̽��ֱ�� of Cambridge - energy-efficient

New type of computer memory could greatly reduce energy use and improve performance

sc604 — Fri, 23 Jun 2023 13:58:55 +0000

̽��ֱ��researchers, led by the ̽��ֱ�� of Cambridge, developed a device that processes data in a similar way as the synapses in the human brain. ̽��ֱ��devices are based on hafnium oxide, a material already used in the semiconductor industry, and tiny self-assembled barriers, which can be raised or lowered to allow electrons to pass.

This method of changing the electrical resistance in computer memory devices, and allowing information processing and memory to exist in the same place, could lead to the development of computer memory devices with far greater density, higher performance and lower energy consumption. ̽��ֱ��results are reported in the journal Science Advances.

Our data-hungry world has led to a ballooning of energy demands, making it ever more difficult to reduce carbon emissions. Within the next few years, artificial intelligence, internet usage, algorithms and other data-driven technologies are expected to consume more than 30% of global electricity.

“To a large extent, this explosion in energy demands is due to shortcomings of current computer memory technologies,” said first author Dr Markus Hellenbrand, from Cambridge’s Department of Materials Science and Metallurgy. “In conventional computing, there’s memory on one side and processing on the other, and data is shuffled back between the two, which takes both energy and time.”

One potential solution to the problem of inefficient computer memory is a new type of technology known as resistive switching memory. Conventional memory devices are capable of two states: one or zero. A functioning resistive switching memory device however, would be capable of a continuous range of states – computer memory devices based on this principle would be capable of far greater density and speed.

“A typical USB stick based on continuous range would be able to hold between ten and 100 times more information, for example,” said Hellenbrand.

Hellenbrand and his colleagues developed a prototype device based on hafnium oxide, an insulating material that is already used in the semiconductor industry. ̽��ֱ��issue with using this material for resistive switching memory applications is known as the uniformity problem. At the atomic level, hafnium oxide has no structure, with the hafnium and oxygen atoms randomly mixed, making it challenging to use for memory applications.

However, the researchers found that by adding barium to thin films of hafnium oxide, some unusual structures started to form, perpendicular to the hafnium oxide plane, in the composite material.

These vertical barium-rich ‘bridges’ are highly structured, and allow electrons to pass through, while the surrounding hafnium oxide remains unstructured. At the point where these bridges meet the device contacts, an energy barrier was created, which electrons can cross. ̽��ֱ��researchers were able to control the height of this barrier, which in turn changes the electrical resistance of the composite material.

“This allows multiple states to exist in the material, unlike conventional memory which has only two states,” said Hellenbrand.

Unlike other composite materials, which require expensive high-temperature manufacturing methods, these hafnium oxide composites self-assemble at low temperatures. ̽��ֱ��composite material showed high levels of performance and uniformity, making them highly promising for next-generation memory applications.

A patent on the technology has been filed by Cambridge Enterprise, the ̽��ֱ��’s commercialisation arm.

“What’s really exciting about these materials is they can work like a synapse in the brain: they can store and process information in the same place, like our brains can, making them highly promising for the rapidly growing AI and machine learning fields,” said Hellenbrand.

̽��ֱ��researchers are now working with industry to carry out larger feasibility studies on the materials, in order to understand more clearly how the high-performance structures form. Since hafnium oxide is a material already used in the semiconductor industry, the researchers say it would not be difficult to integrate into existing manufacturing processes.

̽��ֱ��research was supported in part by the U.S. National Science Foundation and the Engineering and Physical Sciences Research Council (EPSRC), part of UK Research and Innovation (UKRI).

Reference:
Markus Hellenbrand et al. ‘Thin-film design of amorphous hafnium oxide nanocomposites enabling strong interfacial resistive switching uniformity.’ Science Advances (2023). DOI: 10.1126/sciadv.adg1946

Researchers have developed a new design for computer memory that could both greatly improve performance and reduce the energy demands of internet and communications technologies, which are predicted to consume nearly a third of global electricity within the next ten years.

