diff --git a/Utilities/Optimisation.py b/Utilities/Optimisation.py
index e33742b..bf6842b 100644
--- a/Utilities/Optimisation.py
+++ b/Utilities/Optimisation.py
@@ -18,16 +18,18 @@ def optimise_vertical_panel_pitch(c):
         """
         c["array"]["spacing"] = pitch
         logging.info(f"Optimizing with pitch: {pitch}m")
-        vertical_energy = calculate_energy_production_vertical(c)
+        vertical_energy, _ = calculate_energy_production_vertical(c)
         total_energy_yield = vertical_energy.sum()
         logger.info(f"Total energy yield for pitch {pitch}m: {total_energy_yield}kWh")
         return -total_energy_yield
 
     # perform minimization
     initial_pitch = c["array"]["spacing"]
-    result = minimize(objective, initial_pitch, bounds=[(0, 90)])
+    result = minimize(
+        objective, initial_pitch, bounds=[(0, 5)], tol=1e-8, options={"eps": 0.5}
+    )
     optimal_pitch = result.x[0]
     c["array"]["spacing"] = optimal_pitch
     logger.info(f"Optimal pitch found: {optimal_pitch}m")
-    vetical_energy = calculate_energy_production_vertical(c)
-    return (optimal_pitch, vetical_energy)
+    vetical_energy, no_of_panels = calculate_energy_production_vertical(c)
+    return (optimal_pitch, vetical_energy, no_of_panels)
diff --git a/Utilities/Shading.py b/Utilities/Shading.py
index 735891a..2a2088d 100644
--- a/Utilities/Shading.py
+++ b/Utilities/Shading.py
@@ -132,11 +132,6 @@ def calculate_energy_production_vertical(c):
     panel_coordinates, no_of_panels = define_grid_layout(c, panel_tilt=90)
     solar_positions, clearsky_data = get_solar_data(c)
 
-    # split the solar positions data into morning and afternoon, using solar azimuth of
-    # 180 degrees as the threshold
-    morning_solar_positions = solar_positions[solar_positions["azimuth"] <= 180]
-    afternoon_solar_positions = solar_positions[solar_positions["azimuth"] > 180]
-
     # the first row is always not shaded so exclude
     no_of_rows = np.unique(panel_coordinates["y"]).shape[0]
     no_of_shaded_rows = no_of_rows - 1
@@ -207,31 +202,31 @@ def calculate_energy_production_vertical(c):
     # drop rows with poa_global NaN values
     poa_rear = poa_rear.dropna(subset=["poa_global"])
 
-    effective_front = (
-        poa_front["poa_global"]
-        * (1 - morning_shaded_fraction)
-        * c["panel"]["efficiency"]
-    )
+    effective_front = poa_front["poa_global"] * (1 - morning_shaded_fraction)
     effective_rear = (
         poa_rear["poa_global"]
         * (1 - afternoon_shaded_fraction)
         * c["panel"]["bifaciality"]
-        * c["panel"]["efficiency"]
     )
 
-    energy_front = effective_front * 15 / 60 / 1e3
-    energy_rear = effective_rear * 15 / 60 / 1e3
-    total_hourly_energy_m2 = energy_front + energy_rear
-    energy_total = total_hourly_energy_m2.sum()
-    logger.info(f"Energy yield calculated: {energy_total} kWh/m2")
+    total_hourly_irradiance = effective_front + effective_rear
+    system_size = c["panel"]["peak_power"] * no_of_panels
+    pdc0 = system_size
+    gamma_pdc = c["panel"]["temperature_coefficient"]
+    temp_cell = c["panel"]["nominal_operating_cell_temperature"]
+    pdc = pvlib.pvsystem.pvwatts_dc(
+        pdc0=pdc0,
+        gamma_pdc=gamma_pdc,
+        temp_cell=temp_cell,
+        g_poa_effective=total_hourly_irradiance,
+    )
+
+    total_hourly_energy = pdc * 15 / 60 / 1e3  # convert to kWh
 
-    panel_area = c["panel"]["dimensions"]["length"] * c["panel"]["dimensions"]["width"]
-    total_area = panel_area * no_of_panels
-    total_hourly_energy = total_hourly_energy_m2 * total_area
     total_energy = total_hourly_energy.sum()
     logger.info(f"Total energy yield calculated: {total_energy} kWh")
 
