Summary Results

The Summary Results provide high-level performance metrics that characterize the overall energy production and efficiency of a photovoltaic power plant. These metrics are calculated from the detailed timestep results and are reported on an annual basis for each prediction year.

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Plane of Array Insolation

Plane of Array (POA) Insolation represents the total solar energy incident on the module surface over the prediction period, normalized by the total module area. This metric quantifies the solar resource available to the PV system after accounting for the array’s orientation and tilt. POA Insolation is calculated by summing the effective global POA irradiance across all timesteps and converting to energy units: $$POA_{insolation} = \frac{\sum_{t} POA_{global,t} \times \Delta t}{A_{module,total}} \times 0.001$$ Where:

• $POA_{global,t}$ is the global plane-of-array irradiance at timestep $t$ (W/m²)
• $\Delta t$ is the timestep interval (hours)
• $A_{module,total}$ is the total module area of the power plant (m²)
• The factor of 0.001 converts from Wh/m² to kWh/m²

Units: kWh/m²

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Specific Yield DC

Specific Yield DC quantifies the energy production of the power plant normalized by its DC nameplate capacity. It represents the equivalent number of hours that the plant would need to operate at its rated DC capacity to produce the same amount of energy. $$SY_{DC} = \frac{E_{net}}{P_{DC,rated}}$$ Where:

• $E_{net}$ is the total net AC energy delivered to the point of interconnection (Wh)
• $P_{DC,rated}$ is the total DC nameplate capacity of the power plant (W)

The DC nameplate capacity is calculated as the sum of all DC field capacities across the plant: $$P_{DC,rated} = \sum_{blocks} N_{b} \times \sum_{arrays} N_{a} \times \sum_{inverters} N_{i} \times \sum_{fields} N_{f} \times P_{field,DC}$$ Where $N_{b}$, $N_{a}$, $N_{i}$, and $N_{f}$ are the repeater counts for blocks, arrays, inverters, and DC fields respectively. Units: kWh/kWp (equivalent to hours)

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Performance Ratio

Performance Ratio (PR) is a dimensionless metric that indicates how effectively the PV system converts the available solar resource into electrical energy. It accounts for all system losses and is independent of the solar resource, making it useful for comparing system performance across different locations and time periods. $$PR = \frac{SY_{DC}}{POA_{insolation}} \times 100$$ Where:

• $SY_{DC}$ is the Specific Yield DC (kWh/kWp)
• $POA_{insolation}$ is the Plane of Array Insolation (kWh/m²)

A Performance Ratio of 100% would indicate that the system converts all incident solar energy to AC output with no losses. Typical values for well-designed systems range from 75% to 85%, with losses attributed to temperature, shading, soiling, inverter efficiency, and other factors documented in the P50 Loss Tree. Units: % (dimensionless ratio expressed as percentage)

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AC Capacity Factor

AC Capacity Factor represents the ratio of actual energy production to the theoretical maximum energy that could be produced if the plant operated continuously at its AC rated capacity. It provides a measure of plant utilization over the prediction period. $$CF_{AC} = \frac{SY_{AC}}{T_{hours}} \times 100$$ Where:

• $SY_{AC}$ is the Specific Yield AC, calculated as $E_{net} / P_{AC,rated}$ (hours)
• $T_{hours}$ is the total number of hours in the prediction period
• $P_{AC,rated}$ is the total AC rated capacity (sum of inverter setpoint capacities)

The total hours is calculated from the number of timesteps and the weather data time interval: $$T_{hours} = N_{timesteps} \times \frac{\Delta t}{60}$$ Where $\Delta t$ is the timestep interval in minutes. Units: %

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Plant Net Energy

Plant Net Energy is the total AC electrical energy delivered to the point of interconnection over the prediction period. This represents the final energy output after all losses, including DC losses, inverter losses, AC collection losses, transformer losses, and any curtailment due to grid limitations. $$E_{net} = \sum_{t} P_{system,t} \times \frac{\Delta t}{60} \times 10^{-9}$$ Where:

• $P_{system,t}$ is the System Power Output at timestep $t$ from System Nodal Data (W)
• $\Delta t$ is the timestep interval (minutes)
• The factor of $10^{-9}$ converts from Wh to GWh

Plant Net Energy includes both positive power generation during daylight hours and negative power consumption during nighttime (for transformer energization and auxiliary loads). Units: GWh

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Plant Gross Energy

Plant Gross Energy is the total AC electrical energy generated by the power plant before any energy consumption or curtailment. It represents the gross generation capability of the system. $$E_{gross} = \sum_{t} \max(P_{generated,t}, 0) \times \frac{\Delta t}{60} \times 10^{-9}$$ Where:

• $P_{generated,t}$ is the Plant Power Generated at timestep $t$ from System Nodal Data (W)
• Only positive generation values are summed (nighttime consumption is excluded)
• $\Delta t$ is the timestep interval (minutes)
• The factor of $10^{-9}$ converts from Wh to GWh

The difference between Plant Gross Energy and Plant Net Energy represents the total energy consumed by the plant (auxiliary loads, transformer energization) plus any curtailment losses. Units: GWh