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Abstract Based on the periodic solution of the heat conduction equation, an analysis has been developed to study the thermal performance of a simple domestic solar water-heating system consisting of a thermal-trap solar-energy collector, connected to a water tank. To study the effects of typical parameters such as the thickness of the trap material and the presence/absence of the glass cover on the thermal performance, numerical calculations have been performed to correspond to the daily variations of the ambient temperature and solar intensity on a typical cold winter day in New Delhi.

As one of the three high-energy consumption sectors (industry, building, and transportation) in China, the transport sector faced a devastating resource and environment challenge. The transport sector was reportedly responsible for about 15.9% of the country’s total final energy consumption in 2008. This paper investigates the energy consumption and efficiency of China’s transport sector from 2003 to 2009. The transport energy data of 30 China administrative regions were divided into “three-belts” (Eastern, Western, and Central areas), and the corresponding turnovers were reported and analyzed using an index decomposition analysis (Logarithmic Mean Divisia Index). The energy data and turnover of the transport sector indicated that the high growth rate of turnover results is attributed to the high growth rate of diesel, assuming that diesel is the major fuel for freight transport. The growth of diesel is the main contributor to the overall growth of energy consumption. The growth rate of gasoline has become minimal since 2006. Since 2005, all three-belt areas, with regard to the effectiveness of energy conservation policies, have continuously improved their energy efficiencies based on the results of decomposition analysis. The energy intensity effect shows that the energy conservation and efficiency policies were more effective in the Central and Western areas than that in the Eastern area. On the other hand, the regional shift effect indicates that the policies favor to the Eastern area since only its regional shift effect contributes energy savings since 2008. The energy-mix effect is insignificant, which indicates that it is not necessary to conduct CO2 emission decomposition analysis due to the redundant observations. At last, the activity effect dominates the energy consumption increase (98.05% of the accumulated total energy increase) from 2003 to 2009, which is consistent with the rapid development of transportation in China. That is, the policies in the transport sector mainly focused on the economic development but the energy efficiencies in the study period.

Abstract The deep decarbonisation of the power sector coupled with electrification of end-use sectors will be crucial towards a carbon neutral economy, as required to achieve the Paris Agreement's goal. Several studies have highlighted the relevance of electrification under deep decarbonisation. However, previous work does not explore what would be the major shifts towards electrification, i.e., in what economic activities it will likely occur and when up to 2050 considering gradually stricter GHG emissions constraints. This is of upmost relevance since relatively small variations in emission caps may trigger substantial modifications in specific components of the energy system, namely the shift for the electrification of a particular energy end-use, with impacts on the power sector’s portfolio. In this paper, we analyse the extension of the electrification of the energy system as a cost-effective strategy for deep decarbonisation. We set a large number of increasingly stringent mitigation caps to assess: (i) the degree of electrification of different energy end-uses across all economic activities, (ii) the impact in power sector portfolio and costs and (iii) investment needs. The novelty of this paper relies on the anticipation of electrification of activities traditionally supplied by non-electricity energy carriers, by exploring when and how such transformation may occur in the future, and how much it would cost. We assess the case of Portugal till 2050 by using the TIMES_PT model to generate 50 increasingly stricter decarbonisation scenarios. In the long term, incremental changes (+1%) in more aggressive decarbonisation targets (beyond −70% reduction) induce substantial increase in the share of electrification growth rates. Electric private vehicles, electricity-based steam and heat production in ceramic industrial sector and heat pumps in buildings are the most cost-effective electric technologies. We found that a decarbonisation up to near −80% of 1990′s levels of the Portuguese energy system does not have a significant impact on the power sector unit costs, and does not surpass historic values for some years. However, it should be noted that incremental changes (+1%) in more aggressive decarbonisation targets may increase sharply electricity costs in 2050 (+9%). Thus, focusing in only few scenarios may narrow the role of electrification (or other mitigation options) and its associated costs for deep decarbonisation. This paper allows researchers, planners and decision makers to enhance awareness regarding the relevance and cost-effectiveness of electrification under decarbonisation, namely its feasibility and affordability, providing fruitful insights.

