A potential solution in reducing the parabolic trough based solar industrial process heat system cost by partially replacing absorbers coatings with non-selective ones in initial loop sections

An important step to achieve low-emission production is the integration of solar energy into industrial processes for decarbonizing the industrial sector. It is therefore necessary to attempt to minimize the cost of these solar industrial process heat systems. The article presents a strategy to reduce the investment costs and thus increase the popularity of parabolic trough collectors by partially replacing the expensive selective coating with a high absorptive, low-cost, non-selective coating in the initial sections of the solar loop where the heat transfer fluid temperature is lower. The analysis was performed for 4 case studies reflecting commercially available solutions with varying temperature ranges for different industrial applications. Calculations were performed using the two-dimensional developed mathematical model that validated with experimental data. The assumed heat transfer fluid is Therminol VP-1. The results have shown the potential of partial use of the Pyromark coating for low and medium-temperature industrial process heat systems with inlet–outlet temperature ranges of 60–120 °C and 100–200 °C. The analysis also showed that all the absorbers can be covered with a low-cost coating in the first scenario. Efficiency increases from 1.5 to 5.5 percentage points have been observed. For the second scenario, 15 of the 24 absorbers can be covered with a low-cost coating, when the installation works at a solar irradiance of 800 W/m2. Since the results are depended on the solar irradiance and the chosen regulation strategy of the flow, the final number of absorbers possible to cover with non-selective coating requires a long-term analysis for each case examined.