Study Finds Utility-Scale Solar Plants Degrade More Than Owners Initially Assume
Researchers from the U.S. Department of Energy’s Lawrence Berkeley National Laboratory and the National Renewable Energy Laboratory recently published a report in the Journal of Renewable and Sustainable Energy. The study, “System-level performance and degradation of 21 GWDC of utility-scale PV plants in the United States”, assessed a fleet of 411 utility-scale PV systems, totaling 21.1 GWDC of capacity, commissioned from 2007 to 2016. These photovoltaic (PV) systems contributed more than 50% of the total solar-generated electricity in the United States. The study found that system-level degradation rates of utility-scale PV systems were higher than assumed when initially deciding power purchase agreement (PPA) rates. Ultimately affecting the potential internal rate of return (IRR). It also found that newer PV sites degrade less, and PV sites in high long-term average temperatures degrade more.
The study focused on system-level degradation rates rather than module-level degradation rates. In the past, studies have focused primarily on module-level performance and degradation, which ignores essential system components, such as trackers, inverters, and breakers. These methods ignore these component’s effect on the “balance of system” and a PV system’s overall performance. The researchers found that at the system-level, degradation rates are higher than the rates used in PPAs, due to the majority of PPA rates using the module-level degradation rate of 0.5%. System-level degradation must be weighed when forming PPAs. By only using the assumed rate of 0.5% degradation, and with all other associated costs considered, asset owners and investors can expect an IRR of 10%. However, they’ll only receive a 5.1% return if the actual degradation turned out to be 1.0%, and a lower 2.6% return if degradation is the suspected 1.3%.
Utility-scale solar photovoltaic (PV) ground-mounted systems are the largest sector of the overall solar market within the U.S., and the fastest-growing form of renewable power generation. Nevertheless, most of the utility-scale PV systems used in the study were commissioned after the year 2014, showing that the industry doesn’t have extensive data on long-term utility-scale PV systems performance, unlike smaller PV systems. Due to this, Asset Owners and investors should require more rigorous and frequent monitoring of their PV systems and rely on the collected data rather than the assumed degradation. This finding is in line with the study Raptor Maps produced for the 2020 Solar Risk Assessment Report, where we found that diode and string anomalies were 60% more frequent after the first year of operation, read more about that study here.
String level anomalies in a utility-scale PV system identified through an aerial thermography inspection.
It is necessary to perform frequent and standardized preventative maintenance inspections to combat the lower rates of return and high degradation levels. However, completing inspections at this magnitude while a portfolio grows will be strenuous on the operations and maintenance (O&M) teams and resources. By utilizing aerial thermography, O&M can scale affordably, and reduce the stress on labor resources, allowing organizations to monitor the PV systems regularly. Aerial thermography, when coupled with software post-processing, equips O&M teams with a standardized inspection method, and transparent data to enable efficient site remediation and prevent future performance issues. Raptor Maps provides accurate post-processing analysis of aerial thermography data to reveal the performance of PV systems. Our turnkey services enable the fastest adoption of aerial thermography and analytics worldwide.
System-level degradation rates need to be considered when formulating PPAs, and rigorous monitoring is required to ensure the Solar Industry continues its substantial growth. Raptor Maps has analyzed over 20 GW of solar PV systems, spanning 30+ countries around the world. To learn more about Raptor Maps and our software and services, please contact us.
Greentown Labs, the world’s largest cleantech incubator, hosts Raptor Maps and Enel Green Power to discuss start-up and corporate partnerships.
Greentown Labs invited Raptor Maps, a member company of the cleantech incubator, to a Fireside chat with corporate partners, Enel Green Power. Raptor Maps’ CEO and co-founder, Nikhil Vadhavar, and Enel Green Power’s Sander Cohan discussed strategic start-up and corporate partnerships, approaching them, and how they can benefit both companies. This article was originally written by Reena Karasin, the Community and Content Manager at Greentown Labs.
Both Enel and Greentown Labs member Raptor Maps describe the start of their relationship as exceedingly “casual.” Neither anticipated that they’d ultimately partner to ensure the operation of Enel’s solar assets worldwide—they started just by testing out drones at an Enel solar farm.
