Demand for electricity, a cornerstone of modern society, accounts for about 39 % of all energy use in the United States, even though electricity accounts for 30% of the energy used for heating. Electricity demand doubled from 1970-2000 and is on pace to increase another 20% by 2009. We expect electricity to be highly reliable, affordable, and secure, made more difficult because it must be used immediately at industrial levels; unlike the water supply, it can’t be stored. The key to success turns on providing power to supply demand precisely when consumers desire it, second by second. The goal is to forecast demand as accurately as possible, then assemble the most dependable, controllable supply in order to achieve confidant reliability, or capacity.
When gauging a power generator’s ability to perform, energy experts consider the machine’s design potential, then measure its actual performance over time while also assessing confidence in its availability for use during critical peak demand times, since heavy demand challenges the adequacy of supply. A power unit’s design potential is known as its rated or installed capacity, which is the average energy it should produce, usually over a year, if it worked at maximum without stoppage—expressed in thousands (kilowatts, kW) or millions (megawatts, MW) of watts. Engineers use the term capacity factor to project what percentage of its rated capacity a power plant will actually deliver over a specified time, since they realize no machine, for a variety of reasons, can function perpetually at full tilt. To express their level of confidence about a particular generator’s availability to produce as expected at whatever time it was needed, energy experts measure the unit’s capacity value or credit, again as a percentage of its rated capacity.
Conventional units must pass stringent tests for reliability and effectiveness. Generators that satisfy basic levels of demand, such as nuclear, large coal plants, and hydro, have capacity factors in the 90%+ range, with capacity values exceeding 99.99%. Smaller, more flexible units, such as natural gas, coal, or oil, which may be used only a few hours a year, may have capacity factors of as little as 5%, reflecting not the limitations of their potential so much as operator choice. When selected, however, their reliability produces a capacity credit in the range of virtual certainty.
Because of wind energy’s intermittency and relentless volatility, along with downtime for maintenance, the average national capacity factor for wind technology is about 25%; less than 1% of all wind plants achieve a capacity factor of 30%. The random, desultory nature of the wind, which rapidly changes energy levels at frequent intervals, limits what wind machinery can do, condemning wind turbines to intrinsically low capacity factors. The wind typically blows hardest at night, at times of least demand, and much less during the afternoon, at times of peak demand. And in
summer months, when demand for electricity is greatest, there is often no wind at all. The capacity credit for wind technology is in the low single digits—and often it is zero.
Chautauqua County has the wind potential to absorb about 500-2.0MW turbines, each more than 400 feet tall and spread over 100 miles, with a collective installed capacity of 1000MW. Annually, projecting a capacity factor of 25%, these might provide about 250MW of very sporadic and highly volatile energy to the state’s grid, which has an installed capacity of 37,500MW and a summer peak demand of 34,000MW. Their capacity value at any peak demand period will vary from zero to no more than 5% of their installed capacity, which means they can be reliably expected to contribute no more than 50MW to augment power at times when it is needed most. Given the way that dependable conventional generation must mix with the wind energy to balance and smooth its skittering activity, wind technology can neither supplant those units nor assure that it could abate significant levels of carbon dioxide emissions throughout the energy production/transmission system. No independent, transparent measurement has demonstrated system-wide CO2 emissions abatement due to wind technology anywhere in the world, largely because wind developers insist on the confidentiality of proprietary performance information.
Wishful thinking about any technology, particularly such massively intrusive technology as industrial wind, should be filtered through and tested against reality before it is unleashed throughout the countryside. Wind energy for the production of electricity is not new. Nearly 18,000 wind turbines exist in the United States, revealing enough evidence about their actual performance, despite proprietary efforts to conceal it, to derive informed decisions about its potential effectiveness in New York.
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