This is the fourth in our series on important things to keep in mind when performing technical due diligence on a solar asset.

View previous Due Diligence 101 articles

Today, we're diving into the nitty-gritty of overall system design — the final piece of the puzzle in our series on due diligence for purchasing operational solar farms. Strap in; we've got a lot to cover!

So, the site's installed at this point, right? It's there, standing tall and soaking up those rays. But what we need to figure out is if it's doing what it's supposed to. Is it living up to its design, churning out power up to its expected output?

Control systems

First stop on our checklist: SCADA, or supervisory control and data acquisition systems. We're peeling back the layers, looking at historical data, scrutinizing the design from an inverter standpoint, checking on module health through infrared flyovers — it's like giving the solar farm a thorough checkup.

By carefully analyzing the array, we can identify hotspots and other defects that could cause performance and safety issues over time, including fires.

Degradation

Is the site aging gracefully, or are we dealing with premature wrinkles? If it's the latter, we need to find out why. Is it obsolescence, underperforming components, or a bit of both? Our detective work begins with a close look at the single line diagram — our telltale document in the quest for answers.

How many modules are there? How are they strung together? What size inverters are in play? We scrutinize the design, the way the DC side is collecting power — whether it's underground, in cable trays, or just hanging there.

Shifting equipment

Now, if the site is a hill or a slope, we've got to keep an eye on erosion. I've seen erosion turn a peaceful site into a chaotic disaster zone. Rocks, direction, piles — the whole nine yards. It's like nature doing its own remix of the solar symphony.

And let's not forget about rooftops. Ballast blocks are like the unsung heroes, and we want to make sure they're where they belong. We’ve seen numerous examples of ballast blocks being moved from their original location, sometimes being used to stabilize other rooftop equipment. Disappearing ballast blocks can become a major safety issue.

Structural and soil checks are crucial. We're looking for any signs of instability, loose bolts, or modules threatening to take flight.

Analysis of project portfolios

Now, the real challenge comes in a portfolio of sites. You can't inspect them all, so you've got to be strategic to ensure that the sample you choose for analysis is representative of the overall portfolio.

Were each of the sites built using the same equipment? Did the same EPC manage the construction? Are some sites ground-mounted, while others are on rooftops? 

We need to consider the individual characteristics of each site and ensure that we study a diverse sample that includes these variations from site to site. If problems are identified, we can then sample more sites in the portfolio with similar characteristics, to see whether these issues are widespread vs. one-offs.

Operations & maintenance

We also review the O&M records for the portfolio. Are these sites spending more than expected to maintain their equipment? What is this money being spent on? Is the scope of the O&M agreement adequate for this site? These records can help paint a fuller picture of the site’s overall performance and cost to operate.

Comparison with original design specifications

Was the original design implemented according to plans? Did this design incorporate the right standards of workmanship? Were any key details left out of the original design? By carefully reviewing the development, construction, and interconnection documentation and results, we can identify other problems or concerns that might affect a site’s performance. 

So, there you have it—system design in a nutshell. It's a mix of detective work, common sense, and a dash of foresight. Because when it comes to solar farms, you've got to ensure they're not just soaking up the sun, but also delivering on their promises.