Primary Energy Requirements Research Articles

Generation of compressed air by overdriven free-displacer thermocompressors – Experimental investigation of a three-stage cascade

Due to their straightforward design and advantageous operational characteristics, cascaded arrangements of overdriven free-displacer thermocompressors may provide a simple, expedient and cost-effective solution to reduce the high primary energy requirements for compressed air generation, which is a common challenge in industry. Following first experiments with a single-stage prototype, this contribution presents the first experimental realization of a three-stage cascade so that the overall concept has now been demonstrated to be fully operational for the first time. In particular, the predicted self-control capabilities of a stage located within the cascade and thus without any preset inlet or outlet pressure could be proven, whereas this had been impossible with the single-stage prototype before. Stable operation with all stages running is possible at total pressure ratios ranging from a practical maximum near 2.1 down to approximately 1.36. At even lower values, the pressure ratio of the first stage undercuts an analytically predicted lower stability limit and eventually stops, whereas the power density of the remaining stages is increased. To exploit the potential for improvement identified during the single-stage experiments, the design of the new stages is based on the first prototype, but has been optimized by a similarity-based scaling procedure and design evolution, resulting in a significant increase in power density from 7.1 W to 12.5 W per liter of displacement. To further demonstrate the capability of such a cascade to extract waste heat from a hot stream, the heater temperatures of the stages were successively reduced along the cascade by an adequate control, thus emulating a finite heat capacity rate of the stream. Although the exergy transferred to the compressed air flow is reduced in this case, the overall performance is not adversely affected. The combination of the models and the scaling approach, which have now been demonstrated experimentally, provides a comprehensive toolbox for the future development of a series machine.

COMPARATIVE THERMODYNAMIC AND ENVIRONMENTAL ANALYSIS OF VAPOR COMPRESSION REFRIGERATION SYSTEM USING C-PENTANE AS REFRIGERANT

The selection of refrigerant is one of the most important parameters when designing a cooling system. Hydrocarbon refrigerants have low primary energy requirements for effective cooling capacity and favourable thermodynamic properties that reduce both direct and indirect greenhouse gas emissions. In this study, a comparative performance and environmental analysis of the vapor compression refrigeration cycle using C-Pentane as the refrigerant was performed. The cooling performance and environmental effect of C-Pentane has been compared with the cooling performance and environmental effect of R134A, R407C and R404A refrigerants in the cooling system. During the analysis, the cooling system was examined under different operating conditions. The highest coefficient of performance (COP) value in the analysis was 6.485 for the refrigeration cycle using C-Pentane, and this value was obtained at 0 oC evaporator temperature and 25 oC condenser temperature operating condition. According to the Life Cycle Climate Performance (LCCP) analysis for refrigerants, the lowest total emission value belongs to C-Pentane. Direct Emission (DE) value and indirect emission (IE) value of C-Pentane are 57.5 kgCO2 and 24928.04 kgCO2, respectively.

Comparative life cycle assessment of light frame timber and reinforced concrete masonry structural systems for single-family houses in Luxembourg

The building sector's significant greenhouse gas emissions and energy consumption present added challenges to meeting European climate commitments amidst rapid population growth. In Luxembourg, single-family houses dominate the residential buildings, noticeably contributing to construction waste and CO2 emissions. This study compares the environmental impacts of a three-story reinforced concrete masonry single-family house and an identical timber building in Luxembourg, emphasizing greenhouse gas emissions and embodied energy. A cradle-to-grave life cycle assessment was conducted using Building Information Modelling (BIM) models to analyze the global warming potential and primary energy requirements. Environmental product declarations from the producers and the ÖKOBAUDAT German database were used to determine the environmental impacts of the materials. The results show that the timber building outperforms the concrete building with a 43.5% lower global warming potential, while the concrete building demonstrates a 15.6% reduction in primary energy demand. This aligns with the average outcomes of seven similar studies discussed in this paper, at 33.2% and 4.7%, respectively. Moreover, the timber building is 78.6% lighter than the concrete one. When evaluating benefits and loads beyond the system boundary, the timber building provides 3.6 and 4 times greater advantages in terms of global warming potential and primary energy, respectively, compared to the reinforced concrete masonry building. Additionally, the study explores the impact of reusing the floors in the timber building. The cradle-to-grave LCA reveals that reusing the timber slabs improves the building's global warming potential and primary energy by 2.4% and 1.2%, respectively. However, when considering the benefits and loads beyond the system boundary, floor system reuse exhibits a 38.9% surge in global warming advantages while reducing primary energy benefits by 28.1%. The findings advocate for a policy promoting timber construction and reuse in Luxembourg, aiming to achieve the net-zero emission target by 2050.

