ANALYSIS OF SOLAR-ASSISTED HEAT PUMP SYSTEM FOR INDOOR SWIMMING POOL HEATING: A CASE STUDY FOR AN-NAJAH UNIVERSITY SWIMMING POOL

Abstract

This study evaluates retrofit heating configurations for an indoor swimming pool in Palestine, utilizing the An-Najah National University indoor pool in Nablus as a case study. The study evaluates the energy efficiency and economic feasibility of possible solutions while keeping the temperature of the pool to be 28°C during its operational time and to determine the most suitable option under local energy prices. The existing reference system is evacuated tube solar thermal collectors integrated with a diesel boiler that is used for heating the swimming pool, with a control logic that may bypass the solar loop under certain conditions and it was modeled first. Retrofit options were then developed and simulated in Polysun Simulation Software, using an hourly resolution for a full year using TMY2 weather data for the city of Nablus. The evaluated options include: (i) diesel boiler replacement with an air source heat pump without using solar collectors (ii) a solar-assisted heat pump (SAHP) in parallel where the solar thermal field and an ASHP supply heat in parallel, (iii) a SAHP in series which include water source heat pump that connected in series with solar thermal collector and supported by air source heat pump to ensure reliable heating, (iv) replacement of diesel boiler with Liquified Petrol Gas boiler in addition to the solar thermal collector heating system source (v): using solar thermal collectors in addition to heat pump with auxiliary diesel boiler, and (vi) using solar thermal collectors in addition to heat pump with auxiliary LPG boiler. The simulation outputs (useful heat, solar contribution, electricity and fuel consumption, and seasonal performance) were integrated into an economic assessment using different indicators like payback period, present worth, rate of return, benefit-to-cost, and Levelized cost of heat. Also, an environmental assessment was conducted for the different evaluated options. The results show that the SAHP system significantly reduces total energy consumption to approximately 147,643 kWh/year, compared to 452,865 kWh/year for the conventional system. The solar collectors contributed around 40% of the total heating demand, leading to a noticeable reduction in heat pump electricity consumption. Economically, the system achieved levelized cost of heat (LCOH) of 0.074 $/kWhth. Which is very good compared to other alternatives and to the existing conventional system that has LCOH higher than 0.22$/kWhth, and the estimated payback period is 1.89 years. In terms of environmental impact, the SAHP system reduced CO2 emissions to approximately 62,010 kgCO₂e/year, compared to 120,915 kgCO₂e/year for the diesel-based system, representing a reduction of about 49%. In conclusion, the solar-assisted heat pump system proves to be an efficient and sustainable solution for swimming pool heating in Palestine, offering significant energy savings, economic benefits, and considerable reductions in greenhouse gas emissions.