Solar Energy Storage: Page 5 of 14

Emerging Technologies, Markets and Applications

What policy shifts or utility cost-structure changes will significantly impact the deployment of storage systems in the US?

Energy storage systems can be a great source for capacity in resource-constrained areas where additional generation is not feasible due to permitting, siting or other reasons, and a full-blown transmission or distribution build-out is highly cost prohibitive. However, to qualify for capacity, many utilities require a 4-hour duration that can make storage systems quite expensive. If the utilities alleviated the constraint to 1 or 2 hours, then the economics for this application could be very interesting, especially considering all the other grid-level services the system can provide. If the generic, one-size-fits-all requirement of 4 hours for capacity payments can be intelligently revised, developers and utilities may open an excellent market for PPA-type storage projects owned by the developer, and controlled and paid for on a fixed-price basis by the utility.

In addition, it will be interesting to see how utilities change tariff structures to compensate for lost revenue associated with the proliferation of DG. An increase in demand charges can play right into the hands of energy storage systems that can quickly discharge to reduce the metered maximum demand on the customer’s meter, and charge during periods of low demand to generate demand savings for the customer. If demand charges do continue to increase, the market for behind-the-meter energy storage will certainly see significant growth.

What are the major obstacles to the expansion of solar storage systems in the US?

An obvious obstacle is still the cost of the systems. This will continue to decline with improvements in battery technology. However, creating market structures that truly enable the unique benefits of energy storage systems to realize a monetary value is also critical. FERC Order 755 is a terrific example of how a market structure is being revised to truly value grid assets that can respond more quickly and accurately, such as energy storage systems, to provide frequency regulation.

[Editor’s note: Xtreme Power filed for bankruptcy protection after our interview was completed.]

Tristan Kreager

Manager of hybrid energy solutions, SMA America, sma-america.com

What products does SMA America offer for utility-interactive solar storage systems and stand-alone microgrids?

SMA manufactures the Sunny Island, a grid-forming,bidirectional, utility-interactive or stand-alone inverter/charger with a 48 Vdc battery bus. Each unit is rated at 4.5 kW or 6 kW and can be networked in various configurations to the MW scale. This solution works in either utility-interactive or stand-alone microgrids. Residential systems range from a single 4.5 kW Sunny Island up to a 24 kW Sunny Island cluster with a 30 kW PV array. Commercial solar storage systems are under development as the market matures. Currently, a single cluster of Sunny Islands in either a 3-phase or split-phase configuration is our fully UL-compliant limit [13.5 kW or 24 kW of load, 36 kW–48 kW of PV, 480 kWh of storage].

As system size increases, a piece of synchronizing switchgear called a Multicluster Box [MCB] is used. Currently, the MCB is not listed for utility interactivity. However, utilizing external transfer switches that are listed for that purpose makes large-scale projects feasible. In the US market, SMA offers the MCB12, which incorporates 12 Sunny Islands configured in four 3-phase clusters. This allows for system capacities of 72 kW of Sunny Islands, 110 kW of PV and nearly 2 MWh of batteries. For even larger projects, SMA offers the MCB36, which is configured for European grids [230/400 Vac, 50 or 60 HZ] and is CE listed. Using voltage transformers, US projects can be built with up to 216 kW of load, 360 kW of PV and 8 MWh of batteries. Our utility-scale storage solutions are custom engineered based on our Sunny Central technology and are primarily aimed at facilitating advanced grid-management requirements.

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