Determination of building cooling loads using real weather data.

The main objective of this study is to develop a new computer based tool for use by engineers when designing and selecting an air conditioning system. Moreover, the design of the developed model must be robust enough for it to be implemented in the design stage of the building. Therefore this study was initiated to overcome some of the problems that were encountered using the well-established cooling load method. For instance, cooling load calculations of a building are dependent on the external dynamic environmental factors. The load on the building is also affected by the internal dynamic environmental factors, in addition to the presence of the building envelope and its harmonics due to time lags. On the other hand, the application of using daily weather data in calculating the cooling load as well as the dynamic internal and external environmental factors is difficult to carry out manually because of the tediousness of the repetitive calculation which can deter designers from attempting detailed load profiling and this can result in more inaccurate estimates. For this reason, a dynamic model has been developed to account for the harmonic nature of the cooling load components on an hourly basis. A computer model was constructed to carry out the calculations and to test the results. The CLTD/CLF method was used for the model because of its flexibility. Moreover, the dynamic behaviour of the model can be used to compare results from different building designs obtained from this study. These results showed that the real load profiles were superior to the profile from using the static traditional method. Results from the analysis of the new method can clearly demonstrate the use of the computer program and allow variations in cooling load, peak and minimum load to be observed. Presenting the results in this way will enable a designer to size and to select the type of machine and predict the planned maintenance periods. Moreover, the program allows for effects of climate change on the performance of building cooling systems to be simulated. Application of Qbasic programming with the CLTD/CLF method in combination with the Sinusoidal equation was also been used to account for the weather harmonics. The use of real weather data also allows the designer to see typical patterns of plant usage. If global warming becomes a reality we can use the computer program to predict how changes in weather patterns will effect cooling systems and can plan accordingly.