Stock Turnover Model Research Articles

Coordinating the electric vehicle transition and electricity grid decarbonization in the U.S. is not essential to achieving substantial long-term carbon dioxide emissions reductions

How quickly the US can decarbonize light-duty vehicle (LDV) transportation depends on the rates of change of electric vehicle (EV) sales, stock turnover, and grid decarbonization. We build a stock turnover model to assess how sensitive achieving 2050 LDV decarbonization targets is to these rates. We estimate carbon dioxide (CO2) reductions of 70%–85% by 2050, including emissions from vehicles and upstream electricity generation, provided that new vehicle sales transition to 100% EVs and substantial grid decarbonization are accomplished by 2050. This result is robust to continuation of long-term trends of increasing vehicle longevity, and to whether the timing of EV sales growth and grid decarbonization are coordinated. If the two key goals are met, the annual contribution of EV electricity use to CO2 emissions will be small over the entire period.

Embodied carbon emissions and mitigation potential in China's building sector: An outlook to 2060

In China's building sector, annual embodied carbon emissions (EC) account for a larger proportion than operational emissions, unlike in developed economies. Investigating future EC trajectories, possible abatement potential, and roadmaps can better guide the low-carbon development of the building sector to tackle climate change. This study proposes a bottom-up building EC model, based on the dynamic building stock turnover model and process-based life cycle assessment model, to simulate China's building EC by 2060 under different policy scenarios. The abatement potential of various factors is discussed through the decomposition model and supplementary scenarios. Results indicate that building EC have reached the peak plateau, and by 2060, under the baseline scenario, will be 49% lower than 2020 levels. There is huge room for emission reduction, and the cumulative mitigation ranges from 20.9 to 45.3 billion tCO2 for alternative development scenarios between 2021 and 2060. New building area and material emission factors are the greatest contributors to mitigation potential. Therefore, controlling construction scale and reducing material supply-side emissions are critical strategies for alleviating building EC. Moreover, measures to extend the reasonable service life of existing and new buildings should be implemented as soon as possible to decrease unnecessary waste and emissions.

Quantification of the carbon emission of urban residential buildings: The case of the Greater Bay Area cities in China

Building sector plays a significant role in China's ambitous climate targets to peak carbon emissions (CEs) by 2030 and to realize carbon neutral by 2060. However, studies in characterizing the CEs of urban residential buildings from life-cycle perspective at regional level are still limited, especially for the Guangdong-Hong Kong-Macao Greater Bay Area (GBA) in China. Here, life cycle assessment method and improved building stock turnover model were employed to quantify the annual CEs of urban residential buildings (including materialization CEs of the newly-built urban residential buildings, operational CEs of the existing urban residential buildings, and CEs generated from the demolition of the existing urban residential buildings) in GBA cities from 2000 to 2018. The results show that the total CEs increased dramatically from 44.5 Mt. CO2 e in 2000 to 75.1 Mt. CO2 e in 2018 with an annual growth rate by approximately 3%. The CEs from operation stage accounted for around 70%, and recycling building wastes could reduce 7.5% emissions. Compared with other bay areas globally, the operational CEs of urban residential building in GBA became the highest since 2014. Therefore, climate actions in energy saving and emission mitigation are required. Based on scenario analysis, we estimated that Huizhou city can reach the peak target by 2020 if taking some effective measures. These emission findings could provide data references and suggestions for the low-carbon development path for urban residential buildings in GBA and other global cities.

Forecasting urban residential stock turnover dynamics using system dynamics and Bayesian model averaging

Knowing the size of building stock is perhaps the most basic determinant in assessing energy use in buildings. However, official statistics on urban residential stock for many countries are piecemeal at best. Previous studies estimating stock size and energy use make various debateable methodological assumptions and only produce deterministic results. This paper presents a Bayesian approach to characterise stock turnover dynamics and estimate stock size uncertainties, applied here to China. Firstly, a probabilistic dynamic building stock turnover model is developed to describe the building aging and demolition process, governed by a hazard function specified by a parametric survival model. Secondly, using five candidate parametric survival models, the building stock turnover model is simulated through Markov Chain Monte Carlo to obtain posterior distributions of model-specific parameters, estimate marginal likelihood, and make predictions of stock size. Thirdly, Bayesian Model Averaging is applied to create a model ensemble that combines model-specific posterior predictive distributions of the recent historical stock evolution pathway in proportion to posterior model probabilities. Finally, the Bayesian Model Averaging model ensemble is extended to forecast future trajectories of residential stock development through 2100. The modelling results suggest that the total stock in China will peak around 2065, at between 42.4 and 50.1 billion m2. This Bayesian modelling framework produces probability distributions of annual total stock, age-specific substocks, annual new buildings and annual demolition rates. This can support future analysis of policy trade-offs across embodied-versus-operational energy consumption, in the context of sector-wide decarbonisation.

