Coal still produces 40% of the planet’s electricity, and researchers in Germany have figured out a way to make the fossil fuel just a bit more palatable. Their ultra-efficient plant design produces 40% fewer emissions compared to a conventional coal-fired station.
This is important because switching away from coal too quickly could leave an energy gap, where there is not enough green power to meet demand. The U.K., for example, faces this situation in the next decade. Coal-fired power stations and nuclear reactors are set to go offline, while subsidies for wind and solar power have been cut. The country may, says a new study, face a power deficit where demand outstrips supply by 40%.
"You simply can’t close your eyes to coal," GE’s Olivier Le Galudec told GE Reports. "We’ll still need it going forward to provide a good amount of our power."
A new power plant—named RDK8—in Karlsruhe, Germany, has achieved 10% better efficiency than the current German coal-burning plants, reaching 47.1% efficiency. This means less coal needs to be burned for the same power output, and the raised efficiency also means fewer emissions—a huge reduction of 40% "compared to the global average conventional coal-fired fleet," says GE.
The secret is heating the water that drives the steam turbines beyond the normal limits. At the RDK8’s operating temperature of 1,112 degrees Fahrenheit, the pressure reaches 4,000 pounds per square inch. Under these conditions, the water becomes ultra-supercritical steam. This means that the water never boils—it just turns from water to steam, and doesn’t act like either "Instead, it exhibits properties of both at the same time," writes GE’s Mike Keller. "In this state, supercritical steam becomes much more efficient at driving the turbines that spin the electricity-producing generators."
This isn’t the limit, either. Efficiency could still be pushed higher, but even these improvements could "cut yearly CO2 emissions by two gigatons, or the equivalent of India’s annual CO2 emissions," GE consultant Will Viguerie told Co.Exist. However, that figure relies on replacing all of today’s coal plants with the new ultra-supercritical steam plants, which is itself a huge environmental and cost burden—especially for a power source that’s on its way out.