Performance-objective design for a renewable energy transportation circuit of Christchurch, New Zealand
A systems engineering based methodology for exploring technical sustainability in the social and environmental context was used to investigate a specific transportation load in the city of Christchurch. The process includes defining sustainability performance parameters in engineering terms, defining service objectives in socio-economic terms, and then generating concept designs using standard engineering modeling. The approach reflects a balance between form and function, and we refer to the resulting concepts as energy architecture. In this study, the performance-objective methodology was used to develop the energy architecture for a wind and solar powered public transportation service that provides a 35km circuit of schools, shopping malls, and industrial parks. The service objective for the design was set by an existing bus service. A number of concepts were explored for the renewable energy supply of an electric light rail trolley circuit on a dedicated (not grid connected) electric supply network. Each concept represents a different degree of capital investment and system complexity, and achieves a certain level of the desired transportation service on any given day. Real-time simulated performance modeled with historical local weather data was used to compare the performance of each of the possible architectures to the objective. A service factor was calculated to evaluate the level of transport service performance compared to the objective. The results demonstrate that no amount of investment in wind and solar energy capacity can provide the same service as the fossil fuel system. When pumped-hydro storage of wind and solar energy was added to the system, the service factor could be increased to 100%. The modeling exercise points out that a relatively modest investment in wind generation can produce a useful service. However, the schedule would need to be flexible to match the wind energy availability. A system like this could work if a communication system could be implemented to provide real-time schedule information.