Design for Purpose Microgrids – Water and Wastewater

Nov. 3, 2023
Michael Boswell, vice president, power & infrastructure at Concord Engineering discusses microgrid designs for water and wastewater.
So what happens when the grid goes down and the operations of water and wastewater treatment facilities are compromised? Nothing good for sure.

As proven by recent severe weather events and foreshadowed by future climate trends, the vital services provided to our communities by water and wastewater authorities can be compromised by loss of grid utility services. Even backup power systems relying on diesel fuel can be at risk as the supply logistics of fuel delivery can be impacted, leading to the diesel generators running out of fuel.

Often located in low lying areas or adjacent to bodies of water, wastewater treatment facilities and their upstream pumping stations are especially susceptible to flooding and storm tidal surge. 

Designing a microgrid for long-term multilayered resiliency

For decades these types of facilities have operated with emergency backup power by diesel engines. This is an adequate approach so long as the diesel can be stored for long-term operation or delivered when supply chains and local roads are compromised before, during and after a major storm or flooding event. Think fuel resiliency: Add natural gas engines to the diesel mix. Natural gas distribution systems have proven their resiliency during severe storm events.

Renewables and batteries

Renewable energy and batteries can play an important role in a flexible microgrid. Each has its purpose and each by itself has drawbacks that limit its ability to sustain long-term operations under a black sky scenario. But both complement each other to provide flexible attributes that enhance overall resiliency and operation by providing power that would have to be provided by engines needing possibly scarce or expensive fuel and, in the case of batteries, allow for fast formation of a microgrid with very stable voltage and frequency control.

Demand management and arbitrage

Under the right utility tariff or within the demand response and capacity markets offered by regional independent system operators or utilities, a flexible and actively managed microgrid that dispatches the distributed energy resource can provide significant economic benefits that traditional backup power cannot. Yes, the additional equipment and systems add capital cost, but if the right markets are available, why not design to capture the benefits instead of having “dead iron” on the books?

Additional hardening and operability against severe weather events

In addition to emergency backup power in the form of a microgrid, additional hardening, such as flood walls and elevating critical systems above flood lines, are often designed into critical facilities. Middlesex County Utility Authority’s Sayreville Pumping Station was designed with a floodwall system that can be operated ahead of or during a storm. The pumping station also has the ability to preemptively disconnect from the local grid and fire up its engines to operate in island mode. This benefits the authority but also aids the local utility by removing a large end of the line load from its distribution system during a time of stress.

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