The Role of Powertrain Electrification in Achieving Deep Decarbonization in Road Freight Transport

Decarbonizing road freight transport is difficult due to its reliance on fossil fuel internal combustion engine vehicles (ICEVs). The role of powertrain electrification in achieving deep decarbonization in road freight transport was studied using a vehicle stock turnover model, focusing on Japan. Twelve vehicle types were considered; combining four powertrains, ICEV, hybrid electric vehicle (HEV), battery electric vehicle (BEV) and fuel cell electric vehicle (FCEV); and three vehicle size classes, normal, compact and mini-sized vehicles. A scenario-based approach was used; considering a Base scenario, and three alternative scenarios targeting powertrain electrification. Between 2012 and 2050, tank to wheel CO2 emissions decrease 42.8% in the Base scenario, due to the reduction of vehicle stock, the improvement of vehicle fuel consumption and the adoption of HEVs. Diffusion of FCEVs in normal vehicles and BEVs in compact and mini-sized vehicles achieves the largest tank to wheel CO2 emissions reductions, up to 44.6% compared with the 2050 baseline value. The net cash flow is positive over the whole time horizon, peaking at 6.7 billion USD/year in 2049 and reaching 6.6 billion USD/year by 2050. Powertrain electrification is not enough to achieve any of the CO2 emissions reduction targets in road freight transport.

A statistics-based method to quantify residential energy consumption and stock at the city level in China: The case of the Guangdong-Hong Kong-Macao Greater Bay Area cities

The residential sector is a substantial consumer of energy worldwide, especially in China, and therefore a focus of energy conservation efforts. Although cities are basic executive units nowadays, their residential energy consumption (REC) is often overlooked. By revealing this research gap, we develop a REC calculation model at the city level (CRECM) and an improved residential stock turnover model (RSTM) to calculate the REC and residential stock of Guangdong-Hong Kong-Macao Greater Bay Area (GBA) cities. Based on these two indicators, the REC intensity is quantified to measure residential energy efficiency. The results show that 11 GBA cities see a dramatic increase in REC over the past 16 years and REC intensities of most cities have plateaued out. The total REC of GBA is expected to rise until that of Guangzhou and Shenzhen reaches the peak. Also, the over residential stock of GBA has tended to saturation in recent years after significant growth, while some cities (i.e. Zhuhai, Huizhou, and Zhongshan) tend to increase. The gaps in REC among cities can be attributed to socio-economic factors (population, GDP, and residential stock) and building characteristics (unit area and construction vintage). Both CRECM and RSTM proposed in this study can provide robust data support for developing building energy efficiency policies for GBA cities as well as other cities across the country

China's building stock estimation and energy intensity analysis

Reliable and objective data regarding building stock is essential for predicting and analyzing energy demand and carbon emission. However, China's building stock data is lacking. This study proposes a set of China building floor space estimation method (CBFSM) based on the improved building stock turnover model. Then it measures China's building stocks by vintage and type from 2000 to 2015, as well as building energy intensity (national level and provincial level) and energy-efficient buildings. Results showed that total building stocks increased significantly, rising from 35.2 billion m2 in 2000 to 63.6 billion m2 in 2015, with the average growth rate 4.0%. The deviations were well below 10% by comparing with China Population Census, which validated the reliability of CBFSM and the results. As for energy intensity, urban dwellings and rural dwellings showed relatively stable and increasing trend respectively. The commercial building energy intensity saw a downward trend during “12th Five Year Plan” period. This indicated the effectiveness of building energy efficiency work for commercial buildings since 2005.38.6 billion m2 residential dwellings and 5.7 billion m2 commercial buildings still need to be retrofitted in future. CBFSM can overcome shortages in previous studies. It can also provide Chinese government with technical support and data evidence to promote the building energy efficiency work.

