Site evaluation process overview

The environmental conditions, power needs of users, the type of structure and the budget vary for each off-grid PV project. A site evaluation is the process of gathering information, photographs, and drawings of the location for the proposed project to understand whether a PV system is best way to provide power and if a project will be feasible. The site evaluation begins with the initial conversation that is had about the system and will continue until the design is completed. It is ideal to make the process as efficient and simple as possible to avoid lost time and unnecessary expense, but as a potential project progresses a visit to the physical location is necessary for all but the simplest projects. A visit to the location and an evaluation through the eyes of someone that understands PV systems can provide vital information to inform the design that is often not possible to obtain any other way. The site evaluation process can be divided into four main phases:

• Load evaluation: The gathering of information about the current power needs (AC and DC) and potential future power needs. The load evaluation will determine the types of PV systems, the size of the necessary components and the cost of the system. In order to properly perform a load evaluation for a system that will have AC loads, it is necessary to understand two related concepts: Surge loads and Power factor.

• Physical evaluation: The gathering of information about the geographic location, the building/structure, and preexisting electrical system. This will inform decisions about the potential location for system components, the ideal mounting system, and the appropriate wire and cable types, and the necessary wire protection.

• Weather and solar resource evaluation: This information will inform decisions about the size of key system components like the PV source and energy storage system.

• Load and solar resource comparison: If there is significant season variation in either solar resource or load usage then it is necessary to perform a comparison between the solar resource for each month and the monthly energy requirements to find the month with the worst solar resource relative to energy demand. The solar resource and load evaluation for this month will serve as the basis for the design.

A load evaluation is the best place to start evaluating a potential project site as it can quickly raise questions about feasibility and cost. These steps are not independent though and may be performed in parallel or all at once during a visit to the site.