Prediction of greenhouse gas reduction potential in Japanese residential sector by residential energy end-use model

A model is developed that simulates nationwide energy consumption of the residential sector by considering the diversity of household and building types. Since this model can simulate the energy consumption for each household and building category by dynamic energy use based on the schedule of the occupants’ activities and a heating and cooling load calculation model, various kinds of energy-saving policies can be evaluated with considerable accuracy. In addition, the average energy efficiency of major electric appliances used in the residential sector and the percentages of housing insulation levels of existing houses is predicted by the “stock transition model.” In this paper, energy consumption and CO₂ emissions in the Japanese residential sector until 2025 are predicted. For example, as a business – as-usual (BAU) case, CO₂ emissions will be reduced by 7% from the 1990 level. Also evaluated are mitigation measures such as the energy efficiency standard for home electric appliances, thermal insulation code, reduction of standby power, high-efficiency water heaters, energy-efficient behavior of occupants, and dissemination of photovoltaic panels.     

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.     

Model projections for household energy use in India

Energy use in developing countries is heterogeneous across households. Present day global energy models are mostly too aggregate to account for this heterogeneity. Here, a bottom-up model for residential energy use that starts from key dynamic concepts on energy use in developing countries is presented and applied to India. Energy use and fuel choice is determined for five end-use functions (cooking, water heating, space heating, lighting and appliances) and for five different income quintiles in rural and urban areas. The paper specifically explores the consequences of different assumptions for income distribution and rural electrification on residential sector energy use and CO₂ emissions, finding that results are clearly sensitive to variations in these parameters. As a result of population and economic growth, total Indian residential energy use is expected to increase by around 65–75% in 2050 compared to 2005, but residential carbon emissions may increase by up to 9–10 times the 2005 level. While a more equal income distribution and rural electrification enhance the transition to commercial fuels and reduce poverty, there is a trade-off in terms of higher CO₂ emissions via increased electricity use.     

On the potential trade-offs between energy supply and end-use technologies for residential heating

In Sweden, where district heating accounts for a significant share of residential heating, it has been argued that improvements in end-use energy efficiency may be counter-productive since such measures reduce the potential of energy efficient combined heat and power production. In this paper we model how the potential trade-offs between energy supply and end-use technologies depend on climate policy and energy prices. The model optimizes a combination of energy efficiency measures, technologies and fuels for heat supply and district heating extensions over a 50 year period. We ask under what circumstances improved end-use efficiency may be cost-effective in buildings connected to district heating? The answer hinges on the available technologies for electricity production. In a scenario with no alternatives to basic condensing electricity production, high CO₂ prices result in very high electricity prices, high profitability of combined heat and power production, and little incentive to reduce heat demand in buildings with district heating. In contrast, in a scenario where electricity production alternatives with low CO₂ emissions are available, the electricity price will level out at high CO₂ prices. This gives heat prices that increase with the CO₂ price and make end-use efficiency cost-effective also in buildings with district heating.     

Combustion performance of low-NOx and conventional storage water heaters operated on hydrogen enriched natural gas

Adding renewable hydrogen into natural gas pipeline would bring down the net gas C/H ratio and hence the CO₂ emissions. Also, it can help stabilize electric grids and maximize the renewable output of intermittent energy sources (solar, wind, etc.) via power-to-gas pathway. However, hydrogen differs in its chemical and physical characteristics (flammability range, flame speed, density, adiabatic flame temperature, energy content, etc.) than natural gas. Before transitioning to hydrogen admixing into pipelines, a general agreement on maximum hydrogen tolerance pertaining to end use (residential appliances) operation needs to be established. Focusing on the combustion performance of two representative models of storage water heaters (conventional and low-NO_x) in California, this research addresses how much H₂ content in natural gas can be tolerated without loss of critical performance parameters with reliable operation. Characteristics like flashback, ignition delay, flame structure, and emissions (NO_x, NO, CO, CO₂, UHC, and NH₃) at different concentrations of H₂ admixed with natural gas is investigated. The present study shows <10% H₂ can be added to natural gas without any loss of efficiency for both the low-NO_x and conventional storage water heater. This work also aims to provide a brief review of burner configuration and emission regulation pertaining to water heating owing to a gap in the literature.     

