Solar Energy Storage

Emerging Technologies, Markets and Applications

The current buzz surrounding solar energy storage has been gradually building for the last two years. How the storage market will grow and evolve, and how quickly, is not yet clear. However, one thing is certain—the solar industry is entering a dynamic new phase of solar storage market and application development. Established power electronics and battery vendors are positioning themselves for the expected business growth, and new start-ups fueled by successive rounds of funding are aiming to capture a piece of the anticipated market surge.

Today, industry conversations about solar storage often include references to “early market issues.” This may leave integrators who have been at it for a decade or two rather perplexed. Through the 1980s and most of the 1990s, if you were working in solar, you were working with batteries. The introduction of power electronics that allowed utility-interactive systems to operate without batteries was a key advancement that facilitated the mainstreaming of PV generation in the US over the last decade. However, by many accounts PV systems with integrated storage are starting to come full circle, and, in a sense, what is old is new again.

Utility rate structures, gradual shifts in how the utility grid is managed, maintained and upgraded, and regulatory changes are creating new applications and opportunities for PV systems with integrated storage. Furthermore, customer-sited and utility-scale storage will likely become a design requirement for renewables integration in regions with high distributed generation (DG) penetration levels to help manage the impact of variable energy sources on these regional utility grids.

For this article, I conducted interviews with industry stakeholders, including representatives of power electronics vendors, and design and integration firms, to compile a range of perspectives on solar storage, primarily related to utility-interactive applications. My goal was to identify the technological and market developments that are creating a predominantly bullish industry attitude toward the future of solar energy storage in North America.

Eric Carlson

Senior director of grid systems integration, SolarCity, solarcity.com

What markets and applications provide an optimal value proposition for PV systems with integrated storage? How will this evolve over time?

Battery energy storage devices clearly have capabilities that make them attractive as an energy and capacity resource. A PV and storage battery system can provide value on many levels. Storage can provide backup power to homes and businesses, or it can cut peak-demand charges. Energy storage can be used in addition to renewable generators to provide firm peak capacity to the grid. If a grid operator is looking at an area where it might need to replace or increase the capacity of equipment, it could put a battery or batteries in place to meet the demand instead of the traditional infrastructure. Energy storage can also provide frequency regulation and other services that offer value to the grid.

One of the most developed markets for grid-connected energy storage is in commercial retail peak-demand reduction. Because utility tariffs place a high value on reducing demand, especially at peak times, there is an economic incentive to deploy energy storage in certain locations. The optimal candidate for a PV system integrated with energy storage is a commercial site with peak demand occurring during or just after daylight hours and with a high-demand charge, typically from $12 to $20 per kW during peak hours. These customers are typically in either California or the Northeast US. However, across the US, demand charges are increasing at an even steeper rate than energy prices. As more utilities rely on demand charges to help smooth out customer load curves and recover costs, energy storage will become economically viable for more and more customers.

Is SolarCity seeing an increase in customer interest in storage systems? If so, what are the market drivers?

We’re in the pilot phase of our home energy storage system offering in California. We have more than 300 customers either installed or under contract to install storage within that limited pilot, and we hope to expand the scope soon. We see increasing interest in home storage systems, and the most common driving factor is the desire for backup power. As storms and other climate-related disasters have increased in intensity in recent years, more people are interested in securing their own energy to avoid hardships.

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