Candidate buildings may have photovoltaic (PV) systems and the energy generated by these systems may offset the power used by HVAC, lighting, and other building systems. Since most PV systems work under a net metering arrangement whereby the utility grid is used as a storage battery, accepting excess energy when it is available and providing power back to the building at night and other times when the PV system is not generating, the simulation of PV systems need to be on an hourly time step so that it can be aligned with the building loads and the utility rate structure.
This section describes one set of building descriptors for specifying a PV system. This set of building descriptors is based on the five-parameter model.1 Other models may be used for PV systems. The inputs apply only to the proposed design, as the baseline building is modeled without a PV system.
Configuration
This set of building descriptors addresses the overall layout and design of the PV system, including the orientation and slope of the collectors, how they are wired together, and how they are linked to an inverter that converts DC power to AC and synchronizes it with the grid.
|
PV System Name |
|
|---|---|
|
Applicability |
All PV systems |
|
Definition |
A unique identifier that can be used to reference the PV system and associate it with the construction documents |
|
Units |
Text, unique |
|
Input Restrictions |
The name should provide a link to the construction documents. |
|
Baseline Rules |
None (PV not modeled for the baseline building) |
|
Number of Modules in a String |
|
|---|---|
|
Applicability |
All PV systems |
|
Definition |
This is the number of modules in a series string. Modules in series increase voltage which is often needed in order to match output voltage with the inverter requirements; modules in parallel increase current. |
|
Units |
Numeric: integer |
|
Input Restrictions |
As designed |
|
Baseline Rules |
None (PV not modeled for the baseline building) |
|
Number of Strings |
|
|---|---|
|
Applicability |
All PV systems |
|
Definition |
This is the number of strings of modules in parallel. Modules in series increase voltage; modules in parallel increase current. |
|
Units |
Numeric: integer |
|
Input Restrictions |
As designed |
|
Baseline Rules |
None (PV not modeled for the baseline building) |
|
Collector Area |
|
|---|---|
|
Applicability |
All PV systems |
|
Definition |
The area of the collector module. |
|
Units |
Square feet (ft²) |
|
Input Restrictions |
From manufacturer's specification |
|
Baseline Rules |
None (PV not modeled for the baseline building) |
|
Slope |
|
|---|---|
|
Applicability |
All PV systems |
|
Definition |
The slope of the collector modules relative to the horizontal. |
|
Units |
Degrees (°) |
|
Input Restrictions |
As designed |
|
Baseline Rules |
None (PV not modeled for the baseline building) |
|
Azimuth |
|
|---|---|
|
Applicability |
All PV systems |
|
Definition |
The orientation of the collector modules relative to due North. An azimuth of 180° faces due south; 90° faces east, etc. |
|
Units |
Degrees (°) |
|
Input Restrictions |
As designed |
|
Baseline Rules |
None (PV not modeled for the baseline building) |
|
PV Mounting Height |
|
|---|---|
|
Applicability |
All PV systems |
|
Definition |
The height of the collectors above the ground. |
|
Units |
Feet (ft) |
|
Input Restrictions |
As designed. |
|
Baseline Rules |
None (PV not modeled for the baseline building) |
Shading
Shading of PV systems results in significant reduction of production and must be accounted for in an acceptable manner. A method is implied in the following building descriptors that is consistent with the NSHP Calculator2 . With this method, the area around the solar system is divided into 22.5° cones and the height and distance to shading objects is entered for each quadrant. Other methods may be used, including use of the building shade inputs (see building site characteristics under project data)
|
Shading Azimuth |
|
|---|---|
|
Applicability |
All PV systems |
|
Definition |
A quadrant where the height and distance of shading objects is specified. |
|
Units |
List: ENE, E, ESE, SE, SSE, S, SSW, SW, WSW, W, WNW |
|
Input Restrictions |
As estimated from existing surrounding buildings and shading structures |
|
Baseline Rules |
None (PV not modeled for the baseline building) |
|
Shading Object Height |
|
|---|---|
|
Applicability |
All PV systems |
|
Definition |
The height of the building or shading object in the 22.5° cone |
|
Units |
Feet (ft) |
|
Input Restrictions |
As estimated from existing surrounding buildings and shading structures |
|
Baseline Rules |
None (PV not modeled for the baseline building) |
|
Shading Object Distance |
|
|---|---|
|
Applicability |
All PV systems |
|
Definition |
The horizontal distance from the shading object to the collectors |
|
Units |
Feet (ft) |
|
Input Restrictions |
As estimated from existing surrounding buildings and shading structures |
|
Baseline Rules |
None (PV not modeled for the baseline building) |
Collector Performance
The collector performance can be characterized by the following five variables that are available from PV array manufacturers: the open-circuit voltage, the short-circuit current, the voltage and current at the maximum power-point, and the temperature coefficient of the open-circuit voltage. These are described below.
