Via Gizmag, word comes of one Australian town that is to go solar powered, 24-hours a day. How is that possible?
The technology used will ensure the 10 megawatt Cloncurry solar thermal power station will continue to generate electricity when the sun is not shining and will deliver about 30 million kilowatt hours of electricity a year. Up to 8000 mirrors will reflect sunlight onto graphite blocks through which water will be pumped to generate steam that will operate a conventional steam turbine electricity generator. Because heat stays in the graphite, the system will work through the night and on overcast days. Cloncurry, which is the first town in the State of Queensland to go totally solar, is a perfect candidate for solar thermal power generation, having long claimed the title of having recorded Australia’s hottest day – 53 degrees Celsius in the shade in 1889.
The system is being manufactured by the Australia-based Lloyd Energy Storage. The company has been conducting a feasibility study since 2007. Lloyd says the its steam system uses a once-through steam generator method combined with a air-cooled condensor and turbine. All water used is treated and recycled back through the system. The big deal in this story though is Lloyd’s energy storage system.
The key difference between this new technology and other solar power generation is the ability to store thermal energy at the point of collection and hold it before it is converted into electricity . This means that the storage losses are very low, thus making the system very efficient. The electricity generation system can, if required, run for 24 hours a day and also provide solar power on cloudy days. The solar energy generation facility will comprise a series of solar reflectors called heliostats which track the sun continuously and concentrate the beams of solar energy into a receiver cavity at the base of the storage blocks sitting on the top of small towers, the height of a small rural windmill. The blocks contain heat exchangers through which water is passed to generate steam and electricity using ordinary steam turbine generators. The energy storage system will enable power to be dispatched 24 hours a day if required, compared with conventional solar systems that only generate during sunlight hours.
The blocks are made of high-purity graphite so heat can be moved in and out very quickly. There is no intrinsic link to solar. It also could be used to store energy from wind and wave – really anytime there is a system that generates excess capacity or has a timing mismatch between generation and demand. The technology is the brainchild of Australian scientist Bob Lloyd. The company began as a project in the SMEC (nee Snowy Mountains Engineering Corp.). Lloyd says it has developed and patented a low-cost method of refining low quality graphite to create high quality crystalline graphite for the manufacture and use in the graphite heat storage block.