Optimisation Of Inter-Seasonal Ground Source Heat Pumps With Predictive Behavioural Control

In practice, heat pumps (HP) often do not perform as expected. This is due to many factors such as how well the system and the ground loop are designed, installed and subsequently maintained and how well they are operated and controlled in the field. Improving overall system design and demonstrating increased HP performance and higher reliability are core objectives for this research. Performance instability and variations in ground source heat pump (GSHP) system output has been observed previously and this indicates that detailed research is required for example (i) to identify the relationship between dynamic performance and seasonal ground temperature patterns, (ii) to address the operation, installation and control opportunities that arise from (i). This project investigates all of these issues. This thesis focuses on the monitoring of the long-term operation of a 500 kW installed GSHP system with the aim of understanding and establishing the current trend performance characteristics of the installation. The research involved combination of experimental measurements and analysis, mathematical simulation and the development of an empirical transient model that could be generally applied. Despite the importance of the effect of ground temperatures on performance, relatively little data has been published on the effect of disturbed underground temperature distributions. The author has therefore developed a novel mathematical model for the analysis of disturbed ground temperatures over time. The novel mathematical model developed has been used to predict the disturbed seasonal underground temperatures based on daily fluid and air temperature data and has been validated against real historical data. It was concluded from the critical literature review that the dynamic long term performance investigation of GSHP systems using transient models is not well understood. Therefore the work described in this thesis has focused on the development of a generic empirical transient system model of a GSHP system. This model has been developed using TRNSYS 17 software. This has permitted investigation of the effects of different control strategies using a dry air cooler (DAC) for heat rejection, energy consumption of the HP, the overall performance of the system and ground temperature variations. The main novelty and contributions to science from this work is: The better understanding of the effect of ground temperature variation over time and its effect on the system’s performance. The development of new measurement methods for assessing system performance. The use of ground temperature in the prediction and control of system performance, together with an analysis of the effects of specific interventions or control methodologies. The development of a novel mathematical model for predicting disturbed ground temperature. The development of a novel GSHP model using TRNSYS. The development and investigation of novel control strategies using DAC

Magnetic Attraction

In the 2015 United Nations Climate Change Conference, COP 21 in Paris, world leaders have been negotiating to limit the global warming to below 2°C by 2100. These talks are necessary to avoid serious climate catastrophes and reduce greenhouse gas emissions by increasing the use of zero carbon technologies such as magnetic refrigeration for heating or cooling. This is an emerging, innovative and potential low carbon technology. Due to the increased concern about global warming and an ever increasing energy consumption, the interest in magnetic refrigeration as a new heating or cooling technology competitive to conventional vapour compression has grown considerably over the last 15 years. The principle of magnetic refrigeration is based on a phenomenon known as magnetocaloric effect (MCE). This was discovered by Emil Warburg in 1881 and is related to the property of some exotic materials such as Gadolinium and Dysprosium that heat up when applying a magnetic field and cool down when the magnetic field is removed

The Value of hybrid heat pumps

In households not connected to mains gas, electric heat pumps offer the opportunity to provide high efficiency low carbon heating as an alternative to electric heaters, LPG or oil based systems. As a result this technology is an ideal heating solution for the 4 million households in the UK that don’t have access to mains gas. However, electric heat pumps also offer large scale carbon savings when used for heating in the 22 million households that do have gas as well as mains electricity. In these applications hybrid heat pumps present an attractive opportunity for reducing fossil fuel consumption. In March 2013, the Department for Energy and Climate Change (DECC) published a document entitled “The Future of Heating: Meeting the challenge”. This report predicted that by 2030 approximately 26% of the UK’s heating energy output will be met by air source heat pumps alone, and as much as 56% will be met by hybrid system

Life-Saving Cooling

Large areas of many developing countries have no grid electricity. According to the International Energy Agency’s (IEA) World Energy Outlook (2015) report, 1.2 billion people lacked access to electricity in 2013, which is equivalent to more than 16 percent of the world population. The research reported by IEA (2015) showed that more than 95 percent of those living without electricity live in rural areas, mainly in sub-Saharan Africa and developing Asia where there is no distribution grid for electricity, and there are no prospects of the grid reaching them in the near future see Figure 1. Even in areas with grid power, the demand for electricity has outpaced supply resulting in unreliable electricity availability, insufficient for continuous refrigeration

Control strategy of a novel dry air ground source (DAGS) system

Based on a number of studies carried out; it has been identified that Ground Source Heat Pump (GSHP) systems are widely used as one of the preferred low carbon technologies in the UK. The use of these systems is due to their economic advantages and potential reduction of carbon footprint. However, a number of the studies have highlighted that the systems are either installed incorrectly or operated and controlled improperly and therefore result in poor performance. GSHP performance is affected by the temperature of the ground and when thermally saturated its efficiency reduces significantly. This paper investigates the potential to reduce the level of thermal saturation by rejecting heat via a Dry Air Cooler (DAC) when the ground and ambient temperatures favour this. DACs are often fitted to GSHP systems to reject heat during extreme conditions to protect the system, rather than improve performance. In this investigation, an empirical Transient System Simulation (TRNSYS) model has been developed and used to investigate the control algorithms so as to identify the optimal operation and control strategies for DAGS system for enhancing the system efficiency. Specifically, the paper investigates the effect of using a DAC in conjunction with a GSHP system. This includes investigating the (i) energy input into the GSHP system, (ii) ground temperatures and (iii) Coefficient of Performance (COP). The results show significant savings can be achieved