These materials can work like a synapse in the brain: they can store and process information in the same place, like our brains can

Markus Hellenbrand

Andriy Onufriyenko via Getty Images

Artificial intelligence brain

̽��ֱ��text in this work is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 4.0 International License. Images, including our videos, are Copyright © ̽��ֱ�� of Cambridge and licensors/contributors as identified. All rights reserved. We make our image and video content available in a number of ways – as here, on our main website under its Terms and conditions, and on a range of channels including social media that permit your use and sharing of our content under their respective Terms.

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New research will use space telescopes to monitor energy efficiency of buildings

sc604 — Mon, 07 Dec 2020 11:57:09 +0000

̽��ֱ��funding will support companies and universities with radical ideas for how we tackle climate change through earth observation or address satellite communications challenges, from providing greater connectivity to remote places to increasing the efficiency of our homes.

Dr Ian Parry from Cambridge’s Institute of Astronomy has been awarded funding for high-resolution thermal infrared space telescopes for monitoring the energy efficiency of buildings.

Thermal infrared (TIR) earth observation telescopes in low earth orbit can monitor the energy output of buildings. Parry and his collaborators will build and develop a prototype for the continuous alignment required for a space telescope, as well as developing end-user climate change cases for TIR telescope.

“This technology can give us a global health check to let us know if the world is on target to meet its carbon emissions targets. It also makes it clear who needs to act and what they have to do if the targets aren’t being met,” said Parry. “It’s a bit like trying to get someone to give up smoking. ̽��ֱ��person knows it's bad for them and they have good intentions and make promises, but they still fall short of what they need to do until they get a worrying wake-up call from a medical examination.”

Governments sign up to agreements but it’s the behaviour of organisations and individuals that will deliver – or not – the required actions. This technology will allow governments across the world, including our own, to deliver what was promised.

̽��ֱ��technology will identify anything bigger than about five metres across that is using large amounts of energy, such as buildings, houses, aircraft, ships or lorries.

“Normally I point my telescope at the stars but by pointing it at the Earth I can help address a really important issue,” said Parry.

“We want the UK to be a world leader in space technology which is why we are supporting our most ambitious innovators who are developing technologies to help solve some of our greatest challenges,” said Science Minister Amanda Solloway. “From slashing carbon emissions to protecting the UK’s critical services from harmful cyber-attacks, today’s funding will unshackle our most entrepreneurial space scientists so that they can transfer their revolutionary ideas into world class products and services, while helping to boost the UK economy.”

̽��ֱ��funding comes from the UK Space Agency’s National Space Innovation Programme (NSIP), which is the first UK fund dedicated to supporting the space sector’s development of innovations, allowing us to compete internationally on the world stage with other countries, like France and Germany, which have dedicated national funding for space.

Businesses, universities and research organisations were awarded co-funding for projects that will help the space sector create new high-skill jobs, while developing new skills and technologies on UK soil. Grants from the £15 million funding pot range from between £170,000 and £1.4 million per project.

“Space technologies have become deeply embedded in, and critical to, almost every aspect of our daily lives,” said Dr Graham Turnock, Chief Executive of the UK Space Agency. “With rapid technological innovation, space offers a broad and growing range of opportunities to support economic activity and protect the environment. From the satellites connecting our calls to the ones that tell us when to expect rain when we step outside, space technologies are fundamental to our day-to-day lives.Our space sector is constantly advancing and welcoming new ideas, and through this funding we are championing the best of this British innovation.”

In addition, £5 million of the programme funding has been set aside for international projects, which will focus on increasing exports and securing new inward investment, supporting UK science and the prosperity agenda by funding working relationships between world-leading researchers and institutions and developing space capabilities important to the UK's security interests.

̽��ֱ��UK space sector has grown by over 60% since 2010. ̽��ֱ��industry already supports £300 billion of UK economic activity through the use of satellite services and is expected to grow further as this new Government support unlocks commercial opportunities.

