The status and prospects of renewable energy for combating global warming

Reducing anthropogenic greenhouse gas (GHG) emissions in material quantities, globally, is a critical element in limiting the impacts of global warming. GHG emissions associated with energy extraction and use are a major component of any strategy addressing climate change mitigation. Non-emitting options for electrical power and liquid transportation fuels are increasingly considered key components of an energy system with lower overall environmental impacts. Renewable energy technologies (RETs) as well as biofuels technologies have been accelerating rapidly during the past decades, both in technology performance and cost-competitiveness — and they are increasingly gaining market share. These technology options offer many positive attributes, but also have unique cost/benefit trade-offs, such as land-use competition for bioresources and variability for wind and solar electric generation technologies. This paper presents a brief summary of status, recent progress, some technological highlights for RETs and biofuels, and an analysis of critical issues that must be addressed for RETs to meet a greater share of the global energy requirements and lower GHG emissions.     

Socio-technological impact analysis using an energy IO approach to GHG emissions issues in South Korea

Through energy input–output (E-IO) analyses from 1985 to 2005, the changes in three factors affecting GHG emissions in South Korea were analyzed. Based on the E-IO results, the changes in the direct and total (embodied) GHG emissions from the pertinent sectors were decomposed into three factors—the energy consumption effect, the social effect, and the technological effect—using the Sato-Vartia index for the three periods of 1985–1995, 1995–2000, and 2000–2005. The decomposition analysis demonstrated that a total emission matrix including both direct and indirect GHG emissions showed an evolution pattern that was very similar to the changes in direct GHG emissions; however, ripple effects were observed in the case of emissions from sector #-59 (Synthetic resins, synthetic rubber-p). The results showed that national energy policies such as those pertaining to the diversification of energy sources, shifts in the energy consumption structure (social effect), and the transformation to a low-carbon energy economy (technology effect) were effective. Finally, several limitations of the Divisia decomposition analysis were pointed out.     

Policy progress in mitigation of climate change in Taiwan

To make an active contribution to the global effort in mitigation of climate change, Taiwan government has implemented the “Frameworks for Sustainable Energy Policy—An Energy-Saving and Carbon-Reduction Action Plan” in June 2008. It has made a commitment of a stepwise reduction of nationwide greenhouse gas (GHG) emissions, which returns the nationwide GHG emission to 2008 levels by 2020, then reduces to 2000 levels by 2025, and finally cuts 50% of 2000 levels by 2050. The fundamental strategy is to reduce the GHG emission under acceptable economic development and energy security to achieve generation-spanning triple-win in energy, environment and economy. The major policy instruments such as “Statute for Renewable Energy Development”, “GHG Reduction Law (draft),” “Regulation for Energy Tax (draft),” and “Energy Management Act” have been either implemented or scheduled for legislative reviewing. The purpose of this paper is to present an updated review of the outcomes of GHG emission reduction in Taiwan. In addition, the progress and priority of policy instruments in GHG emission reduction are analyzed as well.     

Update of indicators for climate change mitigation in Greece

This paper analyses the factors affecting greenhouse gas (GHG) emissions in Greece, (i.e. the drivers of pressures on climate change), using environmental indicators related to energy, demographics and economic growth. The analysis is based on the data of 2008 and considers types of fuel and sectors. The Kaya identity is used to identify the relationship between drivers and pressures, using annual time series data of National GHG emissions, population, energy consumption and gross domestic product. The analysis shows that over the period 2000–2008, GHG emissions show a slight variation, but they are almost stabilised, with a total increase of 1.6%. Despite the economic growth over that period, this stabilisation may be considered as a combination of reductions in the energy intensity of GDP and the carbon intensity of energy, which are affected by improvements in energy efficiency and introduction of “cleaner” fuels, such as natural gas and renewables in the energy mixture of the country.     

