A stand-alone micro heat pump for personalized environmental control system (PECS)

This experimental study presents the design, development, and testing of a micro-scale vapor compression (VC) heat pump prototype tailored for novel Personalized Environmental Comfort Systems (PECS). The system employs a natural refrigerant (HC-290) to align with new environmental regulations, and integrates both compressor speed and expansion valve modulation, enabling continuous and precise control of cooling power and temperature – features rarely found in miniaturized systems. A key innovation is the integration of a 20-liter heat thermal energy storage unit (either sensible or latent) to buffer condensation heat and support standalone operation up to 8 h, without outdoor ducting or heat rejection. Experimental results show that localized cooling at approximately 20 °C can be maintained even in ambient conditions up to 36 °C, with an average Energy Efficiency Ratio (EER) of around 2 when using a latent heat thermal storage system based on phase change materials. The optimized configuration delivers a stable cooling output of ∼200 W, sufficient to meet the thermal needs of a single occupant while minimizing the impact on indoor air conditions. By reducing the volume of conditioned space and enabling direct user-level control, the proposed system supports a shift toward decentralized comfort solutions, with the potential to relax central HVAC setpoints and reduce overall building energy consumption. The study also provides a comprehensive experimental characterization.