̽��ֱ��UK also remains a member of the European Space Agency. ESA membership allows the UK to cooperate in world-leading science on a global scale, enabling UK scientists and researchers access to a range of international research and development programmes.

A bold response to the world’s greatest challenge

̽��ֱ�� ̽��ֱ�� of Cambridge is building on its existing research and launching an ambitious new environment and climate change initiative. Cambridge Zero is not just about developing greener technologies. It will harness the full power of the ̽��ֱ��’s research and policy expertise, developing solutions that work for our lives, our society and our biosphere.

̽��ֱ�� ̽��ֱ�� of Cambridge is one of 21 organisations awarded a share of over £7 million in funding meant to put the UK at the forefront of the latest advances in space innovation.

Normally I point my telescope at the stars but by pointing it at the Earth I can help address a really important issue

Ian Parry

NASA

Gulf of Mexico from space

̽��ֱ��text in this work is licensed under a Creative Commons Attribution 4.0 International License. Images, including our videos, are Copyright © ̽��ֱ�� of Cambridge and licensors/contributors as identified. All rights reserved. We make our image and video content available in a number of ways – as here, on our main website under its Terms and conditions, and on a range of channels including social media that permit your use and sharing of our content under their respective Terms.

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New research aims to improve energy efficiency, cut carbon emissions and reduce costs

pbh25 — Thu, 07 Aug 2014 08:34:00 +0000

Against a world backdrop of increased concerns about energy security, price fluctuations and, of course, the need to address climate change, six new research projects that aim to gain a fuller understanding of how energy is managed in the country’s non-domestic buildings are launched today.

Funded with £3 million from the Engineering and Physical Sciences Research Council (EPSRC), on behalf of the Research Councils UK Energy Programme (RCUKEP), the research will address how to use technology, data and information, mathematics, law and sociology to create better energy strategies and behaviours in the public and private, non-domestic buildings stock.

Among the schemes being funded is a Cambridge project aimed at creating software which will help to reduce the uncertainty in modelling the energy management of a wide variety of buildings.

Non-domestic buildings such as offices, supermarkets, hospitals and factories account for approximately 18 per cent of UK carbon emissions and 13 per cent of final energy consumption.

By 2050, the total UK’s non-domestic floor area is expected to increase by 35 per cent, while 60 per cent of existing buildings will still be in use. This means that substantial retro-fitting is likely and planning what techniques to use to save energy, as well as how to implement change with the cooperation of building occupants, is going to be essential.

Professor Philip Nelson EPSRC’s Chief Executive said: “Improving energy efficiency is an important piece of the energy puzzle. Worldwide energy demand is rising, as are global temperatures and sea levels. We need to find smart solutions to how we use energy while improving the environment in which people have to work, rest or play. These projects will go a long way to help improve our understanding of what goes on in non-domestic buildings and add to the armoury at the disposal of those managing these facilities.”

̽��ֱ��new projects will be run at Imperial College London, ̽��ֱ�� of Cambridge, ̽��ֱ�� of Edinburgh, ̽��ֱ�� of Oxford, ̽��ֱ�� of Southampton and the ̽��ֱ�� of Strathclyde.

̽��ֱ��Cambridge project is called B-bem: ̽��ֱ��Bayesian building energy management Portal. ̽��ֱ��research team is led by Ruchi Choudhary (Department of Engineering) and includes Sebastian Macmillan (IDBE), Koen Steemers and Yeonsook Heo (Department of Architecture), and Michael Pollitt (Cambridge Judge Business School).

Cambridge project is among those benefiting from £3 million Engineering and Physical Sciences Research Council (EPSRC) funding.

Improving energy efficiency is an important piece of the energy puzzle.

