Project SHOES: Secondary heat opportunities from electrical substations

Through the mechanism of stepping up and stepping down voltages with electrical power transformers, losses in the form of heat occur and are dissipated to the atmosphere. These losses have the opportunity to be recovered and upgraded to help support the thermal demands of buildings as allow carbon secondary heat source. The electrification of heat facilitates the uptake of electrically driven heat pumps that are efficient means of upgrading low temperature heat sources to commonly used temperatures and the employment of district heating networks enables the transition of these alternative heat sources into the economy. This paper describes the results discovered from an initial investigation on the contribution available from a transformer energy recovery scheme using the Southampton Bulk Supply Point substation and District Heating Scheme as a case study. Benefits to the heat sector and asset owner are analysed from the results considering the techno-economic, environmental and social performance with the aim to provide guidance to the engineering community for further in-depth feasibility studies on this waste energy recovery concep

Cooling with heat recovery for electrical cable tunnels in cities

Within cities, electrical power is often distributed by means of underground cable tunnels, frequently extending for many kilometres. Cables can generate significant heat, with the quantity of heat being directly related to the electrical load carried. Tunnel air temperatures are generally controlled by ventilation using outside air; preventing the cables from overheating. If active cooling was provided, tunnel air temperatures could be further reduced, permitting higher electrical loadings to be used. Using an air/water heat exchanger to cool the outside air entering the ventilation shaft has been investigated. The temperature of the heat extracted (to water) was increased using a heat pump before transfer to a heat network. Benefits identified included reduction in cable temperatures, and carbon and cost savings compared to conventional heat delivery

Heat Recovery Opportunities from Wastewater Treatment Plants

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

Ambient loop district heating and cooling networks with integrated mobility, power and interseasonal storage

This paper describes a heat pump investigation for GreenSCIES (GS), a fifth Generation district heating and cooling (5DHC) network in Islington, London. The paper describes the GreenSCIES concept integrating Mobility, Power and Heat into a Smart Local Energy System (SLES). At the heart of the system is an ultra-low temperature ambient loop network, which permits bi-directional flow within the pipes to allow energy exchange between heating and cooling customers at different times and in different locations, depending on where demand is at any given time. An existing data centre provides the primary source of waste heat for the scheme. Heat pumps in distributed energy centres are utilised to amplify the temperature of the ambient loop to deliver heat in connected buildings. The energy centres integrate heat pumps with building-mounted solar photovoltaic (PV) systems and electric vehicle (EV) charging points. The paper provides an overview of the integrated SLES concept, focussing on the heat pump selection and the short and long-term thermal storage options designed for the scheme. The results show that even the smaller constructible ‘New River’ scheme will save 5,000 tons of CO2e annually. This will tend to 100% as the grid decarbonise further. Therefore, the GS SLES concept applied to urban areas could deliver significant carbon emission savings in the UK and elsewhere. Practical application: Project GreenSCIES, is a detailed design study to develop a Smart, Local Energy System (SLES) for a large community in the London Borough of Islington. Our consortium have developed an innovative SLES concept, centred around a fifth generation district heating and cooling network. The GS ambient loop systems have negligible losses and much greater efficiencies than traditional district heat networks. As recognised by the UK Government’s Heat and Buildings Strategy, ambient loop systems should be considered where large-scale neighbourhood regeneration occurs. The proposed SLES concept applied to wider urban areas could deliver significant carbon emission savings in the UK

