关于定向光伏电池阵列布置间距的探讨

该文在讨论了接收直射辐射的起始高度角和可接收的散射辐射比例的基础上给出了一种计算阵列接收辐射总量的方法，并据此以场所内电池阵列的年总发电量和平均单位电价为评价指标，总结了定向光伏电池阵列布置间距的确定方法。     

太阳能光伏建筑能效影响因素及节能综合效益评价研究

面对全球不断增长的能源需求量和碳排放量,为了响应国家的“双碳”战略,大力发展光伏建筑一体化应用从而降低建筑能耗就显得尤为重要。通过对蒙商银行光伏系统进行研究,分析其太阳能利用能效,主要贡献和创新性有以下几点,其一,利用Matlab软件在全年典型气象条件下测算光伏系统全年发电量为439.43 MWh。其二,对光伏系统发电量影响较大的因素积灰量和安装角度进行动态分析,分析光伏不同安装角度和积灰量对发电量的影响。其三,利用e QUEST能耗模拟软件对全年逐时动态负荷与能耗进行模拟,得到安装光伏系统后,建筑全年总负荷降低362.89 MWh,全年建筑总能耗量下降529.74 MWh。其四,对光伏系统节能综合效益进行评价,得到光伏系统的年经济效益为25.12万元,生命周期内产生的环境效益为0.09元/k Wh。蒙商银行光伏系统的案例为城市中光伏建筑的推广及光伏产业政策的制定提供了借鉴。     

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。     

考虑时段耦合的带有蓄电池的用户光伏系统优化运行研究

考虑到光伏出力、负荷变化以及电价都有明显的以一天为周期的变化规律,建立以天为一个运行优化周期,一天内又可分为任意多个时段的带有时段耦合的配蓄电池的用户光伏系统的运行优化模型。该模型在整个优化周期表现为非线性模型或分段线性模型,通过控制变量分拆的方法将其改造为等价全局线性模型,以便运用高效快捷的线性规划单纯形算法对其求解。与非线性模型在相同条件下进行比较,该模型不仅可在分时电价、实时电价下得出最佳运行方案,更重要的是在运算时间上也有极强优势,所以不但可用于日前优化方案的制定,也可用超短时优化方案的制定。最后在某省现行分时电价下应用该模型预测了蓄电池配在光伏系统中可实现盈利的折旧费或投资成本。     

光伏阵列安装角度与安装节距的优化选择

光伏发电系统安装地点确定之后,其发电量主要受到光伏组件安装倾角和节距的影响。文章首先建立了光伏电池发电模型和斜面上的辐照度模型,以西安某公司的光伏发电系统为例,计算了不同倾角和节距下光伏阵列的年发电量。结果表明:在没有阴影遮挡的情况下,光伏组件在西安地区的最佳安装倾角为32°;在有阴影遮挡的情况下,节距越小,最佳倾角越小。光伏阵列的节距减小时,组件的发电量减少,利用效率降低。但是,由于组件安装量增多,单个组件占地面积减少,总安装容量增大,发电量增大。此计算方法可为光伏组件安装倾角和节距的选择提供参考。     

城镇典型住宅建筑屋顶分布式光伏系统潜能分析

以中国8个地区的多层住宅建筑为例,以典型气象年数据计算光伏发电和建筑能耗,采用PVsyst软件完成分布式光伏系统设计,Energy Plus软件建立多层建筑能耗模型,以电能自治度、碳减排量和经济分析指标净现值(NPV)、效益成本比(BCR)进行分析。结果表明,昆明和拉萨分布式光伏对建筑的贡献程度最高,三亚最低;哈尔滨和拉萨碳减排收益潜能高;8个地区分布式光伏系统在不同系统配置和运行方式下经济性存在差异,但普遍选择自用比例为30%的收益最高。综上,处于Ⅱ类太阳资源区下的温和地区和Ⅰ类下的寒冷地区光伏贡献程度高,夏热冬暖地区低;在发电量较少和销售-上网电价差异较大地区光伏的系统配置及运行方式对经济性影响大。     

