Forecasting how residential urban form affects the regional carbon savings and costs of retrofitting and decentralized energy supply

Significance Statement

Hargreaves et al. (2016) developed a method of taking into account the variability of indoor and outdoor space of housing when forecasting the suitability of decentralized energy technologies. The research, published in the journal Applied Energy, substantially improves the spatial estimates of thermal energy consumption when compared to building energy models that use standard dwelling typologies.  It also forecast how spatial planning scenarios would affect the suitability of decentralised energy supply.

The United Kingdom Future of Heating report by the government Department of Energy and Climate Change (DECC) proposed that decentralized energy supply, such as heat pumps and heat networks, will provide a large proportion of future domestic heating and make a substantial contribution to achieving future CO₂ reduction targets. However, the DECC consultation on a domestic renewable energy incentive scheme identified costs and uncertainty about whether properties have the space for installation as important barriers.  This leads to the need for the future built form characteristics and energy demands to be considered because they will affect the suitability of decentralized technologies and their uptake and cost effectiveness.

Research to carry out this investigation was part of a case study of London and its surrounding regions in the south east of England. It used urban modeling forecasts of the locations and average densities of dwellings for year 2031, and an innovative method of converting these densities into a representation of the housing stock and plot sizes. It thereby combined the regional simulation of urban form and building occupancies with the building-scale modelling of energy demand and supply to test combined scenarios for spatial planning policy, building regulations and technologies.

Dwelling energy demands were estimated using a Domestic Energy and Carbon Model (DECM) for predicting the energy consumption and carbon dioxide emission of the English housing stock. The decentralized energy supply options consisted of community-scale and building integrated technologies. Cost effectiveness was calculated as a relative measure against the most appropriate reference case and was used to explore the cost of achieving a one tonne reduction in CO₂ emissions compared with paying a carbon price of around £ 70/tonne. The future costs and efficiencies of buildings and technologies were based on information available in 2009.

From the results, Hargreaves et al. (2016) showed that lower density areas would have the greatest potential for energy efficiency improvement by retrofitting because they would have a greater proportion of less energy efficient dwelling types such as detached and semi-detached houses. These would also have more garden and roof space for low carbon technologies that could partly offset their greater CO₂ emissions. The integrated modeling framework showed how differences in the densities of dwellings due to spatial planning policies would affect their CO2 emissions and also the reduction in these emissions achievable by the energy supply systems.

The energy supply systems were selected based on the availability of suitable space, an initial estimate of their likely uptake, and sized with respect to their connected energy demand and operational characteristics.  The results obtained show that the decentralized energy supply technologies would make only a marginal reduction in CO₂ per capita for the case study regions in the forecast year of 2031 compared to conventional supply.

The UK has a policy to progressively de-carbonize the conventional energy supply and this will diminish the future CO₂ reduction benefits of these local low-carbon technologies.  None of the decentralized supply technologies tested, except micro-chp & gas, would be financially beneficial to households unless subsidized.  Also, the new-build dwellings would be much more energy efficient and so would have less potential for further reduction in CO₂ emissions by low carbon supply.

Hargreaves et al. 2016’s findings have helped to improve the evidence base for strategies on achieving carbon budgets and the results show that current strategies do not adequately take into account how future residential space constraints would affect the suitability of some of these decentralized technologies. Their future uptake is therefore likely to be lower than expected and is likely to decline unless there is continuing policy support. Also, they will become less cost effective at reducing CO₂ when compared to conventional supply unless there is continuing improvement in their performance and costs characteristics.

About The Author

Tony Hargreaves is a chartered civil engineer and has been a Senior Research Fellow at Birmingham University since 2015, and was previously a Senior Research Associate for 12 years at Cambridge University, UK.

His research explores the interdependencies between spatial planning and the suitability of decentralised infrastructure for energy, travel, water and waste.  This has integrated the regional modelling of land use and transport with the neighbourhood scale modelling of urban form to forecast how planning policies and technology scenarios could be combined to improve the sustainability and resilience of cities. 

About The Author

Dr. Vicky Cheng is the leader of the Energy Efficient and Smart Cities research group at the Munich School of Engineering, Technische Universität München, Germany. Prior to joining TU München, Vicky worked as a post-doctoral researcher in the Department of Architecture, University of Cambridge where she obtained her PhD. As well as academic research, Vicky has served as an Associate in Cambridge Architectural Research Ltd. with whom she has worked on consultancy projects for the UK and Scottish governments in the topic of housing energy.

Vicky’s research is centred on urban energy system modelling and analysis, particularly in the area of energy system optimisation, heat and electricity sector coupling and integration of renewable energy technologies. 

About The Author

Sandip Deshmukh is Associate Professor of Mechanical Engineering, BITS Pilani–Hyderabad Campus, India.  Sandip is associated with BITS Pilani in various capacities from last thirteen years. He has also worked for four years as a Research Fellow on EPSRC funded projects at the Centre for Environmental Strategy, University of Surrey, Guildford, UK.

His main research interest relate to regional energy planning with a focus on decentralized energy supply options and energy resource allocation for socio-economic and techno-economic development. 

About The Author

Matthew Leach is Professor of Energy and Environmental Systems at University of Surrey, UK.  Matthew is part of the multidisciplinary Centre for Environment and Sustainability, where he recently completed six years as Centre Director. He is a chartered mechanical engineer, with an MSc and PhD in Energy Policy from Imperial College London. He has previously been Vice President of the Energy Institute and Chair of Council of the British Institute of Energy Economics.

Matthew has thirty years’ experience of the challenges in delivering secure and sustainable energy services. His research has focussed on decentralised energy supply systems and the role of demand-side management, exploring the environmental and economic performance of emerging technologies, and the roles for policy, in long term transitions to a low carbon economy. 

About The Author

Koen Steemers is Professor of Sustainable Design at the Department of Architecture, University of Cambridge. There he has been Head of Department (2008-14) and Head of Research as Director of the Martin Centre (2003-08).

An architect and environmental design specialist, Koen was listed as one of the “top 50 most influential people in UK sustainability” by Building Design. His current work deals with the architectural and urban implications of environmental issues ranging from energy use to human well-being. Koen is a member of energy, environment and health networks and has been developing cross-disciplinary research initiatives.

Koen’s research activities are focused on the environmental performance of buildings and cities – with a particular interest in human perception and behaviour – which are the topics of funded research projects and his 35 past and present PhD students.

Koen has over 200 outputs (with over 4600 citations), with 10 books including “Energy and Environment in Architecture” (2000), “Daylight Design of Buildings” (2002), “Environmental Diversity in Architecture” (2004) and “Sustainable Urban and Architectural Design” (2006). 

Journal Reference

Anthony Hargreaves¹ , Vicky Cheng², Sandip Deshmukh³, Matthew Leach⁴, Koen Steemers⁵. Forecasting How Residential Urban Form Affects the Regional Carbon Savings and Costs of Retrofitting and Decentralized Energy Supply.  Applied Energy, Volume 186, Part 3, 15 January 2017, Pages 549–561.