The role of experience curves for setting MEPS for appliances

Minimum efficiency performance standards (MEPS) are an important policy instrument to raise the efficiency of products. In most schemes the concept of life cycle costs (LCC) is used to guide setting the MEPS levels. Although a large body of literature shows that product cost is decreasing with increasing cumulative production, the experience curve, this is currently not used for setting MEPS. This article shows how to integrate the concept of the experience curve into LCC calculations for setting MEPS in the European Union and applies this to household laundry driers, refrigerator-freezers and televisions. The results indicate that for driers and refrigerator-freezers at least twice the energy savings compared to the current approach can be achieved. These products also show that energy label classes can successfully be used for setting MEPS. For televisions an experience curve is provided, showing a learning rate of 29%. However, television prices do not show a relation with energy efficiency but are to a large extent determined by the time the product is placed on the market. This suggests to policy makers that for televisions and other products with a short (re)design and market cycle timing is more important than the MEPS levels itself.     

LES of Impingement Heat Transfer on a Concave Surface

Wall-resolved and zonal numerical large eddy type simulations are performed for a round jet impinging on a concave hemisphere at Re = 23,000. The zonal method uses a near-wall k–l model and a Hamilton-Jacobi equation to match this to the large eddy simulation zone. To minimize numerical dissipation, a self-adaptive discretization (SDS) scheme is examined. Both second- (n = 2) and sixth- (n = 6) order-based central discretization schemes are tested. The characteristics of the schemes is assessed using two test cases: the development of a subcritical Tollmien-Schlichting (T-S) stability wave in a plane channel and the decay of homogenous, isotropic turbulence (DHIT). It is found, that Smagorinsky LES simulations tend to be too dissipative in the high wave-number region, even with the SDS scheme; hence, the SGS model is omitted. Significant flow feedback is observed for the hemisphere case. Both shear-layer excitation and stabilization is observed. Computed wall pressure coefficients for the zonal NLES method are encouraging; for the wall-resolved case the stagnation region value is overpredicted. Heat transfer for the wall-resolved and zonal large eddy simulations are encouraging. For both quantities the difference between the n = 2 and n = 6 schemes is small, and the modeling approach used appears to be more influential. It is concluded that the presence of feedback mechanisms should be considered when designing experiments and/or numerical simulations for this case, and that the importance of boundary conditions for LES should not be neglected.     

Dishwashing behaviour of European consumers with regard to the acceptance of long programme cycles

Since the introduction of the energy label for household dishwashers in the EU, manufacturers have been incentivised to reduce resource consumption and increase the energy efficiency of their appliances. Technological progress has led to very efficient programmes with cleaning cycles of 3 to 4 h or longer. The European Commission recently initiated a revision of the energy label and Ecodesign requirements, leading to their adjustment to the state of the art and to actual usage patterns. The University of Bonn was tasked with investigating dishwashing habits in Europe. An online survey was conducted in 11 countries of the EU with more than 5000 participants. The survey focused on the choice of programme, attitudes towards energy-saving programmes and practices and the willingness to apply them. It appears that consumers are willing to apply energy-saving practices and to use energy-saving programmes, but the acceptance of long cycles that take more than 2 h is low, which stands in contradiction to the fact that 19% of all dishwashing cycles are run in the Eco programme, which takes more than 2 h in most cases. The percentage of people who understand that long cycles can be energy-efficient is smaller than the percentage of those who do not believe this. The statements of the participants are contradictory regarding the importance of saving energy and of programme duration. The results of the survey point out the importance of better consumer education and better communication by manufacturers, consumer organisations and legislation.     