Professor Philip Nelson EPSRC’s Chief Executive

Phil Guest

Overlooking the Thames

More information:

̽��ֱ��Engineering and Physical Sciences Research Council (EPSRC) is the UK's main agency for funding research in engineering and physical sciences. EPSRC invests around £800m a year in research and postgraduate training, to help the nation handle the next generation of technological change. ̽��ֱ��areas covered range from information technology to structural engineering, and mathematics to materials science. This research forms the basis for future economic development in the UK and improvements for everyone's health, lifestyle and culture. EPSRC works alongside other Research Councils with responsibility for other areas of research. ̽��ֱ��Research Councils work collectively on issues of common concern via Research Councils UK.
̽��ֱ��Research Councils UK (RCUK) Energy Programme led by EPSRC aims to position the UK to meet its energy and environmental targets and policy goals through world-class research and training. ̽��ֱ��Energy programme is investing more than £625 million in research and skills to pioneer a low carbon future. This builds on an investment of £839 million over the past eight years. ̽��ֱ��Energy Programme brings together the work of EPSRC and that of the Biotechnology and Biological Sciences Research Council (BBSRC), the Economic and Social Research Council (ESRC), the Natural Environment Research Council (NERC), and the Science and Technology Facilities Council (STFC).

̽��ֱ��text in this work is licensed under a Creative Commons Licence. If you use this content on your site please link back to this page. For image rights, please see the credits associated with each individual image.

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When building for the future means what it says

sj387 — Fri, 18 Oct 2013 09:13:47 +0000

When the Victorian domestic housing boom kicked off in the 19th century, the designers, developers and inhabitants of the new terraces that sprung up across the country would probably have paid scant attention to the impact of housing on the environment over the long-term. Today, with approximately 40% of the nation’s buildings built before 1944, the UK has one of the oldest and least efficient domestic stocks in Europe, accounting for around 25% of its carbon emissions.

But, with new buildings, a very different scenario is fast approaching. According to government proposals, by 2016 all new homes will have to achieve a zero-carbon status. Buildings of the future should be low-energy, sustainable and able to respond to future changes – climatic, technological, social or regulatory – in other words, be ‘future proofed’.

This represents a significant shift for the building and construction sectors, as engineer Maria-Christina Georgiadou explained: “Much of the industry is based on a philosophy of ‘build-it-now and fix-it-later’ rather than on one of anticipating future trends and drivers affecting the energy performance of buildings.

“Added to this, there is conceptual confusion on what is ‘future-proofing’ in policy making, industry and academia. Little research has been carried out on identifying design approaches that adopt a long-term perspective in the context of the energy design of housing developments.”

For the past three years, Georgiadou has been working in the Centre for Sustainable Development, part of Cambridge’s Department of Engineering, with Dr Theo Hacking and Professor Peter Guthrie to examine the design approaches available to building professionals for integrating future-proofing into the energy design of housing developments.

Although a portfolio of methods is available, Georgiadou concludes that many “underestimate or even overlook the social and economic aspects of sustainability”, and identifies a need for design strategies that will proactively manage future trends and drivers affecting the energy performance of buildings. Her aim is to propose unified guidelines.

Georgiadou has been following four ‘best-practice’ housing developments in the UK and Sweden – North West Cambridge (Cambridgeshire), West Carclaze and Baal (Cornwall), Välle Broar (Växjö) and Hammarby Sjöstad (Stockholm) – interviewing city officers, planners, developers, contractors and members of design teams involved in the energy design process.

“There was a clear difference in the approach taken in Sweden and the UK to sustainability, in general, and future-proofing, in particular,” she noted. “In Sweden the concept of ‘life cycle thinking’ emerged on the back of the 1970s oil crisis, when the municipalities sought to find alternatives to oil and switched to local wood waste, such as wood chips and sawdust. From this early on, they had environmental planning in mind, tending to construct in timber, which they have in abundance and is a sustainable material with potential for reuse and recycling at the end of the house’s life compared to concrete. Building professionals in Sweden are also familiar with Lifecycle Assessment tools used to assess the environmental impact of building solutions from ‘cradle to grave’.”

