The Department of Energy (DOE) has granted $375 million to fund three new Bioenergy Research Centers to develop technology for cellulosic ethanol and other biofuels. The DOE also plans to spend $385 million over the next four years, working with commercial partners, to build six pilot plants to produce ethanol from cellulose. Even so, significant progress is not assured. Tim Donohue, a bacteriologist at the University of Wisconsin–Madison, put it this way: “I equate what we're doing to society saying, ‘We're going to the moon,’ or ‘We're going to sequence the human genome.’ To me, this is a critically grand scientific mission that we're just setting off on today.”521 Clearly, biofuels are not a panacea for the world's energy ills.
Hydroelectric
The second area of unrealistic expectations is renewable energy for generating electricity, mostly in the form of hydro-power, geothermal, wind and solar. The world's primary sources of energy are depicted in Illustration 150. Hydroelectric plants supply about 715,000 megawatts (MW), some 19% of total world electricity generation. Hydro is also the largest renewable source of electricity at this time, making up 64% of the total renewable non-carbon portfolio. Hydroelectric power plants convert the kinetic energy contained in falling water into electricity. The Sun evaporates water from the ocean, which condenses into water at higher elevations. The energy in flowing water is ultimately derived from the Sun and is constantly being renewed.
Illustration 150: World sources of energy ca. 2004, Source The Economist.
The largest hydro producing nations are China, Canada, Brazil, the United States, Russia and Norway. Currently, the largest hydroelectric power station is the Three Gorges Dam in China, with a projected maximum capacity of 22,500 MW. The largest plant in the US is Grand Coulee Dam in Washington state, with a capacity of 6,800 MW. While the generation of electric power from flowing water generates no pollution, large dams can have a significant environmental impact. Habitat is lost under the water of dam-created reservoirs, fish migration paths can be blocked, and the natural renewal cycles of rivers downstream are disrupted. Water exiting a hydroelectric turbine usually contains little suspended sediment, which can lead to scouring of riverbeds and riverbanks. Large dams can cause environmental problems both upstream and downstream.
The expansion of hydroelectric power from fresh water sources is limited by geography and the balancing of environmental and human concerns. There are those who advocate small-scale hydro-power plants that would provide electricity for a cluster of houses or a village. While this is a worthwhile solution where conditions permit, care must be taken when relying on hydro-power from small sources. This is due to the fact that smaller water sources may prove to be seasonal or highly variable over a period of years.
For example, in Peru, home to 70 percent of Earth's tropical glaciers, the glaciers in the Andes mountains have lost at least 22% of their area since 1970. According to Peru's National Resources Institute, the melting is accelerating. This threatens not only fresh water supplies but also hydroelectric plants that generate 70% of Peru's power.522 Expanding hydro-power greatly is not possible and what is achievable in the short-term, may not be prudent in the long-term.
Geothermal
Another area of suggested expansion is electrical generation and, to a lesser degree, heating from geothermal sources. Taking advantage of the natural internal head of Earth's molten interior is a great idea, if you have access to such a heat source. It is a non-polluting, renewable and long-lasting energy source. Geothermal energy is generally harnessed in areas of volcanic activity. The Pacific Ring of Fire is a prime spot for the harnessing of geothermal activity because of significant tectonic activity (see page 138). Other areas, such as Iceland, Italy and around America's Yellowstone Park, have abundant supplies of geothermal energy.
Geothermal energy can be produced by drilling a well into the ground where thermal activity occurs. Once a well has been sunk and a well-head attached, energy can be extracted by injecting water into the ground and collecting the resulting steam and hot water, which can be used for heating or running a generator turbine.