我国光伏政策的回顾和展望(下)

正5分布式光伏的政策演变2013年的电价政策本意是希望优先发展东部地区的分布式光伏。能源局给出的分布式光伏定义是:接入35 k V及以下电压等级电网,且单个系统装机容量小于2 MW的光伏系统。因此,对于那些接入35 k V或10 k V公共配电网的系统,即使所发电量全部卖给电网,也只能享受每k Wh脱硫标杆电价+0.42元的电价(约只有0.7~0.8元/k Wh)。除此之外,还有其他执行中的障碍:1)大部分建筑光伏项目收益低——60%以     

基于图形逻辑分析的光伏储能系统能量管理方法

考虑现阶段市场普遍采用的峰谷分时阶梯电价机制,该文给出一种基于图形逻辑分析方法,以应用双向逆变器的光伏储能系统用户日用电消费最低为目的创新型能量管理方法。该方法通过分析每日用户用电量与光伏发电量,储能系统状态,结合现行电价与光伏补贴价格,设计光伏储能系统电能的合理流动及控制算法。利用电力公司的用户用电量、光伏发电量数据及上海市实际电价,验证该图形逻辑分析方法的有效性。计算表明在该方法控制下用户日用电消费明显降低;运算速度在相同仿真计算平台下,相比于普通寻优方法显著提高。     

太阳光入射角差异对不同气候区立面垂直安装光伏组件发电量的影响研究

对于安装在不同地区、以不同倾角安装的光伏组件来说，全年的太阳光入射角差异较大，而太阳光入射角的变化会极大影响光伏组件的发电量情况。基于入射角修正模型，分析了中国不同气候区因太阳光入射角差异而引起的立面垂直安装光伏组件的发电量和地面最佳倾角安装光伏组件的发电量变化及差异，并通过相对偏差对二者的发电量差异进行了量化。研究结果表明：立面垂直安装光伏组件的年发电量比地面最佳倾角安装光伏组件的年发电量低，且随着光伏组件安装地区纬度的降低，二者的发电量差值逐渐增大。低纬度地区立面垂直安装光伏组件的年发电量与地面最佳倾角安装光伏组件的年发电量的相对偏差较大。研究结果对指导光伏发电系统设计意义重大。     

光伏电站内不同光伏支架形式数量占比的研究

光伏支架形式不同时会对土建工程量、电气工程量等产生一定影响。针对位于不同太阳能资源区的光伏电站,在光伏电站总装机容量不变的情况下,根据固定式与平单轴跟踪式光伏支架数量占比的变化趋势,对光伏电站全寿命周期内2种光伏支架形式在不同数量占比下的光伏电站初始投资额与25年平均发电量的增益值及增幅进行计算,并得出对应的光伏电站发电量及土建工程量、电气工程量等的变化趋势;最后得出在不同太阳能资源区光伏电站全寿命周期内全资财务内部收益率(税后)较优(大于等于8%)时平单轴跟踪式光伏支架的数量占比范围,为工程建设的最经济性投资提供参考依据。     

Photovoltaic modules in buildings: Performance and safety

Many PV systems exhibit a poorer performance as is to be expected using installed peak power. Performance ratios of ‘reasonable’ systems have experimentally been determined in the range of 60%–85% of STC (=standard test conditions) performance. A significant part of the losses is due to the performance deviation of PV modules from their rating at STC due to the outdoor conditions (realistic reporting conditions, RRC). This is due to low light level dependence, temperature coefficients, nominal operating cell temperatures and reflectivity at the module surface. Due to the special operating conditions, this is of special importance if PV modules are integrated into buildings. To overcome the problems in module performance evaluation and to assist system sizing, a realistic PV efficiency map and performance data for commercial PV modules are presented. In a similar way as the European radiation atlas for solar irradiation, this RRC market survey of PV modules gives detailed information on module performance at many sites for various installation conditions.As the International Electrotechnical Commission is currently preparing a new international standard, dealing with the safety of PV modules in a variety of application classes, performance data on PV modules is supplemented by information on possible module safety tests and module integration into buildings.     

