Improve invalid zenith angle handling in Sandia PV model

src/EnergyPlus/ElectricPowerServiceManager.cc

@@ -1924,7 +1924,9 @@ namespace EnergyPlus {
 		electricityProd( 0.0 ),
 		electProdRate( 0.0 ),
 		thermalProd( 0.0 ),
-		thermProdRate( 0.0 )
+		thermProdRate( 0.0 ),
+		errCountNegElectProd_( 0 ),
+		errCountNegThermProd_( 0 )
 	{
 
 		std::string const routineName = "GeneratorController constructor ";
@@ -2068,6 +2070,18 @@ namespace EnergyPlus {
 			break;
 		}
 		} // end switch
+
+		//check if generator production has gone wrong and is negative, reset to zero and warn
+		if ( electricPowerOutput < 0.0 ) {
+			if ( errCountNegElectProd_ == 0 ) {
+				ShowWarningMessage( typeOfName + " named " + name  + " is producing negative electric power, check generator inputs." );
+				ShowContinueError( "Electric power production rate =" + General::RoundSigDigits( electricPowerOutput, 4 ) );
+				ShowContinueError( "The power will be set to zero, and the simulation continues... " );
+			}
+			ShowRecurringWarningErrorAtEnd( typeOfName + " named " + name  + " is producing negative electric power ", errCountNegElectProd_,electricPowerOutput, electricPowerOutput );
+			electricPowerOutput = 0.0;
+		}
+
 	}
 
 	DCtoACInverter::DCtoACInverter(

src/EnergyPlus/ElectricPowerServiceManager.hh

@@ -595,6 +595,13 @@ public: // data // might make this class a friend of ElectPowerLoadCenter?
 	Real64 electProdRate; // Current AC Electric Production Rate from Equipment (W)
 	Real64 thermalProd; // Current Thermal energy Produced from Equipment (J)
 	Real64 thermProdRate; // Current Thermal energy Production Rate from Equipment (W)
+
+private:
+
+	int errCountNegElectProd_; // error count for reccuring error when generators produce negative electric power
+	int errCountNegThermProd_; // error count for reccuring error when generators produce negative thermal power
+
+
 }; //class GeneratorController
 
 class ElectPowerLoadCenter

src/EnergyPlus/Photovoltaics.cc

@@ -2145,8 +2145,8 @@ namespace Photovoltaics {
 			Real64 const AM( 1.0 / ( std::cos( SolZen * DegToRadians ) + 0.5057 * std::pow( 96.08 - SolZen, -1.634 ) ) );
 			AbsoluteAirMass = std::exp( -0.0001184 * Altitude ) * AM;
 		} else {
-			AbsoluteAirMass = 999.0;
-			// should maybe add a show warning msg.
+			Real64 const AM( 36.32 ); // evaluated above at SolZen = 89.9 issue #5528
+			AbsoluteAirMass = std::exp( -0.0001184 * Altitude ) * AM;
 		}
 
 		return AbsoluteAirMass;

tst/EnergyPlus/unit/CMakeLists.txt

@@ -73,6 +73,7 @@ set( test_src
   OutputReportData.unit.cc
   OutputReportTabular.unit.cc
   OutputReportTabularAnnual.unit.cc
+  Photovoltaics.unit.cc
   PierceSurface.unit.cc
   ReportSizingManager.unit.cc
   RoomAirflowNetwork.unit.cc

