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In the debate on the decarbonisation of heat, renewable electricity tends to play a much more dominant role than green gases, despite the potential advantages of gas in terms of utilising existing transportation networks and end-use appliances. Informed comparisons are hampered by information asymmetry; the renewable electricity has seen a huge grid level deployment whereas low-carbon hydrogen or bio-methane have been limited to some small, stand-alone trials. This paper explores the regulatory and commercial challenges of implementing the first UK neighbourhood level 100% low-carbon hydrogen demonstration project. We draw on existing literature and action research to identify the key practical barriers currently hindering the ability of strategically important actors to accelerate the substitution of natural gas with low carbon hydrogen in local gas networks. This paper adds much needed contextual depth to existing generic and theoretical understandings of low-carbon hydrogen for heat transition feasibility. The learnings from pilot projects, about the exclusion of hydrogen calorific value from the Local Distribution Zone calorific value calculation, Special Purpose Vehicle companies, holding of liability and future costs to consumers, need to be quickly transferred into resilient operational practice, or gas repurposing projects will continue to be less desirable than electrification using existing regulations, and with more rapid delivery. • This paper explores barriers for the first UK 100% hydrogen distribution project. • Learnings from pilot projects need to be transferred into UK operational practice. • Existing regulations present barriers to gas distribution innovation projects. [ABSTRACT FROM AUTHOR]

This paper investigates factors associated with variation in daily total (electricity and gas) energy consumption in domestic buildings using linked pre-COVID-19 smart meter, weather, building thermal characteristics, and socio-technical survey data covering appliance ownership, demographics, behaviours, and attitudes for two nested sub-samples of 1418 and 682 British households selected from the Smart Energy Research Laboratory (SERL) Observatory panel. Linear mixed effects modelling resulted in adjusted R2 between 63% and 80% depending on sample size and combinations of contextual data used. Increased daily energy consumption was significantly associated (p -value < 0.05, VIF < 5) with: households living in buildings with more rooms and bedrooms, that are older, more detached, have air-conditioning, and experience colder (more heating degree days) or less sunny weather; households with more adult occupants, more children, older adult occupants, higher heating temperature setpoints, and that do not try to save energy. The results demonstrate the value of smart meter data linked with contextual data for improving understanding of energy demand in British housing. Accredited UK researchers are invited to apply to access the data, which has recently been updated to include over 13,000 households from across Great Britain. This paper provides guidance on appropriate methods to use when analysing the data. [ABSTRACT FROM AUTHOR]

Abstract: The climate in cities differs significantly from those found in the surrounding area. These differences results from modifications of the Earth''s surface that alters the disposition of “natural energy balance” at a micro-scale and the concentration of activities that results in anthropogenic emissions that change the composition of the atmosphere. These urban effects have distinctive temporal and spatial properties with different impacts on building energy performance depending on their purpose which are rarely accounted for. This paper examines performance implications of a change-of-use (from office to residential) in the context of the UK government''s proposal to encourage regeneration and to meet housing needs. However, the diurnal occupation and activity patterns of these uses are distinct. For office buildings, with daytime occupation, focus is on the diurnal heating cycle driven by solar energy gains to which internal energy sources must be added. For residential buildings occupation and activity are primarily associated with the diurnal cooling period, and lower levels of activity that results in a primary heating need. This paper highlights the link between the timing of the urban climate effects, the urban setting and energy performance in a typical city street, where buildings are currently designed for commercial use. It employs London''s current and projected climate to simulate heating and cooling demands. By studying the role of urban form and its implications on the suitability of a buildings function we find that a ‘form first’ approach should be considered in the early design stages over the standard ‘fabric first’ approach. [Copyright &y& Elsevier]

