Microgrids are increasingly recognized as dependable sources of power for emergency and other off-grid situations and as economical alternatives for reliable energy because of their ability to produce sustainable energy with long-term cost savings. Since energy is one of the biggest operating costs for wastewater treatment plants, microgrids are now being considered by plant managers eager to take advantage of those benefits.
Microgrids—integrated electrical energy systems comprised of interconnected loads and distributed energy resources that can produce and distribute electricity in independent operation from the power grid—can also provide enhanced reliability, rate stability, and sustainability.
RESILIENCE
Treatment of wastewater is particularly difficult if power outages are prolonged. “Storms are negative drivers for reliability conversations,” says Clark Wiedetz, director of microgrids, Siemens Digital Grid. “A microgrid provides the ability to control assets and to ‘island’ when it makes sense—for disasters, substation issues, or costs.”
After superstorm Sandy, nearly the entire state of New Jersey—2.8 million households—lost power. The electric grid was down, rendering most wastewater treatment plants inoperable. Then-Governor Chris Christie had to grant permission to dump millions of gallons of raw sewage each day into New Jersey waterways.
That was the start of a move toward adding microgrids at almost all of the state’s wastewater treatment facilities to provide resiliency by allowing the utilities to extend operations beyond previous capabilities after loss of grid power by using solar power and other distributed energy resources to prolong the existing fuel supply.
This utility resiliency program took five years to achieve. It began when Public Service Electric and Gas began operating a microgrid in Caldwell, NJ, using solar power plus storage to serve as backup generation capable of powering the facility for up to 10 days. The 250-kilowatt (kW) per 1-MWh battery system is paired with 2,682 solar panels that generate 896 kW. Siemens control technology monitors, manages, and distributes power across the system.
The project was funded by the Solar 4 All program, fed by customer rates. The New Jersey Board of Public Utilities approved utility spending for the program of $515 million in 2009, $247 million in 2013, and $275 million in 2016.
Similarly, the City of Ithaca built an emergency service microgrid. “We did a feasibility study and applied for a design award as part of the New York REV program,” says Jack Griffin, microgrid champion for Veolia North America, a leader in environmental services for water, wastewater, and energy. Veolia owns and operates district energy systems and provides advice to improve operational efficiencies and increase sustainability so utilities can operate in adverse conditions like big storms—and, during extended events, enable them to dispose of waste and deliver potable water.
The REV program—Reforming the Energy Vision—is Governor Andrew Cuomo’s comprehensive energy strategy for New York. It aims to build a clean, more resilient, and affordable energy system by developing new energy products and services to spur innovation, attract investments, and improve customer choices.
Ithaca already used digestion to get more methane out of the process and generate more power, but the city added solar panels and worked with the State of New York to “install breakers so they could disconnect from the grid and isolate,” explains Griffin.
Unfortunately, there were regulatory barriers that prohibited that part of the design, but he says the city is proceeding with enhancing digestion and solar development. “Regional barriers can complicate plans,” says Griffin, explaining that the issue is that there is “no one body” overseeing microgrids; each state has authority. However, independent systems often cross state lines, encountering different markets with diverse sets of variables, requirements, and restrictions…and confounding plans.
Beyond saving money, use of microgrids can ensure reliability. What is your reliability strategy? Wiedetz asks. If a wastewater treatment plant has multiple distributed generation assets, it can augment what is already there to save money and provide reliability.
Using renewable energy resources instead of traditional fossil fuels enhances sustainability. It’s one of the drivers, along with cost reduction and diversification of the fuel stream, that Wiedetz says is pushing this trend.
The common microgrid design on the west coast relies on solar, Wiedetz says. He says more solar plants are cropping up next to wastewater treatment plants. “There are opportunities, especially in California—so, many cities add solar next to a wastewater treatment plant. Where does the increase of distributed generation provide value? The West Coast.”
California isn’t the only state where solar works. Wiedetz counts 20 states with “a lot of solar” and says the price is less than or equal to the grid. “That’s the incentive: grid parity.”
Griffin says economies of scale make it affordable to have power delivered by the utility, but renewable resources such as wind and solar are changing the economics. In fact, affordability is another driver of adoption. “Capital expenses are getting less and there’s a higher penetration of renewables, including geo-thermal, because they are cheaper. When buying wind or solar power instead of natural gas, there is zero fuel cost. The most rapid price drop is in wind. Solar prices have dropped too, but not as much as wind.”
