Céline Weber

Design and optimization of district energy systems

The reduction of CO2 emissions is a challenge for the coming decade, especially with the implementation of the Kyoto protocol. Since energy services (mainly heating and cooling of buildings) contribute to over 40% of the final energy consumption in a country like Switzerland, it is essential to find ways to improve the efficiency of energy conversion technologies. This can be done by combining these energy conversion technologies into polygeneration systems for instance. However, to ensure that polygeneration systems operate as often as possible at or near their optimal load, it is meaningful to implement systems that meet the requirements of more than just one building, in order to take advantage of the various load profiles of the buildings by compensating the fluctuations and having therefore a smoother operation. Besides, because these systems are complex and defacto difficult to operate, there are usually not justified in an individual building where no continuous professional control can be guaranteed. It is much more advantageous to implement them in a small plant that serves several buildings, and that is managed by an energy service company. This means that a network needs to be designed, that optimally connects the buildings and the energy conversion technologies together. A new methodology to design and optimize district energy systems is therefore being developed. The method (see figure) is based on the combination of an evolutionary algorithm, a network design and optimization algorithm, and several thermo- economic models for the energy conversion technologies. The first step is to select a district for which an energy system has to be developed or modified. The available renewable energy sources existing near or in the district, and thus the possible energy conversion technologies, are identified. Besides, all the relevant information regarding the district have to be structured: the geographical coordinates of the buildings, the load profiles of the buildings and finally the constraints (legal regulations, topology, existing networks,…). Once this information structuring phase is completed, the method for the design of the network and the energy conversion technologies can be applied, resulting in a number of different configurations. The costs and CO2-emissions are computed for each configuration on a Pareto-curve and the results compared. In this presentation, we present the first results of the implementation of this method.

Network synthesis for a district energy system: a step towards sustainability

In this paper, the first results of a new method for the configuration of district energy systems are presented. District energy systems are believed to help decreasing the CO 2 -emissions due to energy services (heating, cooling, electricity and hot water), by implementing polygeneration energy conversion technologies, connected to a group of buildings over a network. The synthesis of the network is an important but not trivial task, mainly because the problem involves a large number of integer variables and results in an mixed integer linear programming problem (MILP) that needs to be optimised.

A collaborative platform for sustainable building design based on model integration over the internet

Considerable potential exists for reducing life cycle environmental impacts of buildings in Japan. While energy consumption during the operation stage of a buildings lifetime is usually dominant, indirect energy use and pollutant emissions associated with production and disposal of building materials during construction and demolition are significant. For sustainable building design, interactions between the performance and dynamics of the building structure and energy systems must be considered. A collaborative platform based on the distributed object-based modelling environment, DOME, and a set of component models for sustainable building design analysis is presented. Integration examples of the component models to study particular building designs are described.