Global issues of greenhouse gas emissions, security of supply and decreasing fossil fuel resources calls for increased use of renewable energy and energy efficiency measures for existing technology. In the domestic sector, main energy consumption occurs due to space heating and hot water which is mostly provided by gas or oil boiler via hydronic central heating system in the UK. In order to diversify fossil fuel usage, reduce emissions and security supply, implementation of efficient technology (e.g. heat pump) along with renewable technology is vital. The heat pump is an efficient technology based on the vapour compression cycle, mostly driven by electric motors where it provides heat at high temperature by consuming energy from low temperature sources such as air, ground or water. Electric heat pumps (EHPs) have good potential to displace existing gas boiler system to meet domestic heating demand. However, conventional hydronic systems operate with high flow temperatures where EHP's performance drops as temperature lift increases. In addition, if vast deployment of EHPs occurs then it could create issues for the electricity distribution network. Also, until the major portion of electricity is generated by renewable sources, EHP's operating at high temperatures will not give significant benefit in terms of C02 savings compared gas boiler heating. The aim of the presented work is to develop an engine driven heat pump system. This will meet the designed domestic heat demand at high flow temperatures suitable for conventional wet radiator systems. It will also use the waste heat recovered from the engine. The developed engine driven heat pump (ENHP) should also help in diversification of fossil fuel usage in domestic sector, emission reduction and thermal comfort improvement. Liquid biofuels or gas engine concepts will be possible at a later date. The diesel engine was used with modifications to take advantage of coolant and exhaust heat recovery. The engine was coupled with a reciprocating open compressor as a drive source. A water-to-water heat pump was developed for testing purposes. Diesel engine heat pump (DEHP) performance was tested at three different engine speeds and four different water flow temperatures for given evaporation temperature conditions. DEHP test results showed a strong influence of engine speed and condensing temperature on overall total heat output and heat recovery. Test results showed that heat recovery from the engine contributes about 31 % in total heat output. DEHP test results at various conditions gave primary energy ratio in a range of 0.93 to 2 showing better performance compared to conventional gas boiler. Speed variation of the DEHP system showed that it has the potential to match domestic heating demand ( at 70-73 0 C) between -4.5°c to 9°C air/water temperature by varying engine speed, hence reduction in on/off cycling. In terms of flow temperature requirements for retrofit application, the DEHP test results showed that it can provide flow temperatures in the range of 70°C to 73°C which is in a similar range of gas boiler flow temperature range in a typical household. In addition, DEHP system can provide water flow rate in a range of 5 to 20 lImin which is suitable to meet typical space heating and/or DHW flow rate demand. Another common issue was noise associated with the DEHP system and this was also reduced by acoustic insulation around the engine-compressor assembly showing potential for domestic installation where noise and vibration could be achieved in a similar range to conventional heating system. Overall, DEHP test results showed potential as a transition retrofit technology with possible use of renewable energy sources (e.g. biofuel) with integration of thermal/electrical energy storage to meet heating and electricity demand locally.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:677465 |
| Date | January 2015 |
| Creators | Shah, Nikhilkumar |
| Publisher | Ulster University |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
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