Only three months after world leaders meeting in Paris signed a sweeping deal to reduce greenhouse gas emissions, a team of American scientists has designed a hybrid system that could boost efficiency of coal-powered plants, cutting emissions in half.
Researchers at the Massachusetts Institute of Technology (MIT) are proposing a combined system that has the potential to generate electricity from coal with much greater efficiency — possibly reaching as much as twice the fuel-to-electricity efficiency of today’s conventional coal plants, according to the paper to be published in the May edition of The Journal of Power Sources.
If that proves to be possible, it would mean a 50% reduction in carbon dioxide emissions for a given amount of power produced.
“If we’re going to cut down on carbon dioxide emissions in the near term, the only way to realistically do that is to increase the efficiency of our fossil fuel plants,” MIT doctoral student Katherine Ong said in a statement.
The key, the scientists explain, is combining into a single system two well-known technologies — coal gasification and fuel cells:
Coal gasification, by itself, works at a lower temperature than combustion and is more efficient than burning. First, the coal is pulverized to a powder, which is then heated in a flow of hot steam, somewhat like popcorn kernels heated in an air-popper. The heat leads to chemical reactions that release gases from the coal particles — mainly carbon monoxide and hydrogen, both of which can produce electricity in a solid oxide fuel cell.
In the combined system, these gases would then be piped from the gasifier to a separate fuel cell stack, or ultimately, the fuel cell system could be installed in the same chamber as the gasifier so that the hot gas flows straight into the cell. In the fuel cell, a membrane separates the carbon monoxide and hydrogen from the oxygen, promoting an electrochemical reaction that generates electricity without burning the fuel.
Because there is no burning involved, the system produces less ash and other air pollutants than would be generated by combustion. It does produce carbon dioxide, but this is in a pure, uncontaminated stream and not mixed with air as in a conventional coal-burning plant.
David Tucker, a research scientist at the U.S. Department of Energy’s National Energy Technology Laboratory in West Virginia, agrees. While he was not involved in the MIT research, he believes that exploring unconventional hybrid cycles represents the future of clean energy production in the US.
According to projections by the International Energy Agency (IEA) even with the new agreements in place, global coal-fired power generation will increase over the next few decades. Finding a cleaner way of using that coal, the MIT experts said, could be a significant step toward achieving carbon-emissions reductions while meeting the needs of a growing and increasingly industrialized world population.