But that experimentation with various data capture and analysis protocols resulted in a ten-fold improvement in inspection speed, issue identification, and overall efficiency. Those impressive outcomes and the informal relationship building that went along with it proved crucial, both companies say.
At a Fireside Chat this spring, Raptor Maps CEO Nikhil Vadhavkar and Enel Green Power North America’s Director of Innovation Sander Cohan shared the story of their partnership and offered advice for startups that want to collaborate with corporates. Enel is a Greentown partner, and its Boston Innovation Hub is headquartered at Greentown to facilitate collaboration with members like Raptor Maps.
Raptor Maps uses artificial intelligence and thermal imaging to pinpoint electrical issues, outages, damages, and obstructions (think dust, bird droppings, or overgrown trees) down to the exact solar panel. This type of information has become crucial as the solar industry grows globally.
Raptor Maps and Enel work together to manage real-time operations across the corporate’s solar portfolio.
RAPTOR MAPS CEO NIKHIL VADHAVKAR
“Raptor Maps solves a very fundamental problem by helping us automate and digitize a previously manual process,” Cohan told the Fireside Chat audience. “Enel maintains several dozen gigawatts of solar globally, and these are large facilities. What Raptor Maps’ process allows us to do is turn a days-long process into a minutes-long process.”
While they had already established informal relationships, their formal partnership began with the Massachusetts Clean Energy Center’s InnovateMass program. Through the program, Enel and Raptor did formal testing of the technology and Enel provided feedback on how the product could be most useful for their company.
When the InnovateMass opportunity arose, Raptor Maps and Enel’s prior relationship helped all the pieces fall into place.
“We knew exactly who to call and say, ‘Hey, we’ve got this idea, we think you guys are a really good partner, can we get this paperwork done and apply for this?’” Vadhavkar said.
For startups that are looking to collaborate with corporates, Vadhavkar advised that they should still work with smaller customers even while chasing a big partnership deal. This split strategy means that startups aren’t relying on corporate deals as a “lifeboat,” and that they can continue to iterate on their technology, meaning a better product for the target corporate.
Cohan emphasized the importance of patience and relationship building, explaining that a startup’s technology likely won’t be a perfect fit for a corporate initially, but that the two can grow together over time.
“The reason why we have an Innovation Hub at Greentown Labs is we want to be in constant exchange with companies in this ecosystem,” he said.
Check out a video on Enel and Raptor Maps’ partnership here!
Listen to a recording of the Fireside chat here!
“Rarely does a single investment yield both significant social and financial benefit. In this way, solar is unique: this rapidly growing asset class offers the promise of substantial returns on investment in both.”
-kWh Analytics, producer of the Solar Risk Assessment Report.
The Solar Risk Assessment Report: 2020 is a quantitative, data-driven, analysis of risks across different fields in the solar industry. The report is compiled of articles from industry experts in their respective areas, each providing in-depth data and insight into the associated risk and methods to mitigate them. In this year’s edition, Raptor Maps was invited as one of the eleven contributors, writing alongside some of the solar industry’s most respected companies, including DNV-GL, Nextera Analytics, WoodMackenzie Power & Renewables, Radian Generation, Origis Services, and others. Raptor Maps was chosen to represent the aerial thermography inspections and the post-processing scope of the industry. Our contribution to the compendium focused on the importance of performing rigorous, high-detail commissioning inspections to reduce the transfer of risk to asset owners and minimize a probable increase in performance issues, as shown by the data.
An example of a thermal anomaly in a solar PV system.
There is a transfer of risk to the asset owner when a solar PV system is commissioned, a crucial step before the Commercial Operation Date (COD). To minimize performance risk and increased costs, a detailed commissioning inspection is required. This also benefits the Engineering, Procurement, and Construction firms (EPCs), which can address issues prior to demobilization, as well as asset managers and operations and maintenance (O&M), which can establish a thorough performance baseline. Our analysis found a high level of anomalies detected at commissioning, followed by a lull in the year one of operation, followed by a large and sustained increase beginning in year two. This suggests that asset owners should opt for high-detail commissioning inspections before the COD, as unresolved issues will become present later on, causing operational challenges and inefficiencies. By conducting a meticulous commissioning inspection, teams can identify and address potential performance issues before they manifest. In turn, this reduces the transfer of risk to the asset owner and improves efficiency for EPCs, asset management, and O&M teams with a strong baseline at the start of the asset’s lifecycle. Aerial thermography coupled with accurate data post-processing software enables this both quickly and affordably.
