Buildings are a major contributor to climate change, accounting for one third of global energy consumption and one quarter of CO2 emissions. However, comprehensive information is lacking for the ...development, evaluation and monitoring of mitigation policies. This paper discusses the remaining challenges in terms of reliability and consistency of the available data. A review of energy use in buildings is presented to analyse its evolution by building types, energy services and fuel sources. Residential buildings are the most consuming, although tertiary expansion requires further analysis to develop sound specific indicators. Heating Ventilation and Air Conditioning (HVAC) systems concentrate 38% of buildings consumption, calling for strengthened standards and incentives for retrofitting. Electrification is rapidly increasing, representing a potential tool for climate change mitigation, if renewable power was promoted. However, energy use in buildings will only curb if global cooperation enables developing nations to break the link between economic growth, urbanisation and consumption. To this aim, efficiency gains both in construction and equipment, decarbonisation of the energy mix and a global awareness on energy conservation are all needed.
•Buildings account for a third of global consumption and a quarter of CO2 emissions.•HVAC accounts for 38% of buildings consumption, equivalent to 12% of final energy.•Population, wealth and urbanisation in emerging nations are the key upward drivers.•Energy intensity gains require retrofitting and adopting conservation behaviours.•Building’s electrification is far and pointless until the power sector is decarbonised
•Residential sector accounts for a quarter of consumption and a fifth of CO2 emissions.•HVAC accounts for a third of residential consumption, equivalent to 8% of final energy.•Collecting and ...reporting information is crucial to target residential energy policies.•Retrofitting of residential stock and adopting conservation behaviours are mandatory.•Residential electrification is far away and needs to be accompanied by the decarbonisation of the electricity sector.
The residential sector is a major contributor to climate change, accounting for almost a quarter of global energy consumption and a fifth of CO2 emissions in 2019. Since 2000, residential consumption has grown at a sustained rate of 1%/year, driven by the development of emerging economies, despite stagnation in developed countries. The increasing demand for living space, energy services and comfort levels seems difficult to curb, especially in the developing world on its fair attempt to reduce inequality. To understand these trends, this paper analyses the trajectories of key indicators of activity and efficiency in this sector, for emerging and developed regions, as well as for major consuming nations, mainly China, United States, European Union, Russia, India, Japan and Brazil. Despite data limitations, meaningful cross-country comparisons are presented for fuel mixes, energy services and dwelling types. Heating, ventilation and air conditioning (HVAC) systems account for a third of residential consumption and will grow rapidly as increasing wealth in emerging economies allows for satisfying the thermal comfort demand. Economic development will naturally increase housing size and equipment level and reduce household size, and could close the per capita consumption gap between developing and developed regions. Efficiency improvements could reduce the energy use intensity to around 10 koe/m2 but will not be enough to curb residential consumption. International cooperation, policy support and funding are essential to accelerate development and efficiency gains in developing countries without compromising environmental targets. In the meantime, politicians should focus on decarbonising the energy mix and promoting energy efficiency, while citizens focus on energy conservation to avoid irreversible environmental damage.
•Pyramidal approach for the analysis and decomposition of energy intensity.•Definition of structural and efficiency indicators for the whole energy system.•Impact of transformation processes and fuel ...types on supply side energy efficiency.•Emerging nations needed to worsen the efficiency of the supply side to thrive.•Renewable electrification simultaneously benefits energy and carbon intensities.
Energy efficiency remains as the main mitigation factor to slow down the growth of energy consumption and related CO2 emissions, undoubtedly the major responsible for climate change. Gaining insights into the driving forces that make efficiency change is a keystone to define energy policies and examine pathways to sustainable development. To this aim, this paper proposes a pyramidal approach for the analysis and decomposition of energy intensity, the main global efficiency indicator, using the LMDI method. First, the effects related to supply and demand sides of the energy system are separated in Primary Energy Factor and final energy intensity, respectively. Then, supply side is further decomposed to progressively reveal structural effects associated to transformation processes and fuel types. The approach is applied to the most emitting and consuming nations (China, United States, European Union, India, Russia, Japan) to provide a meaningful cross-country analysis over the period 1995–2017. Results show that energy intensity gains have been mainly driven by widespread demand side efficiency improvements from 25% to 61%. Regarding the supply side, unfavourable structural changes due to electrification, up to 12% in China, have only been offset by transformation efficiency gains about 6% in developed countries. Consequently, emerging economies have worsened their energy sector efficiency as they thrive. Changes in fuel mixes have generally contributed to energy intensity reductions (up to 4%) mainly due to shifts from coal and nuclear power towards gas and renewables plants. The proposed methodology could help stakeholders to effectively analyse the energy system and to develop policies to reduce its environmental impact.
The impact of energy use on the planet due to related CO2 emissions is continuously increasing, despite the adoption of efficiency and decarbonisation policies and widespread environmental awareness. ...Climate change mitigation will only succeed if the driving forces of consumption and emissions are deeply analysed, and effective means are provided to reverse their trends. To this aim, the Kaya Identity framework is revisited to classify indicators and decomposition studies in the literature. A comprehensive pyramid approach is proposed for the progressive disaggregation and discussion of energy and emissions changes. The approach is applied to the OECD and non-OECD to provide meaningful regional analysis of past trends and future projections according to stated policy intentions. Results show that a hopeful change has already begun in the developed region due to a sustained decrease of the energy intensity and a promising reduction of the carbon intensity. Emerging economies follow the performance of developed nations since 2013, held back by later economic development. Activity slowdown, energy conservation, renewable electrification, efficient power plants and coal phase out appear as the keystones for decarbonisation. As a result, emissions stabilisation could have already been achieved as rises in emerging countries are offset by drops in developed nations. However, more stringent climate policies, especially targeting carbon drivers, are urgently needed to enable emissions reductions compatible with a global temperature increase of 1.5°C.