[Display omitted] • A whole system approach to studying a low-temperature HGSHP system. • 3D coupled TH model with realistic boundaries and dynamic heat pump COP. • Design of a HGSHP system to support a 5th generation DHC network. • Different factors on performance of the HGSHP system and ground thermal behaviour. • Ground moisture transfer, cooling process and buried depth are important. Exploitation of shallow ground and its low-grade heat potential is fundamental to designing 5th generation district heating and cooling (DHC) networks. Horizontal ground-source heat pump (HGSHP) systems are a common way to utilize shallow geothermal energy. Realistic estimation and prediction of performance of a HGSHP system and shallow ground thermal behaviour should consider the whole system including building heating and cooling load, heat pump and ground heat exchanger, and the ground. This should be accompanied by realistic atmospheric and ground conditions. In this paper, a three-dimensional coupled thermal–hydraulic model with realistic boundary conditions adopting a whole system approach is presented. Dynamic heat pump coefficient of performance (COP) that depends on seasonal variation of heating/cooling demand and ground conditions are also considered. Model validations are conducted against experimental and analytical results in literatures. The model is applied for evaluating a HGSHP system to support development of a 5th generation DHC network on a potential site in the UK. Several influencing factors, such as ground moisture transfer, building thermal load mode, buried depth of ground loops, and initial ground temperature profile are studied to assess performance efficiency of the HGSHP system and evolution of ground thermal behaviour in response to heat extraction or rejection into the ground. The results show that 5% of the monthly total heat demand of the site could be met by the designed HGSHP system, consisting of 200 U-shaped ground loops buried at the depth of 3 m and pure water as the heat carrier. Overlooking the ground moisture transfer or hyperbolizing the ground saturation would overestimate the load-carrying capacity of the HGSHP system. The HGSHP system is more efficient with a higher heat pump COP under the heating and cooling mode than under the heating-only mode. Predicted performance of the HGSHP system improves with buried depth of the ground loops. The results also show that a 1 ℃ increase in the undisturbed ground temperature could suffice up to 8% of the monthly total heat demand of the site. [ABSTRACT FROM AUTHOR]

• A well-functioning space heating system can operate below 70 °C for 98% of the year and below 55 °C for 71% of the year. • The performance gap between measured and calculated energy use is widening across building age groups, with a clear increase for post-1980 buildings. • Pre-1980 buildings can operate with supply temperatures below 70 °C for 96–99% of the year and below 55 °C for 67–71% of the year. • Building envelope improvement, whilst recommended, is not a pre-requisite for using low-temperature supply in pre-1980 buildings. • Post-1980 buildings could have limitations in respect of using low-temperature heat under windy conditions. Decarbonising heat in the UK by 2050 will require the wider adoption of low-temperature heat. Current systems, largely relying on gas boilers, have design operating temperatures of 82/71 °C (supply/return) while new standards for 4th Generation District Heating are 55/25 °C. Local authorities must set-up strategies to get their buildings "Heat network ready" but this raises the question of the ability for existing buildings to use low-temperature heat. The aim and the novelty of this paper is to establish a relationship between an energy 'performance gap' in Scottish public buildings and their ability to use low-temperature heat. This performance gap has been evaluated for 121 non-domestic buildings, primarily schools, operated by The City of Edinburgh Council. Space heating system are assumed oversized by 10%. The results show that renovation of the building envelope, while highly desirable, is not a pre-requisite for using low-temperature heat in pre-1980 constructed buildings, which represent 64% of the stock. It also highlights that post-1980 buildings, predominantly utilising mechanical ventilation systems, demonstrate an increasing performance gap which could limit their ability to use reduced operating temperature, especially in windy conditions. [ABSTRACT FROM AUTHOR]