Energy savings potential of uninterruptible power supplies in European Union

Uninterruptible power supplies (UPS) are key components of information and communications technologies (ICT) systems, ensuring reliability by maintaining the continuity and quality of the systems’ power supply. The energy consumption of UPS should be an important consideration due to its high impact on the lifecycle costs, but in most applications of UPS, energy efficiency is not the most important issue, since the operational reliability of the ICT systems and the related security of data processing and storage are the major concerns. However, the conversion efficiency of UPS systems has been improving in recent years and high energy savings can be achieved with the adoption of new technologies without a reduction of the reliability levels. The Ecodesign Preparatory Study for UPS (Lot 27) aimed to identify and recommend ways to improve, at their design phase, the environmental performance of UPS in the European Union throughout their lifetime. This paper presents the work developed during the Preparatory Study for UPS focused on the technical analysis of the best available and not yet available technologies, as well as the potential energy savings that can be achieved. Several technologies were considered at component and product level. The main design options were then modelled, and the potential energy savings achievable with policy options focused on minimum efficiency performance standards and energy labelling were assessed, showing a potential for energy savings in European Union in 2025 of 11.4 TWh (65 % energy saving relative to predicted energy requirement of EU ICT system UPS based on current practice).     

Energy-efficient distribution transformers in Europe: impact of Ecodesign regulation

This paper assesses the impact of energy-efficient distribution transformers through the implementation of energy efficiency classes, as well as through mandatory standards that remove the worst transformers from the market. Energy-efficient distribution transformers can not only save about 1 % of all the electricity generated but can also save very large investments in power generation and transmission power systems. Technical solutions to reduce energy consumption of transformers are available, but the market penetration of high-efficient transformers is significantly lower than it could be. The paper analyses the main market and regulatory failures and identifies that the introduction of efficiency classes and minimum energy performance standards (MEPS) is the best way to foster energy performance in distribution transformers. Policies and measures supporting energy-efficient distribution transformers around the world are reviewed. The use of Ecodesign methodology do define possible transformer MEPS regulation is discussed for different types of distribution transformers, as well as the associated impacts. Sensitivity analysis in relation to key parameters (load factor and electricity prices) is analyzed. The energy saving potential and the environmental impacts are calculated until the year 2050 in the European Union, as well as at world level. The potential savings in the year 2050 represent about 35 TWh of electricity in Europe, equivalent to about four million tons of reduced CO₂ emissions. For the world, the estimated impact in 2050 is about 450 TWh equivalent to about 180 million tons of reduced CO₂ emissions.     

Capturing energy efficiency in European iron and steel production—comparing specific energy consumption and Malmquist productivity index

European iron and steel producers are working towards increased energy efficiency to meet requirements set by European policies such as the Energy Efficiency Directive. In this study, we show that the specific energy consumption (SEC), representing the iron and steel sector in the Odyssee energy efficiency index (ODEX)—the tool for policy evaluation recommended by the European Commission—is insufficient for capturing energy efficiency trends of European iron and steel production. European producers focus on niche markets, diversifying and specialising their set of products well beyond crude steel, which is the benchmark product for deriving the SEC. We compare the SEC with the more comprehensive Malmquist productivity index (MPI) methodology, which is calculated using data envelopment analysis (DEA) techniques. An evaluation of energy efficiency trends during 2000–2010 showed that the SEC overestimated energy efficiency improvements for European steel industries, while underestimating the improvements achieved by Swedish steel industries. A comparison between the SEC, the MPI/DEA approach, and energy intensity based on value added in the Swedish case provides further insight to the methodological differences between the approaches. We conclude that the approaches highlight different aspects of energy efficiency analyses and that the SEC is not sufficient for capturing the energy efficiency of steel industries.     

