Community Research and Development Information Service - CORDIS

Review of the design criteria for multi-megawatt photovoltaic power plants

This study involved a consortium of utilities and engineering companies, and its purpose was to compare and analyse the design criteria for multi-megawatt (1 to 10 MW) photovoltaic (PV) plants with the aim of optimising balance of system (BOS) design practices. Considering PVs as a viable option for the renewable energy generation, the state-of-the-art of different technical components was reviewed to indicate the best technical-economic choices, and to identify the remaining obstacles and development needs. The project's key objective was to provide details and recommendations on criteria and practices for design, hardware procurement, installation, testing and operation. A wide variety of topics, 15 in all, have been studied in detail. Consideration has been given to PV plant site criteria, as well as PV plant layout and field design, and module and panel design. The great variety of array support structures, foundations and materials has also been discussed. Special attention has been given to the array assembly and field installation to reduce the balance of system costs of larger PV installations.

Different options and practices concerning the DC circuit design, hardware and installation have been reviewed, including DC circuit design, fault detection, protection and grounding. In depth consideration has also been given to human safety, hardware safety and quality control. These considerations have been expanded to address the issues related to the connection requirements of the PV plant to the electricity grid, and utility interface design. This is required to establish maximum cost-effectiveness, adequate quality and continuity of service at the point of the electricity network. PV plant monitoring has also been considered.

This project resulted in the identification of many technology development issues. It concluded that the whole area of DC and AC circuit grounding must be reviewed, consolidated and standardised. To ensure initial module matching, quality control and degradation determination, the nameplate on each PV module should list representative data, including actual test data at two sets of operating conditions. A systematic approach to the sizing of the inverter, and in general for all utility interface criteria, is currently lacking. This, and especially inverter power quality, should be standardised. On-site and off-site monitoring in near real-time is critically important, as is monitoring criteria for large central PV plants. It is also concluded that, generally the pre-assembly of PV panels improves the projects overall costs. The current lack of widely accepted standards for array grounding and lightning protection is still a major problem for large and utility-scale PV applications.

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