Techno-economic assessment of evacuated flat-plate solar collector system for industrial process heat

Abstract

In the industrial sector, hot water applications constitute a significant share of final energy consumption. This creates a wide demand-supply energy gap that must be bridged by integrating renewable sources with conventional fuels. This paper presents the performance analysis of a solar water heating system based on an evacuated flat-plate collector (EFPC) with a surface area of 4 m2. A water-glycol mixture was used as the heat transfer fluid (HTF) with mass flow rates of 0.03, 0.0336, and 0.0504 kg/s under a vacuum pressure of -0.8 bar created inside the collector. A detailed numerical model was developed in MATLAB for the proposed EFPC system, followed by experimental validation. A maximum root mean square error of 2.81 for the absorber temperature and a percentage error of 6.62 was observed for the thermal efficiency in model validation. This substantiates the model's capability to predict actual system performance with reasonable accuracy. The maximum thermal efficiency of the EFPC is 78% with a maximum fluid outlet temperature of 98°C in June and 69°C in January. The maximum useful energy extracted is 1300 W in January. Additionally, the effect of design parameters on system performance such as mass flow rates, collector areas, tube spacing, and different HTF mixtures is simulated. Lastly, an economic analysis of the EFPC was conducted for hot water demand in a textile industry. The results revealed a payback period of 7.4 years, which highlights the feasibility of this system.