With the decreasing popularity of coal and increasing volatility of petroleum prices, natural gas is emerging as a major energy resource. And while we have plenty of reserves, an estimated 84 trillion cubic metres, it's still a non-renewable resource that must be used sparingly whenever possible -- like this new natural gas power plant prototype from the Department of Energy. It produces just as much electricity with 20 per cent less gas every time the sun shines.
Natural gas is composed primarily of methane and in 2011, the US consumed more than 680 trillion cubic metres of it, a third of which went towards electricity production -- some 8 trillion cubic metres. The DoE estimates that natural gas will constitute 27 per cent of the national energy supply by the end of the decade. Natural gas power plants operate by burning the gas at temperatures of more than 1090C and using the resulting heat to produce a high pressure gas stream, which spins an electricity-generating turbine. But by augmenting the conventional NG system with a solar concentrating power system's ability to generate heat, plants will be able to produce just as much electricity using a fifth less gas.
The $US4.3 million system developed for the DoE's SunShot Initiative by Pacific Northwest National Lab in collaboration with SolarThermoChemical measures roughly 120cm long by 60cm wide. A circular collection dish concentrates the sun's rays, directing the captured heat across a series of heat exchanging tubes -- each just a few times wider than a human hair. Natural gas flows through these exchanger channels where it mixes with a catalyst and is converted into a more energy-rich form known as Syngas, which is then burned to create electricity. Recent tests have suggested that this solar system can reach 60 per cent efficiency -- that is, 60 per cent of the energy hitting the collection disc is deposited as chemical energy into the syngas.
"Our system will enable power plants to use less natural gas to produce the same amount of electricity they already make," PNNL engineer and project lead Bob Wegeng said in a press statement. "At the same time, the system lowers a power plant's greenhouse gas emissions at a cost that's competitive with traditional fossil fuel power." And when the sun isn't shining, the plant is able to bypass the solar system and burn straight natural gas instead of the synthetic alternative.
The PNNL team believes that it can lower the system's production costs down to 6 cents per kilowatt-hour, the competitive price point of petroleum-based fuels by 2020 -- the same year the DoE estimates that natural gas use will constitute 27 per cent of the total US demand.
But before this production design starts popping up throughout the southwest (the sunniest US region), it will first have to pass the PNNL's field tests in Richland, WA, later this year.