|
Short-circuit Current |
|
|---|---|
|
Applicability |
All PV systems |
|
Definition |
Isc - current measured with zero voltage |
|
Units |
Amps |
|
Input Restrictions |
From manufacturer's specification |
|
Baseline Rules |
None (PV not modeled for the baseline building) |
|
Open-circuit Voltage |
|
|---|---|
|
Applicability |
All PV systems |
|
Definition |
Voc - voltage measured with an open circuit |
|
Units |
Volts |
|
Input Restrictions |
From manufacturer's specification |
|
Baseline Rules |
None (PV not modeled for the baseline building) |
|
Maximum Power-Point Voltage and Current |
|
|---|---|
|
Applicability |
All PV systems |
|
Definition |
Imp, Vmp - current and voltage at the maximum power-point condition. These parameters are typically reported at Standard Test Conditions of 1000 W/m2 and a cell temperature of 25°C. |
|
Units |
Amps and Volts |
|
Input Restrictions |
From manufacturer's specification |
|
Baseline Rules |
None (PV not modeled for the baseline building) |
|
Open-circuit Temperature Coefficient |
|
|---|---|
|
Applicability |
All PV systems |
|
Definition |
Voc - temperature coefficient at open-circuit voltage |
|
Units |
I/C |
|
Input Restrictions |
From manufacturer's specification |
|
Baseline Rules |
None (PV not modeled for the baseline building) |
|
Short-circuit Temperature Coefficient |
|
|---|---|
|
Applicability |
All PV systems |
|
Definition |
Voc - temperature coefficient at short-circuit current. This is supplied the manufacturer. |
|
Units |
V/C |
|
Input Restrictions |
From manufacturer's specification |
|
Baseline Rules |
None (PV not modeled for the baseline building) |
|
Normal Operating Cell Temperature (NOCT) |
|
|---|---|
|
Applicability |
All PV systems |
|
Definition |
The normal operating cell temperature, typically between 45°C and 55°C |
|
Units |
Degrees Celsius (°C) |
|
Input Restrictions |
From manufacturer's specification |
|
Baseline Rules |
None (PV not modeled for the baseline building) |
Candidate buildings may have photovoltaic (PV) systems and the energy generated by these systems may offset the power used by HVAC, lighting, and other building systems. Since most PV systems work under a net metering arrangement whereby the utility grid is used as a storage battery, accepting excess energy when it is available and providing power back to the building at night and other times when the PV system is not generating, the simulation of PV systems need to be on an hourly time step so that it can be aligned with the building loads and the utility rate structure.
This section describes one set of building descriptors for specifying a PV system. This set of building descriptors is based on the five-parameter model (De Soto et al. 2006). Other models may be used for PV systems. The inputs apply only to the proposed design, as the baseline building is modeled without a PV system.
3.10.1.1 Configuration
This set of building descriptors addresses the overall layout and design of the PV system, including the orientation and slope of the collectors, how they are wired together, and how they are linked to an inverter that converts DC power to AC and synchronizes it with the grid.
