Options for Energy Storage that Aren't Batteries

Jul 20, 2017

Massachusetts is pushing hard on the renewable energy front, with more than 1600MW solar installed and a target of 1600MW offshore wind energy by 2020. Since sunshine and wind don’t always match consumer demand for electricity, the Commonwealth has set a goal of 200MWh of energy storage capacity by 2020, and is putting more than $10 million into energy storage research and demonstration projects.

The Department of Energy Resources puts the Commonwealth’s total energy storage capacity at just over 7MWh, only 2MWh of which is owned by utilities. That leave 198MWh to go, and it’s not as simple as just buying and installing batteries.

Batteries are one of the leading options, and prices have dropped significantly in recent years. But, at the moment, it would take a two-ton lithium ion battery to store one week’s worth of energy for an average American household.

While a great deal of effort is going into developing cheaper, more efficient batteries, there are also other energy storage technologies worth exploring.

  1. Pumped hydro: One of the most efficient ways to store energy is to pump water to a higher elevation, then release it to drive a hydropower plant when needed. Pumped hydro returns more than 70% of the energy put into it, and can respond rapidly to changes in electricity demand. The primary drawback is the amount of space required.  Massachusetts currently has one pumped hydro plant in Northfield.
  2. Compressed air: It may wound far-fetched, but underwater air balloons were a hot topic at a recent conference on offshore energy. The idea is to use excess wind energy to run a compressor that fills large, underwater balloons with pressurized air. There’s plenty of space offshore, and the weight of the water helps maintain the air pressure. When that energy is needed, a valve opens and the flow of air runs a turbine to make electricity. On paper, this scheme could be as efficient as pumped hydro. It’s currently being tested at commercial scale in Toronto.
  3. Thermal energy: Air conditioning is the leading cause of summer spikes in electricity usage, known as peak demand. A project on Nantucket aims to address that issue two-fold by making air-conditioning more energy efficient, and using off-peak energy to meet the demand. The secret is ice. Units called Ice Bears chill a block of ice at night, when energy demand is lowest, and use it to cool a building during the day. 


  • Galen Nelson Senior Director of Innovation and Industry Support at Mass CEC
  • Rupp Carriveau – Director of the Environmental Energy Institute and Co-Director of the Turbulence and Energy Lab at the University of Windsor