Life-cycle energy of residential buildings in China

In the context of rapid urbanization and new construction in rural China, residential building energy consumption has the potential to increase with the expected increase in demand. A process-based hybrid life-cycle assessment model is used to quantify the life-cycle energy use for both urban and rural residential buildings in China and determine the energy use characteristics of each life cycle phase. An input–output model for the pre-use phases is based on 2007 Chinese economic benchmark data. A process-based life-cycle assessment model for estimating the operation and demolition phases uses historical energy-intensity data. Results show that operation energy in both urban and rural residential buildings is dominant and varies from 75% to 86% of life cycle energy respectively. Gaps in living standards as well as differences in building structure and materials result in a life-cycle energy intensity of urban residential buildings that is 20% higher than that of rural residential buildings. The life-cycle energy of urban residential buildings is most sensitive to the reduction of operational energy intensity excluding heating energy which depends on both the occupants' energy-saving behavior as well as the performance of the building itself.     

Cost benefits analysis and emission reductions of optimum thickness and air gaps for selected insulation materials for building walls in Maldives

The demand for electricity in the Maldives continues to increase by more than 11% in recent years. This is mainly due to the growing number of high-rise air-conditioned buildings and the increasing use of electrical appliances in the residential and commercial sector. This paper investigates potential cost savings and emission reductions achieved by installing different insulation materials of optimum thickness in building's walls. The paper also investigates the effect when air gaps are introduced in the wall. The optimum insulation thickness is based on the cost benefits of each insulation material over its lifetime. This study found that by introducing optimal thickness of different insulation materials and by having air gaps of 2 cm, 4 cm and 6 cm, energy consumption and emissions can be reduced by 65–77%, in comparison to a wall without insulation or air gaps. And, hence have considerable cost savings.     

Development of China TIMES-30P model and its application to model China's provincial low carbon transformation

To explore the provincial energy system transformation till 2050 under the carbon emission constraints from a bottom-up perspective, this research develops the China TIMES-30P model with detailed characterization of China's provincial energy system and applies it to low carbon scenarios analysis. A set of methodology is developed to project the key provincial socio-economic parameters and the provincial energy service demand, which is the major driving force of the China TIMES-30P model. Results show that compared with the value in 2015, the provincial intensity of final energy consumption will decrease by 65%–90% under different scenarios in 2050. The intensities of primary energy consumption in most of the provinces will be lower than 0.2 tce/1000 dollars under different scenarios in 2050. In the WBD2 scenario, the national CO₂ emission can reach the peak value of 9.3 billion tons in 2020 and the provincial CO₂ emission intensity in 2050 will decrease by 85%–100%, compared with the value in 2015.     

The energy saving index and the performance evaluation of thermochromic windows in passive buildings

The concepts of the energy saving equivalent (ESE) and energy saving index (ESI) are presented in this paper to evaluate the performance of new materials and components in passive buildings. The ESE represents the hypothetical energy that should be input to maintain a passive room at the same thermal state as that when a particular material or component is adopted. The ESI is the ratio of a particular material or component's energy saving equivalent to the corresponding value of the ideal material or component that can maintain the room at an ideal thermal state in passive mode. The former can be used to estimate the effect of the adoption of a certain building component or material on the building's thermal state from an energy standpoint, while the latter can be used to characterize the performance of the actual building component or material from a common standpoint and be used to evaluate the performance of components or materials in different climatic regions or under different operating situations. In this study, the ESI was used to evaluate the performance of a thermochromic window, represented by a single vanadium dioxide (VO₂) glazing, in passive residential buildings in three climatic regions of China (cold zone, hot summer and cold winter zone, and hot summer and warm winter zone).     