According to the US Bureau of Land Management, the production of steam and hot water from 22 producing geothermal leases on public lands generated over 4.1 billion kilowatt-hours of electricity in 2005; enough for over 500,000 people. Royalties associated with this level of production totaled over $12 million dollars.523 Most of this takes place in California. In the US, the potential of geothermal energy has been estimated as high as five times the current total use of electricity. Such estimations are theoretical, and current technology does not come close to allowing such levels of generation.524
As of 1999, 8,217 MW of electricity were being produced from 250 geothermal power plants in 22 countries around the world. One of the advantages that geothermal generation has over wind and solar power is the ability to run day and night. These plants provide reliable power for over 60 million people, mostly in developing countries. The top ten producers in 1999 are listed in Table 10.
Table 10: Top 10 producers of geothermal energy in 1999. Source GEO.
Currently, this method of energy production can only be used where there is significant thermal activity close to the surface. Though geothermal reservoirs as deep as two miles (3.2 km) have been tapped by drilling wells, this still leaves geothermal as a niche player in the overall renewable energy game.
Wind Power
The current star of the renewable energy stage is wind power. During the 1970s, wind turbines produced around 200-300 kW of energy each at a cost of around $2 per kWh. Today, large turbines produce up to 2.5 MW each at a cost of 5-8 cents per kWh. In comparison, electricity generated by a coal plant costs 2-4 cents per kWh.525 How much potential energy is there in wind? In a study published in the Journal of Geophysical Research, global wind power potential for the year 2000 was estimated to be ~72,000 GW (gigawatt). According to the study: “Even if only ~20% of this power could be captured, it could satisfy 100% of the world's energy demand for all purposes and over seven times the world's electricity needs, 1.6-1.8 TW (terawatt).”526 But much like geothermal energy, wind power's potential cannot be realized in the real world.
There are problems with wind power that make its widespread use much less attractive. Some areas do not have sufficient wind to make installing turbines viable. Wind generators are practical where the average wind speed is 10 mph (16 km/h) or greater. Even in areas with high enough average wind speeds, fluctuations can limit generation. Too little breeze means no power, while strong winds can force the turbines to shut down to prevent damage. Most wind farms achieve, on average, only 30% of their full capacity. Worse, from a power grid management point of view, is that output can fluctuate by up to 20% of the total national wind capacity in the space of a single hour.527 In America, there are many areas where wind generation is not cost-effective or practical, including large portions of the south (see Illustration 151).
Illustration 151: U.S. wind potential—lighter areas have less potential. Source U.S. National Renewable Energy Laboratory.
Because of these limitations for ground-based wind turbines, a number of proposals have been made to elevate the problem. Among the more ambitious ideas for expanding wind power is a suggestion to loft huge flying generators, a cross between a kite and a helicopter, into the perpetual winds of the jet-stream, six miles above the ground.528 The idea is being developed by Sky WindPower, a company based in San Diego, California. According to Ken Caldeira, a climate scientist at the Carnegie Institution, harvesting just 1% of the jet-stream's energy would produce enough power for everybody on the planet. Aiming a bit lower, a Canadian company called Magenn Power has proposed wind generators filled with helium. Spinning around its horizontal axis, like an airborne water mill, the generators would fly at altitudes up to ½ mile (1 km). Other proposals include arrays of giant kites and similar, far-fetched ideas.
Beyond the physical and engineering problems, wind farms are running into increasing opposition from the
public, a form of the NIMBY (not in my back yard) phenomenon. In Britain, the Economist reports: “Wind power, once seen as the eco-friendly cure-all for Britain's energy problems, is attracting unprecedented criticism. The latest campaign, which unites veteran Greens and the opposition Tories, opposes a proposed installation of 27 wind turbines next to Romney Marsh in Kent, a noted bird sanctuary and beauty spot.”529 The truth of the matter is that large wind farms are ugly, despoiling the natural beauty of the landscape and endangering local bird populations. In many highly populated regions, wind farms are simply not acceptable. For this reason, many proposed wind farms are to be built in offshore waters.
