Less than two weeks after celebrating the implementation of solar photovoltaic panels just outside its gates, Boulder’s Wastewater Treatment Facility (WWTF) reached a new milestone, going “off the grid” completely for two and a half hours on Thursday, Oct. 28. Going “off the grid” means that all power necessary to operate the facility came from sources other than Xcel’s traditional fossil fuel supply.

In this case, Coordinator of Wastewater Treatment Chris Douville explained, the plant was able to draw all of the energy it needed, roughly 1,200 to 1,400 kilowatts at any given moment, from the solar array and from its two co-generation (co-gen) system engines. The co-gen engines capture and burn the gas that is coming off the anaerobic digester process tanks, using that gas to generate additional power instead of releasing it into the atmosphere. The solar system, when at its peak on Thursday, was generating close to 800 kilowatts.

Douville said the success was attributable to a combination of factors, including relatively low wastewater flows, less demand than usual, a clear solar day and cooler temperatures. Data captured at the plant shows the milestone was reached at 11:30 a.m. The plant did not start drawing power from the traditional source again until 2 p.m. Attached is a screen grab that shows the solar photovoltaic production for the day.

“This is a great example of what we can get to,” said David Driskell, executive director of Community Planning and Sustainability. “It shows it is possible to really change our energy mix, and that will have long-term economic and environmental benefits to us as a community.”

While going “off the grid” is impressive, the ultimate goal for the WWTF is for 50 percent or more of the facility’s power to come from alternative sources, over a monthly or annual basis, Douville said. The city hopes to meet this goal through a combination of energy efficiency efforts and maximizing its alternative supplies.
SOURCE: CITY OF BOULDER NEWS RELEASE