Model development of deep space-source heat pump system and its feasibility analysis

This study proposes a novel deep space-source heat pump (DSSHP) system for efficient heat rejection, considering the spectral selectivity of cooling coatings and atmospheric windows, the influence of tilt angles and cloud cover fractions. Then, the long-term operation performances of the DSSHP are investigated under various working conditions. The results indicate that the optimal DSSHP operation conditions include a lower flow rate, horizontal installation of environment-side water-to-air radiators, and clear sky. The proposed system shows better economic and cooling-efficiency advantages. Compared with air-source heat pump (HP) and ground-source HP, the DSSHP payback period is only 5.1 years, and its cooling season average COP is comparable to ground-source HP (at 5.3). Moreover, this cooling system also shows high geographical adaptability for actual applications. The COP of the system in the highland city (Lhasa) can reach 6.7 on the cooling season average. Even in a tropical city (Hong Kong), the COP can still reach 5.3. Besides, this cooling system exhibits high spectral adaptability of cooling coatings on environment-side water-to-air radiators. The COP of a practical system with the actual coating is only maximally 8.0% smaller than that of the ideal system. Under the current worst energy crisis, this study can provide a novel application way of cooling coatings and a new cooling source for HP systems, with advantages of water saving, energy saving, and high energy efficiency.