A 100% wind,water, sunlight (WWS) all-sector energy plan for Washington State

This study analyzes the potential and consequences of Washington State's use of wind, water, and sunlight (WWS) to produce electricity and electrolytic hydrogen for 100% of its all-purposes energy (electricity, transportation, heating/cooling, industry) by 2050, with 80–85% conversion by 2030. Electrification plus modest efficiency measures can reduce Washington State's 2050 end-use power demand by ∼39.9%, with ∼80% of the reduction due to electrification, and can stabilize energy prices since WWS fuel costs are zero. The remaining demand can be met, in one scenario, with ∼35% onshore wind, ∼13% offshore wind, ∼10.73% utility-scale PV, ∼2.9% residential PV, ∼1.5% commercial/government PV, ∼0.65% geothermal, ∼0.5% wave, ∼0.3% tidal, and ∼35.42% hydropower. Converting will require only 0.08% of the state's land for new footprint and ∼2% for spacing between new wind turbines (spacing that can be used for multiple purposes). It will further result in each person in the state saving ∼$85/yr in direct energy costs and ∼$950/yr in health costs [eliminating ∼830 (190–1950)/yr statewide premature air pollution mortalities] while reducing global climate costs by ∼$4200/person/yr (all in 2013 dollars). Converting will therefore improve health and climate while reducing costs.     

China's energy and emissions outlook to 2050: Perspectives from bottom-up energy end-use model

Although China became the world's largest CO₂ emitter in 2007, the country has also taken serious actions to reduce its energy and carbon intensity. This study uses the bottom-up LBNL China End-Use Energy Model to assess the role of energy efficiency policies in transitioning China to a lower emission trajectory and meeting its 2020 intensity reduction goals. Two scenarios – Continued Improvement and Accelerated Improvement – were developed to assess the impact of actions already taken by the Chinese government as well as planned and potential actions, and to evaluate the potential for China to reduce energy demand and emissions. This scenario analysis presents an important modeling approach based in the diffusion of end-use technologies and physical drivers of energy demand and thereby help illuminate China's complex and dynamic drivers of energy consumption and implications of energy efficiency policies. The findings suggest that China's CO₂ emissions will not likely continue growing throughout this century because of saturation effects in appliances, residential and commercial floor area, roadways, fertilizer use; and population peak around 2030 with slowing urban population growth. The scenarios also underscore the significant role that policy-driven efficiency improvements will play in meeting 2020 carbon mitigation goals along with a decarbonized power supply.     

Long-term energy savings and greenhouse gas emission reductions in the Swiss residential sector

The aim of this paper is to explore the possibilities to reach two long-term targets regarding energy consumption and greenhouse gas emissions of the Swiss residential building stock: a reduction of the final energy consumption by a factor of 3 and of _CO2${\mathrm{CO}}_2$ emissions by a factor of 5 until 2050. A model is constructed to describe the dynamics of the energy-relevant properties of the residential building stock. Appropriate scenarios are discussed in terms of decisions made during construction or renovation of residential buildings which affect heat demand and determine the energy carriers used for heating and hot water generation. We show that both targets could be reached, although ambitious efforts are necessary. The central element of a successful strategy is to reduce the specific heat demand of existing buildings during renovation and to substitute the heating and hot water systems by less carbon intensive ones. Our results suggest that there is more flexibility to reach the emission target than the energy reduction target.     

Energy efficiency improvement potentials and a low energy demand scenario for the global industrial sector

The adoption of energy efficiency measures can significantly reduce industrial energy use. This study estimates the future industrial energy consumption under two energy demand scenarios: (1) a reference scenario that follows business as usual trends and (2) a low energy demand scenario that takes into account the implementation of energy efficiency improvement measures. These scenarios cover energy demand in the period 2009–2050 for ten world regions. The reference scenario is based on the International Energy Agency World Energy Outlook (2011 edition) up to 2035 and is extrapolated by Gross Domestic Product projections for the period 2035–2050. According to the reference scenario, the industrial energy use will increase from 105 EJ in 2009 to 185 EJ in 2050 (excluding fuel use as a feedstock). It is estimated that, with the adoption of energy efficient technologies and increased recycling, the growth in industrial energy use in 2050 can be limited to 140 EJ, an annual energy use increase of 0.7 % compared with the 2009 case. The 2050 industrial energy use in the low energy demand scenario is estimated to be 24 % lower than the 2050 energy use in the reference scenario. The results of this study highlight the importance of industrial energy efficiency by providing insights of the energy savings potentials in different regions of the world.     