Abstract Carbon capture and storage (CCS) technology is an important option in the portfolio of emission mitigation solutions in scenarios that lead to deep reductions in greenhouse gas (GHG) emissions. We focus on CCS application in hard-to-abate sectors (cement industry, iron and steel, chemicals) and introduce industrial CCS options into the MIT Economic Projection and Policy Analysis (EPPA) model, a global multi-region multi-sector energy-economic model that provides a basis for the analysis of long-term energy deployment. We use the EPPA model to explore the potential for industrial CCS in different parts of the world, under the assumptions that CCS is the only mitigation option for deep GHG emission reductions in industry and that negative emission options are not available for other sectors of the economy. We evaluate CCS deployment in a scenario that limits the increase in average global surface temperature to 2 °C above preindustrial levels. When industrial CCS is not available, global costs of reaching the target are higher by 12% in 2075 and 71% in 2100 relative to the cost of achieving the policy with CCS. Overall, industrial CCS enables continued growth in the use of energy-intensive goods along with large reductions in global and sectoral emissions. We find that in scenarios with stringent climate policy, CCS in the industry sector is a key mitigation option, and our approach provides a path to projecting the deployment of industrial CCS across industries and regions.

Abstract In recent years, distributed energy systems (DESs) have been recognized as a promising option for sustainable development of future energy systems, and their application has increased rapidly with supportive policies and financial incentives. With growing concerns on global warming and depletion of fossil fuels, design optimization of DESs through economic assessments for short-run benefits only is not sufficient, while application of exergy principles can improve the efficiency in energy resource use for long-run sustainability of energy supply. The innovation of this paper is to investigate exergy in DES design to attain rational use of energy resources including renewables by considering energy qualities of supply and demand. By using low-temperature sources for low-quality thermal demand, the waste of high-quality energy can be reduced, and the overall exergy efficiency can be increased. The goal of the design optimization problem is to determine types, numbers and sizes of energy devices in DESs to reduce the total annual cost and increase the overall exergy efficiency. Based on a pre-established DES superstructure with multiple energy devices such as combined heat and power and PV, a multi-objective linear problem is formulated. In modeling of energy devices, the novelty is that the entire available size ranges and the variation of their efficiencies, capital and operation and maintenance costs with sizes are considered. The operation of energy devices is modeled based on previous work on DES operation optimization. By minimizing a weighted sum of the total annual cost and primary exergy input, the problem is solved by branch-and-cut. Numerical results show that the Pareto frontier provides good balancing solutions for planners based on economic and sustainability priorities. The total annual cost and primary exergy input of DESs with optimized configurations are reduced by 21–36% as compared with conventional energy supply systems, where grid power is used for the electricity demand, and gas-fired boilers and electric chillers fed by grid power for thermal demand. A sensitivity analysis is also carried out to analyze the influence of energy prices and energy demand variation on the optimized DES configurations.

The design of transition pathways for sustainable electricity systems with high penetrations of renewable energy sources requires the use of energy modeling tools that are able to account for two key aspects: the evolution of fossil fuels and technology prices, and the natural dynamics of renewable resources. However, the modeling methodologies most currently used focus on only one of these two aspects, which hinders their suitability for performing long-term analysis with high penetrations of renewable energy sources. This paper presents a modeling framework that is able to optimize the investment in new renewable generation capacity on the long-term while taking into account the hourly dynamics of electricity supply and demand. The framework combines two of the most used energy planning tools, each able to account for one of the aspects of the modeling of energy systems. The framework was applied to continental Portugal for the time period of 2005–2050, in order to identify optimal investment plans in new renewable and fossil generation capacity with the goal of achieving significant CO2 emissions reduction, under different scenarios. The results show that the inclusion of dynamics in the modeling methodology can help avoid overinvestment and reduce the excess of electricity from renewable energy sources that cannot be used by the system. These results can have a significant impact on the design of a sustainable electricity system and may lead to a diversification of the energy sources used.

