Study: Battery energy storage benefits solar, not wind

Everyone knows energy storage is the key to unlocking renewable energy’s full potential, right? Well, not always, says new research from Stanford University. Utility-scale batteries make sense for storing electricity from large solar power systems, but not wind farms, according to analysis published in the journal Energy & Environmental Science.

If true, this research could undercut one of the most promising opportunities to solve intermittency concerns from renewable power sources and better integrate wind and solar onto the grid.

Can Energy Storage Solve Intermittency Issues?

Energy intermittency from renewables (meaning the relative unpredictability of the wind blowing or the sun shining) is one of the biggest challenges facing our transition to a clean energy economy.

Grid operators are most concerned with reliability, and they often overlook the climate and pollution issues that come from running coal and natural gas plants around the clock as baseload power resources.

While incredible technological advances in the ability to forecast weather and renewable output are happening today, there are still times when solar or wind output don’t match demand – which freaks out grid operators.

That’s where energy storage comes into the picture. Technologies like pumped-hydro storage or large battery systems can be paired with solar and wind to capture whatever power they generate whenever it’s available, providing grid operators with confidence it’ll be available when they need it to meet demand.

What’s EROI And Why Does It Matter? 

As more and more renewables come online, large batteries have become more and more attractive as an energy storage option. But as with most developing technologies, they’re often expensive, and thus Stanford’s research focus.

The Stanford scientists examined the energy return on energy investment (EROI) ratios of using several technologies to store solar and wind energy. The EROI calculation is relatively simple – the amount of energy produced by a technology divided by the amount of energy required to build and maintain a storage system.

“Batteries with high energetic costs consume more fossil fuels and therefore release more carbon dioxide over their lifetime,” said lead author Charles Barnhart. “If the battery’s energetic cost is too high, its overall contribution to global warming could negate the environmental benefits of the wind or solar farm.”

Based on this formula, many battery technologies may not provide a positive EROI when used for wind energy. “Both wind turbines and photovoltaics deliver more energy than it takes to build or maintain,” said co-author Michael Dale. “The overall energetic cost of wind turbines is much lower than conventional solar panel.”

Stanford’s EROI found the energy demands of solar power installations comparable to the energy demands of the five leading battery technologies. But wind farms, since they require less energy to build and maintain, significantly reduce EROI from 20-50% depending on the energy storage technology.

That’s a problem for wind power, because curtailment – shutting off the turbines when they’re generating too much power – only reduces EROI by 10% “For wind farms, the energetic cost of curtailment is much lower than it is for batteries,” said Dale. “It would actually be more energetically efficient to shut down a wind turbine than to store the surplus electricity it generates.”

But Hope Still Springs Eternal

But while that reality may be true, it doesn’t comport well with our need to get off fossil fuels to cut emissions and slow climate change. Fortunately, the Stanford researchers do see several options to make the EROI of energy storage via batteries work for both wind and solar generation.

Increasing battery life cycles is the most effective way to boost EROI, according to the study, but the goal is high. The Stanford researchers estimate batteries must endure 10,000-18,000 cycles to efficiently store energy on the grid – but conventional lithium-ion batteries only last 6,000 cycles and lead-acid batteries only 700 cycles.

Pumped-hydro energy storage performs best of all the available options, providing an EROI 10 times better than conventional batteries, but with limited deployment options. Other options like vehicle-to-grid technology also hold promise, according to the researchers, and could grow in scale as more electric vehicles hit the road.

http://cleantechnica.com/2013/09/13/study-battery-energy-storage-works-for-solar-but-not-wind/