Any scientific analysis is only as accurate as the least accurate input. Gross errors in structure orientation, solar system sizing, collector placement, component specification, and scientific studies can result when designers/engineers fail to accurately assess shading patterns at proposed building/ecological sites.

By combining the site-specific shading data of the Solar Pathfinder™ with the published solar radiation figures (by NREL for USA), an accurate solar site analysis can be made. This insolation data, on an hourly and monthly basis can then be applied to architectural, engineering, solar, and ecological applications.

The Solar Pathfinder™ is non-electronic. Simple and straight-forward in its engineering, it requires no special skills or technical know-how. One simple tracing does the job and becomes the permanent record for the solar data. When properly cared for, the unit will give the user years of accurate site analysis.

The Solar Pathfinder™ uses a highly polished, transparent, convex plastic dome to give a panoramic view of the entire site. All the trees, buildings or other obstacles to the sun are plainly visible as reflections on the surface of the dome. The sunpath diagram can be seen through the transparent dome at the same time. This diagram is latitude specific [the further away from the equator, the lower the sun will be in the sky, thereby making the sunpath further from the center of the unit] and shows the sun’s average path for each month. The rays of the diagram depict solar time. The diagram itself is therefore calibrated to give solar insolation data for all the hours of the day and all the days of the year. The diagram is also specific to the application: “South-facing” (for Northern hemisphere) or “vertical” is for applications of 20-90 degrees tilt – usually solar; “Horizontal” is for applications of 0-20 degrees tilt – usually ecological (For the flexibility of calculating radiation of any azimuth and any tilt angle, use our Solar Pathfinder Assistant software in addition to the Solar Pathfinder).

Because the Solar Pathfinder™ works on a reflective principle rather than actually showing shadows, it can be used anytime of the day, anytime of the year, in either cloudy or clear weather. The actual position of the sun at the time of the solar site analysis is irrelevant. In fact, the unit is easier to use in the absence of direct sunlight. It could even be used on a moonlit night.

The Pathfinder has an integral bubble level and magnetic compass to facilitate quick instrument set-up. The unit and diagrams are engineered to adjust for magnetic declination to face “true south” (for Northern hemisphere), not “magnetic south”. A locking mechanism secures the adjustment.

Once the Solar Pathfinder™ has been properly set up, the user traces the outline of the horizon’s reflection seen on the dome onto the underlying diagram by inserting a white marking pen (included) through the slots on the side of the unit. The traced line shows exactly at what hours of the day and months of the year an obstacle will shade that particular location. The picture below shows a Solar Pathfinder™ being used at a typical solar site. Notice how the reflected image of the tree-line is sighted coincidentally with the diagram below it. The diagram, also pictured, is a site tracing of the same site. The tracing becomes a permanent record of the solar data.


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The small numbers across the arcs represent the percentage of solar insolation in half-hour segments throughout the day – each month’s arc totaling 100%. The sum of the unshaded numbers along a particular monthly sunpath represent the percent of the total available solar energy for an average day during that month, as compared to a completely unobstructed site.

To translate the Site Percent value obtained as above to kWh/m2/day, take the solar radiation data based on unobstructed site (as collected by the NREL for the USA – this data is included with the unit) for the desired tilt and tracking mechanism (i.e. fixed, 1-axis, 2-axis, etc.) and multiply it by the daily Site Percent. For example:

Ecological studies can use this same NREL insolation data by using the “fixed tilt” chart at 0 degrees (horizontal) tilt and using the same math.

Solar Insolation Data, such as the NREL data, takes into account the specific climate of the city chosen. Local cloud cover, smog, dust in the atmosphere, etc. are averaged in its insolation values. Such data would be the only information needed if the site was completely free of shade-producing objects such as trees, building, etc. For specific sun/shade analysis of a given site, the Solar Pathfinder™ is an invaluable tool that is both fast and accurate.

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