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.     

Coal-based synthetic natural gas (SNG): A solution to China’s energy security and CO2 reduction?

Considering natural gas (NG) to be the most promising low-carbon option for the energy industry, large state owned companies in China have established numerous coal-based synthetic natural gas (SNG) projects. The objective of this paper is to use a system approach to evaluate coal-derived SNG in terms of life-cycle energy efficiency and CO₂ emissions. This project examined main applications of the SNG and developed a model that can be used for evaluating energy efficiency and CO₂ emissions of various fuel pathway systems. The model development started with the GREET model, and added the SNG module and an end-use equipment module. The database was constructed with Chinese data. The analyses show when the SNG are used for cooking, power generation, steam production for heating and industry, life-cycle energies are 20–108% higher than all competitive pathways, with a similar rate of increase in life-cycle CO₂ emissions. When a compressed natural gas (CNG) car uses the SNG, life-cycle CO₂ emission will increase by 150–190% compared to the baseline gasoline car and by 140–210% compared to an electric car powered by electricity from coal-fired power plants. The life-cycle CO₂ emission of SNG-powered city bus will be 220–270% higher than that of traditional diesel city bus. The gap between SNG-powered buses and new hybrid diesel buses will be even larger—life-cycle CO₂ emission of the former being around 4 times of that of the latter. It is concluded that the SNG will not accomplish the tasks of both energy conservation and CO₂ reduction.     

Analysis of CO2 emissions reduction potential in secondary production and semi-fabrication of non-ferrous metals

Industrial sector growth in developing countries requires the provision of alternatives to guarantee sustainable development. Improving energy efficiency and fuel switching are two measures to reduce CO₂ emissions in the industrial sector, with natural gas and low-carbon electricity as the most feasible options in the short term. In this work, a linear programming optimization model has been developed to study the potential of energy efficiency improvement and fuel substitution for CO₂ emissions reduction, at national level in the non-ferrous metals industry. The energy resource/end-use device allocation problem in secondary metal production and semi-fabrication has been modeled. Using this model, the particular case of Colombia, where low-carbon electricity is available, has been studied. By improving energy efficiency, energy use and CO₂ emissions can be reduced significantly, 73% and 72%, respectively, at negative costs. Further CO₂ emissions reductions, up to 88%, are possible with fuel switching to low-carbon electricity, increasing the costs for the energy system; however, cost reductions caused by energy efficiency improvement outweigh cost increments of fuel switching. Benefits achieved with fuel substitution using low-carbon electricity can be lost if hydropower is not available; in such a case, efficient natural gas-fired end-use devices are preferable.     

Optimization of the design of polygeneration systems for the residential sector under different self-consumption regulations

Polygeneration systems enable natural resources to be exploited efficiently, decreasing CO₂ emissions and achieving economic savings relative to the conventional separate production. However, their economic feasibility depends on the legal framework. Preliminary design of polygeneration systems for the residential sector based on the last Spanish self-consumption regulations RD 900/2015 and RD 244/2019 was carried out in Zaragoza, Spain. Both regulations were applied to individual and collective installations. Several technologies, appropriate for the energy supply to residential buildings, for example, photovoltaics, wind turbines, solar thermal collectors, microcogeneration engines, heat pump, gas boiler, absorption chiller, and thermal and electric energy storage were considered candidate technologies for the polygeneration system. A mixed integer linear programming model was developed to minimize the total annual cost of polygeneration systems. Scenarios with and without electricity sale were considered. CO₂ emissions were also calculated to estimate the environmental impact. Results show that RD 900/2015 discourages the investment in self-consumption systems whereas the RD 244/2019 encourages them, especially in renewable energy technologies. Moreover, in economic terms, it is more profitable to invest in collective self-consumption installations over individual installations. However, this does not necessarily represent a significant reduction of CO₂ emissions with respect to individual installations since the natural gas consumption tends to increase as its unit price decreases because of the increase of its consumption level. Thus, more appropriate pricing of natural gas in residential sector, in which its cost would not be reduced when increasing its consumption, would be required to achieve significant CO₂ emissions reduction. In all cases, the photovoltaic panels (PV) are competitive and profitable without subsidies in self-consumption schemes and the reversible heat pump (HP) played an important role for the CO₂ emissions reduction. In a horizon to achieve zero CO₂ emissions, the net metering scheme could be an interesting and profitable alternative to be considered.     