Numerical Simulation of Low NO x Combustion Technology in a 100 MWe Bituminous Coal-Fired Wall Boiler

Computational fluid dynamics (CFD) has been applied to evaluate two NO _x reducing schemes in a 100 MW_e per hour (p/h) boiler that uses double volute burners without over-fire-air (OFA). The new schemes involve: a) changing the double volute burners for centrally fuel rich (CFR) burners, and b) using the OFA system in conjunction with a). In analyzing the results of these two schemes, various conclusions were drawn: 1) gas temperatures and related rise rates in the central zone of burners were higher, O₂ and NO _x concentrations were lower; and 2) cross-sectional gas temperature distributions through the burner centers in scheme employing b) is higher than that of original furnace set-up, and lower than that of scheme employing a). Comparing the b) scheme with those of the a) scheme and the original set-up, which is 277 mg/m³ (at 6% O₂) at the furnace outlet, the peak value of NO _x concentration has decreased 571 mg/m³ (67.4%) and 436 mg/m³ (61.2%), respectively.     

一款通用汽油机的排放优化

随着美国EPA对19kW以下的通用小型火花点燃式汽油机第三阶段排放法规的实施,现有的通机要达到该标准通常采取的技术方案是对汽油机进行优化和增加催化器。这种方案虽然能达到标准要求,但是汽油机的制造成本增加较多,大大降低了产品在美国市场的竞争力。在这种情况下国内迫切需要能够在不增加或很少增加成本的条件下,达到美国EPA第三阶段排放要求的解决方案。通过对现有产品排量的提升、进排气道的改造、活塞组的改制、点火提前角的匹配等方案的实施,使该机型达到了美国EPA第三阶段的要求。采用的是最终验证结果,对于过程中的无效或影响较小的方案没有进行描述。     

Off-board regeneration of ammonia borane for use as a hydrogen carrier for automotive fuel cells

Ammonia borane (AB) is a promising chemical hydrogen storage material because of its high H₂ intrinsic material capacity and the exothermicity of the dehydrogenation reactions. A major technical barrier for AB, however, is in the development of an energy-efficient regeneration scheme. This paper examines three promising regeneration schemes that are in various stages of development and verification in the laboratory. The first scheme utilizes a thiol to digest the spent fuel and requires reforming formic acid to close the fuel cycle. The second scheme utilizes an alcohol to digest the spent fuel, but not all steps in the process have been formulated or tested. The third scheme is a single-reactor process that uses hydrazine to regenerate spent AB, but the production of hydrazine from hydrogen is itself not a trivial process. Engineering flowsheets were constructed for each of the three regeneration schemes and the process energy requirements for each scheme were calculated. Additionally, total energy requirements across the entire chain of production, delivery, storage, recovery, and regeneration were evaluated to determine the total cycle well-to-tank energy efficiency and greenhouse gas emissions. The well-to-tank efficiency ranges from a low of 8% in one version of the third regeneration scheme to as high as 37% in the second scheme if the missing process steps were to have no impact on efficiency. The estimated greenhouse gas emissions are between 20 and 100 kg CO₂-equivalent per kg H₂ delivered to the vehicle.     

Effect of jet schemes of the double-nozzle strut injector on mixing efficiency of air and hydrogen for a scramjet combustor

This work presents the numerical analysis of the DLR scramjet combustor for different jet schemes of the double-nozzle injector, namely the various injection directions, injection angles, and nozzle spacings. After comparing various jet schemes, it is found that the optimal jet scheme for the double-nozzle strut is to set the angle of 60° for the inward injection direction and the nozzle spacing of 3 mm. Furthermore, the mixing efficiency of the optimal jet scheme is investigated at different Mach numbers. The current research focuses on the mixing mechanism of air and hydrogen by analyzing the flow structures in the strut's wake region. It is observed that the double-nozzle configuration increases the number of vortexes behind the strut and creates a recirculation zone between the two jet streams. The mixing efficiency of the scramjet combustor improves significantly with an increase in the injection angle, but the spacing and direction of the double-nozzle have little effect on the mixing efficiency. It is found that the additional total pressure loss generated by the double-nozzle configuration can be negligible. In addition, the results show that the mixing efficiency of the optimal jet scheme for the double-nozzle is improved more significantly at low Mach numbers (e.g., Ma = 2 and 3).     