Features,trajectories and driving forces for energy-related GHG emissions from Chinese mega cites: The case of Beijing,Tianjin, Shanghai and Chongqing

With China’s rapid economic development and urbanization process, cities are facing great challenges for tackling anthropogenic climate change. In this paper we present features, trajectories and driving forces for energy-related greenhouse gas (GHG) emissions from four Chinese mega-cities (Beijing, Tianjin, Shanghai and Chongqing) during 1995–2009. First, top-down GHG inventories of these four cities, including direct emissions (scope 1) and emissions from imported electricity (scope 2) are presented. Then, the driving forces for the GHG emission changes are uncovered by adopting a time serial LMDI decomposition analysis. Results indicate that annual GHG emission in these four cities exceeds more than 500 million tons and such an amount is still rapidly growing. GHG emissions are mainly generated from energy use in industrial sector and coal-burning thermal power plants. The growth of GHG emissions in four mega-cities during 1995–2009 is mainly due to economic activity effect, partially offset by improvements in carbon intensity. Besides, the proportion of indirect GHG emission from imported energy use (scope 2) keeps growing, implying that big cities are further dependent on energy/material supplies from neighboring regions. Therefore, a comprehensive consideration on various perspectives is needed so that different stakeholders can better understand their responsibilities on reducing total GHG emissions.     

Kyoto Protocol implementation in Serbia as precognition of sustainable energetic and economic development

The paper gives reasons for low energy efficiency typical of the Serbian economy, which is based on outdated and dirty technologies. The comparison of selected economic indicators and indicators of energy efficiency in both Serbia and the European Union points out the benefits of the Kyoto Protocol implementation due to the growth of competitiveness in the global market. Serbia has no obligation to reduce GHG emissions, the authors point to the proposals whose implementation along with the mechanisms of the Protocol can enable Serbia the access to markets that trade GHG emissions and the access to dedicated funds, self-financing or attracting foreign investments to raise energy efficiency, which will be accompanied by adequate economic benefits. A similar principle can be applied in all countries that are not obliged to reduce GHG emissions. The application of different mechanisms aiming to increase energy efficiency in Serbia, could contribute to the increase of GDP annual growth rate from 5% to 7%, which cannot be achieved by any other economic instrument. Energy efficiency, which is actually a question of competitiveness of each economy, can finance itself through the mechanisms of the Kyoto Protocol by selling excess emissions resulting from improved energy efficiency.     

Climate consequences of low-carbon fuels: The United States Renewable Fuel Standard

A common strategy for reducing greenhouse gas (GHG) emissions from energy use is to increase the supply of low-carbon alternatives. However, increasing supply tends to lower energy prices, which encourages additional fuel consumption. This “fuel market rebound effect” can undermine climate change mitigation strategies, even to the point where efforts to reduce GHG emissions by increasing the supply of low-carbon fuels may actually result in increased GHG emissions. Here, we explore how policies that encourage the production of low-carbon fuels may result in increased GHG emissions because the resulting increase in energy use overwhelms the benefits of reduced carbon intensity. We describe how climate change mitigation strategies should follow a simple rule: a low-carbon fuel with a carbon intensity of X% that of a fossil fuel must displace at least X% of that fossil fuel to reduce overall GHG emissions. We apply this rule to the United States Renewable Fuel Standard (RFS2). We show that absent consideration of the fuel market rebound effect, RFS2 appears to reduce GHG emissions, but once the fuel market rebound effect is factored in, RFS2 actually increases GHG emissions when all fuel GHG intensity targets are met.     

To cool a sweltering earth: Does energy efficiency improvement offset the climate impacts of lifestyle?

As technical efficiency improvement in energy use remains a touchstone measure to curb greenhouse gas (GHG) emissions, there is substantial concern about whether this approach can offset the large and expanding impacts of human actions. Critics contend that without adjustments to the prevailing consumptive lifestyle, energy efficiency improvement will generate only token reductions in GHG emissions. I address this concern by examining the extent to which technical efficiency improvement in energy use offsets the impacts of housing-related lifestyle on GHG emissions. I build from two perspectives, the physical–technical–economic models that consider energy efficiency improvement as a potent strategy to curb residential energy consumption, and the lifestyle and social–behavioral approach, which questions this view. The analyses reveal consistent positive relationship between lifestyle and energy consumption. The results also indicate that energy efficiency improvement has mixed effects on energy consumption. In fact, model-based figures show that technical efficiency improvement in energy use leads to slightly higher energy consumption if it is not accompanied by adjustments to lifestyle.     

