In June, President Obama made a speech about the increase in renewable power that the United States had created in the last 4 years, and announced goals to double this amount in the next four. Virtually all of this power was solar and wind power. Little mention was made of hydroelectric or onsite sources. But the latter have been around much longer than the former sources and there may be options to increase their contributions under the right circumstances.
Hydroelectric power has been in use in the US for over 100 years. By the 1930s, 40 percent of the nation’s power came from hydroelectric dams, including some fantastic accomplishments of the time like the Hoover Dam. Today we have over 100,000 dams in the US, most of which provide power. Today hydroelectric is only 6 percent of our total. The reluctance to continue with hydroelectric power involved fisheries, land acquisition costs and legal issues. Some hydropower options are excellent. Hurting fisheries (which disrupt local economies dependent on those fisheries) may not be, and therein lies part of the dilemma.
But water and wastewater utilities are actively looking for means to reduce power costs. Depending on the utility, pumping water can account for 80-90 percent of total power consumption, especially with high service pumps on water systems that require high pressures. More efficient pumps is one obvious answer, but of fairly limited use unless your pumps are really old. Variable speed drives can increase efficiency, and the cost is dropping. But note that with all that high pressure, how do utilities recapture the energy? We often don’t and the question is whether there is a means to do so that can benefit up. The first step is looking at plant hydraulics. Is there a way to recapture energy in the form a pressure. For example of reverse osmosis systems, we can install a turbine to recapture the pressure on the concentrate side. They are not very efficient at present, but the potential is there. On long gravity pipe runs for water supply, a means to recapture pressure might also be available.
Of course on-site generation of power is a potential solution. Water and sewer utilities have land, and on the wastewater side, methane, so producing power is possible. This solution, however, may not be embraced by power utilities due to the potential revenue reduction potential and loss of embedded reserve capacity at water and wastewater plants. As the water facility takes on on-site generation, their load profile may shift significantly placing them in under a different rate structure. This may greatly reduce the benefit to the facility. There are, however, approaches to permit win-win solutions. The goal is to put willing power and water utilities together to permit local generation that will benefit both power and water utility systems to encourage public – private partnerships. A medium to large wastewater plant can generate at least a third of its power needs. Some even more if they take in grease, oils and other substances that should not be put into the sewer system. The potential there is significant. EBMUD has a plant that is a net seller of power. We should look for opportunities. But don’t forget, water utilities can create hydropower without impacting fish populations. We just need to seek out the right opportunities.