Washington, Nov 18 : An analysis by MIT (Massachusetts Institute of Technology) researchers has suggested that in order to lower down the cost of coal-fired power plants, 'partial capture' of carbon dioxide (CO2) emissions by plants would mean less costly changes in plant design and operation.
"Our approach - 'partial capture' - can get CO2 emissions from coal-burning plants down to emissions levels of natural gas power plants," said Ashleigh Hildebrand, a graduate student in chemical engineering and the Technology and Policy Program at MIT.
"Policies such as California's Emissions Performance Standards could be met by coal plants using partial capture rather than having to rely solely on natural gas, which is increasingly imported and subject to high and volatile prices," Hildebrand added.
The United States is facing a pressing need for more power plants that run essentially all the time.
Renewable sources aren't suited to the task, nuclear plants can't be built quickly enough, and expanded reliance on natural gas raises price and energy-security concerns.
Coal, which now supplies more than half of all U.S. electricity, seems the best option.
But as several states have started to regulate CO2 emissions, and others are expected to follow suit, some of the luster has come off coal.
Amid the uncertainty, no one wants to be the "first mover" on building a new coal plant incorporating carbon capture and storage (CCS).
Depending on the type of plant, carbon capture alone can increase the initial capital cost by 30 to 60 percent and decrease plant efficiency so that the cost per kilowatt-hour rises.
That high cost would reduce - or possibly eliminate - the hours the plant will be called on to run. Plus, CCS hasn't been proved at full scale, so no one knows exactly what to expect.
Hildebrand and Howard J. Herzog, principal research engineer at the MIT Energy Initiative, modeled the technological changes and costs involved in capturing fractions ranging from zero to 90 percent.
The model confirms that the cost per ton of CO2 removed declines as the number of captured tons increases.
Not surprisingly, when the second series is added, cost per ton goes up, but it then quickly levels off. Cost per ton is thus roughly the same at, say, 60 percent capture as it is at 90 percent capture.
The researchers conclude that as a near-term measure, partial capture looks promising.
New coal plants with lower CO2 emissions would generate much-needed electricity, while also demonstrating carbon capture and providing a setting for testing CO2 storage - steps that will accelerate the large-scale deployment of full capture in the future.