Locating wind turbines at sea raises the cost of power generation by as much as 50%, but this disadvantage can be offset by more reliable wind. Offshore saltwater environments can also raise maintenance costs by corroding the towers. Repair and maintenance are usually much more difficult, and more costly, than for onshore turbines. Offshore saltwater wind turbines must be outfitted with extensive corrosion protection measures like coatings and cathodic protection, helping to raise the cost of power generation. Though building offshore doesn't compete with local people or wildlife for land use—and partially hides the unsightly windmills—offshore wind farms have run afoul of public opinion.
One area that is a prime candidate for installation of an offshore wind farm is off Cape Cod, in Massachusetts. The location is one of America's prized resort areas, including such vacation destinations as Cape Cod, Martha's Vineyard and Nantucket—all playgrounds for the wealthy and powerful. The proposed Cape Wind Energy Project, on Horseshoe Shoals in Nantucket Sound, would be America's first offshore wind farm, and would provide 74% of Cape Cod's energy needs with clean, ecologically acceptable power. Though the turbines would be hard to see except on very clear days, and even then, they'd be tiny objects on the horizon, wealthy landowners have bitterly opposed the project.
Leading the opposition to the proposed wind farm are such environmental notables as former CBS news anchor Walter Cronkite, US Senator Ted Kennedy, and his nephew Robert Kennedy, a lawyer for the Natural Resources Defense Council (NRDC). Both the NRDC and Greenpeace strongly back the project.530 Support for environmental issues evidently evaporates when landowner's property values or the scenic views from their homes are threatened. In the face of this formidable opposition, the project seems to be going ahead, recently gaining authorization from the Massachusetts secretary of environmental affairs.531
The fact that wind power, one of the greenest and most advanced renewable energy technologies, can encounter such stiff resistance from people who are supposedly pro-environment, is an indication that the potential of these sources of energy may never be fully realized. This is not a reason to give up on building wind farms—just practical recognition that overly enthusiastic projections for any alternate energy technology should be viewed cautiously.
Solar Power
The last of the major renewable technologies mentioned in the IPCC reports is solar energy. In 2001, solar electricity provided less than 0.1% of the world's electricity. The potential energy present in sunlight is tremendous—after all, the source of energy for all life on Earth and the planet's climate comes from the Sun. More energy strikes the Earth as sunlight in one hour than all the energy consumed by people in a year. According to the US DOE, America could supply its entire energy needs by covering 1.6% of its land area with solar cells. For comparison, the required land area is about 10 times the rooftop area of all single-family homes and is comparable with the land area covered by the nation's federal highways.532
Because of day/night and time-of-day variations in insolation and cloud cover, the average electrical power produced by a solar cell over a year is about 20% of its production rating. Solar cells have a lifetime of approximately 30 years and, though they incur no fuel expenses, they do involve initial capital cost. The cost of electricity produced by solar cells is calculated by amortizing the capital cost over the lifetime of the cells. The electrical output produced diminishes over the cells lifetime, further increasing overall cost.
Unfortunately, even though there have been major advances in solar energy technology in recent decades, solar is a far less mature technology than those already mentioned. The efficiency of photovoltaic (PV) cells has increased from 6% when they were first developed to around 15%. Their cost has dropped from around $20 per watt of production capacity in the 1970s to $2.70 in 2004.533 But that progress has not made solar cells even remotely competitive with wind or fossil fuels. Today, a 2-kilowatt capacity PV system in Tucson, Arizona, would generate about 9.4 kilowatt hours (kWh) per day, a similar size unit in New York would produce 6.2 kWh. A PV system connected to the local power grid costs about $7,000 to $10,000 per kW of capacity, before incentives.534
Though solar cells are the most visible means of harvesting energy from the Sun, there are other technologies available. Many residential and commercial buildings use solar energy for heating water. Other commercial installations have been built to generate electricity without using expensive PV technology. Concentrating Solar Power (CSP) uses reflectors to focus and concentrate sunlight on a specific point to boil water. The mirrors may take the form of troughs, parabolic dishes or multiple flat mirrors. The concentrated sunlight produces steam, which is used to spin turbines driving electrical generators. The most complicated part of this type of system is the mirror tracking control, which must slowly move the reflectors to keep them aimed at the Sun. The heat from excess steam can also be used to desalinate water or heat buildings. Another advantage CSP has over photovoltaic cells is that a CSP plant can continue generating power for several hours after sunset using stored thermal energy.