Estimating the potential for electricity savings in households

Improving efficiency in the use of energy is an important goal for many nations since end-use energy efficiency can help to reduce CO₂ emissions. Furthermore, since the residential sector in industrialised countries requires around one third of the end-use electricity, it is important for policy makers to estimate the scope for electricity saving in households to reduce electricity consumption by using appropriate steering mechanisms. We estimate the level of technical efficiency in the use of electricity using data from a Swiss household survey. We find an average inefficiency in electricity use by Swiss households of around 20 to 25%. Bottom-up economic-engineering models estimate the potential in Switzerland to be around 15%. In this paper we use a sub-vector input distance frontier function based on economic foundations. Our estimates lie at the upper end of the electricity saving potential estimated by the afore-mentioned economic-engineering approach.     

Potential of energy and water efficiency improvement in Abu Dhabi's building sector – Analysis of Estidama pearl rating system

Energy and water infrastructure in Abu Dhabi provides a strong example of the interconnection between energy and water, where the majority of its electricity and water demand is jointly produced from cogeneration plants. The total cost of fuel used for cogeneration plants are heavily depending on the efficiency level of end-use energy and water consumption. Buildings are the major electricity and water consumers with 84.6% and 92.2% respectively from the entire demand. The aim of this study is to analyze the energy and water consumption reduction by implementing Estidama pearl regulations and compare it with Business as Usual -the normal execution of things as they always do-for three sample buildings (villa, multistory residential and office building). For energy assessment, eQUEST software was used to examine the energy performance of the chosen buildings and to evaluate the energy saving potential after applying Estidama requirements. While for water assessment; Estidama and LEED calculation tools were used to do the same. The results of energy simulation and water analysis of the chosen buildings showed a potential of electricity reduction between 31% and 38% and a potential of water reduction between 22% and 36% depending on building type and other parameters. Also, a total monetary savings of 19 Billion AED can be achieved cumulatively over ten years period (2011–2020) after Estidama regulations have been applied. In addition, a reduction of 31.4 Million ton of CO₂eq cumulatively can be achieved.     

District heating and energy efficiency in detached houses of differing size and construction

House envelope measures and conversion of heating systems can reduce primary energy use and CO₂ emission in the existing Swedish building stock. We analysed how the size and construction of electrically heated detached houses affect the potential for such measures and the potential for cogenerated district heating. Our starting point was two typical houses built in the 1970s. We altered the floor plans to obtain 6 houses, with heated floor space ranging between 100 and 306 m². One of the houses was also analysed for three energy standards with differing heat loss rates. CO₂ emission, primary energy use and heating cost were estimated after implementing house envelope measures, conversions to other heating systems and changes in the generation of district heat and electricity. The study accounted for primary energy, including energy chains from natural resources to useful heat in the houses. We showed that conversion to district heating based on biomass, together with house envelope measures, reduced the primary energy use by 88% and the CO₂ emission by 96%, while reducing the annual societal cost by 7%. The choice of end-use heating system was decisive for the primary energy use, with district heating being the most efficient. Neither house size nor energy standard did significantly change the ranking of the heating systems, either from a primary energy or an economic viewpoint, but did affect the extent of the annual cost reduction after implementing the measures.     

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.     

Hydrogen energy deployment in decarbonizing transportation sector using multi-supply-demand integrated scenario analysis with nonlinear programming — A Shanxi case study

Peaking CO₂ emissions and reaching carbon neutrality create a major role for hydrogen in the transportation field where decarbonization is difficult. Shanxi, as a microcosm of China in the systematic transformation of energy end-use consumption, is selected to investigate the hydrogen energy development forecast for decarbonization in the transportation sector. Multi-supply-demand integrated scenario analysis with nonlinear programming (NLP) model is established to analyze hydrogen energy deployment in varied periods and regions under minimum environmental, energy and economic objectives, to obtain CO₂ emission reduction potential. Results reveal that green hydrogen contributes most to low-carbon hydrogen development strategies. In high-hydrogen demand scenarios, carbon emission reduction potential is significantly higher under environmental objectives, estimated at 297.68 × 10⁴–848.12 × 10⁴ tons (2025–2035). The work provides a strategy to forecast hydrogen energy deployment for transportation decarbonization, being of vital significant guide for planning of hydrogen energy transportation in other regions.     

