How to turn coal plants into climate-solution machines

In addition to reducing costs and greenhouse gas emissions, EPRI believes that solar thermal technology could also boost coal and natural gas power enough in existing plants to eliminate the need for new infrastructure.

1. Look for a dirty coal plant located in an optimal place: (1) close enough to a zone suitable for the construction of a solar thermal plant; (2) close enough to a region that provides sustainably sourced biomass; (3) close enough to potential geosequestration sites. The first of these is a prerequisite; the other two are flexible choices, because both biomass as well as captured CO2 can be transported over fairly long distances.

2. Begin with co-firing torrefied biomass pellets. Torrefied biomass - a new kid on the green block - gives the fuel a higher energy density and allows it to be transported over much longer distances than ordinary biomass; it can be stored like coal without the need for new infrastructures; it requires less energy to be crushed than ordinary biomass but also than coal, and can make use of the same grinding infrastructures as those used for coal; torrefied biomass can be readily co-fired at very large fractions. Co-firing torrefied biomass is the most straightforward and affordable way to cut emissions from existing coal plants.

3. When this operation is up and running, add solar thermal steam. The biomass and coal would provide the baseload for the intermittent solar thermal energy.

4. Gradually increase the biomass fraction to a ratio higher than 50% of all the carbon used as fuel in the power plant. So we can keep using coal, but simply much less of it. Keep adding biomass and solar steam until emissions from this power plant begin to near zero. Victory is in sight. We have a carbon-neutral baseload power plant.

5. But carbon-neutrality is not enough. More important actions are still ahead. By now carbon capture and sequestration (CCS) technologies should be commercially viable, and carbon prices on the market should allow the technology to be implemented without pushing up costs too much. So we add a CCS infrastructure to our hybrid power plant. This CCS infrastructure would capture and store CO2 from biomass, and make the power plant carbon-negative, instead of merely carbon-neutral.