• A micro-CHP system integrating PVT collectors, a SE and energy storage is considered. • A transient model is developed to evaluate technoeconomic and environmental performance. • The primary energy savings and carbon emission reduction amount to 35% and 37%. • The discounted payback period of the system is 28 years. • The system has greater environmental benefits and a longer payback period than alternatives. This paper presents a comprehensive analysis of the energetic, economic and environmental performance of a micro-combined heat and power (CHP) system that comprises 29.5 m2 of hybrid photovoltaic-thermal (PVT) collectors, a 1-kW e Stirling engine (SE) and energy storage. First, a model for the solar micro-CHP system, which includes a validated transient model for the SE micro-CHP unit, is developed. Parametric analyses are performed throughout a year to evaluate the effects of key component sizes and operating parameters, including collector flow rate, storage tank size, SE micro-CHP flow rate, and battery capacity, on the energetic, economic and environmental performance of the proposed system using real hourly weather data, and thermal and electrical energy demand profiles of a detached house located in London (UK). The optimum component sizes and operating parameters are determined accordingly. The daily and monthly operating characteristics of the system are evaluated, and its annual performance is compared to those of a reference system (gas boiler plus grid electricity), as well as of other alternative solar-CHP systems including a PVT-assisted heat pump system and a standalone PVT system. The results indicate that the installation of such a system can achieve an annual electricity self-sufficiency of 87% and an annual thermal energy demand coverage of 99%, along with annual primary energy savings and carbon emission reduction rate of 35% and 37% relative to the reference system. Over 30 years of operation, the net present value (NPV) of the proposed system is £1990 and the discounted payback period is 28 years. The economics of the proposed system is very sensitive to utility prices, especially the electricity purchase price. Relative to the alternative solar systems, the proposed system offers greater environmental benefits but has a longer payback period. This implies that although the energy saving and emission reduction potential of the proposed system is significant, the initial/capital investment, especially of the SE CHP unit and the PVT collector array, are currently high, so efforts should focus on the cost reduction of these technologies. [ABSTRACT FROM AUTHOR]

• Data-driven and comprehensive thermodynamic technology models are developed. • Multi-fidelity approaches are used to compare heat-generation solutions. • Centralised CHP systems appear to be the most profitable option at present. • Heat pumps can achieve a significant degree of heat decarbonisation (55–62%). • Thermodynamic models reduce uncertainty by 75% compared to black-box approaches. This paper presents a multi-scale framework for the design and comparison of centralised and distributed heat generation solutions. An extensive analysis of commercially available products on the UK market is conducted to gather information on the performance and cost of a range of gas-fired combined heat and power (CHP) systems, air-source heat pumps (ASHPs) and ground-source heat pumps (GSHPs). Data-driven models with associated uncertainty bounds are derived from the collected data, which capture cost and performance variations with scale (i.e. , size and rating) and operating conditions. In addition, a comprehensive thermoeconomic (thermodynamic and component-costing) heat pump model, validated against manufacturer data, is developed to capture design-related performance and cost variations, thus reducing technology-related model uncertainties. The novelty of this paper lies in the use of multi-fidelity approaches for the comparison of the economic and environmental potential of important heat-generation solutions: (i) centralised gas-fired CHP systems associated with district heating network; (ii) gas-fired CHP systems or GSHPs providing heat to differentiated energy communities; and (iii) small-scale micro-CHP systems, ASHPs or GSHPs, installed at the household level. The pathways are evaluated for the case of the Isle of Dogs district in London, UK. A centralised CHP system appears as the most profitable option, achieving annual savings of £13 M compared to the use of decentralised boilers and a levelised cost of heat equal to 31 £/MWh th. However, if the carbon intensity of the electrical grid continues to reduce at current rates, CHP systems will only provide minimal carbon savings compared to boilers (<6%), with heat pumps achieving significant heat decarbonisation (55–62%). Differentiating between high- and low-performance and cost heat pump designs shows that the former, although 25% more expensive, have significantly lower annualised costs (£4.9 M vs. £7.7 M) and 12% higher CO 2 -equivalent savings. The uncertainty propagation reveals that data-driven and detailed thermoeconomic models can reduce the uncertainty in the total annualised energy cost and emissions by more than 75% compared to simplified black-box approaches, while the economic comparison of centralised CHP systems and domestic heat pumps for various electricity and gas price scenarios provides guidance to support energy policy. [ABSTRACT FROM AUTHOR]

