An Australian solar thermal technology developer says it can provide concentrated solar thermal energy to outback and remote locations for just 8c/kWh, and hopes to sign for its first two commercial projects within the next few months.
Graphite Energy, an Australian company privately owned by an un-named “entrepreneurial family”, has been operating a 3MW solar thermal power plant at Lake Cargelligo, in western NSW, for the last couple of years.
Concentrating solar thermal technology differs from solar PV because it captures the sun’s heat and uses it to generate steam – just like fossil fuel generators. The key to its success comes in its ability to do this efficiently, at high temperatures, and at low cost.
Various technologies exist, such as parabolic troughs, power towers and flat-mirrored linear fresnel. The distinguishing feature of Graphite Energy’s technology (seen at right) is that it uses graphite receivers that are mounted on towers to collect heat reflected from a field of heliostats (mirrors), and its ability to store energy via heat exchangers gives it an “in-built” storage option that delivers “dispatchable” energy.
And the company is about to take this technology to market, but not in the way that most would expect.
One thing it has learned is that, unlike other CSP technologies, it does not have the cost structure to be able to install more stand alone power plants. “It’s an expensive way to boil water,” Gary Baddlock, the chief operating officer of Graphite Energy, told an international symposium on concentrating solar power at the CSIRO Energy Centre in Newcastle on Wednesday.
But it does offer a cheap way of doing what he calls the “high end” of the technology, by “superheating” waste heat, for instance, and using this to produce energy.
Baddlock notes that this has attracted the interest of two potential customers in remote areas of Western Australia. The details are being kept confidential for the moment, but they are most likely mining related, as the load requirements of the client need to be at least 15MW to be worthwhile.
Baddlock says that by adding the solar technology, and its storage ability which can provide stable output over a 24 hour period – diesel consumption at a remote location could be reduced by 15 to 30 per cent. Given that diesel-fired power plants cost at least 30c/kWh, and sometimes more than 40c/kWh depending on location, the option to replace at least some of this with an 8c/kWh power source should be attractive.
Baddlock says by integrating waste heat and solar thermal, and focusing on the “last 20 per cent” of the heating process, this will deliver thermal to electrical efficiency of more than 50 per cent, and a solar to electricity efficiency of around 30 per cent, and explains the dramatically cheaper levellised cost of energy” over other applications. (Most solar thermal technologies are bracketed around 25c/kWh)
He says the technology can be used as a booster to lift the temperature of steam, and the efficiency of steam cycle turbines by between 7 and 15 per cent.
The company’s initial target markets are for boosting combined cycle gas turbines where the avoided cost of fuel is greater than $10/GJ (and has some spare land), and on remote mining locations which burn high cost diesel, which is offering the best short term opportunities. Indeed, there are a number of projects combining solar with diesel or gas in remote locations that could be announced in the coming year, some with help of funding from institutions such as the Australian Renewable Energy Agency, which has identified hybrid systems as one of its priorities.
Overseas opportunities for Graphite Energy are seen in the US, where the company would focus on integrating its technology with CCGT and cogeneration plants, or even to extend geothermal plants; and in Saudi Arabia, where it would look at hybrid facilities or stand alone solar thermal plants acting as superheaters.
“We believe we have got a compelling solution for solar thermal,” Baddlock says. “We feel we have found the essence of where the true value is. Now it’s about getting out there and getting projects.”
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