•EU policy efforts on energy efficiency in buildings stared in the 1970s in response to the oil crisis.•The first comprehensive EU policy was the SAVE directive in 1992, introducing policy actions ...still relevant today.•A major step forward was the Energy Performance of Buildings Directive in 2002 and its subsequent amendments.•Mandatory energy performance standards are progressively converging towards near zero energy buildings.•Additional policies and financing are needed for the full decarbonisation of the building stock.
The reduction of energy demand in buildings through the adoption of energy efficiency policy is a key pillar of the European Union (EU) climate and energy strategy. Energy efficiency first emerged in the EU energy policy agenda in the 1970s and was progressively transformed with shifting global and EU energy and climate policies and priorities. The paper offers a review of EU energy policies spanning over the last half century with a focus on policy instruments to encourage measures on energy efficiency in new and existing buildings. Starting from early policies set by the EU in response to the Oil Embargo in the 1973, the paper discusses the impact of EU policies in stimulating energy efficiency improvements in the building sector ranging from the SAVE Directive to the recently 2018 updated Energy Performance of Buildings Directive and Energy Efficiency Directive. The review explores the progress made over the last 50 years in addressing energy efficiency in buildings and highlights successes as well as remaining challenges. It discusses the impact of political priorities in reshaping how energy efficiency is addressed by EU policymakers, leading to a holistic approach to buildings, and provides insights and suggestions on how to further exploit the EU potential to save energy from buildings.
The energy consumption in buildings accounts for a significant proportion of total energy and carbon emissions over the world. To reduce the building energy consumption and achieve sustainable ...development of buildings, nearly zero energy buildings (NZEBs) have attracted widespread attention as a future building energy target. This paper reviews energy-efficient measures (EEMs) and renewable energy technologies (RETs) in NZEBs and discusses the application and suitability of the key technologies, i.e. minimizing the energy demand in NZEBs by EEMs and adopting RETs to meet the remaining energy needs. EEMs contain efficient thermal insulation system, high-performance window system, good airtightness and fresh air heat recovery system. RETs are composed of solar photovoltaic/thermal (PV/T) system, air source heat pump system (ASHP), ground source heat pump system (GSHP), and wind power. In addition, this paper emphasizes further research works, which involve life cycle energy analysis (LCEA), meteorological parameters change, intelligent building operation management (IBOM) system, energy storage system and social policy issues. This paper will provide some references for the further development of NZEBs in different climatic regions in China.
•This paper systematically reviews application of EEMs and RETs in NZEBs in China.•Feasibility and suitability of EEMs and RETs are evaluated from different aspects.•Further research work and development direction of NZEBs are pointed out.
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.
The paper proposes a multi-objective optimization approach to address the energy design of the building envelope. A genetic algorithm (GA) is implemented by means of the coupling between MATLAB® and ...EnergyPlus to minimize primary energy consumption (PEC), energy-related global cost (GC) and discomfort hours (DH). The design variables concern the set point temperatures, the radiative properties of plasters, the thermo-physical properties of envelope components, the window type, the building orientation. The GA performs a Pareto optimization and finally two optimal solutions are recommended: the nZEB (nearly zero energy building) optimal solution, which minimizes PEC, and the cost-optimal solution, which minimizes GC. These solutions provide the optimal design strategies for the public and private stakeholders, respectively, which represent the main actors involved in building design. The approach is applied for the design of a new typical Italian residential building. Four locations are considered to investigate the typical Italian climates. The outcomes can give precious indications to rebuild the Italian residential stock with a view to energy-efficiency and cost-optimality, given that the optimal solutions provide low values of PEC – between 62.0 and 91.9 kWhp/m2a – and of GC – between 456 and 665 €/m2 – depending on the location.
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•The methodology optimizes envelope energy design by using a genetic algorithm.•Primary energy consumption, global cost and discomfort hours are minimized.•The optimal most sustainable (nZEB) and the cost-optimal designs are achieved.•The methodology is applied to four different Italian climatic zones.•Original indications to rebuild the Italian residential stock are provided.
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•A new evaluation model of Nearly Zero Energy Cities (nZEC-EATEP) was presented.•nZEC-EATEP model contributes in the study of the energy self-sufficiency of cities.•nZEC-EATEP model ...extends the Zero Energy concept from buildings to cities.•The evaluation of a Nearly Zero Energy model for Barcelona city was presented.•PV self-consumption of Prosumers help to reduce energy consumption of cities.
As a contribution to the study of the urban energy transition, this paper proposes a novel model of energy-economic evaluation of the cities self-sufficiency and presents its application in the form of a case study. The objective of this study was to analyse the scope of the investment in the photovoltaic self-consumption of buildings in order to promote the creation of Prosumers communities within the cities. The operation of this model is based on the scalability of the Nearly Zero Energy concept from buildings to cities and seeks to evaluate Nearly Zero Energy Cities (nZEC): cities made up of Nearly Zero Energy Buildings (nZEB) and other installations of distributed generation to cover their energy demand by use of local renewable resources to the detriment of external resources. By using public data, we apply this model with the aim of economically evaluating the investment of six packages of energy rehabilitation and photovoltaic self-consumption in 17% of the residential buildings (37,800) in the city of Barcelona. To do this, we simulated 37 years of electricity distribution among Consumers, Producers and a hypothetical peer-to-peer community of Prosumers during the period 2014–2050 in hourly time intervals. The results indicated that the photovoltaic self-consumption and the local markets of Prosumers help to reduce primary energy consumption, the energy costs, and the CO2 emissions.
The concerted TABULA typology concept includes structural information and datasets of housing stocks from 20 European countries. It is being used for showcasing the effect of energy saving measures, ...for cross-country comparisons of building and supply system features as well as for setting-up housing stock models.