Estimating urban residential building-related energy consumption and energy intensity in China based on improved building stock turnover model

Accurate estimation of urban residential building-related energy consumption (URBEC) and energy intensity per unit floor area at the national level has significant implications for the analysis of carbon emission peaks. However, reliable data on China's building floor space (BFS) are lacking, resulting in unclear energy intensity levels. This study proposes a China BFS estimation method (CBFSEM) based on improved building stock turnover model. Using CBFSEM, it estimates the BFS of historic urban dwelling stock, the demolished and newly built dwelling from 2000 to 2015. It then estimates the corresponding energy consumption and intensity based on the obtained urban residential BFS data. Results showed that total URBEC in China increased dramatically from 217.1 Mtce in 2000 to 417.2 Mtce in 2015 with an average annual growth rate of 4.45%. China's total dwelling stock almost doubled, from 10.6 billion m2 in 2000 to 27.4 billion m2 in 2015 with an annual growth rate of 6.56%. The operational energy consumption accounted for approximately 70% of total URBEC and the building material production energy intensity was the highest in total URBEC, >60 kgce/m2. A comparison with the China Population Census showed that the deviations were well below 8%, which indicated the reliability of the CBFSEM and the estimated results. In general, this study fills the gap in available data and addresses the shortage of estimation methods for BFS and energy intensity. It also provides the government with technical support and scientific evidence to promote building energy efficiency.

Energy consumption and CO2 emissions reduction potential of electric-drive vehicle diffusion in a road freight vehicle fleet

Road freight transport is dominated by gasoline- and diesel- fueled internal combustion engine vehicles, presenting a challenge for decarbonization. There is a growing interest in electric-drive vehicles as alternative to reduce CO2 and local pollutant emissions in road freight transport. In this research, a vehicle stock turnover model is used to estimate the potential of electric-drive vehicles to reduce energy consumption and CO2 emissions in a road freight vehicle fleet; focusing on Japan as a case of study. In the Base scenario, tank to wheel CO2 emissions are reduced 51.9% between 2012 and 2050 driven by vehicle stock reduction, hybrid electric vehicle diffusion and vehicle fuel consumption improvement. By 2050, tank to wheel CO2 emissions can be reduced up to 55.8% with the diffusion of battery electric vehicles and fuel cell electric vehicles. Despite of aggressive electric-drive vehicle deployment, fossil fuels account for more than 52% of the energy consumed in all scenarios in 2050.

Scenarios to decarbonize residential water heating in California

This paper presents the first detailed long-term stock turnover model to investigate scenarios to decarbonize the residential water heating sector in California, which is currently dominated by natural gas. We model a mix of water heating (WH) technologies including conventional and on-demand (tank-less) natural gas heating, electric resistance, existing electric heat pumps, advanced heat pumps with low global warming refrigerants and solar thermal water heaters. Technically feasible policy scenarios are developed by considering combinations of WH technologies with efficiency gains within each technology, lowering global warming potential of refrigerants and decreasing grid carbon intensity. We then evaluate energy demand, emissions and equipment replacement costs of the pathways. We develop multiple scenarios by which the annual greenhouse gas emissions from residential water heaters in California can be reduced by over 80% from 1990 levels resulting in an annual savings of over 10 Million Metric Tons by 2050. The overall cost of transition will depend on future cost reductions in heat pump and solar thermal water heating equipment, energy costs, and hot water consumption.

Scenario analysis of lightweight and electric-drive vehicle market penetration in the long-term and impact on the light-duty vehicle fleet

Electric-drive vehicles, including hybrid electric vehicles, plug-in hybrid electric vehicles, battery electric vehicles, fuel cell electric vehicles and fuel cell hybrid electric vehicles, are emerging as less polluting alternatives to internal combustion engine vehicles. Therefore, it is important to assess their penetration in the vehicle market in the future. A ‘two-step’ approach is used to estimate the optimum market penetration of lightweight and electric-drive vehicles in the long-term and the impact on the light-duty vehicle fleet, focusing on Japan. First, an optimization model is used to estimate the vehicle market composition in 2050. Then, a vehicle stock turnover model is used to estimate light-duty vehicle fleet energy and material consumption, CO2 emissions and cost. Internal combustion engine vehicles and hybrid electric vehicles dominate in the Base scenario. Fuel cell hybrid electric vehicles dominate when low cost is prioritized. Shift to battery electric vehicles occurs when low CO2 emissions are prioritized. CO2 emissions are reduced 56.9% between 2012 and 2050 in the Base scenario. Lightweight mini-sized battery electric vehicle diffusion has the largest CO2 emissions reductions, 87.3% compared to the 2050 baseline value; with the net cash flow peaking at 10.2 billion USD/year in 2035 and becoming negative after 2044.

