Solar Energy Storage: Page 11 of 14

Emerging Technologies, Markets and Applications

What kinds of battery technologies are you specifying in solar storage systems?

Systems must be designed and specified based on the application they are designed to serve. For backup power and off-grid applications, for instance, lead-acid batteries are still one of the best choices. They have a relatively short cycle life of typically 1,000 cycles or less, but they do extremely well in situations for which you need large amounts of reserve power at low cost. Lead-acid batteries can last for approximately 7–10 years if they are operated and maintained well.

Lithium-ion batteries, however, with their much longer cycle life—typically 10,000 cycles or more—and tolerance to “short” cycles, are ideally suited to applications that require frequent partial discharging and charging, such as demand reduction or frequency response applications in which you may discharge and recharge the batteries more often than once per day. In such applications, lithium-ion batteries can also last for 10 years or more, if well cared for. And while they are more expensive than lead-acid batteries in initial  capital outlay, they are, in fact, quite comparable in cost when measured in dollars per kWh delivered over their lifetime.

How will California’s Assembly Bill 2514 impact the deployment of solar storage systems in the state? Does it have any nation-wide implications?

AB 2514 should prove to be the right ignition source for the market at the right time, much like the California Solar Initiative [CSI] program created a runway for driving down costs and increasing system adoption for the PV industry from 2007 through 2013. This effect won’t be immediate, and as was the case with the CSI, the early market will develop more slowly than the later market. As with many things that start in California, the rest of the country learns from our mistakes and successes, and adopts the ideas that work. This trend should prove true for ES systems as well, as the many benefits of their deployment are further proved economically and logistically.

What new business models will be required to accelerate the deployment of solar storage systems?

It may not be so much a shift to new business models as it will be an emergence of new technologies that are deployed through well-understood existing business models. We believe the approaches to ES that have been the standard-bearers for the past 20 years lack imagination. Traditional ES approaches have emerged out of what was technologically possible and affordable two decades ago. Therefore, the traditional ES approach is primarily for off-grid and backup applications based on lead-acid batteries. New approaches and technologies are rapidly supplanting and augmenting this approach, including new types of batteries with longer cycle lives, new applications like demand reduction and frequency regulation, and evolutions in technology that are driving down costs.

Ben Peters

Director of solar finance and policy, REC Solar, recsolar.com

What is REC Solar’s history with solar storage? Are you seeing an increase in customer interest in these systems?

When our company was founded in 1997, solar plus battery storage was one of our primary system types. With the increase in severe storms and questions of grid resiliency, many customers have asked about incorporating storage into their solar project, and this trend will continue.

The most significant growth will come from customer-sited commercial projects. The key factor driving this interest is not the desire to pay for backup power, but the ability to reduce the electric bill with a financed technology package. The continual increase in commercial demand charges requires a new way of designing solar systems. Co-locating storage technology with a solar project significantly expands the portions of a customer’s electric bill that we are able to reduce or eliminate entirely once the system is installed and producing electricity.

The final growth segment is in developing DG-sized projects that incorporate energy storage. These projects are typically less than 20 MW and directly interconnected to the distribution system. Programs mandated by the CPUC [California Public Utilities Commission], PJM grid operators and most recently the Puerto Rico Electric Power Authority are the start of what should be a significant redesign of our electric infrastructure.

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