Analysis of Energy Efficiency and Energy Savings at CityU

20 August 2018

Dr. Lin ZHANG, Assistant Professor, School of Energy and Environment, City University of Hong Kong.

The drastic increase of energy consumption issue has emerged significantly along with the depletion of energy resources. The overall energy consumption has shown increasing trend for past 10 years in Hong Kong. As this trend is projected to continue, various management trials have implemented to cope with energy issues. Hong Kong government mainly adopts two approaches, reducing energy intensity and increasing energy efficiency. Building sector occupies over 90% of total electricity usage in Hong Kong. This drives Hong Kong government to focus on improving building energy efficiency.

Many governments and researchers suggest buildings of educational institute as a major target for sustainability. University is a significant stakeholder for sustainable future, as it educates and trains future professionals who will take a major role in the society. Universities are long-term owner oriented and have social responsibility to pursue a low carbon economy with sustainability. Therefore, universities can be a sustainability innovator through research activities and act as models for the community in terms of their physical operations.

From 2011 to 2015, CityU consumed energy for 57.3 MkWh on average, and saved around 1697.78 MWh annually. In terms of final energy use, we identify four major sub-users, which are general lighting/AC, chiller plant, lab equipment, and others. Energy consumption for general operation (general lighting/AC, chiller plant) and research (lab equipment) occupy a considerable proportion. General lighting/AC sector, the biggest stakeholder, occupies 34.5% in average with increasing tendency. Chiller plant sector takes 32.3% with slightly decreasing trend. Las instrument sector exhibits increasing tendency continuously over time, taking 14.5% of share in average. The rest occupied 18.6% and exhibited decrease in its proportion in 2015.

Figure 1: Annual energy consumption and by end-use in CityU

Based on sub-use data, we observed the drastic increase of energy consumption on 2013, which can be explained by the completion and operation of the new academic building. General lighting/AC section shows the continuous increase of energy consumption. Additionally, the proportion of general lighting/AC section has extended persistently over past 5 years. This illustrates that the most overriding section is general lighting/AC section, as the section shows a significant impact on total energy consumption.

The energy efficiency of campus is estimated using the stochastic frontier analysis. The seasonal cycle is observed in the efficiency tendencies. This can be explained by three major energy uses in CityU, which are general lighting/AC, chiller plant, and lab instrument sector. As high temperature increases the demand for cooling services for people and lab instrument maintenance, and the needs for chiller plant operation, the campus energy efficiency decreases over the seasons with higher temperature. In 2013, a new academic building was in operation. The inefficient use of facilities in the new building led to a drop in energy efficiency and significant increase in total energy consumption. However, efficiency score shows increasing tendency after 2013, and achieves the similar level in 2015 with higher energy consumption comparing with 2012.

Figure 2: Energy efficiency and performance score of CityU over time

Energy efficiency and performance score in terms of savings have improved after the introduction of new academic building in 2013. Our decomposition analysis and sectional analysis of energy consumption suggest that CityU should provide policy guidance for the research sector, as it shows considerable impact on energy intensity of CityU and highly affects the energy use in the lab instrument.


Acknowledgment: The work described in this short article was fully supported by the Campus Sustainability Fund of the City University of Hong Kong (Project No. 6986045)".