Implications of an energy efficiency obligation scheme for the Swedish energy-intensive industries: an evaluation of costs and benefits

The EU Energy Efficiency Directive (EED) aims at improving energy efficiency by implementing actions in all sectors of the economy in the EU. Article 7 of the EED sets the target of 1.5 % cumulative annual energy end-use savings. An energy efficiency obligation scheme (EEO) is one of the policy mechanisms proposed to reach this target. This paper assesses the impact of implementing a Swedish EEO and the implications that such a scheme may have for Swedish energy-intensive industries. The assessment was based on cost-benefit analysis (CBA) methodology. The benefit-to-cost ratio (BCR) ranges from 1.56 to 2.17 and the break-even cost ranges from 83.3 to 86.9 €/MWh with sensitivity analyses performed for the emission allowance prices and eventual costs of the EEO. The annual energy savings potential is estimated to be 1.25 TWh/year. A Swedish EEO could motivate investments in energy efficiency measures and thus help Sweden reach the energy efficiency targets set in the EED.     

A bibliometric analysis of recent energy efficiency literatures: an expanding and shifting focus

To meet the energy requirements of sustainable economic growth, policymakers, analysts, and business leaders have increasingly turned to the role that energy efficiency might play. This has resulted in a growing energy efficiency literature, which is examined in this paper. Using bibliometric techniques, we analyze the database of Science Citation Index Expanded and Social Sciences Citation Index covering the 1991–2010 period. Of the 8,244 publications, 78.8 % were journal articles, and about 95.5 % were published in English. Based on the h-index, an evaluative indicator, the USA has produced the most influential set of publications on energy efficiency, followed by Canada, UK, Japan, and China. In contrast, China is second to the USA in the volume of its publications. Correspondingly, the University of California at Berkeley, Chinese Academy of Sciences, and Tsinghua University were the most productive research organizations. The three most common subjects examined in this body of research were “energy and fuels”, “environmental sciences”, and “electrical and electronic engineering”. Energy Policy has been the most productive journal, and “A water and heat management model for proton-exchange-membrane fuel-cells”, has had the most citations (587 through May 2012). Based on an analysis of article titles and keywords, we conclude that the hotspots of energy efficiency research have been green communications, renewable energy, and energy sustainability; green communications, in particular, has developed rapidly as a focus of energy efficiency publications in recent years.     

The governance challenge for implementing effective market-based climate policies: A case study of The New South Wales Greenhouse Gas Reduction Scheme

The New South Wales (NSW) Greenhouse Gas Reduction Scheme (GGAS) in Australia is a baseline and credit emissions trading scheme with the stated aim of reducing the per-capita greenhouse emissions associated with electricity consumption in the state of NSW. Here we provide a detailed assessment of the GGAS design and operation, with a particular emphasis on its effectiveness in delivering physical emissions reductions that would not have occurred in its absence. We find that a number of design features mean a significant proportion of the tradeable ‘abatement’ certificates are unlikely to correspond to the claimed emissions reductions. While some of these adverse design choices might be corrected, others would seem inherent to the underlying scheme design. Our analysis highlights the major governance challenges with emissions trading approaches and hence the importance of good policy implementation processes including the need for separation of powers through a scheme development process that involves design, assessment and revision. These GGAS lessons would seem relevant for governance with all emissions trading schemes, and has particular implications for cap and trade schemes that incorporate baseline and credit offset schemes, as well as to the ‘White Certificate’ schemes increasingly being seen as a means of fostering enhanced end-use energy efficiency.     