| PV System Name | |
|---|---|
| Applicability | All PV systems |
| Definition | A unique identifier that can be used to reference the PV system and associate it with the construction documents |
| Units | Text, Unique |
| Input Restrictions | As designed |
| Baseline Building | None (PV not modeled for the baseline building) |
| Number of Modules in a String | |
|---|---|
| Applicability | All PV systems |
| Definition | This is the number of modules in a series string. Modules in series increase voltage which is often needed in order to match output voltage with the inverter requirements; modules in parallel increase current. |
| Units | Numeric: Integer |
| Input Restrictions | As designed |
| Baseline Building | None (PV not modeled for the baseline building) |
| Number of Strings | |
|---|---|
| Applicability | All PV systems |
| Definition | This is the number of strings of modules in parallel. Modules in series increase voltage; modules in parallel increase current. |
| Units | Numeric: Integer |
| Input Restrictions | As designed |
| Baseline Building | None (PV not modeled for the baseline building) |
| Collector Area | |
|---|---|
| Applicability | All PV systems |
| Definition | The area of the collector module |
| Units | Square feet (ft2) |
| Input Restrictions | As designed |
| Baseline Building | None (PV not modeled for the baseline building) |
| Azimuth | |
|---|---|
| Applicability | All PV systems |
| Definition |
The azimuth angle is the angle clockwise from true north describing the direction that the array faces. An azimuth angle of 180° is for a south-facing array, and an azimuth angle of 0° is for a north-facing array. For an array with one-axis tracking, the azimuth angle is the angle clockwise from true north of the axis of rotation. The azimuth angle does not apply to arrays with two-axis tracking. The default value is an azimuth angle of 180° (south-facing) for locations in the northern hemisphere and 0° (north-facing) for locations in the southern hemisphere. These values typically maximize electricity production over the year, although local weather patterns may cause the optimal azimuth angle to be slightly more or less than the default values. |
| Units | Degrees (°) |
| Input Restrictions | As designed |
| Baseline Building | None (PV not modeled for the baseline building) |
| PV Mounting Height | |
|---|---|
| Applicability | All PV systems |
| Definition |
The height of the collectors above the ground |
| Units | Feet (ft) |
| Input Restrictions | As designed |
| Baseline Building | None (PV not modeled for the baseline building) |
| PV Array Mounting Type | |
|---|---|
| Applicability | All PV systems |
| Definition |
The array type describes whether the PV modules in the array are fixed, or whether they move to track the movement of the sun across the sky with one or two axes of rotation. |
| Units | List: Fixed, one axis tracking, two axis tracking. |
| Input Restrictions | As designed. The default value is a fixed, or no tracking. |
| Baseline Building | None (PV not modeled for the baseline building) |
3.10.1.2 Shading
Shading of PV systems results in significant reduction of production and must be accounted for in an acceptable manner. A method is implied in the following building descriptors that is consistent with the NSHP Calculator.9 With this method, the area around the solar system is divided into 22.5° cones and the height and distance to shading objects is entered for each quadrant. Other methods may be used, including use of the building shade inputs (see building site characteristics under project data)
| Shading Azimuth | |
|---|---|
| Applicability | All PV systems |
| Definition |
A quadrant where the height and distance of shading objects is specified |
| Units | List: ENE, E, ESE, SE, SSE, S, SSW, SW, WSW, W, WNW |
| Input Restrictions | As estimated from existing surrounding buildings and shading structures |
| Baseline Building | None (PV not modeled for the baseline building) |
| Shading Object Height | |
|---|---|
| Applicability | All PV systems |
| Definition |
The height of the building or shading object in the 22.5° cone |
| Units | Feet (ft) |
| Input Restrictions | As estimated from existing surrounding buildings and shading structures |
| Baseline Building | None (PV not modeled for the baseline building) |
| Shading Object Distance | |
|---|---|
| Applicability | All PV systems |
| Definition |
The horizontal distance from the shading object to the collectors |
| Units | Feet (ft) |
| Input Restrictions | As estimated from existing surrounding buildings and shading structures |
| Baseline Building | None (PV not modeled for the baseline building) |
3.10.1.3 Collector Performance
The collector performance can be characterized by the following five variables that are available from PV array manufacturers: the open-circuit voltage, the short-circuit current, the voltage and current at the maximum power-point, and the temperature coefficient of the open-circuit voltage. These are described below.