On the other hand, she finds that developments in the UK place greater emphasis on accommodating risks and uncertainties “so that the design can be resilient to the occurrence of high-impact events such as hotter summers due to climate change. ̽��ֱ��UK planning system and energy policy is focused on flexibility and adaptability, which cascades down into the design of buildings,” she added.

But which approach is best for thinking about the future of residential buildings? “ ̽��ֱ��best case is a combination of both,” said Georgiadou, whose research is funded by the Engineering and Physical Sciences Research Council and the Alexander S. Onassis Public Benefit Foundation in Greece.

“Buildings are already being designed and constructed to use less energy and reduce carbon emissions, but long-term future-proofing to climate change is still in its infancy,” she added. “My research has identified the lack of a robust evidence-based framework as to how buildings can be future-proofed in terms of the selection of energy-related design responses right from the earliest stages of the project’s lifespan.”

To encourage a long-term view of the sustainability of buildings, the UK government has adopted the Government Soft Landings (GSL) scheme, which will be mandatory by 2016. “With GSL, the designers and constructors are required to monitor the buildings once built, to increase operational efficiency and understanding of the actual energy performance,” she explained. “This is in addition to the Code for Sustainable Homes, which is the tool by which the carbon rating of all new buildings is being measured.”

For the UK, Georgiadou believes one aspect of the solution is to build assessment criteria that explicitly promote a futures perspective into the Code for Sustainable Homes: “ ̽��ֱ��highest Code level aims for ‘zero carbon’ dwellings. However, fieldwork in the two UK cases revealed that this target may be hampered by the failure to consider the full lifecycle of the selected materials, building components and energy systems.”

She has now created a ‘knowledge map’ that can be used in any decision-support context for the energy design of residential buildings, with the potential to be expanded to cover other building types (such as offices, commercial, retail) as well as integration with other areas including water and waste management.

Evidence also shows that the focus of new buildings was predominantly on energy-efficiency measures and mitigation of carbon emissions now – what Georgiadou refers to as the “low hanging fruit” – and not on the adoption of adaptation strategies to address the increasing frequency and severity of temperature extremes that may lead to overheating of homes in the future.

“It’s the ability to respond to upcoming changes that defines future-proofing,” said Georgiadou. “This must be at the heart of strengthening building codes and energy-related standards at the start of the energy design process if we are to increase the likelihood of dwellings remaining ‘fit for purpose’ under a set of plausible energy futures. This would be a shift away from the short-term mindset that still dominates design and construction practices.”

For more information, please contact the Centre for Sustainable Development.

Too little attention is being paid to the long-term sustainability of new buildings in a changing climate according to a new study that makes recommendations for ‘future-proofing’ best practice.

It’s the ability to respond to upcoming changes that defines future-proofing

Maria-Christina Georgiadou

Kevin Dooley

Crane

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Water waste! Manufacturers look to go green

amb94 — Mon, 22 Jul 2013 10:44:38 +0000

Imagine the changes required to transform a car factory into a place in which not one single kilogram of landfill waste is produced, and you are some way to understanding what is it the Next Manufacturing Revolution (NMR), a not for profit initiative comprising academics, strategy and enterprise experts, is hoping to achieve.

In the UK manufacturing industry, improvements to the workforce have already reduced costs and improved efficiency at a rate of 3% per annum since 2001, but so far the efficient use of materials, water and energy has been slower to follow suit. In the NMR’s new report, academics from the Department of Engineering’s Institute for Manufacturing (IfM) have collaborated with industrial partners to give practical advice on how the manufacturing sector in the UK can clean up its act, and boost its profits.

“We are very excited about the launch of NMR’s report and the beginning of its programme to drive forward greater efficiencies, and in turn productivity, profits and jobs, in the manufacturing sector”, says report co-author Professor Steve Evans of the ̽��ֱ�� of Cambridge. “ ̽��ֱ��changes that NMR’s programme advocates use proven technologies and have already been implemented by pioneering companies. In many cases actions are straightforward and will deliver quick returns.”

