Site Assessment for Solar Water Heating Systems: Page 2 of 4

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Proper planning is important to maximize system performance.
Ideally, solar thermal collectors should be positioned to get full sun between 9 a.m. and 3 p.m. solar time. Proper planning is important to maximize system performance.
Street-level view
Street-level views can assist with identifying site-specific characteristics, such as roof type and roof slope, and potential shading issues.
Aerial photo
Aerial photos from online maps can also be used to spot potential shading issues. In addition, they can help the assessor determine the building’s orientation.
Solmetric’s free online Roof Azimuth Tool
Solmetric’s free online Roof Azimuth Tool can calculate a roof’s orientation angle with two clicks of a mouse.
Fitting additional solar equipment into an existing utility room
Fitting additional solar equipment into an existing utility room can be a challenge and may affect system design.
replace damaged or old roofing
Since an SWH system is designed to function for at least 20 years, it may be best to replace damaged or old roofing material prior to the system’s installation.
Solmetric’s iPV app
Solmetric’s iPV app offers a sample shade analysis for a site in San Francisco showing a 20% annual loss due to shade.
Solmetric’s iPV app
Solmetric’s iPV app allows users to trace obstructions on-screen to determine the site’s effective skyline.
Solmetric’s SunEye
Solmetric’s SunEye is a digital interface that provides detailed information about a site’s solar access.
Example SunEye Site Data
Solmetric’s SunEye is a digital interface that provides detailed information about a site’s solar access, expressing it as a monthly, biannual, and annual percentage.
The Solar Pathfinder’s Sun Trace Wizard
The Solar Pathfinder’s Sun Trace Wizard allows users to trace the shadows of obstructions from a digital photo, and then calculates monthly solar access.
The Solar Pathfinder solar assessment tool
The Solar Pathfinder solar assessment tool can be used manually (users trace the outline of obstructions reflected on the plastic dome onto the black sun path diagram) or an image can be imported into software for automated calculations.
Proper planning is important to maximize system performance.
Street-level view
Aerial photo
Solmetric’s free online Roof Azimuth Tool
Fitting additional solar equipment into an existing utility room
replace damaged or old roofing
Solmetric’s iPV app
Solmetric’s iPV app
Solmetric’s SunEye
Example SunEye Site Data
The Solar Pathfinder’s Sun Trace Wizard
The Solar Pathfinder solar assessment tool

How will the building’s orientation and architecture impact collector placement? Some buildings are perfectly situated for a roof-mounted collector array. Others may require a wall- or ground-mounted array. These approaches may affect system cost and performance.

How is the water currently heated? Almost all SWH systems are integrated with water heaters powered by electricity, propane, natural gas, or oil. The type of auxiliary heat used with the SWH system will have a significant impact on the type of tank that is appropriate.

How many people live at the home? Since the production of a SWH system is dependent upon household hot water consumption, it is important to gauge whether the household uses enough hot water to justify the expense.

How much money is currently being spent for water heating? Throughout its history, the solar industry has been driven by competing energy costs. If a system has the potential to save its owner a bunch of money, this is a huge benefit. By determining the costs of water heating, a professional can also more precisely estimate the average hot water use for the household.

Some prospective clients have done their homework, identified the system type that best fits their desires, and have a good sense of the system costs. Others might simply be interested in “going green,” becoming more self-sufficient, or reducing their energy costs. In all cases, the professional should visit the site to verify the conditions before proceeding. If any homeowner interested in self-install has doubts, they would be wise to hire a pro to perform an initial assessment.

Powerful online tools are huge assets to the solar professional during this preliminary phase. Aerial maps and satellite photos from common online providers allow remote site observation. The building’s orientation, large trees or other obstructions that might cause shading, and roof space that might be appropriate can be identified. Street-level and isometric views provide greater detail for gathering as much information as is practical before visiting the site.

A site assessor can use these tools to observe barriers for installation. Had I checked remotely on the project mentioned earlier, I would have seen that the neighboring trees were a significant problem and been able to address this issue during the planning process, instead of after arriving on-site.

On-Site Assessment

Key details must be confirmed before selecting equipment and determining the system design. Some of these include:

How will the system be integrated with the existing heating system? The type of heating fuel is critical, as it affects tank selection and controls. If the existing heater is old or inefficient, it may make sense to replace it.

Will the SWH system also provide space heating? A system that provides space heating also increases complexity. Information is needed about the type of distribution (i.e., baseboard, radiant tubing, ducts, etc.), the efficiency of the building envelope, and the configuration of the current heating system.

Where will the equipment be located? The collector location can often be approximated without a site visit. Details such as the location of storage tanks, controls, piping, expansion tanks, and other components often require a site visit.

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