冷凝器镀层可以使发电效率更高

Most of the world's electricity-producing power plants -- whether powered by coal, natural gas, or nuclear fission -- make electricity by generating steam that turns a turbine. That steam then is condensed back to water, and the cycle begins again. But the condensers that collect the steam are quite inefficient, and improving them could make a big difference in overall power plant efficiency.

Now, a team of researchers at MIT has developed a way of coating these condenser surfaces with a layer of graphene, just one atom thick, and found that this can improve the rate of heat transfer by a factor of four -- and potentially even more than that, with further work. And unlike polymer coatings, the graphene coatings have proven to be highly durable in laboratory tests.

The findings are reported in the journal Nano Letters by MIT graduate student Daniel Preston, professors Evelyn Wang and Jing Kong, and two others. The improvement in condenser heat transfer, which is just one step in the power-production cycle, could lead to an overall improvement in power plant efficiency of 2 to 3 percent based on figures from the Electric Power Research Institute, Preston says -- enough to make a significant dent in global carbon emissions, since such plants represent the vast majority of the world's electricity generation. "That translates into millions of dollars per power plant per year," he explains.

There are two basic ways in which the condensers -- which may take the form of coiled metal tubes, often made of copper -- interact with the flow of steam. In some cases, the steam condenses to form a thin sheet of water that coats the surface; in others it forms water droplets that are pulled from the surface by gravity.