Antinuclear

Cheap effective storage for renewable energy – ” pumped hydro”

How pushing water uphill can solve our renewable energy issues  The Conversation, Andrew Blakers Director of the Centre for Sustainable Energy Systems (CSES) at Australian National University 9 July 2014

More and more renewable energy sources are being plugged into Australia’s electricity grids. South Australia, for example, will get 40% of its electricity from wind and solar once the Snowtown wind farm is completed later this year.

But if renewable energy is ultimately to dominate the market, we will need ways to store the energy so we can use it round the clock. The good news is that it is easy to store energy. All you need is two small reservoirs – one high, one low – and a way to pump water between them.

This technique, called “off-river pumped hydro energy storage”, can potentially provide the energy storage that Australia needs to embrace renewables fully. It’s cheap, too.

How pumped hydro works

When there is excess electricity, water is pumped through a pipe or tunnel, to the upper reservoir. The energy is later recovered by letting the water flow back down again, through a turbine that converts it back into electricity. Efficiencies of 90% in each direction are possible.

Pumped hydro is by far the most widely used form of energy storage, representing 99% of the total. Worldwide, pumped hydro storage can deliver about 150 gigawatts, mostly integrated with hydroelectric power stations on rivers………..

There is little opportunity for Australia to develop on-river hydroelectric power, because of environmental and other constraints. But, there are vast opportunities for short-term off-river energy storage. A typical site would comprise a pair of small reservoirs connected by a pipe through which water would be cycled daily, together with a pump and turbine, powerhouse and power lines.

Australia has thousands of excellent potential sites in hilly areas outside conservation reserves, with typical elevation differences of 750 m. They don’t need to be near a wind or solar farm.

Off-river electricity storage has several advantages over typical on-river facilities:

• There are vastly more potential sites
• Sites can be selected that do not clash with environmental and other values
• The upper reservoir can be placed on top of a hill rather than in a valley, allowing the elevation difference to be maximised
• No provision needs to be made for floods (typically a major cost).

A system comprising twin 10-hectare reservoirs, each 30 m deep, with a 750 m elevation difference, can deliver about 1,000 megawatts for five hours.

Between 20 and 40 of these systems would be enough to stabilise a 100% renewable Australian electricity system……..http://theconversation.com/how-pushing-water-uphill-can-solve-our-renewable-energy-issues-28196

July 9, 2014 - Posted by Christina Macpherson | AUSTRALIA - NATIONAL, energy