Opportunities for utilization of stand-alone hybrid (photovoltaic + diesel + battery) power systems in hot climates

There is a growing awareness that combustion fuels are a limited resource and burning of these fuels is the principal cause of air pollution, and possibly environmental warming. This recognition is elevating interest and activity toward the development and application of alternative/renewable sources of energy, such as solar energy to displace some of the use of fossil fuels. In this context, Saudi Arabia being enriched with fairly high degree of solar radiation, is a suitable candidate for deployment of solar photo-voltaic (PV) panels for power generation in crisis. Literature shows that residential buildings in Saudi Arabia consume about 47% of the total electric energy generated/consumed. In the present study, hourly mean solar radiation data for the period 1986–1993 recorded at the solar radiation and meteorological monitoring station, Dhahran (26° 32’ N, 50°13’ E), Saudi Arabia, have been analyzed to examine/investigate the potential of utilizing hybrid (PV + diesel) power systems to meet the load requirements of a typical residential building (with annual electrical energy demand of 35 200 kWh). The monthly average daily values of solar global irradiation for Dhahran range from 3.61 kwh/m² to 7.96 kwh/m². The hybrid systems considered in the present analysis consist of different combinations of PV panels/modules (different array sizes) supplemented with battery storage unit and diesel back-up. The study shows that with 225 m² PV together with 12 h of battery storage, the diesel back-up system has to provide 9% of the load demand. However, in absence of battery bank, about 58% of the load needs to be provided by the diesel system.     

Prospects of autonomous/stand-alone hybrid (photo-voltaic + diesel + battery) power systems in commercial applications in hot regions

Most of the world’s energy consumption is greatly dependent on fossil fuel, which is exhaustible and is being used extensively due to continuous escalation in the world’s population and development. This valuable resource needs to be conserved and its alternatives need to be explored. In this perspective, dissemination and utilisation of renewables such as solar energy has gained worldwide momentum since the onset of oil crises of 1970s. Moreover, burning of fuels is the principal cause of air pollution, and possibly environmental warming. Saudi Arabia, being blessed with a fairly high level of solar radiation, is a suitable candidate for deployment of solar photo-voltaic (PV) panels for power generation during crisis. Literature indicates that commercial/residential buildings in Saudi Arabia consume an estimated 10–45% of the total electrical energy generated/consumed. In the present study, hourly mean solar radiation data for the period 1986–1993 recorded at the solar radiation and meteorological monitoring station, Dhahran (26° 32′ N, 50° 13′ E), Saudi Arabia, have been analyzed to investigate the potential of utilizing hybrid (PV+diesel) power systems to meet the load requirements of a typical commercial building (with an annual electrical energy demand of 620,000 kWh). The monthly average daily solar global irradiation for Dhahran ranges from 3.61 to 7.96 kWh/m². The hybrid systems considered in the present analysis consist of different combinations of PV panels/modules (different array sizes) supplemented with a battery storage unit and diesel back-up. The study shows that with a combination of 3700 m² PV together with 12 h of battery storage, the diesel back-up system has to provide 6% of the load demand. However, in the absence of a battery bank, about 56% of the load needs to be provided by the diesel system.     

Critical factors affecting the photovoltaic characteristic and comparative study between two maximum power point tracking algorithms

This paper presents the characterization and the modeling of the electric characteristics of currentvoltage and power–voltage of the photovoltaic (PV) panels. The philosophy behind digital simulation of solar energy systems is that experiments which normally should be done on real systems under high assembling costs can be done numerically in a short time on a computer, thus saving time and investments. The electric parameters of PV cells and the optimal electric quantities of PV panels have been analyzed (voltage and power) according to the meteorological variations (Temperature, solar irradiation …). The obtained results show that the diode parameters of the PV cells depend on solar irradiation: the current saturation increases with solar irradiation. This induces a decrease of the optimal voltage with solar irradiation; when the solar irradiation varies from 600 W/m² to 1000 W/m². By taking into consideration all the modeling results, the electric behavior of the cells association in parallels or in series, as well as the aging of a PV panel have been analyzed. Moreover, a comparative study between two types of MPPT techniques that are used in photovoltaic systems to extract the maximum power have been introduced which are Perturb and Observe (P &O) and Incremental Conductance (INC).     