This paper provides an analysis of the relationships between dwelling, household, and motivation, behaviour and perception characteristics and winter heating setpoint temperatures (n = 111) and heating periods (n = 148 and 145) used in UK social housing. The work capitalises on primary data from a socio-technical household survey, undertaken in Plymouth, UK, during 2015, which was merged with building audit data collected by the social housing association managing the properties. The mean reported heating setpoint temperature was 20.9 °C and the average weekday and weekend day heating periods were 9.5 h and 11.2 h respectively. The results suggest that heating setpoint temperatures and periods vary greatly among UK social houses, but there are clear systematic variations according to dwelling, household, and motivation, behaviour and perception characteristics. The research could enable social housing providers, the government and commercial organisations to target energy efficiency measures (i.e. thermal upgrades) and social interventions (i.e. behaviour change) at those dwellings and households where their impact may be most beneficial. The results presented could also be used to better inform the assumptions of heating preferences in energy models, which could result in more realistic predictions of the space heating demands of social housing and the potential energy savings from refurbishment measures. [ABSTRACT FROM AUTHOR]

• Over the technologies' typical 20-year lifetime, most UK dwellings have a cost optimum low-carbon heating system using air source heat pumps. • Dwelling properties and spatiotemporal variabilities significantly change the optimum low-carbon technology from blue hydrogen boilers, direct electrical heating, and air source heat pumps, to ground source heat pumps. • Direct electrical heating is economically preferred over heat pumps in lower demand dwellings and with analysis over shorter timescales. • Incentives for low-carbon heating need to target adoption of efficient technologies to reduce the greater increase in network demands. An understanding of heating technologies from the consumers' perspective is critical to ensure low-carbon technologies are adopted for reducing their current associated emissions. Existing studies from the consumers' perspective do not compare and optimise the full range and combinations of potential heating systems. There is also little consideration of how spatiotemporal and dwelling variations combined alter the economic and environmental effectiveness of technologies. The novelty of this paper is the creation and use of a new comprehensive framework to capture the range of heating technologies and their viability for any specific dwelling's traits and climate from customers' perspective which is missing from current studies. The model optimises combinations of prime heaters, energy sources, ancillary solar technologies and sizes, thermal energy storage sizes and tariffs with hourly heating simulation across a year and compares their operation, capital, and lifetime costs alongside emissions to realise the true preferential heating systems for customers, which could be used by various stakeholders. Using the UK as a case study, the results show electrified heating is generally the optimum lifetime cost solution, mainly from air source heat pumps coupled with photovoltaics. However, direct electrical heating becomes more economically viable as dwelling demands reduce from smaller dwellings or warmer climates, as shorter durations of the ownership are considered, or with capital cost constraints from lower income households. Understanding this is of high importance, as without correctly targeted incentives, a larger uptake of direct electrical heating may occur, which will burden the electrical network and generation to a greater extent than more efficient heat pumps. [ABSTRACT FROM AUTHOR]

This paper uses a whole system approach to examine system design and planning strategies that enhance the system value of electrifying heating and identify trade-offs between consumers' investment and infrastructure requirements for decarbonising heating in buildings. We present a novel integrated model of heat, electricity and gas systems, HEGIT, to investigate different heat electrification strategies using the UK as the case study from two perspectives: (i) a system planning perspective regarding the scope and timing of electrification; and (ii) a demand-side perspective regarding the operational and investment schemes on the consumer side. Our results indicate that complete electrification of heating increases peak electricity demand by 170%, resulting in a 160% increase in the required installed capacity in the electricity grid. However, this effect can be moderated by implementing smart demand-side schemes. Grid integration of heat pumps combined with thermal storage at the consumer-end was shown to unlock significant potential for diurnal load shifting, thereby reducing the electricity grid reinforcement requirements. For example, our results show that a 5 b£ investment in such demand-side flexibility schemes can reduce the total system transition cost by about 22 b£ compared to the case of relying solely on supply-side flexibility. In such a case, it is also possible to reduce consumer investment by lowering the output temperature of heat pumps from 55 °C to 45 °C and sharing the heating duty with electric resistance heaters. Furthermore, our results suggest that, when used at a domestic scale, ground-source heat pumps offer limited system value since their advantages (lower peak demand and reduced variations in electric heating loads) can instead be provided by grid-integration of air-source heat pumps and increased thermal storage capacity at a lower cost to consumers and with additional flexibility benefits for the electricity grid. Lastly, our results show that, regardless of consumers' investment and operation decisions, the UK electricity grid can reliably accommodate close to 50% of the heating demand, but this can be increased to about 75% by implementing smart operation schemes at the consumer end. • Value of smart electrification is examined from system and demand-side perspectives. • Coordinated system planning is key to accelerate electrification and lower system costs. • Consumer costs are reduced by sharing demand between electric heater and heat pump. • Air-source heat pump with storage has higher system value than ground-source heat pump. • Smart operation schemes can increase the optimal degree of electrification by 25%. [ABSTRACT FROM AUTHOR]

