By Georgena Terry, Volunteer Research Associate, CESAHow does a utility cope with peak loads that are stressing its distribution system? It constructs a new substation feeder. Or does it?

In 2014, as state legislators were considering a four-fold expansion of the state’s distributed generation program, the Rhode Island Office of Energy Resources (OER) and National Grid (the state’s major investor-owned utility) were busily investigating how distributed renewable energy could benefit system reliability. They identified the Rhode Island communities of Tiverton and Little Compton as places to test the proposition that distributed, solar PV generation could defer or potentially eliminate grid upgrades and enhance reliability.

A study determined that solar could provide 250 kilowatts of summer peak load needs and potentially contribute to the deferral of $2.9 million in electric distribution upgrades. The next step was for OER and National Grid to take a real-life look at PV deployment and how to maximize its benefits to the grid and to system owners in the two towns.

The hourly electricity load in Rhode Island’s test areas is highest in the late afternoon. Because panels facing southwest and west generate electricity during this time period of peak demand, they offer advantages for the distribution system. Even though the total amount of electricity generated by a typical south-facing array is greater on an annual basis, its solar generation drops off significantly in the late afternoon when the electrical load is high. In recent years, some electricity system analysts have called for using west-facing and southwest-facing solar panels to address this capacity problem.

Because less electricity is produced, the concept of orienting panels to the west would normally not be an easy sell to potential solar customers who want to maximize the amount of electricity they can produce to reap all of the financial benefits of their system. To address this concern, OER, Commerce Rhode Island, and the nonprofit SmartPower partnered to pilot a Solarize program that offered an extra incentive to homeowners who install westerly-oriented panels in the two test communities. The one-time rebate incentive is designed to offset the lower electricity production of the panels.
Data acquisition systems (DAS) are another integral part of this solar program. A DAS collects measurements at both the inverter and the electric service meter. It reports PV production data and tracks in-home energy usage. DAS will allow OER to monitor and ultimately evaluate the actual generation that the solar systems contribute during periods of peak demand.

On the policy side, the 2014 legislation removed a three-percent aggregate statewide limit on net metering which would have impeded the adoption of solar. The bill also addressed an accounting issue that has historically deterred some utilities from more fully embracing renewable energy: Contracts between utilities and solar developers have now been replaced by tariffs, which provide an income stream to developers without creating a balance sheet liability  or the utility.

Rhode Island’s nascent but ambitious project of cooperating with utilities to target areas that could benefit from distributed solar generation could easily be replicated in other locations. “This pilot will help us better understand the benefits of solar beyond cost-savings to the project owner—including potential system-wide savings for all ratepayers by deferring, or possibly eliminating, the need for investment in costly utility infrastructure to meet growing energy demand,” Shauna Beland, chief of program development at OER, commented. “If the pilot bears fruit, it could open the door for grid planners to tap solar as an exciting new tool in the toolbox of solutions to address electric distribution system investment needs.”


This blog post was originally published in CESA’s 2015 report “Clean Energy Champions: The Importance of State Policies and Programs.” This report provides the first-ever comprehensive look at the ways states are advancing clean energy and suggests how to further encourage clean energy growth.

This blog post was also published in Renewable Energy World.