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Waste or recoverable heat is a resource that could be cost-effectively exploited by district heating (DH) systems to increase the efficiency of heat supply in buildings. This paper introduces the Bunhill waste heat recovery (WHR) system, a novel scheme that recovers waste energy from a ventilation shaft of the London Underground (LU) transport network. The system is based upon the installation of a heat recovery heat exchanger consisting of cooling coils and a reversible fan; the coils are connected to a heat pump that supplies low-carbon thermal energy to the Bunhill DH network in central London. One particularly important aspect of the Bunhill WHR system is its ability to operate in a way that not only provides heating to the local heat network, but can also simultaneously supply cooled air to the LU tunnels depending on the operation of the reversible fan. The current paper presents the results from an investigation into the benefits of integrating heating and cooling from the perspective of reducing carbon emissions and the levelised costs of energy from the WHR system, whilst also alleviating peak temperatures at nearby LU stations through the cooling provided. The findings of the investigation are presented together with recommendations for further development and future deployment of WHR systems, which not only apply to underground railways but also to other sources of recoverable heat. [ABSTRACT FROM AUTHOR]

The transformation of voltages leads to two types of energy losses in the form of heat, namely no-load losses which are inherent to the transformer and associated with its core; and load losses, caused by the resistance of the windings, which are a direct function of the electrical loading. This paper investigates how the waste heat generated by electrical transformers could be captured and reused via district heating networks. At first, the current availability of waste heat from transformers in the UK is assessed based on data from distribution network operators (DNOs). Potential methods for recovering waste heat from transformers are then presented, and the achievable benefits are discussed based upon carbon and cost savings against conventional heating technologies. [ABSTRACT FROM AUTHOR]

Wastewater offers the potential of a widespread resource for low-temperature waste heat, with wastewater in sewers normally at temperatures greater than ambient due to the use of hot water in buildings. Heat can be recovered from wastewater from different locations, such as the wastewater pipework within a building, the sewage network or at wastewater treatment plants (WWTPs). The latter represents an interesting alternative as wastewater flow rates are generally much higher in the effluent of treatment plants than in sewers. Additionally, the temperatures may be above ambient, as the biological sewage treatment process results in some heat generation. This paper investigates the potential availability of waste heat from WWTPs across the UK, with a total thermal energy output of 26.2 TWh [89.5 MMDth (US)] per annum being estimated. A possible configuration for recovering waste heat from the WWTP effluent is also presented and used to assess the benefits that could be obtained against conventional heating technologies based on a case study in London. Although the case study is based in the UK, the methodology hereby described can also be applied to evaluate the potential for heat recovery from wastewater treatment plants in other countries. [ABSTRACT FROM AUTHOR]

This paper describes the investigation of heat pumps for GreenSCIES, a 5th Generation heat network in Islington, London. The paper describes the GreenSCIES concept integrating Mobility, Power and Heat into a local energy system. At the heart of the system is a 5th generation heat network, which utilises an ambient heat network to capture secondary heat and share heat between different applications. The GreenSCIES network, technology utilised and buildings connected are described. Heat pumps are used to amplify the temperature of the ambient loop to deliver heat at the required temperature in connected buildings. A number of different heat pumps using different refrigerants and configurations were appraised in this study. This considered the performance, safety, environmental impact, operational and capital expenditure point of view. The study shows the importance of heat pump COP on the economics of operating the system and suggests innovative series arrangements in order to improve performance and economics. [ABSTRACT FROM AUTHOR]

The decarbonisation of the UK economy, driven by the national net-zero target, will require the large-scale electrification of important fields within the energy sector, such as transport and heating. The increase in electricity demand associated with this process will mean that flexible and integrated energy systems will be increasingly relevant in the future, especially in terms of improving the efficiency of energy use and alleviating stress on the electricity grid. District heating is a key technology in this process, particularly in densely populated urban centres, as it enables the integration of heating with other energy vectors and unlocks the potential for urban waste heat recovery to deliver significant carbon and cost savings. This paper aims to investigate how the benefits of a waste heat recovery system can be maximised through its flexible operation. This will be achieved by modelling the coupling of thermal energy storage (TES) with a district-scale heat pump, based upon time-of-use electricity prices and the concept of an existing system that recovers waste heat from the London Underground mass rapid transit system. The results from this investigation are reported together with recommendations for further development and future deployment of heat recovery from subway systems in general. [ABSTRACT FROM AUTHOR]