串并联太阳能电池弧形光伏组件的发电性能研究

将弧形光伏组件安装在建筑和汽车上获取电能,已受到人们越来越多的关注。为获得更高的输出功率,有必要研究由互连太阳能电池组成的、电流不匹配的弧形光伏组件的特性。研究重点关注由串并联太阳能电池组成的弧形光伏组件的发电性能,设计了不同曲率的非平面微型光伏模块,并通过测量获取光伏模块的参数。与平面光伏模块相比,弧形光伏模块的发电量较小。此外,利用二极管模型分析了光伏模块的特性,说明并联比串联功率高的原因。最后研究了实际应用中太阳能电池的互连问题。结果表明,在理想模型下并联能获取更多电能,但大尺寸的光伏模块会产生更大电流,可能会在实际运行中产生额外损耗。因此,在实际应用中设计弧形光伏组件时也应考虑太阳能电池的互连。     

Hybrid photovoltaic/thermal solar systems

We present test results on hybrid solar systems, consisting of photovoltaic modules and thermal collectors (hybrid PV/T systems). The solar radiation increases the temperature of PV modules, resulting in a drop of their electrical efficiency. By proper circulation of a fluid with low inlet temperature, heat is extracted from the PV modules keeping the electrical efficiency at satisfactory values. The extracted thermal energy can be used in several ways, increasing the total energy output of the system. Hybrid PV/T systems can be applied mainly in buildings for the production of electricity and heat and are suitable for PV applications under high values of solar radiation and ambient temperature. Hybrid PV/T experimental models based on commercial PV modules of typical size are described and outdoor test results of the systems are presented and discussed. The results showed that PV cooling can increase the electrical efficiency of PV modules, increasing the total efficiency of the systems. Improvement of the system performance can be achieved by the use of an additional glazing to increase thermal output, a booster diffuse reflector to increase electrical and thermal output, or both, giving flexibility in system design.     

Estimation of the energy of a PV generator using artificial neural network

The integration of grid-connected photovoltaic (GCPVS) systems into urban buildings is very popular in industrialized countries. Many countries enhance the international collaboration efforts which accelerate the development and deployment of photovoltaic solar energy as a significant and sustainable renewable energy option. A previous method, based on artificial neural networks (ANNs), has been developed to electrical characterisation of PV modules. This method was able to generate V–I curves of si-crystalline PV modules for any irradiance and module cell temperature. The results showed that the proposed ANN introduced a good accurate prediction for si-crystalline PV modules performance when compared with the measured values. Now, this method, based on ANNs, is going to be applied to obtain a suitable value of the power provided by a photovoltaic installation. Specifically this method is going to be applied to obtain the power provided by a particular installation, the “Univer generator”, since modules used in these works were the same as the ones used in this photovoltaic generator.     

