A new study appears to back up the idea that building more wind power in order to meet peak demand – even if the turbines sometimes produce more energy than the grid needs – could be a better strategy than spending resources on trying to store the energy in batteries.
You might recall that this was the fascinating scenario suggested in a study out of Delaware late last year, which found that at a very high rates of renewables penetration, “over-generation is preferred over more storage because excess generation is more cost-effective.”
Similarly, a new study [PDF] out of Stanford University concludes that “if society aims to increase output of (say) wind energy with the least energetic investment, it is better in many cases to just build another wind turbine, or possibly more transmission lines, than to build a battery to store power that arrives at off-peak times.”
You’ll notice a slight difference with the Stanford study compared to the one out of Delaware – the Stanford researchers weren’t trying to come up with the lowest costscenario like the Delaware researchers, but were instead aiming to minimize energyexpenditure. So what they did was look at the life-cycle energy cost of wind or solar energy (the “energetic cost”), then compared the energetic cost of curtailing excess energy produced versus storing it in batteries.
For wind power, curtailing production – turning off the turbines when the energy wasn’t needed – resulted in a 10 percent reduction in the energy return on investment. But storing the energy in batteries was even more costly, with a 20 percent reduction in return on investment for lithium-ion batteries and 50 percent reduction for lead-acid batteries.
With solar, storage beat out curtailment, for the perverse reason that it takes a lot more energy to build and maintain solar panels than it does wind turbines.
“Both wind turbines and photovoltaics deliver more energy than it takes to build and maintain them,” postdoctoral scholar Michael Dale, a co-author of the study, said in a statement. “However, our calculations showed that the overall energetic cost of wind turbines is much lower than conventional solar panels, which require lots of energy, primarily from fossil fuels, for processing silicon and fabricating other components.”
With this big investment for solar, it makes more sense to pay the high cost of storing the energy produced, rather than simply letting it go to waste through curtailment. Just the opposite of with wind. Or as Dale put it, “You wouldn’t spend $100 on a safe to store a $10 watch,” he said. “Likewise, it’s not sensible to build energetically expensive batteries for an energetically cheap resource like wind, but it does make sense for photovoltaic systems, which require lots of energy to produce.”