LCOE建模及关键影响因子分析

围绕着光伏发电系统的度电成本(LCOE)概念和现状,开发了一套适用于我国光伏发电项目的LCOE计算模型。利用该模型估算我国当前光伏发电项目的LCOE水平,对LCOE的关键影响因子进行分析,并预测光伏发电项目的LCOE发展趋势。     

大型风电项目平准化成本模型研究

平准化成本(LCOE)是国内外学者广泛应用于评估各种发电技术综合竞争力的经济性指标。文章根据LCOE的基本原理及平准化成本分析模型,提出了适用于我国大型风电项目的 LCOE分析模型,并进行了算例分析;结合算例,探讨了影响风电项目LCOE的敏感性因素,对不同情景下的LCOE进行了预测研究。该研究结果对于风电项目的经济性评估及风电产业的发展具有重要的意义。     

基于优化LCOE的光伏平价上网可行性分析

平准化度电成本(LCOE)是国际上通用评价发电技术的主要经济性指标。在原有LCOE评估模型基础上,增加了考虑折旧抵税后的税收成本和损耗带来的额外成本,进一步优化成本模型,并考虑清洁发展机制(CDM)的收入因素,提出更准确、更完整的优化LCOE模型,并结合其他投资指标提出适应我国现状的光伏发电效益模型。以南京某3 MW分布式光伏电站项目为例进行敏感性分析,进一步探讨未来光伏平价上网的可行性,提出提高光伏系统单位造价和提高发电量是实现平价上网的主要途径。     

从LCOE与电价关系角度实证研究光伏发电项目的平价上网路径

以中国不同地区的20个光伏发电项目为样本,计算项目的平准化度电成本(LCOE),将计算得到的不含税LCOE修正为含税LCOE,并与项目的核准电价、当地的脱硫煤标杆电价对标,分析含税LCOE与核准电价之间的变化趋势;对LCOE进行敏感性分析,将平价上网时代含税LCOE降幅与核准电价降幅趋势进行对比分析,并针对平价上网时代...     

基于实物期权的光伏电站项目LCOE分析

在分析关于光伏电站项目当前政策的基础上,建立了对标燃煤标杆上网电价的光伏发电平准化度电成本(LCOE)模型,并与实物期权方法相结合,考虑项目延迟期权与放弃期权的复合实物期权价值,构建了全面反映项目竞争力价值的扩展平准化度电成本(extended levelized cost of energy,ELCOE)模型,并以某光伏电站项目为例进行了分析。分析结果表明：平价上网机制下,建立的LCOE模型能够直接对标燃煤标杆上网电价,且ELCOE模型考虑了光伏电站项目未来收益的不确定性与管理灵活性,弥补了LCOE法忽略项目未来不确定性价值的不足,避免决策失误。     

基于LCOE的单面与双面双玻光伏组件经济性分析

首先引入平准化度电成本(LCOE)模型,分析了计算LCOE时合适的折现率取值;然后对典型场景下采用单面光伏组件和双面双玻光伏组件的光伏电站进行了发电量模拟;最后结合发电量模拟结果和LCOE模型,比较了典型场景下单面光伏组件和双面双玻光伏组件的经济性.此外,还对分析结果进一步拓展,得到了不同价差、不同发电量增益下的单面光...     

光伏支架成本及选型分析

以长沙地区为例，对采用不同类型光伏支架时光伏电站的占地面积、发电量、运行成本、平准化度电成本(LCOE)进行了分析，并分析了不同场景下适用的光伏支架类型。分析结果显示：1)从发电量差异系数来看，双轴跟踪式光伏支架的发电量差异系数最高，单轴跟踪式光伏支架的次之，固定式光伏支架的最低。2) LCOE从低到高依次为：水平单轴跟踪式光伏支架<固定式光伏支架<垂直单轴跟踪式光伏支架<斜单轴跟踪式光伏支架<双轴跟踪式光伏支架。3)当光伏电站项目以经济性最优为考量标准时，建议选择平单轴跟踪式光伏支架。4)当光伏电站项目以装机容量最大为考量标准时，建议选择固定式光伏支架。本研究方法适用于中国各个地区光伏电站的光伏支架成本及选型分析。     

