An Energy Department-backed project is using supersonic shock-wave technology used in jet engines to compress carbon dioxide for storage at coal-fired power plants and other industrial sites.
The goal: Develop the cheapest, fastest and most efficient compressors.
Compression is crucial to capturing CO2 and storing it deep underground or reusing it. But compressing CO2 to pipeline levels -- 100 times the normal pressure of the atmosphere -- consumes enormous amounts of energy.
How much energy? Using carbon capture and storage (CCS) technology, including compression, at a coal-burning integrated gasification combined cycle (IGCC) power plant reduces the net electric output of that plant by 8 to 12 percent, DOE says.
Enter Ramgen Power Systems, a Bellevue, Wash.-based technology developer. With DOE assistance, the company is working on a CO2 compression system based on using shock-wave technology.
"There's existing technology that will [compress CO2], but it ends up being enormous machines and expensive," said Jarlath Hume, the company's vice president for government relations. "Our machine is much, much smaller and much cheaper, both in capital and operating costs."
Supersonic jets are propelled by air moving through a narrow part of their engines at supersonic speeds, creating shock waves that compress air and create a forward thrust. The company is applying that idea to CO2 compression. It uses a rotating disk to move the gas at the speed of sound, creating shock waves that compress the gas.
"It's clever," said Rich Dennis, the turbine technology manager at DOE's National Energy Technology Laboratory. "They took the whole concept of fluids moving at the speed of sound and set up shock waves to compress fluid gas and then put it in a rotational reference frame."
The result: a system that compresses CO2 to pipeline pressure levels in two stages rather than six, and a machine with fewer moving parts than traditional compressors. Those machines can reuse heat produced, improving efficiency.
"The problem with CCS," Hume said, "is parasitic loss: the whole idea of using fossil fuel ... to generate electricity and then using a good chunk of that electricity to pay for CCS. We're trying to get that parasitic penalty down as much as possible."
Ramgen's work is funded by a $20 million DOE grant from the stimulus law, along with a $25 million investment by equipment manufacturer Dresser-Rand. The technology will be tested next year in a demonstration-scale project at Dresser-Rand's plant in New York. Ramgen has already tested smaller versions at a Boeing facility in Washington state.
Ramgen began as a startup 10 years ago with a goal of developing an electricity-generating engine. DOE caught wind of the project and three years ago suggested that the company try using the technology to compress CO2 instead.
"It had never occurred to us, so it was sort of totally out of the blue," Hume said.
Working with DOE experts and with previous federal grants, Ramgen successfully developed the concept and has been scaling it up ever since.
The company has temporarily put on hold development of the original engine technology, but Hume said the company's flagship engine proposal is far from dead.
"The engine is still very much on our radar screen," Hume said. "Completing the compressor for CO2 will also improve the technology for ... the engine. So any accomplishment with CO2 will be a huge advancement for the engine, as well."