Geoffrey P. Hammond

Energy analysis and environmental life cycle assessment of a micro-wind turbine

The life cycle energy use and environmental impact of an installed micro-wind turbine for domestic (residential) electricity generation has been determined. The turbine examined was a horizontal-axis wind turbine, which has a rotor diameter of 1.7 m, a power rating of 600 W at 12 m/s, and an assumed lifetime of 15 years. The system boundaries for the study encompass energy and material resources in the ground and extend to the point of delivery of electricity. The energy output of the turbine in different terrains has been estimated via a dataset of hourly measured wind speeds, and the environmental impact of producing and maintaining the micro-wind turbine was determined. The environmental performance of the turbine was assessed by assuming that each unit of electricity generated displaces (avoids the use of) a unit of grid electricity. The whole life cycle performance of a micro-wind turbine was found to be dependant on a number of factors, primarily the geographical positioning of the turbine, the available wind resource, and the use of recycled materials within the production of the microturbine.

Natural convective heat transfer rates in rectangular enclosures

An experimental study of buoyancy-driven convection in rectangular enclosures has been made in order to obtain convection coefficients and data correlations which are more accurate for real building situation. Three different flow regimes viz. stably-stratified flow, buoyancy-driven vertical flow and horizontal flow were investigated. The Nusselt number variation with respect to the Rayleigh number has been plotted and compared with existing correlations. In general, the measured data were lower than the data obtained from the existing correlations which are mainly derived from data obtained from experiments involving isolated surfaces.

Environmental and resource burdens associated with world biofuel production out to 2050: footprint components from carbon emissions and land use to waste arisings and water consumption.

Environmental or ‘ecological’ footprints have been widely used in recent years as indicators of resource consumption and waste absorption presented in terms of biologically productive land area [in global hectares (gha)] required per capita with prevailing technology. In contrast, ‘carbon footprints’ are the amount of carbon (or carbon dioxide equivalent) emissions for such activities in units of mass or weight (like kilograms per functional unit), but can be translated into a component of the environmental footprint (on a gha basis). The carbon and environmental footprints associated with the world production of liquid biofuels have been computed for the period 2010–2050. Estimates of future global biofuel production were adopted from the 2011 International Energy Agency (IEA) ‘technology roadmap’ for transport biofuels. This suggests that, although first generation biofuels will dominate the market up to 2020, advanced or second generation biofuels might constitute some 75% of biofuel production by 2050. The overall environmental footprint was estimated to be 0.29 billion (bn) gha in 2010 and is likely to grow to around 2.57 bn gha by 2050. It was then disaggregated into various components: bioproductive land, built land, carbon emissions, embodied energy, materials and waste, transport, and water consumption. This component‐based approach has enabled the examination of the Manufactured and Natural Capital elements of the ‘four capitals’ model of sustainability quite broadly, along with specific issues (such as the linkages associated with the so‐called energy–land–water nexus). Bioproductive land use was found to exhibit the largest footprint component (a 48% share in 2050), followed by the carbon footprint (23%), embodied energy (16%), and then the water footprint (9%). Footprint components related to built land, transport and waste arisings were all found to account for an insignificant proportion to the overall environmental footprint, together amounting to only about 2%

Thermodynamic efficiency of low-carbon domestic heating systems: heat pumps and micro-cogeneration

Energy and exergy analysis is employed to compare the relative thermodynamic performance of low-carbon domestic energy systems based on air source heat pumps and micro-combined heat and power (cogeneration) units. A wide range of current units are modelled under different operating conditions representative of the United Kingdom to determine the energy and exergy flows from primary energy inputs through to low-carbon heating system and then to end use. The resulting performances are then analysed in order to provide insights regarding the relative merits of the systems under the different operating constraints that may be experienced both now and into the future. Although current mid-range systems achieve comparable performance to a condensing gas boiler, the state-of-art offers considerable improvements. Micro-combined heat and power units and air source heat pumps have the technical potential to improve the energy performance of dwellings. The relative performance and potential of the systems is dominated by the electrical characteristics: the grid electrical generation efficiency, the power-to-heat demand ratio and the availability of electrical export. For total power-to-heat demands below 1:1.5, air source heat pumps have greater improvement potential as their energy efficiency is not constrained. At higher power-to-heat ratios, micro-combined heat and power units offer the potential for higher overall efficiency and this generally occurs irrespective of whether or not the thermal energy from them is used effectively.

