Design and analysis of a medium-temperature, concentrated solar thermal collector for air-conditioning applications

- A rooftop-based concentrating collector coupled with an absorption chiller was analyzed.
- A novel semi-passive tracking method was proposed for high annual optical efficiency.
- The optimal sizes of the solar assisted air-conditioning plants were obtained.
- Economic analysis indicated an achievable LCOC price of 0.60 $/kW-h.

Solar thermal energy is considered as a promising source to drive air-conditioning applications due to the good correlation between supply and demand. The present work examines the feasibility of a novel, low-profile concentrated solar thermal collector to provide medium-temperature heat to commercial buildings for both heating and cooling purposes, aiming to reduce their non-renewable energy consumption levels. To the best of the authors' knowledge, the semi-passive tracking/concentrating platform employed in this collector represents a significant improvement for 'stationary' (internal tracking, the module itself remains fixed) solar concentrating technology. To investigate the real-world viability of this collector design for solar heating and cooling, a system-level techno-economic performance analysis is conducted using a validated TRNSYS model. The solar heating and cooling (SHC) system includes the proposed solar thermal collectors, an auxiliary heater, and a double-effect absorption chiller. In this study, the proposed solar collectors are employed to supply thermal energy to the chiller to offset the building cooling demand or the thermal energy can also be used directly to satisfy the building's heating demand. When sufficient solar energy is not available, the auxiliary heater provides the rest of the heating and cooling demand. The annual solar fraction and economic metrics (e.g. total levelized costs) were used as the selection criteria among design options. The simulation results demonstrate that a specific collector area of 2.4 m2 per kW cooling and an optimal storage tank specific volume of 40 L/m2 are sufficient to cover 50% of the load requirement of the building. The economic analysis indicates that a levelized cost of cooling energy (LCOC) of ∼0.6 $/kW-h can be derived from this solar air-conditioning system.