•Classification of indicators and studies in the framework of Kaya Identity.•Definition of an Emissions Indicators Pyramid for analyses standardisation.•Activity slowdown and cleaner electricity drive emissions drop in the OECD since 2007.•Hopeful efficiency and carbon intensity changes in developing nations since 2013.•Energy intensity must be halved and carbon intensity quartered in 2040.
Water evaporation rate is among the most significant parameters to design and select air conditioning systems in buildings with indoor swimming pools. Experimental correlations are today widely used ...to estimate water evaporation rate, although discrepancies of up to 80% among existing correlations have been shown. An alternative to these empirical methods is the calculation of evaporation rate through computer fluid dynamics techniques. One of the most significant parameters to solve the mass transfer at the air-water interface in these models is the value of the turbulent Schmidt number. Although this value depends on air and water conditions (i.e., temperatures, velocities, and vapour pressure, among others), commercial computer fluid dynamics programmes set a fixed value by default. This study presents a new value through an experimental adjustment. A total of 40 experimental tests have been performed in a wind tunnel under typical conditions in indoor swimming pools. Afterwards, the adjustment was validated with data from 145 experimental tests reported in the scientific literature. The mean relative error in the evaporation rate using the turbulent Schmidt number was 7%, as against 25% using the value by default. The maximum error was reduced from 35% to 15% in forced convection regime.
The improvement of energy efficiency of products is a key pillar of climate and energy strategy in the European Union (EU). The first EU product policies were adopted in the late 1970s, and they have ...evolved to become a coherent set of implementing measures under framework directives that harmonise and refine the regulatory process. After years of weak implementation, considerable progress in terms of scale and ambition has been achieved in the last decade. In 2020, product mandatory measures covered 50% of the EU total final energy consumption, leading to 46 Mtoe energy savings. This paper describes the available policy instruments to promote energy efficiency and remove the market barriers hindering the penetration of the best performing technologies. It offers a review of the progress made over these last 40 years of EU product policies, describing the Energy Labelling, the Minimum Energy Performance Standards (MEPS), the Ecodesign Directive and the voluntary agreements (EU Ecolabel and Green Public Procurement). Moreover, it highlights the remaining challenges and provides policy recommendations to further exploit the EU potential to save energy from products.
•Energy efficiency in products is a key pillar of EU climate and energy strategy.•Despite 40 years of EU product policies, their scale has only improved since 2010.•In 2020, mandatory measures covered 50% of the EU final energy consumption.•By 2030, savings expect to reduce the final consumption by 17%.•Policy orientation to further exploit the energy savings of products is provided.
► We develop an energy management system in a naphtha reforming plant. ► We adopt a new approach for develop EMS based on data mining process. ► EMS establishes real-time baselines and targets for ...tracking energy performance. ► EMS evaluates potential and achieved energy savings adjusted to actual conditions. ► Significant savings have been achieved after the implementation of the EMS.
Despite the industrial sector accounts for about a quarter of total final consumption worldwide and great efforts have been carried out to reduce its energy use in the last decades, there are still substantial opportunities to improve industrial energy efficiency. Among those opportunities, energy management systems (EMSs) are one of the most successful and cost-effective ways to significantly reduce energy use, energy costs and environmental impact without affecting production and quality. This paper describes the development of an energy management system for a naphtha reforming plant by the use of a data mining approach. The paper shows how these techniques have been applied to identify key influence variables on energy consumption and to develop an energy performance model of the plant. Energy baseline and energy targets have been derived for the assessment of achieved and potential energy savings. Plant results show how savings may be achieved after the implementation of the EMS by tracking and adjusting performance against energy targets.
The distillation process accounts more than 25% of total process energy consumption in refineries. Therefore the energy improvements of the distillations units are very important for this sector. Six ...Sigma is a methodology supported by a handful of powerful statistical tools in order to reduce variation through continuous process improvement. This paper proposed the application of Six Sigma methodology for improving energy efficiency in a distillation unit of a naphtha reforming plant. The results reproduce the past energy performance of the unit through multivariate models and show optimal operation mode with an expected savings around 150,000€/year. Although the process may further improve optimizing the consumption of the reaction unit.
► We found that the 6σ is useful to reduce energy consumption of a distillation unit. ► We analyze and optimize distillation process of a naphtha reforming plant. ► Modeling the energy efficiency of the distillation unit of the reforming plant. ► Identified of the optimal operation conditions to improve energy efficiency.
The calculation of the shadows that building environment, building elements or shading devices may cast on the building envelope, plays a key role in load calculations and building energy simulation. ...Algorithms for solar shading calculations have direct repercussions on the accuracy of the results and the computational times of building simulation tools. This paper presents an improved method for direct solar shading calculations based on the projection of every polygon on a unique receiving surface and incorporates recent and high efficient algorithms to solve polygon intersections. Firstly, the method is shortly described. Secondly, it is validated by comparisons with other methods, experimental results and European standards. Then, a comparison test between the proposed and conventional methods is presented to assess computational speed improvement. Finally, the main advantages of the proposed method are discussed.
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