Generation¶
Solar Electric¶
Home Energy Score allows for a single photovoltaic system to be included per
dwelling unit. For multi-family units and single-family attached units a shared
PV system can be specified along with the number of units sharing that system
and the proportion of the PV system allocated to that unit will be considered.
In HPXML, multiple PVSystem elements can be specified to represent the PV
systems on the house. The translator combines multiple systems and generates the
appropriate HEScore inputs as follows:
Number of Units Sharing System¶
If the Building Dwelling Unit Type is single_family_attached or
apartment_unit the HPXML element NumberofUnitsServed can be provided to
indicate a shared PV system. If that is provided the total capacity of the PV
system will be divided by the number of units as described below. If this is
omitted or the building is not one of those dwelling unit types, the entire PV
system will be assumed to serve a single unit.
Capacity Known¶
If each PVSystem has a MaxPowerOutput, this is true. If each
PVSystem has a NumberOfPanels or if each has CollectorArea, this is
false. Preference is given to known capacity if available. One of
MaxPowerOutput, NumberOfPanels, or CollectorArea must be specified
for each PVSystem.
DC Capacity¶
If each PVSystem has a MaxPowerOutput, the system capacity is known. The
system_capacity in HEScore is calculated by summing all the
MaxPowerOutput elements in HPXML.
If PVSystem is a shared system (i.e., serving multiple dwelling units), PV
generation will be apportioned to the dwelling unit by dividing the building’s
total PV capacity by the number of units.
Number of Panels¶
If MaxPowerOutput is missing from any PVSystem, the translator will
check to see if every system has NumberOfPanels and calculate the total
number of panels.
If NumberOfPanels isn’t available on every system, the translator will look
for CollectorArea on every PVSystem. The number of panels is calculated by
summing all the collector area, dividing by 17.6 sq.ft., and rounding to the
nearest whole number.
If PVSystem is a shared system (i.e., serving multiple dwelling units), the
number of panels will be apportioned to the dwelling unit by dividing the
building’s total number of panels by the number of units.
Weighted Averages¶
The below quantities are calculated using weighted averages. The weights used are in priority order:
MaxPowerOutputNumberOfPanelsCollectorArea
Which is the same data elements used to determine the PV sizing inputs above.
Year Installed¶
For each PVSystem the YearInverterManufactured and
YearModulesManufactured element values are retrieved, and the greater of the
two is assumed to be the year that system was installed. When there are multiple
PVSystem elements, a weighted average is calculated and used.
Panel Orientation (Azimuth)¶
For each PVSystem the ArrayAzimuth (degrees clockwise from north) is
retrieved. If ArrayAzimuth is not available, ArrayOrientation (north,
northwest, etc) is converted into an azimuth. A weighted average azimuth is
calculated and converted into the nearest cardinal direction (north, northwest,
etc) for submission into the array_azimuth HEScore input (which expects a
direction, not a numeric azimuth).
Panel Tilt¶
For each PVSystem the ArrayTilt (in degrees from horizontal) is
retrieved. A weighted average tilt is calculated and submitted to the
array_tilt HEScore input (which expects an enumeration, not a numeric tilt).
The tilt is mapped to HEScore as follows:
HPXML |
HEScore |
|---|---|
0 - 7° |
flat |
8 - 22° |
low_slope |
23 - 37° |
medium_slope |
38 - 90° |
steep_slope |