A large cooling system of residential building in Changsha City in China was investigated in the summer of 2003. The relationships among the controlled variables, uncontrolled variables and the chillers’ performance were obtained empirically with the test data. A model of optimal operation for the system was established based on these empirical relationships. A parameter, system coefficient of performance (SCOP), is presented to analyze the effect of energy saving of the cooling system. The results show that the energy saving is likely to reach as high as 10% by applying the optimal model to the cooling system.

Accurate air-conditioning load forecasting is the precondition for the optimal control and energy saving operation of HVAC systems. They have developed many forecasting methods, such as multiple linear regression (MLR), autoregressive integrated moving average (ARIMA), grey model (GM) and artificial neural network (ANN), in the field of air-conditioning load prediction. However, none of them has enough accuracy to satisfy the practical demand. On the basis of these models existed, a novel forecasting method, called ‘RBF neural network (RBFNN) with combined residual error correction’, is developed in this paper. The new model adopts the advanced algorithm of neural network based on radial basis functions for the air-conditioning load forecasting, and uses the combined forecasting model, which is the combination of MLR, ARIMA and GM, to estimate the residual errors and correct the ultimate foresting results. A study case indicates that RBFNN with combined residual error correction has a much better forecasting accuracy than RBFNN itself and RBFNN with single-model correction.

Although variable-air-volume system (VAVS) can save much energy compared with other kind of HVAC system (e.g. constant-air-volume system (CAVS), fan-coil system (FCS)), it demands more investment. The rate of return of variable-air-volume system, which is closely related to the energy-saving rate of the system, ought to be taken into account by the engineers in the course of design. China has a wide territory and different climates that will impact on the energy-saving rate of variable-air-volume system. To help the engineers have a good idea of the rate of return of variable-air-volume system in different areas of China, it is necessary to establish such program that can evaluate the energy-saving rate of variable-air-volume system compared to constant-air-volume system and fan-coil system. In this paper, the specific energy models of the primary equipments in HVAC system are established, and the evaluation program for the energy-saving of variable-air-volume system compared to constant-air-volume system and fan-coil system are expounded. The parameters in the energy models, which may impact the validity of the evaluation program, can be obtained from the field-testing data or the performance data provided by the product manual. One small office building is taken as an example, the year-round energy simulations of the three kinds of HVAC systems (variable-air-volume system, constant-air-volume system and fan-coil system) of the same building have been made, and the energy-saving of the variable-air-volume system has been evaluated in six cities of China by the program. The evaluation program can also be used to analyze the energy-saving of variable-air-volume system in medium and big office buildings.

Experiments are conducted on human subjects to study the overall and the local thermal sensation and thermal comfort as well as the skin temperature distribution of the body in a recumbent posture under different environmental temperatures (21, 24, 26, and 29℃). Local skin temperatures are measured and 14 methods for the mean skin temperature overall are investigated. Statistical analysis showed that the Burton (3 points) method wiu obtain similar results for mean skin temperature compared with the other methods, e.g., Colin/Houdas (10 points), Hardy/DuBois (12 points), Stolwijk/Hardy (unweighted 10 points), and Mitchell/ Wyndham (unweighted 15 points), and is employed in this study due to its simplicity and convenience. Meanwhile, the relationship between skin temperature and thermal comfort and sensation is investigated and overall/local thermal sensation models based on the skin temperature are established according to the experimental data in this study.

Heating/cooling cost allocation is of growing concern in many countries because it contributes much to the energy conservation of central air-conditioning system. This paper intends to summarize the current studies and techniques on the heating/cooling cost allocation and discuss about the key problems to them. The contents mainly include the following parts: (1) probing into the methods of heating/cooling measurement; (2) establishing the calculation model for thermal billing; (3) presenting several typical systems for heating/cooling cost allocation. The significance of the paper is to help the engineers in this field have a good idea of the current development of heating/cooling cost allocation and promote the application of the relevant technologies to practice.