tst/EnergyPlus/unit/Photovoltaics.unit.cc

@@ -0,0 +1,87 @@
+// EnergyPlus, Copyright (c) 1996-2016, The Board of Trustees of the University of Illinois and
+// The Regents of the University of California, through Lawrence Berkeley National Laboratory
+// (subject to receipt of any required approvals from the U.S. Dept. of Energy). All rights
+// reserved.
+//
+// If you have questions about your rights to use or distribute this software, please contact
+// Berkeley Lab's Innovation & Partnerships Office at IPO@lbl.gov.
+//
+// NOTICE: This Software was developed under funding from the U.S. Department of Energy and the
+// U.S. Government consequently retains certain rights. As such, the U.S. Government has been
+// granted for itself and others acting on its behalf a paid-up, nonexclusive, irrevocable,
+// worldwide license in the Software to reproduce, distribute copies to the public, prepare
+// derivative works, and perform publicly and display publicly, and to permit others to do so.
+//
+// Redistribution and use in source and binary forms, with or without modification, are permitted
+// provided that the following conditions are met:
+//
+// (1) Redistributions of source code must retain the above copyright notice, this list of
+//     conditions and the following disclaimer.
+//
+// (2) Redistributions in binary form must reproduce the above copyright notice, this list of
+//     conditions and the following disclaimer in the documentation and/or other materials
+//     provided with the distribution.
+//
+// (3) Neither the name of the University of California, Lawrence Berkeley National Laboratory,
+//     the University of Illinois, U.S. Dept. of Energy nor the names of its contributors may be
+//     used to endorse or promote products derived from this software without specific prior
+//     written permission.
+//
+// (4) Use of EnergyPlus(TM) Name. If Licensee (i) distributes the software in stand-alone form
+//     without changes from the version obtained under this License, or (ii) Licensee makes a
+//     reference solely to the software portion of its product, Licensee must refer to the
+//     software as "EnergyPlus version X" software, where "X" is the version number Licensee
+//     obtained under this License and may not use a different name for the software. Except as
+//     specifically required in this Section (4), Licensee shall not use in a company name, a
+//     product name, in advertising, publicity, or other promotional activities any name, trade
+//     name, trademark, logo, or other designation of "EnergyPlus", "E+", "e+" or confusingly
+//     similar designation, without Lawrence Berkeley National Laboratory's prior written consent.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND ANY EXPRESS OR
+// IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY
+// AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR
+// CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
+// CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
+// SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR
+// OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+// POSSIBILITY OF SUCH DAMAGE.
+//
+// You are under no obligation whatsoever to provide any bug fixes, patches, or upgrades to the
+// features, functionality or performance of the source code ("Enhancements") to anyone; however,
+// if you choose to make your Enhancements available either publicly, or directly to Lawrence
+// Berkeley National Laboratory, without imposing a separate written license agreement for such
+// Enhancements, then you hereby grant the following license: a non-exclusive, royalty-free
+// perpetual license to install, use, modify, prepare derivative works, incorporate into other
+// computer software, distribute, and sublicense such enhancements or derivative works thereof,
+// in binary and source code form.
+
+// EnergyPlus::ElectricPowerServiceManager Unit Tests
+
+// Google Test Headers
+#include <gtest/gtest.h>
+
+// EnergyPlus Headers
+#include <Photovoltaics.hh>
+
+#include "Fixtures/EnergyPlusFixture.hh"
+
+using namespace EnergyPlus;
+
+TEST_F( EnergyPlusFixture, PV_Sandia_AirMassAtHighZenith )
+{
+	// unit test for issue #5528, test behavior of function AbsoluteAirMass at zenith angle above 89.9 degrees.
+
+	// first check above the degree threshold, compare to side calc
+	Real64 zenithAngleDeg = 90.0;
+	Real64 altitude  = 1;
+	Real64 airMass = Photovoltaics::AbsoluteAirMass( zenithAngleDeg, altitude );
+	EXPECT_NE( airMass, 999 ); // would have been true before fix
+	EXPECT_NEAR( airMass, 36.31531 , 0.1 );
+
+	// now check below the threshold, compare to side calc spreadhsheet result
+	zenithAngleDeg = 89.0;
+	airMass = Photovoltaics::AbsoluteAirMass( zenithAngleDeg, altitude );
+	EXPECT_NEAR( airMass, 26.24135, 0.1 );
+
+}