Comparison of the technical potential for hydrogen,battery electric,and conventional light-duty vehicles to reduce greenhouse gas emissions and petroleum consumption in the United States

Light-duty vehicles (LDV) are responsible for a large fraction of petroleum use and are a significant source of greenhouse gas (GHG) emissions in the United States. Improving conventional gasoline-powered vehicle efficiency can reduce petroleum demand, however efficiency alone cannot reach deep GHG reduction targets, such as 80% below the 1990 LDV GHG emissions level. Because the cost and availability of low-GHG fuels will impose limits on their use, significant reductions in GHG emissions will require combinations of fuel and vehicle technologies that both increase efficiency and reduce the emissions from fuel production and use. This paper examines bounding cases for the adoption of individual technologies and then explores combinations of advanced vehicle and fuel technologies. Limits on domestic biofuel production—even combined with significant conventional combustion engine vehicle improvements—mean that hydrogen fuel cell electric or battery electric vehicles fueled by low-GHG sources will be necessary. Complete electrification of the LDV fleet is not required to achieve significant GHG reduction, as replacing 40% of the LDV fleet with zero-emission hydrogen vehicles while achieving optimistic biofuel production and conventional vehicle improvements can allow attainment of a low GHG emission target. Our results show that the long time scale for vehicle turnover will ensure significant emissions from the LDV sector, even when lower emission vehicles and fuels are widely available within 15 years. Reducing petroleum consumption is comparatively less difficult, and significant savings can be achieved using efficient conventional gasoline-powered vehicles.     

Mitigating greenhouse gas emissions from China's cities: Case study of Suzhou

Knowledge of the factors driving greenhouse gas (GHG) emissions from cities is crucial to mitigating China's anthropogenic emissions. In this paper, the main drivers increasing GHG emissions from the Chinese city of Suzhou between 2005 and 2010 were identified and quantitatively analyzed using the Kaya identity and the log-mean Divisia index method. We found that economy and population were the major drivers of GHG emissions in Suzhou, having contributed 162.20% and 109.04%, respectively, to the increase in emissions. A decline in carbon intensity, which was caused by the declining energy intensity and an adjustment to the mixture of power and industrial structures, was the major determinant and accounted for a reduction of 171.24% in GHG emissions. Slowing and maintaining healthy growth rates of economy and population could be the primary and most effective means if Suzhou tries to curb the total emissions over the short term. It may be more realistic for Suzhou to control emissions by optimizing the economic structure for low-carbon industrial development because of the city's relative high energy requirements and low potential to mitigate GHGs by adjusting the energy mixture.     

Exploring the possibilities for setting up sustainable energy systems for the long term: two visions for the Dutch energy system in 2050

In this paper, two long-term visions of the Dutch future energy system are composed, analysed and evaluated. Both visions were set up to meet the requirement to reduce the GHG emissions with 80% in 2050 in comparison to 1990. The two visions start from very different perspectives and contexts. Quantitative analysis shows that when economic growth and energy use follow a business as usual development, emissions of GreenHouse Gases (GHG) can increase up to 250% of 1990 levels. The two, rather opposing, visions show that it is feasible to combine (strong) economic growth with far going reduction of GHG emissions, provided a number of key options are developed and applied. These options were chosen and discussed during several meetings by stakeholders in a dialogue process, using feedback from scientists, and consist of improvements in energy efficiency in industry, CO₂ neutral feedstocks for transportation, renewable energy and highly insulated buildings in the built environment and improvements in the primary production of the agricultural sector. It is clear that drastic changes in many areas in society are required to obtain the desired GHG-emission levels in 2050. The results also show though, that such a development can be realised in different ways. In other words, there are various ways to implement a low GHG emission economy in the long term.     

GHG emissions,GDP growth and the Kyoto Protocol: A revisit of Environmental Kuznets Curve hypothesis

The Kyoto Protocol attempts through political negotiations to guide participating industrialized countries’ greenhouse gas (GHG) emissions from a positive growing trend, to reach a peak point (or turning point), and then be reduced to a negative growth. That means the relationship between decreasing GHG emissions and economic growth may be described by an inverted-U curve (or called a bell-shaped curve), which is consistent with the concept of the Environmental Kuznets Curve (EKC) hypothesis.     

