Measuring Solar Access with the Solmetric SunEye

Assessing solar access is a critical step in designing installations of solar water heating panels and photovoltaic (PV) modules, and in siting passive solar buildings. Until recently, we’ve had only manual tools to support that assessment, most notably the industry standard Solar Pathfinder (www.solarpathfinder.com). With Solar Pathfinder, a user looks down at a transparent, plastic, fisheye globe (mounted on a tripod and leveled) that allows the user to see through and trace the reflected horizon or any solar obstructions on latitude-specific template papers placed under the globe.

Now, Solmetric Corporation has digitalized this process with its SunEye—a sophisticated, easy-to-use tool for measuring solar shading and calculating monthly and annual solar access. The SunEye includes a built-in digital camera with a fisheye lens. A user holds the SunEye or mounts it on a tripod, keeping it level using a built-in bubble-level and orienting it to the south using the built-in compass, then clicks to take a photo. The heart of the system is a Hewlett-Packard iPAQ processor that captures and computes the digital image data.

A straightforward interface allows the user to calculate the percentage of solar access, graphically showing the obstructions by time of day and month, and to simulate removal of the solar obstructions by erasing those areas on the digital image—to show the effect of cutting down a tree, for example. Digital files can be processed in the field or uploaded to a Windows computer (Macintosh interface not yet available) for review and printing.

SunEye users expressed enthusiasm to

EBN. “We’re really happy with it,” said Jeremy Smithson of Puget Sound Solar in Seattle. Smithson has been using the SunEye since October 2006 and told

EBN that it cuts about an hour from a typical site investigation. With an average of four site assessments per week, the SunEye’s $1,355 price was not a problem. “For me, it paid for itself pretty quickly,” Smithson said. He installed over 60 PV and solar hot water systems last year and expects to put in 80–100 this year.

Richard O’Connell, of O’Connell Solar Company in Rohnert Park, California, purchased the very first production model SunEye in August 2006 as soon as he heard about it. He’d been using the Solar Pathfinder for six years and had wondered when someone would come up with a digital version that was easier to use. “It’s an invaluable tool for solar installers and designers here in California,” he said, because of the specific calculations that are required for participation in the California Solar Initiative (see

EBN

Vol. 15, No. 2). “The SunEye takes the guess work out of those calculations and provides a hard copy of the actual site survey,” he told

EBN. Also, California law protects solar access (preventing someone from building a shed or planting a tree that will block access), and he thinks the SunEye “will undoubtedly stand up in a court of law should that be an issue in the future.” Like Smithson, he had no problem with the cost. “I didn’t think twice about purchasing this unit,” he said.

Jonathan Cohen of Imagine Energy, a solar design, engineering, and installation firm in Wilsonville, Oregon, called the SunEye “a great sales tool to show potential customers the effect of shading elements in full color.” It doesn’t hurt that the product looks cool during site visits! None of the users

EBN spoke with have had any problems with the SunEye, and they spoke highly of Solmetric. The company has also provided regular software upgrades at no cost. “The support staff is great,” said Cohen.

The SunEye was invented by Solmetric president Willard MacDonald, an electrical engineer who worked previously as a senior design engineer for the test and measurement company Agilent Technologies (a Hewlett-Packard spin-off), where he helped to develop precision electronic measurement devices. In addition to the SunEye’s performance features, the manufacturing is remarkably green. It makes extensive use of recycled materials and components, including the unit’s main processor, according to director of marketing Daniel Weinreb, who demonstrated the product for EBN staff. To date, the young company has sold about 150 units, with interest growing quickly.

– Alex Wilson

For more information:

Solmetric Corporation

Bolinas, California

877-263-5026

info@solmetric.comwww.solmetric.com