甲醇-柴油混合燃料燃烧的数值模拟

本文根据柴油机燃烧过程的数学模型,将Chemkin中甲醇燃烧动力学反应机理导入Fluent软件中,对各种比例下的甲醇柴油微乳液进行了燃烧模拟计算,并用S195柴油机在台架上对计算值进行测试验证。结果表明:数值模拟的方法可靠。在不改动柴油机结构的情况下,甲醇含量影响燃烧效果,低甲醇含量可以提高燃烧效率,高甲醇含量降低燃烧效率,甲醇含量为10%时最佳。     

Direct and indirect uncertainties in the prediction of tilted irradiance for solar engineering applications

Global radiation measured on fixed-tilt, south-facing planes (40° and vertical) and a 2-axis tracker at NREL’s Solar Radiation Research Lab. in Golden, CO is compared to predictions from ten transposition models, in combination with either optimal or suboptimal input data of horizontal irradiance. Suboptimal inputs are typically used in everyday engineering calculations, for which the necessary data are usually unavailable for the site under scrutiny, and must be estimated in some way. The performance of the transposition models is first evaluated for ideal conditions when optimal data are used. In this specific case, it is found that the Gueymard and Perez models provide the best estimates of global tilted irradiance under clear skies in particular.The performance of four direct/diffuse separation models is also evaluated. Their predictions of direct and diffuse radiation appear biased in most cases, with a model-dependent magnitude. Finally, the performance of the resulting combinations of separation and transposition models is analyzed in a variety of situations. When only global irradiance is known, the accuracy of the tilted irradiance predictions degrades significantly, and is mainly conditioned by the local performance of the direct/diffuse separation method. For the south-facing vertical surface, inaccuracies in the ground reflection calculations becomes another key factor and significantly increase the prediction error. The Reindl transposition algorithm appears to perform best in this case. When using suboptimal input data for the prediction of plane-of-array irradiance on a moderately tilted plane (40°S) or a 2-axis tracking plane, the Hay, Reindl and Skartveit models are less penalized than others and tend to perform better. It is concluded that further research should be conducted to improve the overall process of predicting irradiance on tilted planes in realistic situations where no local high-quality irradiance or albedo measurements are available.     

Multilayer Perceptron approach for estimating 5-min and hourly horizontal global irradiation from exogenous meteorological data in locations without solar measurements

Only one thousand stations around the world measures solar radiation sometimes with a poor quality. The objective of this paper is to show if solar irradiations at short time scale, hourly and 5-min, (very under-studied time-step) can be estimated from more available and cheaper data using Artificial Neural Networks. 7 meteorological and 3 calculated parameters are used as inputs; 1023 inputs combinations are possible for each time-step; the best inputs combinations are pursued. A variable selection method based on Pearson's coefficient is firstly used between inputs and between output and inputs; some inputs are redundant (particularly calculated ones) and/or with a weak link with solar radiation (as wind speed and direction), sunshine duration is strongly correlated with solar irradiation. The models have a good adequacy mainly with sunshine duration in the input set. For hourly data, the performances of the 6 and 10 inputs model are nRMSE = 13.90% (nMAE = 13.28%, R² = 0.979) and nRMSE = 13.33% (nMAE = 12.72%, R² = 0.9812); without sunshine duration, the model nRMSE (with 5 inputs) falls to 28.27%. For 5-min data, the 6 and 10 inputs models have a nRMSE equal to 19.35% and 18.65% which is very good for such a time-step. A comparison with literature highlighted the quality of these models.     

