Solar Energy Storage: Page 9 of 14

Emerging Technologies, Markets and Applications

David Love

Account executive, Ameresco Solar,

What is Ameresco Solar’s history with solar storage systems?

A significant portion of our business is battery based, from small single-battery systems to larger off-grid hybrid applications. While we certainly develop grid-tied systems, the more interesting projects tend to be battery based. For example, we recently completed a 67 kW off-grid project to operate a municipal water system near Peach Springs, Arizona. The remote ac-coupled system operates multiple pumps during daylight hours and also charges a 6,000 Ah at 48 Vdc VRLA battery bank to operate the pumps and controls overnight. We selected Deka Unigy II sealed AGM batteries due to the compact footprint and good product track record. The system pumps 20,000 gallons per day over a pipeline network that is more than 30 miles long.

How can financing mechanisms accelerate the deployment of solar storage systems?

In the past, a barrier to battery-based systems was finding lenders that would offer a loan with a long-enough term at a reasonable rate across all US states and territories. Ameresco Solar now offers a solar loan through our installers for all residential solar projects, including battery backup and off-grid applications. The term of up to 15 years with zero down allows for a reasonable monthly payment, especially compared to the operating costs of fossil-fueled generators.

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

Change is the only constant. Currently we see a desire for off-grid and battery-backup systems. With a change in utility pricing, policy or utility availability, however, we will see new markets appear. The promised new battery technology may find a place at the table as well. Emerging markets will be in Hawaii due to the high cost of utility power and grid saturation there, as well as in California. For some commercial customers with critical loads, I can see the advantages for a standby battery bank to bridge the load between the utility and a backup generator. These systems are often large, and the end user needs to value the continuous power and be willing to pay a premium for that service.

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

One obstacle for residential and small commercial projects is simply training electricians and designers to size systems and set expectations for the end user. Most people do not understand the current limitations related to the size and cost of a lead-acid battery bank. While we see some newer battery technologies making progress on the size, weight and cycle life, standard lead-acid batteries are still an economical choice for many applications. People should not wait for the “magic battery” to appear, since it has been “just around the corner” for a long time. It’s better to complete the system now.

Tom McCalmont, PE

President, McCalmont Engineering,

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

As an engineering firm specializing in large-scale solar projects, we often see interest in integrating energy storage [ES] with PV projects. There has been a significant uptick in this interest during the last 2 years. We believe this increased interest is the result of three parallel drivers: need, cost and technology.

The obvious solar advantages of simplicity, no moving parts, lack of toxicity, and “free fuel” have recently been augmented by falling prices to bring great economics to solar projects. However, solar suffers from one significant disadvantage, which is intermittency. We categorize intermittency in terms of three distinct challenges:

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