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Trunk Bus Technology, What Next Generation Solar Construction and O&M Have Been Waiting For

Jay Shaw's picture
Energy Professional Just Lead, LLC

Energy Professional with over 25 years experience in Fossil Fuel, Geothermal and Solar O&M. A key influencer in the areas of safety, leadership and cultural driven excellence....

  • Member since 2020
  • 5 items added with 3,849 views
  • Jun 22, 2020

I recently had the pleasure of visiting with Mahesh Morjaria and Rajni Burra of REPlantSolutions. Mahesh is the CEO of the newly formed organization located in Tempe, AZ. REPlantSolutions has two major product lines, one being a robust and well-refined Power Plant Controller, and the other line is an innovative trunk bus system and components.

As margins begin to slim in the O&M world, legacy issues like wire ties and complex harness schemes have come back around to haunt. Wire management is becoming almost a full-time job for some technicians on large scale sites. Some solutions have been developed, including high-pull, UV resistant wire ties. Still, in the long run, better installation solutions are required to alleviate the massive amount of wire utilized in collection systems. Fortunately, innovative trunk bus system installations on newer plant sites are going to all but eliminate this costly O&M activity.

In my conversations with Mahesh and Rajni, they introduced me to the REPlantSolutions trunk bus system. This system, designed as part of the installation package for First Solar Series 6 modules, can match almost any panel manufacturer’s installation requirements. The wiring is a simple system that connects six First Solar Series 6 modules or 28 – 30 c-SI modules together to accumulate 1500 Vdc.

 Rather than individual tables having individual home-run connections to a combiner box, the tables tie into the trunk bus itself. The system allows multiple tables to be accumulated on to one trunk bus, reducing wiring needs, and reducing the labor to install. Numerous tables connect into an array utilizing only three wires, a Positive run, a negative run, and a messenger wire used to suspend the other two and to ground the tables as well.

As illustrated above, the trunk bus system is a clean way to install collection systems on plant sites. The advantages gained for construction include:

  • Simplified aggregation of PV modules
  • Between 20 and 25% lower BOS material costs
  • Reduction in labor costs by over 1/3

While the overall cost reduction on the installation side is impressive, the advantage to long-term O&M and wire management is significant as well. Those savings include:

  • Significant reduction in wire management activities
  • Easier troubleshooting
  • Ease of repair and splicing

As trunk bus systems are adapted, the reduction in space needed for wiring should allow a compact plant design, thus reducing the overall footprint. Additionally, with thoughtful design, trunk bus systems allow for clear isles inside the arrays, which provide unobstructed access for O&M personnel. Open isles will provide further savings by enabling weed control, vegetation management, and panel washing to take place in a continuous run, reducing staff-hours and the need for specialized equipment. Much of the site management activities that have been reserved for night work when tables are laying flat can take place at any time due to the open East to West access.

A full trunk bus system will consist of cabling, insulation piercing connectors, and covers, trunk bus combiner boxes, hangers for wire management, and various end caps and splice covers. Installation is simple, using a tapping screw to attach the hangers into the table posts, the messenger wire is then connected and screwed in tightly to ensure a bond. Next, the positive and negative wire run installations take place.  Lastly, series of panels are connected to the positive and negative wiring utilizing insulation piercing connectors. Negative and positive runs are terminated to combiner boxes and run from combiner boxes to PCSs are established.

These innovations will provide cost savings from the building of a facility to its end of use. REPlantSolutions is not the only provider of these types of systems, and I look forward to seeing manufacturers and suppliers provide even more innovative and efficient systems that will allow the industry to become a genuinely low-cost provider of energy.

Much thanks to Mahesh and Rajni for the time they spent with me. I plan on discussing some innovations in plant controller systems in another article derived from the time I spent with the leadership team at REPlantSolutions.  

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Thank Jay for the Post!
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