Cheaper, cleaner power for your home could be on the near horizon. With the support of a U.S. Department of Energy (DOE) grant, a team of four institutions thinks that within three years they can bring energy efficiency to your house at one-eighth the cost.
The group's proposal to optimize combined heating and power (CHP) systems for residential housing earned $2.7 million in seed money in October from the DOE's Advanced Research Projects Agency-Energy (ARPA-E).
CHP systems use a waste-heat recovery system and one power source, such as a natural gas generator, to produce all of the heating, cooling and electrical power that a building needs. Commercial buildings use CHP to increase energy efficiency by avoiding the transmission and distribution losses that occur when electricity travels over power lines, and by capturing more of the energy output from natural gas through waste-heat recovery. Additionally, CHP systems remove the need to worry about power loss from grid outages or mandated rolling blackouts during peak use times.
Early in 2016, the DOE's Argonne National Laboratory, Colorado-based Air Squared, Inc., Mississippi State University and Purdue University launched efforts to develop the first residential CHP system that uses small generators.
Today's CHP systems operate on large 4 or 5 kilowatt-sized generators, requiring them to connect to the main utility grid system to offload excess power, and can cost $25,000 to $30,000.
Creating a system that can work with a smaller generator powered by natural gas would make mass production viable, reduce costs and eliminate the need to interface with the grid system.
In addition, the team says its novel home utility system will be more efficient and longer lasting than residential CHP systems on the market. Today's systems operate at about 26 percent efficiency, and ARPA-E has set a goal of increasing efficiency to 40 percent or more.
"It's going to be something totally new," said Munidhar Biruduganti, a principal research engineer at Argonne. "We want to shoot for an output of one kilowatt, not five kilowatts, so that all the power is used by the home."
The team will develop the new system in two parts, with efforts led by equipment manufacturer Air Squared, Inc.
Air Squared will partner with Purdue University to build an organic Rankine cycle system to capture waste heat and turn it into electricity. The generator is projected to cost one-third of existing systems through improvements in fluid mixture and the addition of a novel oil-free scroll expander.
"Using organic Rankine cycle technology to recover the waste heat of the engine exhaust will allow us to boost overall thermal efficiency by up to six percent, getting us closer to the 40 percent goal," said Eckhard A. Groll, Reilly Professor of Mechanical Engineering, Ray W. Herrick Laboratories, at Purdue University.
Groll added, "Organic Rankine cycle technology has been proven in larger applications, such as geothermal heat recovery. However, the challenge of the current project lies in the miniaturization of the technology for application in a one-kilowatt power output engine."
In tandem, researchers from Argonne and Mississippi State University will develop an advanced internal combustion engine to integrate with the organic Rankine cycle system. The engine will use spark-assisted compression ignition, a turbulent jet ignition fueling system, high compression ratio and aggressive exhaust gas recirculation to deliver a higher thermal efficiency with low emissions. Argonne brings to the project expertise working with a variety of natural gas stationary power generation systems to reduce emissions.
Mississippi State University researchers Professors Sundar Krishnan and Kalyan Srinivasan will develop high-fidelity system-level simulations and lead the design effort to achieve a high-efficiency, one-kilowatt spark-assisted compression ignition natural gas generator.
The two components will be coupled in the second year of the three-year project and undergo system-wide testing at Argonne. In the final year, Air Squared will put the new system through durability testing.
The award is one of three given out as part of the Generators for Small Electrical and Thermal Systems' Small Business Innovation Research (SBIR) and Small Business Technology Transfer (STTR) initiatives funded by ARPA-E.