A joint venture of solar panel manufacturer Suniva and storage developer GS Battery aims to bring battery back-up (but still grid-tied) solar into the limelight once again. Inefficient battery storage has encouraged small-scale solar generation to rely entirely on the grid for auxiliary power. Battery systems can cost nearly twice as much as straight grid-tied systems, depending on the needs of the system, and the batteries themselves are often not eligible for cost-reducing solar incentives. (Though beginning this year, battery systems are eligible for the 30 percent federal ITC.) They also take up a ton of space, which is something many homes and small commercial installation sites don’t have on hand. The Suniva-GS system will use deep-cycle nanocarbon batteries to achieve high performance. The demo system will be 30 kw in capacity with a 3,000-amp hour battery component.
Let’s get into the battery vs. grid-tied debate a bit further. Up until ten or fifteen years ago, home solar energy systems with a battery storage component were the norm, even though utilities in the United States have had to allow independent electric generation facilities to connect to the grid since 1978. But it wasn’t until 2005 that the Federal Energy Regulatory Commission (FERC) introduced interconnection standards for systems under 20 MW, making it much easier for states to build their own such standards and speed up the installation and permitting process for solar energy systems.
Interconnection standards do not net-metering make: it’s up to an individual state to require its utilities to compensate independent electric generators for the energy they feed into the grid. Most states do now have net metering laws in place (all but six states offer some form of net-metering, whether state mandated or in some cases by the utilities’ own initiative–the Pew Center on Global Climate Change maintains an easy to read map of which is which).
Not all net-metering programs are created equal: in some, you get compensated for your net-excess generation (NEG) at the rate at which you purchase electricity from the grid, an even exchange and perfect offset. In this instance, the utility is basically acting like a perfectly efficient “battery”.
In some net-metering programs, however, the utility is allowed to compensate you for your NEG at a rate lower than that at which you purchase electricity from them. This can be either a lower-tier rate or, worse, an avoided cost rate. “Avoided cost” is the estimated cost of production per kilowatt-hour (kWh) that the utility avoids paying because, well, you’re producing that kWh for them for free. So they pass on their savings to you, but not a penny more. In this type of net-metering program, you’re not getting full value for every kWh of electricity you produce. It’s therefore more cost-effective to store any NEG on-site and either use it when you need it or–and this is where smart-grid technology and time of use meters are game-changing–sell it back to the utility when you can get a better price for it. Here’s where efficient, more affordable batteries could seriously make a positive difference to solar’s ROI.
All of which is to say, we’ll be keeping an eye on Suniva and GS Battery’s collaboration, as well as on other new battery solutions as they emerge.
Storage is measured in Watt-hours, not in amp-hours. How much would a 3,000-amp hour (or 36 kWh in capacity, assuming 12V) battery cost, before ITC and other incentives? By the way, that battery would be barely enough for 2 kW off-grid system (as solar generates, on average in California, less than 4 hours a day at peak capacity – 1 KW-rated PV system typically generates less than 1460 kWhs AC a year there).