Transport, Industrial and Commercial Refrigeration – A research project

The Climate Change Act commits the UK to reach net zero emissions by 2050, tackling hard to abate areas. A significant energy end use, often overlooked in policy, is refrigeration and there is a gap in our understanding of transport, industrial and commercial refrigeration (TICR) emissions. Essential for multiple applications across the cold chain, this paper assesses the size of TICR emissions, and opportunities for research and innovation. Our initial results suggest that 6% of industrial electricity use is for refrigeration, with large uncertainty in this figure. To address this knowledge gap, we reviewed available data sources to estimate the UK’s carbon emissions and produce a breakdown per application sector. In an industry dominated by SMEs with low-risk appetite and innovations with low readiness levels, we explore ways, which TICR could decarbonise in order to reach the UK’s Net Zero ambitions, through innovation and better data

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

Heat Recovery Opportunities from Electrical Substation Transformers

The transformation of voltages in electrical substations leads to energy losses in the form of waste heat; the quantity of which depends on transformer size and electrical loading. This paper investigates how a novel waste heat source, namely transformer waste heat could be harvested and distributed via district heating networks. Firstly, the investigation considered nameplate heat loss factors to quantify the theoretical waste heat potential from electrical substation transformers in England, Wales and Northern Ireland, which varied from 3.0 to 5.4 TWh.a-1, equivalent to between 0.7 and 1.25% of annual heat demand for these countries, depending on loading assumptions. A number of heat recovery approaches which could be integrated with existing transformer cooling systems were then proposed. A spreadsheet model was then developed to simulate heat recovery from a transformer, together with the upgrade of the recovered heat using a heat pump prior to delivery via district heating. The model was used to evaluate the merits of capturing transformer waste heat losses, estimated using industry supplied electrical loading data, to meet different heat network demands based on an existing network, compared to conventional heating technologies. Findings suggest that the system proposed can achieve levelised costs that are up to 17% lower than the running costs of air-source heat pumps, whilst reducing emissions by almost 80% when displacing gas boilers. The methodology hereby described can also be used to evaluate the feasibility of recovering transformer waste heat in other countries

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

District Heat Networks: Addressing Categorisation to Unlock Deployment Potential

District heating (DH) consists of substantial energy infrastructures in many urban areas around the world, which offer a significant opportunity for achieving economies of scale and increasing the energy efficiency of the built environment. Heat networks have been identified by the UK Government as an essential mechanism for decarbonising heat. However, different to other European countries, the UK heat network market is minimal, meeting only around 3% of overall heat demand. Many of these networks use Combined Heat and Power (CHP) technologies, often driven by carbon-intensive gas engines. If the UK is to achieve its netzero target, these CHP systems need to be modified or replaced with low-carbon alternatives such as heat pumps. One challenge to the growth of low-carbon heat networks in the UK relates to a lack of clarity when categorising them as either communal or district. These systems have different merits and peculiarities that affect their potential as scalable tools for decarbonisation. This paper aims to address this challenge by proposing new definitions that clearly separate district and communal concepts. This is achieved by analysing the status of heat networks in the UK and London, which is complemented by a review of current definitions available in the literature. The potential implications of misclassification to the development of DH in the UK are then discussed, with a focus on how policy needs to establish clear boundaries in order to guide the transition towards a low-carbon DH market in the UK. By addressing the issue of inconsistent categorisation and improving data accuracy, this paper serves as a foundation for future research and development efforts aimed at overcoming the barriers to the broader deployment of low-carbon heat networks in the UK

Decarbonisation pathways for fossil fuel-based district heating networks using heat pumps

Decarbonising the energy sector is crucial for addressing climate change concerns. Traditional UK district heating networks heavily rely on large, centralised gas-fired plants driven by economies of scale. However, the changing energy landscape necessitates a shift towards low-carbon alternatives in existing heating systems. This study fills a significant knowledge gap by examining strategies to decarbonise district heating networks (HN) through the integration of heat pumps (HPs) at different temperatures. It comprehensively assesses cost-effectiveness, energy efficiency, and operational carbon emissions. The findings emphasize the seamless integration of HPs into diverse settings, enabling them to extract heat from air, ground, or water sources and resulting in substantial carbon savings. Moreover, harnessing waste heat from the London Underground presents a substantial opportunity for emission reductions. Nevertheless, the viability of biogas is limited in densely populated areas like London. This research makes a noteworthy contribution to UK decarbonisation efforts, offering a practical roadmap for widespread adoption of HPs and a sustainable future

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

Crescimento inicial de pinhão-manso sob efeito de calagem e adubação, em solos de Mato Grosso do Sul.

bitstream/item/66215/1/32010.pdfFERTBIO

Characterization of time delay in power hardware in the loop setups

The testing of complex power components by means of power hardware in the loop (PHIL) requires accurate and stable PHIL platforms. The total time delay typically present within these platforms is commonly acknowledged to be an important factor to be considered due to its impact on accuracy and stability. However, a thorough assessment of the total loop delay in PHIL platforms has not been performed in the literature. Therefore, time delay is typically accounted for as a constant parameter. However, with the detailed analysis of the total loop delay performed in this article, variability in time delay has been detected as a result of the interaction between discrete components. Furthermore, a time delay characterization methodology (which includes variability in time delay) has been proposed. This will allow for performing stability analysis with higher precision as well as to perform accurate compensation of these delays. The implications on stability and accuracy that the time delay variability can introduce in PHIL simulations has also been studied. Finally, with an experimental validation procedure, the presence of the variability and the effectiveness of the proposed characterization approach have been demonstrated