Abstract To meet the needs of fuel security and combat the growing concerns of CO2 emissions, the automotive industry is seeking solutions through biofuels. Traditionally, when supplying biofuel blends to the combustion chamber, the blend is mixed externally prior to its injection in one location. This location occurs either before the cylinder (port-fuel injection, PFI), or directly into the cylinder (direct-injection, DI). However, the use of dual-injection allows the in-cylinder blending of two fuels at any blend ratio, when combining the two locations (PFI and DI). This injection strategy offers increased flexibility as the blend ratio can be changed instantaneously according to engine speed and load demand and fuel availability. Previous work by the authors has reported the improved combustion performance of dual-injection with 25% blends (in gasoline) of a new biofuel candidate: 2,5-dimethylfuran (DMF). This current investigation extends the analysis to include the gaseous emissions of various DMF blends (25%, 50% and 75%) from 3.5 bar to 8.5 bar IMEP and the particulate matter (PM) emissions of similar fraction ethanol blends at a selected condition of 5.5 bar IMEP. Compared to DI, dual-injection offers reduced CO and CO2 emissions and comparable HC emissions. The mean PM diameter is decreased and the accumulation mode particles are negligible compared to DI. However, the implication of the higher combustion pressures is an increase in NOx due to reduced charge-cooling.

Abstract In this paper, an open source tool is introduced to represent urban energy infrastructure in the City of Philadelphia, and different renewable energy scenarios are compared with respect to minimization of the standard deviation of the residual load. Renewable energy sources play a critical role in the world’s ongoing energy transition in response to climate change. Urban Energy Systems may be particularly sensitive to this transition due to the high energy demand density associated with urban environments. Open energy analysis and modeling tools can provide important information that can be used by urban energy planners, policy makers, and other stakeholders during this transition. In the present study, we apply FlexiGIS, an open energy modeling tool developed in a European context, to a case study in the City of Philadelphia. Due to the importance of open access to energy data, we pay particular attention to open energy data sources. Notably, OpenStreetMap was incomplete in its spatial coverage, but alternate open data resources were identified. This work conducts an optimization of the renewable energy mix to minimize the amount of balancing energy required for the residual load. We observe that Philadelphia has an optimal mix of renewables that favors a roughly even share of wind and solar, but that, compared to a previous case study in Oldenburg, Germany, requires more balancing energy at comparable levels of renewable penetration.

A continuous growth of international trade, especially between developing countries, has greatly increased carbon dioxide (CO2) emissions associated with energy consumption over the past two decades. Given the more intensified intraregional cooperation and trade within the Belt and Road Initiative (BRI), this study aims to trace the imbalance of CO2 embodied in trade between nations in BRI and the rest of the world, providing new insights into the drivers of emissions growth by contrasting consumption, production and technological differences-based perspectives. Results indicate that the BRI contributed to over 50% of global carbon footprint and 92% of its increase in 1995–2015. The BRI was a net exporter of trade-embodied emissions, whose technological-adjusted carbon footprint remained remarkably large due to comparatively high carbon intensity. Geographically, carbon leakage has gradually moved from China and India to other BRI countries, especially to Southeast Asia, West Asia and Africa. Technological change was the key driver of emissions reduction, followed by the change in industrial structure. The growth in final demand per capita was the most important driver for the growth of CO2 emissions in BRI. Improving carbon efficiency remains a critical step for BRI nations to slow down not only emissions growth but also carbon leakage. The paper managed to provide novel insights into the carbon leakage in BRI by contrasting the consumption, production and technological differences-based perspectives, thus being able to better inform policymakers on region-specific low-carbon transition and global climate governance.