UK Centre for Efficient and Renewable Energy in Buildings (CEREB)- Lessons Learned After 5 Years of Running

The Centre for Efficient and Renewable Energy in Buildings (CEREB) is a unique, teaching, research and demonstration resource for the built environment. It is located at London South Bank University (LSBU) and showcases different renewable and low carbon energy solutions for which performance data is captured for teaching and research. The technologies included are Ground Source Heat Pump (GSHP) for providing heating and cooling to the 8,500 m2 K2 building which is located below CEREB. The solar thermal collectors are used to provide the hot water demand of the K2 building, with back-up boilers to supplement the required heat on cloudy days. The centre itself has additional technologies including solar fibre optic lighting, solar Photovoltaic (PV) panels, solar thermal tubes (evacuated tubes), phase change materials, absorption chiller for cooling, and a weather station, which is crucial for understanding the performance of the various technologies at different times of the year and different weather conditions. This paper consists of two parts; the first part presents a brief description of CEREB and the K2 building including the concept behind the design, sustainability measures and key features followed by a description of the technologies used in the building and in the centre. The second part presents lessons learned from the design, construction and running the building over the last 5 years with results from the solar thermal panels and PV Panels

Experimental investigation of using Graphene Oxide with Ethylene Glycol and Water mixture to improve the performance of a car radiator

Nanofluids offer a good alternative heat transfer mediums with approximately five-fold heat transfer enhancement. This paper presents the results from a research study carried out on the use of Graphene Oxide/ Ethylene glycol Mixture (GnO/H2O-EG) Nanofluid as the heat transfer medium in a car radiator. The radiator consisted of 30 vertical tubes with elliptical cross section. Air makes a cross flow inside the tube bank with constant speed. The system was tested with three different Nanofluid concentrations (0.1, 0.3 and 0.5% by weight). The tests were conducted for flow rates ranging between 2 to 5 lit/min which corresponds to Reynolds number between 14000 and 38000. The effect on fluid outlet temperature to the radiator was analyzed for different flow rates and constant inlet temperature. The data were compared to that obtained with potable water in the radiator. The result of the comparison revealed that the use of graphene oxide increased the temperature drop across can radiator by upto 22 % compared to 50% Glycol mixture

Metering measurement challenges & monitoring of a large scale ground source heat pump (GSHP) system

Ground Source Heat Pumps (GSHP) have significant potential to reduce carbon emissions. The performance of heat pumps is highly dependent on their interaction with the ground and specifically the extraction and injection of the heat. A number of literature reviews has shown how the performance of GSHP systems vary in practice when compared to the theoretical aspects. This paper provides detailed investigative work on heat metering installation difficulties and associated errors which affect the long term practical performance of GSHP systems. Particularly, incorrect installation of heat meters is a sensitive issue for a heat metering scheme designed to evaluate the performance of any heating technology since it’s likely that they will bias the readings. The findings obtained from this work confirm a range of generic installation problems that the refrigeration, air condition and heat pump (RACHP) industry is currently facing. The findings obtained from this study provide useful information for design and implementation of future GSHP systems in terms of improving energy efficiency as well as reducing costs. This study has identified a range of installation errors which include (i) temperature sensors being incorrectly positioned and/or installed (ii) incorrect selection of heat meters (iii) type of thermocouple pockets and (iv) poorly insulated sensors, all of which have contributed to an uncertainty error of ±20% of the system performance

Metering measurement challenges & monitoring of a large scale ground source heat pump (GSHP) system

Ground Source Heat Pumps (GSHP) have significant potential to reduce carbon emissions. The performance of heat pumps is highly dependent on their interaction with the ground and specifically the extraction and injection of the heat. A number of literature reviews has shown how the performance of GSHP systems vary in practice when compared to the theoretical aspects. This paper provides detailed investigative work on heat metering installation difficulties and associated errors which affect the long term practical performance of GSHP systems. Particularly, incorrect installation of heat meters is a sensitive issue for a heat metering scheme designed to evaluate the performance of any heating technology since it’s likely that they will bias the readings. The findings obtained from this work confirm a range of generic installation problems that the refrigeration, air condition and heat pump (RACHP) industry is currently facing. The findings obtained from this study provide useful information for design and implementation of future GSHP systems in terms of improving energy efficiency as well as reducing costs. This study has identified a range of installation errors which include (i) temperature sensors being incorrectly positioned and/or installed (ii) incorrect selection of heat meters (iii) type of thermocouple pockets and (iv) poorly insulated sensors, all of which have contributed to an uncertainty error of ±20% of the system performance

Smart cities – Thermal networks for London

This paper presents a feasibility study of the technical and economic viability of introducing combined heating and cooling networks in London, referred to collectively in this paper as “thermal networks”. The study begins with a review of the current and potential future demographic and energy trends for London. This is followed with detailed energy analysis of three different thermal network configurations to identify the most viable thermal network configuration for London. Future projection analysis was also carried based on a number of potential building mix scenarios. The study revealed that by using thermal network with heat recovery produced significant energy savings and subsequent carbon savings by upto 56%. The majority of the energy saving and equivalent CO⁠2 emission savings resulted from the reduction of the heating energy required to cater for the loads due the viability of heat recovery from the cooling network into the return of the heating network. The study also revealed that by utilising thermal networks, with central energy centre approximately 1831 tonnes of CO⁠2 equivalent could be saved per annum compared to traditional supply methods. With a minimum assumed system life of 25 years this equates to approximately 46,000 tonnes CO⁠2