Driving success towards zero carbon energy targets for UK's Local Authorities

This paper draws on three case studies which show feasible and economic results in meeting net zero carbon emissions targets through Smart Local Energy Systems (SLES) in different localities across England, exploring opportunities to utilise waste heat from industry. They are based on the GreenSCIES model for which the blueprint was developed in London, Study 1. It consists of a fifth generation (5G) ambient loop district heat network using waste heat from a data centre, integrated with electric vehicle charging, storage and solar PV. The network includes decentralised heat pumps and allows for (i) heat sharing between buildings and (ii) applications for heat recovery from local sources. Study 2 is based on a heat network with waste heat from a foundry and some cooling supply and heat storage in the aquifer. Study 3 explored waste heat from a glassworks and considered mine workings for providing heat storage. These SLES projects illustrate how to integrate local waste heat sources in 3G and 4G heat networks, adapting the original GreenSCIES concept, providing pathways towards net zero carbon for a diverse range of urban locations with different waste heat sources, and further demonstrate the importance of collaboration between researchers, local government and industry

Waste heat recovery from urban electrical cable tunnels

Electrical power distribution within cities is most often distributed through underground cables located just below the road surface. Due to steadily increasing electricity demands, many power suppliers are making large investments in housing these cables in underground tunnels. These urban cable tunnels often extend to many kilometres in length. Through the electrical loading of the cables a significant amount of heat is generated. Often this heat has to be removed through ventilation in order to avoid overheating the cables and to provide safe conditions for access. As opposed to rejecting the heat to the atmosphere, this low grade energy could potentially be recovered, upgraded if necessary, and distributed to nearby heat users above ground. This paper discusses possible heat recovery methods applicable for urban electricity distribution networks, i.e. transformers and cable tunnels. It also presents results from a modelling-based preliminary feasibility study which used cable tunnels in London as a case study

Unchecked box Heat from Underground Energy London (Heat FUEL)

This paper aims to introduce a heat recovery scheme that will collect waste energy from the London Underground in Islington, London. The system is based on the installation of an air to water heat exchanger within a ventilation shaft of the London Underground. The heat captured is distributed to a heat pump, which upgrades it to a suitable temperature for reuse and provides low carbon energy to a local district heating network. This paper introduces some of the key aspects of the technical design of this novel urban heat recovery and delivery system. Its theoretical performance is evaluated and compared to the previous heating method used for the buildings supplied by the network. It also provides recommendations for the implementation of future installations for secondary heat recovery and reuse in cities

Opportunities for integrating underground railways into low carbon urban energy networks: A review

Cities demand vast amounts of energy for their everyday operation, resulting in significant degradation of energy in the form of heat in the urban environment. This leads to high cooling requirements in cities, while also presenting the opportunity to reuse such waste heat in order to provide low-carbon heating for buildings and processes. Among the many potential energy sources that could be exploited in urban areas, underground railway tunnels are particularly attractive, as the operation of the trains produce considerable amounts of heat throughout the year. This paper reviews how secondary energy sources in urban areas can be integrated into heating and cooling networks, with emphasis on underground rail tunnels. This involves investigating potential urban waste heat sources and the existing state-of-the-art technologies that could be applied to efficiently recover this secondary energy, as well as analyzing how district heating and cooling networks have been a key mechanism to allow for a smooth transition from current fossil fuel based to future low-carbon energy sources

The Importance of Heat Pump COP in the Economics of 5th Generation District Heating and Cooling Networks

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

Waste Heat Recovery from Underground Railways – Evaluating the Cooling Potential

The Bunhill Waste Heat Recovery (WHR) System is a first of its kind scheme that will recover waste energy from a ventilation shaft of the London Underground (LU) network. The system is based upon the installation of a heat recovery heat exchanger that consists of cooling coils and a reversible fan. The coils are connected to a heat pump that supplies low carbon thermal energy to the Bunhill Heat Network in the London Borough of Islington. 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 provides an analysis of the heating and cooling duties and their associated cost and carbon savings against conventional technologies based upon a mathematical model of the WHR system. The model is able to predict the condition of the coil surface according to air inlet parameters, and this is used to calculate the latent and sensible cooling loads, which are applied to simulate how the system impacts the local tunnel environment, with peak temperature reductions of up to 7.2 °C being estimated for adjacent stations in 2030. The results from these analyses are reported, together with recommendations for further development and future deployment of heat recovery from metro systems