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•A concerted concept of residential building typologies has been developed.•The concept has been implemented in 20 European countries.•A common calculation method is used including a calibration to typical consumption.•Cross-country comparisons were performed for 600 residential buildings.•Average buildings have been used as simplified building stock models.
In the framework of the international projects TABULA and EPISCOPE residential building typologies have been created in 20 European countries. Each national typology consists of a classification scheme grouping buildings according to their size, age and further parameters and a set of exemplary buildings representing these building types. U-values of different age bands and energy expenditure factors of heat generators of these buildings are being compared. In addition, synthetical average buildings have been defined which are statistically representative for specific age and size bands and enable projections of the energy performance to the total housing stocks. Based on the common data structure the energy performance of the average buildings is calculated in a standardised way to form simplified housing stock models. In the context of inhomogeneous building stocks of European countries the results allow an understanding of the average and variation of parameters like U-values, supply system performances or final energy.
•Effect of external venetian blind on nearly zero-energy buildings was studied.•Energy performance of external shading in different climate regions was quantified.•Multiple optimization design of ...shading arrangement parameters was discussed.•A new index was proposed for evaluating the energy efficiency of external shading.
The development and promotion of nearly zero-energy buildings (NZEBs) is an inevitable trend of building energy conservation, and external venetian blind shading (EVBS) is one of the most effective technologies for NZEBs. Therefore, this study aims to analyze and optimize the energy-saving performance of EVBS for NZEBs in different climate regions of China. Based on EnergyPlus, the optimal shading arrangements of NZEBs are obtained by evaluating the shading performance of different shading slat angles, orientations, window-to-wall ratios (WWRs) and locations. The results show that the energy saving potential of EVBS for NZEBs is significant, especially in southwest of China. And the energy-saving trends of EVBS with different shading arrangements are similar regardless of the climates, and the maximum energy saving potential per unit window area of EVBS is obtained in slat angle of 0°, west orientation and low WWR. The total energy saving potential (P) gradually decreases first and then increases rapidly as the slat angle increases for all slat angle (0°~180°) shading conditions. And the multi-orientation shading effect is the sum of each single-orientation shading effect. In addition, the cooling efficiency index (CEI) is proposed to evaluate the importance of shading to reduce the cooling demand of buildings, and to guide the improvement of the self-performance of shading. This research will be helpful in guiding the application of EVBS for residential NZEBs in different climate regions of China.
Nowadays, most areas of human activity should be reviewed with the aim of reducing CO2 emissions, since these activities are producing the majority of these emissions. Specifically, the building ...sector is one of the main responsible activities. In order to minimize the ecological footprint and ensure energy sufficiency, European Union created the nearly-Zero Energy Building (nZEB) concept. More than ten years have elapsed and it worth to review the current state around the concept, considering the new advances in computer development that are already applicable to this field. Accordingly, recent researches published in reputed indexed journals and international conferences have been reviewed. This paper explains the nZEB concept and reviews research articles focused on achieving it. A research gap is detected, so enabling concepts and technologies as Building Energy Performance Simulation (BEPS) tools and Model Predictive Control (MPC) are recalled, and relevant researches where used are included in a specific state-of-the-art for each concept, since the academia considers that these tools should be applied in building air conditioning to achieve nZEB. After this deep analysis, we conclude that the possibilities to optimize the energy consumption are huge combining properly in a holistic way BEPS tools for modeling and simulation and MPC for control strategies. It is possible to manage a Heating, Ventilation and Air Conditioning (HVAC) system using Renewable Energy Sources (RES) in an effective means, reducing CO2 emissions problems worldwide and reaching considerable energy savings.
•The nZEB concept has been explained and different factors that are important to reaching this objective have been reviewed.•A A research gap has been detected about nZEB due they are not transversal only their focus is from a specific point of view.•It has been raised a holistic treatment, with a multidisciplinary approach to achieve the energy efficiency of the buildings.•BEPS tools literature have also been reviewed since the possibilities to optimize the energy consumption using them are huge.•The MPC concept has been explained and it is considered as a great control option to find optimal management of the energy.
•Graphical approach to assess matching between photovoltaic electricity and loads.•Combines the conventional measures self-sufficiency and self-consumption.•Possible to visualize improved matching ...with energy storage and load shifting.•Contribution of photovoltaic electricity for Swedish nearly zero energy buildings.
For on-site renewable energy supply, such as photovoltaic (PV) electricity generation, an important issue is the daily and seasonal matching between on-site supply and demand. The matching potential is frequently expressed using the load matching indicators such as self-sufficiency and self-consumption. This paper presents the Energy matching chart, which is a novel graphical approach to visualize the PV-load matching. The chart uses self-sufficiency and self-consumption to provide information regarding the matching in both size and time. Using the Energy matching chart, the matching between PV production and load presented in previous studies is graphically analyzed and compared. Furthermore, the potentials for the two most common measures for improving the matching, namely energy storage and load shifting, are investigated. The results show that energy storage has, on average, a significantly higher potential for increasing the PV-load matching than load shifting. The second part of the paper, illustrates the benefits of the Energy matching chart by evaluating the Swedish implementation of the EU legislation on nearly Zero Energy Buildings (nZEBs). The assessment is performed for detached houses and evaluates the feasibility to use PV and battery systems for Swedish nZEBs. The results show that on-site PV production can help buildings to meet the nZEB regulations, but there are limitations due to the poor time-dependent matching. With a combined PV-battery system, the potential to meet the regulation is significantly larger. To summarize, the Energy matching chart has the potential to become a useful tool in the assessment of PV system and the evaluation of load matching measures.
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