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2. ENGINEERING AND TECHNOLOGY
The utilisation of renewable energy resources for electricity and thermal generation is extremely important in Ireland due to the lack of indigenous fossil fuel resources and the high dependence on imported fossil fuels. The release of environmentally-damaging greenhouse gases in the combustion of fossil fuels in electricity and thermal generation is also a major issue. In Ireland, the domestic dwelling is recognised as one of the biggest energy consumers. The use of renewable energy technologies to provide electricity, heating and hotwater can effectively offset the usage of fossil fuels. The aim of this research study was to develop a novel technique for the optimised integration of grid-connected renewable energy systems to satisfy the entire energy demand in a domestic dwelling. The development of the technique was carried out in a series of logical stages. In the first stage, a sub-technique for the optimised integration of grid-connected micro-renewable electricity generation systems was developed. In this sub-technique a detailed and accurate economic analysis of the investigated systems is performed. Net present value is the metric employed in the economic analysis and the system which achieves the highest net present value is deemed the optimal system. High-resolution measured electrical load data and a user-specified renewable energy requirement are employed in this sub-technique. The renewable energy requirement is the percentage of the household electricity demand that must be satisfied by the on-site grid-connected micro-renewable electricity generation system. In the second stage, a sub-technique for the optimised integration of grid-connected micro-renewable thermal generation systems was developed. In this sub-technique, following the completion of the life cycle cost (economic) analysis of the investigated systems, the system which achieves the lowest life cycle cost is deemed the optimal system. High-resolution measured thermal load data is utilised in this sub-technique. Finally, in the third stage, the overall integration technique was then developed by amalgamating these two sub-techniques. Life cycle cost analysis is again used to determine the optimal system. In order to demonstrate their application, the two sub-techniques and overall technique were deployed with Irish conditions. The investigated systems were formed from commercially-available products; the products selected for this study were six micro wind turbines, three solar PV modules, three air source heat pumps and three solar thermal collectors. When the sub-technique for the optimised integration of grid-connected micro renewable electricity generation systems was deployed under current Irish conditions, the optimal system, which meets the 50% renewable energy requirement, was a single micro wind turbine having a capacity of 2.4 kW. However, this optimal system is not economically viable as its net present value is negative. When the sub-technique for the optimised integration of grid-connected micro renewable thermal generation systems was deployed, the optimal system was a single air source heat pump having a thermal capacity of 14 kW. This optimal system is economically viable in comparison with an oil boiler system or an electrical heating system; however it is not economically viable compared with a gas boiler system. Finally, when the overall integration technique was deployed, the optimal system was a combination of an air source heat pump having a thermal capacity of 14 kW and grid supplied electricity; however this system is not economically viable in comparison with an economically-best-performing conventional combination of grid supplied electricity and a gas boiler system. The influence of several parameters on the economic performance of the investigated systems was also studied with the developed sub-techniques and overall technique. Due to the wide range of micro-renewable energy generation systems available on the market and the broad range of existing capacities, the developed integration technique is extremely useful for performing an accurate economic analysis and determining a system that is most suitable for a domestic dwelling.
Li, Z. (2014) Optimised Integration of Grid-Connected Renewable Energy Technologies for Domestic Application in Ireland, Doctoral Thesis, Technological University Dublin. doi:10.21427/D7PP56