Long-term prospects for compressed air storage

The compressed air storage (CAS) concept has been reviewed in the light of the long-term requirement for energy storage to effect load following in a predominantly nuclear generating system. This requirement would eventually lead to the operation of storage plant on a daily cycle of storing energy for 6–8 h and generating for 12–16 h. Conventional CAS schemes, typified by the Nordwestdeutchen Kraftwerke (NWK) installation in West Germany, are shown to be incapable of fulfilling this duty on merit.The basic concept is then re-examined and a novel development is proposed which, by using uncooled compressors and conserving the compression energy, constitutes a true energy storage scheme requiring no fuel other than the off-peak energy taken from the electrical grid. The efficiency and other performance characteristics of this proposal are discussed.The capital cost of an 8 GWh storage scheme is tentatively put at £125–175/kW (at 1974 price levels), depending on the air store construction, well within the £200/kW cost target which storage plant would need to meet to be of interest for storing off-peak nuclear power by the end of the present century. It is concluded that, once developed, CAS schemes which incorporate heat storage could provide an attractive method for storing off-peak electricity.     

Accounting for early action in the European Union Emission Trading Scheme

In the context of emission markets, failure to include early action (EA) as a criterion when sharing out the reduction effort may be unfair. This paper presents (1) a method based on index decomposition that seeks to quantify EA and (2) a method for determining effort sharing considering EA. It is shown that, in the case of European industry (EU-15) and for the period 1995–2005, EA accounted for a reduction of 21% in energy-related CO₂ emissions. Considering two alternative schemes for sharing out the reduction effort in European industry, equal shares (all industries in all countries reduce their emissions by the same percentage) and taking EA into account, we find that Spain, Austria, Italy, the United Kingdom and Sweden would be better off under an equal shares scheme as opposed to one that takes EA into account. The efforts of the remaining countries would be greater than if EA was taken into account. An equal shares scheme would also greatly benefit the textile, non-metallic mineral, paper and “other” industries, and would be particularly detrimental to the chemical, non-ferrous and other metal, and engineering industries.     

Thermodynamic assessment of an electrically-enhanced thermochemical hydrogen production (EETHP) concept for renewable hydrogen generation

A novel concept for coupling a thermochemical cycle with an electrochemical separation device for the generation of hydrogen from steam is reported and a thermodynamic analysis of the system is presented. In a conventional thermochemical cycle, an oxygen carrier material is thermally reduced, cooled, and then reoxidized in steam thereby generating hydrogen. However, this process often requires high temperatures (>1700 K) and/or low oxygen partial pressures (<0.001 atm) in order to meet thermodynamic requirements. Such extreme conditions can adversely affect the stability of the reactive oxides, reactor materials, and system efficiency. In our proposed technology, we seek to decrease the required reduction temperature by several hundred degrees Kelvin by relaxing the requirement for spontaneous oxidation reaction at atmospheric pressure. This is accomplished by incorporating a proton-conducting membrane (PCM) to separate hydrogen produced at equilibrium concentrations from reactant steam. We also suggest the use of mixed ionic-electronic conducting (MIEC) oxygen carrier materials that reduce through a continuum of oxidation states at lower temperatures (～1200 °C). This concept allows the generation of a high-quality hydrogen stream while avoiding the challenging high temperatures/low partial pressures required in conventional water-splitting reaction schemes.     

Performance Analysis of Small Size Compressed Air Energy Storage Systems for Power Augmentation: Air Injection and Air Injection/Expander Schemes

Two small size second-generation compressed air energy storage (CAES) systems have been investigated. Both plants are based on a 4600 kW Mercury recuperated gas turbine (GT) and on an artificial air storage system. In CAES air injection (CAES AI) plant, the stored compressed air is mixed with the air flow exiting the GT compressor and fed after a recuperative heating to the GT combustion chamber. A topping air expander is included in the CAES air injection/expander (CAES AI/E) plant scheme. Preliminary evaluations have been carried out to assess the maximum achievable GT power augmentation taking safety of operations and plant life duration into consideration. Plant performance has been evaluated during the overall operational cycle (charging, storage and discharging phases). CAES AI plant allows a 30% maximum extra power delivery (some 1500 kW) in respect to the nominal design GT power. The introduction of the topping air expander in CAES AI/E plant allows an additional power production of some 300 kW. Both plants have shown storage efficiency improvements by reducing the discharge period duration. Satisfactory values around 70% have been found in the best operating conditions.     