Realising transition pathways for a more electric, low-carbon energy system in the United Kingdom: Challenges, insights and opportunities

The United Kingdom has placed itself on a transition towards a low-carbon economy and society, through the imposition of a legally-binding goal aimed at reducing its ‘greenhouse gas’ emissions by 80% by 2050 against a 1990 baseline. A set of three low-carbon, socio-technical transition pathways were developed and analysed via an innovative collaboration between engineers, social scientists and policy analysts. The pathways focus on the power sector, including the potential for increasing use of low-carbon electricity for heating and transport, within the context of critical European Union developments and policies. Their development started from narrative storylines regarding different governance framings, drawing on interviews and workshops with stakeholders and analysis of historical analogies. The quantified UK pathways were named Market Rules, Central Co-ordination and Thousand Flowers; each reflecting a dominant logic of governance arrangements. The aim of the present contribution was to use these pathways to explore what is needed to realise a transition that successfully addresses the so-called energy policy ‘trilemma,’ i.e. the simultaneous delivery of low carbon, secure and affordable energy services. Analytical tools were developed and applied to assess the technical feasibility, social acceptability, and environmental and economic impacts of the pathways. Technological and behavioural developments were examined, alongside appropriate governance structures and regulations for these low-carbon transition pathways, as well as the roles of key energy system ‘actors’ (both large and small). An assessment of the part that could possibly be played by future demand side response was also undertaken in order to understand the factors that drive energy demand and energy-using behaviour, and reflecting growing interest in demand side response for balancing a system with high proportions of renewable generation. A set of interacting and complementary engineering and techno-economic models or tools were then employed to analyse electricity network infrastructure investment and operational decisions to assist market design and option evaluation. This provided a basis for integrating the analysis within a whole systems framework of electricity system development, together with the evaluation of future economic benefits, costs and uncertainties. Finally, the energy and environmental performance of the different energy mixes were appraised on a ‘life-cycle’ basis to determine the greenhouse gas emissions and other ecological or health burdens associated with each of the three transition pathways. Here, the challenges, insights and opportunities that have been identified over the transition towards a low-carbon future in the United Kingdom are described with the purpose of providing a valuable evidence base for developers, policy makers and other stakeholders.

Risk assessment of UK biofuel developments within the rapidly evolving energy and transport sectors

A range of major risks associated with the production and use of biofuels in the rapidly changing United Kingdom (UK) energy and transport sectors have been identified and quantified. This was achieved with the aid of various stakeholder groups (academic researchers; industrialists; and a concatenated group of policy makers together with ‘green’ and international development groups), who completed an online internet questionnaire. Each stakeholder ranked 15 potential risks associated with the UK development and use of liquid biofuels according to their perceived ‘severity of impact’ and ‘likelihood of occurrence’ using a three-point scale. This data was then used to perform a ranking of the risks by multiplying scores for impact and occurrence. There was some variation between the different stakeholder groups, but the similar risks were ranked highly by each group. The overall ranking identified the main risks as being a lack of investor confidence in biofuel developments (the highest score); energy or fuel security issues; negative public perception of biofuels (equal second highest); increased food prices; high barriers to entry into the fuel market; and misdirected agricultural expansion or land use (equal fifth highest). Comments by the expert respondents also provide a qualitative evaluation of the present state of UK biofuel developments. The present trial illustrates the potential of using risk issues appraisal and ranking to evaluate developing risks to the UK biofuels landscape. Clearly such an exercise would need to be carried out periodically if it were to maintain its value to the biofuel-related industrial sector and other stakeholders, including policy makers.

