Abstract
Methods of increasing energy efficiency and reducing greenhouse gas emission are widely developed across the whole world. Housing energy consumption as a large energy consumption among different energy sectors, such as industry, transportation, needs to be paid more attention. In the UK, gas is still the main fuel used for providing heating in homes and space heating is responsible for over 60% of domestic energy usage.This work investigates the optimal operation of the low carbon space heating system based on a real-world project providing a community level space heating with low carbon technologies and thermal energy storage system. The proposed space heating system consists of borehole thermal storage and heat pumps. The heat pump has relatively high efficiency compared to boilers and with proper operation, electricity consumption and CO2 emission can be largely reduced. Borehole thermal storage uses the natural heat source, by coupling with heat pumps the heat pump efficiency can be increased.
The existing research on the borehole mainly focused on the modelling, verification, and optimization on the sizing/material of the system and when it comes to coupling with heat pumps, most research showed the system operation results, temperature behaviour with constant heat injection/extraction and monetary and environmental benefits of the projects. With heat injection/extraction and natural heat replenishment under the ground, the heat energy storage becomes a very complicated problem when coupled with heat pumps especially when the temperature is a key aspect of the system. As a result, how temperature affecting the system efficiency and what is the influence of the operation of the borehole storage coupled with heat pumps have not been studied.
This thesis delivers the researching findings at each stage in each chapter. Starting from the high-level energy chain analysis, borehole temperature behaviour study and borehole charging strategy optimization. For single/multiple charging/discharging cycles, it enables the borehole to store less heat and still retains the performance of the Ground Source Heat Pump (GSHP) during the heating season and for limited available heat flux input- by obtaining the optimized charging strategy, the heat accumulation in the borehole is more efficient. The total GSHP electricity consumption is reduced along with the CO2 emission reduction and in the long-term operation, borehole thermal energy storage benefit more in the future.
| Date of Award | 2019 |
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| Original language | English |
| Awarding Institution |
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| Supervisor | Chenghong Gu (Supervisor) & Furong Li (Supervisor) |