The need for water as energy storage for better integration of renewables is a policy brief produced by the United Nations University Institute for Integrated Management of Material Fluxes and of Resources (UNU-FLORES) in colloboration with the International Hydropower Association (IHA) and the Centre for Environmental Design of Renewable Energy (CEDREN).

The brief follows a seminar on the subject convened by the three organisations at 2014 World Water Week in Stockholm, Sweden.

The brief explores water as energy storage in the context of the water–energy nexus, and how the planning, operation and management of storage or pumped-storage hydropower needs to adopt a nexus perspective.

It includes three case studies:

• The island El Hierro, Spain: 100 per cent renewable energy by integrating wind and solar energy with pumped hydro on a small scale
• Integration of wind and hydro power in Ethiopia: large opportunities for a developing country
• Hydro as a carrier for both off- and on-grid electrification and as energy storage for better integration of renewables in Mozambique