̽��ֱ��report and subsequent programme claims it can help deliver significant benefits to the sector, including £10 billion per annum in additional profits and a 4.5% reduction in the UK’s total annual greenhouse gas emissions. It focuses on seven key areas including waste, energy, packaging and supply chain collaboration. These areas have been analysed within each of the manufacturing sub-sectors making it one of the most comprehensive analyses of resource management in UK manufacturing to date.

“I welcome this report for the important issues it raises around sustainable manufacturing and the range of opportunities it identifies for UK industry to improve its productivity through more efficient use of resources,” said ̽��ֱ��Rt Hon Dr Vince Cable, Secretary of State for Business, Innovation and Skills. “It fits neatly with my objective of strengthening the manufacturing sector in a forward looking and sustainable manner. There are many companies cited in the report as best practice leaders, and I am very supportive of its efforts to encourage the rest of UK manufacturing to follow their lead.”

̽��ֱ��NMR launched its new programme at a high profile event attended by Government, companies and NGOs at the House of Commons last week.

Established in 2012, NMR is a not-for-profit initiative founded by strategy advisors Lavery/Pennell, the ̽��ֱ�� of Cambridge’s Institute for Manufacturing, and business community experts 2degrees. Its objective is to unlock significant performance improvement in the manufacturing sector working with manufacturers, government, policy makers and relevant NGOs.

For a full copy of the report and further details on NMR’s programme is available please visit: http://www.nextmanufacturingrevolution.org

Programme launched to revolutionise green credentials of UK manufacturing

In many cases actions are straightforward and will deliver quick returns

Professor Steve Evans

Roberto Bouza on flickr

Green lego

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Energy efficiency and human behaviour

tdk25 — Mon, 18 Feb 2013 15:30:11 +0000

Improving the energy efficiency of the UK’s existing building stock is vital to meeting the UK’s climate change mitigation targets. Currently at least 30% of all end use Green House Gas (GHG) emissions are from the UK residential sector. If the UK is going to meet its legally binding target of 80% reduction in GHG emissions by 2050 from 1990 levels, emissions from the UK residential sector will have to be eliminated almost entirely.

This means the ‘right’ mix of policies, technologies and behavioural changes with the greatest potential for emissions abatement is crucial. However, this is much more complicated than it appears at first sight. New research from the ̽��ֱ�� of Cambridge has started to highlight the importance of understanding how the interaction between energy efficiency technologies, socio-demographic characteristics, environmental conditions and human behaviour all combine in unique ways to create very different carbon mitigation opportunities for each dwelling. Therefore, maximising the potential for carbon mitigation requires much deeper understanding for how different factors interact for each dwelling.

Recent studies have shown that human behaviour is at least as important as the physical characteristics of a building in influencing energy use, and that carbon emissions from dwellings are most sensitive to internal temperature changes, largely dependent on human behaviour. By understanding the interaction between human behaviour and the physical variables of buildings they occupy, we can untangle the complex relationships affecting energy use and get a clearer idea where energy and emissions savings can be made.

Predicting the impact that human behaviour and energy efficiency measures may have on residential energy consumption is complex. Energy consumption is affected by the income, age group, lifestyle and behaviour of occupants as well as the physical characteristics of dwellings and the environment where the building is located. As dwellings are non-homogenous, maximising emissions reductions for each dwelling can only be achieved with knowledge of how the combination of variables of the buildings physical material, environment and behaviour of its occupants all come together uniquely.

There is good evidence to show that improving building efficiency will lower energy expenditure and therefore emissions, even after the “rebound effect” is accounted for where energy savings achieved through energy efficiency measures are “taken back” as higher internal temperature or increased plug load . Although model estimates including the rebound effect suggest overall energy demand will decrease, the level of reduction will vary for different income groups and building efficiency levels.