The effect of energy end-use efficiency improvement on China’s energy use and CO2 emissions: a CGE model-based analysis

With its rapid economic growth, China is now confronted with soaring pressure from both its energy supply and the environment. To deal with this conflict, energy end-use efficiency improvement is now promoted by the government as an emphasis for future energy saving. This study explores the general equilibrium effect of energy end-use efficiency improvement on China’s economy, energy use, and CO₂ emissions. This paper develops a static, multisector computable general equilibrium model (CGE) for China, with specific detail in energy use and with the embodiment of energy efficiency. In order to explore the ability of subsidizing non-fossil-generated electricity on moderating potential rebound effects, in this model, the electricity sector was deconstructed into five specific generation activities using bottom–up data from the Chinese electricity industry. The model is calibrated into a 16-sector Chinese Social Accounting Matrix for the year 2002. In the analysis, seven scenarios were established: business as usual, solely efficiency improvement, and five policy scenarios (taxing carbon, subsidized hydropower, subsidized nuclear power, combination of taxing carbon and subsidized hydropower, combination of taxing carbon and subsidized nuclear power). Results show that a sectoral-uniform improvement of energy end-use efficiency will increase rather than decrease the total energy consumption and CO₂ emissions. The sensitivity analysis of sectoral efficiency improvement shows that efficiency improvements happened in different sectors may have obvious different extents of rebound. The three sectors, whose efficient improvements do not drive-up total national energy use and CO₂ emissions, include Iron and Steel, Building Materials, and Construction. Thus, the improvement of energy end-use efficiency should be sectoral specific. When differentiating the sectoral energy-saving goal, not only the saving potential of each sector but also its potential to ease the total rebound should be taken into account. Moreover, since the potential efficiency improvement for a sector over a certain period will be limited, technology measures should work along with a specific policy to neutralize the rebound effect. Results of policy analysis show that one relatively enhanced way is to combine carbon taxing with subsidized hydropower.     

Interactions of energy technology development and new energy exploitation with water technology development in China

Interactions of energy policies with water technology development in China are investigated using a hybrid input-output model and scenario analysis. The implementation of energy policies and water technology development can produce co-benefits for each other. Water saving potential of energy technology development is much larger than that of new energy exploitation. From the viewpoint of proportions of water saving co-benefits of energy policies, energy sectors benefit the most. From the viewpoint of proportions of energy saving and CO₂ mitigation co-benefits of water technology development, water sector benefits the most. Moreover, economic sectors are classified into four categories concerning co-benefits on water saving, energy saving and CO₂ mitigation. Sectors in categories 1 and 2 have big direct co-benefits. Thus, they can take additional responsibility for water and energy saving and CO₂ mitigation. If China implements life cycle materials management, sectors in category 3 can also take additional responsibility for water and energy saving and CO₂ mitigation. Sectors in category 4 have few co-benefits from both direct and accumulative perspectives. Thus, putting additional responsibility on sectors in category 4 might produce pressure for their economic development.     

Driving forces of residential CO2 emissions in urban and rural China: An index decomposition analysis

There exist many differences between urban and rural China among which residential CO₂ emissions arising from energy consumption is a major one. In this paper, we estimate and compare the energy related CO₂ emissions from urban and rural residential energy consumption from 1991 to 2004. The logarithmic mean Divisia index decomposition analysis is then applied to investigate the factors that may affect the changes of the CO₂ emissions. It is found that energy intensity and the income effects, respectively, contributed most to the decline and the increase of residential CO₂ emissions for both urban and rural China. In urban China, the population effect was found to contribute to the increase of residential CO₂ emissions with a rising tendency. However, in rural China, the population effect for residential CO₂ emissions kept decreasing since 1998.     