Revitalizing PT. Sindo Energy (SE): A Forward-Thinking Proposed Scenario Planning to Navigate Coal-Regulatory Changes and Ensure Sustainability

Coal is a valuable natural resource that belongs to the Indonesian state and serves as a crucial raw material for fulfilling the country’s primary energy requirements. Starting from 2022, the Government has made a formal declaration to attain Net Zero Emissions (NZE) by the year 2060. Presidential Decree no. 112 of 2022 has been issued to expedite the development of renewable energy for electricity supply. One of the consequences of this decree is the discontinuation of coal-based power plants, reflecting the government’s dedication to transitioning to alternative energy sources in the future. Sindo Energy (SE) is a mining contractor services company that operates under the Indonesia Mining Alliances (IMA). It specializes in the coal industry and has a significant market share, contributing to a Gross Profit Margin of 93.43%. Naturally, projects that collaborate with SE are firms that own coal and so have the power to influence the overall business operations. This study aims to offer a comprehensive and enduring perspective on the potential future occurrences of scenario planning. The fundamental basis for creating the four scenarios, namely Believing Spirit (BS), Pioneer of Changes (PC), Truly Fighter (TF), and Chameleon Specialist (CS), involves identifying the major focal issues, driving reasons, and sources of uncertainty. This research outlines four scenarios that depict the projected industrial conditions in 2040. Each scenario presents different ramifications and possibilities, as outlined in the study. This research also generates pre-emptive indicators for SE business, which will subsequently prove valuable for corporations in formulating strategic measures that the company can adopt to confront potential situations in the face of future uncertainty, via implementation plans spanning a minimum of 15 years, in the upcoming year.

Primary architecture and energy requirements of Type III and Type IV secretion systems.

Many pathogens use Type III and Type IV protein secretion systems to secrete virulence factors from the bacterial cytosol into host cells. These systems operate through a one-step mechanism. The secreted substrates (protein or nucleo-protein complexes in the case of Type IV conjugative systems) are guided to the base of the secretion channel, where they are directly delivered into the host cell in an ATP-dependent unfolded state. Despite the numerous disparities between these secretion systems, here we have focused on the structural and functional similarities between both systems. In particular, on the structural similarity shared by one of the main ATPases (EscN and VirD4 in Type III and Type IV secretion systems, respectively). Interestingly, these ATPases also exhibit a structural resemblance to F1-ATPases, which suggests a common mechanism for substrate secretion. The correlation between structure and function of essential components in both systems can provide significant insights into the molecular mechanisms involved. This approach is of great interest in the pursuit of identifying inhibitors that can effectively target these systems.

