Researchers from India’s National Institute of Technology (NIT) Kurukshetra and the National Institute of Solar Energy (NISE) Gurugram have developed a PV-driven prototype solar geyser system that uses a fine sand thermal storage medium for domestic hot water.
The Fine Sand Solar Geyser (FSG) reportedly achieves an energy cost of just $0.0233 per kWh, according to its creators.
It uses electricity generated from PV panels to power a nichrome wire heating rod, which converts the electrical energy into heat. This heat is stored in 120 kg of fine sand, chosen for its high thermal mass, excellent heat retention, uniform heat distribution, low cost, and abundant availability.
“The FSG system offers a sustainable, environmentally friendly, and cost-effective solution for water heating by storing thermal energy in fine sand, overcoming the intermittency of solar radiation,” researcher Dinesh Kumar Saini told PV Magazine.
The system comprises three 300 W polycrystalline solar panels, a nichrome wire heating rod, and a circular heat exchanger. During system operation, the nichrome wire converts PV-generated electricity into thermal energy, which is stored in the fine sand. A heat exchanger with aluminum fins then transfers the stored heat to water as it passes through embedded pipes.
The performance analysis of the system showed the sand temperature inside the FSG increased from 25.2 C to 164.2 C on the first day of operation and from 94.7 C to 211.9 C on the second day. The system stored 14.39 MJ and 13.02 MJ of heat on these respective days, achieving thermal storage efficiencies of 97.41% and 90.76%, respectively.
Co-author Chandrashekara Muniyappa further explained that the system delivered 140 liters and 152 liters of hot water over two days at a flow rate of 0.67 liters per minute. The average water temperature difference between the FSG inlet and outlet was recorded as 11.7 C and 13.75 C on these days. The system demonstrated a discharging efficiency of approximately 90% on both days.
Further techno-economic analysis indicated the system is economically viable for domestic water heating applications, with an initial capital cost of $278 and an expected lifespan of 25 years. The system offers a cost of energy is $0.0233 per kWh, with a projected payback period of 4.45 years.
The group described the system in the study “Thermal performance analysis of a fine sand solar geyser integrated with photovoltaic technology,” which was recently published in Energy Sources.
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