国内外能源管理师制度的发展及建议

本文分析了国外实施能源管理师制度的几种模式:政府强制实施型、能源管理师注册型、协会推进型,重点介绍了日本、美国、欧盟在推进能源管理师制度方面的一些经验。文章还介绍了国内的石油和化工行业、青岛市等地区推进能源管理师制度的情况,并对我国推进能源管理师制度提出了一些建议。     

Consumer acceptance under hydrogen energy promotion policy: Evidence from Yangtze River Delta

Hydrogen fuel cell vehicle (HFCV) as an emerging industry with great potential have received great attention in the Yangtze River Delta, China. Under government's promotion of hydrogen energy, whether HFCV can be accepted by consumers is an important topic for future policymaking. Therefore, this study takes consumers' willingness to consume HFCV as the dependent variable and collects questionnaires from 21 cities in the Yangtze River Delta from 2020 to 2021. Based on Ordinary Least Squares (OLS) and Logit Regression, the evaluation was conducted from four perspectives: personal and family situation, environmental awareness, energy attitude and local product confidence. The results show that gender, age and income differences are not necessarily determinants of HFCV purchase, but educational level is a significant factor. Consistent with social-psychological studies, personal awareness of environmental protection and energy attitudes are the key factors that are significant affect HFCV purchase. Lastly, it is found that in the Yangtze River Delta, consumers' confidence in Chinese local hydrogen products is also a significant factor. This paper confirms that HFCV consumers have commonalities with other new energy consumers. However, due to the expectation of greater local production and development, enhancing the social recognition and confidence of local hydrogen technology may be one of the promotion approaches neglected.     

A techno-economic analysis of small-scale, biomass-fuelled combined heat and power for community housing

This paper presents the results of a techno-economic study into the feasibility of a number of biomass-fuelled CHP (BCHP) systems when operated in a community housing/mixed use context. Six systems comprising differing technologies have been analysed, with the assumption that the systems operate within an ESCO (energy services company) supply scenario. Actual demand data was obtained for a representative community housing scheme, along with technical performance and cost data on the various biomass CHP systems. Subsequently, an economic modelling tool was developed and a number of operational scenarios were analysed to determine the viability of specific systems and the sensitivity of the results to a range of technical and economic parameters. The impact of thermal storage was also considered in order to optimise heat usage as far as possible. The results indicate that within specific realistic ESCO operating scenarios, biomass CHP can demonstrate positive net present values without the need for capital subsidies. Optimal system design and implementation is critical for profitable operation and it is found that the best economic performance occurs for high load factors when the maximum quantity of both electricity and heat sold on-site is maximised. The results are also found to be very sensitive to a number of the model inputs.     

Energy supply for sustainable rural livelihoods. A multi-criteria decision-support system

Energy supply to the rural poor in developing countries is a complex activity that transcends the simple selection of a best technology. This paper explains the outcomes achieved by using a new multi-criteria decision-support system to assist in calculating the most appropriate set of energy options for providing sufficient power to fulfil local demands that improve livelihoods. The elicitation of the priorities of future users, which are subsequently integrated into the energy selection process, is seen as a mechanism for the promotion of energy policies that ensure that technological developments reduce poverty. The sustainable rural energy decision support system (SURE DSS), a methodological package and software designed by the research team RESURL builds upon technical and non-technical features of energy development in remote poor areas, drawing on a sustainable livelihoods approach as part of its rationale. SURE enables simulations and calculation of the disparities that may arise between current and potential livelihoods after specific energy solutions have been installed, as well as measuring potential trade-offs among alternative livelihoods. The paper reports the outcome of an application of SURE to the case of a remote Colombian rural community whose total energy demands are only partly met through a diesel generator.     

Numerical study of heat transfer of hydrogen combustion in noble gases atmosphere in compression ignition engine

