Recovery of liquefied natural gas cold energy in a clean cogeneration system utilizing concentrated photovoltaics

Natural gas must be liquefied for long distance transport, so a lot of energy is lost during the liquefaction and regasification process. The innovative system proposed in this study recovers the cold exergy of liquefied natural gas (LNG) regasification process and also uses this potential for concentrated photovoltaics (CPV) cooling. The system uses cascades of organic Rankine cycles (ORC) whose boilers' high-temperature sources are supplied by thermal management of the CPV and low-temperature sides are in thermal contact with LNG flow. In the proposed system, the ORC's organic working fluid cools the CPV heat sink directly to reduce exergy destructions. An analytical thermodynamic and heat transfer model is developed which focuses on the heat transfer within the CPV heat sinks. The proposed system is examined in the ambient conditions of the top five LNG importing countries in the world. The results indicate that the proposed approach can deliver up to 24 MW electrical power, which is improved up to 180% in comparison with using the seawater-driven ORCs. The system produces up to 223 kg/s of cooling water in 7 degrees C, and its exergetic efficiency is up to 31%. From the CPV cooling point of view, the proposed system in 1000 x solar radiation concentration can keep the CPV temperature below 87 degrees C. Among studied regions, the best annual average of 2nd law efficiency can be achieved in India, about 28.3%. Utilizing the proposed system in a 100 kg/s LNG regasification unit can result in 26-32 MW of annual average power production, depending on the region it is used.

Automated summary

The study proposes an innovative system that recovers the cold energy from the liquefied natural gas regasification process and uses it to cool concentrated photovoltaics. By using cascades of organic Rankine cycles, the system improves the electrical power output and energy efficiency.