He mentions an island off the coast of Rhode Island that requires 40 MW. To create it costs $220 per MWh, or 22 cents per kilowatt-hour (kWh). But when a local utility partnered with a wind developer, they were able to drive costs down to $65 per MWh, guaranteed.
The price of wind may have dropped, but Wiedetz says that across the marketplaces and utilities, there has been an “enormous increase”—34%—in solar from 2008 to 2013.
Wastewater treatment plants already use digesters and backup generators to improve the effluent and gain use of digestion to heat the boilers for additional heat. “Influent of water must be treated. In the process of solving that problem, you create energy; it’s an economic value.” The reduction of solids reduces waste and generates methane for electricity, heat, and to power vehicles. It also reduces what goes to the landfill and GHG emissions.
But a controller isn’t all that’s missing to achieve microgrid status. A microgrid must run around the clock, every day of the year. To do that, it needs battery storage, which, Griffin says, is still at a “high cost point.”
Many wastewater treatment plants already have generators—sometimes due to regulations. Some may even have solar or other renewable distributed energy resources. But battery storage is new. “If you just have a backup generator, you may have to make an additional investment,” observes Wiedetz.
It’s a valuable investment. Adding battery storage increases reliability and can enable a plant to save on tariffs for high use periods. The recipe for microgrids is to “just add storage and controls,” says Wiedetz. “It’s more affordable.”
He believes that utilities are moving in this direction—and says other industries already have. For example, Wiedetz mentions a casino in California that combined solar, battery storage, and a controller added to the backup generator. “They saved $300,000 and had a 10-year payback.”
Achieving a swift ROI is easier in states that offer incentives and grants for microgrid development, energy efficiency, or other resiliency or renewables initiatives. Enrolling in a demand response program with the electric utility may be a way to generate revenue.
MINIMIZING ENERGY COSTS
Of course, one way of accelerating ROI is by reducing costs. The integration of renewable energy can significantly impact future energy costs. By adding load flexibility to react to changes in electric rates, plants can “island” to avoid peak charges, as well as for emergency situations.
Microgrid technology is currently used by fewer than 3% of California’s digester-operating wastewater treatment facilities due to high costs, a long payback period, and limited technology experience. But Rialto Bioenergy is working to offer a clear, repeatable, standardized microgrid configuration that reduces costs for both wastewater treatment plants and organics management facilities.
The $5 million project funded by the California Energy Commission intends to demonstrate the commercial value of microgrids for wastewater treatment plants that use anaerobic digesters. The microgrid, located in Rialto, CA, will include a 2-MWh battery storage system and a new 2-MW combined heat and power unit. Biogas produced from food waste and sewage sludge will fuel the CHP operation.
Rialto Bioenergy expects to begin converting waste by 2019. When it does, the treatment plan will produce 13.38 MW of energy from up to 1,080 tons per day of food waste, liquid waste, and municipal biosolids. It will produce 3 MW of renewable electricity and 8.2 MW of equivalent biogas that can be used in offsite power generation or for vehicle fuel.
The microgrid will be able to “island” during power outages and supply power to the plant for at least three days. During normal operation, it will enable more efficient energy management by minimizing electrical draw, exporting renewable energy, and participating in demand response. As a result, the microgrid will minimize energy costs at the facility, and help reduce the need for the local utility to start up high-cost peaking plants when the grid is under strain.
Another way of looking at it is to ask: What’s the cost of being down? “There are costs associated with power outages,” states Wiedetz.
Because the benefits have been proven, there is a “heightened intensity level” of interest in microgrids at wastewater treatment plants, Griffin believes, but he says that the acquisition cycle in the US and Europe is lengthy and he considers this country in the “discovery phase” at present. “Industrial has a quicker cycle because they’re more aware of disruptions in the profit-loss cycle.”
The continuity of service metric is what Griffin considers as the value investment, but he adds that there are two levels: emergency response and manage energy profile, which he says is the most economical value from a lifecycle perspective. The least upfront cost solution is not the best; lifecycle costs must be considered.
Microgrids are great for a wastewater application, he continues. Although self-generation is established, microgrids are new for this industry. Adoption will be pushed by society, Griffin believes, particularly as society weighs the impact of global warming. “The [federal] government pulled out of the Paris Agreement, but 30% of the mayors stepped in support it,” he says. “The motivation is there.” And so are the benefits.