-    return total_hourly_energy
+    return total_hourly_energy, no_of_panels
 
 
 def calculate_energy_production_horizontal(c):
@@ -263,7 +258,6 @@ def calculate_energy_production_horizontal(c):
         axis_tilt=axis_tilt,
     )
     shaded_fraction = shaded_fraction * no_of_shaded_rows / no_of_rows
-    logger.info(f"Shaded fraction calculated for solar positions: {shaded_fraction}")
 
     poa = pvlib.irradiance.get_total_irradiance(
         surface_tilt=0,
@@ -277,18 +271,22 @@ def calculate_energy_production_horizontal(c):
     )
     poa = poa.dropna(subset=["poa_global"])
 
-    effective_front = (
-        poa["poa_global"] * (1 - shaded_fraction) * c["panel"]["efficiency"]
+    effective_front = poa["poa_global"] * (1 - shaded_fraction)
+
+    system_size = c["panel"]["peak_power"] * no_of_panels
+
+    pdc0 = system_size
+    gamma_pdc = c["panel"]["temperature_coefficient"]
+    temp_cell = c["panel"]["nominal_operating_cell_temperature"]
+    pdc = pvlib.pvsystem.pvwatts_dc(
+        pdc0=pdc0,
+        gamma_pdc=gamma_pdc,
+        temp_cell=temp_cell,
+        g_poa_effective=effective_front,
     )
 
-    total_hourly_energy_m2 = effective_front * 15 / 60 / 1e3
-    energy_total = total_hourly_energy_m2.sum()
-    logger.info(f"Energy yield calculated: {energy_total} kWh/m2")
-
-    panel_area = c["panel"]["dimensions"]["length"] * c["panel"]["dimensions"]["width"]
-    total_area = panel_area * no_of_panels
-    total_hourly_energy = total_hourly_energy_m2 * total_area
+    total_hourly_energy = pdc * 15 / 60 / 1e3  # convert to kWh
     total_energy = total_hourly_energy.sum()
     logger.info(f"Total energy yield calculated: {total_energy} kWh")
 
-    return total_hourly_energy
+    return total_hourly_energy, no_of_panels
diff --git a/config.yml b/config.yml
index 479bc82..ade5837 100644
--- a/config.yml
+++ b/config.yml
@@ -1,6 +1,6 @@
 array:
   system_size: 900 # in kWp
-  spacing: 1 # spacing between adjacent panel rows in m
+  spacing: 21.8 # spacing between adjacent panel rows in m
   edge_setback: 1.8 # distance from the edge of the roof to the array
   roof_slope: 0
   slope: 0 # degrees from horizontal (+ve means shaded row is higher than the row in front)
@@ -30,3 +30,6 @@ panel:
     length: 2.384
     width: 1.303
     thickness: 0.033
+  temperature_coefficient: -0.0029 # /°C
+  nominal_operating_cell_temperature: 43 # °C
+
diff --git a/main.py b/main.py
index 610a860..1309ab9 100644
--- a/main.py
+++ b/main.py
@@ -3,7 +3,10 @@ import yaml
 import logging
 import numpy as np
 import matplotlib.pyplot as pl
-from Utilities.Shading import calculate_energy_production_horizontal
+from Utilities.Shading import (
+    calculate_energy_production_horizontal,
+    calculate_energy_production_vertical,
+)
 from Utilities.Optimisation import optimise_vertical_panel_pitch
 
 logging.basicConfig(
@@ -27,15 +30,17 @@ with open(config_path, "r") as file:
 logger.info("Configuration loaded successfully.")
 logger.debug(f"Configuration: {c}")
 
+
 # calculate energy production for horizontal and vertical panels
-optimal_pitch, vertical_energy = optimise_vertical_panel_pitch(c)
+optimal_pitch, vertical_energy, no_of_panels_vertical = optimise_vertical_panel_pitch(c)
 logger.info("Energy production for vertical panels calculated successfully.")
 logger.debug(f"Vertical Energy Production: {vertical_energy.sum()}")
+logger.debug("Number of panels: %d", no_of_panels_vertical)
 
-horizontal_energy = calculate_energy_production_horizontal(c)
+horizontal_energy, no_of_panels_horizontal = calculate_energy_production_horizontal(c)
 logger.info("Energy production for horizontal panels calculated successfully.")
 logger.debug(f"Horizontal Energy Production: {horizontal_energy.sum()}")
-
+logger.debug("Number of panels: %d", no_of_panels_horizontal)
 
 NOVA_scaledown = 0.75