Energy conservation in commercial buildings by optimizing the start stop sequence of the air-conditioning plant

Abstract

Sri Lanka has a warm humid climatic condition in low altitudes since it is located close to the equator. In many commercial buildings located in low altitudes, airconditioning is used as a popular option for providing the thermal comfort. However, this option is causing a lot of problems in recent past due to the energy crisis faced by Sri Lanka. The continuous increase of consumers has shifted the energy generation from hydropower to fossil fuels. Due to the recent price hikes of the petroleum in the world market, the electricity tariff rates have also been increased substantially. Therefore the cost of air-conditioning has increased considerably. With this, there is a considerable interest to optimize the performance of the air-conditioning systems. So that energy usage could be minimized.

The reduction of energy used for air-conditioning is not a straightforward task. This is because it is important to maintain the thermal comfort indoors at an acceptable level. Therefore, developing strategies to reduce the energy consumed for airconditioning is important which has to be achieved without compromising thermal comfort of the occupants. The feasibility of the adjusting starts stop sequence of the air-conditioning plants was investigated with the aid of computer simulations carried out for a ten-story building. The effect on thermal comfort was determined by using the Predicted Mean Vote (PMV) index. It was shown that the number of operating hours could be reduced without affecting the thermal comfort, especially towards the end of the office hours. Such saving could be extremely important for countries like Sri Lanka that is facing an energy crisis amid the need to increase the number of consumers.

The significance of such energy savings is quantified in terms of the number of rural houses that could be provided electricity. It is shown that the energy saved by adjusting the start stop sequence of a ten-story building is sufficient meet the electricity demand in about fifty rural houses.