CO2 heat pumps save 37-50% electricity in railway stations in China&rsquo;s cold regions &nbsp;

Two demonstration projects of CO₂ heat pumps (HP) in Chinese railway stations in cold regions reveal that even under temperatures as low as -25°C, CO₂ HP reached higher coefficient of performance (COP) than conventional electric boilers and heaters. The CO₂-based systems achieved electricity savings of approximately 37-50% in the two cases as compared to conventional technologies, while providing additional functionalities such as space heating and air-condit

Comparison of CO₂ HP with conventional technology

Two case studies of CO₂ HP application in railway stations in cold regions of China demonstrate the suitability of CO₂ HP in low temperature conditions. CO₂ ECOLAND heat pumps from Tianjin Hi-Tech, which provide hot water, space heating and air conditioning, were installed in Dandong and Tongliao cities.

The results of a performance comparison between a conventional electrical boiler and heater and the CO₂ HP under similar conditions revealed that the CO₂ HP has reached:

• higher COP under -25°C

• energy savings of 49.67% and 36.3% in the two case studies respectively.

Railway station in Dandong City

A CO₂ HP system at the railway station in Dandong City was installed to replace an electric boiler providing hot water. In addition to providing hot water for daily use, the CO₂ HP provides space heating during the winter period.

Observation period: CO₂HP (8th of December 2012 – 18th of March 2013); electric boiler (15th of November 2011 - 15th of March 2012)
COP: CO₂ HP reached COP as high as 3.2 with external temperature of 12-17°C; even under temperature of -25°C, COP was measured at 1.36.
Electricity consumption (kWh): CO₂ HP (31,209) includes space heating; electric boiler (75,000) excludes space heating
Average electricity consumption per hour (kWh/d): CO₂HP (309); electric boiler (614)
Energy savings rate: 49.67%

Railway station office in Tongliao City

A conventional electric heater providing space heating during winter at the railway station office in Tongliao City was replaced with a CO₂ HP system, which, in addition, offers air conditioning during summer.

Observation period: CO₂HP (30th January 2013-12th April, 20th October 2013 – 19th of November); electric heater (20th October 2011-20th April 2012)
COP: CO₂heat pump reached COP as high as 3.2 with external temperature of 12-17°C. Under the temperature of -25°C, COP was measured at 1.33, which was higher than COP of the electric heater.
Electricity consumption (kWh): CO₂ HP (12,724) includes providing AC in summer; electric heater (35,000) excludes AC in summer.
Average electricity consumption per hour (kWh/d): CO₂ HP (121); electric heater (190)
Energy savings rate: 36.3%

In both cases, the CO₂ HP’s COP decreases as the external temperature decreases. Under external temperatures as low as -25°C, COP is still higher than that of conventional technology.

CO₂ HP: very suitable for Chinese railway stations

CO₂ HP systems are very suitable for application in Chinese railway stations, as they serve well to meet the low temperature conditions and other needs of such buildings. Railways in China cover large areas with various temperature conditions, and most of the stations are built in remote areas as single-unit buildings. A majority of the buildings require space heating during winter, air conditioning during the summer and hot water for daily use. Hot water is also needed for locomotive and train equipment cleaning as well as for repair and maintenance. The CO₂ heat pump system helps to achieve high efficiency while providing the needs of railway systems in various weather conditions.