Thermal Assessment of Evacuated and Flat Plate Collector Solar Water Heater for the Enhancement of Collector Area

Over the past decade, India has witnessed a sig- nificant increase in the share of renewable energy sources in its energy mix, rising from 13.2% in 2010 to 24.8% in 2020, driven by governmental policies like the National Solar Mission and the Renewable Purchase Obligation (RPO). This growth has been further fueled by diminishing fossil fuel reserves, rising fuel prices, and global emissions regulations. Consequently, there has been a notable surge in the adoption of solar evacuated tube collector-based domestic water heating systems, with installations in India escalating from 1.8 million square meters in 2015 to 3.2 million square meters in 2020, reflecting increased awareness and the tangible benefits of renewable energy technologies. However, challenges persist, especially in densely populated urban areas with limited installation space due to rapid urbanization. To address this, the study proposes reducing the collector area by varying evacuated tube diameters. Comparative analysis between evacuated tube collectors and flat plate solar water heaters aims to introduce a dual absorber solar water heater capable of harnessing direct and diffused solar radiation, en- hancing hot water generation and system efficiency. Findings suggest that 48mm diameter and 1800mm length tubes are optimal for evacuated tube models, while a 4m2 collector area proves excessive for a 150-litre solar water heater. Theoretical validation using MATLAB aligns with experimental results. A dual absorber-based solar water heater is proposed, potentially reducing collector area by approximately 30%. Further research is recommended to refine the capacity and efficiency of this proposed model.