Life-Cycle Assessments of Meat-Free and Meat-Containing Diets by Integrating Sustainability and Lean: Meat-Free Dishes Are Sustainable

Nowadays, sustainable food choices are taking on an increasingly central role. This paper assesses the environmental loads and energy resources of meat-free (vegan and pescovegetarian) and meat-containing (traditional) restaurant soups and main dishes. The applied life-cycle assessment focuses on determining environmental loads and energy resources in restaurant products’ preparation, cooking, and end-of-life phases. Mann–Whitney and Kruskal–Wallis statistical methods were applied to investigate restaurant products’ distribution and carbon footprints. Furthermore, a sustainability assessment model was developed by integrating green-lean and life-cycle assessment approaches called “GreenCycLEAN”. Based on the analysis results, the whole life cycle of meat-free dishes has a lower environmental impact. However, the primary energy requirement of a vegetable soup is less favorable than that of a meat-containing soup. The preparation phase has higher burdens, and the cooking phase is the most energy intensive. Research results are helpful for the sustainability of catering establishments.

Modeling of Energy Consumption and Print Time for FDM 3D Printing Using Multilayer Perceptron Network

Given the recognized advantages of additive manufacturing (AM) printing systems in comparison with conventional subtractive manufacturing systems, AM technology has become increasingly adopted in 3D manufacturing, with usage rates increasing dramatically. This strong growth has had a significant and direct impact not only on energy consumption but also on manufacturing time, which in turn has generated significant costs. As a result, this problem has attracted the attention of industry actors and the research community, and several studies have focused on predicting and reducing energy consumption and additive manufacturing time, which has become one of the main objectives of research in this field. However, there is no effective model yet for predicting and optimizing energy consumption and printing time in a fused deposition modeling (FDM) process while taking into account the correct part orientation that minimizes both of these costs. In this paper, a neural-network-based model has been proposed to solve this problem using experimental data from isovolumetrically shaped mechanical parts. The data will serve as the basis for proposing the appropriate model using a specific methodology based on five performance criteria with the following statistical values: R2-squared > 99%, explained variance > 99%, MAE < 0.99%, MSE < 0.02% and RMSE < 1.36%. These values show just how effective the proposed model will be in estimating energy consumption and FDM printing time, taking into account the best choice of part orientation for the lowest cost. This model provides a global understanding of the primary energy and time requirements for manufacturing while also improving the system’s cost efficiency. The results of this work can be extended and applied to other additive manufacturing processes in future work.

Advanced downstream processing of bioethanol from syngas fermentation

Syngas fermentation is used industrially to produce diluted bioethanol (about 1–6 wt%). This research study proposes a novel downstream process that recovers bioethanol in an energy-efficient and cost-effective manner, improves fermentation yield by recycling all fermentation broth components (microbes, acetate and water), and is designed for full-scale industrial-level application. Therefore, vacuum distillation at fermentation temperature was conceptually studied as an initial ethanol recovery step, leading to a bottom stream that may be recycled. Advanced separation and purification techniques were designed to recover 99.5% of initially present ethanol as high-purity product (99.8 wt%). Mechanical vapor recompression and heat integration methods were used to maximize sustainability and eco-efficiency of the proposed recovery process. Implementation of these techniques on a process using 6 wt% ethanol feed stream decreased the total annual costs by 54.2% (from 0.175 to 0.080 $/kgEtOH), reduced the primary energy requirement by 66.1% (from 2.82 to 0.96 kWthh/kgEtOH), lowered the CO2 emission by up to 82.6% (from 0.414 to 0.072 kgCO2/kgEtOH), and reduced the fresh water usage by 62.6% (from 0.242 to 0.091 m3W/kgEtOH). Sensitivity analysis for ethanol concentrations ranging from 6 to 1 wt% showed that the recovery costs and energy use increased to 0.336 $/kgEtOH and 1.78 kWthh/kgEtOH respectively. Since ethanol recovery performs better but fermentation will perform worse at higher ethanol concentration in fermentation broth, there is a trade-off concentration for the overall process. The current analysis is an important step toward determining this trade-off.

