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) |
Building projects may incorporate on-site electricity generation equipment, such as photovoltaics (PV) and wind turbines or combined heat and power or fuel cells that make electricity and produce heat. These systems may be modeled in various ways. Descriptors have been added below for PV, combined heat and power cogeneration and wind turbines. Fuel cells are not addressed by this manual currently. In all cases, the baseline building will be modeled without heat recovery from on-site generation equipment. If there is no thermal link between the power generation equipment and building equipment (such as heat recovery from combined heat and power [CHP]), on-site power generation can be modeled in a separate process; otherwise, it needs to be linked to the building simulation.
On-site renewable energy shall be subtracted from the proposed design energy consumption prior to calculating the proposed building performance, additional details are provided in Section 1.3. On-site renewable energy generated by systems included on the building permit that is used by the building is considered free and shall not be included in the proposed design energy cost for renewable energy contributions up to 5% of the baseline building performance. When renewable energy contribution of the on-site renewable energy generation system exceeds 5% of the BBP, the PCI will be calculated as explain in Section 1.3 of this manual.
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 |