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。     

光伏发电项目LCOE的研究与思考

针对光伏发电项目的平准化度电成本(LCOE)展开研究,介绍了其相关概念,分析了其各个影响因素;并有针对性地提出了降低LCOE的相关方法和建议。研究结果显示：1)在目前的市场行情下,光伏发电项目LCOE的3个组成部分中,初始投资部分LCOE的占比最大,达到了72%～76%;2)发电量是项目LCOE非常敏感的影响因素,应寻找光照资源条件较好的地区建设光伏发电项目,并且减少弃光率,提升上网电量,有助于降低项目LCOE;3)折现率对项目LCOE的影响很大,但其与项目本身无关,主要取决于行业的基准收益率和项目投资者设定的项目预期收益率;4)光伏发电系统年衰减率和运维成本对项目LCOE的影响不大;5)寻找融资利率低的贷款可在一定程度上降低项目LCOE;6)降低项目初始投资和提升发电量是降低项目LCOE最主要的两个途径,也是光伏工作者最需要努力的两个方向。以期研究结果可为光伏发电技术的发展和光伏发电项目的开发建设提供参考。     

光伏阵列倾角与土地成本双因素影响下的光伏发电项目经济性分析研究

采用PVsyst软件,对光伏阵列倾角与土地成本双因素影响下的光伏发电项目经济性进行了研究和分析,分析了光伏阵列倾角与倾斜面上总太阳辐射量及光伏发电项目实际发电量的关系,计算了不同光伏阵列倾角和不同单位土地租金下光伏场区占地面积、土地年租金,以及光伏发电项目的平准化度电成本(LCOE)。研究结果表明：在光伏阵列倾角及土地成本双因素的共同影响下,随着光伏阵列倾角的增大,项目的 LCOE呈先下降后上升的趋势,存在一个光伏阵列倾角使LCOE最优,且该光伏阵列倾角与项目发电量最高时对应的光伏阵列倾角可能不同。不同单位土地租金下,项目的 LCOE最优时对应的光伏阵列倾角可能不同,随着单位土地租金提高,项目的 LCOE最优时对应的光伏阵列倾角逐渐降低。     

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。     

四川省某光伏发电项目的光伏支架选型设计

以2021年建设的四川省某光伏发电项目为例,针对其光伏支架选型设计,利用平准化度电成本(LCOE)对该项目分别采用固定倾角式、固定可调式、平单轴和带倾角的平单轴4种光伏支架进行定量分析,从而得到LCOE最低时的光伏支架方案。结果显示：本项目在地势平坦区域推荐安装采用2P方案(2块光伏组件竖排)的平单轴光伏支架,其他区域推荐安装固定倾角式光伏支架。     

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。     

Ash-forming elements in four Scandinavian wood species. Part 1: Summer harvest

Woody biomass in Finland and Sweden comprises mainly four wood species: spruce, pine, birch and aspen. To study the ash, which may cause problems for the combustion device, one tree of each species were cut down and prepared for comparisons with fuel samples. Well-defined samples of wood, bark and foliage were analyzed on 11 ash-forming elements: Si, Al, Fe, Ca, Mg, Mn, Na, K, P, S and Cl. The ash content in the wood tissues (0.2–0.7%) was low compared to the ash content in the bark tissues (1.9–6.4%) and the foliage (2.4–7.7%). The woods’ content of ash-forming elements was consequently low; the highest contents were of Ca (410–1340 ppm) and K (200–1310), followed by Mg (70–290), Mn (15–240) and P (0–350). Present in the wood was also Si (50–190), S (50–200) and Cl (30–110). The bark tissues showed much higher element contents; Ca (4800–19,100 ppm) and K (1600–6400) were the dominating elements, followed by Mg (210–2400), P (210–1200), Mn (110–1100) and S (310–750), but the Cl contents (40–330) were only moderately higher in the bark than in the wood. The young foliage (shoots and deciduous leaves) had the highest K (7100–25,000 ppm), P (1600–5300) and S (1100–2600) contents of all tissues, while the shoots of spruce had the highest Cl contents (820–1360) and its needles the highest Si content (5000–11,300). This paper presented a new approach in fuel characterization: the method excludes the presence of impurities, and focus on different categories of plant tissues. This made it possible to discuss the contents of ash element in a wide spectrum of fuel-types, which are of large importance for the energy production in Finland and Sweden.     

Contents in Volume 23,2014

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NEXT GENERATION ENGINEERED MATERIALS FOR ULTRA SUPERCRITICAL STEAM TURBINES

正1 ABSTRACT To reduce the effect of global warming on our climate,the levels of CO2emissions should be reduced.One way to do this is to increase the efficiency of electricity production from fossil fuels.This will in turn reduce the amount of CO2emissions for a given power output.Using US practice for efficiency calculations,then a move from a typical US plant running at 37%efficiency to a 760℃/38.5 MPa(1 400/5 580 psi)plant running at 48%efficiency would reduce CO2emissions by 170kg/MW.hr or 25%.     

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.     

