1. Department Name IITD Nabeel Ahmed Khan, Bishwajit Bhattacharjee*
Industry Day Theme # 4 : Sustainable Habitat
Building Thermal Design Optimization
Nabeel Ahmed Khan, Bishwajit Bhattacharjee*
Abstract
Proper selection of building envelope parameters is very crucial in determining the energy consumption by the building during the operational stage. Although there are a number of options available for each parameter, only one combination will result in minimum energy consumption for the building. The search for this optimal design combination can not be based on trial and error method but requires a heuristic search technique to search the whole domain of possible design combinations and take out the best one. This poster presents an approach which can be used for the selection of building envelope parameters at the design stage through coupling of an optimization algorithm and building energy modelling program. The resulting design combination will result in considerable savings in the operational energy consumption of the building.
Result
A medium occupancy commercial building at Delhi was chosen for the case study. Wall material, glazing material and roof material for the building were optimized using Genetic Algorithm optimization approach. In the base case, typical construction materials were used in the building envelope. The above mentioned parameters were optimized using the building thermal optimization approach and optimized envelope materials obtained were used in the GA case. Admittance method [2] was used as a building energy simulation program and was used to calculate thermal load on the building.
Fig. 1 Model of the case study building in building energy simulation software
The energy consumption was calculated on a representative day of every month for the whole year for both the base case and GA case and the results have been presented in Table 1.
Table 1. The annual energy consumption of the case study building in base stage and in optimized stage.
Introduction
With increase in the size of buildings in the past few decades, the operational energy consumption have increased to huge proportions. The major part of which is consumed in maintaining thermal comfort inside the building. The passive building envelope parameters like shape, orientation, wall material etc. plays a very crucial role in determining the amount of heat gain which enters into the building through walls, windows and roof throughout the year. Proper selection of these passive building envelope parameters at the design stage can help in reducing heat gain and hence energy consumption due to thermal to a considerable extent. In Building Thermal design optimization, optimization techniques like genetic algorithm are used to optimize the building envelope parameters with the objective of minimizing the thermal load of the building. Optimization algorithm is coupled with a energy modelling program or software which takes building envelope parameters as input and gives thermal load as the output. The optimization algorithm is then used to find out the most optimal combination of building envelope parameters which will result in minimum thermal load for the building.
Materials and Methods
Shape, orientation, wall material, glass material, roof material, window to wall ratio are selected as the building envelope parameters to be optimized and the available options for these parameters are also decided upon. As there can be a number of design combinations using different options for each parameter, Genetic algorithm [1] is used for optimization of these parameters. Genetic algorithm is a heuristic search technique which heuristically search through the design space to give an optimal value with respect to a given objective function. Minimization of thermal load is chosen as the objective function in the optimization process. Genetic algorithm is used to optimize the above mentioned building envelope parameters with the objective of minimizing the thermal load and the resulting optimal solution is used in the design of the building. A case study building was optimized using the above mentioned approach. To Validate the results the given building was modelled in a building energy simulation software. The building was first modelled using the typical envelope parameters and then using the optimized parameters. The energy consumption obtained in both the cases were compared to check the effectiveness Building thermal design optimization approach.
Case study building
Energy Consumption
Base case
4000 kWh
GA case
3262 kWh
Department Name IITD
Conclusions
As can be seen the from the results of the case study building, the Building operational energy consumption can be brought down considerably using the Building thermal design optimization approach.
References
[1] D.E. Goldberg, Genetic Algorithms in Search, Optimization, and Machine Learning, Addison-Wesley, Reading, MA, 1989.
[2] J.A. Clarke, Energy Simulation in Building Design, Adam Hilger Ltd., Bristol and Boston, 1985.
Industrial Significance
If During the design stage of the building , building thermal optimization approach is used for the selection of building envelope parameters, considerable energy can be saved during the operational phase of the building.
Technology Readiness Level: The results will be produced in the form of ready to use guidelines for design of buildings.