Analysis of policies to reduce oil consumption and greenhouse-gas emissions from the US transportation sector

Even as the US debates an economy-wide CO₂ cap-and-trade policy the transportation sector remains a significant oil security and climate change concern. Transportation alone consumes the majority of the US’s imported oil and produces a third of total US Greenhouse-Gas (GHG) emissions. This study examines different sector-specific policy scenarios for reducing GHG emissions and oil consumption in the US transportation sector under economy-wide CO₂ prices. The 2009 version of the Energy Information Administration’s (EIA) National Energy Modeling System (NEMS), a general equilibrium model of US energy markets, enables quantitative estimates of the impact of economy-wide CO₂ prices and various transportation-specific policy options. We analyze fuel taxes, continued increases in fuel economy standards, and purchase tax credits for new vehicle purchases, as well as the impacts of combining these policies. All policy scenarios modeled fail to meet the Obama administration’s goal of reducing GHG emissions 14% below 2005 levels by 2020. Purchase tax credits are expensive and ineffective at reducing emissions, while the largest reductions in GHG emissions result from increasing the cost of driving, thereby damping growth in vehicle miles traveled.     

Plug-in hybrid vehicle GHG impacts in California: Integrating consumer-informed recharge profiles with an electricity-dispatch model

This paper explores how Plug-in Hybrid Vehicles (PHEVs) may reduce source-to-wheel Greenhouse Gas (GHG) emissions from passenger vehicles. The two primary advances are the incorporation of (1) explicit measures of consumer interest in and potential use of different types of PHEVs and (2) a model of the California electricity grid capable of differentiating hourly and seasonal GHG emissions by generation source. We construct PHEV emissions scenarios to address inherent relationships between vehicle design, driving and recharging behaviors, seasonal and time-of-day variation in GHG-intensity of electricity, and total GHG emissions. A sample of 877 California new vehicle buyers provide data on driving, time of day recharge access, and PHEV design interests. The elicited data differ substantially from the assumptions used in previous analyses. We construct electricity demand profiles scaled to one million PHEVs and input them into an hourly California electricity supply model to simulate GHG emissions. Compared to conventional vehicles, consumer-designed PHEVs cut marginal (incremental) GHG emissions by more than one-third in current California energy scenarios and by one-quarter in future energy scenarios—reductions similar to those simulated for all-electric PHEV designs. Across the emissions scenarios, long-term GHG reductions depends on reducing the carbon intensity of the grid.     

Sustainable energy system design with distributed renewable resources considering economic,environmental and uncertainty aspects

Electricity generation using renewable energy generation technologies is one of the most practical alternatives for network planners in order to achieve national and international Greenhouse Gas (GHG) emission reduction targets. Renewable Distributed Generation (DG) based Hybrid Energy System (HES) is a sustainable solution for serving electricity demand with reduced GHG emissions. A multi-objective optimisation technique for minimising cost, GHG emissions and generation uncertainty has been proposed in this paper to design HES for sustainable power generation and distribution system planning while considering economic and environmental issues and uncertainty in power availability of renewable resources. Life cycle assessment has been carried out to estimate the global warming potential of the embodied GHG emissions from the electricity generation technologies. The uncertainty in the availability of renewable resources is modelled using the method of moments. A design procedure for building sustainable HES has been presented and the sensitivity analysis is conducted for determining the optimal solution set.     

MW cogenerated proton exchange membrane fuel cell combined heat and power system design for eco-neighborhoods in North China

Buildings account for most of the greenhouse gas (GHG) emissions causing global warming. The development of eco-neighborhood can improve the energy efficiency of buildings and reduce GHG emissions. A combined heat and power (CHP) system based on proton exchange membrane fuel cells (PEMFCs) is designed to supply electricity and thermal for eco-neighborhood in North China with low GHG emissions. Effects of different inlet parameters, such as PEMFC inlet pressure and current density, on multi-stack CHP system performance are discussed. Coupled with a dynamic load scenario, the adaptability of the designed PEMFC-CHP system is studied through PI control with an electricity-led strategy and a thermal-led strategy. Both strategies can effectively reduce GHG emissions and the eco-neighborhood with PEMFC-CHP system is more environmental friendly compared to conventional energy supply. The electricity-led strategy can satisfy the energy consumption of the eco-neighborhood but with thermal waste. The energy consumption for most of the time during a year can be satisfied by the PEMFC-CHP system under the thermal-led strategy, but the electricity gap exists as the thermal demand is lower. Under the electricity-led strategy, the GHG emission reduction of the eco-neighborhood under electricity-led strategy and thermal-led strategy are around 7000 ton and 5000 ton per year, respectively.     