For my PhD research in the Cambridge Centre for Climate Change Mitigation Research (4CMR) I developed a building stock model of the UK residential sector and made several important innovations on existing methods. ̽��ֱ��most important innovation is the inclusion of human behaviour, income, age-group, lifestyle and environmental factors down to the dwelling level. With this new model it is possible to estimate the level of emissions reductions that can be made from very specific subsectors within the building stock. As an example, it is now possible to estimate the level of energy and emissions reductions possible by improving the loft insulation in all end-terrace dwellings belonging to people aged over 65.

My research shows there is an equivalent, opposite effect to the rebound effect; that the building’s propensity for energy use affects the overall efficiency of a building; people living in a building with high energy bills are motivated to install energy efficiency measures and save money – the more money saved the more that is available to be spent on energy efficiency measures. My research suggests that dwellings that consume less energy have poorer energy efficiency, but homes that consume more energy have higher energy efficiency. Following the law of diminishing returns, buildings that are already more energy efficient are more expensive to make more efficient because the majority of low cost energy savings have already been adopted. For these homes the most effective strategy for reducing energy and emissions will be to change the energy consuming behaviour of occupants.

On the other hand, homes that consume less energy are less energy efficient when compared to the rest of the building stock and benefit from improvements in energy efficiency measures such as improved loft and wall insulation, triple glazing and improvements to the energy efficiency of heating systems. Unfortunately these homes are also the most susceptible to the rebound effect reducing the expected energy savings. However improvements to energy efficiency in these dwellings will lower the overall cost of energy and therefore lead to a reduction in fuel poverty. In addition warmer and less draughty dwellings improve the health of those belonging to the lowest income groups and thus lower the overall cost of health care for all UK taxpayers.

In summary, in order to meet future emissions reduction targets the question should not be about the role of either energy efficiency or human behaviour within the building stock. Rather, it is important to recognise that dwellings are heterogeneous and therefore a decarbonisation strategy that works well for one dwelling may not work for another. It is the complex interaction of variables occurring at the dwelling level that ultimately determines the optimal carbon mitigation solution. Policy instruments therefore need to reflect the diversity within the building stock so that emissions reductions can be maximised across the building stock.

Scott Kelly is a research associate in the Cambridge Centre for Climate Change Mitigation Research.

Are buildings that consume less energy really more energy efficient as a result? As the ̽��ֱ�� of Cambridge begins Switch Off Week, researcher Scott Kelly explains how predicting energy efficiency is easier said than done, especially once human behaviour becomes part of the calculation.

Dwellings are heterogeneous. A decarbonisation strategy that works well for one may not work for another.

Scott Kelly

Passivhaus Institut via Wikimedia Commons.

Thermogram of a Passivhaus with a traditional house in the background.

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̽��ֱ��prebound effect

bjb42 — Tue, 03 Jul 2012 00:01:06 +0000

Many European households are consuming less energy than predicted, especially in supposedly energy-inefficient homes, a new study has found.

̽��ֱ��research identified a recurring gulf between the quantity of energy predicted by governments for different types of housing and the amount homeowners actually use.

Researchers also found that the discrepancy was greatest among the least energy-efficient homes, where householders appear to be consuming far less than national energy usage standards predict.

This phenomenon is branded the “prebound effect” in the study, which is published in the new issue of the journal Building Research and Information. ( ̽��ֱ��term refers to the earlier identification of a “rebound effect”, in which people who have already had energy-saving initiatives such as thermal retrofits implemented in their home then use more energy, reducing the amount of energy actually saved).

Conversely, the “prebound effect” suggests that politicians and policy-makers who want to see more such initiatives in a wider range of homes may be over-estimating the benefits, and the rate of pay-back, because their judgements about how much energy those homes consume are already exaggerated.

Dr Minna Sunikka-Blank, from the Department of Architecture at the ̽��ֱ�� of Cambridge, who co-authored the study, said: “In general, the worse a home is thermally, the more the occupants tend to control the amount of heating they use. For financial reasons, they also have to. This challenges the prevailing view that large cuts in energy consumption can be achieved by focusing purely on technical solutions, such as retrofitting homes. In some cases, doing so may bring only half the expected savings, perhaps less.”

