Onsite Generation Help

Modified on Fri, 15 Jan 2021 at 12:10 PM

Solar Generation

Ekotrope uses the National Renewable Energy Laboratory’s (NREL) PVWatts model to calculate annual production from Solar Photovoltaic (PV) systems. The inputs below match those required for PVWatts.

Track Mode	This solar array’s mode of tracking sunlight. If the solar array does not track sunlight, track mode “Fixed” must be selected.
Nameplate Capacity	The full-load output of this solar array, in units kWdc, as published by the manufacturer.
Derate Factor	DC to AC derate factor of the PV system [0-1]. Ekotrope uses PVWatts to estimate solar production. System Losses are described in Chapter 11 of the PVWatts Manual and Ekotrope provides this calculator for Derate Factor. The default value is 0.77.
Orientation	The cardinal direction of the solar PV array, measured in degrees clockwise from north. 0 is North, 90 is East, 180 is South, and 270 is West. Clicking “Rotate 45 Deg.” or “Find Worst Orientation” at the bottom of the page will have no effect on solar orientation.
Tilt	The pitch of the solar panel, measured in degrees from the horizontal. At 0 degrees, the solar panel is perfectly horizontal-facing. At 90 degrees, the solar panel is perfectly vertical-facing.

In buildings with multiple Dwelling Units, the Solar Generation should be pro-rated for each Dwelling Unit based on the number of bedrooms. For example, for a building with a 1 bedroom and 2 bedroom unit and a 15 kW solar array, 5 kW should be assigned to the 1 bedroom unit and 10 kW assigned to the 2 bedroom unit.

NOTE: if a reliable annual kWh production number can be gathered from another source, like a professional PV system design report, the system could be modeled using the Onsite Generation section rather than the Solar Generation section.

Onsite Generation

This section allows entering both solar and wind generation systems. Click the Other Onsite Generation? checkbox to add Onsite Generation components.

Onsite Generation components use types from the Component Library similar to other components like walls and windows.

When using this section, users must specify the estimated annual production of the onsite generation system. This information should come from a reliable source, like a system design report from a professional designer.

Note that for Onsite Generation, Ekotrope will not model the true hourly distribution of the electric production and will instead assume a flat-line distribution throughout the entire year. This will not impact the HERS Index or code compliance, but could impact energy bill predictions if variable time of use energy rates are used.