TECHNICAL DESIGN OF SYSTEM
Outline system design. Essentially, this is a plan for the project’s physical development, including the lay-out, identification of equipment, and costs, etc. The system design is often required to obtain permits/consents. To select an initial conceptual design, it is worthwhile to evaluate various design configurations and module sizes, so that a design can be selected that is optimised for the site. • Assessment of shading and initial solar PV plant layout. The process enables optimisation and typically takes into account: • Shading angles. • Operations and maintenance (O&M) requirements• Module cleaning strategy. • Tilt angle, orientation, and tracking. • Temperature and wind profiles of the site. • Cable runs and electrical loss minimisation. • Production of a detailed site plan, including site surveys, topographic contours, depiction of access routes, and other civil works requirements. • Calculation of solar resource and environmental characteristics, especially those that will impact performance of technical requirements (temperature, wind speed, and geological hazards). While the accuracy of satellite data is increasing and is acceptable in many cases, it is often desirable to implement site-specific measurements of irradiation 3 as early in the project planning process as possible; the feasibility study stage is a good time to bring such data into the planning process. Note that irradiation levels often vary across seasons, and this needs to be accounted for in the financing model. • Electrical cabling design and single line diagrams • Electrical connections and monitoring equipment. • Grid connection design, including transformers and metering, etc. • Full energy yield analysis using screened solar data and the optimised layout (discussed in Section 5). • Assessment of all technology options and cost/benefit analysis of potential suppliers given the project location, including: • Module selection. This is an optimized selection based on the feasibility phase output, current availability, and pricing in the market place. Note that in countries where the solar industry is still in its infancy, there may be challenges when importing solar modules and other critical components of plant infrastructure. Examples include delays at customs and difficult negotiations on the terms of sale with manufacturers lacking a local sales representative or distributor. • Inverter selection. Manufacturers are predominately based in Europe and North America, though others are emerging in China and Japan. As above, importation can result in delays to project schedules and also the mounting frame or tracking system selection, including consideration of site specific conditions
Development of Detailed PV Design We will prepare the necessary detail documentation for the solar PV plant to be tendered and constructed. The following documentation will be prepared: • Detailed layout design. • Detailed civil design (buildings, foundations, drainage, access roads). • Detailed electrical design. • Revised energy yield. • Construction plans. • Project schedule. • Interface matrix. • Commissioning plans. Key electrical systems must be designed in rigorous detail. This will include equipment required for protection, earthing and interconnection to the grid. The following designs and specifications should be prepared: • Overall single line diagrams. • Medium voltage (MV) and low voltage (LV) switch gear line diagrams. • Protection systems. • Interconnection systems and design. • Auxiliary power requirements. • Control systems. Civil engineering items should be developed to a level suitable for construction. These will include designs of array foundations and buildings, as well as roads and infrastructure required for implementation and operation. The design basis criteria should be determined in accordance with national standards and site specific constraints such as geotechnical conditions. For example, wind loadings should be calculated to ensure that the design will be suitable for the project location.