Parametric analysis of solar-assisted trigeneration system based on energy and exergy analyses

Rapid deterioration of environment has led researchers to explore feasible forms of energy which could produce multiple energy forms with minimum inputs. Hence, in this study a nov-el trigeneration setup is explored so as to achieve simultaneous forms of energy in the form of electrical energy, heating and cooling, driving its primary energy requirements through a solar power tower. Molten salt is used in this study to transfer the heat from the solar component to the vapor absorption apparatus. Further the vapor absorption system is tested for thermody-namic performance for a couple of refrigerants (LiNO3-H2O and LiBr-H2O), so as to establish the Pareto-optimal fluid among them. In order to remove any adherent error in the measuring procedure, all equipment’s uncertainty analysis was performed which was negligibly small approximately at 5.34 % in terms of power plant efficiencies. An exact analysis was performed so as to estimate energy and exergy in efficiencies in the equipment while varying input pa-rameters. Zenith exergy destruction was achieved in 33.6% by the central receiver, followed by 24.9% by heliostat, and 7.8% in heat recovery steam generator. The highest energy and exergy efficiencies (62.6% and 20.6%) are attained on system working on LiBr-H2O, whereas (60.9% and 19.6%) were obtained in LiNO3-H2O operated system.

Energy renovation of the multi-residential historic building after the Zagreb earthquake – Case study

Historic buildings represent our cultural heritage and identity. Due to their age and building tradition, they are extremely vulnerable to seismic excitations, as confirmed by the recent earthquake in the city of Zagreb. In addition, historic buildings are among the buildings with the worst energy performance and very low indoor comfort. In the scope of this paper, the seismic and energy integrated approach is applied to a typical multi-residential building in Zagreb historical downtown. The main focus of the paper is on building envelope energy efficiency measures. Different variants of thermal insulation (external and internal), secondary windows (maintaining existing ones vs. new efficient ones) and ventilation (natural vs. mechanical with heat recovery) are analysed in terms of building energy performance (3D level). Furthermore, replacement of existing technical systems and installation of RES are also considered. Moreover, the acceptability of the proposed retrofitting solutions for opaque elements is evaluated in terms of thermal bridges (2D level) and long-term hygrothermal performance (1D level). Finally, the results show that it is possible even for a 100-year-old building to meet the current national primary energy requirements for new buildings and provide good indoor environmental quality for occupants while respecting the cultural heritage.

Implications of electric vehicle promotion policy on the road transport and electricity sectors for Thailand

This paper aims to analyze the implications of electric vehicle (EV) promotion policy on the Thai road transport and electricity sectors. For this purpose, this paper develops three scenarios representing different levels of EV penetration and assesses the scenario impacts with a view to identify policy implications and policy trade-offs of an increased EV deployment. A Low Emissions Analysis Platform (LEAP) model is employed, in this study, to assess the scenario impacts for the period 2020–2037. The analyses showed that high EV deployment in the transport sector would provide noticeable benefits, for example, reducing energy demand in the transport sector, decreasing primary energy requirements, and mitigating emissions of CO2, NOx and PM2.5. An increase in electricity generation would be, however, required for supporting increased EVs. The analyses further revealed that the impacts of high EV adoption in the transport sector could be considered in terms of both emerging challenges and opportunities. In terms of emerging challenges, promotion of EV adoption would pose several challenges including electricity grid impacts, energy security issues, and impacts on related industries. In order to address these challenges, the development of long-term electricity planning taking into account various issues, for example, a mixture of generating capacity additions, infrastructure expansion, coordinated charging, and time-of-use tariff setting would be essentially needed. EVs deployment would also bring several opportunities including the implementation of Vehicle-to-Everything (V2X) technology in smart grid and integration of renewable energy with V2X in smart grid. The success of these opportunities would, however, require policy supports from the Thai government and also the development of a consistent policy framework considering all related sectors. This framework is urgently required in order to provide effective strategies for developing sustainable future of electric mobility in Thailand.