| Short Circuit Current | |
|---|---|
| Applicability | All PV systems |
| Definition |
Isc - current measured with zero voltage |
| Units | Amps |
| Input Restrictions | From manufacturer's specification |
| Baseline Building | None (PV not modeled for the baseline building) |
| Open-Circuit Voltage | |
|---|---|
| Applicability | All PV systems |
| Definition |
Voc - voltage measured with an open circuit |
| Units | Volts |
| Input Restrictions | From manufacturer's specification |
| Baseline Building | None (PV not modeled for the baseline building) |
| Maximum Power-Point Voltage and Current | |
|---|---|
| Applicability | All PV systems |
| Definition |
Imp, Vmp - current and voltage at the maximum power-point condition. These parameters are typically reported at Standard Test Conditions of 1000 W/m2 and a cell temperature of 25°C. |
| Units | Amps and Volts |
| Input Restrictions | From manufacturer's specification |
| Baseline Building | None (PV not modeled for the baseline building) |
| Open-Circuit Temperature Coefficient | |
|---|---|
| Applicability | All PV systems |
| Definition |
Temperature coefficient of the open circuit voltage (Voc) measures the changing open circuit voltage values of the PV module when the temperature increases (or decreases) |
| Units | %/ºC |
| Input Restrictions | From manufacturer's specification |
| Baseline Building | None (PV not modeled for the baseline building) |
| Short Circuit Temperature Coefficient | |
|---|---|
| Applicability | All PV systems |
| Definition |
Temperature coefficient of the short-circuit current (Isc) measures the changing short-circuit current values of the PV module when the solar cell temperature increases (or decreases) |
| Units | %/ºC |
| Input Restrictions | From manufacturer's specification |
| Baseline Building | None (PV not modeled for the baseline building) |
| Nominal Operating Cell Temperature (NOCT) | |
|---|---|
| Applicability | All PV systems |
| Definition |
The normal operating cell temperature, typically between 45°C and 55°C |
| Units | Degrees Celsius (°C) |
| Input Restrictions | From manufacturer's specification |
| Baseline Building | None (PV not modeled for the baseline building) |
| PV Array Mounting Type | |
|---|---|
| Applicability | All PV systems |
| Definition |
The array type describes whether the PV modules in the array are fixed, or whether they move to track the movement of the sun across the sky with one or two axes of rotation. |
| Units | List: Fixed, one axis tracking, two axis tracking |
| Input Restrictions | As designed. The default value is a fixed, or no tracking. |
| Baseline Building | None (PV not modeled for the baseline building) |
Candidate buildings may have photovoltaic (PV) systems and the energy generated by these systems may offset the power used by HVAC, lighting, and other building systems. Since most PV systems work under a net metering arrangement whereby the utility grid is used as a storage battery, accepting excess energy when it is available and providing power back to the building at night and other times when the PV system is not generating, the simulation of PV systems need to be on an hourly time step so that it can be aligned with the building loads and the utility rate structure.
This section describes one set of building descriptors for specifying a PV system. This set of building descriptors is based on the five-parameter model1 . Other models may be used for PV systems. The inputs apply only to the proposed design, as the baseline building is modeled without a PV system.
Configuration
This set of building descriptors addresses the overall layout and design of the PV system, including the orientation and slope of the collectors, how they are wired together, and how they are linked to an inverter that converts DC power to AC and synchronizes it with the grid.
| PV System Name | |
| Applicability | All PV systems |
|---|---|
| Definition | A unique identifier that can be used to reference the PV system and associate it with the construction documents |
| Units | Text, unique |
| Input Restrictions | The name should provide a link to the construction documents. |
| Number of Modules in a String | |
| Applicability | All PV systems |
|---|---|
| Definition | This is the number of modules in a series string. Modules in series increase voltage which is often needed in order to match output voltage with the inverter requirements; modules in parallel increase current. |
| Units | Numeric: integer |
| Input Restrictions | As designed |
| Number of Strings | |
| Applicability | All PV systems |
|---|---|
| Definition | This is the number of strings of modules in parallel. Modules in series increase voltage; modules in parallel increase current. |
| Units | Numeric: integer |
| Input Restrictions | As designed |
| Collector Area | |
| Applicability | All PV systems |
|---|---|
| Definition | The area of the collector module. |
