The utilities of the US, if not those in many other parts of the world, have pressing needs not just to supply power to energy-hungry consumers. But more than that they must meet both public and political pressures for using renewable energy sources. Apparently heedless of the impact to the environment of the Middle Kingdom and abroad, China commissions a new coal-fired plant every 5 days. Yet in the US there has not been a new coal-fired power plant permitted in about a year. So over time in North America, the older systems are passing away. The question is, what will take their place? To the extent that the public envisions renewable energy systems, the image it holds is of tall poles with windmill systems on top with blades turning. Or there is an expectation of solar systems mounted on rooftops, facing the sun. But these are intermittent sources of energy production. Some of the time - most of the time, really - the wind does not blow. And at least in the nighttime, the sun does not shine. So for each Megawatt of power that moves through the grid, down to meet the load, the requirement is for three megawatts of installed capacity of wind and solar. Build three, get one. In the big picture, this is not a good use of resources.

California's power shortage confirms that all of the hoopla over wind energy's credentials as a clean and renewable source of electricity is undercut by the reality of its unreliability. During an extremely hot week in August, when air conditioners were cranked up and the state was on the brink of rolling blackouts, how much help did the state get from its beloved 2,500 megawatts of wind power? Only 4 percent of its capacity, according to the California Independent System Operator, which is responsible for the state's electricity grid. Southern California Edison's 2,200 megawatts of wind capacity generated only 45 megawatts. In other words, wind energy works great — except when you need air conditioning.