Solar Energy Storage: Page 3 of 14

Emerging Technologies, Markets and Applications

Darren Hammell

Cofounder and chief strategic officer, Princeton Power Systems, princetonpower.com

What products does Princeton Power Systems offer for utility-interactive PV with integrated storage?

We offer turnkey energy storage systems that combine advanced batteries, converters and controllers. Our power converters can integrate multiple battery banks, and solar, wind and fossil fuel generators with a single converter. The converters can export power and can also run off-grid in an islanded mode while still meeting UL 1741 requirements. Our inverters include many smart-grid features such as peak shaving algorithms, programmable demand response and frequency regulation. We also offer a site controller that aggregates multiple inverters and other assets, and allows a single point of monitoring and control. Our converters are available in power levels of 10 kW–500 kW and can be paralleled into multimegawatt systems.

What battery technologies are compatible with Princeton equipment?

We help our customers choose the best battery for their application and have existing systems in the field with advanced batteries from manufacturers such as Deka/East Penn, Dow Kokam, General Electric, Saft, Samsung, Tesla Motors, ViZn Energy and many others. Our converters are compatible with most chemistries due to their wide operating voltage range of 36 Vdc–600 Vdc.

Are you seeing any emerging trends in the battery technologies that the solar industry is deploying?

Most of the available battery types that are in reliable, cost-effective packages from reliable suppliers have been on the market for several years, though the costs have come down considerably. Many of the newer battery technologies that companies are heavily marketing are not yet ready for wide deployment.

Lithium-ion batteries are now widely available, have exceptional efficiency and performance, and have come down in price significantly over the last few years. The major manufacturers of electric vehicles have all chosen lithium-ion chemistries for their vehicles, which is driving costs down and increasing performance. Other unique chemistries, such as the GE Durathon battery, are also commercially available at attractive price points. Lead-acid batteries are still the most common since they have much lower initial costs, but there are many operating scenarios where their lifetime costs may be more expensive than those of other battery types.

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

PV with storage is ideal in on-grid settings where backup power and resiliency are important, such as community centers, municipalities, schools and other public settings. Adding storage to PV installations can create stand-alone microgrids that are critical to communities in the event of outages caused by storms, wildfires or other events. Grid-connected systems with storage can also provide peak demand reduction, demand response, frequency regulation or other lucrative services.

Where do you think the US solar storage market is headed?

Princeton Power Systems works in three main sectors—microgrids, energy storage systems and electric vehicle charging—that all utilize the same underlying platform. In 2013, we deployed more than 11 MW of these systems in commercial and industrial applications, and we expect this to increase dramatically in 2014. We believe that demand for residential systems may increase in 2014, but it will take longer for widespread adoption in this segment.

There is a huge interest in microgrid systems in the Northeast, especially after the devastation caused by Superstorm Sandy. There is also a large demand across California due to wildfires, high energy costs and other factors. Customers are becoming increasingly aware that one battery system can provide a number of different services. After recent FERC [Federal Energy Regulatory Commission] orders, legislation in California targeting stationary storage and resiliency efforts in the Northeast, we are on the verge of seeing an extraordinary increase in the demand for stationary storage systems with PV.

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