MorganEnergy

The greening of the USA’s generation industry took another significant step forward this week when the Colorado Public Utilities Commission approved a plan by Xcel Energy to replace 229MW of coal-fired generation with a 200MW solar plant. As reported by Rocky Mountain News, Xcel had originally planned to replace the aging coal plants (Arapahoe in Denver and Cameo in Gran Junction) with a 480MW gas plant. However, in the face of local opposition, and the need to meet Governor Bill Ritter’s plan for a 20% reduction in CO2 emissions by 2020, the utility will now use renewable generation instead.

While local fossil fuel interests are not best pleased with this development, the general sentiment in Colorado appears very positive. As this Washington Post article reports:

State leaders are thrilled with the economic benefits that have come with the hundreds of new research and manufacturing jobs in pursuit of alternative power.

Among the signs is the arrival of Vestas, a Danish wind turbine company, which announced Friday the construction of two more manufacturing plants and 1,350 new jobs, bringing the company’s total in Colorado to 2,450. ConocoPhillips announced this year that it will locate its alternative-fuels research operation in the state. The Colorado-based National Renewable Energy Laboratory is adding 100 jobs.

Of course you can’t just replace 229MW of coal generation with 200MW of solar, because the coal plant is capable of running baseload and the solar is not. You can’t make electricity from sunlight at night. So Xcel will also be building 850MW of wind generation. It is also looking at ways to store the output of the solar plant.

The chosen technology is concentrated solar, which uses mirrors to increase the amount of sunlight falling on the solar cells. In parallel with this Xcel hopes to build an energy storage system that will probably use molten salt. The “salt” (actually a mixture of sodium and potassium nitrate, which is chemically a salt but not the same thing as we put on our food) is heated to a temperature of 1,000 degrees Fahrenheit, and is apparently remarkably good at retaining that heat for use later. A more detailed explanation of the technology is available here.