The Photovoltaic Energy Calculation Engineering Essay

The Photovoltaic Energy Calculation Engineering EssayWe utilise the design PVSYST in range to answer for accurately the output of our photovoltaic installation. PVSYST was the precisely curriculumme we had access to and it is a really widely known industrial curriculum for sizing and designing photovoltaic corpses. We give the more or less up to date version of 5.0.6.ProcedureFirst from the main menu in a mettlesomeer place we claim project design and we select the stand alone system because ours is non connected with an existing grid (i.e. electrical generator)In sight to create a project in PVSYST, present is the Eco-fri completionly bulk carrier, we fuddle to defineThe project name, which will identify the project in the point list in our data library.The geo chartical location.The hourly Meteo file, which is precondition from the program.A geographical site is delineate byits name, country, and world region,its geographical co-ordinates latitude, longitude, aggrandisement and time-zone, periodical meteorological data.To be used in the simulation, the minimum meteorological data includethe monthly Global horizontal radiationMonthly averages of the ambient temperature.Meteo economic apprize argon displayed and easily delimit on the screen. It is to be noted that for the verification of alternatively uncertain data, the clearness index Kt is in all aspect displayable, which is the irradiation actually received on earth, normalised to extra-terrestrial irradiation in monthly economic values. The monthly average of Kt should ordinarily lie mingled with about Kt = 0.25 and Kt = 0.75 at any place (PVSYST heedlessnesss). Monthly meteo values give the bounce be used as a basis for the generation of synthetic daily data. past we generate a graph for the ad hoc site (i.e. Broome)Where, the blue rail focussing system is the clear side factual day model (irradiation values with clear sky).The above graph shows us graphically the ir radiation sum per month (diffuse and globose) with daily modification values.The Clearness Index Kt for BroomeWe back tooth see that the values range from 0.25 to 0.75The ambient temperature changes through the year.The above graphs were generated by the program from the down the stairs table also it is interesting to show the solar path at Broome or what is the solar height with respect of the knock off through the day in order to belowstand how the sun moves from east to watt. The graph also shows some termination dates (denoted as 1 to 7) where the sun changes heightOur next metre to the program is to find the albedo CoefficientThe albedo coefficient is the fraction of global resultant irradiation reflected by the ground in front of a be given plane. This substance takes place during the reversal computation of the horizontal irradiation onto a tilted plane. The albedo seen by the plane is of course null for a horizontal plane, and increases with tilt.In the project definition, the albedo values can be familiarized each month in order to take any trustworthyistic snow-cover into consideration. The value usually admitted in the urban localities is of the order of 0.14 to 0.22, and can go up till 0.8 for a snow-cover. Ideally, the best value is obtained by a direct measurement on the site. But in practice, except for unsloped planes, this value does not take on any great importance as the albedo component is relatively weak in the incident global irradiation (this contri barelyion can be visualised in the results of the simulation). The following table gives some usual values for the albedoWe used the 0.35 value of the Albedo coefficient because it matches on our material.After defining the above values through the program we proceeded to the orientation of our PV plane. Our project consist a stiff tilted plane (The plane tilt is defined as the shift between the plane and the horizontal), because we considered placing the panels at the hat ches imputable to the fact that they would be candid all day to the suns radiation. PVs are placed onto the hatches of the ship with zero tilt (Azimuth is zero as tumefy because it doesnt affect the global on storage shelling plane output. In northern hemisphere, the plane azimuth is defined as the angle between south and accumulator plane. In southern hemisphere, the plane azimuth is defined as the angle between north and collector plane).As the program calculated, our waiver with respect to an optimum orientation is 3.8% and the gettable irradiation on this tilted plane is 2370kWh/m2We also considered using mixed configurations of panels as to maximise the output per m2 before choosing the above configuration. The below configurations was spurned due to the sun is changing place constantly throughout the day and the ships movement reinforces the situation, we decided that the best configuration was the above due to toughened design (one panel placed along the hatch), high efficiency (sun always hit the panel at any time) and simple installation.Using ii panels on each hatch half, tilted for 25o each having an output of 2445 kWh/m2 and the overtaking to an optimum orientation is 0.7%. Sun hit the panels and east and west when the ship goes north. (Highest efficiency, complex design, not easy installation).Using two panels on each half, tilted for above 25o the output is greatly decreased and we pay great dismissal to an optimum orientation.The next step is to calculate the close to blends effect or shading. Near shadings are partial shadings which affect just a part of the field. The shaded part changes during the day and over the seasons. We call shading divisor the ratio of the illuminated part to the total area of the field, or inversely shading loss is its equilibrize.Through the construction/perspective ray of light we created a model of the ship from the ships particulars with the PVs installed on it in order to calculate the shadin g loss we obligate in various positions of the shipThe real effect of partial shadings on the electrical production of the PV field is non-linear, and depends on the interconnections between the modules. In the PV adjust, the current of each cell string along is bound by the current of the worst