Energy savings technologies for heating, ventilation and air-conditioning system
The heating, ventilation and air-conditioning system consumes about 1/3–2/3 of the total building energy. Therefore, studies on the operation strategies of the air-conditioning system and building envelope thermal properties have always been a hot topic. Deng studied the effects of air-conditioning operation mode on the energy consumption of a model building with different external wall insulations in the hot summer and cold winter region in China. It was found that the energy saving effect of external insulation was better than that of internal insulation under continuous operation mode, and vice versa under intermittence mode with low-and-medium-temperature tolerance.
As the number of subway lines increased with rapid speed in China, the research on how to improve the energy efficiency of metro stations becomes particularly important. The heating, ventilation and air-conditioning system account for more than 30% of the total operating energy consumption of the subway systems. Li performed field measurements on the ventilation and air-conditioning system in a subway station in Changsha, China and found that the air-conditioning system was operating at 10–50% of the design load during testing period with most of the thermal loads were sensible and the night time cooling load was about 80% of that in the daytime.
Data center consumed about 1 percent of global electricity use, and has attracted many researchers to find innovative technologies to reduce its energy consumption. Heat pipe is one of the technologies that can be used to cool the data center with low energy consumption while reducing the local hot spots problem. Meng developed a 1-D steady-state mathematical model of a novel loop heat pipe that removes the compensation chamber of the loop heat pipe and adds capillary wick at the end of liquid line. The model was able to calculate the operation temperature with small relative errors of <13%, which could provide help to the design of a novel loop heat pipe experiment.
Water atomization process is worth studying in mine exhaust heat recovery system. Chen carried out an experimental study on the influence of gas disturbance on water atomization in a curved diffuser in a ventilation system and found that injection pressure is the dominant factor affecting the breakup length of liquid film near the atomizing nozzle and dispersed phase fraction for droplets reaches the maximum with an air flow rate equal to 3.2 m3/s.
Energy savings through building envelope, load forecasting and rating system
Zero energy buildings are based on a bioclimatic architecture concept and demand responses to internet of things control strategies. From the architectural design perspective, vertical greening system and green roof have received more and more attention worldwide recently as a passive measured to reduce building energy consumption and improve indoor thermal comfort. Tan proposed an energy saving method by covering both the vertical facades and building roof with green plants. Through the experiment, it was found that the building integrated green plants help to achieve energy savings in winter by 18% and in summer by 25%.
Load forecasting is very important in the building energy management system which helps to improve the energy efficiency of the heating, ventilation and air-conditioning system by matching the equipment output capacity with the thermal load of the building. It can also integrate with the internet of things for renewable energy generation. Lee developed load forecasting models for office buildings in Korean using calendar data and weather data and found that the quadratic model was most suitable to be
used in Korea’s climate. Peng used a long short-term memory neural network method and developed a regression model to predict the energy consumption of a shopping mall in Shenzhen with an average relative error of less than 10%.
A number of rating systems have been developed to evaluate the performance of green/ sustainable buildings, with different methods and the number of indicators. Al-Addous and Albatayneh (2020) performed a review on the energy rating method for housing and evaluated the limitation of the assessment systems. The authors raised concerns on using the R-value alone to evaluate the building thermal performance in the rating system and the accuracy of the building energy simulation software.
From: Building integrated renewable energy
Yaolin Lin, Wei Yang, Xiaoli Hao and Changxiong Yu
