Novel Integrated Organic Rankine Cycle for Recovery of Low-Grade Waste Heat from Air-Conditioning Systems for Electricity Production

Project: Research

View graph of relations



The International Energy Agency (IEA) has identified Energy Efficiency as the most effective strategy to reduce greenhouse gas emission. In Hong Kong, the Government has set an aggressive target to reduce our energy intensity by 40% by 2025 in the Energy Saving Plan. As air-conditioning (AC) is the largest electricity consumer, AC has the highest potential to save substantial energy for achieving the energy intensity reduction target. AC waste heat recovery is a promising approach. We previously successfully completed an ITF project on integrated heat pump for recovery of AC waste heat for hot water production. Since our hot water demand is comparatively small, we still reject the remaining waste heat without production. Here we propose to develop integrated organic Rankine cycle air-conditioning (i-ORC-AC) systems to recover all the waste heat for electricity production. The main challenge is to boost ORC in recovery of low-grade heat (refrigerant condensing at 50-60 deg-C) with high economic viability. We have identified potential strategies, including superheating/desuperheating, evaporative cooling and coordinated heating/cooling. Our research will determine the best integrated system design and control. The target performance is to achieve high net COP equal to 10 or above; and payback period within 3 years.


Project number9440150
Grant typeITF
Effective start/end date1/06/1631/08/18