Aerodynamic performance effects of leading-edge geometry in gas-turbine blades

The purpose of this paper is to illustrate the advantages of the direct surface-curvature distribution blade-design method, originally proposed by Korakianitis, for the leading-edge design of turbine blades, and by extension for other types of airfoil shapes. The leading edge shape is critical in the blade design process, and it is quite difficult to completely control with inverse, semi-inverse or other direct-design methods. The blade-design method is briefly reviewed, and then the effort is concentrated on smoothly blending the leading edge shape (circle or ellipse, etc.) with the main part of the blade surface, in a manner that avoids leading-edge flow-disturbance and flow-separation regions. Specifically in the leading edge region we return to the second-order (parabolic) construction line coupled with a revised smoothing equation between the leading-edge shape and the main part of the blade. The Hodson–Dominy blade has been used as an example to show the ability of this blade-design method to remove leading-edge separation bubbles in gas turbine blades and other airfoil shapes that have very sharp changes in curvature near the leading edge. An additional gas turbine blade example has been used to illustrate the ability of this method to design leading edge shapes that avoid leading-edge separation bubbles at off-design conditions. This gas turbine blade example has inlet flow angle 0°, outlet flow angle −64.3°, and tangential lift coefficient 1.045, in a region of parameters where the leading edge shape is critical for the overall blade performance. Computed results at incidences of −10°,   −5°,   +5°,   +10° are used to illustrate the complete removal of leading edge flow-disturbance regions, thus minimizing the possibility of leading-edge separation bubbles, while concurrently minimizing the stagnation pressure drop from inlet to outlet. These results using two difficult example cases of leading edge geometries illustrate the superiority and utility of this blade-design method when compared with other direct or inverse blade-design methods.     

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.     

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.     

Controls on the Karaha–Telaga Bodas geothermal reservoir,Indonesia

Karaha–Telaga Bodas is a partially vapor-dominated, fracture-controlled geothermal system located adjacent to Galunggung Volcano in western Java, Indonesia. The geothermal system consists of: (1) a caprock, ranging from several hundred to 1600 m in thickness, and characterized by a steep, conductive temperature gradient and low permeability; (2) an underlying vapor-dominated zone that extends below sea level; and (3) a deep liquid-dominated zone with measured temperatures up to 353 °C. Heat is provided by a tabular granodiorite stock encountered at about 3 km depth. A structural analysis of the geothermal system shows that the effective base of the reservoir is controlled either by the boundary between brittle and ductile deformational regimes or by the closure and collapse of fractures within volcanic rocks located above the brittle/ductile transition. The base of the caprock is determined by the distribution of initially low-permeability lithologies above the reservoir; the extent of pervasive clay alteration that has significantly reduced primary rock permeabilities; the distribution of secondary minerals deposited by descending waters; and, locally, by a downward change from a strike-slip to an extensional stress regime. Fluid-producing zones are controlled by both matrix and fracture permeabilities. High matrix permeabilities are associated with lacustrine, pyroclastic, and epiclastic deposits. Productive fractures are those showing the greatest tendency to slip and dilate under the present-day stress conditions. Although the reservoir appears to be in pressure communication across its length, fluid, and gas chemistries vary laterally, suggesting the presence of isolated convection cells.     

Hydrogen production by steam-gasification of carbonaceous materials using concentrated solar energy – V. Reactor modeling,optimization, and scale-up

A chemical reactor for the steam-gasification of carbonaceous particles (e.g. coal, coke) is considered for using concentrated solar radiation as the energy source of high-temperature process heat. A two-phase reactor model that couples radiative, convective, and conductive heat transfer to the chemical kinetics is applied to optimize the reactor geometrical configuration and operational parameters (feedstock's initial particle size, feeding rates, and solar power input) for maximum reaction extent and solar-to-chemical energy conversion efficiency of a 5 kW prototype reactor and its scale-up to 300 kW. For the 300 kW reactor, complete reaction extent is predicted for an initial feedstock particle size up to 35 μm at residence times of less than 10 s and peak temperatures of 1818 K, yielding high-quality syngas with a calorific content that has been solar-upgraded by 19% over that of the petcoke gasified.     

Assessment methods of material ageing using Sdobyrev''s creep rupture model

The physical aspects of the activation energy, in higher and high temperatures, of the metal creep process were examined. The research results of creep-rupture in a uniaxial stress state and the criterion of creep-rupture in biaxial stress states, at two temperatures, are then presented. For these studies creep-rupture, taking case iron as an example the energy and pseudoenergy activation was determined. For complex stress states the criterion of creep-rupture was taken to be Sdobyrev's, i.e. σ_red = σ₁ β + (1 − β)σ_i, where: σ₁-maximal principal stress, σ_i-stress intensity, β-material constant (at variable temperature β = β(T)). The methods of assessment of the material ageing grade are given in percentages of ageing of new material in the following mechanical properties: 1) creep strength in uniaxial stress state, 2) activation energy in uniaxial stress state, 3) criterion creep strength in complex stress states, 4) activation pseudoenergy in complex stress states. The methods 1) and 3) are the relatively simplest because they result from experimental investigations only at nominal temperature of the structure work, however, for methods 2) and 4) it is necessary to perform the experimental investigations at least at two temperatures.