NABCEP Solar Site and Shading Analysis 5

Question 1

A site assessment reveals that a proposed rooftop array will have a solar access value of 82% annually. According to NABCEP guidelines, how should this value be used in client communications?

Accepted Answer

Use it to calculate a derated energy production estimate, clearly communicating that shading will reduce output by 18% compared to an unshaded system

Answer

Solar access of 82% means 18% of potential solar energy is blocked by shading; this factor should be applied to the unshaded energy estimate to give the client an accurate production projection.

Question 2

Which of the following site conditions would most benefit from using microinverters or DC power optimizers compared to a standard string inverter configuration?

Accepted Answer

A complex roofline with modules on multiple orientations and partial shading from a chimney

Answer

Microinverters and DC optimizers provide module-level MPPT, which is most beneficial when modules experience unequal shading or different orientations that would otherwise cause severe mismatch losses in a string.

Question 3

When using the Solmetric SunEye for shading analysis, the device is placed at the array plane and photographs the sky. The resulting 'TOF' (Table of Obstructions) reports shading by:

Accepted Answer

Monthly and annual solar access percentages accounting for both beam and diffuse shading

Answer

The SunEye TOF report provides monthly and annual solar access percentages that factor in both direct beam shading from obstructions and the reduction in diffuse sky radiation from blocked sky dome portions.

Question 4

A NABCEP-certified designer finds that the proposed array location has only 68% annual solar access due to mature trees. According to best practices, what should the designer do FIRST before recommending system downsizing?

Accepted Answer

Evaluate whether tree trimming, removal, or alternative mounting locations could improve solar access above an acceptable threshold

Answer

Before accepting poor solar access, the designer should explore mitigation options such as selective tree trimming, removal, or relocating the array to an area with better solar access.

Question 5

In solar resource data analysis, the term 'P90' production estimate means:

Accepted Answer

There is a 90% probability that actual annual production will meet or exceed this energy estimate

Answer

P90 is a financial risk metric meaning there is a 90% probability (high confidence) that the system will produce at least this much energy annually, accounting for weather variability and uncertainty in the resource data.

(NABCEP) Certified North American Board of Certified Energy Practitioners Specialist Practice Test

(NABCEP) Certified North American Board of Certified Energy Practitioners Specialist Practice Test

NABCEP Solar Site and Shading Analysis 5