Quantifying regional economic impacts of CO2 intensity targets in China

To address rising energy use and CO₂ emissions, China's leadership has enacted energy and CO₂ intensity targets under the Twelfth Five-Year Plan (2011–2015), which are defined at both the national and provincial levels. We develop a computable general equilibrium (CGE) model with global coverage that disaggregates China's 30 provinces and includes energy system detail, and apply it to assess the impact of the current binding provincial CO₂ emissions intensity targets. We compare the impact of the provincial targets approach to a single target for China that achieves the same reduction in CO₂ emissions intensity at the national level. The national target assumes trading of emissions allowances across provinces, resulting in the least-cost reductions nationwide. We find that the national target results in about 20% lower welfare loss in China relative to the provincial targets approach. Given that the regional distribution of impacts has been an important consideration in the target-setting process, we focus on the changes in provincial-level CO₂ emissions intensity, CO₂ emissions, energy consumption, and economic welfare. We observe significant heterogeneity across provinces in terms of the energy system response as well as the magnitude of welfare impacts. We further model the current policy of fixed end-use electricity prices in China and find that national welfare losses increase. Assumptions about capital mobility have a substantial impact on national welfare loss, while changing assumptions about the future availability of domestic natural gas resources does not have a large effect.     

Quantitative analysis of energy-efficiency strategy on CO2 emissions in the residential sector in Japan – Case study of Iwate prefecture

This study examines the economics of energy-efficiency strategies for reducing CO₂ emissions in the residential sector in Japan from the perspective of regional characteristics. For this study, the residential sector in Iwate prefecture was selected as representative of rural areas in Japan. In order to promote purchases of energy-efficient consumer appliances, the prefectural government is presumed to reimburse purchasers a part of the cost difference between energy efficient and conventional appliances. This paper begins with a discussion of the prefecture’s financial support for purchasers of energy efficient appliances and assumes that the payments come from prefectural government funds. This paper then looks at the effect of a carbon-tax refund on the reduction of CO₂ emissions. The results show that, if half of the households use energy-efficient appliances, then CO₂ emissions in the residential sector in the year 2020 will decreases from the BAU scenario, 0.726 Mt-C to 0.674 Mt-C. However, the Iwate prefectural government expends $105 million annually, which is 1.5% of the total tax revenue in the year 2003. The carbon-tax refund effectively encourages further reductions in CO₂ emissions. Under the $20/tC carbon tax, proposed by the Ministry of the Environment, the carbon-tax refund leads to a reduction in residential CO₂ emissions from 0.726 Mt-C to 0.712 Mt-C.     

Systemic approach for techno-economic evaluation of triple hybrid (RO,MSF and power generation) scheme including accounting of CO2 emission

A system of models for the techno-economic evaluation of a triple hybrid, reverse osmosis (RO), multistage flush (MSF) and power generation process has been developed. There are three groups of models underlying the system: (A) models describing power-generating technology; (B) models describing RO desalination, and (C) models describing MSF desalination. Any group of individual models, in turn, consists of a set of submodels of different hierarchy levels; they are: (1) technological submodel, (2) fuel or energy submodel, (3) ecological submodel and (4) economic submodel. (1) The technological submodel is focused on the calculation of technological characteristics at different operating loads of the generating systems; (2) the fuel or energy submodel covers the calculation of fuel influx into power-generating systems at different operating loads; (3) the ecological submodel focuses on estimation of CO₂ emissions at different operating regimes; (4) the economic submodel gives values of economic indicators, such as (a) cost of water, (b) cost of energy, and (c) accounting for CO₂ emissions through imposed carbon tax (assuming rates of environmental taxes recommended by European Union tax legislation). This paper contains an analysis of the behavior of economic and ecological indicators for various technological parameters and economic assumptions, such as (1) load, specific fuel consumption and efficiency of the energy generating system, (2) specific energy consumption for desalination, (3) specific emissions of CO₂, and (4) taxes on CO₂ emissions. The model presented can be applied for the analysis of schemes where seasonal surplus of unused power is utilized by RO which are characterized by higher efficiency of fuel consumption and decreasing specific CO₂ emissions.