The high energy content of hydrogen and zero carbon emission from hydrogen combustion is very important for compression ignition engine development. Hydrogen requires a very high auto-ignition temperature, which encourages replacing nitrogen with noble gases with higher specific heat ratio during compression process. In noble gases-hydrogen combustion, higher combustion temperature potentially leading to a higher heat loss. This paper aims to investigate the effect of hydrogen combustion in various noble gases on heat distribution and heat transfer on the cylinder wall. Converge CFD software was used to simulate a Yanmar NF19SK direct injection compression ignition engine. The local heat flux was measured at different locations of cylinder wall and piston head. The heat transfer of hydrogen combustion in various noble gases at different intake temperatures was studied using the numerical approach. As a result, hydrogen combustion in light noble gases such as helium produces faster combustion progress and higher heat temperature. The hydrogen combustion that experienced detonation, which happened in neon at 340 K and argon at 380 K, recorded a very high local heat flux at the cylinder head and piston due to the rapid combustion, which should be avoided in the engine operation. At a higher intake temperature, the rate of heat transfer on the cylinder wall is increased. In conclusion, helium was found as the best working gas for controlling combustion and heat transfer. Overall, the heat transfer data gained in this paper can be used to construct the future engine hydrogen in noble gases.     

Energy use pattern and sensitivity analysis of energy inputs and input costs for pear production in Iran

The purposes of this study were to determine energy use pattern and investigate the relationships between energy inputs and yield, cost inputs and income for pear production in the Tehran province of Iran. In this study, data were collected by administering a questionnaire in face-to-face interviews in the production year of 2009/2010. This article presents a comprehensive picture of the current status of energy consumption and some energy indices like energy ratio, energy productivity, specific energy, net energy and energy intensiveness. Results showed that the total energy input of 172,608.43 MJ ha⁻¹ was required for pear production. Among input energy sources, electricity energy with share of 78% of total input energy had the highest share. The energy use efficiency and energy productivity were found as 0.51 and 0.27 kg MJ⁻¹, respectively. To investigate the relationships between energy inputs and yield, cost inputs and income, Cobb–Douglas production function was selected as the best function. Sensitivity analysis of energy and cost inputs was carried out using the marginal physical productivity (MPP) technique. Economic analysis of pear production was carried out and total cost of pear production was obtained as 11,936.97 $ h⁻¹. Also the benefit to cost ratio was calculated as 3.11.     

Preliminary identification of potential markets for off-grid electrification: tool development and a case study of Ghana

With more than one billion people lacking access to electricity in the world, ensuring universal access to electricity by 2030 remains a major challenge which cannot be left to the government initiatives alone. Access to local information and identification of potential areas for investment can be a challenge for investors. This paper provides a tool for preliminary assessment of potential markets for off-grid electrification in developing countries and applies this to Ghana to demonstrate its applicability. A multi-criteria approach is used to rank the districts according to the overall potential and the best markets and least favourable areas for investment are identified. The tool offers flexibility to include new inputs to the analysis and the factor weights can be adjusted as appropriate. The case study shows that the tool can effectively identify potential areas from a list of candidates and offers support to analysts.     

基于博弈论的电采暖系统应用经济性研究

使用清洁电力代替化石能源燃烧供暖是实现"碳中和"的一个重要方式.若无适宜的商业模式,在一些煤炭资源丰富的地区,将很难推广电采暖替代燃煤供暖系统.首先,本文提出一种清洁电能采暖的商业模式,分析了利益相关者政府、国家电网和热能用户三者之间关于电采暖推广的博弈关系.基于此,提出利益相关者的收益函数并以次作为各自的优化目标,以...     

Optimization of an artificial neural network dedicated to the multivariate forecasting of daily global radiation

This paper presents an application of Artificial Neural Networks (ANNs) to predict daily solar radiation. We look at the Multi-Layer Perceptron (MLP) network which is the most used of ANNs architectures. In previous studies, we have developed an ad-hoc time series preprocessing and optimized a MLP with endogenous inputs in order to forecast the solar radiation on a horizontal surface. We propose in this paper to study the contribution of exogenous meteorological data (multivariate method) as time series to our optimized MLP and compare with different forecasting methods: a naïve forecaster (persistence), ARIMA reference predictor, an ANN with preprocessing using only endogenous inputs (univariate method) and an ANN with preprocessing using endogenous and exogenous inputs. The use of exogenous data generates an nRMSE decrease between 0.5% and 1% for two stations during 2006 and 2007 (Corsica Island, France). The prediction results are also relevant for the concrete case of a tilted PV wall (1.175 kWp). The addition of endogenous and exogenous data allows a 1% decrease of the nRMSE over a 6 months-cloudy period for the power production. While the use of exogenous data shows an interest in winter, endogenous data as inputs on a preprocessed ANN seem sufficient in summer.     

