Energy balance of solar absorption and vapour compression cooling systems

Solar absorption cooling systems are viewed as potential alternatives to fossil-fuel-based conventional cooling systems. This view is investigated in this paper from the point of view of the energy balance of solar absorption and conventional systems. The paper investigates the primary energy needs of three cooling systems; dry and wet cooled vapour compression systems and wet cooled solar absorption. The sources of energy demand in the three systems are identified and their primary energy needs determined. The paper, then, investigates the conditions under which the energy inputs to the solar system breaks even with the other two systems. The investigation is conducted with particular reference to the operational and environmental conditions in Kuwait.     

Energy consumption and GHG emissions of GTL fuel by LCA: Results from eight demonstration transit buses in Beijing

Gas-to-liquids (GTL) as an alternative to diesel is considered to be one of the technical options to reduce petroleum consumption in the on-road transportation sector. Between May and August 2007, a joint demonstration program by Tsinghua University, Beijing Transit, Cummins Corporation and Shell Corporation was carried out in Beijing. The program focused on the supply systems and vehicle use of GTL fuel. The demonstration fleet was formed by four transit buses fueled with GTL and four with diesel. It was demonstrated that GTL has good compatibility with diesel in terms of fuel supply system and vehicle use. This paper compares the energy consumption and GHG emissions of diesel and GTL fuel supply chains by life cycle analysis based on demonstration results. The results indicate GTL’s large range (reported 54–70%) in synthesis efficiency, as the key factor in determining energy consumption and GHG emissions within the GTL fuel supply chain. For the probable case (GTL synthesis efficiency: 65%), the life cycle energy consumption and GHG emissions of GTL fuel are 42.5% and 12.6% higher than that of diesel. For two sensitivity analysis cases (GTL synthesis efficiency: 54% and70%), energy consumptions are 74.2% and 31.2% higher and GHG emissions are 27.3% and 7.4% higher than that of the diesel fuel supply chain. If the efficiency of the GTL synthesis process is improved to 75%, then the GHG emissions level of the GTL fuel supply chain can be reduced to the same level as the diesel fuel supply chain.     

Energy consumption analysis of integrated flowsheets for production of fuel ethanol from lignocellulosic biomass

Fuel ethanol is considered one of the most important renewable fuels due to the economic and environmental benefits of its use. Lignocellulosic biomass is the most promising feedstock for producing bioethanol due to its global availability and to the energy gain that can be obtained when non-fermentable materials from biomass are used for cogeneration of heat and power. In this work, several process configurations for fuel ethanol production from lignocellulosic biomass were studied through process simulation using Aspen Plus. Some flowsheets considering the possibilities of reaction–reaction integration were taken into account among the studied process routes. The flowsheet variants were analyzed from the energy point of view utilizing as comparison criterion the energy consumption needed to produce 1 L of anhydrous ethanol. Simultaneous saccharification and cofermentation process with water recycling showed the best results accounting an energy consumption of 41.96 MJ/L EtOH. If pervaporation is used as dehydration method instead of azeotropic distillation, further energy savings can be obtained. In addition, energy balance was estimated using the results from the simulation and literature data. A net energy value of 17.65–18.93 MJ/L EtOH was calculated indicating the energy efficiency of the lignocellulosic ethanol.     

Energy potential from municipal solid waste in Malaysia

The average amount of municipal solid waste (MSW) generated in Malaysia is 0.5–0.8 kg/person/day and has increased to 1.7 kg/person/day in major cities. This paper highlights the MSW characteristics for the city of Kuala Lumpur. Currently, the waste management approach being employed is landfill, but due to rapid development and lack of space for new landfills, big cities in Malaysia are switching to incineration. A simple evaluation was conducted to establish the amount of energy that would be recovered based on the characteristics of the MSW if it were to be incinerated. From the characterization exercise, the main components of the Malaysian MSW were found to be food, paper and plastic, which made up almost 80% of the waste by weight. The average moisture content of the MSW was about 55%, making incineration a challenging task. The calorific value of the Malaysian MSW ranged between 1500 and 2600 kcal/kg. However, the energy potential from an incineration plant operating based on 1500 ton of MSW/day with an average calorific value of 2200 kcal/kg is assessed to be at 640 kW/day.     

