Emerging technology assessments aim to deliver benefits of solar and storage to disadvantaged communities

Posted to EPRI in the Utility Management Group
Samantha Gilman's picture
Communications Manager Electric Power Research Institute (EPRI)

Samantha Gilman is the communications manager for the Power Delivery and Utilization sector at EPRI. Samantha has spent a decade in communications, public relations, and digital marketing within...

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  • Nov 5, 2021

This article appeared in EPRI's Efficient Electrification newsletter and written by EPRI staff. You can sign up to receive future issues here.

As the nation’s electric power system incorporates increasing amounts of renewable energy and distributed energy resources (DER), stakeholders and policymakers are working to ensure that low-income communities reap an equitable share of the financial and environmental benefits. There are substantial reasons why this is a priority. For example, low-income households have an energy burden – which is defined as the percentage of income spent on electricity, gas, and other energy expenses – three times higher than non-low-income households.

DER, such as rooftop solar, have the potential to reduce electricity bills while also improving overall air quality in neighborhoods that have been disproportionately impacted by pollution. But what will it take for the developers and operators of affordable housing projects in disadvantaged communities to reap the maximum economic benefits of solar and other DERs? Are there complementary technologies, such as energy storage and smart building controls, that can help deliver those benefits? And is there a way that increased deployments of DER at affordable housing developments can also provide benefits to the operators of local electric grids?

These and other questions are being addressed as part of ongoing research funded by the California Energy Commission (CEC) and Southern California Edison (SCE). The project is being led by EPRI and includes non-profit affordable housing developer LINC Housing, and a host of other research partners. The initiative involves the installation of 120 kilowatts of bifacial solar panels as well as two 60-kilowatt/120-kilowatt-hour battery systems at the multifamily Mosaic Gardens at Willowbrook affordable housing development in Compton, California, just south of downtown Los Angeles.

For the CEC, the project was a chance to better understand the barriers that low-income and disadvantaged communities face when considering adopting clean energy. “This was an opportunity to demonstrate the viability of how a package of technologies with integrated solar and storage can provide direct bill savings to the residents while demonstrating how the aggregated operation of several communities like Willowbrook along the same circuit can benefit the electric grid,” said Liet Le, who works in the CEC’s Energy Generation Research Office.


An opportunity to test innovative technologies

Built in 2017, the Willowbrook development achieved LEED Silver certification and includes a total of 61 units, including 31 for residents transitioning from homelessness. In addition to the solar and storage, the project includes a DC-coupled bidirectional inverter, native DC lighting, and DC-enabled space heating and cooling loads in the complex’s common area. The project also includes a system controller to coordinate the operation of the solar, storage, and inverter.

As of early September 2021, the bifacial solar and storage installations were complete and fully commissioned and data about their performance were being collected and analyzed. In addition, about a third of the residents at Willowbrook were participating in a voluntary behavioral demand response (DR) program conducted by the software company, OhmConnect.

By participating in the DR program, residents receive advance notifications about the optimal times to manage their energy use. This is important because Willowbrook residents will be transitioning to time-of-use (TOU) electricity rates at the beginning of 2022. TOU rates mean that when customers use electricity is also a factor in their energy expense, not just how much electricity they consume. Responding to DR notifications can lower their bills.

The deployment of a mix of innovative DER technologies and the opportunity to learn more about how customers can provide potential grid benefits through managed behavior were big reasons SCE decided to participate in the project. “These are emerging technologies that you can’t just buy off the shelf and the whole point of a field demonstration is to see how you can put them all together,” said Mark Martinez, senior portfolio manager of emerging markets and technologies at SCE.

Martinez was also interested in learning how affordable housing complexes, or any buildings with DERs, can become local grid resources and how the utility can design new programs and rates to help. “Someday most, if not all, new buildings in California will have batteries and solar and other smart technologies. We want to know in advance what we can expect them to do and how to design future programs and rates that reflect the larger needs of both customers and the grid while supporting those who have DERs,” said Martinez.


Engaging Willowbrook residents

Although the project is ongoing, EPRI’s analysis has already yielded some helpful takeaways that can inform future program design. There were a few early lessons showing the difficulty of getting residents to understand and sign up for the demand response program. Not surprisingly, the current pandemic made in-person recruitment difficult. Other challenges included the lack of mobile devices and computers among some residents and the complexity of having third parties actually paying the utility bills of certain residents.

Despite those obstacles, about a third of Willowbrook residents did sign up to receive notifications that prompted them to reduce their electricity usage when the wholesale market prices were particularly high. OhmConnect bids into the California Independent System Operator’s (CAISO) Demand Response Auction Market (DRAM) market and provides a portion of those revenues to demand response participants who reduce their usage. “The recipients of the messaging have reduced their energy usage compared to their baseline,” said Agatha Kazdan, an EPRI senior technical leader, who is managing the project.

Making it easy for residents to monetize their participation in demand response has been effective. “If they participate with OhmConnect, they can accrue points for taking actions to lower their electricity usage in response to notifications and cash out those points using PayPal,” said Kazdan. “If you were somewhat responsive to notifications and reduced your energy usage, you could expect $100 a year and if you were very active it could go up to $200 or $300, in addition to the bill savings.”