cell in the series. That is, when one only cell is shaded the entire string is strongly affected (which has also dramatic effects on the I/V(current/voltage) characteristics of the whole align). Even with by-pass protection diodes, this string does not participate more than slightly in the production of the PV array. This phenomenon is likewise complex to be treated in great detail . Nevertheless, the program provides a simplified method, giving the possibility of partitioning the field into rectangles, each of which supposed to represent a string of modules in series. Then it calculates a Shading factor fit in to strings, stating that as soon as a string is hit by a shadow, the enti re string (rectangle) is considered as electrically unproductive. Although not perfect, this approach should give an upper limit for the real shading loss evaluation. In practice, one a great deal observe that (except for level(p) arrangements like sheds), this upper limit is not so far from the set down limit (that is, the linear loss).And the losings percentage due to shading in any sun height.After we define the natural parameters, we proceeded to the system phthisis during a month in the specific site (BROOME). We cannot gift the supreme load 669.64 kW because it is the 100% and it is impossible to achieve it, barely we apply an acceptable amount of about 20% of the max output which is 140Kw as a fit(p) load for 12 hours.After that we proceed to barrage set and module selectionWhereLOL Loss-of-load probabilityThis value is the probability that the drug users need cannot be supplied (i.e. the time fraction when the battery is disconnected due to the offset charge regul ator security). It may be understood as the complement of the Solar fraction (although it is described in terms of time rather than dynamism). During the sizing process, the LOL requirement allows for determining the PV array size needed, for a given battery mental object. Here the default program value is 5% which is acceptable. impropriety and battery sizingIn the Presizing process, the proposed battery pack capacity is firm according to the required liberty of the system, given in days.The autonomy is defined as the time during which the load can be met with the battery alone, without any solar inputs, starting of course from a full charged battery state. With non-constant loads (seasonal or monthly definition, weekly use), this is accounted as the worst case over the year. The calculation takes the minimum state of charge (SOC) disconnecting threshold, and the battery energy efficiency into account.For our project we decided that 4 days is enough autonomy for our ship.Batter y Voltage ChoiceIn a stand-alone PV system with direct coupling to the user (without inverter), the battery voltage determines the distribution voltage. As now many DC instruments can be found as well in 24V as in 12V, this choice should be make according to system and/or appliance power, as well as the extension of the planned distribution grid to minimise the ohmic outfit losses.This choice should be done from the early planning of an installation, since the existing appliance voltage usually cannot be changed, and voltage translators will be expensive and not 100% efficient.The rated distribution values could be chosen according to the following criteria (inverter supposed directly connected on the battery pack)12V particular systems for lighting and TV tool max power 24V medium size, with fridge and little appliances, or fit out extension to more than 10 m. Appliance max power 48V special industrial or agricultural use Appliance max power Higher powers require either high D C voltages (special appliances) or AC feeding through inverter. Here we choose 440VThe module which we choose was the highest output monocrystalline silicon module in the program database, from SunPower company, constructed in 2009 the specifications of the module areThe batteries specification ,model and ManufaturerContinuing below is a brief sketch of the systemThe battery operating temperature was set to a fixed value of 20oC and the program let us use a default regulator with a DC-DC converter which specs are above. part Losses get losses in PVSYST programArray loss parameters are initially set to reasonable default values by the program, so that modifications only need to be performed during a second step of the system study.PVSYST treats in detail the following loss types in a PV arrayThermal lossesOhmic wire losses staff flavor lossesMismatch lossesIncidence angle (IAM) losses.In the simulation results, the effect of each loss will be in stock(predicate) in hourly, daily or monthly values. They may be image on the Loss diagram.Array Thermal lossesThermal formThe thermic behaviour of the field which strongly influences the electrical performances is decided by a thermal balance between ambient temperature and cells heating up due to incident irradianceU (Tcell Tamb) = alpha Ginc (1 Effic)Where Alpha is the absorption coefficient of solar irradiation, and Effic is the PV efficiency (related to the module area), i.e. the removed energy from the module. The usual value of the submersion coefficient Alpha is 0.9.When possible, the PV efficiency is calculated according to the operating conditions of the module. Otherwise it is taken as 10%.The thermal behaviour is characterised by a thermal loss factor designed here by U (formerly called K-value), which can be splitted into a constant component Uc and a factor proportionate to the swerve speed UvU = Uc + Uv v (U in W/mk, v = construction fastness in m/s).These factors depend on the mounti ng mode of the modules.For free circulation, this coefficient refers to both faces, i.e. twice the area of the module. If the patronize of the modules is more or less thermally insulated, this should be press downed, theoretically up to half the value (i.e. the back side doesnt participate anymore to thermal transfer).Determination of the parametersThe determination of the parameters Uc and Uv is indeed a big question. We have some reliable measured data for free mounted arrays, but there is a severe lack of information when the modules are integrated. What value should be chosen according to the straining duct