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<p class="MsoNormal"><span lang="EN-GB">Dear all,<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-GB"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-GB">I want to simulate the PV yield and I am using Type94a (see attachement).<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-GB">I have some knowledge on the 4-parameter PV model, I have two major questions or remarks:
<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-GB"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-GB">I am using TRNSYS 17.01.xx<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-GB"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-GB">############# FIRST #########################:<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-GB">I am not entirely clear but I think, that Type94a when operated with
<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-GB">ParameterValue(16) (tau-alpha)>0, that is without the IAM-correction,<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-GB">e.g. tau-alpha=0.9, does not consider tau-alpha for the calculation of the light-current I_L.<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-GB"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-GB">The annual yield is not sensitive wrt tau-alpha ():<o:p></o:p></span></p>
<p class="MsoListParagraph" style="text-indent:-18.0pt;mso-list:l0 level1 lfo1"><![if !supportLists]><span lang="EN-GB"><span style="mso-list:Ignore">-<span style="font:7.0pt "Times New Roman"">
</span></span></span><![endif]><span lang="EN-GB">Run the attached project (Project_Type94a_noWeatherFile.tpf) (tau-alpha=0.9) and record the value for Wpv_kWh7m2 in the online plotter at the end of the year (my result 675.8 kWh/m2)<o:p></o:p></span></p>
<p class="MsoListParagraph" style="text-indent:-18.0pt;mso-list:l0 level1 lfo1"><![if !supportLists]><span lang="EN-GB"><span style="mso-list:Ignore">-<span style="font:7.0pt "Times New Roman"">
</span></span></span><![endif]><span lang="EN-GB">change tau-alpha to 0.5 and repeat the last line (my result 686.4 kWh/m2), the result is higher which is not really physical with nearly half the radiation from before (reason: the cell-temperature is smaller
– see below, and not tau_alpha correction for the light current)<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-GB"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-GB">You may repeat these steps for a project (Project_Type94a_.tpf) with real weather data<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-GB">my results for tau-alpha=0.9 : 232.2 kWh/m2<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-GB">my results for tau-alpha=0.5 : 226.7 kWh/m2 (the difference is too small)<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-GB"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-GB">I cite the relevant source code lines (see attachment) in the following.<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-GB">Lets assume tau-alpha=0.9; <o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-GB"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-GB">Line 240: tamax = DABS(getParameterValue(16)) !
</span><span style="font-family:Wingdings">à</span><span lang="EN-GB"> tamax=0.9 represents the optical efficiency factor<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-GB">Line 245: If (getParameterValue(16) < 0) Then<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-GB">Line 248: incangmod = 0 ! incangmod = 0 since getParameterValue(16) > 0<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-GB">Line 249: tau_al = tamax ! tau_al is set constant
<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-GB">Line 393: sun = getInputValue(1)/3.6d0 ! read the total radiation on the PV-array<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-GB">Line 498: tc = ta + (sun*(tcnoct-tanoct)/sunnoct*(1.-effref/tau_al)) ! tau_al is used for the calculation of the cell temperature
<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-GB">Line 501: il = (sun/sunr)*(ilr+misc*nprl*(tc-tcr)) ! for the calc. of the light current tau_al is not used; that is, it seems there is no optical efficiency considered<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-GB"><o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-GB">Am I missing sth here, or do I use an old source code file (please see attachement)?<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-GB">As I understand in this case without IAM-correction there is an error in the source-code.<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-GB"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-GB">############# SECOND #########################:<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-GB">Lets assume tau-alpha=-0.9; </span><span lang="EN-GB" style="font-family:Wingdings">à</span><span lang="EN-GB"> incangmod = 1<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-GB"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-GB">I don’t understand where type94a gets a value assigned for sungnd?<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-GB">Where does the sungnd come from, I mean Type94a has no parameter relating to the ground reflectance.<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-GB">Line 497: sungnd = sungnd*tagnd<o:p></o:p></span></p>
<p class="MsoNormal" style="text-indent:35.4pt"><span lang="EN-GB"> sundir = sundir*tadir<o:p></o:p></span></p>
<p class="MsoNormal" style="text-indent:35.4pt"><span lang="EN-GB"> tau_al =(sundiff+sungnd+sundir)/sun<o:p></o:p></span></p>
<p class="MsoNormal" style="text-indent:35.4pt"><span lang="EN-GB"> sun = sundiff+sungnd+sundir<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-GB"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-GB"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-GB">Thank you for any responses.<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-GB">best regards<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-GB"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-GB">MArtin<o:p></o:p></span></p>
<p class="MsoNormal">_______________________________________________________________<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal"> Mag. Ing. <span lang="EN-GB">Martin Felix Pichler<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-GB"> Institut fuer Waermetechnik / Institute of Thermal Engineering<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-GB"> TU Graz / Graz University of Technology<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-GB"> Inffeldgasse 25B, A-8010 Graz<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-GB"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-GB"> Tel.: +43 316 873 7312<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-GB"> Fax : +43 316 873 7305<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-GB"> </span><a href="http://www.iwt.tugraz.at/"><span lang="EN-GB" style="color:blue">http://www.iwt.tugraz.at/</span></a><span lang="EN-GB"><o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-GB"> </span>_______________________________________________________________<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
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