energy.agwired.com

The U.S. Department of Energy (DOE) has awarded Southwest Research Institute (SwRI) $4.9 million as part of a $9.9 million continuation contract to manufacture and test a high-efficiency supercritical CO2 (sCO2) hot gas turbo-expander and compact heat exchangers for concentrating solar power (CSP) plants. Dr. Klaus Brun, program director of the Machinery Program in SwRI’s Mechanical Engineering Division says this project is one of eight DOE-funded sCO2 power cycle projects currently in progress.

The award was given through DOE’s SunShot Initiative and continues a previous DOE project to design the sCO2 expander. SwRI will lead a team of industry collaborators that includes Aramco Services Company, Bechtel Marine Propulsion Corporation, Electric Power Research Institute (EPRI), General Electric, and Thar Energy.

According to SwRI the highly cyclical nature of CSP plant operation requires an sCO2 hot gas turbo-expander to operate at high temperatures and pressures over a wide range of load conditions while maintaining high efficiency, handling rapid transient heat input swings, and offering very fast start-up to optimize the plant’s online availability. Similar sCO2 expanders also have the potential to significantly improve the efficiency of waste heat recovery, nuclear and fossil-fueled power plants.

“Over the last two years, SwRI and its industry collaborators have developed a highly efficient, multi-stage axial flow sCO2 hot gas turbo-expander that advances the state of the art from laboratory size to a full mega-watt scale prototype,” says Dr. Jeff Moore, manager of the Rotating Machinery Dynamics Section in SwRI’s Mechanical Engineering Division, and principal investigator of the project.

A second objective of the project, according to SwRI, is to optimize novel compact heat exchangers for sCO2 applications to drastically reduce manufacturing costs. The scalable sCO2 expander design and improved heat exchanger will close two critical technology gaps and potentially provide a major pathway to achieve power at $0.06 per kilowatt hour, increasing energy conversion efficiency to more than 50 percent, and potentially reducing total power block cost to below $1,200 per kilowatt installed. Conventional steam-based CSP systems typically operate at less than 35 percent efficiency. These efficiencies also will allow solar plants to be competitive with conventional fossil-fueled power plants.

The Louisiana Public Service Commission has released a draft report that the Partnership for Affordable Clean Energy (PACE) says sheds “significant light” on the inequities caused by the state’s treatment of distributed solar generation. The report finds that the state’s current public subsidy for solar power is unsustainable but also that the net metering requirement for utilities is shifting considerable grid costs from solar customers to non-solar customers.

PACE is calling this “unfair” and wants the state to change its treatment of distributed solar. They cite several important conclusions found in the report:

• More than $2 million in grid costs are being shifted to non-solar customers in Louisiana. This could grow to $31.4 million by 2020.
• Costs associated with net metering in Louisiana far outweigh the benefits. The negative cost is already $89 million and is estimated to rise to between $125 million and $488 million.
• Net metering customers have incomes on average 35% higher than non-solar customers, meaning the state’s net metering policy is shifting grid costs from those with more money to those with less.
• Louisiana’s net metering policy could cause power customers to pay as much as $809 million more if it is left unchanged.
• Louisiana’s taxpayer subsidy to solar customers has grown from an originally estimated half a million dollars annually to $42 million per year, making it one of the most generous in the nation.

In Louisiana, as in many other states, regulatory policy allows a small group of customers to use the power grid as a battery backup when they are unable to rely on their solar rooftop systems. However, PACE notes that these customers are unwilling to help pay for the cost of maintaining a reliable electricity grid in Louisiana. While solar is a valuable resource, says PACE, everyone should pay their fair share for the use of the power grid. Right now, as the report clearly shows, those costs are being shifted to less affluent non-solar customers, which is both unfair and unsustainable.

How to incorporate solar energy in way that is fair and benefits all electricity consumers is becoming a hot button issue around the country. For example, Arizona and New Mexico, fees for solar users have been viewed as solutions to this issue while Hawaii has recently lowered net metering rates. PACE is calling on Louisiana to review other states’ policies as a guide to create fairness.