SOLAR TODAY - November/December 2010

ask ases | american solar energy society experts answer your questions.

PV Design software: where can I find It?

I am trying to locate a good solar photovoltaic (PV) design software package for my install business. There are plenty on Google search, but [I’m] not sure ven where to start. Thought you could help or lead me in the right direction.

— Steve Schanne, Woodbury, N.J.

— SCOT T SkLAR,
president of the
Stella Group (thestella
groupltd.com), a solar
consulting firm in
Washington, D.C.

Joseph McCabe, chair of the American Solar Energy Society (ASES) Solar Electric Division, offers these suggestions: •;PV-DesignPro at mauisolarsoft-ware.com.

•;PVsyst ( pvsyst.com/5.2/index. php) is a software package for the study, sizing, simulation and data analysis of complete PV systems.

• Precigeo ( precigeo.com) uses aerial imagery and computer-aided design to provide shading evaluations, individual module selection with custom placements along with fire setback overlays.

PV-DesignPro

— JOSEPH MCCAbE, chair of the American Solar Energy Society (ASES) Solar Electricity Division

Scott Sklar, president of the Stella Group (thestella groupltd.com), a solar consulting firm in Washington, D.C., likes: •;3Tier’s website ( 3tier.com) to gauge the solar resource.

•;NREL’s;PVWATTS ( nrel.gov/rredc/pvwatts/).

•;Sandia National Laboratory’s guide ( photovoltaics.sandia.gov/ docs/Design_and_Installation_ of_PV_Systems.htm).

•;In My Back yard, a solar and wind tool ( nrel.gov/eis/imby/ about.html).

For more sophisticated energy-
modeling software, useful for
architectural and engineering
firms, the popular programs
include —
•;Homer ( homerenergy.com/software.html) and
•;Energy 10 ( nrel.gov/buildings/energy10.html).

Sklar also recommends — • The Solar Design Tool ( solardesigntool.com/user. html?action=create) and • Sustainable by Design ( susdesign.com/tools.php). Find a useful directory listing dozens of software packages at bit.ly/d9zHTS.

Portable PV system: Is It worth the money?

Alocal store sells a small, 60-watt solar system for $312, with inverter — you just need to add a battery. Is it worth it? — Terry Trefz, Cardington, Ohio

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That’s about $5.20 per watt, more or less competitive with other photovoltaic (PV) systems on the market. “Small photovoltaic systems do make sense for remote and portable use,” says Scott Sklar. “The 60-watt panel with inverter and a battery could be useful in charging portable tools, cellular phones and video games, for running the fluorescent or CFL lights in a shed or garage, or for camping, where it could inflate tires, provide light and run a radio.”

Joseph McCabe says, “Typically, smaller solar electric systems are more expensive per watt than larger systems — check on computer-portability and camping-supply websites to see if this price is fair. Do consider how fragile the panels are; often times, amorphous silicon on float glass will break more easily than crystalline silicon on tempered glass. Do be sure to include a charge controller to interact with the battery charging from the solar panels. Direct-current charge controllers can be cost-effective, even for smaller systems, optimizing the power harvest from the panels and protecting the battery for longer life.” ST