The reduction of energy consumption in buildings is an important pillar of the European strategy to ensure that future climate and energy targets are reached. This paper focuses on the definition of ...Nearly zero energy buildings (NZEBs) that represent one of the greatest opportunities to increase energy savings in Europe. As this term appears to be subject to different interpretations, the paper explores the NZEB literature to provide an overview of definitions. The analysis underlines inconsistencies and critical issues among them. The paper also assesses the progress of the NZEB implementation in Europe, and compares the EU-NZEBs and the US-NZEBs definitions. The main debates arisen around NZEBs are evaluated. Among these topics, there are: the distinction between energy and primary energy, and between energy sources and energy carriers. A focus is also due to metrics and primary energy conversion factors. Special attention is provided in defining primary energy factors for energy carriers produced from renewable energy sources on site, nearby or far. After specifying the role of “plus” buildings, a complementary energy index, useful for defining incentives for buildings is formulated to overcome the questioning on the “negative” primary energy index that can be achieved using some of current net ZEB definitions. A proposal for clarifying the meaning of near zero, zero and plus energy buildings is also given. The analysis highlights that, although the attention given to NZEBs increased over the last years, the NZEB topic is still under discussion and not uniformly implemented.
•An overview of NZEBs definition is provided.•The main issues around NZEBs are presented and discussed.•A comparison between EU-NZEB and US-ZEB is given.•The progress of the NZEB implementation in Europe is assessed.•The definition of a novel energy index is proposed.
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•Primary energy use for a building differs a lot depending on calculation method.•The heating systems district heating and heat pumps are favored by different methods.•Overall, Swedish calculation ...methods give lower primary energy use.
The building sector accounts for a large part of the energy use in Europe and is a sector where the energy efficiency needs to improve in order to reach the EU energy and climate goals. The energy efficiency goal is set in terms of primary energy even though there are different opinions on how to calculate primary energy. When determining the primary energy use in a building several assumptions are made regarding allocation and the value of different energy sources. In order to analyze the difference in primary energy when different methods are used, this study use 16 combinations of different assumptions to calculate the primary energy use for three simulated heating and ventilations systems in a building. The system with the lowest primary energy use differs depending on the method used. Comparing a system with district heating and mechanical exhaust ventilation with a system with district heating, mechanical exhaust ventilation and exhaust air heat pump, the former has a 40% higher primary energy use in one scenario while the other has a 320% higher in another scenario. This illustrates the difficulty in determining which system makes the largest contribution to fulfilling the EU energy and climate goals.
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Reaching the European Union's 2030 targets for primary energy use (PE) and CO2 emissions (CE) requires an accurate assessment of how different technologies perform on these two fronts. To calculate ...the PE and CE associated with the consumption of electricity (e.g. by an electric vehicle or a heat pump) conversion factors (CFs) are required, namely a primary energy factor and a CO2 intensity factor. Previous theoretical work has shown that the calculation and use of CFs is a contentious and multifaceted issue, but a review of the actual practice in academic literature has so far been missing. 110 recent studies have been systematically reviewed across six methodological aspects, to find that 75% of the studies consider only a single country, 79% apply a purely retrospective perspective, 66% apply a yearly temporal resolution, 75% apply a purely operational (instead of a life-cycle) perspective, 85% make use of average (rather than marginal) CFs, and 77% ignore electricity imports from surrounding countries. Future research in which CFs are used should more carefully consider each of these methodological aspects and explicitly justify the choices that are being made on this front. There is also a strong need in the literature for a publicly available and methodologically transparent database of up-to-date CFs, which would not only enable more accurate and transparent PE and CE calculations, but also support the further development of building energy performance assessment methods and smart grid algorithms.
•Primary energy factors and CO2 intensities are crucial but contentious parameters.•The calculation and use of these ‘conversion factors’ is systematically reviewed.•Across 110 recent studies, six methodological aspects are assessed.•Methodological shortcomings and other overarching challenges are identified.•A publicly available database of conversion factors would benefit future research.
