Whether you’re a project owner, developer or EPC, your focus is on the bottom line in the short and long term, and that’s why solar tracking design is so important today—and 20-30 years from now. Your tracker system design will affect both upfront costs and your project’s levelized cost of energy (LCOE) over the lifetime of the project. In this second part of my “Best Practices for Solar Tracker O&M” blog series based on our new white paper and recent GTM webinar, we’ll explore optimal single-axis tracker (SAT) system design and technology considerations, with a strong lens on the O&M advantages of decentralized versus centralized SATs.
The Power of Independence
Centralized or decentralized SATs? That is the question that EPCs, developers and asset managers are asking themselves as they design their utility and commercial projects. In my experience in the inverter and now tracker business, that choice has a profound impact on O&M planning and costs. In a centralized or linked-row system, rows are connected via drive lines and cables and require trenches for power wiring, adding to project costs. On the other hand, decentralized trackers such as the NX HorizonTM are composed of independent rows that have no hard links between the rows or trenched cables, since each row is powered by its own motor drive and controller.
Why are independent rows so important to service guys like me? Because when you design your projects with row independence, it enables more flexible layouts and easier access between rows, an important advantage for many reasons.
Take a look at the comparison below, and you can see that there are unutilized areas of the linked-row site layout. In addition, access roads must be developed during the engineering design phase of the project to allow vehicles to access the site for routine service. With decentralized trackers, you not only avoid building access roads, you’re optimizing land use—allowing more solar trackers to be installed and increasing the plant’s power density.
Once again, from my O&M perspective, I want routine panel cleaning to be fast and easy in order to achieve higher energy performance for the system owner. With linked-row systems, motors and drives are typically located between rows, which increases the cost and complexity of cleaning. Conversely, self-powered, unlinked-row systems provide unlimited access throughout the site. As the the graphic below shows, independent trackers leave rows unimpeded for maintenance vehicles, making module cleaning and vegetation management four to five times faster than in linked-row systems—significantly lowering cleaning and upkeep costs and ultimately reducing the associated O&M expenditures by up to 55%.
Redundancy and Resiliency
A couple of other things that solar O&M people like me are concerned about are redundancy and resiliency. Both independent rows and linked-row SAT systems are composed of motors, batteries, controllers and other mechanical components that drive the action of the rows to follow the sun and maximize energy production. When evaluating SATs, I want to consider whether the failure of any individual hardware component could threaten the system’s overall production. In the case of a decentralized SAT, for example, each row’s independent motor is powered by its own dedicated solar panel (with integrated battery backup), making external power cables obsolete. With a centralized SAT system, if a power cable goes down for any reason, then that entire row stops producing kilowatt-hours.
Self-powered unlinked rows reduce the risk of asset downtime since each row is essentially its own independent system, increasing the overall resiliency of the solar plant by eliminating the risk of malfunctions that can lead to downtime for a larger portion of the installed capacity.
In my next blog, I’ll explore drive system and power requirements, as well as a rarely discussed topic for solar O&M—fastener tracker maintenance. I’ll also talk about environmental considerations, flood clearance and related topics, including a case study of how our systems fared during Hurricane Matthew.
(If you’re interested in reading the entire “Tracking Your Solar O&M Investment: Best Practices for Solar Tracker O&M” white paper, you can download it HERE. And in case you missed all of us who participated (or want to hear us again) on the recent Greentech Media webinar, “Solar Field of Dreams: Tracking Your Solar O&M Investment,” listen and download the presentation HERE.)