In order to combat climate change, many countries have been focusing their efforts on how to accelerate the transition towards a clean energy future, expanding access to energy across the world whilst significantly reducing the global carbon footprint. In the UK, as heating and cooling account for nearly half of the energy consumption and a third of carbon emissions, district heating and cooling networks represent a key technology for facilitating a smooth transition from current fossil fuel based energy to future low-carbon energy sources. A key contributor to these low carbon energy sources has been identified as the use of waste heat sources in urban environments, which can help to tackle both climate change and fuel poverty within cities. Despite their known advantages and wide application in many countries, heat networks currently supply only a small fraction of demand (~2% of heating needs) in the UK. This paper reviews how a new generation of district heating networks utilising waste heat can deliver massive carbon savings and are key to meeting future targets. In order to guarantee an efficient operation of the heat network, the installation of integrated control and monitoring systems is essential, as they allow measuring and adjusting key parameters, such as temperatures, pressures and flow rates, assuring that the system achieves optimum performance and stays within safe operating limits. This paper focuses on understanding how the performance of waste heat based district networks can be assessed by exploring best practices identified in the literature relating to control and monitoring of heat networks. Based on the review, the paper also provides recommendations for the best approach for monitoring the performance of a recently developed waste heat recovery system in Islington, London, involving the capture of waste heat from the London Underground, which is then upgraded and used to supply a local district heating network. [ABSTRACT FROM AUTHOR]

In 2019, the UK became the first major economy to pass laws to reduce its greenhouse gas emissions to net zero by 2050. Meeting this ambitious target not only requires a shift in energy supply from fossil fuels to low carbon energy sources, but also a reduction in energy demand through the roll-out of energy efficiency improvements to existing buildings. The UK has some of the oldest and most inefficient housing stock in Western Europe and the building sector is responsible for approximately half of energy consumption. The present work has a strong focus on exploring low carbon heat supply tehcnologies could be applied to existing housing stock, using the London Borough of Islington (LBI) as a case study. The applicability of low carbon energy efficiency measures to a range of different building archetype prominent within LBI is discussed and evaluated. The methodology implemented includes both qualitative and quantitative assessment of the opportunities and benefits, with a focus on applicability, cost, and carbon savings associated with two low carbon heat supply options. The overall evaluation approach presented in the paper is applicable to other urban areas in the UK and elsewhere. Key conclusion from the study and planned next steps are also discussed. [ABSTRACT FROM AUTHOR]

Heat networks are a key technology proposed in the UK Government's Clean Growth Strategy for delivering low carbon and low-cost energy to urban communities in the UK. Currently, around 2% of all heat in the UK is provided by heat networks compared to other countries such as Sweden/Denmark, where they have more than 30% delivered in this way. Most of the Scandinavian systems use high temperature 3rd or 4th generation heat networks (>50-80°C) [>122-176°F] and these are often driven by fossil fuel powered Combined Heat and Power (CHP), which are carbon intensive and also impact on local pollution/particulates. In the UK there is a drive towards 5th generation heat networks involving ambient temperature loops (13 - 25°C) [55-77°F]. These systems deliver additional benefits and savings as they are able to share heat/coolth across the network and capture waste heat from secondary heat sources like the heat from London Underground ventilation shafts and local data centres. They utilise heat pumps to deliver heat or cold from the loop to individual applications or buildings and they avoid emissions of particulates associated with CHP. This paper investigates how existing 3rd and 4th generation networks can be connected into 5th generation systems. It uses the 3rd generation Bunhill CHP installation in the London borough of Islington as a case study to investigate the relative performance when converting a system. The paper describes the techno-economic models developed to show how the Bunhill installation might perform when connected to 5th generation, including CAPEX and engineering connection approaches. [ABSTRACT FROM AUTHOR]