Techno-economic-environmental optimization of a solid oxide fuel cell-gas turbine hybrid coupled with small-scale membrane desalination

A techno-economic-environmental optimization of a pressurized solid oxide fuel cell-gas turbine (SOFC-GT) hybrid coupled with a small-scale seawater reverse osmosis (SWRO) desalination unit is presented. The overall exergy efficiency and cost rate of the system are maximized and minimized, respectively, using a genetic algorithm. The optimum solution selected, representing a trade-off between both optimization objectives, yields 2.4 MWe of electric power and 107 m³/day of permeate, at an overall exergy efficiency and cost rate of 70.5% and 0.0233 USD/s, respectively. These metrics compare favorably with those of alternative coupled SOFC-GT-thermal desalination systems previously optimized in the literature. Compared with the selected trade-off solution, single-objective optimizations of exergy efficiency and cost rate would permit a further improvement in exergy efficiency of 6%, and 9% reduction in cost rate, respectively. For the optimum economic solution, the SWRO unit would be effectively eliminated, with the system reducing to a SOFC-GT power plant. The system payback time is mostly sensitive to electricity prices, and ranges from two to ten years for typical economic parameters, but would become unprofitable in the most unfavorable economic context considered.     

Short-term impact of green certificates and CO2 emissions trading in the Swedish district heating sector

Swedish district-heating (DH) systems use a wide range of energy sources and technologies for heat-and-power generation. This provides the DH utilities with major flexibility in changing their fuel and technology mix when the economic conditions for generation change. Two recently introduced policy instruments have changed the DH utilities’ costs for generation considerably; the tradable green-certificate (TGC) scheme introduced in 2003 in Sweden, and the tradable greenhouse-gas emission permit (TEP) scheme introduced in the EU on January 1, 2005. The objective of this study is to analyse how these two trading schemes impact on the operation of the Swedish DH sector in terms of changes in CHP generation, CO₂ emissions, and operating costs. The analysis was carried out by comparing the most cost-effective operation for the DH utilities, with and without, the two trading schemes applied, using a model that handles the Swedish DH-sector system-by-system. It was found that the volume of renewable power generated in CHP plants only increased slightly owing to the TGC scheme. The TGC and the TEP schemes in force together, however, nearly doubled the renewable power-generation. CO₂ emissions from the DH sector may either increase or decrease depending on the combination of TGC and TEP prices. The overall CO₂ emissions from the European power-generation sector would, however, be reduced for all price combinations assuming that increased Swedish CHP generation replaces coal-condensing power (coal-fired plants with power generation only) in other European countries. The trading schemes also lower the operational costs of the DH sector since the cost increase owing to the use of more expensive fuels and the purchase of TEPs is outweighed by the increased revenues from sales of electricity and TGCs.     

A case study on the costs and the fuel consumption of harvesting,transporting, and chipping chains for logging residues in Japan

The objective of this study is to examine the feasibility of a harvesting and transporting system for logging residues including the cost, energy, and carbon dioxide (CO₂) effectiveness of fossil energy substitution with logging residues in Japan. “A harvesting and transporting system for logging residues” was constructed with reference to some European countries, where the utilization of bioenergy is making steady progress, and examined based on field experiments in Japanese forestry. The feasibility of the system was discussed from the standpoints of cost, energy, and CO₂, and the system was compared with those of European countries. Concerning the system, it is desirable that the process of chipper comminuting should be incorporated into the system as early as possible. Although such a system is not particularly feasible in Japan from the standpoint of cost, it is suggested that it should be possible for Japan to reduce the domestic CO₂ emissions by utilizing logging residues as alternative energy resources. A comparison with the European countries and a preliminary sensitivity analysis to the system demonstrate that the technical development to reduce the total cost, e.g., improving the forwarding and transporting efficiency, is essential for realizing bioenergy utilization in Japan.