Forecasting world and regional aviation jet fuel demands to the mid-term (2025)

This article provides jet fuel demand projections at the worldwide level and for eight geographical zones until 2025. Air traffic forecasts are performed using dynamic panel-data econometrics. Then, the conversion of air traffic projections into quantities of jet fuel is accomplished by using a complementary approach to the ‘Traffic Efficiency’ method developed previously by the UK Department of Trade and Industry to support the Intergovernmental Panel on Climate Change ( IPCC, 1999). According to our main scenario, air traffic should increase by about 100% between 2008 and 2025 at the world level, corresponding to a yearly average growth rate of 4.7%. World jet fuel demand is expected to increase by about 38% during the same period, corresponding to a yearly average growth rate of 1.9% per year. According to these results, energy efficiency improvements allow reducing the effect of air traffic rise on the increase in jet fuel demand, but do not annihilate it. Jet fuel demand is thus unlikely to diminish unless there is a radical technological shift, or air travel demand is restricted.     

Energy consumption reduction of a PEM fuel cell motor-compressor group thanks to efficient control laws

This paper deals with the energy optimization of an embedded fuel cell generator. To reach this aim, experimentally validated models of a low power 5 kW proton exchange membrane fuel cell (PEMFC) and its most power hungry ancillary (motor-compressor group) are described. All simulation results have been performed using Matlab/Simulink^® environment. Moreover, a control strategy of the air supply circuit integrated in an embedded fuel cell system is proposed. The air flow control of the air supply circuit is built around a fuzzy PD + I controller and for the air supply set point determination, a fuzzy supervision is proposed. The parameters of this fuzzy supervision have been optimized thanks to particle swarm optimization (PSO) method.     

Energy and associated greenhouse gas emissions from household appliances in Malaysia

Today, electricity is an indispensable key for civilization and development. The trend of electricity consumption is rather escalating. Electricity generation principally depends upon fossil fuels. In one hand, the stocks of these fuels have been confirmed to be critically limited. On the other hand, in process of electricity generation by means of these fuels, a number of poisonous by-products adversely affect the conservation of natural eco-system. Further, electricity driven appliances use emanate anti-environmental gases that also affect human health and climate. Therefore, estimation of energy consumption for operating household appliances, savings of energy under policy intervention, and emission of poisonous gases in a fast developing country deserve academic attention.     

医院空调冷热源系统能耗及经济性分析

医院建筑是进行疾病诊断及治疗活动的场所,人员集中性较大且包含一些特殊功能区域。因此,医院建筑对空调系统的要求比一般办公性建筑高,其必须对整个医院提供稳定可靠的能源供应,保证医院正常医疗活动。目前,我国医院建筑的空调能耗能占整个建筑能耗的50%以上,空调节能势在必行。面对新一轮大规模医院建设,需要在设计之初就考虑空调系统节能策略,尤其在空调冷热源的选择时不仅要满足实际需求,同时还需要符合国家节能减排低碳的生态文明原则。以江苏地区某一新建医院为例,针对2种冷热源选型方案,从投资、运行能耗及费用进行了经济性比较分析,得到了适合该医院的最佳方案,对以后此类项目的设计施工提供一定借鉴意义。     

提高DF4B型机车冷却水和机油温度降低燃油消耗

阐述在DF_(4B)型机车上使用6B型温包替代3B型温包,提高机车冷却水和机油温度,实现降低机车燃油消耗的目的。     

Energy efficiency and carbon trading potential in Malaysia

The damage inflicted by global warming is happening far faster than any experts have predicted or anticipated. Since the Kyoto Protocol was signed in 1997 to fight global warming through reducing global greenhouse gases (GHGs) emission, the world climate pattern has worsened at an accelerated rate beyond expectation. While developed countries sanctioned by the protocol are committed to achieve their GHG emission targets, developing nations play similar roles on a voluntary basis. Since almost all of the GHGs emissions come from energy sector, it is obvious that energy policy and related regulatory frameworks play imperative roles in realizing the Kyoto Protocol objectives. With carbon dioxide (CO₂) touted as the main remedy in the GHGs emissions, it is only reasonable that carbon trading becomes the essential element in the Protocol. Recently a milestone is marked in the Kyoto Protocol with the 2009 Climate Summit in Copenhagen, Denmark, with all participating countries further committed themselves in fulfilling the protocol's obligations before the commitment period due in 2012. It is worthwhile to review the various energy efficiency efforts and carbon trading potential in Malaysia, a country which although does not bear any obligation, has ratified and lauded the cause of the protocol. Malaysia as a developing nation is seen as a direct beneficiary from carbon trading and in this paper, how the country energy policies have evolved over the years with concerted efforts from the government to minimize its carbon footprint through numerous energy efficiency implementations are discussed in length. The impact from the 2009 Climate Summit on Malaysia is also briefed.     

