Energy demand for buildings has been rising during recent years. Increasing building energy consumption has caused many energy-related problems and environmental issues. The on-site community energy system application is a promising way of providing energy for buildings. Community energy system usage reduces the primary energy consumption and environmental effects of greenhouse gas (GHG) emissions compared to the implementation of the stand-alone energy systems. Furthermore, due to the increase in electricity price and shortage of fossil fuel resources, renewable energies and energy storage technologies could be great alternative solutions to solve energy-related problems. Generally, the energy system might include various technologies such as internal combustion engine, heat recovery system, boiler, thermal storage tank, battery, absorption chiller, ground source heat pump, heating coil, electric chiller, solar photovoltaics (PV) and solar thermal collectors, and seasonal thermal energy storage. The economic, technical and environmental impacts of energy systems depend on the system design and operational strategy. The focus of this thesis is to propose unified frameworks, including the mathematical formulation of all of the components to determine the optimal energy system configuration, the optimal size of each component, and optimal operating strategy. The proposed methodologies address the problems related to the optimal design of the energy system for both deterministic and stochastic cases. By the use of the proposed frameworks, the design of the energy system is investigated for different specified levels of GHG emissions ratio, and the purpose is to minimize the annual total cost. To account for uncertainties and to reduce the computational times and maintain accuracy, a novel strategy is developed to produce scenarios for the stochastic problem. System design is carried out to minimize the annual total cost and conditional value at risk (CVaR) of emissions for the confidence level of 95%. The results demonstrate how the system size changes due to uncertainty and as a function of the operational GHG emissions ratio. It is shown that with the present-day technology (without solar technologies and seasonal storage), the lowest amount of GHG emissions ratio is 37%. This indicates the need for significant technological development to overcome that ratio to be 10% of stand-alone systems. This thesis introduces novel performance curves (NPC) for determining the optimal operation of the energy system. By the use of this approach, it is possible to identify the optimal operation of the energy system without solving complex optimization procedures. The application of the proposed NPC strategy is investigated for various case studies in different locations. The usage of the proposed strategy leads to the best-operating cost-saving and operational GHG savings when compared to other published approaches. It has shown that other strategies are special (not always optimal) cases of the NPC strategy. Based on the extensive literature review, it is found that it is exceptionally complicated to apply the previously proposed models of seasonal thermal energy storage in optimization software. Besides, the high computational time is required to obtain an optimum size and operation of storage from an optimization software. This thesis also proposes a new flexible semi-analytical, semi-numerical methodology to model the heat transfer process of the borehole thermal energy storage to solve the above challenges. The model increases the flexibility of the storage operation since the model can control the process of the storage by also deciding the appropriate storage zone for charging and discharging. / Thesis / Doctor of Engineering (DEng)

An eight-lot residential subdivision in central Wairarapa is being developed to demonstrate the principles of sustainable resource management. Local energy sources for low and high grade use, including electricity sourced from proposed grid-integrated, on-site, distributed generation will supplement imported network electricity. A unique component is an internal loop grid for lot connection that interfaces with the local network through a single connection point. A decision model was designed as a decision-support tool for the development based on the annual supply-demand electrical energy balance, site infrastructure covenants and a range of economic and technology criteria. Solar and wind resources were assessed for potential supply of electricity to the community energy system. Three demand profiles were developed using supplied and estimated electrical demand data; and included assumptions on thermal performance of the houses, the use of low-grade heat, user behaviour, and appliance use. Supply and demand were analysed as daily average profiles by hour for each month of the year. The decision model outputs were designed to give a graphic view of the system options. The accompanying output datasets also enabled a number of scenarios for connection configurations, load management, and economic sensitivity to be explored for their impact on the communal approach to managing energy. The viability of the community energy system is significantly influenced by managing demand level in conjunction with system size, capital cost management, and tariffs for electricity import and export. Energy requirements could be best met in the short term by installing a site-wide mixed generation system of sized capacity between 5 and 11kW, supported by metering and information technology to deliver management data to the residents. Future research opportunities exist to continue monitoring technical, economic and social outcomes from this unique community development. Incentivising private investment in userfocussed energy innovations is an option for New Zealand to consider in the current climate of market-driven large scale electricity developments.