平准化度电成本是不同发电技术经济性评价的通用参数

文中系统梳理了平准化度电成本(LCOE)的理论内涵和核算机制等,简述了LCOE目前的进展及存在的不足。LCOE合理剔除了不同发电技术初始投资和发电量的差异、以及财务和税收差异性,可以真实地反映不同发电技术经济性。在LCOE实际测算过程中,国内外对成本的测算差异较大;实际应用中,需要构建适合我国特点的核算体系,清晰成本纳入标准,充分考虑增值税、所得税及优惠政策等实际国情。     

光伏发电系统的LCOE及最优容配比分析

传统光伏发电系统的容配比一般按1:1及以下比例设计，因存在光资源不足、系统损耗、弃光限电等情况，常导致交流侧输出功率无法达到额定工况，从而造成资源浪费。以光资源实测数据的分析及处理为基础，解析计算光伏发电系统发电量及弃光率，创新性得到了弃光率、年均发电量、弃光电量等参数与容配比的函数关系，并以平准化度电成本(LCOE)为寻优目标，综合弃光率、光伏发电系统衰减率、直流侧损耗、项目增值税抵扣、运营成本等因素，采用曲线拟合方法定量分析了LCOE与容配比之间的强相关函数关系，进而确定了最优容配比。结果表明：通过曲线拟合方法，可得到准确的最小LCOE，进而确定最优容配比。     

超高海拔地区集中式光伏发电项目的经济与环境效益分析

为探讨集中式光伏发电项目在超高海拔地区运行的经济效益和环境效益,选用平准化度电成本(LCOE)和平准化度电净现值(LNPVE)作为经济效益评价指标,以能量回收期、年均节约标准煤量、污染物排放量作为环境效益评价指标,对全球首个建于超高海拔地区的集中式光伏发电项目的经济效益和环境效益进行了分析。分析结果显示：1)该项目的LCOE小于燃煤发电上网电价,说明该项目发电成本低,具有替代传统能源发电的潜力,可以实现最低价格的平价上网;LNPVE指标表明该项目能够实现对燃煤发电的替代,可以最低价格实现平价上网。2)该项目的能量回收期约为4.13年,年均节约标准煤约15.14万t,年均减少CO₂排放量约41.93万t、SO₂排放量约1.26万t、NO_x排放量约0.63万t,环境效益良好。该研究对于在超高海拔地区规模建设集中式光伏发电项目可提供良好的理论基础。     

Natural-gas fueled spark-ignition (SI) and compression-ignition (CI) engine performance and emissions

Natural gas is a fossil fuel that has been used and investigated extensively for use in spark-ignition (SI) and compression-ignition (CI) engines. Compared with conventional gasoline engines, SI engines using natural gas can run at higher compression ratios, thus producing higher thermal efficiencies but also increased nitrogen oxide (NO_x) emissions, while producing lower emissions of carbon dioxide (CO₂), unburned hydrocarbons (HC) and carbon monoxide (CO). These engines also produce relatively less power than gasoline-fueled engines because of the convergence of one or more of three factors: a reduction in volumetric efficiency due to natural-gas injection in the intake manifold; the lower stoichiometric fuel/air ratio of natural gas compared to gasoline; and the lower equivalence ratio at which these engines may be run in order to reduce NO_x emissions. High NO_x emissions, especially at high loads, reduce with exhaust gas recirculation (EGR). However, EGR rates above a maximum value result in misfire and erratic engine operation. Hydrogen gas addition increases this EGR threshold significantly. In addition, hydrogen increases the flame speed of the natural gas-hydrogen mixture. Power levels can be increased with supercharging or turbocharging and intercooling. Natural gas is used to power CI engines via the dual-fuel mode, where a high-cetane fuel is injected along with the natural gas in order to provide a source of ignition for the charge. Thermal efficiency levels compared with normal diesel-fueled CI-engine operation are generally maintained with dual-fuel operation, and smoke levels are reduced significantly. At the same time, lower NO_x and CO₂ emissions, as well as higher HC and CO emissions compared with normal CI-engine operation at low and intermediate loads are recorded. These trends are caused by the low charge temperature and increased ignition delay, resulting in low combustion temperatures. Another factor is insufficient penetration and distribution of the pilot fuel in the charge, resulting in a lack of ignition centers. EGR admission at low and intermediate loads increases combustion temperatures, lowering unburned HC and CO emissions. Larger pilot fuel quantities at these load levels and hydrogen gas addition can also help increase combustion efficiency. Power output is lower at certain conditions than diesel-fueled engines, for reasons similar to those affecting power output of SI engines. In both cases the power output can be maintained with direct injection. Overall, natural gas can be used in both engine types; however further refinement and optimization of engines and fuel-injection systems is needed.     

