Engineering news
The University of Nottingham is developing a solar air-conditioning system that cuts electricity consumption by up to 50% compared to the conventional vapour compression (VC) system.
The university said the system could have ‘major savings for the environment and people’s pockets’, particularly as air-conditioning accounts for a significant portion of total energy use around the world.
Dr Jie Zhu, from the Department of Architecture and Built Environment at The University of Nottingham and Professor Tingxian Li, Shanghai Jiaotong University, China – supported by the Royal Society – are working together to investigate the new air-conditioning technology. It combines temperature and humidity independent control (THIC), powered by solar energy, and a sorption thermal battery that combines heat and cold energy storage in one unit.
Dr Zhu said: “A VC cooling system adopts a condensation dehumidification method to handle both sensible and latent heat loads. This means the system has to operate under lower evaporation temperatures, which results in lower cooling capacity, lower coefficient of performance (COP) and sometimes a reheating process is required to meet supply air requirements.
“We are proposing a temperature and humidity independent control technology to solve this problem. This system can save 25-50% electrical consumption and COP increases about 40-60%, thus greatly reducing operating costs, compared to the conventional VC system.”
The solid-gas sorption thermal battery has the ability to store both heat and cold energy at a controllable temperature in one unit. The heat energy is used to power the dehumidification sub-system, while the cold energy is used to cool the air that needs to circulate in indoor environments.
The proposed system consists of two units: heat-powered membrane liquid-drying dehumidification and solar sorption thermal battery units. Two sorption thermal battery units are used to assure the system continuously operates.
To remove moisture and latent heat from the incoming supply air stream, the air-conditioning system uses a liquid desiccant material which attracts and holds water vapour.
During the regeneration process in the dehumidification unit, the desiccant solution is heated by the sorption heat of the battery and then flows into the regeneration cabin where the warmed desiccant solution will remove moisture from the working air.
Afterwards, as the air reaches a water-air cooler, it is cooled by chilled water produced by the evaporation heat of refrigerant from the sorption thermal battery. This cyclical process ultimately generates the dry and cooled supply air which is released into a room.
The proposed research is investigating new composite sorbents, thermal energy storage capacity, heat and mass transfer properties and will assess economic and environmental impacts using theoretical and experimental measures.
A small scale prototype system will be designed, constructed and tested.
It is expected that the system could eventually be of huge value to industries including Heating, Ventilation, and Air-Conditioning (HVAC), building services, environmental engineering and component manufacture.
“Solar air-conditioning is one of the promising technologies to alleviate the huge demand for energy resources. It has the potential to provide a viable alternative to conventional air-conditioning systems,” said Dr Zhu.