Energy consumption by gender in some European countries

Household total energy use has been estimated in numerous studies in recent decades and differences have mainly been explained by levels of income/expenditure. Studies of gender consumption patterns show that men eat more meat than women and drive longer distances, potentially leading to higher total energy use by men. In this study we calculated the total energy use for male and female consumption patterns in four European countries (Germany, Norway, Greece and Sweden) by studying single households. Significant differences in total energy use were found in two countries, Greece and Sweden. The largest differences found between men and women were for travel and eating out, alcohol and tobacco, where men used much more energy than women. We suggest that these findings are policy relevant for the EU, which aims to mainstream gender issues into all activities and to lower its total energy use.     

Energy for sustainable development in Malaysia: Energy policy and alternative energy

Energy is often known as the catalyst for development. Globally, the per capita consumption of energy is often used as a barometer to measure the level of economic development in a particular country. Realizing the importance of energy as a vital component in economic and social development, the government of Malaysia has been continuously reviewing its energy policy to ensure long-term reliability and security of energy supply. Concentrated efforts are being undertaken to ensure the sustainability of energy resources, both depletable and renewable. The aim of this paper is to describe the various energy policies adopted in Malaysia to ensure long-term reliability and security of energy supply. The role of both, non-renewable and renewable sources of energy in the current Five-Fuel Diversification Strategy energy mix will also be discussed. Apart from that, this paper will also describe the various alternative energy and the implementation of energy efficiency program in Malaysia.     

Energy and economic analysis of an integrated solar absorption cooling and heating system in different building types and climates

The use of solar energy in buildings is an important contribution for the reduction of fossil fuel consumption and harmful emissions to the environment. Solar thermal cooling systems are still in their infancy regarding practical applications, although the technology is sufficiently developed for a number of years. In many cases, their application has been conditioned by the lack of integration between cooling and heating systems. This study aims to evaluate the potential of integrated solar absorption cooling and heating systems for building applications. The TRNSYS software tool was used as a basis for assessment. Different building types were considered: residential, office and hotel. The TRNSYS models are able to run for a whole year (365 days), according to control rules (self-deciding whether to operate in heating or cooling modes), and with the possibility of combining cooling, heating and DHW applications. Three different locations and climates were considered: Berlin (Germany), Lisbon (Portugal), and Rome (Italy). Both energy and economic results are presented for all cases. The different local costs for energy (gas, electricity and water) were taken into account. Savings in CO₂ emissions were also assessed. An optimization of solar collector size and other system parameters was also analysed.     

Energy and emission analysis for industrial motors in Malaysia

The industrial sector is the largest user of energy in Malaysia. Industrial motors account for a major segment of total industrial energy use. Since motors are the principle energy users, different energy savings strategies have been applied to reduce their energy consumption and associated emissions released into the atmosphere. These strategies include using highly efficient motors, variable speed drive (VSD), and capacitor banks to improve the power factor. It has been estimated that there can be a total energy savings of 1765, 2703 and 3605 MWh by utilizing energy-efficient motors for 50%, 75% and 100% loads, respectively. It was also found that for different motor loads, an estimated US$115,936 US$173,019 and US$230,693 can be saved in anticipated energy costs. Similarly, it is hypothesized that a significant amount of energy can be saved using VSD and capacitor banks to reduce speed and improve the power factor, thus cutting energy costs. Moreover, a substantial reduction in the amount of emissions can be effected together with the associated energy savings for different energy savings strategies. In addition, the payback period for different energy savings strategies has been found to be reasonable in some cases.     