Progress in Energy Demand Reduction - From Here to 2050 (Editorial)

Energy systems pervade industrial societies and weave a complex web of interactions that affect the daily lives of their citizens. Such societies face increasing pressures associated with the need for a rapid transition towards a low carbon dioxide and secure energy future at moderate cost (that is, one which is affordable or competitive). These three elements represent the so-called energy policy ‘trilemma’ (Hammond and Pearson, 2013). In terms of the first element, the British government established a legally binding target of reducing the nation’s carbon dioxide emissions overall by 80% by 2050 in comparison to a 1990 baseline (Climate Change Act 2008, 2008; DTI, 2007). That will be a very difficult task to achieve. Thus, the three elements of the ‘trilemma’ collectively present many challenges that will require a portfolio of energy options to surmount them: energy demand reduction and efficiency improvements, carbon dioxide capture and storage (CCS) from fossil fuel power plants and a switch to low or zero carbon dioxide energy sources (such as combined heat and power (CHP), nuclear power stations and renewable energy technologies on a large and small scale). The demand for energy, however, is the main driver of the whole energy system. It gives rise to the total amount of energy used, as well as the location, type of fuel and characteristics of specific end-use technologies. Consequently, the need for reductions in energy demand, and associated ‘greenhouse gas’ (GHG) emissions, applies across the end-use spectrum from the built environment to industrial processes and products, from materials to design, and from markets and regulation to individual and organisational behaviour. In order to analyse rigorously the energy and environmental consequences of changes in supply and demand of energy-intensive goods and services, it is necessary to take a holistic perspective (Hammond, 2000). This implies drawing the system boundary quite widely – across the ‘whole energy system’ or ‘fuel chain’ on a life-cycle basis. Such an approach is needed because of the complex interaction between sectors and their impacts during the transition to a ‘low carbon’ future. It is therefore important to trace the whole life of products, services and supporting infrastructure, and their associated energy flows and pollutant emissions, as they pass through the economy. A simplified model of energy flows in the UK is illustrated in Figure 1 (Hammond, 2000). It should be noted that heat is potentially wasted and energy is ‘lost’ at each stage of energy conversion, transmission and distribution, particularly in connection with the process of electricity generation. This schematic energy flow diagram hides many feedback loops in which primary energy sources (including fossil fuels, uranium ore and hydro-electric sites) and secondary derivatives (such as hydrogen fuel or nuclearand renewable-generated electricity) provide upstream energy inputs into the ‘energy transformation system’ (Slesser, 1978). The latter is that part of the economy where a raw energy resource is converted into useful energy which can meet downstream, ‘final’ or ‘end-use’ demand. ‘Renewable’ energy sources are taken to mean those that are ultimately solar-derived: mainly solar energy itself, biomass resources and wind power (Hammond, 2000).

The thermodynamic implications of electricity end-use for heat and power

Thermodynamic (energy and exergy) analysis can give rise to differing insights into the relative merits of the various end-uses of electricity for heat and power. The thermodynamic property known as ‘exergy’ reflects the ability to undertake ‘useful work’, but does not represent well heating processes within an energy sector. The end-use of electricity in the home, in the service sector, in industry, and the UK economy more generally has therefore been examined in order to estimate how much is used for heat and power, respectively. The share of electricity employed for heat and power applications has been studied, and alternative scenarios for the future development of the UK energy system were then used to evaluate the variation in heat/power share out to 2050. It was found that the proportion of electricity used to meet these end-use heat demands in the three sectors examined were likely to be quite high (∼50–60%), and that these shares are insensitive to the precise nature of the forward projections (forecasts, transition pathways or scenarios). The results represent a first indicative analysis of possible long-term trends in this heat/power share across the UK economy. Whilst the study is the first to consider this topic within such a timeframe, some of the necessary simplifying assumptions mean there are substantial uncertainties associated with the results. Where end-use heat demands are met by electricity, energy and exergy analysis should be performed in parallel in order to reflect the interrelated constraints imposed by the First and Second Laws of Thermodynamics. An understanding of the actual end-uses for electricity will also enable policy makers to take account of the implications of a greater end-use of electricity in the future.

