Efficiencies at the Water-Energy Nexus

Nov. 7, 2018

“The interdependence of water and energy forms a nexus or convergence that means efficiency measures in one area have the potential to produce additional efficiencies in the other, thus benefiting both water and electric utility customers as well as the environment.”
American Water – Water-Energy Convergence: Efficiency Challenges and Opportunities

Energy efficiency and how to pursue it at water utilities has been studied by various agencies and nonprofits for the past 15 years, particularly in the western states. A few have published papers on the water-energy nexus, which focus on how utilities can reduce energy use. Most recently, they are linking the need to reduce greenhouse gases to energy efficiency. Two papers, in particular, stand out.

The US Department of Energy and the University of California, Irvine, held a two-day Water-Energy Workshop in 2015 and brought together experts from academia, utilities, and state agency representatives from California and the southwestern states to discuss issues regarding the interactions between water and energy sustainability. A report titled Capturing the Benefits of Integrated Resource Management for Water & Electricity Utilities and their Partners was published in May 2016 by the DOE and the University of California. It can be found on the DOE website.

California utilities took the report seriously. For example, the California Public Utilities Commission’s requirement that utilities examine embedded energy savings associated with water prompted the San Diego County Water Authority Board to coordinate efforts to implement water efficiency programs with San Diego Gas & Electric. They developed three programs: comprehensive water/energy audits, a landscape irrigation management program, and a recycled water program.

Pacific Gas and Electric and a number of Bay Area water utilities collaborated on developing a high-efficiency clothes washer rebate program which brought together a number of uncoordinated efforts already active from individual utilities.

The Pacific Institute, in its 2013 publication Water-Energy Synergies: Coordinating Efficiency Programs in California, wrote that all forms of energy from hydropower to solar panels use water to extract and process the fuels, construct the processing facilities, or generate the electricity. And water supply, treatment, use, and disposal use considerable amounts of energy.

The California Energy Commission found in a 2005 study that water efficiency improvements could save as much energy as some of the state’s existing energy-efficiency programs at about half the cost.

The profiles below illustrate emerging energy trends among water utilities. Generating renewable energy is growing in popularity. Improving pump performance is also high on their list. And a few are pursuing or volunteering to participate in research projects.

The Water Operations Division of the Los Angeles Department of Water and Power (LADWP) has been executing numerous projects for several years throughout its many facilities to reduce energy use and make its equipment more efficient, according to Steven Cole, assistant director of the division.

Starting with the basics, Cole says his crew has swapped out incandescent and fluorescent lights for LEDs at 80 pump stations, 120 water storage tanks, and a filtration plant. They will move on to switch out lights at 400 underground vaults containing pressure regulation valves, he says.

The division is installing premium-efficiency motors on their pumps, says Cole. Variable frequency drives are installed on the bigger pumps. A 2,000-horsepower (hp) pump requires a tremendous amount of power to start up, so staff uses soft starts and installed variable-frequency drives (VFD) on them. However, since VFDs require air conditioning to keep them cool, smaller pumps do not have them—they get the premium efficiency motors, he says. He explains that air conditioning small pumps to install VFDs would negate any energy savings. Cole says they are also eliminating any unnecessary use of uninterruptible power supply equipment because they require air conditioning.

The insides of new and refurbished pumps are recoated with Belzona, a metal super glide coating to improve water flow efficiency by repelling water away from the pump’s metal surface. Cole says this improves a pump’s efficiency by 6%.

Monitoring pumps in real time makes them more efficient, says Cole. They are monitored according to their temperatures, vibration, flow rates, and pressure. “We’ll turn on the most efficient pump first, and the least efficient last,” he says. Real-time monitoring also improves maintenance, by identifying pump/motor problems early.

The water operations division participates in LADWP’s demand response program between June 15 and October 15 each year. When the division gets a call, between 1:00 and 5:00 p.m. on weekdays, they work to adjust pump performance to reduce power and operating hours. They also adjust air conditioning and lighting during those hours when called upon.

In 2016, the division reduced power by 7.9 MW during peak periods, and in 2017, they reduced power by 7.6 MW. Cole said the average commercial customer will reduce demand between 500 kilowatts (kW) and 1 MW, on average, when called upon. “LADWP gave us our own peak reduction award,” he says.

Cole says they have begun a pilot for the water distribution system in the last six months by putting pressure and flow sensors in the lines. “Some lines may not need to have high pressure, and by monitoring, they may be able to dial back pressures,” he says. Lower pressure will avoid leaking in a pipe, he says.

This pilot is in preparation for a state regulation requiring all water utilities to reduce water loss starting in 2019, Cole says.

