- About PRI Engineering
- About Polar Racking
- What’s Different About Polar Racking’s PRU Fixed Ground-Mount Racking Solar System?
- Design Considerations For The Caribbean
- Polar’s PRU Racking Design Hacks
- PRU Table Design For The Caribbean
- Foundation Design And Geotechnical Engineering
- Common Foundation Types For Solar Systems In The Caribbean
- Ground Conditions In The Caribbean
- The Benefits To Pre-Production Load Testing
- The Importance Of Construction Oversight
- Case Studies From The Caribbean
- Question Period
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Vishal Lala: Hi everybody. My name is Vishal Lala. I’m the Managing Director of Polar Racking. Welcome to our webinar today about selecting resilient racking for the Caribbean. Today we’re going to talk about our company, the services we offer, foundation design, and a couple of highlights from the many projects we’ve worked on in the Caribbean.
Today, two others will be speaking, Arash Yazdani from PRI Engineering and AJ Kiani, our Sales Manager for Canada and the Caribbean. Before we start to talk about Polar, I’ll turn it over to Arash so he can talk a little bit about PRI, and then we can jump into it.
About PRI Engineering
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Arash Yazdani: Thank you very much, Vishal. Appreciate the introduction. My name is Arash Yazdani. I am the Director of Engineering for PRI Engineering.
We do focus on pile design and geotechnical engineering for solar facilities. We take developers, racking companies, other players in the solar industry through the design process of foundations.
We have a team of over 10. There are four PNGs, licensed engineers. We have technicians, technologists, and a whole supporting team to oversee all your projects. And our ultimate goal is to save you money but not take on too much risk or not allow you to take on additional unnecessary risks by doing so.
Vishal Lala: Appreciate that introduction, Arash, and as we get through the presentation, we’ll have a few slides dedicated to foundation design. And again, just speaking to the experience of the combined team between Polar and PRI, working on foundations and the benefits of really having a strong foundation design matter through the lifetime of your project but through construction as well.
About Polar Racking
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So, with that, I’ll introduce the speakers and tell you a little bit more about Polar Racking. So Polar Racking was founded in 2009. This is our 12th year in business. We’re primarily solar mounting, solar panel mounting systems manufacturers. Initially, we started as rooftop solar and since then have moved into ground mount and carports. We make our foundations, ground screws, and helical piles. We supply driven piles and many ballasted foundation options as well, such as pour-in-place, pre-cast ballast, and geo ballast for all your projects.
We are a Canadian leader in this space, and we have been supplying projects in the Caribbean and US for at least the last 10 years. We have over 360 megawatts installed to date and an aggressive pipeline of projects coming up.
PRG: Flat Rooftop Solar System
Once again, we started as rooftop, and we still do quite a bit of flat rooftop systems, all over North America, including the Caribbean. Our flat rooftop solution is called a PRG. It’s a grid-based ballasted solution, which means that the grid is completely interconnected. Generally, you only need ballast in the perimeter of the array. It’s extremely lightweight, self-spacing components, very easy to build, and not much thinking while you install it on the roof.
PRR: Flush Mount Rooftop Solar System
PRR is our flush mount solution. We have traditionally done a lot more commercial flush mount rooftops than we have residential. However, the product works well for both. We have a lot of PRR installed in the Caribbean, particularly in Barbados but also in the Dominican Republic and the Bahamas. We’ve done a lot of our flush mount – very nice flush mount projects in that area.
PRU-D: Small Ground-Mount Solar System
PRU-D is our small ground-mount solution. So generally, projects under 500 kilowatts have a kind of a standard out-of-the-box design. It’s an over-design solution that can work pretty much anywhere in North America and is available through our distributors. And you can get the distributor’s contact information through our website.
PRU: Fixed Ground-Mount Solar System
PRU, which is the topic of our presentation today, is our fixed ground mount solution. And again, we’ll go through that in greater detail. We do make our own helical piles. We make our own ground screws; we supply driven piles. And as I said, we supply solutions for ballasted options. Whether that be a pour-in-place tub or a geo-ballast basket, we can work with you, based on your project, and supply everything basically from under the ground – all the way up to the complete racking solution.
PRP: Solar Carport System
And our latest product that we’re having a lot of success with these days is our PRP product, which is our solar carports. We’re very active in this market as of the last two years. And we’re gaining a lot of steam here in North America, obviously in Canada and in the US supplying many projects from California all the way to New Jersey. And we are suddenly quoting quite a few carports in the Caribbean. We’ve had yet to supply our first one in the Caribbean, but we feel very confident that will happen this year.
Polar Racking Services
We offer engineering and installation services. We don’t have an in-house crew of installers but generally work with local installers. We supply construction management and project management for sites, and that’s all built on a platform of high-quality, simple-to-assemble products.
What’s different about Polar Racking’s PRU fixed ground-mount racking solar system?