Realising transition pathways to a low-carbon future (Editorial)

The evolution of modern industrialised society has been interwoven with discoveries of sources and uses of energy, especially the exploitation of fossil fuel resource stocks, the assembly of energy infrastructures, and the development of end-use technologies and practices. With its coal reserves, ports and engineering skills, Britain lay at the heart of the first industrial revolution. Nowadays, while energy supplies underpin continued economic development, this fossil fuel dependence exposes the UK to major risks: supply and resource insecurities; increasing costs of energy supply; and damage to the quality and longer term viability of the biosphere. The 2008 Climate Change Act aimed to establish an economically credible ‘greenhouse gas’ (GHG) emissions reduction pathway towards an 80% emissions reduction by 2050 against a 1990 baseline. It set legally binding mediumand long-term targets, as well as requiring intermediate carbon budgets. These GHG reductions will necessitate a radical transition towards an energy system that delivers high-quality energy services through low-carbon technologies and processes, whilst ensuring the provision of secure energy supplies at affordable prices: the so-called energy policy ‘trilemma’. There is clearly a need for urgent decisions and substantial investments in supply and demand-side options, against the risks of lock-in to technologies and institutions highlighted in the recent International Energy Agency (IEA) World Energy Outlook 2016. In this context, the UK Engineering and Physical Sciences Research Council (EPSRC) funded the nine-university multi-disciplinary Realising Transition Pathways (RTP) Consortium, under the auspices of the RCUK Energy Programme, over the period 2012–2016. It followed an initial Transition Pathways project (2008–2012), with essentially the same university collaborators, that was funded under a strategic partnership between E.ON UK and the EPSRC to undertake a whole systems analysis of the UK electricity sector. Thus, the RTP project built on the first project’s three socio-technical transition pathways, tools and approaches to analyse the challenges involved in realising a transition to a UK low-carbon electricity system in the context of wider European energy developments and policies. In constructing the three pathways, the project focused on aspects of governance. This approach sees a transition pathway arising through the interactions of three broad, highly aggregated types of governance ‘logics’ (state, market, civil society) and the shifting balances of agency between them and the actors who espouse them. These logics influence the framing of energy challenges and responses, including policy responses. The pathways were named Market Rules, Central Co-ordination and Thousand Flowers (TF) reflecting three alternative governance ‘logics’ (blue, red and green pathways, respectively). They were developed and analysed via an innovative collaboration between engineers, social scientists and policy analysts. Their research focused on the realisation of technologies, practices and choices that might ‘get there from here’ on the journey to 2050, and their behavioural, economic and environmental implications. It involved new studies of historical transition experience, strategic issues (including horizon scanning of medium-term technological developments on the supply-side, the network infrastructure and the demand-side), as well as network, market simulation and behavioural modelling, with ‘whole systems appraisal’ of key energy technologies and the full pathways, within a ‘sustainability framework’. This analysis sought to contribute to understand the future interplay of the energy policy ‘trilemma’: again, achieving deep GHG emission cuts, whilst maintaining a secure and affordable energy system and addressing how resulting tensions might be resolved.

The potential environmental consequences of shifts in UK energy policy that impact on electricity generation

Internationally, there has been a move by nations to decarbonise their electricity systems in an effort to tackle rising territorial emissions. No consensus has been fully reached on best approach, which has led to significant divergence in energy policy between countries and a consequential lack of long-term clarity. Additionally, recent UK policy failures, in terms of stimulating greater energy efficiency and encouraging energy innovation, highlight the huge challenge involved in developing and achieving a low carbon future. Steps to decarbonise electricity whilst also providing a secure and affordable supply, can lead to varying life-cycle environmental consequences. A UK research consortium developed three pathways to explore this move to a more electric low carbon future out to 2050. These pathways have been previously evaluated in terms of their life-cycle energy and environmental performance within a wider sustainability framework. Over the course of the project, greater understanding of the generation technologies and the functionality of the overall system under the different regimes were gained. Here, the environmental consequences of the most recent version of the pathways are presented on a life-cycle basis from ‘cradle-to-gate.’ Thus, the environmental impact of technological trends in UK energy policy and their effect on the pathways are explored through a series of sensitivity analyses. The three UK energy futures incorporating ‘disruptive’ technological options were examined based on the phase out of coal use in favour of gas-fired power, ranging penetration levels of carbon capture and storage, and the allocation and fuel type used for combined heat and power. Recommendations are proposed to help frame future energy policy choices in order to limit the environmental consequences of future electricity systems.