Solar thermal
Concentrating solar thermal – how it works
Solar thermal energy harnesses the sun’s power to generate electricity by using lenses and reflectors to concentrate the sun’s energy. The concentrated energy is then used to heat a fluid such as water or oil and uses the steam to drive a turbine. This technology is being deployed on a large scale to provide electricity. Storage systems are also being investigated.
The most common solar thermal power stations utilise:
- Compact Linear Fresnel Reflector (CLFR) - modular flat reflectors focus the sun's heat onto elevated receivers containing water. The concentrated sunlight boils the water in the tubes, generating high-pressure steam for direct use in power generation and industrial steam applications without the need for costly heat exchangers
- Trough system – array of linear parabolic concentrator to focus the sunlight into a collector pipe that then pipes the fluid to a central point
- Tower System – a field of tracking mirrors reflects the sunlight onto a centrally located tower containing the fluid
- Parabolic dish system – an array parabolic dish concentrators that focus the sunlight to a point at the focus of each dish to heat a fluid
Greenhouse gas savings
Solar power is a zero-emission electricity source. One megawatt hour (MWh) of solar-derived electricity avoids approximately one tonne of CO2.
In Australia
Australia is blessed with the highest average solar radiation of any continent in the world, which means our solar industry has the greatest potential to lead the world.
Currently there is only a very small number of working solar thermal power systems in Australia. The largest is the Liddell Power station, which uses Ausra’s Compact Linear Fresnel Reflector (CLFR) solar thermal technology, and is a demonstration plant of around 1.5 MW although a larger system is being planned on this site. The CSIRO is also constructing a 0.5 MW solar thermal power station in Mayfield.
With a number of companies evaluating much larger systems in Australia, the commercial deployment of large scale solar power generation could play a significant role in the nation’s renewable energy mix. WorleyParsons have plans for power stations of around 250 megawatts in Australia.
In May 2009 the federal government announced the $1.5 billion Solar Flagships Program to help fund the construction and deployment of up to four large-scale solar power stations of around 250 megawatts of which two can be solar thermal. State governments and private enterprise would add to this fund to enable the deployment of the power stations.
Global View
The US has one of the world’s largest working solar thermal power stations with a 350 MW system dating back to 1985. Rajasthan, India, has 140 MW power station and many other countries either have operating solar thermal power stations or are committed to deploying large scale power stations. Spain is a significant player in solar thermal technology and recently commissioned a 50 megawatt system in 2008. Globally more projects are expected to come on-line in 2009 including one in Morocco.
Current Issues
While the solar the $1.5 billion Solar Flagships Program will have a major impact on the deployment of solar thermal technology in Australia, the Renewable Energy Target will also have a large impact. In 2007 the government committed to ensuring that 20 per cent of Australia's electricity supply would come from renewable energy sources by 2020 by establishing the expanded national Renewable Energy Target (RET) scheme. Draft legislation on the design of the RET was released in December 2008 with the final legislation passed on August 20 2009.