Performance assessment of some ice TES systems

In this paper, a performance assessment of four main types of ice storage techniques for space cooling purposes, namely ice slurry systems, ice-on-coil systems (both internal and external melt), and encapsulated ice systems is conducted. A detailed analysis, coupled with a case study based on the literature data, follows. The ice making techniques are compared on the basis of energy and exergy performance criteria including charging, discharging and storage efficiencies, which make up the ice storage and retrieval process. Losses due to heat leakage and irreversibilities from entropy generation are included. A vapor-compression refrigeration cycle with R134a as the working fluid provides the cooling load, while the analysis is performed in both a full storage and partial storage process, with comparisons between these two. In the case of full storage, the energy efficiencies associated with the charging and discharging processes are well over 98% in all cases, while the exergy efficiencies ranged from 46% to 76% for the charging cycle and 18% to 24% for the discharging cycle. For the partial storage systems, all energy and exergy efficiencies were slightly less than that for full storage, due to the increasing effect wall heat leakage has on the decreased storage volume and load. The results show that energy analyses alone do not provide much useful insight into system behavior, since the vast majority of losses in all processes are a result of entropy generation which results from system irreversibilities.     

Decomposition of limestone in a solar reactor

The thermal decomposition of limestone has been selected as a model reaction for developing and testing an atmospheric open solar reactor. The reactor consists of a cyclone gas/particle separator which has been modified to let the concentrated solar energy enter through a windowless aperture. The reacting particles are directly exposed to the solar irradiation. Experimentation with a 60 kW reactor prototype was conducted at PSI's 90m² parabolic solar concentrator, in a continuous mode of operation. A counter-current flow heat exchanger was employed to preheat the reactants. Eighty five percent degree of calcination was obtained for cement raw material and 15% of the solar input was converted into chemical energy (enthalpy).The technical feasibility of the solar thermal decomposition of limestone was experimentally demonstrated. The use of solar energy as a source for high-temperature process heat offers the potential of reducing significantly the CO₂ emissions from lime producing plants. Such a solar thermochemical process can find application in sunny rural areas for avoiding deforestation.     

Effect of co-cultivation of Chlamydomonas reinhardtii with Azotobacter chroococcum on hydrogen production

Chlamydomonas reinhardtii cc124 and Azotobacter chroococcum bacteria were co-cultured with a series of volume ratios and under a variety of light densities to determine the optimal culture conditions and to investigate the mechanism by which co-cultivation improves H₂ yield. The results demonstrated that the optimal culture conditions for the highest H₂ production of the combined system were a 1:40 vol ratio of bacterial cultures to algal cultures under 200 μE m^?2 s^?1. Under these conditions, the maximal H₂ yield was 255 μmol mg^?1 Chl, which was approximately 15.9-fold of the control. The reasons for the improvement in H₂ yield included decreased O₂ content, enhanced algal growth, and increased H₂ase activity and starch content of the combined system.     

Biohydrogen production by Anabaena sp. PCC 7120 wild-type and mutants under different conditions: Light, nickel, propane, carbon dioxide and nitrogen

Increasing awareness of environmental problems caused by the current use of fossil fuel-based energy, has led to the search for alternatives. Hydrogen is a good alternative and the cyanobacterium Anabaena sp. PCC 7120 is naturally able to produce molecular hydrogen, photosynthetically from water and light. However, this H₂ is rapidly consumed by the uptake hydrogenase.This study evaluated the hydrogen production of Anabaena sp. PCC 7120 wild-type and mutants: hupL⁻ (deficient in the uptake hydrogenase), hoxH⁻ (deficient in the bidirectional hydrogenase) and hupL⁻/hoxH⁻ (deficient in both hydrogenases) on several experimental conditions, such as gas atmosphere (argon and propane with or without N₂ and/or CO₂ addition), light intensity (54 and 152 ??Em⁻²s⁻¹), light regime (continuous and light/dark cycles 16 h/8 h) and nickel concentrations in the culture medium.In every assay, the hupL⁻ and hupL⁻/hoxH⁻ mutants stood out over wild-type cells and the hoxH⁻ mutant. Nevertheless, the hupL⁻ mutant showed the best hydrogen production except in an argon atmosphere under 16 h light/8 h dark cycles at 54 ??Em⁻²s⁻¹ in the light period, with 1 ??M of NiCl₂ supplementation in the culture medium, and under a propane atmosphere.In all strains, higher light intensity leads to higher hydrogen production and if there is a daily 1% of CO₂ addition in the gas atmosphere, hydrogen production could increase 5.8 times, related to the great increase in heterocysts differentiation (5 times more, approximately), whereas nickel supplementation in the culture medium was not shown to increase hydrogen production. The daily incorporation of 1% of CO₂ plus 1% of N₂ did not affect positively hydrogen production rate.     

