Energy and water are connected. Power plants use significant amounts of water for cooling. And pumping stations require significant amounts of energy to deliver water to communities where it is needed.
At Sempra Energy, we work to reduce the amount of water we need in our operations. This is particularly true in water-stressed areas where community access to adequate supplies of fresh water may be a concern. We design our facilities to use the least amount of water possible, utilize recycled water when possible and also work with local water districts on water-saving initiatives.
In 2015, Sempra Energy and our subsidiaries withdrew 27.9 billion gallons of water, and returned 25 billion gallons (90 percent) to the source. Our businesses withdrew 24.9 billion gallons of salt/brackish or seawater, primarily used to support LNG operations. Another 2.3 billion gallons were reclaimed or recycled water, primarily used to support power generation operations. Some 493 million gallons were fresh water, also primarily used to support power generation operations. We minimized our need for fresh water by using dry-cooling technology and reclaimed or recycled water.
Minimizing water use
At Sempra Energy, we place a priority on respecting local water supplies and mitigating the risk associated with operating power plants in areas where there is the potential for prolonged water scarcity. Our subsidiaries’ power generation facilities save water in a number of ways:
- SDG&E’s 565-megawatt Palomar Energy Center in Escondido, Calif., uses reclaimed water (treated wastewater) in the electric generation process. This saved more than 830 million gallons of fresh water in 2015.
- SDG&E’s 480-megawatt Desert Star power plant near Boulder City, Nev., uses dry-cooling, which requires only 10 percent of the water used by traditional wet-cooled power plants.
- Sempra International’s 625-megawatt Termoeléctrica de Mexicali power plant in Mexicali, Mexico, uses treated sewage, cleaned in our own water treatment facility, to cool the plant. As a result, we saved more than 1.5 billion gallons of fresh water in 2015.
We also minimize our need for water by developing and operating wind and solar power plants, which use a negligible amount of water compared to coal or natural gas-fired power plants.
Extreme drought and water use
Utility infrastructure projects can require millions of gallons of water – for soil compaction, dust control and fire suppression. However, regulatory hurdles and a long approval process can make it difficult to use recycled water. Both SDG&E and SoCalGas are working with local authorities to ease restrictions on recycled water use.
Our utility businesses can also take direct action. In 2015, during a period of extreme drought, SDG&E developed a water sourcing plan that identifies all potential water source options and outlines the water supply regulatory framework and restrictions in the region. This allows project planners to understand the potential water needs of a project early on, with sufficient time to secure a recycled water source.
The energy-water nexus
In California, 20 percent of the state’s electricity and 30 percent of its natural gas are used for water-related purposes such as pumping water to where it is needed. (These figures exclude the natural gas used by natural gas-fired power plants.) Water plays a similarly vital role in producing energy, as it is used to cool many power plants.
Energy producers and water agencies look for opportunities to work together. One example comes from the San Diego County Water Authority. At night, when electricity supplies are ample and electric rates are low, water can be pumped uphill from the Lake Hodges Reservoir to the Olivenhain Reservoir. Then, during the day when demand for power increases, the water can flow back downhill, generating up to 40 megawatts of electricity.
Piloting a new type of raincatcher
At SDG&E, Senior Environmental Specialist Marc Doalson had an interesting question. What if it were possible to capture the rainwater that flows off of transmission towers? How much water could be captured and how might it be used?
SDG&E is now exploring this idea with a pilot project. Preliminary estimates indicate that with the runoff from 2-3 inches of rain falling on just one transmission tower, the utility can fill a 500 gallon tank.
If the concept were expanded, SDG&E could use water captured locally for road and other maintenance, as opposed to needing to truck potable water in from other locations. Cost and water savings could be significant!