Future fuel cell and internal combustion engine automobile technologies: A 25-year life cycle and fleet impact assessment

Hydrogen fuel cell (FC) vehicles are receiving increasing attention as a potential powerful technology to reduce the transportation sector's dependence on petroleum and substantially decrease emissions of greenhouse gases (GHGs) at the same time. This paper projects energy use and GHG emissions from different FC vehicle configurations and compares these values to the projected characteristics of similarly sized and performing gasoline and diesel fueled automobiles on a life cycle, well to wheels and cradle to grave basis. Our analysis suggests that for the next 20 or more years, new internal combustion engine (ICE) hybrid drive train vehicles can achieve similar levels of reduction in energy use and GHG emissions compared to hydrogen FC vehicles, if the hydrogen is derived from natural gas. The fleet impact of more fuel-efficient vehicles depends on the time it takes for new technology to (i) become competitive, (ii) increase its share of the new vehicles produced, and finally (iii) penetrate significantly into the vehicle fleet. Since the lead times for bringing improved ICE vehicle technology into production are the shortest, its impact on vehicle fleet energy use and emissions could be significant in 20–30 years, about half the time required for hydrogen FC vehicles to have a similar impact. Full emission reduction potential of FC vehicles can only be achieved when hydrogen is derived from zero or very low-carbon releasing production processes on a large scale—an option that further increases the impact leadtime. Thus, a comprehensive short- and long-term strategy for reducing automobile energy use and emissions should include both the continuous improvement of ICE vehicles and simultaneous research and development of hydrogen FC cars.     

Decoupling urban transport from GHG emissions in Indian cities—A critical review and perspectives

How to sustain rapid economic and urban growth with minimised detriment to environment is a key challenge for sustainable development and climate change mitigation in developing countries, which face constraints of technical and financial resources scarcity as well as dearth of infrastructure governance capacity. This paper attempts to address this question by investigating the driving forces of transport demand and relevant policy measures that facilitate mitigating GHG emissions in the urban transport sector in Indian cities based on a critical review of the literature. Our overview of existing literature and international experiences suggests that it is critical to improve urban governance in transport infrastructure quality and develop efficient public transport, coupled with integrated land use/transport planning as well as economic instruments. This will allow Indian cities to embark on a sustainable growth pathway by decoupling transport services demand of GHG emissions in the longer term. Appropriate policy instruments need to be selected to reconcile the imperatives of economic and urban growth, aspiration to higher quality of life, improvements in social welfare, urban transport-related energy consumption and GHG emissions mitigation target in Indian cities.     

Performance of residential fuel-cell-combined heat and power systems for various household types in Japan

A residential fuel-cell-combined heat and power (FC-CHP) system is considered a promising low-carbon technology that can reduce residential energy consumption and thus, achieve Japan's greenhouse gas (GHG) emissions reduction targets. However, to consider future directions for the systems' research and development, it is critical to understand the relationships between the performances of FC-CHP systems and residential energy demand profiles, which vary by household characteristic. This study evaluates the effects of applying city gas-fueled FC-CHP systems to Japanese households with different attributes. We compare total costs and GHG emissions for residential energy use between the FC-CHP systems and a conventional system. The economic performance results suggest that the basic PEMFC-CHP systems have an economic advantage only for four-person families with teenage children and further development efforts for low-output FC-CHP systems are required to enable various households save energy costs. The environmental evaluation results show that SOFC-CHP systems can drastically reduce GHG emissions from particularly small-sized households.     

Reducing atmospheric pollutant and greenhouse gas emissions of heavy duty trucks by substituting diesel with hydrogen in Beijing-Tianjin-Hebei-Shandong region,China

The extensive use of diesel heavy duty trucks (diesel HDTs) has led to substantial atmospheric pollutant and greenhouse gas (GHG) emissions in Beijing-Tianjin-Hebei-Shandong (BTHS) region, China. The substitution of hydrogen fuel cell heavy duty trucks (HFC-HDTs) for their diesel counterparts is effective to solve the problems above. Aiming at the BTHS region, a GPERF (GHG emission, Pollutant emission and Economic cost Reduction in Fuel cycle) assessment model was established combining with regional vehicle data to investigate the reductions of GHG emissions, pollutant emissions and economic expenditures by the substitution scheme. Data indicated that population of diesel HDTs and HFC-vehicles in BTHS region both accounted for reaching 25% of total in country. Results showed that the fuel substitution scheme could significantly reduce the GHG and pollutant emissions by vehicles in BTHS region, among which the GHG reduced by 1/3, while the NOx and PM remarkably reduced by around 50%.