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The energy efficiency of different biogas systems, including single and co-digestion of multiple feedstock, different biogas utilization pathways, and waste-stream management strategies was ...evaluated. The input data were derived from assessment of existing biogas systems, present knowledge on anaerobic digestion process management and technologies for biogas system operating conditions in Germany. The energy balance was evaluated as Primary Energy Input to Output (PEIO) ratio, to assess the process energy efficiency, hence, the potential sustainability. Results indicate that the PEIO correspond to 10.5–64.0% and 34.1–55.0% for single feedstock digestion and feedstock co-digestion, respectively. Energy balance was assessed to be negative for feedstock transportation distances in excess of 22
km and 425
km for cattle manure and for Municipal Solid Waste, respectively, which defines the operational limits for respective feedstock transportation. Energy input was highly influenced by the characteristics of feedstock used. For example, agricultural waste, in most part, did not require pre-treatment. Energy crop feedstock required the respect cultivation energy inputs, and processing of industrial waste streams included energy-demanding pre-treatment processes to meet stipulated hygiene standards. Energy balance depended on biogas yield, the utilization efficiency, and energy value of intended fossil fuel substitution. For example, obtained results suggests that, whereas the upgrading of biogas to biomethane for injection into natural gas network potentially increased the primary energy input for biogas utilization by up to 100%; the energy efficiency of the biogas system improved by up to 65% when natural gas was substituted instead of electricity. It was also found that, system energy efficiency could be further enhanced by 5.1–6.1% through recovery of residual biogas from enclosed digestate storage units. Overall, this study provides bases for more detailed assessment of environmental compatibility of energy efficiency pathways in biogas production and utilization, including management of spent digestate.
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This open access handbook is distinguished by its emphasis on international energy, rather than domestic energy policies or international geopolitic aspects. Addressing key topics such as energy ...production and distribution, renewables and corporate energy structures, alongside global energy trends, regional case studies and emerging areas such as the digitalization of energy and energy transition, this handbook provides a major new contribution to the field of international energy economics. Written by academics, practitioners and policy-makers, this handbook is a valuable and timely addition to the literature on international energy economics. This book was published open access with the support of Eni.
This volume provides an overview of the political economy of coal in diverse country contexts. Coal is the largest source of greenhouse gas emissions globally, accounting for about 40 percent of ...energy-related CO2 emissions. Continued construction of coal-fired power plants could make the climate targets of the Paris Agreement infeasible to achieve. In spite of sharply declining costs for renewable energy sources, many countries still heavily rely on coal to meet their energy demand. The predominance of coal can only be adequately understood in light of the political factors that determine energy policy formulation. To this end, this edited volume assembles a wide variety of case studies exploring the political economy of coal for across the globe. These includes industrial and developing nations, coal importers and exporters as well as countries that are either substantial coal users, are just beginning to ramp up their capacities, or have already initiated a coal phase-out. Importantly, all case studies are structured along a unifying framework that focuses on the central actors driving energy policy formulation, their main objectives as well as the context that determines to what extent they can influence policy making. This large set of comparable studies will permit drawing conclusions regarding key similarities as well as differences driving coal use in different countries. This book will be of great interest to students and scholars of energy, climate change, resource management, and sustainable development. It will also appeal to practitioners and policymakers involved in sustainable development.
In order to expand the applicability of the conventional conformable fractional grey model, an extensive conformable fractional grey model, abbreviated as ECFGM(1,1), is proposed by the introduction ...of the extensive conformable fractional accumulation. Specifically, the improvements of the proposed model can be outlined as follows. First, the extensive fractional accumulation and difference are designed for accumulated generating operation and its reverse calculation, respectively. Second, based on the extensive form, the parameter estimation and time response function of the ECFGM(1,1) model are deduced, thereinto, the particle swarm optimization algorithm is employed to determine the optimal fractional order for the newly-designed model. It is worthy noting that an algorithm framework by the Monte Carlo simulation and parameter sensitivity analysis is conducted to assess the robustness of the proposed model. To validate this model’s efficacy, the novel technique is adopted to forecast China’s primary energy consumption compared with a series of competitive models. The numerical results indicate the newly-proposed model is superior to all competitors in terms of MAPE and RMSE values, thus, the proposed ECFGM(1,1) model is considered a powerful and promising method for enhancing the existing fractional grey models.