Fuel cell drive for urban freight transport in comparison to diesel and battery electric drives: a case study of the food retailing industry in Berlin

The option of decarbonizing urban freight transport using battery electric vehicle (BEV) seems promising. However, there is currently a strong debate whether fuel cell electric vehicle (FCEV) might be the better solution. The question arises as to how a fleet of FCEV influences the operating cost, the greenhouse gas (GHG) emissions and primary energy demand in comparison to BEVs and to Internal Combustion Engine Vehicle (ICEV). To investigate this, we simulate the urban food retailing as a representative share of urban freight transport using a multi-agent transport simulation software. Synthetic routes as well as fleet size and composition are determined by solving a vehicle routing problem. We compute the operating costs using a total cost of ownership analysis and the use phase emissions as well as primary energy demand using the well to wheel approach. While a change to BEV results in 17–23% higher costs compared to ICEV, using FCEVs leads to 22–57% higher costs. Assuming today’s electricity mix, we show a GHG emission reduction of 25% compared to the ICEV base case when using BEV. Current hydrogen production leads to a GHG reduction of 33% when using FCEV which however cannot be scaled to larger fleets. Using current electricity in electrolysis will increase GHG emission by 60% compared to the base case. Assuming 100% renewable electricity for charging and hydrogen production, the reduction from FCEVs rises to 73% and from BEV to 92%. The primary energy requirement for BEV is in all cases lower and for higher compared to the base case. We conclude that while FCEV have a slightly higher GHG savings potential with current hydrogen, BEV are the favored technology for urban freight transport from an economic and ecological point of view, considering the increasing shares of renewable energies in the grid mix.

Emerging trends on the role of recombinant pectinolytic enzymes in industries- an overview

The primary energy requirement of almost all life-forms on earth is derived from plant sources. The plant cell wall (PCW) has a chemically complex structure composed of glycoproteins, aromatic compounds and carbohydrates. The carbohydrates include cellulose, hemicellulose and pectin. Cellulose has homogeneous structure, whereas hemicellulose and pectin are heterogeneous. Pectin constitutes as the most complex polysaccharide and is abundantly found in the middle lamella and primary cell wall of PCW. It is also proportionally the highest constituent of plant dry matter. The pectic substances are hydrolyzed by pectinolytic enzymes which are widely present in bacteria, fungi and plants. Pectinolytic enzymes are classified as de-polymerising and de-esterifying enzymes. The de-esterifying enzymes are the accessory enzymes which remove the side chains. The pre-action of de-esterifying enzymes removes the steric hindrance and provides better access to other de-polymerizing enzymes for complete degradation of pectin. This review describes the pectin structure and the structure, function and biochemical properties of recombinant pectinolytic enzymes from different microbial sources. The focus is on the specific role of individual pectinolytic enzymes in various industrial applications such as juice extraction, vegetable puree production, fibre retting, waste water treatment, pharmaceuticals, biomass hydrolysis and production of other value-added products. Thus, the enhanced use of pectinolytic enzymes in these growing industries holds a great potential for gaining insights about their efficient role in various sectors. • A core information about pectin structure and its components has been incorporated. • It details the structure, function and mode of action of individual pectinases. • Recent developments in novel bioengineered pectinolytic enzymes are included. • It elaborates recent advances on the role of individual pectinases in industries.

Retrofit strategies to obtain a NZEB using low enthalpy geothermal energy systems

The European Union introduced the concept of “Net Zero Energy Building” (NZEB) to promote competitive, sustainable, eco-friendly, and “decarbonised” cities. To these aims, mainly with reference to highly urbanized places, it is necessary to renovate existing buildings to achieve the NZEB target. Thus, this paper analyses the energy retrofit of an existing building considering two low enthalpy geothermal systems in the HVAC plants: the Ground-to-Air Heat eXchanger (GAHX) and the Ground Source Heat Pump (GSHP). These two plants are used in different retrofit strategies and compared from an energy, environmental and economic point of view. A dynamic simulation software based on EnergyPlus calculation engine is used. The results are very interesting and demonstrate how by using a low enthalpy geothermal plant, a very low value of primary energy requirement can be obtained (about 60 kWh/m2, i.e., −71% compared to the existing building, characterized by a gas boiler). Moreover, substantial savings on annual energy bills and reduction of CO2 emissions are obtained.

