UTILITY INNOVATION

Combining wind, solar, and thermal storage for beneficial electrification

An update from Lake Region Electric Cooperative

 

500 kW of solar. 2.3 MW of wind. Residential water heaters. What do these things have in common?

They are all part of a strategy at Lake Region Electric Cooperative to pair local, renewable energy with beneficial electrification in a way that reduces costs to the cooperative and its members.

 

Lake Region members had an appetite for renewable energy—and local renewable energy—so we worked with Juhl Energy over a couple of years to develop the project.

Dan Husted, Vice President for Business Development at Lake Region Electric Cooperative

So, first, the local renewable energy.

Located in Trondhjem Township, the wind-solar hybrid project from Lake Region Electric Cooperative (LREC) includes a 500 kW solar array and a single 2.3 MW wind turbine. According to Dan Husted, LREC’s Vice President for Business Development, “Lake Region members had an appetite for renewable energy—and local renewable energy—so we worked with Juhl Energy over a couple of years to develop the project.”

 

The 2 MW hybrid system uses technology from General Electric and is interconnected directly into the adjoining distribution feeder. It takes advantage of the complementary nature of wind and solar energy: when the wind blows the most tends to be when the sun shines the least, and vice versa. That means that the solar output provides summer peak energy, and the wind provides winter peak energy. LREC purchases the output of the project, which is owned and operated by a subsidiary of Juhl Energy. Because of the ownership structure and power purchase agreement, the co-op incurred no debt in the construction of this project.

According to Husted, “Economic benefits include locking in low-priced energy over 20 years. There are also savings related to the avoidance of some capacity and transmission charges—that’s where much of the savings comes from.” 

Economic benefits include locking in low-priced energy over 20 years. There are also savings related to the avoidance of some capacity and transmission charges—that’s where much of the savings comes from.

Dan Husted, Vice President for Business Development at Lake Region Electric Cooperative

The wind-solar hybrid project is not LREC’s first foray into renewable energy. They also have two fully subscribed community solar arrays (20 kW and 40 kW), as well as an innovative program known as GoWest Solar. The GoWest program provides the opportunity for members to install ground-mounted arrays oriented southwest (rather than due south) to maximize production during peak afternoon and early evening hours of the summer. Members that take advantage of this program receive an extra bill credit during the summer months.

community solar

But wait…what about thermal storage?

Through their Community Storage project, Lake Region is piloting the use of large (80-105 gallon) water heaters as a way to use “excess” energy from the wind-solar hybrid project, in what are effectively thermal storage batteries distributed among members’ homes. 

How does it work? Water heaters are connected to the internet via a Grid-interactive Electric Thermal Storage (GETS) controller—LREC is using the Steffes GETS product in their pilot project. Water heaters have a default charging time of 10 pm – 5 am, when other demand is typically low, and wind energy is typically more plentiful. The water is heated to 140 degrees F, and a mixing valve is employed to ensure that that scalding does not occur. There are control periods in the morning and then again in the evening, when local and transmission peaks typically occur. Other than during the peak times, when electricity is at its most expensive, the water heaters are available to take less expensive energy like wind. 

 

The large size of the water heaters, their high temperature, and the ability of the system to identify and respond to households’ use patterns help ensure that households have hot water when they need it. “We focus on satisfying each individual household's needs for hot water,” emphasized Husted. “We certainly don’t want members to drop off and reduce the program’s value. To advance Beneficial Electrification, we’ve got to keep the customer first.”

In order for a program like this to function, there has to be a communications backbone available for the GETS to function, as the device is connected to the member’s internet via an ethernet connection. It also has to be cost effective for both the co-op and the participating members, given that there are installation and operating costs associated with the technology. The benefits need to exceed the costs. Finally, a challenge that Lake Region has seen in the pilot program so far is that it is more difficult to promote a program for members fed by a single substation than it is to promote programs that can be marketed across the member base.

We focus on satisfying each individual household's needs for hot water. We certainly don’t want members to drop off and reduce the program’s value. To advance Beneficial Electrification, we’ve got to keep the customer first.

Dan Husted, Vice President for Business Development at Lake Region Electric Cooperative

Bringing it all together

In addition to their water heater pilot project, Lake Region has several other programs focused on different technologies with the potential to act as variable loads that can be matched to variable resources. For instance, they have had programs around smart thermostats with targeting for households that use a lot of air conditioning during peak hours. They have also implemented two different rate structures for electric vehicle charging: “Time of Use” and “Electric Storage.” Finally, LREC has more conventional programs for off-peak water heating and space heating, such as for electric thermal storage (ETS) systems. What makes water heaters special, however, is that they are used consistently on a daily basis, year-round, making them ideal candidates for distributed energy storage.

Most important take-away from the program so far? Prioritize solutions for households. According to Husted, “With beneficial electrification, you’ve got to put the customer first.”

LREC_Hybrid-Substation_Dashboard_2020-07-14.jpg

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