•An extensive conformable fractional grey model is proposed.•Particle Swarm Optimization is used to find the optimal fractional order.•Monte Carlo simulation and sensitivity analysis advance the robustness.•The proposed model is applied in China’s primary energy consumption.
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► The performances of CCHP system in different operation modes are compared. ► The CCHP system following electrical load and thermal loads are analyzed. ► The instantaneous performances of CCHP ...system with loads are obtained. ► The sensitivity of CCHP system to the technical parameters are analyzed.
Operation mode of combined cooling heating and power (CCHP) system determines its energetic and environmental performances. This paper analyzes the energy flows of CCHP system and separated production (SP) system. The fuel energy consumptions of CCHP system following electrical demand management (EDM) and thermal demand management (TDM) are deduced respectively. Three indicators: primary energy saving, exergy efficiency and CO
2 emission reduction, are employed to evaluate the performances of CCHP system for a commercial building in Beijing, China. The feasibility analysis shows that the performance of CCHP system is strictly dependent upon building energy demands. The selection of CCHP operation modes is systemically based on building loads, CCHP system and local SP system. The calculation results conclude that CCHP system in winter under EDM achieves more benefits than in summer. The sensitivity discussion indicates that the coefficient of performance for cooling and the efficiency of electricity generation are the most sensitive variables to the energetic and environmental performances of CCHP system.
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This study investigated the major factors that influence the CO2 emission in 12 Middle Eastern countries, namely, Bahrain, Egypt, Iran, Jordan, Kuwait, Lebanon, Oman, Qatar, Saudi Arabia, Syria, the ...UAE, and Yemen. A panel model was used in this study and the period 1990–2009 was considered. The results showed that the total primary energy consumption, foreign direct investment net inflows, GDP, and total trade were important factors in increasing CO2 emission in the investigated countries. Thus, it is important for these counties to examine the requirements for foreign investment to promote environmental protection and increase the technological transfer through foreign companies to reduce the environmental damage. It is also important for them to adopt trade-related measures and policies to increase environmental protection since total trade increases CO2 emission. It is also crucial for these countries to increase energy productivity to achieve their GDP growth.
► The factors that influence the CO2 emission in the Middle East were investigated. ► A panel model was used in this study taking the period 1990–2009. ► The energy consumption, FDI, GDP, and total trade increase CO2 emission.
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•A novel series connection between photovoltaic thermal module and solar thermal collector (PVT-ST) is proposed.•Model validation shows good agreement with experimental ...results.•Satisfactory thermal and electrical performance is observed from the PVT-ST system.•The system can produce 298.50 kWh electricity and 2096.51 kWh heat annually in Shanghai.
The photovoltaic thermal (PVT) module can produce electricity and heat simultaneously, while its outlet temperature is usually not high and might not be able to meet the requirement for hot water and spacing heating in buildings. In this study, an innovative integrated system is proposed that a PVT module is series-connected with a following solar thermal (ST) collector, renamed as PVT-ST, to overcome the drawback of low output temperature of PVT and no electrical generation of ST. The feasibility of the proposed system is discussed first, and a steady two-dimensional model is developed to investigate the thermal, electrical and overall performance of the PVT-ST system. The mathematical model is also validated based on the experimental data, revealing that the numerical results agree well with the collected data, with root mean square deviation lower than 1.39%. A comparative study is then conducted, and indicates that the PVT-ST system has slightly lower electrical efficiency but can output relatively high-grade thermal energy and performs much better in primary energy saving efficiency, the duel effects could make the system promising in residential buildings which need both electricity and heat. The PVT-ST system, occupying 1.65 m2 for both the PVT and ST collector, can output in average 0.82 kWh/day electricity and 5.75 kWh/day heat in Shanghai, as a result 83.48% of primary energy saving efficiency is achieved. Finally, a parametric analysis explicates that solar radiation and mass flow rate shows positive effects on overall performance, whereas a negative effect is observed from the inlet water temperature.
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