The decarbonisation of heat requires a transition from gas boilers to low-carbon heating systems such as heat pumps. Efficiency gains can be achieved by linking heating systems through ambient loops called Fifth Generation District Heating and Cooling (5GDHC) networks. The UK needs working demonstrators to understand both the technical and practical challenges in the heat transition. The Balanced Energy Network (BEN) links two buildings on LSBU's campus and is the UK's first 5GDHC system at scale and among the first in the world to be retrofit in parallel to an incumbent gas system and include an active demand side response control system to toggle between energy vectors in way that minimises cost and carbon emissions. This paper presents performance data from its first year of operation in baseline mode, as it was commissioned and optimised. High temperature heat pumps were retrofit to an existing gas boiler circuit and match the 79 °C output temperature of the gas boiler system. No fabric upgrades were required and no pipes, ducts or heat emitters were resized, however the system maintained performance to reduce overall building carbon emissions by 13% and gas use by 40% across both buildings compared to the pervious heating season while the system was in use. • First known UK 5th Gen ambient heat network retrofit to existing buildings. • Demonstration of high temperature heat pumps (79 °C) maintaining a high COP. • Performance data from heat pumps retrofit into existing gas heating systems. • Demonstration of a phased transition from gas to heat pumps in complex buildings. • Up to 40% reduction in use CO2 emissions with opportunities to optimise over time. [ABSTRACT FROM AUTHOR]

• Techno-economic analysis of low-carbon heat supply options for UK supermarkets. • RIHC, an ASHP, and a thermal storage tank with advanced control is recommended. • Best investments provide a 16-to-18-year payback without a carbon price. • The UK renewable heat incentive subsidy (for ASHP) generates 89% of the 'savings' • When a £100/tCO2e tax is considered, paybacks are reduced to a 9–11 years. Eliminating the use of natural gas for non-domestic heat supply is an imperative component of net-zero targets. Techno-economic analyses of competing options for low-carbon heat supply are essential for decision makers developing decarbonisation strategies. This paper investigates the impact various heat supply configurations can have in UK supermarkets by using heat recovery principles from refrigeration systems under different climatic conditions. The methodology builds upon a steady-state model that has been validated in previous studies. All refrigeration integrated heating and cooling (RIHC) systems employ CO 2 booster refrigeration to recover heat and provide space heating alongside various technologies such as thermal storage, air-source heat pumps (ASHPs) and direct electric heaters. Seven cases evaluating various technology combinations are analysed and compared against a conventional scenario in which the building is heated with a natural gas boiler. The specific combinations of technologies analysed here contrasts trade-offs and is a first in the literature. The capital costs of these projects are considered, giving insights into their business case. Results indicate that electric heaters are not cost-competitive in supermarkets. Meanwhile, RIHC and ASHP configurations are the most attractive option, and if a thermal storage tank system with advanced controls is included, the benefits increase even further. Best solutions have a 6.3% ROI, a payback time of 16 years while reducing energy demand by 62% and CO 2 emissions by 54%. Such investments will be difficult to justify unless policy steers decision makers through incentives or the business case changes by implementing internal carbon pricing. [ABSTRACT FROM AUTHOR]

Abstract: An archetypal simulation model of office building representing variability in UK office building stock by parameterising built form, construction elements, occupancy/usage and operational/control strategy has been developed thus enabling detailed energy performance simulation to be used for stock modelling and parametric studies. The paper discusses the building characteristics needed to be considered for energy performance simulation, their values, and how they can be used in parametric studies. These parameters include built forms, fabrics (including thermal mass and insulation positioning), glazing percentages and characteristics, daylight and solar control measures and activity and operational related parameters (heating and cooling set points, ventilation rate, occupancy density and metabolic rate, equipment and lighting gain). The default parameter values suggested for the archetypal simulation model reflect typical existing and currently proposed UK office building stock. An archetypal model, combined with parametric studies, can be used in assessing energy performance of building stock and evaluating adaptation/retrofitting strategies. [Copyright &y& Elsevier]

