Addressing the Water-Energy Nexus
While clean water flows freely from our sinks, the fact is that close to 1 billion people in developing countries don't have access to this critical resource. Closer to home, scientists at the Scripps Institution of Oceanography in University of California, San Diego have projected a 50 percent chance of Arizona’s Lake Mead drying up by the year 2021, at the current rate of global warming and water consumption.
As these alarming statistics are released, there is a growing reality that while much has been done in the realm of calculating energy consumption in buildings, few tools are available to evaluate the resulting water consumption required to produce that energy.
The Water- Energy Nexus
The primary issue of the Water- Energy Nexus is the fact that the process of burning coal and natural gas in traditional thermoelectric power generation—which takes place in most power plants—consumes large quantities of water for use as a cooling source to condense steam. Power plants utilize water for cooling systems and water plants consume power for treatment and distribution, creating a vital interrelationship between energy and water.
In fact, the Union of Concerned Scientists has reported that 53 percent of all fresh surface water consumed in the U.S. is being used to cool fossil fuel and nuclear power plants. Clearly, water distribution is energy intensive with high energy costs. Furthermore, utility companies want to know how much energy is embedded in their water use and the energy savings in water efficiency programs. So while plumbing engineers are actively working to specify water-saving fixtures for toilets, faucets, and showers, and to design rainwater harvesting and grey-water systems to reduce water use, it is difficult to evaluate how much water is being consumed for energy production.
To begin addressing this issue, the New Buildings Institute (NBI) has developed a calculator to estimate the watershed impacts of building electricity use and compare it to on-site water consumption.
With this new tool, users enter basic inputs to create a baseline for a proposed building to estimate the water cost of energy consumption, which researchers have found to be in the range of 0.25 to 0.75 gallons per kWh, depending on the state. The NBI simulation has found that water savings at the generation source, created by energy efficiency enhancements, are on the same order of magnitude as building-level water savings of 20 percent.
Although only a step in this direction, the new NBI program is attempting to answer a critical question: If a building is conserving any amount of energy, what percentage of those savings relate to water? The NBI calculator is the first noteworthy attempt to guide the building community in this new direction to develop a better understanding of water savings, on the building side, from the point of origin to the point of use. In working to better evaluate if the amount of energy savings vs. the amount of water savings are on par, advocates hope this will create a buzz in raising awareness.
Moving in the Right Direction
One great example of a pro-active water efficient project is the California Endowment’s Water Reclamation project at The Center for Healthy Communities in downtown Los Angeles. Instead of discharging condensate drainage blowdown from the central plant water cooling tower into the sanitary drainage system, the water is pumped and stored into a dedicated 3,000-gallon capacity storage tank.
After treating the water with softeners, filtration, and reverse osmosis, this reclaimed water provides all of the building’s water irrigation needs, thereby fully eliminating the use of fresh potable city water for landscaping.
As one of the first facilities in the city to utilize this technology, the project is an aggressive step toward addressing the water-energy nexus.
Of course, it is a steep road ahead in terms of raising more water conservation awareness, and pursuing tools and initiatives to ensure that the industry is working to taper down the vast amounts of water currently used for energy production. But these first steps point us in the right direction.