Determine renewable generation objectives

Many projects are designed to include renewable generation systems (such as solar photovoltaic panels), or are designed to be "solar ready" which means that they are constructed "in a way that facilitates and optimizes the installation of a rooftop solar photovoltaic (PV) system at some point after the building has been constructed." As a BEM practitioner, you can assist the design team by evaluating the site, and estimating renewable generation potential.

Solar PV systems

Solar panels are most effective when the sun's rays hit their surface perpendicularly. In the northern hemisphere, this means solar panels should face south and, in the southern hemisphere, they should face north. The panels should also be tilted at an angle approximately equal to the geographical latitude.

Evaluate site

Review the project's site conditions to see whether any surrounding trees, structures, or other site features may cast shadows on areas of the site, and for which hours of the day throughout the year. Areas that receive significant hours of shading are not ideal for placing solar panels. For new construction projects, consider siting the building in a manner where the building itself doesn't cast shadows on areas of the site where solar panels may be placed.

Evaluate roof

Similar to the site evaluation, also determine which areas of the roof receive adequate sunlight. Be mindful that the entire roof area is unlikely to be available for placing PV panels because there is likely to be mechanical equipment, access hatches, skylights, and other features that require adequate area and access.

Another consideration for existing buildings is the age of the roof. If the roof is aging and will need replacement within a few years, it may make sense to replace the roof before installing solar.

Estimate generation potential

Many tools exist to estimate energy generation potential based on the project's location, available area for PV, orientation, and tilt. See the additional resources section below for some commonly used tools.

Additional Resources

• NREL PVWatts Calculator - Estimates the energy production and cost of energy of grid-connected photovoltaic (PV) energy systems throughout the world. It allows homeowners, small building owners, installers and manufacturers to easily develop estimates of the performance of potential PV installations.
• NREL System Advisor Model (SAM) - Estimates performance and cost of energy for grid-connected renewable energy systems. In addition to solar systems, the SAM tool also models battery storage, wind power generation, geothermal, and several other technologies.

Links to external websites are provided as a convenience for further research, but do not imply any endorsement of the content or the operator of the external site, as detailed in BEMcyclopedia's general disclaimers.