Large-Scale Green Power: An Impossible Dream?
Chasing after windmills and photovoltaics could well be the stuff of fiction.
Wind and solar cells (photovoltaics or PVs) are two renewable energy technologies that many hope will eventually provide the United States with massive amounts of clean, sustainable electric power for the indefinite future. Indeed, it is often suggested or implied that the United States can look to a future where most, if not all electric power can be provided by wind and photovoltaics [1, 2]. But careful analysis shows that will not be possible unless consumers are willing to pay five to 10 times what they pay for electricity today.
Both wind and sunlight are unpredictable and intermittent. The wind blows at different speeds at different times in different places. Sometimes the air hardly moves. Sunlight is available only in the daytime; it is weak in the morning and late afternoon and is dramatically reduced by cloudiness, which is location-dependent and unpredictable. That's nature, as we all know from our everyday experience.
On the other hand, the public requires electricity on demand, which requires dispatchable electric power generators. Lights must go on when the switch is flipped, the computer must start and operate steadily on demand, etc. Very few people would be willing to operate their homes or businesses only when the sun shines or the wind blows. So the question becomes one of how to accommodate the inherent mismatch between what we demand in electric power availability and what nature provides in light and wind, which are inherently not dispatchable [3, 4, 5].
Both wind and photovoltaics are currently too expensive in today's marketplace for widespread commercial application, so large sums are being invested in research and development and government subsidies. In the near-term, investors are building government subsidized and/or mandated wind farms that are capable of providing modest but useful amounts of electric power, which is absorbed on our large, complex, interconnected electric power grids. That arrangement has been demonstrated to be operable, but the economics are not what they appear to be, because the impact on the rest of the grid is not often calculated nor made public.
Investigating the Promise of Large-Scale, Baseload Solar Electricity
Consider a future time when wind and photovoltaics might conceivably provide a major fraction of the nation's electric power needs. Two major paths emerge that could provide large-scale electric power-on-demand. (By large-scale we mean a major fraction of U.S. electric power consumption-say many tens of percent). The first path involves the use of energy storage to bridge the gap between our requirement for power-on-demand and the intermittence of wind and photovoltaics [6, 7]. The second involves the use of wind or photovoltaics in combination with a conventional gas or coal power plant that together could supply electricity-on-demand when wind or sunlight diminishes or simply is not available.
In most of today's applications of photovoltaics, which are comparatively small-scale, energy storage (often batteries) is used to bridge the no- or low-sunlight gaps . Applications include the supply of electricity to remote locations for water pumping, vaccine refrigeration, communication, warning lights, beacons and