Innovative Utilities Reducing Water-Energy Nexus Pressures
By Robert C. Brears
With large parts of the country facing drought conditions, including California, Massachusetts, and Alabama, small communities and cities alike are facing increased water-energy nexus pressures. Water and energy are interlinked as energy is required in the extraction, treatment, distribution, and use of water, in addition to the collection and treatment of wastewater, while large volumes of water is required for hydroelectric and thermometric power generation. For example, in California water-related energy use consumes around 20 percent of the state’s electricity.
Increased Nexus Pressures In The Future
Heading into the future, higher average temperatures, more severe droughts, changes in precipitation patterns, severe weather events, and earlier snowmelt as a result of climate change will place additional stress on the availability of water for both potable use and energy production. Nonetheless, utilities are taking steps to reduce water-energy nexus pressures in the treating and distributing of drinking water, as well as collecting and treating wastewater, by developing renewable energy systems.
Water Utilities’ Cutting-Edge Renewable Energy Systems
San Diego County Water Authority — an early leader in pursuing hydroelectric and solar energy projects as part of its infrastructure — has been operating the Water Authority-owned Rancho Peñasquitos in-line hydro generation facility since 2006. The facility generates 25,000 to 30,000 megawatt-hours (MWh) of renewable energy annually, enough to power around 5,000 San Diego homes. Not only does it provide the utility with clean energy and eliminate the equivalent of 60,000 metric tons of carbon dioxide a year, the facility also generates surplus electricity for the local grid, providing the utility with more than $1 million in annual revenue. Meanwhile, the Metropolitan Water District of Southern California has recently activated two separate solar fields with over 10,000 large sun-tracking panels at the district’s F.E. Weymouth Water Treatment Plant in La Verne. The 3-MW installation, covering 15.5 acres, will generate about 6.5 million kilowatt-hours (kWh) of clean, renewable energy per year. This will offset nearly 50 percent of the plant’s energy demands.
Small Water Utilities Cutting Back Energy Costs
Even water utilities serving smaller communities are implementing renewable energy systems as a way of reducing operational costs as well as carbon emissions. Just last month, Amador Water Agency of Sutter Creek, CA, opened its new hydroelectric power generation facility at the Tanner Reservoir Water Treatment Plant. The new facility uses water flowing in the agency’s Amador Transmission Pipeline, which carries raw water from Lake Tabeaud to the plant, to power a small turbine. The turbine will generate up to 580,000 kWh of electricity per year, which is enough to power the water treatment plant as well as adjacent offices and the maintenance facility. Overall, the new facility will save the agency around $4 million in electricity costs over 30 years as well as reduce the equivalent greenhouse gas emissions of 33 households each year.
Waste Becomes A Resource
Utilities are also implementing renewable systems in their wastewater treatment plants that not only reduce operational costs, but also provide an additional source of revenue. For instance, LA Sanitation will in late 2016 open a new 25-MW biogas-fueled cogeneration plant that will provide 100 percent of the steam and electricity required to power its Hyperion Water Reclamation Plant. The cogeneration plant is projected to generate more than 173 million kWh of electricity a year and supply up to 70,000 pounds per hour of steam. The use of biogas as an energy source will avoid the release of about 100,000 metric tons of carbon dioxide a year, equal to the emissions from over 21,000 cars per annum. Furthermore, the City of Phoenix has just announced that it will operate, once built, the largest wastewater biogas-to-energy facility in the U.S. The 91st Ave biogas project, expected to be operational in late 2017, will process raw biogas generated in the anaerobic digesters into renewable natural gas. This gas will then be sold to the vehicle market through the natural gas pipeline grid and will reduce carbon emissions by nearly 45,000 tons per year, the equivalent of taking over 70,000 cars off the road.
With climate change placing additional water-nexus pressures on communities of all sizes, water utilities can implement renewable energy systems that not only reduce operational costs and carbon emissions, but also provide additional revenue streams.
About the Author
Robert C. Brears is the author of Urban Water Security (Wiley). Urban Water Security argues that, with climate change and rapid urbanization, cities need to transition from supply-side to demand-side management to achieve urban water security.