Wind and solar energy has a main flaw: it is unpredictable. It is controlled by the sun and the wind—which have little consideration for the fluctuations of power demand based on predictable human activity. The promise of energy storage has been all the rage of late, including Tesla’s much anticipated home battery and electric cars as storage units. All eyes are on Ireland, where an energy storage plant with an operating capacity of 20MW (enough to power 25,000 homes) is to be laid within the next few weeks. Its flywheel technology will be able to harness kinetic energy from the grid at times of over-supply, releasing it when needed. It is expected that the storage plant, which is scheduled to come online by 2017, will enable Ireland’s power grid to increase it dependence on renewable energy up to 75% v. today’s 50% ceiling.