| Units | Square feet (ft²) |
| Input Restrictions | From manufacturer's specification |
| Slope | |
| Applicability | All PV systems |
|---|---|
| Definition | The slope of the collector modules relative to the horizontal. |
| Units | Degrees (°) |
| Input Restrictions | As designed |
| Azimuth | |
| Applicability | All PV systems |
|---|---|
| Definition | The orientation of the collector modules relative to due North. An azimuth of 180° faces due south; 90° faces east, etc. |
| Units | Degrees (°) |
| Input Restrictions | As designed |
| PV Mounting Height | |
| Applicability | All PV systems |
|---|---|
| Definition | The height of the collectors above the ground. |
| Units | Feet (ft) |
| Input Restrictions | As designed. |
Shading
Shading of PV systems results in significant reduction of production and must be accounted for in an acceptable manner. A method is implied in the following building descriptors that is consistent with the NSHP Calculator2 . With this method, the area around the solar system is divided into 22.5° cones and the height and distance to shading objects is entered for each quadrant. Other methods may be used, including use of the building shade inputs (see building site characteristics under project data)
| Shading Azimuth | |
| Applicability | All PV systems |
|---|---|
| Definition | A quadrant where the height and distance of shading objects is specified. |
| Units | List: ENE, E, ESE, SE, SSE, S, SSW, SW, WSW, W, WNW |
| Input Restrictions | As estimated from existing surrounding buildings and shading structures |
| Shading Object Height | |
| Applicability | All PV systems |
|---|---|
| Definition | The height of the building or shading object in the 22.5° cone |
| Units | Feet (ft) |
| Input Restrictions | As estimated from existing surrounding buildings and shading structures |
| Shading Object Distance | |
| Applicability | All PV systems |
|---|---|
| Definition | The horizontal distance from the shading object to the collectors |
| Units | Feet (ft) |
| Input Restrictions | As estimated from existing surrounding buildings and shading structures |
Collector Performance
The collector performance can be characterized by the following five variables that are available from PV array manufacturers: the open-circuit voltage, the short-circuit current, the voltage and current at the maximum power-point, and the temperature coefficient of the open-circuit voltage. These are described below.
| Short-circuit Current | |
| Applicability | All PV systems |
|---|---|
| Definition | Isc - current measured with zero voltage |
| Units | Amps |
| Input Restrictions | From manufacturer's specification |
| Open-circuit Voltage | |
| Applicability | All PV systems |
|---|---|
| Definition | Voc - voltage measured with an open circuit |
| Units | Volts |
| Input Restrictions | From manufacturer's specification |
| Maximum Power-Point Voltage and Current | |
| Applicability | All PV systems |
|---|---|
| Definition | Imp, Vmp - current and voltage at the maximum power-point condition. These parameters are typically reported at Standard Test Conditions of 1000 W/m2 and a cell temperature of 25°C. |
| Units | Amps and Volts |
| Input Restrictions | From manufacturer's specification |
| Open-circuit Temperature Coefficient | |
| Applicability | All PV systems |
|---|---|
| Definition | Voc - temperature coefficient at open-circuit voltage |
| Units | I/C |
| Input Restrictions | From manufacturer's specification |
| Short-circuit Temperature Coefficient | |
| Applicability | All PV systems |
|---|---|
| Definition | Voc - temperature coefficient at short-circuit current. This is supplied the manufacturer. |
| Units | V/C |
| Input Restrictions | From manufacturer's specification |
| Normal Operating Cell Temperature (NOCT) | |
| Applicability | All PV systems |
|---|---|
| Definition | The normal operating cell temperature, typically between 45°C and 55°C |
| Units | Degrees Celsius (°C) |
| Input Restrictions | From manufacturer's specification |
Candidate buildings may have photovoltaic (PV) systems and the energy generated by these systems may offset the power used by HVAC, lighting, and other building systems. Since most PV systems work under a net metering arrangement whereby the utility grid is used as a storage battery, accepting excess energy when it is available and providing power back to the building at night and other times when the PV system is not generating, the simulation of PV systems need to be on an hourly time step so that it can be aligned with the building loads and the utility rate structure.
This section describes one set of building descriptors for specifying a PV system. This set of building descriptors is based on the five-parameter model1 . Other models may be used for PV systems. The inputs apply only to the proposed design, as the baseline building is modeled without a PV system.