The scatter plot illustrates two anomaly types. The “Diode” classification refers to activated bypass diodes or multiple degraded cells corresponding to a single bypass diode. The “String” classification refers to an entire string of series-connected PV modules that are offline. The x-axis is days after COD, and the y-axis is anomalies normalized by MW for the inspection.
The data set used to support this conclusion is comprised of 347 aerial PV inspections across 4,723 MW of PV systems. 96% of modules inspected are Bloomberg Tier 1, representing 12 manufacturers. Inspection times ranged from the commissioning inspection through 1,000 days past the COD. The data for this data set was collected through a standardized and proven method. The flights were conducted according to a pre-programmed standard operating procedure (SOP), and imagery being high-resolution color (RGB) and infrared (thermal) imagery at either 5.5 cm/px (typical for US preventative maintenance inspections) or 3.0 cm/px (IEC TS 62446-3:2017 compliant, typical for commissioning and warranty claims) with detector sensitivity of less than 50 mK. Click here for more information on our data requirements and flight guidelines.
Download the full 2020 Solar Risk Assessment Report for free here. To learn more about Raptor Maps and our services to the solar PV industry, contact us.
Start Successfully Inspecting Solar PV Systems with Thermal Imaging Drones
This is the second part of the two-part series on the most effective and efficient ways to inspect a solar PV system with a thermal imaging UAV (drone) also equipped with a high-definition visual (RGB) camera. Read part one of the series here.
This article presents detailed information about technical requirements and best practices that you must follow to correctly inspect a solar PV system and obtain aerial inspection data (site imagery) to the highest standard. This is necessary for correct analysis and accurate and detailed inspection deliverables and reports. The following paragraphs will break down the correct inspection practices, and a post-inspection checklist created using best-practices from drone pilots with 100s of successful aerial PV inspections.
Best Practices to Follow During a Solar PV Aerial Inspection
Ground Sample Distance and Flight Altitude
Upon arriving onsite at the solar PV system, pilots should follow their standard pre-inspection checklist and review all hardware thoroughly to confirm it meets operating conditions. Before beginning the first flight of the inspection, pilots should re-confirm all flight specs are set up correctly in their flight planning software, there are sufficient levels of irradiance (600 watts/meter²) and that the right GSD (ground sample distance) and overlaps are set correctly for the solar inspection. GSD and overlap details can be found here. The GSD, or required image resolution for this inspection, is determined by the inspection level and deliverable requirements from the end-user/client. Many times pilots inform us that they are unsure of the level of inspection due to unclear requirements from the client. GSD specifies the level of detail of the inspection, a lower GSD equates to more detailed imagery, and in turn higher quality data. The level of inspection is predetermined and establishes the required altitude and GSD for the solar PV inspection. Read an article about GSD here.
Angling the Gimbal to Avoid Glare
After determining the correct GSD and altitude and confirming the irradiance levels, the pilot needs to adjust the thermal and HD visual imaging camera gimbal to prevent glare reflecting off of the solar panels and back into the camera, ruining the data. The gimbal also needs to be adjusted/rotated to capture data at the right angle and orientation to the solar rows. In addition, if the solar PV system is on trackers, the camera gimbal should be continually adjusted to be at the correct angle for data capture. Depending on the amount of time it takes to complete the inspection, the trackers could move several times as they follow the sun’s movement, and the gimbal of the drone should be adjusted regularly for this. Solar farms requiring less than an hour or two of inspecting, smaller than 10 MW, will only require you to set the gimbal in the beginning. Larger solar farms that require an entire day on-site to complete the inspection, sites as large as 30 or 50MW, will require several adjustments to the gimbal. When inspecting PV systems that are fixed-tilt ground mount, the gimbal will only need to be initially adjusted for glare and angle of the solar modules.