The largest solar power plant in the world has been operating in the Mojave desert of California since the mid-1980s. Containing 400,000 mirrors, covering a total area of 4 square miles (10.3 km2), it is capable of generating 354 MW of electricity, enough for 900,000 homes. More plants are planned for America's desert southwest. One new CSP plant in Nevada will generate electricity for an estimated 17 cents per kWh.
The US Department of Energy (DOE) published a report in 2005 that identified 13 priority research directions with the “potential to produce revolutionary, not evolutionary, breakthroughs in materials and processes for solar energy utilization.”535 The report's overly enthusiastic tone cannot hide the fact that most of the technologies discussed are highly speculative. The report notes that progress in the proposed research could lead to: artificial “molecular machines” that turn sunlight into chemical fuel; “smart materials” based on nature's ability to transfer captured solar energy with no energy loss; self-repairing solar conversion systems; devices that absorb all the colors in the solar spectrum for energy conversion, not just a fraction; far more efficient solar cells created using nano-technology; and new materials for high-capacity, slow-release thermal storage.
Illustration 152: World electricity generation. U.S. EIA.
The report further notes that revolutionary breakthroughs come only from basic research and that, “We must understand the fundamental principles of solar energy conversion and develop new materials that exploit them.” Solar remains hundreds of times more expensive than other sources and, barring “revolutionary breakthroughs,” will not be a major factor. Basing future energy, economic and environmental policy on revolutionary breakthroughs is like basing a retirement plan on winning the lottery.
The bottom line on renewable energy? We should maximize its use where it makes economic and environmental sense. But, as we saw, biofuels cannot replace fossil fuels and, when it comes to generating electricity, renewables hold little hope. The US DOE estimates that 0.007 TW536 will be available from solar by 2020. The United Nations estimates that the remaining global, practically exploitable, hydroelectric resource is less than 0.5 TW. The cumulative energy in all the tides and ocean currents in the world amounts to less than 2 TW. The total geothermal energy at the surface of the Earth, integrated
over all the land area of the continents, is 12 TW, of which only a small fraction could be practically extracted. The total amount of globally extractable wind power has been estimated by the IPCC to be 2-4 TW.
All these clean, renewable sources of energy would not satisfy the world's current appetite for power, roughly 13 TW of continuous energy consumption in 2005. Based on current growth (see Illustration 152), world energy consumption is projected to more than double by 2050. Further, demand will more than triple, exceeding 46 TW, by the end of the century.
Coal's False Promise
Much attention is being given to a non-renewable resource that many countries have in abundance—coal. Currently, coal is one of the major contributors to both greenhouse gas emissions and more traditional air pollution, so how can coal be the fuel of the future? This hope all hinges on an experimental and mostly non-existent technology called “carbon sequestration.”
Carbon sequestration is the capture and storage of carbon dioxide and other greenhouse gases that would otherwise be emitted to the atmosphere. The greenhouse gases are to be captured at the point of emission. The captured gases can be stored in underground reservoirs, dissolved in deep oceans, converted to rock-like solid materials.
At present, the state-of-the-art technology for existing power plants is limited to “amine absorbents.” Amines are organic compounds that contain nitrogen as a key atom. Structurally, amines resemble ammonia (NH3) with one or more of its hydrogen atoms replaced by an organic molecular group. It is from such a nitrogen-based group that amino acids, the building blocks of protein molecules, get their name. Amines are used extensively in the petroleum refining and natural gas processing industries. The process works as follows:
The Resilient Earth: Science, Global Warming and the Fate of Humanity Page 36