Impact of new vehicle market composition on the light-duty vehicle fleet CO2 emissions and cost

Internal combustion engine vehicles dominated road transport during the twentieth century. Nevertheless, the panorama is likely to change in the future, with electric-drive vehicle sales increasing due to technology improvement, cost reduction, infrastructure development and increasing environmental awareness. A new vehicle market model and a vehicle stock turnover model were combined to estimate the optimum composition of the 2050 new vehicle market in Japan under different scenarios; and the impact of changes in the new vehicle market composition on the light-duty vehicle fleet. The Base scenario is dominated by internal combustion engine vehicles and hybrid electric vehicles. Fuel cell hybrid electric vehicles dominate when low cost is prioritized; while shift to battery electric vehicles occurs when low CO2 emissions are prioritized. CO2 emissions are reduced 56.9% between 2012 and 2050 in the Base scenario. Diffusion of lightweight mini-sized battery electric vehicles has the largest CO2 emissions reductions, 87.3% compared with the 2050 baseline value; with negative cash flow after 2044.

Energy, environmental and economic impact of mini-sized and zero-emission vehicle diffusion on a light-duty vehicle fleet

Diffusion of battery electric vehicles and fuel cell hybrid electric vehicles can contribute to reduce passenger light-duty vehicle fleet CO2 emissions. However, barriers such as higher vehicle capital cost and lack of electricity and hydrogen infrastructure prevent their deployment. A vehicle stock turnover model was used to assess the impact of mini-sized and zero-emission vehicle diffusion on passenger light-duty vehicle fleet energy and material consumption, CO2 emissions and cost, focusing on Japan. 2050 passenger light-duty vehicle fleet energy consumption and tank-to-wheel CO2 emissions in the base scenario are 48.7 and 51.9% lower than the 2012 values. Diffusion of mini-sized and battery electric vehicles provides the largest energy consumption and CO2 emissions reductions, 64.7, and 87.8% compared with the 2050 baseline values. Incremental cost of zero emission vehicles is reduced through downsizing. The 2050 net cash flow for battery electric vehicles diffusion is reduced from 15.9 to −16.7billion USD/year if downsizing is applied; while in the case of fuel cell hybrid electric vehicle diffusion, downsizing reduces the 2050 net cash flow from −12.5 to −47.8billion USD/year. Thus, shifting to mini-sized zero emission vehicles provides the quadruple benefit of reducing energy and material consumption, CO2 emissions and cost.

Building stock dynamics and its impacts on materials and energy demand in China

China hosts a large amount of building stocks, which is nearly 50 billion square meters. Moreover, annual new construction is growing fast, representing half of the world's total. The trend is expected to continue through the year 2050. Impressive demand for new residential and commercial construction, relative shorter average building lifetime, and higher material intensities have driven massive domestic production of energy intensive building materials such as cement and steel. This paper developed a bottom-up building stock turnover model to project the growths, retrofits and retirements of China's residential and commercial building floor space from 2010 to 2050. It also applied typical material intensities and energy intensities to estimate building materials demand and energy consumed to produce these building materials. By conducting scenario analyses of building lifetime, it identified significant potentials of building materials and energy demand conservation. This study underscored the importance of addressing building material efficiency, improving building lifetime and quality, and promoting compact urban development to reduce energy and environment consequences in China.

Impact of powertrain electrification, vehicle size reduction and lightweight materials substitution on energy use, CO2 emissions and cost of a passenger light-duty vehicle fleet

Electric-drive and lightweight vehicles can reduce CO2 emissions in road passenger transportation. However, maximum reductions are limited by the extent of their diffusion. A vehicle fleet stock turnover model was developed to study the impact of powertrain electrification, vehicle size reduction and lightweight materials substitution on light-duty vehicle fleet energy consumption, CO2 emissions and cost; and used in the case of Japan. Vehicle types included internal combustion engine vehicles, hybrid electric vehicles, battery electric vehicles, and fuel cell hybrid electric vehicles; using two glider types, conventional and lightweight; available in three vehicle size classes, normal, compact and mini-sized vehicles. Diffusion of mini-sized lightweight battery electric vehicles has the largest potential for tank-to-wheel energy consumption and CO2 emissions reductions, 70.6 and 92.2%, compared to the 2050 baseline values; with a net cash flow larger than zero until 2045. In contrast, diffusion of mini-sized lightweight fuel cell hybrid electric vehicles has the lowest net cash flow by 2050, with negative values from 2033 and potential tank-to-wheel energy consumption and CO2 emissions reductions of 55.4 and 82.9% compared to the 2050 baseline values. Lightweighting reduces significantly the capital cost of battery electric vehicles and fuel cell hybrid electric vehicles, favoring their deployment.