Energy efficiency outlook in China’s urban buildings sector through 2030

This study uses bottom-up modeling framework in order to quantify potential energy savings and emission reduction impacts from the implementation of energy efficiency programs in the building sector in China. Policies considered include (1) accelerated building codes in residential and commercial buildings, (2) increased penetration of district heat metering and controls, (3) district heating efficiency improvement, (4) building energy efficiency labeling programs and (5) retrofits of existing commercial buildings.Among these programs, we found that the implementation of building codes provide by far the largest savings opportunity, leading to an overall 17% reduction in overall space heating and cooling demand relative to the baseline. Second are energy efficiency labels with 6%, followed by reductions of losses associated with district heating representing 4% reduction and finally, retrofits representing only about a 1% savings.     

Thermal energy storage in building integrated thermal systems: A review. Part 2. Integration as passive system

Energy consumption trends in residential and commercial buildings show a significant increase in recent decades. One of the key points for reducing energy consumption in buildings is to decrease the energy demand. Buildings envelopes are not just a structure they also provide protection from outdoor weather conditions always taking into account the local climate. Thermal energy storage has been used and applied to the building structure by taking advantage of sensible heat storage of materials with high thermal mass. But in recent years, researchers have focused their studies on the implementation of latent heat storage materials that if well incorporated could have high potential in energy demand reduction without occupying the space required by sensible storage. The aim of this study is to review the thermal energy storage passive systems that have been integrated in building components such as walls, ceilings or floors, and to classify them depending on their component integration.     

Development and initial trial of a tool to enable improved energy & human performance in existing commercial buildings

Green Building has been a large focus for the construction industry, with Green Star certified commercial buildings becoming the new standard for commercial office buildings. However there has been little focus on the improvement of existing buildings, and many of Australia's capital cities have ageing building stock that is not operating efficiently and contributing to the nation's growing greenhouse gas emissions.Retrofitting existing buildings for energy efficiency is receiving more attention across Australia, with grants and funding to incentivise owners to find energy efficient solutions for buildings. However it is important that optimising performance of these buildings considers the impact on occupants. Australians spend the majority of their day indoors and the quality of the indoor environment can have a major impact on the health and productivity of workers.This paper covers the development of a tool for a project sponsored by the Sustainable Built Environment National Research Centre to assist building stakeholders identify key energy performance issues with their buildings. The tool explores 5 key areas in buildings that influence energy performance: design elements, building management, occupant experience, agreements and culture and indoor environment quality.The paper explains the development of the tool and some surprising results from the first trial on the tenancy for a 28 year old commercial building in the Perth CBD that underwent a Green Star interiors fit-out.     

Price and expenditure elasticities of residential energy demand during urbanization: An empirical analysis based on the household-level survey data in China

Urbanization, one of the most obvious characteristics of economic growth in China, has an apparent “lock-in effect” on residential energy consumption pattern. It is expected that residential sector would become a major force that drives China's energy consumption after urbanization process. We estimate price and expenditure elasticities of residential energy demand using data from China's Residential Energy Consumption Survey (CRECS) that covers households at different income levels and from different regional and social groups. Empirical results from the Almost Ideal Demand System model are in accordance with the basic expectations: the demands for electricity, natural gas and transport fuels are inelastic in the residential sector due to the unreasonable pricing mechanism. We further investigate the sensitivities of different income groups to prices of the three types of energy. Policy simulations indicate that rationalizing energy pricing mechanism is an important guarantee for energy sustainable development during urbanization. Finally, we put forward suggestions on energy pricing reform in the residential sector based on characteristics of China's undergoing urbanization process and the current energy consumption situations.     

