What’s the future market for grid-scale energy storage? Not nearly as big as previously assumed, according to Pike Research. The research firm has adjusted its expectations for the market for grid-scale batteries, flywheels, air and hydro storage reservoirs and other energy (and power) storage technologies from a previous estimate of $35 billion by 2020 down to $22 billion over the next decade. At the heart of the reduced estimate are some updated figures from the utility-backed research group, the Electric Power Research Institute, that lay out a pretty tough and complicated path forward for energy storage technologies seeking to justify the cost of their investment with today’s grid economics. That’s too bad, because the grid could really use the backup storage capacity to help manage the flood of on-again, off-again power that wind farms and solar power plants will be providing to it in ever-increasing amounts over the next decade. Pike predicts that nearly half of the growth to come in grid energy storage will be to help manage those intermittent power generation resources. Interestingly, Pike has named flow batteries — energy storage systems that share some characteristics with fuel cells, in that they use a pumped electrolyte material to recharge — along with pumped hydro systems as the two top contenders for major growth in grid energy storage over the next decade.