Nearly all the energy on earth originated as radiation from the sun. Somewhere around 750,000 years ago, early humans discovered the vast quantities of solar energy stored in dried plant material, and fire became a source of supplementary heat and light. Then, as forests began to disappear in the 17th century, Europeans discovered another source of stored sunlight in fossil fuels. These represent the accumulation of solar energy over millions of years. Coal is the most abundant — we will probably never run out of it — and the octane molecules in gasoline are probably the densest storehouse of solar energy we will ever encounter. Pound for pound, coal contains twice as much energy as wood, and gasoline and natural gas contain four times as much. The Industrial Revolution became possible only when these denser forms of solar energy were developed.
Now, as we begin to run up against the natural limits of fossil fuels, it is important to consider the energy density of anything we might use in their place. Wind, water, biofuels, and the direct use of sunlight are anywhere from 5 to 50 times more dilute than fossil fuels. There is only one way to compensate for their low density, and that is to consume huge amounts of land in gathering them.
This is the Achilles heel of every form of “alternative energy.” When first introduced in the 1970s, alternative energy came with the slogan “Small is beautiful.” Prophets such as Amory Lovins, David Brower, and Lester Brown pictured a post-industrial world of backyard windmills, rooftop solar collects, and organic gardens where small plots would be set aside for biofuels that would run hyper-efficient cars. Self-sufficiency was the theme. It all sounded charming and romantic.
The reality has been anything but. We now use one-quarter of America’s corn crop for biofuels in order to replace less than 4 percent of our oil. GreenFuel Technologies, a Massachusetts startup, has a plan to grow photosynthesizing algae that will consume the carbon emissions from coal plants, and can be turned into biodiesel to run cars. It sounds like a great idea, except that the pools required for gathering sunlight to convert 40 percent of the exhausts from a single power plant will occupy 15 square miles.
T. Boone Pickens will soon be running up against a similar density problem with his wind farms. A standard wind farm built to generate 1,000 MW — the capacity of an average coal or nuclear plant — would occupy about 125 square miles. Pickens wants to space his windmills a little wider — five to the square mile instead of eight — so for his 4,000 MW he will need 800 square miles.
But that 4,000 MW is only the “nameplate capacity.” Because wind blows so irregularly, even the best wind farms now generate electricity at only 30 percent of their theoretical capacity. (By contrast, nuclear reactors run at 92 percent capacity.) That means he will need 1,200 square miles of windmills to equal the output of three or four coal or nuclear plants, each of which occupies only a square mile. Factoring in the land required for mining adds several square miles for coal, and much less for uranium.
Even then, the electricity generated by windmills is not what the industry calls “dispatchable,” meaning able to be produced and delivered when and where needed. As the authors of “20% Wind Energy by 2030” write:Incorporating wind energy into power system planning and operation, then, will require new ways of thinking about energy resources. . . . Thinking in terms of “backing up” the wind is not appropriate because the wind capacity was installed to generate low-emissions energy but not to meet load growth requirements. Wind power cannot replace the need for many “capacity resources,” which are generators and dispatchable load that are available to be used when needed to meet peak load.In other words, don’t count on its being there — backup from other resources will always be necessary. Building and maintaining a wind-power infrastructure is a supplement, not a replacement, for fossil-fuel plants.
Part of the mistaken belief that wind can be a reliable source of electricity comes from a misapprehension of what the “grid” is. The national grid is not a machine for churning out electricity. It is more like a high-wire act — the Flying Wallendas balancing six people on a bicycle 50 feet above the ground.
Electricity must be consumed the moment it is generated; there are no methods for storage on an industrial scale. This means that supply and demand must constantly match within about 5 percent. Otherwise there will be power “dips” or “surges,” which can cause brownouts, ruin electrical equipment, or even bring the whole system crashing down.
Traditionally, maintaining voltage balance has involved two things: (1) matching supply with demand through the normal daytime/nighttime fluctuations, with demand usually peaking around mid-afternoon, and (2) maintaining a “spinning reserve” against sudden losses of power, in case an overloaded transmission line brushes against a tree and shorts out, or a generator unexpectedly shuts down. Utilities generally build “peaking plants” to handle high daytime demand, then carry a “spinning reserve” of 20 percent of output to guard against shutdowns.
Now imagine introducing a power source that is constantly fluctuating. The output of a windmill varies with the cube of wind speed, so it can change greatly from minute to minute. Putting windmills on the grid is a little like the Flying Wallendas’ hiring a new crew member to shake the wire while they are doing their balancing act. Engineers who work on electrical grids have been quietly complaining for years, and over the last decade, grid operators in Denmark, Japan, and Ireland have all refused to accept more wind energy. In fact, Denmark — the world leader in wind generation — stopped building windmills altogether in 2007. After long discussions at numerous symposiums and in professional energy journals, a consensus has emerged that, even with very accurate weather forecasts and other improvements, a grid can at best tolerate a maximum of 20 percent wind energy. Above that, the fluctuations become too difficult to mask. That’s why DOE chose the 20 percent–by–2030 goal. . .
Oh, there’s one more rub. Bringing windmills online will require building a whole new cross-country transmission system. While wind energy is concentrated in the Midwest, consumer demand is mostly on the East and West Coasts. Normal transmission lines — of 138 kilovolts (kV) and 345 kV — lose about 10 to 15 percent of their wattage every 1,000 miles, which is not a problem when the power is generated close to the consumer. But transmitting electricity halfway across the country will require a completely new infrastructure of 765 kV lines that cover long distances without losing power. This could be an enormous problem, because utility executives now say the only thing more difficult than siting a power plant is building new transmission lines, since every property owner and municipal jurisdiction in the path gets to have a say. Ranchers who are as just as picky as Pickens about what they permit on their land could pose huge obstacles.
Tuesday, August 05, 2008
Why T. Boone Is Mostly Hot Air
William Tucker tilts at windmills, in the current National Review (subscription only for now):