A longitudinal assessment of the energy and carbon performance of a Passivhaus university building in the UK

There is a limited number of university buildings designed to the Passivhaus standard, therefore, only a few studies have assessed the standard's adoption in this context. This paper aims to address this significant gap by investigating the energy and carbon performance of The Enterprise Centre (TEC), a UK university building, designed and certified to the Passivhaus standard. The building's energy performance was monitored for four years and was predicted by the Passivhaus Planning Package (PHPP) simulations. Results show that TEC met the primary energy requirement of 120 kWh/m2 and space cooling requirement of 15 kWh/m2 during the first four years of operation, as well as the space heating requirement of 15 kWh/m2 during the first two years. TEC had significantly reduced heat losses and heating demand, due to the very high airtightness, 0.21 m3/(m2·h) @50 Pa, and low envelope U-values. The building had significantly lower annual carbon emissions and energy consumption compared to CIBSE TM46 benchmarks and other conventional university buildings. TEC is an excellent building in terms of primary energy, heating consumption, cooling demand, airtightness and carbon emissions. This study bridges the gap on the adoption of the Passivhaus Standard for university buildings to reduce energy consumption and carbon emissions.

An Analysis of the Impacts of Solar Electricity Generation on the Electricity Industry for Thailand

This paper provides an analysis of the impacts of solar electricity generation on the electricity industry for Thailand. In this paper, three scenarios (REF, Solar2015 and Solar2018) are developed to represent an increased levels of electricity produced from solar energy. A Low Emissions Analysis Platform (LEAP) model is employed in this paper to assess the impacts for the period 2019-2037. This paper assesses the scenario impacts in terms of diversification of electricity generation, generation technology mix, primary energy requirement and CO2 emissions. The analysis reveals that greater role of solar energy in the electricity generation would have positive impacts on the Thai electricity generation from several aspects including improving the diversification of primary energy supply for electricity generation, reducing fossil fuel consumptions for power production, less reliance on fossil fuel sources and environmentally friendly electricity generation. For example, 20% share of solar in fuel mix for power generation would result in a 17% reduction in fossil fuel consumption. Furthermore, it would contribute to a 16% decrease in CO2 emissions and 28% reduction in SO2 emissions. Despite several benefits, there are a number of emerging barriers for promoting solar based electricity generation in Thailand. These include inefficient and unreliable nature of solar energy for baseload electricity demand, high-initial cost, unsupportable grid infrastructure and unfavourable regulatory framework. This paper, therefore, recommends that development of energy storage technologies, improvement of grid flexibility and the revision of the regulations to support solar energy business could be effective strategies in order to address the barriers facing the Thai electricity industry.

Quantum Geographic Information System (Q-GIS) based study on emerging energy scenario in Hilly Terrain

ABSTRACT The present scenario in industrial development, population growth, and improvement in people’s life style throughout the hilly areas has led to increase in primary energy consumption. To a fastest growing economy like India, the primary energy requirements will go up with assured supply of 3–4 times more than consumed at present. In order to reduce the carbon footprints and hence to promote the sustainable energy future, the renewable energy sources are only option to bridge this gap and its popularity is gradually gaining in Eastern Himalayan state of India. The present study deals with a case study on energy used pattern in hilly state of Sikkim where large hydro power projects of total rated capacity of 2150 MW are already been developed and commissioned. But due to resultant consequences of global warming, most of the glaciers on Himalayan belt are melting and may deplete in next 35–40 years of now which is responsible for large hydro power generation. In order to address this cause, government and private organizations have already started taking various steps to identify and develop renewable energy projects based on solar, wind, bio-fuel, micro hydel, etc. at potential sites. This study also accounts with Quantum Geographic Information System (Q-GIS, 2.18.0) based geo-processing model for showing up the highly potential sites for suitably harnessing wind energy at different hub heights as well as solar energy considering its key factors like GHI, DNI, DHI, and PVout for entire region of Sikkim. Based on the present analysis, Wind Power Density (WPD) varies up to 995 W/m2 in windy sites, whereas Solar PVout varies from 2.97 to 4.57 kWp and both sources are dominant at northern parts of Sikkim. This study suggests the valuable details to investors, policymakers, industrialist, and scientist for strategic energy planning to avert the future energy crises in hilly regions.