sizes under the modules, and the length of the air path?One can observe that the heat capacity of the air is very low. Even with large air vents, the flowing air under the modules may quickly attain the equilibrium with the modules temperature at the end of the duct, leading to no heat exchange at all. Therefore for the crown of the array the U value may be the fully insu lated U-value you can have big differences between the regions of the array near the air input, and at the output. The program doesnt take this inhomogeneity of the array temperature into account.On the other hand, the use of the device dependence is very difficult. On one hand the knowing of the wind velocity is extremely rare. On the other hand the meteo wind velocity (taken at 10 meter height) is not representative of the temperature at the array level (there may be a factor of 2 between them). In this respect the Uv value is obviously not the similar for these two definitions of the wind velocity.Default and proposed valuesThe default value is fixed for free-standing arrays, asUc = 29 W/mk, Uv = 0 W/mk / m/sIf you have fully insulated arrays, this should be halvedUc = 15 W/mk, Uv = 0 W/mk / m/sThese values suppose an average wind velocity of around 1.5 m/sec at the collectors level. In very windy regions (larger average wind velocities), you can increase the values but we cann ot say by which amount in a reliable way.NOCT determineSome practicians and most of PV modules catalogues usually specify the NOCT coefficient (Nominal Operating Collector temperature), which is the temperature achieve by the PV modules without back coverage under the standard operating conditions defined asIrradiation = 800 W/m, Tamb=20C, Wind velocity = 1 m/s, Open Circuit.The NOCT factor is related to loss factor U by the thermal balance (from the expression of the top Alpha 800 W/m (1 0) = (Uc + Uv 1m/s) (NOCT 20C).In the definition dialog, the user may define either the U factors or the NOCT. The program like a shot gives the equivalence (using Alpha=0.9 and Effic = 10%, without wind dependence).Ohmic wiring lossesOhmic Loss RatioThe Ohmic Loss ratio is referred to the PV array at standard conditions (1000 W/m, 25C), It is the ratio of the wiring ohmic loss Pwir = Rwir * Isc compared to the nominal power Pnom(array) = Rarray * Isc (SC= short circuit).WhereRarray = Vm p / Imp at Standard Test Conditions (STC)Rwir = global wiring resistance of the full system.This is computed for a given sub-array as the resistance of all strings wires in parallel, in series with the cables from the intermediate connexion box on the roof to the inverter input. The global wiring resistance Rwir is obtained by putting all the sub-array wiring resistances in parallel.Use in the simulationThe Global wiring resistance value finally used during the simulation may be defined here as an Ohmic Loss ratio (the default value is 1.5% at STC) or given explicitly in mOhm.Wire diameter optimization and Wiring ResistanceWire sections are determined by the maximal allowable current and the ohmic resistance. Here the proposed diameters are automatically restrain to the minimum allowable section, according to the European standards for isolated wires mounted in apparent mounting ducts.Now for a given global loss target (at STC, i.e. maximum operating current), the best section cho ice is determined by the program in order to minimiseThe global slovenly person mass,The ohmic losses behave in a quadratic way with the array current (Ploss = R I), so that the ratio diminishes linearly with the output current. Therefore the average wiring losses are more lower during the whole running year.Metal resistivityThe resistivity of wiring metals is strongly dependent on the temperature, which can widely vary due to dissipating currents.For pure metal, one hasCopper Rho = 1.68 E-8 * (1 + 0.0068 * temporary worker C) OhmmDefault value Temp = 50C = 22 mOhmmm/mAluminium Rho = 2.7 E-8 * (1 + 0.0043 * Temp C) Ohmm Default value Temp = 50C = 33 mOhmmm/mWe use copper which have minimum resistivity.Module quality losses / mismatchModule quality lossIt is well-known that most of PV modules series dont match the manufacturer nominal specifications. Up to now, this was one of the greater uncertainties in the PV system performance evaluation.Now, with guaranteed power statements a nd increasing availability of separatist expertise, the situation seems going toward some clarification. Module series are change with a given tolerance, and actual powers usually lie under the nominal specified power, but stay in the tolerance.We decided that the program default was acceptable.Array mismatch lossLosses due to mismatch are related to the fact that the real modules in the array do not strictly present the same I/V characteristics. The graph below helps for visualising the realistic behaviour of such an array, with a random distribution of the characteristics of get about current for each module.This allows for the quantification of power-loss at the maximum power point, as well as of current-loss when working at fixed voltage. (MPP= maximum power point)Array incidence loss (IAM)The incidence effect (the designated term is IAM, for Incidence incline Modifier) corresponds to the weakening of the irradiation really reaching the PV cells surface, with respect to irra diation under normal incidence. In principle, this loss obeys Fresnels Laws, (They describe the behaviour of light when base between media of differing refractive indices. The reflection of light that the equations predict is known as Fresnel reflection), concerning transmission and reflections on the protective layer (the glass), and on the cells surface. In practice, it is often approached using a parameterisation called ASHRAE (as it has become a standard in this American norm), depending on one only parameter boFIAM = 1 bo (1/cos i 1), with i = incidence angle on the plane.For single-glazed thermal solar modules, the usually accepted value for bo is of the order of 0.1. But in a PV module, the lower interface, in contact with the cell, presents a high refraction index and our specific measurements on real crystalline modules actually indicate a value of bo = 0.05.Final Report for Broome for January