Not Just Hot Air: Geothermal Power
by Kealy Devoy -- April 14th, 2012
After a long and winding drive we arrived at the Northern California Power Agency’s (NCPA) geothermal power plant, nestled in the Mayacamas Mountains. The site – Geysers geothermal field – is the largest geothermal site in the world. Beneath the surface, unique geological formations produce super heated steam. The NCPA pumps this super heated steam to the surface and through a turbine, which generates electricity. This system is far more efficient than more common geothermal power plants because it uses steam directly instead of flashing hot water into steam to power the turbine.
This in itself is cool, but the NCPA goes far beyond just generating electricity from natural heat. They have implemented innovative programs to make their whole operation more sustainable. Murray Grande was on hand to give us the run down of the plant’s history.
First, the plant output peaked in the late 1980s, which caused the pressure in the wells to decline. Instead of just abandoning the project, the NCPA modified the turbine to operate at a lower inlet pressure so that the steam coming from the wells was still usable.
In the mid- to late-1990s, the town in the valley below the plant was having trouble dealing with their wastewater. The NCPA saw an opportunity to use the town’s treated wastewater at the plant, reducing their need to use municipal water. The NCPA set up a series of pumps to get the water up to the plant, and then installed two 1MW solar arrays to run the pumps. The treated wastewater is injected into special wells drilled into the rock so that the geological formation can heat that water into steam for use in the plant. This project reuses what was formerly a waste product, reduces municipal water use, and helps the plant get more out of the existing rock formation.
The NCPA is always on the lookout for projects that will help them continue to provide reliable, clean energy to their consumers. Their commitment to clean energy is clear, and so far it’s paying off.