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We’re here today to talk about PRU, which is our fixed ground-mount racking solution. It’s used for large-scale ground-mount solar projects, pretty much starting at 500 kilowatts, but can be used for a 500-megawatt site as well. What’s different about PRU and the Polar Racking solution, and why does it apply well to the Caribbean?
PRU and Heavy Loads: Wind, Snow, and Ice
Our solution, designed by a Canadian company, is built for heavy loads of wind, snow, and ice. As compared to what you’re going to see from a lot of our competitors in North America, especially, our solution is a robust structure. It’s very easy to spot our system if you’re driving around, especially in Barbados, where we have a lot of systems, and then, there are competitor systems. It’s easy to identify which one of which one is a Polar Racking system because we pride ourselves on building very robust systems that last.
There are other systems out there that are built for the developer to build and flip. In contrast, we build for someone that wants to own a system long-term and doesn’t want to worry about the system, no matter what the loads are.
PRU Designed with High Tolerances
What do we pride ourselves on with our Polar Racking solution? Greater adjustability. We use the heavier gauge in north-south beams and east-west beams with fewer braces to secure everything together. With that, we’re able to provide or offer a wide range of tolerances in all directions.
We offer multiple clamping options for your modules, which include top-down, mid-clamps, or direct bolt connections. We’ve done both in the Caribbean. We have built-in wire management. Again, we’ll show you a little bit more about that and UL-certified integrated bonding. Our product is highly customizable to match your layout.
Customizable Table Design
If you tell us that you have a strength of 18, of 25, of, 13, whatever it is, we will offer a custom table design. Rather than a continuous row design, we’re able to customize our table design to match your string or to match the layout, as required. On our landscape version, we can pre-populate modules as well onto your table.
PRU is Compatible with All Foundation Types
And I think most importantly, from all the options we offer, we let the ground tell us what your foundation type should be. There are some players out there that are the ground screw guys or the helical guys; we know that to build a project that’s built to last, you need to do the best thing for your given ground conditions. Again, we’ve worked with driven piles, helical piles, ground screws, and ballasted solutions. We offer you options, so you’re not pinned into choosing from the best of the worst that’s available. We want to put the best of the best. That’s going to make your project last until you decide to take it out of the ground.
Design Considerations for the Caribbean
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There are some considerations specific to the Caribbean when we’re looking at a racking design overall, beyond just the foundation design.
The Caribbean has unique characteristics when you’re dealing with steel or with racking structures that you have to pay particular attention to. First of all, when you give us information about a project (or what we will be asking you when we’re designing a project) is the wind speed. Different islands have different wind speed characteristics, and we’ve worked on many islands. We’re able to accommodate that.
Corrosion in the Environment
What does corrosion look like on the site? How close are we to a corrosive environment? And again, what are the ground conditions?
We also ask for the topology of your site to help mitigate your civil costs, which we manage by adjusting our racking design and our foundation design.
What is your availability of equipment on the island? Do you have machines to drive piles or to turn screws? Is there a lot of concrete there, and is the concrete expensive, or is it inexpensive? How can we take all those factors to provide you with a design that not only works but is very buildable for you on-site?
Local Module Requirements
And then, what are the requirements from the module you’re using now? The tricky thing that we’re finding in the Caribbean is that we can design our rack to withstand the loads. But a lot of the time, the module manufacturers are the ones that have special requirements for clamping that we’re not finding in North America or in the mainland if you want to call it Canada or the U.S. We’re keenly aware of it and work with you along with your module manufacturer to come up with a solution that will not only last but will make the module manufacturer happy to ensure you get your full warranty out of the module guys.
Polar’s PRU Racking Design Hacks
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What are some of the tricks – some of the design aspects – that we use and adjust while we’re working on these types of projects? We’ve already mentioned some: heavier gauge beams and braces. We pride ourselves on having a very robust design with not so much bracing that others do. When there is less assembly required, there are fewer points of failure that make it easier to put it together in general and make it easier to maintain over the lifetime of your project. We feel that’s a very important thing to consider when you’re building in these areas with heavy loads.
Adjust Galvanization for Corrosive Environments
Thicker galvanization is another for corrosive environments; we can offer up to, from G90 to G235. If we’re talking about a project in New York, we’re generally going to G90. But if we’re talking about a project in the Caribbean, then we’re generally going to G210 or higher.
Stainless Steel Fasteners
One thing that sets Polar Racking apart is we offer stainless steel fasteners on all the connections. Some others might give you stainless steel connections for just the module connection. But we feel on these islands, stainless steel for all the connections is the way to go. Again, we do offer highly adjustable connections to the foundation to accommodate topology.
Adjustable Connections to Minimize Labour Costs
Ultimately, we know that labour costs are huge when it comes to building a solar project. To mitigate that cost or reduce that cost as much as we can, we’ve made our connections very adjustable too. And then, lastly, as I mentioned before, we offer a mid-clamp and direct bolt bonding options to your module. Something that you need to be very keenly aware of, especially if you build a project in some of these high wind zones, is the requirement from your selected module supplier. It won’t be necessarily the same as what you’re used to if you’re used to building projects in Canada and U.S.