̽��ֱ��study focused on data from Germany, although it then found similar patterns in several other European countries including the United Kingdom. Germany has a rigorous thermal retrofitting programme which has been seen as a leading model for other European states.

At the heart of this model is the use of the Energiekennwert, or energy performance rating (EPR), which is a figure used by German policy-makers to predict the energy consumption of a given type of dwelling based on the thermal quality of the building, the heating system and the location. This is used to predict not only the amount of energy consumed, but the amount that might be saved with improved insulation, for example, as the result of a thermal retrofit.

Sunikka-Blank and her colleague, Dr Ray Galvin, used EPR and energy use data for 3,400 dwellings in Germany, to model the difference between predicted energy consumption and the amount of energy actually being consumed. Most of the measured figures came from meters in people’s homes. In addition, the research drew on background data about the physical character and energy consumption of a further 1 million properties.

̽��ֱ��model revealed clear discrepancies between calculated and measured energy consumption. Even when comparing homes that fell into the same predicted energy bracket, cases were found where one house used six times as much energy as another.

Critically, however, the study revealed a gulf between the predicted energy consumption for heating and the amount actually measured. ̽��ֱ��average EPR for a German dwelling was about 225 kilowatt hours per square metre, per year (kWh/m²a). Real energy consumption for heating averaged at around 150 kWh/m²a; a discrepancy of 30%.

When the discrepancies were plotted on a graph, they showed that overall, the higher the EPR (and therefore the lower the energy-efficiency of a house), the lower the relative measured energy consumption turned out to be. For example, the real average energy consumption of a home with an EPR of 300 kWh/m²a was about 40% below the calculated value, whereas that of a home with an EPR of 150 kWh/m²a was only 17% lower.

In practice, this means that many homes which are predicted to be highly inefficient in terms of the amount of energy they consume, are often consuming nowhere near as much energy in practice.

Comparison with further data, assembled by other researchers in different studies, revealed that similar patterns can be seen with homes in the United Kingdom, the Netherlands, Belgium and France.

In the UK, energy efficiency is predicted using a measured called the Standard Assessment Procedure (SAP), on a scale of 1-100, where 100 is the most efficient. Again, homes with a low SAP have been found to consume far less energy relative to their rating than those with a high SAP. As with the German example, the higher the predicted energy consumption, the lower the actual relative energy consumption seems to be.

̽��ֱ��study suggests that measures such as the German EPR may be based on flawed assumptions about important factors such as energy loss through ventilation, or standard indoor temperature. There may also be a discrepancy between the ways in which buildings are designed and how they are built in practice.

Fundamentally, however, the study indicates that predictive measures are failing to take into account the ways in which people actually heat their homes in practice. “It seems that many German households tend to keep their homes cooler, or heat fewer rooms in their home, or have their heating on for less time - or various combinations of these - than is assumed in their EPR calculations,” Sunikka-Blank said.

“As retrofits cannot save energy that is not actually being consumed, this has implications for the economic viability of thermal retrofits.”

̽��ֱ��study adds that further research is needed to explain the prebound effect, but hints that one reason may be budget-consciousness among families living in energy inefficient homes. This appeared to be borne out by interviews the researchers conducted with German householders.

̽��ֱ��full paper will be downloadable for free for a limited time from the journal website, http://dx.doi.org/10.1080/09613218.2012.690952

Many homes with poor energy efficiency are actually consuming far less energy than predicted, new research has found. ̽��ֱ��study has implications for national energy-saving policies and the economic viability of thermal retrofit programmes.

This challenges the prevailing view that large cuts in energy consumption can be achieved by focusing purely on technical solutions, such as retrofitting homes. In some cases, doing so may bring only half the expected savings, perhaps less.

Minna Sunikka-Blank

Wikimedia Commons.

Thermal image of two people standing outside a building. ̽��ֱ��study found that in many European countries, including the UK, predicted energy usage in homes bears little resemblance to the amount used in practice.

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