Life cycle and environmental impact assessment of heat transfer fluids in parabolic trough CSP plants

Environmental impact, energy efficiency and cost optimization are basic aspects when selecting heat transfer fluids (HTF) for CSP plants. The present study evaluates the environmental impact of four CSP HTF types (Thermal Oil, Liquid Metal, Molten Salt and Silicone-based), by analyzing different traditional and innovative fluids, such as Therminol VP-1 (R), Liquid Sodium, Lead-bismuth eutectic, Solar Salt, Hitec (R), Hitec XL (R) and Helisol (R) 5A. All fluids underwent a life cycle analysis with the ReCiPe 2016 method, using the Ecoinvent 3.8 database, the SimaPro 9.3 software and the "cradle-to-grave" perspective to detail their impacts on Human Health, Ecosystem Quality, and Resource Availability. For the hypothesized scenario, results show how Hitec XL (R) presented the lowest cost and environmental impact values (1.19 US$/kg and 104.99 mPt/kg), being up to 3.6 times more sustainable. Therminol VP-1 (R) obtained the highest environmental impact score, being up to 88.5% more unfavourable than Hitec XL (R) and 73.4% than the rest of fluids. The area with the highest impact was Human health (92.54%), with a significant influence of the Fine Particulate Matter formation category (40%). The knowledge developed will provide a detailed insight into the environmental impact in CSP plants, complementing current performance data and contributing to the energy sector's decarbonization.