Description

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The Description of the SAC Canopy AC Array

Not many people know that we actually have two PV arrays here on campus. The second
one, called an AC array, is rated at 4.3 kW (much smaller than the Aquatic Center rooftop array [342 kW]) and is installed top of a
canopy covering the sidewalk leading up to the Calloway Student Athletic Complex (SAC).
You can see the AC array in the photo below, which was actually taken from the roof of the
Aquatic Center. The square roof at bottom center is on top of the entryway to SAC; just
above it, you can see the curved canopy covered by blue-colored solar modules. The photo
here was taken just before the 1996 Olympics. The fences in front of SAC were part of
Olympic security.

This next photo shows the canopy from ground level. This system was designed by Solar Design Associates of Harvard, MA. It
consists of 18 240W Solarex multicrystalline Si
modules.

On the back of each module is a power conditioning system (PCS) made by Advanced Energy
Systems Inc. in Wilton, NH. These module-integrated PCS (MIPs) can be seen in the photo
below. The smaller boxes with the rounded corners and the two conduits coming out of it
are the junction boxes in which electrical connection to the PV modules are made. The
junction boxes also house the bypass diodes (8 diodes, one for every 18 solar cells). Next
to each junction box is a MIP. There are two MIPs visible in this picture. The one on the
right, the slightly larger and squarer (and darker) one, is an older version. A newer
version is seen on the left. This newer version incorporated some improvements which were
field-tested in this array. We have recently installed the latest version of the AES MIPs
(the "MicroInverters").

The above photo also shows that the modules in our AC array have a clear backskin; the
moisture-proof sheet that covers the back sides of the solar cells in the module is
transparent. In this way, light can get through between the solar cells, and the
interconnections between the solar cells can be seen. Also the PV modules themselves are
the "roof" of this canopy. Not only do they provide electricity, but they also
provide shade and shelter. In this way, this system is also an example of how integrating
PV into building structures increases its value and makes PV more economically attractive.

The electricity from our AC array currently is being fed directly into the main service
entrance of the Calloway Student Athletic Complex (SAC), but it might later be used for
something specific, such as charging an electric vehicle, batteries for lighting, or some
other application. Our modeling predicts that we can expect just over 5 MWh of energy
production from this array each year.

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