PNNL solar thermochemical reaction system can reduce fuel consumption in natural gas power plants by about 20%; future potential for transportation fuels
|PNNL’s thermochemical conversion device is installed in front of a concentrating solar power dish. Photo: PNNL. Click to enlarge.|
A new concentrating solar power system developed by Pacific Northwest National Laboratory (PNNL) can reduce the fuel consumption of a modified natural-gas combined-cycle (NGCC) power plant by about 20%. The system converts natural gas into syngas—with higher energy content than natural gas—using a thermochemical conversion device installed in front of a concentrating solar power dish. The power plant then combusts the more energy dense syngas to produce electricity.
PNNL’s system uses a mirrored parabolic dish to direct sunbeams to a central point, where the thermochemical device uses the solar heat to produce syngas form natural gas. About four feet long and two feet wide, the device contains a chemical reactor and several heat exchangers. Concentrated sunlight heats up the natural gas flowing through the reactor’s channels, which hold a catalyst that helps turn natural gas into syngas.
|The full CSP system. Photo: PNNL. Click to enlarge.|
The heat exchanger features microchannels that are a couple times thicker than a strand of human hair. The exchanger’s channels help recycle heat left over from the chemical reaction gas. By reusing the heat, solar energy is used more efficiently to convert natural gas into syngas. Tests on an earlier prototype of the device showed more than 60% of the solar energy that hit the system’s mirrored dish was converted into chemical energy contained in the syngas.
PNNL is refining the earlier prototype to increase its efficiency while creating a design that can be made at a reasonable price. The project includes developing cost-effective manufacturing techniques that could be used for the mass production. The manufacturing methods will be developed by PNNL staff at the Microproducts Breakthrough Institute, a research and development facility in Corvallis, Ore., that is jointly managed by PNNL and Oregon State University.
Our system will enable power plants to use less natural gas to produce the same amount of electricity they already make. At the same time, the system lowers a power plant’s greenhouse gas emissions at a cost that’s competitive with traditional fossil fuel power.—PNNL engineer Bob Wegeng, project leader
PNNL will conduct field tests of the system at its campus in Richland, Wash., this summer.
|The US Energy Information Administration estimates natural gas will make up 27% of the nation’s electricity by 2020.|
Wegeng noted PNNL’s system is best suited for power plants located in sunshine-drenched areas such as the American Southwest.
Wegeng’s team aims to keep the system’s overall cost low enough so that the electricity produced by a natural gas power plant equipped with the system would cost no more than 6 cents per kilowatt-hour by 2020. Such a price tag would make hybrid solar-gas power plants competitive with conventional, fossil fuel-burning power plants while also reducing greenhouse gas emissions.
The system is adaptable to a large range of natural gas power plant sizes. The number of PNNL devices needed depends on a particular power plant’s size. For example, a 500 MW plant would need roughly 3,000 dishes equipped with PNNL’s device.
PNNL’s system doesn’t require power plants to cease operations when the sun sets or clouds cover the sky. Power plants can bypass the system and burn natural gas directly.
Though outside the scope of the current project, Wegeng also envisions a day when PNNL’s solar-driven system could be used to create transportation fuels. Syngas can also be used to make synthetic crude oil, which can be refined into diesel and gasoline.
The current project is receiving about $4.3 million combined from DOE’s SunShot Initiative, which aims to advance American-made solar technologies, and industrial partner SolarThermoChemical LLC of Santa Maria, Calif.
SolarThermoChemical has a Cooperative Research and Development Agreement for the project and plans to manufacture and sell the system after the project ends.
RS Wegeng, DR Palo, RA Dagle, PH Humble, JA Lizarazo-Adarme, SK, SD Leith, CJ Pestak, S Qiu, B Boler, J Modrell, G McFadden, “Development and Demonstration of a Prototype Solar Methane Reforming System for Thermochemical Energy Storage — Including Preliminary Shakedown Testing Results,” 9th Annual International Energy Conversion Engineering Conference, July-August 2011