Solar power at night? Yes, with a grain of salt

www.watoday.com.au
November 13, 2009

IN THE past few years, something remarkable has emerged on a dry plateau in the Spanish province of Granada. At the Andasol Power Plant, neat lines of 200,000 mirrors spread across 200 hectares harness the sun's rays. It is the world's largest solar plant - and energy experts are excited not so much by its scale but what it does when the sun goes down. This industrial Spanish power plant has overcome one of the biggest problems facing large-scale solar energy: how to produce electricity at night or when it is overcast. The Andasol plant stores heat from the day in molten salt, which then powers electricity turbines overnight.

The plant can continue for 7½ hours without sunlight, and more advanced plants coming online in the next few years are set to double that storage time. For Australia's solar thermal industry, such breakthroughs are critical because they disprove the old claims that solar energy is too unreliable to run an economy on. As Opposition Leader Malcolm Turnbull said in 2007: ''You cannot run a modern economy on wind farms and solar panels.''

The potential for solar thermal in Australia is huge. John Grimes, the Australian and New Zealand Solar Energy Society's chief executive, says enough sunlight falls on Australia in 40 minutes to power the country for a year. Keith Lovegrove, leader of the Australian National University's solar thermal team, says you could power the country on solar thermal dishes on land measuring 168 kilometres long and 168 kilometres wide. ''If you draw that on a map of Australia, it is a tiny little spot,'' he says.

Solar thermal technology can be used for many things, from heating swimming pools to domestic hot water. In large solar thermal power plants, mirrors are used to concentrate the sun's rays and create heat to warm water or oil. This heat then creates steam to drive electricity turbines - mimicking the steam-driven process inside coal-fired power stations.

Solar thermal's future role in powering Australia is being highlighted by the Run for a Safe Climate, a 6021-kilometre run by emergency services workers from Cooktown to Melbourne to highlight the need for action on climate change. The runners will visit a solar plant in NSW today, and ANU's solar dish next week. Globally, solar thermal is growing, particularly in Spain, where the Government offers generous tariffs, and in the US, where there are favourable tax incentives. The largest project is a 1000-MW plant being built on a US air force base that will generate as much power as a large coal-fired plant.

An international consortium led by the world's biggest re-insurance company, Munich Re, is pushing ahead with a $430 billion plan to supply Europe with solar energy from the Sahara Desert from as early as 2015. Ausra founder David Mills told The Age he was excited by the Andasol plant's breakthrough, as well as US research showing the country's solar and wind resources could cover Americans' hourly energy demands. ''It's very exciting work and, once this is done, people will understand that it is very easy to power modern society with renewable energy.''