Preliminary study of a closed loop vertical ground source heat pump system for an experimental pilot plant (Rome, Italy)

A system for capturing thermal energy is planned for installation at the ENEA-Casaccia centre (Italy). Costs, primary energy requirements, pollutant emissions and seasonal electricity consumption were estimated. The configuration based on four boreholes of different depths and the sizing of the vertical loop (double-U) were performed according to the ASHRAE method. This pilot plant, the first under construction within an Italian research centre, is part of a long-term research project funded by the Italian Ministry of Economic Development. The results of this research could be applied throughout the Italian Tyrrhenian Apennine margin, which is geologically characterised by highly conductive lithotypes.

Driving forces of CO2 emissions and energy intensity in Colombia

We analyze the driving factors of CO2 emissions and energy intensity in Colombia during 1971–2017 and 1975–2016, respectively. We apply a factorial additive decomposition for CO2 emissions, starting from the Kaya identity, using the logarithmic mean Divisia index method. The increase in emissions is mainly explained by the affluence and population effects, but is partially offset by the energy intensity effect and, to a lesser extent, the carbonization effect. We then analyze the driving factors of energy intensity with a multiplicative decomposition. We first transform final energy into its total primary energy requirements. The decrease in energy intensity is mainly due to the reduction in sectoral energy intensity and, to a lesser extent, to structural change. We analyze the contribution to both effects of the different sectors considered and relate them with the structural changes of the Colombian economy and the policies applied. The most important contributions to sectoral energy intensity reduction are the efficiency improvements in the transport and industry sectors, while the decrease in the share of industry is the most relevant component explaining the reduction of the structural change effect. The results provide useful information for the analysis and design of energy and environmental policies.

Are we moving toward an energy-efficient low-carbon economy? An input\u2013output LMDI decomposition of CO_{2} emissions for Spain and the EU28

Spain is on a path toward the decarbonization of the economy. This is mainly due to structural changes in the economy, where less energy-intensive sectors are gaining more relevance, and due to a higher use of less carbon-intensive primary energy products. This decarbonization trend is in fact more accentuated than that observed in the EU28, but there is still much to be done in order to reverse the huge increases in emissions that occurred in Spain prior to the 2007 crisis. The technical energy efficiency is improving in the Spanish economy at a higher rate than in the EU28, although all these gains are offset by the losses that the country suffers due to the inefficient use of the energy equipment. There is an installed energy infrastructure (in the energy-consumer side) in the Spanish economy that is not working at its maximum rated capacity, but which has very high fixed energy costs that reduce the observed energy efficiency and puts at risk the achievement of the emissions and energy consumption targets set by the European institutions. We arrive to these findings by developing a hybrid decomposition approach called input–output logarithmic mean Divisia index (IO-LMDI) decomposition method. With this methodological approach, we can provide an allocation diagram scheme for assigning the responsibility of primary energy requirements and carbon-dioxide emissions to the end-use sectors, including both economic and non-productive sectors. In addition, we analyze more potential influencing factors than those typically examined, we proceed in a way that reconciles energy intensity and energy efficiency metrics, and we are able to distinguish between technical and observed end-use energy efficiency taking into account potential rebound effects and other factors.