Investigation of the thermodynamic and kinetic properties of La–Fe–B system hydrogen-storage alloys

La–Fe–B hydrogen-storage alloys were prepared using a vacuum induction-quenching furnace with a rotating copper wheel. The thermodynamic and kinetic properties of the La–Fe–B hydrogen-storage alloys were investigated in this work. The P–C–I curves of the La–Fe–B alloys were measured over a H₂ pressure range of 10⁻³ MPa to 2.0 MPa at temperatures of 313, 328, 343 and 353 K. The P–C–I curves revealed that the maximum hydrogen-storage capacity of the alloys exceeded 1.23 wt% at a pressure of approximately 1.0 MPa and temperature of 313 K. The standard enthalpy of formation ΔH and standard entropy of formation ΔS for the alloys' hydrides, obtained according to the van't Hoff equation, were consistent with their application as anode materials in alkaline media. The alloys also exhibited good absorption/desorption kinetics at room temperature.     

Exergetic evaluation of 5 biowastes-to-biofuels routes via gasification

This paper presents the exergy analysis results for the production of several biofuels, i.e., SNG (synthetic natural gas), methanol, Fischer–Tropsch fuels, hydrogen, as well as heat and electricity, from several biowastes generated in the Dutch province of Friesland, selected as one of the typical European regions. Biowastes have been classified in 5 virtual streams according to their ultimate and proximate analysis. All production chains have been modeled in Aspen Plus in order to analyze their technical performance. The common steps for all the production chains are: pre-treatment, gasification, gas cleaning, water–gas-shift reactions, catalytic reactors, final gas separation and upgrading. Optionally a gas turbine and steam turbines are used to produce heat and electricity from unconverted gas and heat removal, respectively. The results show that, in terms of mass conversion, methanol production seems to be the most efficient process for all the biowastes. SNG synthesis is preferred when exergetic efficiency is the objective parameter, but hydrogen process is more efficient when the performance is analyzed by means of the 1st Law of Thermodynamics. The main exergy losses account for the gasification section, except in the electricity and heat production chain, where the combined cycle is less efficient.     

The Solar Office in context

The goal of sustainability in buildings can only hope to be realised if buildings are designed to both conserve and generate energy. The Solar Office at Doxford International is designed to minimise the use of energy while its external fabric is designed to replace such energy that is used. The recently completed building is now subject of a comprehensive monitoring programme. The programme covers both the performance of the 73 kW_p photovoltaic installation and the environmental conditions within the building as a whole. Hour by hour findings are posted on a dedicated web site. Photovoltaics could have the same impact on building form and layout as the invention of the passenger lift at the end of the last century.     

液压系统常见的故障诊断及处理

任何工程机械式液压设备使用时出现故障是不可避免的。但是怎样确定故障的原因及找到好的解决方法，这是使用者最关心的问题。讲述了液压系统常见的故障及其排除方法。     

Hydrogen recovery from the photovoltaic electroflocculation-flotation process for harvesting Chlorella pyrenoidosa microalgae

In this paper, an integrated process using photovoltaic power to harvest microalgae by electro-flocculation (EF) and hydrogen recovery is presented. It is mainly favorable in regions with high solar radiation. The electro-flocculation efficiency (EFE) of Chlorella pyrenoidosa microalgae was investigated using various types of electrodes (aluminum, iron, zinc, copper and a non-sacrificial electrode of carbon). The best results regarding the EFE, and biomass contamination were achieved with aluminum and carbon electrodes where the electrical energy demand of the process for harvesting 1 kg of algae biomass was 0.28 and 0.34 kWh, respectively, while the energy yield of harvested hydrogen was 0.052 and 0.005 kWh kg^?1, respectively. The highest harvesting efficiency of 95.83 ± 0.87% was obtained with the aluminum electrode.The experimental hydrogen yields obtained were comparable with those calculated from theory. With a low net energy demand, microalgae EF may be a useful and low-cost technology.