Land use and second-generation biofuel feedstocks: The unconsidered impacts of Jatropha biodiesel in Rajasthan,India

Governments around the world see biofuels as a common solution to the multiple policy challenges posed by energy insecurity, climate change and falling farmer incomes. The Indian government has enthusiastically adopted a second-generation feedstock – the oilseed-bearing shrub, Jatropha curcas – for an ambitious national biodiesel program. Studies estimating the production capacity and potential land use implications of this program have typically assumed that the ‘waste land’ slated for Jatropha production has no economic value and that no activities of note will be displaced by plantation development. Here we examine the specific local impacts of rapid Jatropha plantation development on rural livelihoods and land use in Rajasthan, India. We find that in Jhadol Tehsil, Jatropha is planted on both government and private land, and has typically displaced grazing and forage collection. For those at the socioeconomic margins, these unconsidered impacts counteract the very benefits that the biofuel programs aim to create. The Rajasthan case demonstrates that local land-use impacts need to be integrated into decision-making for national targets and global biofuel promotion efforts.     

低产油井油、气、水自动计量系统

为提高低产油井计量的准确性,实现油、气、水三相计量,并确定油井的单次最佳计量时间和计量周期,本设计采用PLC自控系统与智能传感器相结合的方式,对两相分离器进行改造,代替传统的玻璃管计量方法。通过在油、气管线上安装电动阀门,对油、气、水进行在线自动连续计量。利用以太网通讯获得计量过程中传感器、仪表的读数,显示在计算机界面上,为用户提供了监控、查询功能,减轻了计量工人的劳动强度,提高了计量时效和计量精度,现场应用效果良好。该技术实施简便,成本较低,对稠油区块的低产液量含水原油产量计量尤为准确,但由于含水率测试在排液状态下进行,因此数值波动较大。另外通过建立数据分析模型,应用大数定理和中心极限定理,对低产油井的最佳计量时间和量油周期进行了分析确定,因此具有一定的推广价值。     

Manufacturing productivity and energy efficiency: a stochastic efficiency frontier analysis

This paper presents a mathematical model to estimate both production frontier and energy demand frontier, and evaluate the energy efficiency in the automotive manufacturing sector using plant‐level production and utility consumption data. By using the stochastic frontier analysis, two models—an output efficiency model (production frontier) and an input efficiency model (energy demand frontier)—are developed to analyze the plant's energy efficiency performance relative to the ‘best practice’ among peers. Both the structure and parameters of two stochastic frontier functions are identified to understand the relationship between production inputs (e.g., utilities and plant‐specific variables) and the overall productivity. A case study of a set of automotive engine manufacturing plants is conducted and shows that electricity has higher efficiency than other forms of utility in those production‐related activities, and the regional and climate factors have significant impacts on energy efficiency. The models provide a way to measure how far from the production frontier as well as how far from the energy demand frontier the plant is. The results also provide useful information about the inefficient energy components in manufacturing facilities. The opportunities of improving plant‐level efficiency in automotive manufacturing plants can be revealed by the results. Copyright © 2015 John Wiley & Sons, Ltd.     

Renewables portfolio,individual preferences and social values towards RES technologies

The massive deployment of renewable energy sources represents a high priority for Greece in order to comply with the Directive 2009/28/EC on the promotion of the use of energy from renewable sources by 2020. In this perspective, Aegean islands especially Lesvos, are endowed with a considerable potential of a portfolio of renewables, a fact that the entrepreneurial interest has already been targeted. However, regulatory attempts for a massive penetration of renewables do not take seriously into account preferences and risk perceptions of local communities where the proposed projects are to be installed. The aim of this study is to investigate individual preferences and social values towards specific technologies of renewables in Lesvos island. We apply an open-ended contingent valuation survey in order to analyze factors shaping public attitudes towards a portfolio of renewable technologies and estimate the economic welfare (Willingness To Pay) of the preferred technologies. We argue that such information is relevant for energy policy design and the establishment of effective measures for the promotion of renewable energy sources.     

