Merge branch 'develop' into mspt_no_finance

NREL · May 2, 2023 · ef9b670 · ef9b670
2 parents 3fa2278 + c2c1d28
commit ef9b670
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Showing 4 changed files with 35 additions and 15 deletions.
diff --git a/ssc/cmod_swh.cpp b/ssc/cmod_swh.cpp
@@ -679,7 +679,8 @@ class cm_swh : public compute_module
 						V_hot = V_hot_prev + ts_sec*mdot_total/rho_water;
 						V_cold = V_tank - V_hot;
 						T_hot = (T_hot_prev*V_hot_prev + ts_sec*(mdot_total/rho_water)*(T_cold_prev + dT_collector))/V_hot;
-						T_cold = (V_tank/V_cold)*T_tank - (V_hot/V_cold)*T_hot;
+                        T_cold = (V_tank/V_cold)*T_tank - (V_hot/V_cold)*T_hot;                                 // weighted average to enforce T_tank based on T_hot
+                        if (T_cold < std::min(T_mains_use, T_room)) T_cold = std::min(T_mains_use, T_room);     // above relation breaks-down at small V_cold causing unphysical T_cold
 						T_top = T_hot;
 						T_bot = T_cold;
 						T_deliv = T_top;
@@ -722,9 +723,11 @@ class cm_swh : public compute_module
 						V_hot = 0;
                     }
 
+                    double T_hot_drained = std::numeric_limits<double>::quiet_NaN();
 					if (V_hot == 0)	// cold water drawn into the bottom of the tank in previous timesteps has completely flushed hot water from the tank
 					{
-						T_hot = T_hot_prev;
+                        double time_to_drain_sec = V_hot_prev * rho_water / mdot_mix;
+                        T_hot_drained = (T_hot_prev * time_to_drain_sec + T_cold * (ts_sec - time_to_drain_sec)) / ts_sec;
 					}
 					else
 					{
@@ -733,7 +736,6 @@ class cm_swh : public compute_module
 						double m_hot = V_hot_prev*rho_water;
 						T_hot = ((T_hot_prev * Cp_water * m_hot) + (ts_sec*U_tank*A_hot * T_room))/((m_hot*Cp_water) + (ts_sec*U_tank*A_hot)); // IMPLICIT NON-STEADY (Euler)
 					}
-					hotLoss = U_tank * A_hot * (T_hot - T_room);
 
 					// Cold node calculations
 					V_cold = V_tank-V_hot;
@@ -749,20 +751,23 @@ class cm_swh : public compute_module
 						T_cold = ((T_cold_prev*m_cold*Cp_water) + (ts_sec*U_tank*A_cold*T_room) + (ts_sec*mdot_mix*Cp_water*T_mains_use))
 							/((m_cold*Cp_water) + (ts_sec*A_cold*U_tank) + (mdot_mix*ts_sec*Cp_water) ); // IMPLICIT NON-STEADY
 					}
-					coldLoss = U_tank*A_cold*(T_cold - T_room);
 
-					Q_tankloss = hotLoss + coldLoss;
-					T_tank = (V_hot / V_tank) * T_hot + (V_cold / V_tank) * T_cold;
-					T_top = T_tank + 0.33*dT_collector;
-					T_bot = T_tank - 0.67*dT_collector;
-					// T_top = T_hot
-					// T_bot = T_cold
                     if (V_hot > 0) {
                         T_deliv = T_hot;
                     }
                     else {
-                        T_deliv = T_cold;
+                        T_deliv = T_hot_drained;
+                        T_hot = T_cold;     // hot water completely flushed from tank
                     }
+					T_tank = (V_hot / V_tank) * T_hot + (V_cold / V_tank) * T_cold;
+					T_top = T_tank + 0.33*dT_collector;
+					T_bot = T_tank - 0.67*dT_collector;
+					// T_top = T_hot
+					// T_bot = T_cold
+
+					hotLoss = U_tank * A_hot * (T_hot - T_room);
+					coldLoss = U_tank*A_cold*(T_cold - T_room);
+					Q_tankloss = hotLoss + coldLoss;
 				}
 
 				// calculate pumping losses (pump size is user entered) -

diff --git a/tcs/csp_solver_mono_eq_methods.cpp b/tcs/csp_solver_mono_eq_methods.cpp
@@ -89,18 +89,26 @@ int C_csp_solver::solve_operating_mode(C_csp_collector_receiver::E_csp_cr_modes
             C_monotonic_eq_solver::S_xy_pair xy2;
             double m_dot_bal2 = std::numeric_limits<double>::quiet_NaN();
             double x1 = xy1.x;
+            size_t iter_count = 0;
             do
             {
-                xy2.x = x1 * (1.0 / (1.0 + m_dot_bal));
+                xy2.x = x1 * (1.0 / (1.0 + std::max(0.02,m_dot_bal)));
 
                 m_dot_bal_code = c_mdot_solver.test_member_function(xy2.x, &m_dot_bal2);
-                if (m_dot_bal_code != 0)
+                if (std::abs(m_dot_bal2 - m_dot_bal) >= 0.02) {
+                    break;
+                }
+
+                iter_count++;
+                // 23-04-18 tn: If defocus is < 10% get out
+                //              If changing defocus isn't changing mass balance, get out (e.g. trough at its minimum flow rate)
+                if (m_dot_bal_code != 0 || xy2.x < 0.1 || (iter_count > 2 && m_dot_bal2 == m_dot_bal) )
                 {
                     reset_time(t_ts_initial);
                     return -2;
                 }
                 x1 = xy2.x;
-            } while (std::abs(m_dot_bal2 - m_dot_bal) < 0.02);
+            } while (true);
 
             xy2.y = m_dot_bal2;
 

diff --git a/tcs/htf_props.cpp b/tcs/htf_props.cpp
@@ -123,6 +123,13 @@ void HTFProperties::set_temp_enth_lookup()
     double T_low = this->min_temp();
     double T_high = this->max_temp();
 
+    if (!std::isfinite(T_low)) {
+        T_low = 270.0 + 273.15;
+    }
+    if (!std::isfinite(T_high)) {
+        T_high = 720.0 + 273.15;
+    }
+
 	double delta_T_target = 1.0;
 
 	int n_rows = (int)(ceil((T_high - T_low)/delta_T_target) + 1.0);

diff --git a/test/ssc_test/cmod_swh_test.cpp b/test/ssc_test/cmod_swh_test.cpp
@@ -43,7 +43,7 @@ TEST_F(CM_SWH, ResidentialDefault_cmod_swh) {
 
     ssc_number_t annual_energy;
     ssc_data_get_number(data, "annual_energy", &annual_energy);
-    EXPECT_NEAR(annual_energy, 2362.2, 0.1); 
+    EXPECT_NEAR(annual_energy, 2362.5, 0.1); 
 
 }