Sun to Battery: Real-Life Testing of Solar Storage

I think it would be a system operator’s nightmare. You’re responsible for keeping everyone’s lights on, but a passing set of clouds cuts the output from several solar arrays from 100% to 20% — and then raises it back up to 100% in less than a minute.

Fluctuations like that would put me in the hospital if I were a system operator, which fortunately for you all, I’m not.

Not for the faint of heart

From that system operator’s perspective, solar power can cause voltage swings, grid instabilities and shortfalls in meeting demand. Talk about stressful. Especially when your company is ranked No. 5 for solar capacity in the U.S. — and ramping up for more.

Another characteristic of solar is that its daily generation tends to peak before customers’ power use peaks, typically in the early evening hours when people get home but office buildings are still using their regular daytime power.

As more solar arrays come online — both rooftop and utility-scale — we need a reliable, cost-effective way to store all that great sun power and keep power distribution steady. Utility-scale batteries can supplement the grid during rapid fluctuations and “extend” solar energy to cover customers’ peak demand.

Commercial viability

Battery technology has come a long way in recent years, but with something as important as the power grid at stake, Xcel Energy is testing a utility-scale battery in a real-world setting before deploying the technology in other locations.

The 1 MW advanced dry cell lead-acid battery has a “round-trip efficiency” of more than 90%, meaning that only 10% of the energy used for charging is lost to the charging process. The technology also has a very fast response time to handle the quick fluctuations in solar power.

The demonstration is taking place at the Solar Technology Acceleration Center (SolarTAC) in Aurora, Colorado, where participating companies can test their technologies in a real-world setting to see if the products are ready for market or need improvements first.

Good for the environment – and the grid

This isn’t just a “cross your fingers and hope it works” test. The partners involved view it as a pivotal demonstration of the commercial viability of energy-storage systems, particularly of the new advanced lead-acid battery.

Lead-acid? Sounds more like Pepto Bismol for those system operators.

Article by Sheila Knudtsen, appearing courtesy Xcel Energy Blog.