Analysing the interactions between renewable energy promotion and energy efficiency support schemes: The impact of different instruments and design elements

CO₂ emissions reduction, renewable energy deployment and energy efficiency are three main energy/environmental goals, particularly in Europe. Their relevance has led to the implementation of support schemes in these realms. Their coexistence may lead to overlaps, synergies and conflicts between them. The aim of this paper is to analyse the interactions between energy efficiency measures and renewable energy promotion, whereas previous analyses have focused on the interactions between emissions trading schemes (ETS) and energy efficiency measures and ETS and renewable energy promotion schemes. Furthermore, the analysis in this paper transcends the “certificate” debate (i.e., tradable green and white certificates) and considers other instruments, particularly feed-in tariffs for renewable electricity. The goal is to identify positive and negative interactions between energy efficiency and renewable electricity promotion and to assess whether the choice of specific instruments and design elements within those instruments affects the results of the interactions.     

The role of political connection on overinvestment of Chinese energy firms

This paper explores the role of political connection on the overinvestment of Chinese energy firms. We argue that political connection can act as a “helping hand” that enables energy firms to obtain more government support to invest and a “grabbing hand” that forces politically connected energy firms to heavily overinvest for the promotion benefit of local politicians. Our analysis shows that overinvestment of an energy firm is positively affected by its political connection. In terms of the “helping hand” effects, we find that politically connected energy firms are more likely overinvest when they receive more government subsidy. In terms of the “grabbing hand” effects, we show that local politician is more likely to force energy firms to overinvest if the politician is approaching the 65-year-old promotion line. Although firms are less likely to overinvest during the economic downturn, local politician shapes the investment decision of energy firms through the “grabbing hand” effects.     

Benchmarking energy use in the paper industry: a benchmarking study on process unit level

There are large differences between paper mills in, e.g. feedstock use and grades produced, but typical processes are similar in all mills. The aim of this study is to benchmark the specific energy consumption (SEC) of similar processes within different paper mills in order to identify energy improvement potentials at process level. We have defined improvement potentials as measures that can be taken at mill/process level under assumed fixed inputs and outputs. We were able to use industrial data on detailed process level, and we conducted energy benchmarking comparisons in 23 Dutch paper mills. We calculated average SECs per process step for different paper grades, and we were able to identify ranges in SECs between mills producing the same grade. We found significant opportunities for energy efficiency improvement in the wire and press section as well as in the drying section. The total energy improvement potential based on identified best practices in these sections was estimated at 5.4 PJ (or 15 % of the total primary energy use in the selected mills). Energy use in the other processes was found to be too dependent on quality and product specifications to be able to quantify improvement potentials. Our results emphasise that even a benchmark on detailed process level does not lead to clear estimations of energy improvement potentials without accounting for structural effects and without having a decent understanding of the process.     

Promoting renewables in the energy sector of Tajikistan

Energy technology transfer can allow countries to move quickly to environmentally sound and sustainable practices. Integration of Renewable Energy Sources (RES) technologies in the energy sector of these countries can play a key role towards sustainability. The level of penetration of RES technologies remains seriously in arrears in Tajikistan, although the country has great RES potential. The aim of the paper is to look deeply into the most appropriate RES technology, which can be gradually introduced in the energy sector of Tajikistan and supported through demonstrations, business workshops, guides for installers with technical details and design proposals. The multi-dimensional methodology adopted included transparent decision support processes, using linguistic variables, taking into consideration the specific conditions prevailing in Tajikistan, as well as policy and technical proposal for the further development of the local market. Based on the results, the emphasis is laid on decentralized heat production, though the promotion of Solar Water Heaters, which seems to be an attractive energy option, with multiple benefits for the country.