Modelling the UK residential energy sector under long-term decarbonisation scenarios: Comparison between energy systems and sectoral modelling approaches

The UK government has set a groundbreaking target of a 60% reduction in carbon dioxide (CO₂) emissions by 2050. Scenario and modelling assessment of this stringent target consistently finds that all sectors need to contribute to emissions reductions. The UK residential sector accounts for around 30% of the total final energy use and more than one-quarter of CO₂ emissions. This paper focuses on modelling of the residential sector in a system wide energy–economy models (UK MARKAL) and key UK sectoral housing stock models. The UK residential energy demand and CO₂ emission from the both approaches are compared. In an energy system with 60% economy-wide CO₂ reductions, the residential sector plays a commensurate role. Energy systems analysis finds this reduction is primarily driven by energy systems interactions notably decarbonisation of the power sector combined with increased appliance efficiency. The stock models find alternate decarbonisation pathways based on assumptions related to the future building stock and behavioural changes. The paper concludes with a discussion on the assumptions and drivers of emission reductions in different models of the residential energy sector.     

Effect of building regulation on energy consumption in residential buildings in Korea

According to the International Energy Agency (IEA), the energy demand for the building sector constituted about 25.3% of the final energy use in South Korea. The energy demand for residential buildings counts for 50.3% of the building sector and has also increased by 2.9 percent every year. The Korean government has shifted focus and is now promoting energy efficiency within the building sector and has set long-term energy conservation goals.Despite these efforts to minimize building energy, the Korean government has changed the building regulation to allow remodeling of the balcony space as a living space. Remodeling the balcony space to become an indoor space means that a buffer space for the outdoor environment is lost, causing thermal discomfort and discomfort glare and moreover, increasing the heating and cooling energy demand in residential buildings. Also, it results in an increase in building energy demand in South Korea.In this study, the effect of the alteration of balcony space on the indoor thermal environment and the heating and cooling energy demand of residential buildings in Korea were investigated by field measurement and simulation. From the measurement results, the indoor temperature of the condition without a balcony was 0.8 °C lower than that with a balcony. The heating and cooling load of the unit without the balcony space was 39% and 22% higher, respectively, than that of the unit with the balcony space. This increase results in considerable energy loss in the national scale and the ratio will be 0.3% of the final energy use in Korea. Also, it represents about 1.3% of the final energy use within the building sector of Korea.     

Urbanisation and its impact on building energy consumption and efficiency in China

The People's Republic of China and its 1.3 billion people have experienced a rapid economic growth in the past two decades. China's urbanisation ratio rose from around 20% in the early 1980s to 45% in 2007 [China Urban Research Committee. Green building. Beijing: Chinese Construction Industrial Publish House; 2008. ISBN 978-7-112-09925-2.]. The large volume and rapid speed of building construction rarely have been seen in global development and cause substantial pressure on resources and the environment. Government policy makers and building professionals, including architects, building engineers, project managers and property developers, should play an important role in enhancing the planning, design, construction, operation and maintenance of the building energy efficiency process in forming the sustainable urban development. This paper addresses the emerging issues relating to building energy consumption and building energy efficiency due to the fast urbanisation development in China.     

Impact of voluntary green certification on building energy performance

Credible estimates of energy savings from green buildings are critical for policy makers to examine the cost and benefit of various incentives intended to encourage commercial buildings to go green (e.g. expedited construction permits, government grants, and property tax incentives). Yet, data limitations have hindered reliable estimations. Filling this gap, this study uses a large panel dataset on energy consumption for commercial buildings in Phoenix metropolitan area, Arizona. By tracking building occupants' monthly energy consumption before and after the building's certification as an Energy Star building, we provide new estimates of the environmental gains from private investment in green real estate. Results show that for occupants that occupy space in a certified building in both the pre-certification and post-certification periods, occupants in Energy Star buildings consume 8% less energy. This empirically robust estimate of potential benefit from green-certification provides a quantifiable benchmark against which green-promoting policies can be measured. We also document evidence of heterogeneous treatment effects. Energy savings differ by the building's initial certification points and the building's baseline energy consumption. These results are useful for policy makers to identify targets for green certification.     

