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 Excerpt of a presentation from the EAI Solar PV Developer – EPC Meet, Chennai, Jan 22, 2013

During the Developer & EPC meet Mr. Anil Jain, Managing Director of Refex Energy, made a presentation on EPC – To Last a Lifetime. He discussed factors such as AC and DC system design, tests to be conducted before commissioning the plant, and O&M practices.

Mr. Anil Jain began his presentation by introducing his company, mentioning that as a developer-turned-EPC they were in a very good position to understand the needs of a developer and how an EPC could meet them. He spoke of some of the basic points to be considered in ensuring the plant lasts for 25 years

  • EPC
    • In-house design capabilities – To optimise the plant for site conditions
    • Capability to deliver onsite – The execution team should be able to implement the plan and design
    • Components – Choice of best quality components is essential to reliability
    • O&M – A good service provider is required to ensure proper and timely maintenance is performed
    • Design – The solar plant is designed as a series of compromises to provide the lowest levelised cost of electricity. Two vital components are
      • Modules – Attributes to be considered include cost, power output, benefits/drawbacks of technology type, quality, spectral response, performance in low light, nominal power tolerance levels, degradation rate, and warranty terms
      • Inverters – Important factors are compatibility with module technology, compliance with grid code and other applicable regulations, inverter-based layout, reliability, system availability, serviceability, modularity, telemetry requirements, inverter locations, quality, and cost

The electrical design of the plant comprises

  • DC system
    • PV modules
    • Inverters
    • DC cabling (module, string and main cable)
    • DC connectors (plugs and sockets)
    • Junction boxes/combiners/disconnects/switches
    • Protection devices
    • Earthing
    • AC system
      • AC cabling
      • Switchgear
      • Transformers
      • Substation
      • Earthing and surge protection

Other important factors are

  • Data acquisition and monitoring – The yield of the plant is monitored and compared with estimates from irradiation data to identify shortfalls and rectify defects. Also, this helps the power plants provide the required 24-hour forecasts at 30-minute intervals to the network operators
  • Construction – Quality of construction is important in raising finance for the project, particularly from international lenders. Some of the issues faced during construction are
    • Foundations not being suited to ground conditions
    • Discovery of hazardous/contaminated substances during excavation
    • Incorrect orientation of modules
    • Insufficient cross-bracing on mounting structures
    • Incorrect use of torque wrenches
    • Damaging cables during construction/installation
    • Delayed grid connection
    • Access/construction constrained by weather
    • Insufficient clearance between rows for vehicle access
    • Commissioning – Commissioning of the plant should prove that the plant is safe, robust, and performs to expectations. There are 3 kind of tests to ensure this
      • Visual acceptance tests – Detailed visual inspection of all significant aspects of the plant
      • Pre-connection acceptance tests – These are tests conducted before grid connection and include an open circuit voltage test and short circuit current test
      • Post-connection acceptance test – After connecting to the grid, a DC current test should be carried out to check that the promised performance ratio met. An availability test, usually over a period of 5 days, should also be carried out
      • Operations & Maintenance – This consists of
        • Scheduled maintenance
          • Module cleaning
          • Checking module connection integrity
          • Checking junction/string combiner boxes
          • Thermographic detection of faults
          • Inverter servicing
          • Inspecting mechanical integrity of mounting structures
          • Vegetation control
          • Routine balance of plant servicing/inspection
  • Unscheduled maintenance
    • Tightening cable connections that have loosened
    • Replacing blown fuses
    • Repairing lightning damage
    • Repairing equipment damaged by intruders or during module cleaning
    • Rectifying supervisory control and data acquisition (SCADA) faults

Mr. Anil Jain concluded his presentation by sharing pictures and details of a few of his company’s projects.