Optimal angles for harvesting solar electricity in some African cities

In recent years, the quest for renewable and sustainable energy has been extensive while solar energy has been on the vanguard of sustainable alternative and renewable energy sources due to its clean nature and cost effectiveness for most human activities such as water pumping and electric power generation, amongst others. The off beam installation of Photovoltaic (PV) modules has posed a severe challenge to the optimal functioning of these PV cells despite the abundance of solar irradiation receivable in most African cities. This paper presents the Optimal Inclination Angles (OIA) for mounting PV modules in the absences of a mechanized or automated solar tracking device, for optimum yield in solar electricity generation for some selected African cities using the Photovoltaic Geographic Information Systems (PVGIS) dataset. The OIA of the selected African cities has been identified for optimal solar irradiation exploitation and if the modules are mounted on a horizontal plane, it is expected that considerable amount of solar irradiation would not be harnessed as it has been estimated using the difference from the Irradiation on OIA (Hopt) and the Irradiation on horizontal plane (Hh), whose difference shows that the northern African cities, Algiers, Rabat and Tripoli, are seen to have high levels in unutilized solar irradiation of 780 Wh/m², 760 Wh/m² and 680 Wh/m² respectively while Harare, Lusaka, Maiduguri, Khartoum, Maputo and Luanda would have considerably high levels in untapped solar irradiation of 360Wh/m², 330 Wh/m², 180 Wh/m², 260 Wh/m², 570 Wh/m² and 80 Wh/m² respectively if PV modules are mounted on horizontal plane. However cities such as Bangui, Abidjan and Mogadishu have quite low levels in unexploited solar irradiation of 40 Wh/m², 70 Wh/m² and 10 Wh/m² respectively when PV modules are mounted on horizontal plane. These differences show the amount of solar irradiation which if adequately harnessed, adds to the solar energy potentials of the region.     

The risk of power loss in crystalline silicon based photovoltaic modules due to micro-cracks

Micro-cracks in wafer based silicon solar cell modules are nowadays identified by a human observer with the electroluminescence (EL) method. However, the essential question of how the micro-cracks affect the PV module performance has yet to be answered. We experimentally analyze the direct impact of micro-cracks on the module power and the consequences after artificial aging. We show that the immediate effect of micro-cracks on the module power is small, whereas the presence of micro-cracks is potentially crucial for the performance of the module after artificial ageing. This confirms the necessity to develop the means of quantifying the risk of power loss in PV modules with cracked solar cells in their lifetime, in order to enable manufacturers to discard defective modules with high risk of failure while keeping modules with uncritical micro-cracks. As a first step towards risk estimation we develop an upper bound for the potential power loss of PV modules due to micro-cracks in the solar cells. This is done by simulating the impact of inactive solar cell fragments on the power of a common PV module type and PV array. We show that the largest inactive cell area of a double string protected by a bypass diode is most relevant for the power loss of the PV module. A solar cell with micro-cracks, which separate a part of less than 8% of the cell area, results in no power loss in a PV module or a PV module array for all practical cases. In between approximately 12 and 50% of inactive area of a single cell in the PV module the power loss increases nearly linearly from zero to the power of one double string.     

Inverter sizing of grid-connected photovoltaic systems in the light of local solar resource distribution characteristics and temperature

Inverter sizing strategies for grid-connected photovoltaic (PV) systems often do not take into account site-dependent peculiarities of ambient temperature, inverter operating temperature and solar irradiation distribution characteristics. The operating temperature affects PV modules and inverters in different ways and PV systems will hardly ever have a DC output equal to or above their STC-rated nominal power. Inverters are usually sized with a nominal AC output power some 30% (sometimes even more) below the PV array nominal power. In this paper, we show that this practice might lead to considerable energy losses, especially in the case of PV technologies with high temperature coefficients of power operating at sites with cold climates and of PV technologies with low temperature coefficients of power operating at sites with warm climates and an energy distribution of sunlight shifted to higher irradiation levels. In energy markets where PV kW h’s are paid premium tariffs, like in Germany, energy yield optimization might result in a favorable payback of the extra capital invested in a larger inverter.This paper discusses how the time resolution of solar radiation data influences the correct sizing of PV plants.We demonstrate that using instant (10 s) irradiation values instead of average hourly irradiation values leads to considerable differences in optimum inverter sizing. When calculating inverter yearly efficiency values using both, hourly averages and 1-min averages, we can show that with increased time resolution of solar irradiation data there are higher calculated losses due to inverter undersizing. This reveals that hourly averages hide important irradiation peaks that need to be considered.We performed these calculations for data sets from pyranometer readings from Freiburg (48°N, Germany) and Florianopolis (27°S, Brazil) to further show the peculiarities of the site-dependent distribution of irradiation levels and its effects on inverter sizing.