Assume we want to develop a promising solar-assisted absorption heat pump system for sustainable heating of large-scale indoor swimming pools, we could consider integrating photovoltaic/thermal (PV/T) collectors, absorption and ground-source heat pumps (GSHP), and an underground thermal energy storage (UTES) system, strategically designed to enhance renewable energy utilization and reduce grid dependency.
The rationale behind this integrated system is rooted in harnessing solar energy efficiently, capturing electrical and thermal outputs simultaneously through PV/T collectors. These collectors convert solar irradiance into usable electricity and thermal energy, addressing two crucial demands: driving the electrically powered GSHP and fueling the thermally driven absorption heat pump. Solar energy featuresan intermittent supply, so a thermal energy storage system is needed to use the extra heat stored in summer for heating in winter. Therefore, we use the UTES system as a thermal energy storage reservoir to store the excess heat in summer for further usage in winter to balance the intermittent energy supply of solar energy with the stable demand supply in the year-round operation.
Performance metrics are presented vaguely to protect sensitive engineering data while communicating the system’s functionality. The PV/T collectors exhibit distinct average efficiencies—electrical output shows annual degradation at approximately 2-5% due to material aging, significantly affecting long-term performance. Thermal efficiency remains relatively robust, though it requires optimization to meet higher thermal demands. Critical outputs, including annual electrical and thermal energy, are expressed in the general analytical form to underscore the system’s scalability.
Absorption heat pumps offer a noteworthy benefit: the ability to utilize low-grade thermal energy with modest efficiency (COP_abs, eff ~ below 1). In contrast, GSHPs feature significantly higher efficiency (COP_GSHP, eff ~ 4~5), effectively multiplying electrical energy input from the PV/T system. This strategic integration amplifies renewable energy utilization but highlights the importance of managing performance degradation in PV/T panels over the long term.
The system faces several critical limitations. It is worth noting that this PV/T collector combined with an absorption heat pump system only meets a small portion (less than 10%) of the total annual swimming pool heating demand, which shows the significant challenges in scaling up innovative renewable thermal systems for extensive infrastructure (such as commercial swimming pools). Other challenges include PV/T system aging, UTES thermal storage efficiency loss (about 10%), and system integration complexity. Addressing these requires innovations in materials science, system design simplicity, and operational efficiency.
Future developments promise significant improvements in system performance. Emerging technologies in PV/T collectors—particularly perovskite-based PV/T systems—show potential for much higher electrical efficiency (exceeding 25%), dramatically enhancing overall energy yields. Concentrated photovoltaic/thermal (CPV/T) collectors could also substantially improve thermal output, making absorption heat pumps more viable. In addition, the coating on the surface of the PV/T thermal collector has a self-cleaning function, which is expected to reduce the rate of system degradation over time and extend the system’s life and operating efficiency.
Absorption heat pump technology itself is undergoing transformative advancements. The multi-effect absorption system is expected to double the efficiency of the current absorption heat pump system and significantly improve the thermal energy conversion rate of the solar energy input absorption heat pump system. Designs that use new refrigerants, such as ionic liquids and natural refrigerants, can reduce the system’s initial investment and construction and long-term system maintenance costs. More importantly, new refrigerants can also minimize the impact of regenerative thermal energy systems on global warming gas emissions. Integrated systems combining absorption and compression heat pumps are also being explored, which can provide dynamic adjustments based on instant solar energy availability and fluctuations in demand at the user end.
UTES technology similarly benefits from ongoing research into phase-change materials (PCMs) and borehole thermal energy storage (BTES). These alternatives can potentially increase thermal energy storage density and efficiency, reduce building space footprint, and improve system operating efficiency (>95%), which is critical for deploying this emerging PV/T combined with absorption heat pumps in urban infrastructure.
From the perspective of energy markets and policy implementation, increasing global renewable energy incentives, such as renewable heat integration subsidies and carbon pricing mechanisms, can further improve the economic feasibility and energy market competitiveness of solar-assisted absorption heat pump systems. With the strict implementation and promotion of net-zero emission targets, this integrated technology has a promising prospect in urban infrastructure applications such as commercial swimming pools.
By 2030, advancements could see PV/T electrical efficiencies increase 10~15%, thermal efficiencies rising at least 15~20%, and absorption heat pump COPs potentially double. These developments could more than double the heat demand coverage for comparable facilities, significantly lowering the levelized cost of heat (LCOH) by ~20%, making renewable heating solutions increasingly attractive.
In summary, although current regenerative thermal energy systems such as PV/T combined with absorption heat pump systems pose considerable challenges in terms of global coverage and the complexity of system construction and system operation (energy market competition and energy market policy implementation direction), continuous technological innovation in regenerative thermal energy systems and the evolution of government supportive policies for regenerative thermal energy will lead to breakthroughs in the economic feasibility of PV/T combined with absorption heat pump systems in the future. Integrated solar-assisted absorption heat pump systems are an essential system design option for more widespread and efficient regenerative thermal energy systems, consistent with the direction toward broader global sustainability and energy efficiency.