Cole says they haven’t calculated dollar savings but do work closely with the power teams. “We want to save our rate payers money. We need to reduce power consumption in terms of that,” he concluded.

New Jersey American Water installed solar modules on a reservoir at Canoe Brook Water Treatment Plant in Milburn, NJ, in 2011. It is designed to withstand a freeze/thaw environment.

The San Diego County Water Authority has been aggressive in developing local renewable energy systems and continues to do so with its growing list of energy initiatives. Its intent is not to become energy self-sufficient, but to produce the revenues that will keep rates low. Andrea Altmann, a senior management analyst in the Water Authority’s Energy Program, says, “We use renewables during the day and what we don’t use we send back to San Diego Gas & Electric to reduce our utility bill costs.”

SDCWA delivers wholesale water supplies to 24 retail water providers, including cities, special districts, and a military base. It uses 86,000 MWh annually in its operations. Its solar systems, pumped hydro, and inline hydro projects produce 66,000 MWh annually.

The Water Authority has also been very successful in reducing water usage in response to the decades of off- and on-again droughts. It has seen a 47% decline in per capita water use since 1990, from 235 gallons per capita per day (GPCD) in 1990 to 124 GPCD in 2017. The state-mandated 2020 target is 167 GPCD. This reduction offsets the need for over 300,000 acre-feet per year within the region.

SDCWA signed a 20-year agreement with San Diego-based Borrego Solar Systems, which built three solar arrays. They have been operating since 2011 on the roofs and car ports of its headquarters in Kearney Mesa, its Escondido Operations Center, and the Twin Oaks Valley Water Treatment Plant. Together, the three systems generate about 2.7 million kilowatt-hours (kWh) annually, representing 45% of energy used in the facilities. Combined, they will cut the agency’s energy expenses by nearly $5.6 million over 20 years.

Borrego owns and operates the systems and sells the power to the Water Authority at a reduced and fixed rate with an annual price escalation factor.

SDCWA is exploring the potential of building a floating solar system on its Hodges Reservoir in the northern portion of San Diego County. It is discussing a public/private partnership with Cratus Energy which is working on the design of a solar/utility connection and environmental review. Altmann says the Water Authority would expend no capital. The current issue is working through a business model.

Jeff Shoaf, also in the Energy Program, says the issue confronting both the Water Authority and Cratus is that they do not know of an installed floating system on which to model a design. They need to coordinate with regulatory agencies and deal with environmental issues such as impacts on water quality. He said there is a very large learning curve involved here beginning with how to anchor the solar framework to the floor of the reservoir or on the shoreline and dealing with fluctuating water levels. “The developer has been struggling,” he says.

The current plan is to have the floating solar system cover about 20 acres of the 2,300-acre Hodges reservoir. The idea began with a request for proposals in 2014, which produced no responses. Another RFP was released in 2016 and Cratus was the lone contractor to respond. The SDCWA Board approved general terms and conditions in 2017. Staff will ask the Board to approve a power purchase agreement once the project receives California Environmental Quality Authority (CEQA) approval, says Altmann.

In March 2018, SDCWA announced that ENGIE Storage had completed installation of commercial-scale energy storage batteries at the water authority’s Twin Oaks Valley Water Treatment Plant near San Marcos. The system was commissioned five months later, in August, following testing. The Water Authority says the 1-MW/2-MWh system will save approximately $100,000 annually.

The energy storage system is designed to reduce operational costs at the facility by storing low-cost energy for use during high-demand periods when energy prices are at their highest. ENGIE Storage will use its GridSynergy software to charge and discharge stored energy, either from the grid or the onsite solar energy system which generates 1.75 million kWh annually.

Santa Clara, CA-based ENGIE Storage, a division of ENGIE North America, signed a power efficiency agreement with the Water Authority to install the $2 million system at no cost to SDCWA. It owns, operates, and maintains the system under the 10-year contract. The California Energy Commission provided $1 million to help fund the project, under the California Public Utilities Commission’s Self Generation Incentive Program.

SDCWA has several pumped storage facilities in operation or in the planning stages. The 40-MW Lake Hodges Pumped Storage Facilities began operating in 2012 following seven years under construction. It has eight hours of storage capability, says Altmann. It provides emergency water storage for up to 40,000 homes. She says the water authority works cooperatively with the City of San Diego which owns the Hodges Reservoir while SDCWA owns the pumped storage facility.

