In a country as dry as Australia, water is one of our most valuable resources.
Water is also required in large quantities for many forms power generation – whether in direct consumption or for cooling purposes.
According to the American Wind Energy Association, to generate one kilowatt hour of electricity from nuclear power 2.3 litres of water are needed. Coal requires 1.9 litres and oil consumes 1.6 litres.
While solar power and wind energy are overwhelmingly green by general comparison when it comes to power generation, considerable amounts of water are also needed for the most (currently) cost-efficient type of large-scale solar farms – those that utilise concentrated solar power; also known as CSP.
Some CSP technology utilises rows of curved mirrors focus heat onto a tube filled with oil which boils water to make steam, in turn spinning a turbine a turbine – this is called a trough system. Another uses reflective mirrors called heliostats to reflect and concentrate sunlight onto liquid-filled tubes used to generate steam and spin turbines.
In the case of trough technology, the water footprint is considerable – around 3.6 litres per kilowatt hour. Heliostat and other CSP technologies use far less, but the problem of using water in desert conditions, where many of these plants are located, remains.
One breakthrough we reported on last week is being used in Israel – still based on a water-based cooling system, but provides hot water suitable for use in homes. This could be an excellent option where the farm is very close to residential areas; but where it’s placed outside a township, the energy in pumping the water to households couple with heat loss in transit may make it unviable.
Wind power uses the least water – around 4 millitres per kilowatt hour and that’s just to keep the turbine clean. But wind isn’t always suitable in still desert-type conditions.
While still more costly than other forms of solar and wind power per kilowatt, when it comes to water, solar panel based solar farms appear to be by far the most water friendly at 110 millilitres per kilowatt hour – again, this water is used primarily for cleaning solar panels.
Cost can be a very relative concept when it comes to the elixir of life. In some places in Australia where water is abundant, CSP technologies may be the cheapest options, but environmentally and financially speaking in other regions it may be still far cheaper over the long term to implement photovoltaic based large scale power production.