston (b). The piston changes direction and pushes the hot gas into the cold chamber (c). As the gas cools, the cold piston can easily compress it, and so the cycle can start over (d). The movement of the pistons drives a turbine that generates electricity with the help of an alternator.

 

About the author

Daniel M. Kammen is a Senior Professor, Class of 1935, at the University of California, Berkeley, where he holds various positions in the Energy and Resources Research Group, the Goldman School of Public Policy, and the Department of Nuclear Engineering. He is the founding director of the Laboratory for Renewable and Adequate Energy, and co-director of the Berkeley Environmental Institute.

 

charge the hybridThe environmental benefits of biofuels would be even greater if they were used to fuel plug-in hybrid electric vehicles (PHEV). Similar to normal hybrid cars, which combine gasoline and electricity, these cars and trucks combine an internal combustion engine with an electric engine, to maximize fuel consumption. The difference is that plug-in hybrid cars have larger batteries, and have a plug that can be plugged into the mains to recharge them. These vehicles are able to travel on electricity alone for short trips. On longer trips, when the battery gets weak, the combustion engine comes into action. This combination can significantly improve fuel consumption: the fuel consumption of a normal family car today is about 15 km per liter and normal hybrid cars, such as the Toyota Prius, average 20 km per liter, and in contrast a plug-in hybrid car can reach 35 to 70 km per liter. Oil usage is further reduced if the plug-in hybrid car runs on biofuel blends, such as 85E, a mixture of 15% gasoline and 85% ethanol.

If the entire US car fleet were replaced overnight with plug-in hybrid cars, oil consumption in the country would drop by 70% or more, so the need to import oil would completely disappear. The transition could have had far-reaching consequences for the preservation of the Earth's fragile climate, apart from the elimination of smog. Since most of the energy would have come to the cars from the electric grid and not from the fuel tanks, the environmental damage would have been concentrated in a few thousand power plants, instead of hundreds of millions of vehicles. Such a transition would focus the climate preservation challenge solely on the task of reducing greenhouse gas emissions from electricity production.

Plug-in hybrid cars could also bring relief to the American auto industry. Instead of continuing to lose market segments to companies from other countries, American car manufacturers will be able to return to competition if they upgrade their factories to produce plug-in hybrid cars, which save much more fuel than the non-plug-in hybrid cars produced by the Japanese. The power stations will also benefit from the transition, because most owners of plug-in hybrid cars will charge their vehicles at night, when electricity is cheaper, thus balancing the peak and trough times of electricity consumption today. In California, for example, replacing 20 million conventional cars with plug-in hybrids would increase electricity consumption at night to a level close to daytime consumption, which would improve the use of the electric grid and power plants, many of which are on strike at night. Also, electric cars that will not be used during the day will be able to supply electricity to the local power grid during peak hours. The inherent advantages of this for the electric industry are so magical that the electric companies may want to encourage the sales of plug-in hybrid cars by offering lower electricity prices to charge the car's batteries.

And most of all, plug-in hybrid cars are not exotic vehicles from the distant future. Daimler-Chrysler has already launched a prototype of a plug-in hybrid car, a version of the Mercedes-Benz Sprinter van, which consumes 40% less fuel than the traditional model. The plug-in hybrid cars will be even more economical when new technologies improve the energy density in the batteries, so that the vehicles can travel greater distances using only the battery. [See: "Hybrid Cars Gain Speed", Joseph J. Rome and Andrew A. Frank, Scientific American Israel, October-November 2006]

 

R&D is the key
Spending on research and development (R&D) in the US energy sector has been steadily declining since its peak in the 80s. Research on patenting activity shows that the decrease in funding has slowed down the development of new technologies in the field of renewable energy. For example, the number of applications submitted for registration of patents in the field of solar cells and electricity produced from wind fell with the decrease in spending on R&D in this field.

 The least bad mineral fuel

Although renewable energy sources are the best way to radically reduce greenhouse gas emissions, generating electricity from natural gas instead of coal can significantly reduce the amount of carbon emitted into the atmosphere. Coal-burning power plants emit 0.25 kg of carbon for every kilowatt-hour of electricity they produce (more advanced coal-burning power plants emit 20% less carbon). But natural gas (which contains mostly methane, CH4) has a higher ratio of hydrogen to carbon than coal. A power plant that burns natural gas in a combined cycle emits only 0.1 kg of carbon per kilowatt-hour (see graph).

Unfortunately, the dramatic increase in the use of natural gas in the US and other countries has led to an increase in the price of gas. In the last decade, natural gas was the energy source from mineral fuel that grew at the fastest rate, and it currently provides almost 20% of the electricity in the US. At the same time, the price of natural gas has risen from an average of $2.5 to $3 per million BTU (British Thermal Units) in 1997, to more than $7 per million BTU today.

The price increases in 2003 were so alarming that Alan Greenspan, then chairman of the Federal Reserve Board, warned that the US was facing a natural gas crisis. The initial solution proposed by the White House and some members of Congress was to increase gas production. The 2005 Energy Policy Decree included extensive subsidies to support gas producers, increased exploration and expanded imports of liquefied natural gas. However, it is possible that such measures will not be able to increase energy security, since most of the liquefied natural gas will come from some OPEC countries that supply oil to the USA. Moreover, electricity generation even from the cleanest natural gas will still emit too much carbon, if we intend to keep the level of carbon dioxide in the atmosphere below a concentration of 450 to 550 parts per million by volume (higher levels could be destructive for the Earth's climate). It will take less time, and it will also be cheaper and cleaner, to improve energy efficiency and develop renewable sources, and this will also give the US greater energy security than developing additional natural gas supplies. Electricity from a wind farm costs less than electricity produced in a natural gas power plant, if you take into account the total cost of building the power plant and expected gas prices. Also, wind farms and solar arrays are built more quickly than a large power plant operating on natural gas is built. And the most decisive factor: the diversification of US energy sources is the most important factor in maintaining a competitive and innovative energy sector. So encouraging renewable sources makes sense even if we take into account only the economic benefits and ignore the environmental benefits.

 

And more on the subject

Reversing the Incredible Shrinking Energy R&D Budget. DM Kammen and GF Nemet in Issues in Science and Technology, pages 84–88; Fall 2005
Science and Engineering Research That Values ​​the Planet. A. Jacobson and DM Kammen in The Bridge, Vol. 35, no. 4, pages 11–17; Winter 2005
Renewables 2005: Global Status Report. Renewable Energy Policy Network for the 21st Century. Worldwatch Institute, 2005
Ethanol Can Contribute to Energy and Environmental Goals. AE Farrell, RJ Plevin, BT Turner, AD Jones, M. O'Hare and DM Kammen in Science, Vol. 311, pages 506–508; January 27, 2006

All these articles can also be found online at:

http://rael.berkeley.edu/publications