PV fix angle = latitude. Problem

Hi all:

When migrating from previous version (Jun2011) to the last one (Dec2011), a PV model, I realized that for locations in the south hemisphere, the energy output is drastically reduced. i figured out that when activating the option tilt angle = latitude, the tilt produced is not facing the module towards the sun, but the oposite. So this option is not helping the PV installation as it did in the previous version, but is giving a worst performance.
Just a "+/-" problem.

Juan Peña

Dear Juan,

Thank you for letting us know about this issue. Until we resolve it, when using either the PV Component or PVWatts option to model PV systems in the Southern hemisphere, please set the tilt angle manually rather than using the "Force Tilt = Latitude" option on the Array page.

Note that if you are using PVWatts to model a system in the Southern hemisphere, you should also change the azimuth angle to 0 degrees (facing north) from the default value of 180 degrees (facing south). For the PV Component model (and the CSP and solar water heating models), an azimuth angle of 0 degrees represents an array (or collector) facing the equator in both the Northern and Southern hemispheres.

Best regards,
Paul.

For southern hemisphere weather files in SAM 2011.12.2:

For the PV component model, on the Array page, enter array tilt values as negative values.

For PVWatts, enter southern-hemisphere array tilt values on the PVWatts Solar Array page as positive values.

In PVWatts, the "force tilt = latitude" option does not work correctly.

For example, for a PV system in Melbourne, Australia at latitude 38 degrees South with an array tilted at latitude:

- For the PV component model, either enter a tilt value of -38, or check Force Tilt = Latitude

- For PVWatts, enter a tilt value of 38. Do not use Force Tilt = Latitude.

Please note that in SAM 2011.6.30, the force tilt=latitude option does not work for the PV component model, but does work for the PVWatts model (the reverse is true for SAM 2011.12.2)

Best regards,
Paul.