Mixing Solar with Coal to Cut Costs - Technology Review

A project that will add solar power to a coal-fired power plant could reduce the amount of coal required to generate electricity and dramatically cut the cost of solar power.

The approach, announced by Abengoa Solar, based in Lakewood, CO, and Xcel Energy, Colorado's largest electrical utility, would make it easier for utilities in sunny states like California to meet impending state renewable-energy requirements.

The project will involve building an array of parabolic mirrors designed to concentrate heat from the sun, and using that heat to help make the steam that drives the coal plant's turbines and generators, making electricity. Such mirrors have been used for decades to generate electricity at stand-alone concentrated-solar power plants, also called solar-thermal plants, which arecurrently the cheapest source of solar power. But pairing the concentrating mirrors with a coal power plant offers a way to make this type of solar power even cheaper because a large part of the cost of a solar-thermal plant is the equipment for converting heat into electricity. The Abengoa Solar project will use existing boilers, turbines, generators, and so on, reducing this cost.