Water is stored in Olivenhain Reservoir 770 feet in elevation from the Hodges Reservoir through a 1.25-mile-long pipeline connecting the two reservoirs at the Lake Hodges Pump Station. The pump station extends 10 stories underground and houses two 28,000-hp pump turbines capable of generating 20 MW each. An inlet-outlet structure is located below the surface of Hodges Reservoir and links the pump station through a 200-foot-long tunnel, allowing water to be moved back and forth.

When electricity rates are low, water is pumped uphill to the Olivenhain Reservoir and during high energy demand periods, that water is released downhill, passing through the pump station, activating the pump turbines, and generating 40 MW of power, helping to manage temporary peak demands or unplanned outages.

SDCWA is also planning a 500-MW pumped hydro system with eight hours of storage at the city-owned San Vicente reservoir and is currently undergoing negotiations with Brookfield Renewable. Altmann says construction has not been scheduled.

Lastly, while not considered pumped hydro, SDCWA buys 1.7 MW from Hoover Dam under a federal preference power contract.

The Los Angeles Department of Water and Power is refurbishing pumps, as seen in these before and after photos, and coating them with Belzona, a metal super glide coating to improve flow efficiency.

SDCWA is expanding its inline hydropower production as well. Like a water wheel, explains Altmann, energy is captured by small pump turbines as the water flows through large-diameter pipes. It already owns and operates the Rancho Peñasquitos inline hydro generation facility which has been operating since 2006. Power is generated year-round using a single 4.5-MW horizontal turbine, providing 25,000 to 30,000 MWh annually.

The power is sold on the California ISO wholesale energy market and generates approximately $500,000 in annual revenue for SDCWA.

The Water Authority is planning to rehabilitate the Alvarado Hydroelectric Facility, which was built in 1984 and damaged by flooding in 2007. The two original 1-MW pump turbines will be replaced by a 1.7-MW turbine since flows have changed quite a bit, says Altmann. She says the staff was planning to go to its board for approval of a design and construction plan this summer and release an RFP later in the year. Construction is estimated to cost between $7 million and $8 million. Once operational, the facility is expected to bring in $600,000 in annual revenues.

American Water Indiana’s new $1.4 million solar project at its Newburgh Operations and Treatment Center will cut annual costs for electricity by $65,000.

American Water maintains a portfolio of solar, wind, and biomass facilities. The company has installed over 3.1 MW of solar generating capacity at 11 facilities across three states (New Jersey, Illinois, and Missouri) with plans to install more solar at additional facilities. Furthermore, its affiliates have initiated projects to generate alternative energy or reduce energy for clients or in their own operations.

Indiana American Water broke ground on a new $1.4 million solar project at its Newburgh Operations and Treatment Center. It will cut the company’s cost for electricity by approximately $65,000 annually and abate nearly 500 tons of CO2 emissions a year.

In 2005, New Jersey American Water installed the state’s largest ground-mounted solar electric system at its Canal Road Water Treatment Plant in Somerset, NJ. It produces up to 730,000 kWh annually and supplements 20% of the peak power usage needed to run the plant. The savings in carbon dioxide is equivalent to planting 94 acres of tree seedlings or preserving 2.6 acres of land from deforestation, according to the American Water white paper Water-Energy Convergence: Efficiency Challenges and Opportunities, which can be found at www.pr.amwater.com/static-files/de911876-3e07-406e-b34a-976433140545.

Furthermore, in 2011, New Jersey American Water installed solar modules on a reservoir at the Canoe Brook Water Treatment Plant in Millburn, NJ. It was the first solar array on the East Coast on a body of water designed to withstand a freeze/thaw environment. The 538 solar modules rest on a docking station designed to float on the water’s surface as it rises and falls. The array produces 135,000 kWh annually—about 2% of the plant’s power for an estimated cost savings of $16,000. The $1.35-million project was designed and built by ENERActive Solutions of Asbury Park, NJ.

At Pennsylvania American Water’s Shire Oaks Pumping Station, a successful pilot program using the Enbala Power Networks smart grid technology offset 2% to 3% of the site’s total energy cost. Essentially, this technology manages the electricity use of the treatment plant and pumps. Instantaneous water pumping is aligned with the instantaneous electrical demand of the grid thereby allowing the water utility to benefit from short-term peak shaving.

American Water has been awarded three patents for a technology called NPXpress which reduces aeration energy consumption during wastewater treatment by up to 50% and supplemental carbon source by 100%. It has been implemented at seven full-scale wastewater treatment plants in New Jersey and New York and is currently being implemented at a system in California as part of the company’s overall initiative to achieve sustainable energy-neutral wastewater treatment. 

About the Author

Lyn Corum

Lyn Corum is a technical writer specializing in water and energy topics.