Solar assisted heat pumps

Solar Assisted Heat Pumps have the potential to provide low carbon heat for domestic hot water generation and low temperature heating. They have advantages over conventional solar thermal systems because they can generate heating and hot water during periods of low or zero solar, whist still maintain the advantage of not needing to be connected to the gas grid. They are simple in nature and can be installed in a wide range of applications. They are also currently uncommon in the UK so a thorough understanding of the operating performance and characteristics is required. This is potentially an important energy technology that can be used to reduce heating energy consumption and reduce CO2 equivalent emissions in buildings. The paper describes the technology and presents an investigation in an office application. It describes an experimental investigation of solar assisted heat pumps which gives the relative performance compared to conventional methods

Investigation of an integrated low carbon solar assisted heat pump

© 2016, International Institute of Refrigeration. All rights reserved.Solar Assisted Heat Pumps have the potential to provide low carbon heat for domestic hot water generation and low temperature heating. They have advantages over conventional solar thermal systems because they can generate heating and hot water during periods of low or zero solar, whist still maintain the advantage of not needing to be connected to the gas grid. They are simple in nature and can be installed in a wide range of applications. They are also currently uncommon in the UK so a thorough understanding of the operating performance and characteristics is required. This is potentially an important energy technology that can be used to reduce heating energy consumption and reduce CO2 equivalent emissions in buildings. The paper describes the technology and presents an investigation in an office application. It describes an experimental investigation of solar assisted heat pumps which gives the relative performance compared to conventional methods

Simulation of the heat recovery use of R744 systems in a supermarket

This paper describes the outcomes a research project that investigate the improvement in the COP of an enhanced booster R744 refrigeration system that provided MT cooling for chilled food cabinets and LT cooling for cold room/frozen food cabinets by recovering the heat rejected and using it more for other building services applications in the supermarket. For instance, the heat reclaimed can be used for heating, HWS or to drive absorption chillers, either in whole or in part. To demonstrate the potential of the heat reclaimed within the supermarket and its impact on the store’s CO2e emissions, a feasibility study has been performed to examine the innovative system compared to of the existing conventional system which will cover the cooling demands of an existing supermarket. In order to achieve this, the data collected by a smart energy monitoring system will be used to examine the working of the novel system when covering the cooling demands of the store. The energy consumption of the novel system will be analyzed according to thermodynamic theory. Using an Excel model, the potential heat reclaimed will be mathematically investigated for best practice applications of heat recovery. The energy saved and CO2e emission reduction achieved in apply the novel system will be determined and analysed

Smart Cities – Thermal Networks

This paper presents a feasibility study of the technical and economic viability of introducing combined heating and cooling networks, referred to collectively in this paper as “thermal networks”. The steps used for this study include the identification of the most viable thermal network configuration, followed by analysis of a number of potential building mix scenarios and estimation of their respective potential impact on energy consumption, carbon emissions and economics. The final step was a discussion of the potential benefits and drawbacks associated with the implementation of the selected thermal network. This study revealed that by utilising thermal networks, with central energy centres, approximately 1831 tonnes of CO2 could be saved per annum compared to traditional supply methods. With a minimum assumed system life of 25 years this equates to approximately 46000 tonnes CO2. It has also been identified that, in conjunction with a marginal shift in policy to encourage an increase in service led economy, thermal networks can become technically and economically viable with around 40-year net present value payback periods and by introducing financial support from governments, such as 9 – 12 pence investment per kWh of cooling, the payback periods could be reduced to around 25 years

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

Improvement of the isolation of the air cavity for ventilated cladding systems for fire safety purposes

Cladding systems are needed for different reasons, amongst them to provide adequate internal environment, thermal insulation, ventilation, and furthermore after recent fire incidents to prevent the spread of fire. In the case of Grenfell Tower, the majority of the spread of the fire was via combustion of materials of the envelope. Along with the removal of such highly-flammable materials from cladding panels, in this paper the isolation of the air cavity of the ventilated cladding systems is to be analysed and hopefully improved with an extra fire safety measure. The aim of air cavities is mainly to provide resistance to moisture and condensation via natural ventilation as well as to ensure an optimum indoor climate under normal duty. However, in the event of a fire, the air cavity is a potential narrow path for the fire to quickly spread up to other storeys. To prevent the exposure of the materials to the flames, a strategy combining thermally-reacting fire-resistant expanding foam and a fire retardant substance is to be discussed under proper compartmentalisation conditions and a previous correct strategy of fire barriers and other fire safety measures within the building. A control systems strategy relying on the mentioned adequate compartmentalisation will be also described. Means of installation, replacement and decommissioning in such a system are also assessed

Reflective Glass Effect on Energy Consumption and Food Quality in Delicatessen Cabinets

Retail supermarkets are responsible for around 3% of total electrical energy consumed in the United Kingdom and the most energy is used in refrigeration systems, particularly for operation of open displays such as delicatessen cabinets which consume approximately 50%. Although the cabinets are energy intensive, they are commonly used in supermarkets for displaying unwrapped chilled food stuffs. These cabinets are associated with the weight loss and quality deterioration of food stuffs being reported frequently as the cause for their high operational costs. This paper presents an investigation on the cause and rectification of weight loss in delicatessen cabinets. Specifically, the paper describes the effective use of low emissivity glass in reducing the impact of the thermal infrared radiation on the food temperatures and energy consumption

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

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