It’s important to constantly monitor the site while performing the inspection and pilots need to confirm the solar PV system is operating and producing energy during the entire inspection. If the site stops working and the inspection data will show nothing and be useless, requiring the site to need to be reflown when it is operating correctly.
One highly valuable practice that drone pilots inspecting solar farms larger than 1 or 2MW should follow is having multiple fully charged batteries and a battery charger with them, that can charge several batteries at once. Due to the size of some solar PV systems, it can require multiple battery changes to complete the inspection, and drone batteries run out of energy much faster than they charge. Following this, pilots should check the data quality during battery changes and remove the SD card that was just used on that mission and inserting a new SD card between each mission. In addition to checking the data, battery changes provide pilots an opportune time to reconfirm that irradiance levels haven’t decreased. Read about what correct data is in our Knowledge Hub. By regularly checking inspection data, pilots reduce the risk of needing to refly due to equipment malfunctions or data corruption, after already leaving the site. Images should constantly be backed up on a computer while in the field as well. There have been 100s of instances where the camera stops taking images partway through the inspection, and without checking the data in the field the pilot would need to figure out what area of the farm to refly after completing the inspection.
DJI TB60 Intelligent Flight Batteries.
Metadata and Avoiding Obstructions
When checking the data, pilots should ensure that the metadata is being correctly collected. The metadata must contain GPS location, relative altitude, gimbal pitch/yaw/roll, and a timestamp in each image captured during the solar inspection. Metadata is necessary for post-processing and to keep detailed records of the PV system condition and compare the change in site condition over time.
In addition, pilots should be wary of trees, buildings, and other obstructions throughout the duration of the flight. As well as high gusts of winds that could potentially blow the drone off course and into something. This will avoid any damages to the PV system, drone, other obstructions, and injuries. This will require the pilots to be attentive to the drone mid-flight, as well as the flight path that has been set. The possibility of unnecessary costs and insurance claims can be removed by remaining aware of the surroundings throughout the flight.
Post-inspection Checklist for Data-Processing Success
Before leaving the solar PV system that was just inspected, pilots should follow the listed best practices to ensure the captured data will be uploaded to the data-processing software platform quickly and successfully. Pilots need to perform a final data quality check before packing up and leaving the site to confirm all inspection data was collected correctly. Once completed, pilots may begin uploading the data into the Raptor Maps cloud-based platform using the uploader. When uploading data, clearly label all of the folders. The clearest way to label the data is “Site Name – Data Type (IR or RGB) – Mission Number – Inspection Date”. If pilots capture data with the FLIR XT2, XT1, or Duo Pro 2 it is best to upload the data in one image folder. This is because these cameras take simultaneous IR/RGB imagery and the data will be uploaded chronologically. If the camera does not capture RGB and IR imagery in chronological order, the two image types should be separated into individual folders for uploading. Any orthomosaic or oblique imagery should be separated into their own folders and uploaded individually. When uploading data to a cloud-based data-processing solution like Raptor Maps, it is best to limit uploading to no more than 1000 images at a time. Internet speeds can make uploading more images than this challenging. In addition to this, if the connection fails during the uploading process, the images won’t be uploaded and you will need to start over. Data sets of this size should be uploaded in batches. Each batch should be named the same, with the only difference being the batch number, for example, “Asset Owner’s Name – Site Name – Data Type – Date – Image set 2”.
An example of correct and incorrect camera alignment with the solar PV panels for data collection.
Start Aerial Thermography Inspections Today
Aerial thermography enables asset owners, asset managers, O&M teams, engineering firms, and EPCs to quickly, cost-effectively, and accurately gather data on the operating condition of a PV system. Aerial solar inspections are able to provide 95+% accuracy on sub-module anomaly detection and drastically increase visibility into a PV system. These inspections are also an effective way to catch systemic issues related to warranty claims. Using Raptor Maps for data analysis and deliverables, teams receive accurate and actionable reports that enable targeted and efficient site remediation plans. Also, all PV system inspection data and reports are stored in a centralized location, and creates a robust historical record of site condition over time.
Contact us today to learn more about the Raptor Maps software platform and the importance of aerial thermography and data analytics.