Building energy saving potential in Hot Summer and Cold Winter (HSCW) Zone,China—Influence of building energy efficiency standards and implications

Hot Summer and Cold Winter (HSCW) region plays an important role in China's building energy conservation task due to its high consumption in recent years for both climate and social reasons. National and local building energy standards according to which the buildings are built and operated can affect the building energy consumption to a great extent. This study investigated the energy saving potential in Hot Summer and Cold Winter Zone under different level of energy efficiency standards (China local, China national, and UK standard). Chongqing was taken as an example, and the commercial energy simulation tool eQuest was applied to analyze the building end-use energy. With the existing situation as a baseline, the building energy saving for residential section could achieve 31.5% if the Chinese national standard were satisfied, and the value would further increase to 45.0% and 53.4% when the Chongqing local and UK standard were met. For public buildings, the corresponding energy saving potentials were 62.8%, 67.4% and 75.9%. Parameter sensitivity analysis was conducted. The analysis was able to provide suggestions on energy saving implementation priorities for residential and public buildings. Indications to improve building energy standards and their implementation were also discussed.     

夏热冬暖地区居住建筑应对气候变化节能适应性

为研究夏热冬暖地区居住建筑应对气候变化的适应性,运用TRNSYS动态能耗模拟软件对该地区典型居住建筑能耗进行仿真,制定了居住建筑节能星级评估体系。以广州市为例,分析预测了广州2020年、2050年及2080年的气候变化,并提出应对气候变化的节能措施。研究表明：气温上升1℃,4.0、5.5及6.5星级建筑能耗将分别增长25%、20%及20%;在2080年,气温上升近3.5℃,4.0星级建筑CO2年排放量达53 t/m2,将4.0星建筑升级到5.5和6.5星级,每年可相应减排19.5 t/m2和23.2 t/m2;若以4.0星级建筑当前的CO2排放量为控制目标,则需把建筑围护结构热工性能提升到6.5星级水平,可以实现未来70年减排45%。     

German Energiewende and the heating market – Impact and limits of policy

The German Energiewende envisages achieving a climate-neutral building stock in 2050 by means of two major pillars of regulation. First, residential buildings should consume 80% less primary energy and second; the remaining energy demand should be covered primarily with renewables. This paper simulates the future German heating market under different policy scenarios in order to evaluate the impact and limits of recent and conceivable policies. The investigation is based upon a dual model approach, linking a residential heating model to a discrete choice model. The major finding is that current regulations are not suitable for the achievement of governmental targets. Scenario calculations show that additional carbon emission reductions, triggered by the current regulatory regime, are falling short of expectations. In terms of economic efficiency, all calculated policy alternatives outperform the regulation currently in place. This allows to draw the conclusion that carbon emission reductions can be achieved without a major increase in cost. The model results highlight two policy implications. First, a rising mandatory share of renewables in the heating market is needed for target achievement and can be cost effectively. Second, renewable obligations for heating systems must include the existing building stock to achieve the postulated political targets.     

Numerical assessing energy performance for building envelopes with phase change material

In hot climate, phase change material (PCM) can be incorporated into building envelopes to reduce heat gain through the building envelopes and therefore reduce its cooling demand. In this study, the energy performance of building envelopes integrated with PCM has been explored using a popular dynamic building performance simulation package, EnergyPlus, and the energy saving mechanism of PCM was investigated. The simulation results reflected that PCM could effectively help to reduce the building's annual energy consumption by 20.9% for Guangzhou, China. In addition, for the Guangzhou city, 27°C transition temperature, smaller thermal conductivity of roof, and higher amount of PCM can all help to improve the building's energy performance. Additionally, it is suggested that in real building development/retrofit projects, the selection of PCM needs to be based on both their thermal properties and the local climatic conditions of the building.