On December 5-7 the 5th International Conference on Refrigeration Technology (ICRT) collected over 300 attendees, academia as well as industry representatives, from 11 different countries in Zhuhai in the South of China. During the first day several interesting keynote speeches were given, many of them with the increasing cooling demand in emerging countries or the severe air pollution problems in several large cities as the main theme. The problems and challenges were described and possible solutions were presented and discussed.
Energy demand for cooling will overtake the demand for space heating
Several factors such as the global warming, the urbanization, the increasing population in countries with access to comfort cooling, all contributes to that the worldwide energy demand for cooling and will overtake the space heating demand in 2060 if measures not are with taken from now on.
The demand for comfort cooling has already, and will increase even more, especially in countries like China, India, the ASEAN countries, but also in Europe. In addition, the worldwide refrigerated vehicle fleet could grow from around 4 million to as much as 18 million by 2025.
According to one of the keynote speakers Yi Jiang , Academician of Chinese Academy of Engineering, Tsinghua University, much of the increasing cooling demand will appear in households. To avoid extensive increase in energy demand for cooling, the challenge should be met by first reducing the demand for conventional cooling while meeting thermal comfort and thereafter increasing cooling efficiency and decreasing leakage from the equipment.
Some key features for cooling in civil buildings that should be applied to reduce the energy demand for cooling are:
- Part time, part space cooling rather than full-time and full space – behavior might make a difference of a factor of 10 and it has been seen that countries with similar climate condition can have huge difference in cooling energy intensity due to difference in use of cooling. (US compared to China for example, where the energy intensity for cooling is much higher in US)
- Natural ventilation should be used as much as possible. This is not possible everywhere, but in many places, at least part of the day or year. The buildings should be designed with openable windows and external shading if possible and sufficiently insulated to keep the coolness during the hot part of the day.
- A suitable indoor temperature setpoint should be applied and over cooling should be avoided.
- The cooling equipment and system should be designed in accordance with the practical use behaviors to encourage the occupants saving behaviors.
- The efficiency at part load operation should be increased, especially for VRF systems, which have often lower part load efficiency than split units. Household air-conditioning work at low part loads many hours of the year. One solution to achieve this is to apply double compressors, one small and one large
Innovative and alternative technologies to obtain resource efficient cooling are photovoltaic air conditioner, indirect evaporative cooling, desiccant with industry waste heat etc.
Techniques to enhance vapor compressions cycles
Professor Yunho Hwang from University of Maryland talked about several techniques to enhance the vapor compressions cycles, such as:
- Expansion losses reduction
- Multi-stage injections cycles
- Separate sensible and latent cooling
- Micro climate control – Roving Comforter
- Electrochemical compression
- Finless heat exchangers
The Roving Comfort mentioned above is a personal attendant for thermal comfort, which cools and heats through one or more robotically controlled air nozzles. The highly portable unit can follow a person and is equipped with integrated thermal storage.
Heat pumps as an air pollution control strategy
Professor Kirk Robert Smith, from University of California, Berkeley, talked about Heat pumps as an air pollution control strategy. Space heating is a major contributor to outdoor air pollution in Northern China, but also in countries like Mongolia and Nepal. Air pollution is a major contributor to deaths. If China were to introduce clean fuels or electricity for household space heating and cooling around the whole country, some 400 thousand lives a year could be saved compared to current policy. One good example of new policy to control the air pollution in the Beijing-Tianjian-Hebei regions is subsidies to install air-to-water heat pumps for space and hot water heating.
China has transformed from a poor country in the 80s to one of the world’s strongest economies. Now there are many people in the middle class and they often have AC and household machines, but still use coal for space heating. By applying heat pumps and inductive stoves, Chinese households can leapfrog into the 21th century – they can be clean, efficient and integrated!
Professor Kirk Robert Smith also reported about a pilot study where seven advanced air-to-air heat pumps had been installed in households in Ulan Bator. The electric company had to rewire the households to achieve sufficiently high capacity before installations of the heat pumps. The heat pumps were on-line real time monitored for one year. They worked as intended down to -40°C and indoor temperature was kept, no matter what the outdoor temp was.
Energy-Saving of Air-conditioning and heat pump heating
Another of the keynote speakers, Hua Lin, Vice director of the State key Laboratory of Air-conditioning Equipment and System Energy Conservation, gave a presentation about an Application study of the Big Data in Energy-Saving of Air-conditioning and heat pump heating. In one study optimized control strategy for heat pumps had been elaborated by Big Data handling. Defrosting needs are different in different areas in China due to different air humidity and temperature. In addition, haze effects the defrosting need, the heat pumps need to defrost more often and longer when haze. By monitoring and treating the data the optimized compressor frequency under different relative humidity to maximize capacity could be found and established.
International refrigeration technology standards and regulations
One session was about international refrigeration technology standards and regulations, and experiences from different parts of the world were exchanged. For example, Andrea Voigt from European Partnership for Energy and Environment (EPEE) shared experiences from the implementation of the European F-gas regulation and the main European trends. She also compared the phase downs steps of HFCs with the ones of the Kigali agreement, showing that the phase down of F-gas regulation is much steeper than Kigali, but will end at the same level.
The European Ecodesign and Energy Label regulations and standards
Caroline Haglund Stignor, from Heat Pumps Centre and RISE, gave a presentation about the European Ecodesign and Energy Label regulations and standard. Caroline explained the effect those regulations have had on the technology development for air-to-water heat pumps in Europe, for example the large introduction and dominance of variable control air-source heat pumps on the European market.
Caroline Haglund Stignor also gave a presentation about the IEA Technology Collaboration Programme on Heat Pumping Technologies (HPT TCP), since China is in the very last steps in the process of becoming a member of the HPT TCP. The presentation gained a lot of interest and it was clear that many of the attendees looked forward to future collaboration within the TCP. Considering the ongoing activities in China in the field of heat pumping technologies for both heating and cooling, the possibilities for a fruitful collaboration looks good.
The organizers of the conference were National Engineering Research Center of Green Refrigeration Equipment (ERCGRE) and State Key Laboratory of Air-Conditioning Equipment and System Energy Conservation (SKL) in China.