From Hawaii to Vermont, utilities are exploring “virtual power plants,” networks of solar panels, batteries and other devices that can be controlled to help manage the grid.
Holy Cross Energy, a cooperative utility based in Glenwood Springs, Colorado, has developed a virtual power plant made up of four homes that have rooftop solar panels, energy storage, electric vehicle chargers, and heat pumps for space heating and hot water, according to Steve Beuning, vice president for power supply and programs.
HCE can control the homes’ systems to operate in three modes: to keep their load as flat as possible, as a microgrid and to provide demand response to optimize the grid, Beuning said.
The control system was activated in July and the equipment is still being tested, according to Beuning.
He said HCE expects to be able to store solar generation during the day and discharge when electric demand is peaking.
The project gives HCE insights into possible avenues for developing retail programs, Beuning said, noting that on-site energy storage is almost economic for the utility.
HCE offers the most generous utility rebates for rooftop solar in the United States and about 1,300 of the utility’s roughly 53,000 members have installed rooftop systems averaging 8 kilowatts, according to Beuning.
The utility, for example, offers $750 per kW for a system’s first 6 kW, then $500 per kW for the next 6 kW and $250 per kW for the next 3 kW. Incentives for a 15-kW system would total $8,100. HCE also offers net metering for customers with solar panels.
Looking ahead, HCE could use its virtual power plant software to harmonize a growing fleet of rooftop solar with its operations, Beuning said. The utility is ahead of schedule in meeting its goals of getting 70 percent of its electricity from renewable resources by 2030.
The project is part of a net-zero housing development called Basalt Vista built by Habitat for Humanity.
The project was developed in partnership with the Energy Department’s National Renewable Energy Laboratory. The project’s goal, according to NREL, is to “develop and validate new grid visualization, control paradigms, and business models for cooperatives and municipally owned utilities through integration of grid-friendly intelligent [distributed energy resources] assets.”
Other project partners included the National Rural Electric Cooperative Association and Survalent, a provider of advanced distribution management systems for utilities.
Utah utility to manage virtual power plant
Meanwhile, Rocky Mountain Power, a Berkshire Hathaway Energy utility, is working with battery company Sonnen and the Wasatch Group, a real estate company, on an apartment complex in Herriman, Utah, that will include 600 batteries capable of storing 12.6 megawatt-hours produced by solar panels totaling 5.2 megawatts.
RMP will manage the energy storage as a virtual power plant to provide emergency back-up power, daily management of peak energy use and demand response, the companies said Aug. 27.
When the Soleil Lofts project is completed late next year, it will be the largest residential battery demand response facility in the United States. The first wave of residents will start moving in September.
RMP expects the battery demand response project will cost $34.3 million, not counting the solar panels. The batteries are expected to cost $12 million.
RMP is contributing $3.3 million to the battery project, which the Utah Public Service Commission approved in late June.
The project will allow RMP to study the value of having behind-the-meter grid-optimized solar and battery storage interconnected to its distribution system, the PSC said in its decision. It will also help the utility evaluate rate design options for customers with batteries and allow RMP to prepare for expected larger-scale deployment of battery storage technology integrated onto the distribution system, according to the commission.
RMP is part of PacifiCorp, which has 1.9 million customers in six Western states.
Hawaiian, Vermont utilities advance virtual power plant efforts
Utilities in Hawaii and Vermont are also moving ahead with virtual power plant programs.
In Hawaii, Sunrun will install 1,000 solar-and-battery systems on the island of Oahu by 2024 as part of a virtual power plant system to be managed by Open Access Technology International, a Minnesota-based company.
In late August, the Hawaii Public Utilities Commission approved a “grid services purchase agreement” between the Hawaiian Electric Co. and OATI. Under the agreement, OATI Energy Alliance will aggregate, forecast and control customer-owned behind-the-meter distributed energy resources to supply grid services to the utility on several islands, according to the company.
OATI will create a cloud-based system to provide ancillary services, including frequency control, spinning reserves and operating reserves using aggregated distributed resources, the company said.
Also, Sunrun started selling its Brightbox home solar and battery service in Vermont last month. Customers in Green Mountain Power service area can use the equipment to join the utility’s “bring-your-own-device” program, which allows the company to tap into a fleet of battery systems to meet peak demand. Vehicle chargers and water heaters are also eligible for the program. Green Mountain Power has about 265,000 customers.
Public power also looking at virtual power plants
Georgetown, Texas, a city of 70,000, is looking to manage its future peak demand needs "by taking utility-scale assets and deploying them within the community," said Jack Daly, assistant to city manager David Morgan, in late 2018.
The city wants to lease rooftop space for solar panels and ground space for batteries from residential and commercial properties, offsetting the need to buy additional power from outside sources to meet growing peak demand - i.e., a virtual power plant.
Georgetown in 2018 was a winner of Bloomberg Philanthropies U.S. Mayors Challenge. Nine cities will receive $1 million as part of the challenge.
In late 2017, several energy storage projects in Massachusetts that involve public power utilities were awarded grants as part of a state energy storage program.
Included among the utilities was Braintree Electric Light Department. To be located at three Braintree Electric Light Department substations, the project involves a set of three storage systems placed into a virtual power plant model to reduce generation and transmission capacity charges and demonstrate several non-monetizable benefits, including integration of renewable generation.