The long read: Operator, connect me

Share

From pv magazine, April edition

The market for operations and maintenance in solar is a challenging one, as evidenced by the many providers that have exited the segment or been acquired by larger players in recent years. Costs have fallen steeply, and investors and plant owners are aware that O&M activities can have a huge impact on a project’s revenue – with industry players estimating that well managed O&M can increase a project’s energy output by as much as 30%.

In previous years, O&M services were often provided by EPC companies, which would add the service to construction contracts, and simply carry out maintenance on faults they could see and provide owners with a daily report or similar detailing the plant’s overall performance. And funding these services through a warranty structure rather than a set contract has caused problems for many. “Worldwide, a lot of O&M providers have gone out of business,” explains Jamie Mordarski, Director, O&M Americas at SMA. “It was an attractive deal on paper, for investors to see O&M included in an EPC contract, but a lot of these companies weren’t that good at doing it.”

Today, large players are moving into the O&M market with highly specialized offerings, often acquiring project portfolios from older companies, and deploying technologies and expertise capable of cost-effectively monitoring thousands of data points in real time and detecting faults right down to individual cells within a module and other small system components. “EPCs are not interested in O&M anymore – often it doesn’t fit their skill set or business model, which is based on a ‘build and move on’ type of strategy,” continues Mordarski. “Maintaining on a budget over a long period of time requires specialist knowledge and focus. Five years ago, prices were much higher. Now the technology has changed, and investors are asking many more detailed questions.”

Inverter manufacturer SMA has ramped up its O&M activities over the past four years, and currently monitors a 3.6 GW base of projects worldwide, having acquired portfolios in North and South America, and plans to move further into the Australian market.

Finding fault

The addition of aerial imaging, real time monitoring, big data analytics, and other technologies to the O&M playing field greatly enhances an operator’s ability to identify faults in a PV system’s components and allows technicians to work much more efficiently, further optimizing the cost structure.

While the availability of granular performance data and more complex analytics software is certainly of use in narrowing down where performance loss is occurring within a large-scale solar plant, it has not reached the level that would be required for effective fault detection across all system components. “In many facilities, granularity of data only goes down to the combiner box level, and there’s only so much you can do at the level of a thousand modules or so,” says Mordarski. “You can detect string issues through the monitoring system, but not component issues such as hot spots or hot connectors.”

Further into the future, the application of module-level power electronics and other ‘smart’ components, able to produce their own data and even issue notifications to operators when their performance drops, could provide operators with the ability to carry out fault detection at the component level using only monitoring data. These technologies though, still have a way to go and many hurdles to overcome in terms of cost reduction and optimization to demonstrate their effectiveness in large-scale solar projects. So for now, thermal imaging technology is a valuable asset to operators looking to troubleshoot their projects. The rise of affordable drone technologies over the past few years is a well-documented phenomenon. And for solar O&M providers, thermal imaging scans conducted by drone are a valuable resource. “Using a drone and a very high-resolution thermal imager you can find faults that would not be visible through data analytics,” says Mordarski. “You can actually get down to cell level.”

Mordarski goes on to explain that drones deployed by SMA take thermal images at a resolution of 5 cm², and color images at 2 cm² from a height of around 45 meters. Full scans are typically done once a year, though twice a year would also be cost-effective. He also notes that since aerial scans do not require technicians to touch or even get close to the electrical components, they are far safer than other testing methods.

While the cost of drone scans varies depending on plant size, location, airspace, terrain, and the level of analysis/detail required, he estimates the cost, based on a 5-15 MW project built in unrestricted airspace in the United States, to be in the range of $350-$500/MW, including analysis and delivery of a report within two weeks. “The cost of doing aerial IR scans is small in the cost of the total O&M,” he says. “Generally, payback is immediate, and we have seen some projects realizing up to 20 times the cost of the initial aerial scans immediately.”

