Distributed Energy Resources

How solar can reduce congestion and save costs

When we think about solar as an electricity source, we generally think in terms of residential, commercial-and-industrial, or utility-scale installations. A newer trend is distributed utility-scale solar.

I define distributed utility-scale solar as any solar photovoltaic system, typically between 2 MW and 20 MW AC, directly connected to the electric distribution grid at medium voltage, between 12 kV and 35 kV. While such systems have been common in Europe for years, because of feed-in tariff policies, they're just starting to be accepted in the United States. The advantages for utilities are many.

Distributed utility-scale solar allows utilities to locate electricity generation close to where the loads are heaviest. If you put a PV system near your heaviest users — factories, high-population areas, or heavily loaded substations — you benefit from considerably reduced voltage drop, meaning less energy wasted in the transmission and distribution system. This can reduce transmission costs, boost voltage, and improve power quality, when properly matched to the load profile.

Properly located solar plants can alleviate congestion on heavily loaded nodes. It requires utilities to understand where the most congested nodes are.

Public power utilities should look at solar as a distributed resource that can be used to provide low-cost, long-term predictable energy by being placed near congested points in the distribution system. If deployed in this way a distributed utility scale solar system can even save millions of dollars in avoided or deferred capacity upgrades.

For example, if you have a circuit that is near capacity with peaking daytime loads, it is likely that a costly upgrade will need to be planned to support reliability and future load growth. And losses on a circuit near capacity are greater than a circuit with excess capacity.

If a PV system is deployed on the congested circuit, it can offset peak daytime load, reduce congestion, reduce the losses, and augment the capacity of the circuit by acting as a negative load. Depending on how prices are set by the transmission operator, utilities can even cause reduced nodal pricing by putting solar at that congested node.

Distributed utility-scale solar helps utilities improve customer service. By connecting distributed utility-scale PV systems directly to the electrical distribution system, utilities can choose to make electricity from solar available throughout their entire service area and help protect the environment while meeting customers' desire for renewable energy.

Distributed utility scale systems can be built and operated with economies of scale — this means utilities can offer solar power to their customers at a lower cost than if they were to install their own panels. It could be a win-win for all.

Solar is becoming less expensive and more sophisticated every day, so utilities should be on the forefront of this revolution. Start the conversation to determine what the right solar strategy is for you. Take advantage of the solar revolution to benefit your customers and community.