The financial viability of energy storage

Another important research objective of the project was to assess the economic feasibility of incorporating energy storage along with rooftop solar. Like other affordable housing developers in California, LINC Housing has significant experience installing solar on its projects but far less with behind-the-meter storage systems. Many new commercial and multi-family buildings in the state may soon be required to install both solar and energy storage as part of the California building code. For this reason, it was important for researchers in the project to review the full lifecycle costs associated with storage from the perspective of the multifamily property owner.

The early lessons from the Willowbrook project highlighted EPRI’s observation that the financial viability of incorporating storage at affordable housing projects may be premature.

“There was limited investment benefit from the battery installation to the property owner or to the tenants,” said Ram Narayanamurthy, an EPRI technical executive whose work focuses on the decarbonization of buildings and communities. “In fact, the operating maintenance contract for the storage system is more expensive than the forecasted energy savings of this specific installation.”

However, because the battery at Willowbrook is connected to the project’s common area, it could provide backup power and create a resiliency center during local outages. As part of this project, researchers are exploring technologies that could enable this concept, such as an automatic transfer switch that allows DC loads to operate with electricity from the solar and storage system instead of the grid.


The use of innovative emerging technologies

Bifacial solar panel modules have become a popular choice for large utility-scale solar projects. That is because they generate electricity both from the direct sunlight that hits the front of the module as well as from light reflected from the ground or rooftop to the back of the panel.

For the Willowbrook project, the targeted efficiency for converting solar to electricity with the bifacial system was 23 percent. But there were challenges to reaping the potential generation of bifacial modules because there was not enough flat roof space. That meant that some of the bifacial modules had to be installed on a sloped, asphalt-shingled roof, which minimized the efficiency of the module’s back panels.

Because all of the modules installed at Willowbrook shared the same inverter and maximum power point tracking (MPPT) channel, the overall performance of the bifacial panels was degraded. In the future, though, the use of microinverters and power optimizers could help maximize the potential of bifacial modules.

Understanding the benefits of utilizing DC-powered appliances for the air conditioning and lighting in Willowbrook’s common area was another important research priority. “This is a way to reduce conversion losses that take place when you go from DC to AC by directly utilizing electricity from the battery rather than converting it,” said Narayanamurthy. “There’s a lot of potential here because one third of residential loads around the U.S. are native DC.”

There is also the potential for reduced infrastructure costs, due to reduced inverter capacity requirements when large loads, such as a heat pump, connect directly to a battery. While the technology is promising, the fact that it is nascent also presented challenges because many of the products lack the UL certifications that are required by building and safety inspectors.


Reducing peak circuit load

What’s more, EPRI completed a distribution circuit system analysis. Among other things, EPRI’s analysis modeled whether a host of multi-family buildings equipped with solar and storage, and the ability to respond to TOU rates, could reduce the annual peak load of a common feeder by 10 percent.

The annual peak load of the SCE feeder circuit that Willowbrook is connected to is eight megawatts, so EPRI’s modeling analyzed whether 16 hypothetical housing developments similar to Willowbrook could limit the peak load to 7.2 megawatts. Not only did the analysis find that a 10 percent peak load reduction was possible, but it also found that operating the solar and storage in a way designed to reduce the peak load on the circuit would yield bill savings of nearly $900,000 per year.


Planning for the Future

Data collection and analysis by EPRI will continue at Willowbrook through the early part of 2022. Mark Martinez at SCE says that he will use the lessons from this and other EPRI projects in the utility’s future DER forecasting and modeling work. “This is a way to see how smart building systems with DERs can be responsive to future dynamic rate designs,” said Martinez. “These projects help identify opportunities for future models of DER programs. This and other projects will continue to help us understand how future customer solar and storage systems can provide local grid reliability, and what we can do to help our customers maximize their benefits.”

For its part, the CEC will use the lessons from this and other demonstration projects to evaluate various technology options and business models to enable cost-effective, reliable, and grid-supportive community-scale solar and storage. For example, Liet Le says the use of bidirectional ports to interconnect various power sources – like the grid, solar, and batteries – and AC and DC loads minimized conversion losses and necessary equipment. “We will continue to evaluate the use of bidirectional ports to integrate directly with electric vehicles to decrease the cost and streamline the process for installation and interconnection of solar paired with storage in low-income and disadvantaged communities,” said Le.



Founded in 1972, EPRI is the world's preeminent independent, non-profit energy research and development organization, with offices around the world.
Matt Chester's picture
Matt Chester on Nov 5, 2021

Another important research objective of the project was to assess the economic feasibility of incorporating energy storage along with rooftop solar. Like other affordable housing developers in California, LINC Housing has significant experience installing solar on its projects but far less with behind-the-meter storage systems. Many new commercial and multi-family buildings in the state may soon be required to install both solar and energy storage as part of the California building code. For this reason, it was important for researchers in the project to review the full lifecycle costs associated with storage from the perspective of the multifamily property owner.

Did CA do their own cost analysis on this measure before putting it into motion? I'm curious how the EPRI conclusions compared quantitatively with what they put out publicly? 

Samantha Gilman's picture
Thank Samantha for the Post!
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