For those who submitted questions during the webinar, thank you. We’ve compiled your questions and answered them below:
Q: What are the expected O&M costs (with figures) throughout the project life for a single-axis tracker (SAT)?
A: For the first year, the expected maintenance cost is $645,000 (for a 100MW), including vegetation management, array cleaning, eBOS etc. From year two onwards, the cost escalates based on labor rates, equipment rentals, locatin, and other factors specific to each site. There are minimal costs associated with tracker part replacement (by year 10). Please reach out to email@example.com to get more info.
Q: What is the design life of NEXTracker? Increasingly, developers use 40 years pro-forma for PV project economic analysis. What implications does this make on the design life and O&M cost of the trackers?
A: 80% of tracker system is steel, and should last long past 40 years. The O&M costs would remain the same year to year over that same time period. Additional cycles may need to be added for worn out components such as the battery.
Q: How many nuts and bolts – or fasteners – are used in centralized trackers over decentralized trackers?
A: In our analyses, we’ve found that linked-row trackers typically use 85% more fasteners than are used on the NX Horizon self-powered trackers.
Q: What type of third party testing is usually required for the single-axis tracker system (by IEs, etc.)?
A: NEXTracker goes through rigorous testing including wind tunnel testing, structural integrity testing, reliability and stress testing, among other tests. See here for a list of independent engineering firms with whom we work
Q: What is role of Brightbox software technology for O&M?
A: In August of 2016, NEXTracker acquired a software company called Brightbox. Their team is now integrated into our software engineering team and their work drives our digital O&M services we offer. Please reach out to firstname.lastname@example.org to get more info.
Q: What about on project sites where there are corrosive elements like sand, dust, or moisture? Will there be more expected maintenance and replacements of components?
A: All NEXTracker drive and control components are protected against ingress of moisture, dust, and sand, and are rated IP65 or higher. Fully sealed gearboxes and motors are maintenance free for life, and no critical components are exposed to the elements.
Q: What is the O&M cost per watt for single axis tracker vs fixed tilt?
A: In reference to the chart below, 3% of the total cost of O&M goes toward a single axis tracker. For a 100 mw site, the cost per watt it is approx $18,000.
Q: What are the ground condition required for SATs? Can they be built on soft soils?
A. Yes, trackers can be built virtually anywhere. The local geological conditions should always be a consideration for mounting and installation of single-axis tracker solutions.
Q: Do new cleaning robots reduze the O&M costs for centralized trackers impacting positively on the competence of this solution?
A: As noted in the webinar discussion, everyone, including NEXTracker, is looking at the capability of cleaning robots. There is a CAPEX cost and maintenance cost to the robot, which is not yet defined.
Q: What is the most commonly replaced item in a decentralized tracking system?
A: Since the battery life is 10+ years and the system life is 30+ years, the assumption is that the battery will be the most common replacement. The motors are brushless and because the motor only runs at 1.5 amps at 24 volts, the drag on the system is nominal. Additionally, the drives are completely sealed, so NEXTracker is confident that these components will last the life of the system.
Q: Does NEXTracker offer full system O&M or just tracker support?
A: As of today, NEXTracker offers tracker support only, as opportunities arise we may do full O&M for the complete PV system.
Q: All the topics were on horizontal axis trackers, in Northern latitudes horizontal tracker becomes much less efficient. Any thought about vertical axis tracker or dual-axis trackers that would be better suited for installation in the North, for example Canada?
A: A single axis tracker does not meet every condition specific to each site. In these applications it may be best to look at other solutions or different install orientation. In general, tracker project ROI will be highest in regions with high irradiation. We recommend you consult with Solar GIS to assess the viability of your SAT choice.
Q: Other than location, what is the major driver for getting 30 % more yield compared to 20% yield?
A: There are a number of drivers. Location is key but the ability to use a smart system that allows for backtracking per row to avoid shading would also improve your overall yield.
Q: How are the trackers powered? If by batteries, what type are they?
A: Each row of the NX Horizon self-powered tracker is powered with a small dedicated solar panel. There is lithium-ion battery backup powered by the that panel panel that will drive the system during extended periods of low-light. The backup battery will provide 3 days of backup power.
Q: How do you see the use of thermal imagery, say from UAV’s, providing value for utility-scale plant O&M?
A: UAVs provide different value. Thermal imagery provides data regarding consistency across panes and potential hot spots where production can be adjusted. Furthermore UAVs allow companies like NEXTracker to evaluate the effects of panel to panel shading and create algorithms within our monitoring and control system that allows each row to optimize by itself so each row acts independently, increasing overall production on the site.
Q: Does your monitoring system communicate via a DAS like AlsoEnergy or is it independent?
A: Our monitoring system is independent and communicates back to the NERC CIP compliant hub. NEXTracker also links 3rd party systems as well as SCADA.
Q: Is there a low temperature threshold for the batteries?
A: Yes — like any battery, there is always a high/low temperature threshold. To embrace this range, NEXTracker systems placed in cold climates are equipped with a special kit that insulates and warms the battery so that it stays above its lower limit.
Q: Is there a solution for sites that have temps below -22?
A: Yes, we have a cold weather kit for the controller (battery in the controller). Projects are designed with this kit where the minimum temperature is below -22 degrees F (-30 degrees C). This project with EPC Swinerton highlights this application.
Q: Is NEXTracker the only company that can monitor tracker angle via a data acquisition system?
A: No, other companies can monitor in this way. However, many companies need to have additional equipment added to the site, including inclinometers. NEXTracker has a built-in inclinometer in every control unit that feeds back to our digital O&M giving us a clear indication of the tracker angle for each row. We then create the algorithms and find patterns on how each angle is performing on any given day, on any fleet, around the world remotely.
Q: How long does it take for a NEXTracker system to stow from 60 degrees to 0 degrees?
A: It takes less than two minutes for a NEXTracker system to stow from 60 to zero degrees.
Q: What is the expected lifetime for the motor?
A: The motors are brushless, the ampacity and draw is nominal, and there is virtually zero torque applied to the motor, so the design life is estimated at 30+ years.
Q: Is that temperature based on the record low temperature or ASHRAE extreme min?
A: ASHRAE is a third party standard. Our temperature ranges are based on the average temperatures of a given geography, topography, weather analysis and other data known by the geography. This is the sole focus of our design engineering team: to optimize our tracker in the given geography of the customer site.
Q: Do the trackers move based on a predetermined movement or can they track the sun?
A: The tracker’s movement is predetermined based on geographical location and the time of year coordinates. By definition, the tracker array “tracks” or moves with the sun.
Q: Explain your hard wired solution. Such things as motor electrical requirements, comm requirements, etc.
A: NEXTracker has pioneered the self-powered tracking system. Based on specific customer requests, we also have a system for direct wire DC. Our systems uses the zigbee mesh network, a gold standard, which reports back to a control panel. There is one network control unit (NCU) for every 100 self-powered tracker rows.
If you have additional questions, please email ProductTeam@NEXTracker.com.