Energy consumption by multi-stage flash and reverse osmosis desalters

Kuwait and most of the Gulf countries, depend mainly on desalted water from the sea for satisfying their fresh water needs. These countries are using the multi-stage flash (MSF) desalting system, as the ‘work horse’ for their water production. This system is less efficient in energy consumption as compared to the reverse osmosis (RO) system. Moreover, large units based on the MSF system have to be combined with steam or gas turbines power plants for better utilization of steam supplied to the MSF units at moderately low temperature and pressure (as compared to steam produced by large steam generators). The value and the cost of the thermal energy supplied to the MSF desalting system depends on the method of supplying this energy. This steam can be supplied directly from a fuel operated boiler or heat recovery steam generator associated with a gas turbine. It can also be supplied from the exhaust of a steam back pressure turbine or bled from condensed extraction steam turbine at a pressure suitable for the desalting process. Any energy comparison should be based on simple criteria, either how much fuel energy is consumed to produce this energy or how much mechanical energy is needed per unit product. The energy consumed in the light of the practice used in most Gulf countries are discussed here. In this study, reference desalting and power plants are used for comparison purposes. This study shows that shifting from MSF desalting system to the RO system can save up to 66% of the fuel energy used to desalt seawater.     

Energy extraction from seaweed under low temperatures by using an alkaline fuel cell

Marine macroalgae are considered to be one of the most important biomass sources. They can grow rapidly under various conditions, leading to extensive algal blooms. In this work, a reusable solid-acid catalyst, silicotungstic acid, was used to treat the seaweed Enteromorpha prolifera. Under optimum conditions, 237.354 mg/g (23.735%) of total reducing sugar yield was obtained. The hydrolysate was used as the substrate for bioenergy production in an alkaline fuel cell, and the fuel cell achieved the maximum power density of 6.616 W/m² under the condition of 3 M KOH and 8.572 mg/mL reducing sugar in hydrolysate, which is higher than any other reported algae-fed fuel cells.     

The feasibility and implications for conventional liquid fossil fuel of the Indonesian biofuel target in 2025

This paper identifies conventional liquid fossil fuels that can be replaced or blended with biofuel and quantifies the biofuels required to meet the Indonesian biofuel target of at least 5% of the total primary energy mix in 2025. The analysis was conducted using the Long range Energy Alternatives Planning (LEAP) system with an energy elasticity of 1 and maximum allowable biofuel blending ratios according to the current best practices. The results show that the target could be achieved with the maximum blending alternative based on constant energy demand growth of 6%. The target requires a total contribution from biofuel of about 8–27 GL in 2025 depending on blending ratios. In energy terms, these are equivalent to 232–782 PJ or about 40–135 million barrels crude oil, which constitute roughly around 3.3–11.0% of the estimated liquid fossil fuel oil annual consumption in that year. The results imply that it may have detrimental environmental impact, as it requires 5.2 million ha of palm oil and sugar cane plantations. On the positive side, achieving the target offers potential new employment opportunities of about 3.4 million jobs, particularly in the agricultural sector relevant to liquid biofuel production.     

Analysis and forecast of the Tianjin industrial carbon dioxide emissions resulted from energy consumption

This paper analyses the carbon dioxide emissions caused by industrial energy consumption of Tianjin from 2005 to 2012. The carbon emissions decomposition illustrated that the scale of production factor played a major role in the growth of Tianjin industrial carbon emissions and the average contribution of carbon emissions is up to 220.8975% in the statistical period; the intensity of energy factor played an important role in slowing down the growth of industrial carbon dioxide emissions. The average contribution of carbon emissions was ?136.1994% in the statistical period. The prediction model based on carbon emissions data from industrial energy consumption from 2003 to 2012 reached a high accuracy, with an average error of 1.78% for stochastic impacts by regression on population, affluence, and technology (STIRPAT) model, 2.41% for the Logistic regression model and an average error of 1.54% for the grey model. This research can contribute to predict the carbon emission and through it some suggestions can be made.     

Energy and economic returns from cattle dung as manure and fuel

We have studied the fuel use of cattle dung. Data on substitution for fertilizers by farm yard manure formed the basis of this work. The use of dung as fuel is more efficient than its use as manure. Dung (after providing energy for manufacturing fertilizers equal to the nutrient content of the dung in India) used as fuel will provide power equal to 2000 ME_e, which is 1.3 times the power generation capacity of the Punjab.     

Energy storage: The route to liberation from the fossil fuel economy?

If a low-carbon energy strategy is to be developed up to 2050, renewable energy sources will need to be deployed on a large scale against a scenario of increasing global energy demand. Renewables will vary from large-scale regional wind and marine clusters to more localised ‘micro’ generation. If a low-carbon strategy is to be successful, automotive transport will also need to be linked to the renewable infrastructure. Both of these need the development of efficient and viable energy storage.