Configuration
This set of building descriptors addresses the overall layout and design of the PV system, including the orientation and slope of the collectors, how they are wired together, and how they are linked to an inverter that converts DC power to AC and synchronizes it with the grid.
| PV System Name | |
| Applicability | All PV systems |
|---|---|
| Definition | A unique identifier that can be used to reference the PV system and associate it with the construction documents |
| Units | Text, unique |
| Input Restrictions | The name should provide a link to the construction documents. |
| Number of Modules in a String | |
| Applicability | All PV systems |
|---|---|
| Definition | This is the number of modules in a series string. Modules in series increase voltage which is often needed in order to match output voltage with the inverter requirements; modules in parallel increase current. |
| Units | Numeric: integer |
| Input Restrictions | As designed |
| Number of Strings | |
| Applicability | All PV systems |
|---|---|
| Definition | This is the number of strings of modules in parallel. Modules in series increase voltage; modules in parallel increase current. |
| Units | Numeric: integer |
| Input Restrictions | As designed |
| Collector Area | |
| Applicability | All PV systems |
|---|---|
| Definition | The area of the collector module. |
| Units | Square feet (ft²) |
| Input Restrictions | From manufacturer's specification |
| Slope | |
| Applicability | All PV systems |
|---|---|
| Definition | The slope of the collector modules relative to the horizontal. |
| Units | Degrees (°) |
| Input Restrictions | As designed |
| Azimuth | |
| Applicability | All PV systems |
|---|---|
| Definition | The orientation of the collector modules relative to due North. An azimuth of 180° faces due south; 90° faces east, etc. |
| Units | Degrees (°) |
| Input Restrictions | As designed |
| PV Mounting Height | |
| Applicability | All PV systems |
|---|---|
| Definition | The height of the collectors above the ground. |
| Units | Feet (ft) |
| Input Restrictions | As designed. |
Shading
Shading of PV systems results in significant reduction of production and must be accounted for in an acceptable manner. A method is implied in the following building descriptors that is consistent with the NSHP Calculator2 . With this method, the area around the solar system is divided into 22.5° cones and the height and distance to shading objects is entered for each quadrant. Other methods may be used, including use of the building shade inputs (see building site characteristics under project data)
| Shading Azimuth | |
| Applicability | All PV systems |
|---|---|
| Definition | A quadrant where the height and distance of shading objects is specified. |
| Units | List: ENE, E, ESE, SE, SSE, S, SSW, SW, WSW, W, WNW |
| Input Restrictions | As estimated from existing surrounding buildings and shading structures |
| Shading Object Height | |
| Applicability | All PV systems |
|---|---|
| Definition | The height of the building or shading object in the 22.5° cone |
| Units | Feet (ft) |
| Input Restrictions | As estimated from existing surrounding buildings and shading structures |
| Shading Object Distance | |
| Applicability | All PV systems |
|---|---|
| Definition | The horizontal distance from the shading object to the collectors |
| Units | Feet (ft) |
| Input Restrictions | As estimated from existing surrounding buildings and shading structures |
Collector Performance
The collector performance can be characterized by the following five variables that are available from PV array manufacturers: the open-circuit voltage, the short-circuit current, the voltage and current at the maximum power-point, and the temperature coefficient of the open-circuit voltage. These are described below.
| Short-circuit Current | |
| Applicability | All PV systems |
|---|---|
| Definition | Isc - current measured with zero voltage |
| Units | Amps |
| Input Restrictions | From manufacturer's specification |
| Open-circuit Voltage | |
| Applicability | All PV systems |
|---|---|
| Definition | Voc - voltage measured with an open circuit |
| Units | Volts |
| Input Restrictions | From manufacturer's specification |
| Maximum Power-Point Voltage and Current | |
| Applicability | All PV systems |
|---|---|
| Definition | Imp, Vmp - current and voltage at the maximum power-point condition. These parameters are typically reported at Standard Test Conditions of 1000 W/m2 and a cell temperature of 25°C. |
| Units | Amps and Volts |
| Input Restrictions | From manufacturer's specification |
| Open-circuit Temperature Coefficient | |
| Applicability | All PV systems |
|---|---|
| Definition | Voc - temperature coefficient at open-circuit voltage |
| Units | I/C |
| Input Restrictions | From manufacturer's specification |
| Short-circuit Temperature Coefficient | |
| Applicability | All PV systems |
|---|---|
| Definition | Voc - temperature coefficient at short-circuit current. This is supplied the manufacturer. |
| Units | V/C |
| Input Restrictions | From manufacturer's specification |
| Normal Operating Cell Temperature (NOCT) | |
| Applicability | All PV systems |
|---|---|
| Definition | The normal operating cell temperature, typically between 45°C and 55°C |
| Units | Degrees Celsius (°C) |
| Input Restrictions | From manufacturer's specification |