Abstract: The Low Carbon Futures project, funded by the Adaptation and Resilience in a Changing Climate (ARCC) Programme, has the objective of using the latest UK climate projections (UKCP’09) to assess overheating in a range of domestic and non-domestic buildings. As these climate projections are probabilistic in nature, and dynamic building simulation is being used by the project to assess building performance, the information produced is vast. To understand how to filter this data into a useable tool that can interact with current building practices, the project has commissioned a range of focus groups to obtain practitioner feedback. These focus groups provide guidance on how buildings are currently designed with respect to overheating but also how future overheating risk assessments, incorporating probabilistic climate projections, might be carried out. This paper describes the assimilation of all this research into a coherent building simulation methodology that could be used by building practitioners to assess future overheating risks of a range of buildings, and provide guidance for applying adaptation solutions to prevent defined comfort thresholds being exceeded. [Copyright &y& Elsevier]

Abstract: This paper examines the efficiency (in terms of energy use and carbon emissions) with which 5 different types of domestic water heating systems employed in the UK are able to produce hot water for sanitary use. A method of normalisation is employed allowing results from case studies with different systems and usage levels to be compared. Water heating appliances studied include gas boilers, a micro CHP, heat pumps, an immersion heater, and a solar thermal system. It is found that instantaneous production of hot water is much more efficient than delivery via tank storage for gas-fuelled systems. For electrical systems, an immersion heater is found to perform better in some circumstances than heat pumps and also has advantages when combined with a solar thermal system leading to the proposal that this combination offers the most potential as a low carbon method for domestic hot water provision in the long term. Opportunities are identified to improve the performance of all systems with storage through better control of heat inputs. Inconsistencies in, and problems of compliance with, established standards for mitigation of Legionella in hot water systems are also identified. [Copyright &y& Elsevier]

Abstract: Green roofs are a passive cooling technique that stop incoming solar radiation from reaching the building structure below. Many studies have been conducted over the past 10 years to consider the potential building energy benefits of green roofs and shown that they can offer benefits in winter heating reduction as well as summer cooling. This paper reviews the current literature and highlights the situations in which the greatest building energy savings can be made. Older buildings with poor existing insulation are deemed to benefit most from a green roof as current building regulations require such high levels of insulation that green roofs are seen to hardly affect annual building energy consumption. As over half of the existing UK building stock was built before any roof insulation was required, it is older buildings that will benefit most from green roofs. The case for retrofitting existing buildings is therefore reviewed and it is found there is strong potential for green roof retrofit in the UK. [ABSTRACT FROM AUTHOR]

Abstract: Possible solutions for zero energy building design in UK are discussed in this paper. Simulation software (EnergyPlus and TRNSYS 16) are employed in this study, where EnergyPlus simulations are applied to enable facade design studies considering building materials, window sizes and orientations and TRNSYS is used for the investigation of the feasibility of zero energy houses with renewable electricity, solar hot water system and energy efficient heating systems under Cardiff weather conditions. Various design methods are compared and optimal design strategies for typical homes and energy systems are provided. [Copyright &y& Elsevier]

Abstract: There are varieties of physical and behavioral factors to determine energy demand load profile. The attainment of the optimum mix of measures and renewable energy system deployment requires a simple method suitable for using at the early design stage. A simple method of formulating load profile (SMLP) for UK domestic buildings has been presented in this paper. Domestic space heating load profile for different types of houses have been produced using thermal dynamic model which has been developed using thermal resistant network method. The daily breakdown energy demand load profile of appliance, domestic hot water and space heating can be predicted using this method. The method can produce daily load profile from individual house to urban community. It is suitable to be used at Renewable energy system strategic design stage. [Copyright &y& Elsevier]