Missed connections

Most of the common faults for PV systems will show up on a thermal image scan, but not all are visible from the air. So while drones are useful for identifying hot spots and other cell/module issues, scans using handheld imaging equipment are also conducted by technicians on the ground, focused on other system components such as inverters, combiner boxes, cabling, and connectors. “It depends on the contract scope, but generally we have the teams walk down the back of the modules with handheld scanners when doing the combiner box maintenance on that section.” Mordarski says. “Some contracts call for 100%, others may only be small portions due to the large size of the facility and owners’ cost model.”

A survey presented by SMA at the recent Utility Scale Roadshow in Australia used thermal imaging to characterize faults in a 1 GW sample of PV systems. The survey found that the most common fault identified was issues with cabling and connectors.

“Hot connectors are a very common issue, particularly in the first couple of years after installation. Most often it comes down to installation errors,” says Mordarski. “What we see is facilities built by EPCs who hire subcontractors – they rush and of course they make errors.”

The manufacturers of these components agree that while other factors are at play, the relatively high level of cable and connector faults seen in the field is primarily an installation issue. “As much as it looks simple, the opposite is true. Appropriate care of the cable, selecting of appropriate cable management, and knowledge of correct assembly of the connectors – those are just examples of what is frequently underestimated,” says Jan Mastny, Head of Global Sales at cabling manufacturer Leoni. “The situation in the field is that we frequently see installers who do not have any special training, and do not actually understand the key points that they should be observing. Any sort of systematic control of the connector assembly ex-post is basically impossible.”

And using the correct combinations of cable and connector is another issue that is frequently flagged as the cause of faults in these components. “When selecting a connector, you also have to consider the type of cable you have,” says Eric Ast, Head of Global Business Development at Stäubli Electrical Connectors AG. He explains that cables differ on their conductor cross section, diameter, and other parameters, and that there are different connector types for each. “Sometimes the requirement list for a project would just say ‘MC4 type connector’,” Ast continues. “People put a lot of effort into selecting the module and inverter, but pay less attention to the other BOS components.”

But quality of materials is also an issue here. SMA estimates that in 25% of the connector faults it identifies there has been arcing or another type of component failure. Mastny, meanwhile, warns of the well-known issue with EPCs and project developers looking to cut costs and failing to double check standards when it comes to the smaller components in an installation.

As an example, he cites some manufacturers who have in their datasheet references to waterproofing standards that are either non-existent, intended for totally different applications than PV, or a national standard or similar, which has nothing in common with EN or IEC norms. “Unfortunately,” he says, “there is a remarkably large number of procurement people, who would simply believe the specification, and the consequences are not taken into consideration.”

Impacts and solutions

These types of fault can be ‘slow burners,’ that are difficult to detect, and don’t have an immediate effect, but slowly get worse over months and years.

“A typical example is the direct burial of a cable not intended to be used in such a way. The moisture will penetrate slowly, and gradually increase the resistance of the cable,” says Mastny. “Detecting such a failure is close to impossible in the early stage, and many people would wrongly interpret the power loss as degradation of the modules.”

When it comes to fixing the faults, Mordarski says it is simply a matter of cutting off the hot connector, stripping the cable, and remaking the connection. The costs can sometimes be covered by the EPC warranty, but otherwise will be charged by the O&M provider under time and materials. Regulation is one way to keep such avoidable faults in installations under control, and Stäubli’s Eric Ast mentions a new regulation being introduced to the U.S. market, which will require manufacturers to include a list of approved and certified components with its products. “We see a lot of statements from certification bodies saying that power plants should use connectors and cables from the same manufacturer and of the same type,” he explains. “But still, a lot of cross mating and similar issues are found in the field.”

Ultimately though, Ast’s view is that the industry is beginning to move in the right direction: Focus on quality must be maintained and knowledge shared with all players. “The main reason for these faults is lack of awareness,” he says. “It’s still happening and for sure it’s too much. But the level of education is growing. Particularly in more mature markets, you have the lessons learned from the past.”