Putting Sunshine in a Battery

I am not going to lie — when I first heard about solar battery storage, I was not overly excited. Because I usually work with our efficiency programs – and communicating how our customers can conserve energy and save money – I was way out of my comfort zone. And I’d missed lunch, so I was cranky.

Now that I’ve had some nachos, I’ll do my best to illuminate you on the topic.

You may recall from a previous blog post that SolarTAC officially opened its 74-acre testing and demonstration campus in Aurora, Colo. It’s really big.

SolarTAC offers an opportunity to study issues and solutions related to accommodating large amounts of solar energy on the electric grid. Xcel Energy has installed a large, utility scale battery (also mentioned in the previous blog) energy storage system as part of a three-year test program with Xtreme Power at SolarTAC to evaluate how energy storage can help assist our operating a distribution system. I’ve seen a photo. It, too, is really big.

As solar energy continues to grow in our resource mix, we are interested in better managing it on our power system. Fluctuations associated with cloud cover and other weather-related events can cause the output of solar photovoltaic (PV) resources to drop from 100 percent output to 20 percent in less than one minute and climb back to 100 percent just as quickly. That’s super fast.

Frank Novachek, director of Corporate Planning for Xcel Energy, explained it to me this way: “Imagine a comb turned with the teeth facing toward your head. That’s solar production on a sunny day – smooth and flat like the back of a comb. Now picture the comb flipped. That’s solar production on a cloudy day; big fluctuations that are close together. We are looking at ways to at least partially fill in the empty spaces in between the teeth, to minimize the effects of that variability on the power we provide our customers.”

The power grid works best when it’s fed a nice, consistent supply of electricity to keep the electrons flowing. To improve the ups and downs with solar energy, we need to work with Mother Nature and compensate for her beautifully erratic behavior.

While a comb certainly is an illustrative explanation, I kind of think of the power grid in this way: if you don’t eat all day you get really cranky, and then you eat a heaping plate of nachos, you may feel satisfied – but only for a short period. If you were to eat five small, balanced meals a day, you’ll do much better and be much more productive. The grid likes consistency as well.

We are storing and releasing solar energy produced at SolarTAC in megawatt-scale batteries to better understand how these technologies will be able to help us in the future, particularly as we get more and more solar photovoltaic energy on our systems. We are hopeful that stored energy can make up the difference during those periods when the clouds roll over.

It’s actually a pretty cool thing, a big giant battery full of sunshine (much like my personality).

Article by Tim Laughlin, appearing courtesy Xcel Energy Blog.