A team of researchers from the National Renewable Energy Laboratory (NREL) and Acciona Solar Power claimed that they had developed a technology that can enhance the efficiency and revenue of concentrating solar power (CSP) projects.
The researchers explained that most common CSP projects are based on a parabolic trough design, in which heat absorbers tubes run in line with curved concentrating mirrors to absorb the Sun’s energy. The hydrogen buildup reduces CSP’s efficiency, and its mitigation process is also expensive.
In CSP facilities, the organic-based fluids deliver heat to power-generating steam turbines from the parabolic trough receivers. However, it goes through a small but continuous thermal breakdown during the operation, resulting in the hydrogen off-gassing that causes thermal loss, which decreases CSP facilities’ overall efficiency and revenue by around 15%. Eventually, this results in an energy capacity loss of about 750 MW and a revenue loss of approximately $250 million annually as over 80 CSP parabolic trough facilities are in operation worldwide.
The researchers developed a systematic mitigation process to control hydrogen in receivers to enhance CSP facilities’ efficiency and revenue. They built a computational method to regulate the hydrogen extraction rate to maintain acceptable hydrogen concentration in the circulating heat-transfer fluid.
Following that, they developed a hydrogen-sensor to measure gas concentration for every one to two minutes. They utilized a palladium membrane to separate and remove hydrogen from the expansion tank through vacuum pumps. They built a prototype by combining hydrogen sensors and extraction to be used as a CSP facility model.
“A full-scale integrated hydrogen sensor/separate module was designed and implemented at Acciona’s Nevada Solar One CSP facility. Ongoing evaluations indicate that it is successfully operating as designed. But the module goes well beyond preventing future efficiency loss in new receivers – it gradually cleans existing contaminated receivers by pulling the hydrogen back out of the glass sleeves and restore them to their original operating efficiency,” said the researchers.
CSP technology has not gained popularity as the photovoltaic globally due to higher costs. The most recent CSP project is being built in the Mohammed bin Rashid Al Maktoum Solar Park by the Dubai Electricity and Water Authority. This is the world’s largest investment project using concentrated solar power (CSP) on a single site. The project will use three technologies – 600MW from a parabolic basin complex, 100MW from a solar tower, and 250MW from solar PV panels.
Image credit: NREL