On the Portuguese island of Madeira in the Atlantic, the inhabitants are converting an irrigation system from the 15th century into a future-age energy storage facility. For 600 years the rainy north of the island has been linked to the populous but dry south by a series of small canals. In a first step, a number of hydroelectric power stations were incorporated into this network to generate power for locals and tourists alike. But the system has a serious drawback: if the rainfall is sparse in summer, the hydroelectric plants have to be throttled back or even closed down. The ingenious solution the Madeirans have come up with is to use the energy from large-scale wind turbines to pump water into underground reservoirs and use it for storing energy in rainless periods.