Techno-economic assessment of lightweight and zero emission vehicles deployment in the passenger car fleet of developing countries

The largest increment in the global light-duty vehicle fleet in the medium- and long-term will happen in developing countries. Advanced vehicles can outweigh increments in CO2 emissions of a growing vehicle fleet; however, cost remains a barrier for their diffusion. A stock turnover model of the passenger car fleet was developed to estimate the potential of advanced vehicle deployment for CO2 emissions reduction, and used in the case of Colombia. Vehicle types included internal combustion engine vehicles (ICEVs), battery electric vehicles (BEVs) and fuel cell hybrid electric vehicles (FCHEVs); using two glider types: conventional and lightweight materials-intensive. Five scenarios were considered: the base scenario that relies on conventional ICEVs, and four alternative scenarios targeting the penetration of (A) BEVs, (B) BEVs and lightweight vehicles, (C) FCHEVs, and (D) FCHEVs and lightweight vehicles. Deployment of BEVs and lightweight vehicles offers the largest cumulative well-to-wheel CO2 emissions reductions, 22.01% compared to the base scenario; with cost of avoided CO2 going from 930USD/t-CO2 avoided in 2020 to 31USD/t-CO2 avoided in 2050. Despite advanced vehicle deployment, gasoline will be the main fuel and iron and steel the main materials until 2050 in the Colombian passenger car fleet.

Global climate-oriented building energy use scenarios

This paper explores the extent to which global fuel use in buildings could be reduced, and the growth in global electricity use in buildings limited, by applying stringent (factor of 3–4) improvements to recent building codes for new buildings worldwide and large (factor of 2–3) reductions in the energy use of existing buildings through renovations. The analysis is carried out for 10 different socio-economic regions of the world, taking into account existing building stock and energy intensities in each region and projected changes in population and income, which in most parts of the world will drive large increases in building floor area. A stock turnover model is applied to project changes in heating, cooling, service hot water (SHW) and non-thermal electricity demand with various rates of improvement in standards for new and renovated buildings, and various rates of renovation and demolition of existing buildings. For a scenario in which population peaks at about 9 billion and global average per capita GDP increases to twice the 2010 value by 2100, the global fuel demand could be reduced by a factor of four while limiting maximum annual electricity demand to twice the 2010 value.

Long-Term Potential to Reduce Emissions from International Shipping by Adoption of Best Energy-Efficiency Practices

Maritime shipping is highly fuel-efficient, but its sheer volume and rapid growth make it a major source of carbon emissions. Industry and governments seek to reduce the energy use and carbon footprint of shipping. Yet the reasons for the variation in shipping efficiency observed in the world fleet's embrace of best technical and operational practices to increase efficiency remain unexplained. The research reported in this paper offers a novel analysis that connected 2011 in-use fleet characteristics, first-ever global satellite data on ship movement, and technical literature on ship efficiency technology to assess the long-term prospects of increased shipping efficiency. This study also investigated how each ship characteristic influenced the efficiency of the shipping fleet. A ship stock turnover model was developed to track technical and operational efficiency practices in ships independently. The findings indicated that industry-leading ships were about twice as efficient as industry laggards across major ship types. If the available technical and in-use practices of the low-carbon industry leaders of today were fully embraced, the potential would exist to reduce carbon dioxide in absolute terms by more than 300 million metric tonnes by 2040, even while business-as-usual freight movement doubled. On the basis of the data in this assessment, the potential exists to develop a tool for shippers to quantify, evaluate, and compare their supply chain carbon footprints in a manner that does not rely on more aggregated fleet-average simplifications. The methodology, data, and findings of this study should benefit industry as it looks for ways to reduce energy consumption; researchers, who are examining ship operation; and policy makers, who want to curb the climate impact of international shipping.

Recent advances in automotive technology and the cost-effectiveness of fuel economy improvement

The potential for improving the fuel economy of conventional, gasoline-powered automobiles through optimized application of recent technology advances is analyzed. Results are presented at three levels of technical certainty, ranging from technologies already in use to technologies facing technical constraints (such as emissions control problems) which might inhibit widespread use. A fleet-aggregate, engineering-economic analysis is used to estimate a range of U.S. new car fleet average fuel economy levels achievable given roughly 10 years of lead time. Technology cost estimates are compared to fuel savings in order to determine likely cost-effective levels of fuel economy, which are found to range from 39 miles per gallon to 51 miles per gallon depending on technology certainty level. The corresponding estimated increases in average new car price range from $540 to $790 (1993$). Estimated fuel savings payback times average less than 3 years and the cost of conserved energy averages $0.50 per gallon, indicating that these levels of fuel economy improvement are cost-effective over a vehicle lifetime. A vehicle stock turnover model is used to project the reductions in gasoline consumption and associated emissions that would follow if the estimated fuel economy levels are achieved. Potential trade-offs regarding vehicle performance, safety, and emissions are also discussed.