PRU Table Design for the Caribbean
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We offer two table designs for our projects in the Caribbean. One is a standard for east-west beam design. Generally, we can offer this up to 150 miles per hour. Again, we do a lot of testing internally, a lot of simulation testing as well. And a lot of testing with third parties to make sure that our connections are strong, robust, and can withstand the given load.
The other design that we have for Caribbean projects, greater than 150 miles per hour, is a six east-west beam design. So again, this goes mostly when you have higher loads and you have a module manufacturer requirement for certain clamping, whether it be six spots or four spots, or direct bolt holes versus mid-clamps.
So, this is to show that we do have the options. They’re ready, and they’ve been deployed. We feel very comfortable with these solutions that we’re offering because we are accustomed to dealing with heavy loads and very comfortable working with these more robust designs to come up with more options for you than some of the other players in the market these days.
Adjustability is Key to Racking Design
This site particularly shows you the adjustability that we have in our product that you often won’t find in other products, especially on a driven post design, which we’re finding more and more common. We’re able to achieve more, even with a graded post design as opposed to I-beams, W-sections, or H piles.
Round Post Design Provides Structural Integrity
We prefer to use a round post design. We feel the round post design gives us greater structural integrity because it’s strong from all directions. And then secondly, it allows you a lot of adjustability in the field – you’re up-down. We show two inches here, really, you can have four or five inches depending on your orientation. I have our Construction Manager here telling me up to 10 inches, so you have a lot of play when you go with the round post design and a more structurally sound product as well.
Easy Assembly in the Field
In all connections, we’ve added as much adjustability as we can. This helps with assembly especially when you’re dealing with different topologies, but also when you’re dealing with tough ground conditions because the piles don’t always go in dead-on straight, and you want to have a product that has play enough for you to be able to adjust in the field rather than pulling out the pile, re-compacting the soil, and then putting the pile back in the ground.
And what our design does is allow you to adjust in the field. For example, we go with the discreet table design, within a table, if you have a pile that’s 6 inches off like you’ll be able to make it up just within the tolerance of the rack without having to take out the pile and do all kinds of extra adjustments. So, we’ve seen it practically in the field. And we’ve heard about it a lot from our installers that it’s huge when the rubber hits the road, you’re building, you’re under time constraints, and you need to get the job done right.
And then, just to show the adjustability on our dual-post design. We have lots of up and down, east-west, and north-south tolerances to accommodate the different changes in topology and when some posts go in the ground slightly off tolerance or off their mark.
Easy Wire Management
One of the main features of the PRU system that we take a lot of pride in is our wire management. Our channels are built for you to run your cables. There are drainage holes in all the east-west beams so that water doesn’t accumulate within the beams, and there are pre-punched holes so you can tie the wires up.
So, when you’re on a Polar system, generally you have a very clean-looking system from the front and the back. And you don’t have to spend money on additional wire trays or anything like that. So, it’s a very clean product. We do have ETL certification as per UL2703, for Canada and the US. We have a wind tunnel study from CPP.
Tested Design by Third Parties
We have a lot of third-party mechanical design testing that we’re happy to share with you or a third party, in case you have a financing company involved in your projects. And again, a lot of finite element analysis testing and internal load testing data that we’re happy to share now.
Now going back to foundations, we do offer many foundation options. So, on a single post, you can do a driven post. You can do a grouted pile or helical pile. On dual posts, you can do ground screws, helical piles, or ballasted solutions, where you can choose pour-in-place, pre-cast, or geo-ballast.
And the geo-ballast is, it’s a basket where you can use if you have a lot of rock at the site. Oftentimes, that’s where we’ve seen it used, or in those situations where you have a lot of rock on-site. You’re able to take advantage of that and create a geo-ballast basket if that works for you.
Foundation Design and Geotechnical Engineering
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With that, at this point of the presentation, I’ll turn it over to Arash at PRI Engineering. So, he can talk a little bit more about foundation design, the services offered and the advantages of conducting a proper geotechnical investigation before commencing your project, and the advantages of that.
Arash Yazdani: Okay. Thank you, Vishal. Just in case you missed it, I am Arash Yazdani of PRI Engineering, a geotechnical engineer, and my team and I have worked on over 2 gigawatts of foundation design for solar structures, across North America, including the Caribbean.
And, as a geotechnical engineer, we obviously deal with the ground. We deal with the subsurface conditions, which you can’t see, and what a lot of people call the black box of civil engineering. And, some people might wonder, well, what’s a geotechnical engineer from Canada doing in the Caribbean?
The Site Determines the Foundation Type
It really shouldn’t matter what the ground conditions are. The key is letting the geological conditions of the site drive your foundation design. Too often, we see certain racking manufacturers say, “Oh, that’ll work, that’ll work, we always use this, we always use this.”
And I just find that’s the wrong way to start a project. If you pigeonhole yourself into a certain type of foundation, it’s almost like trying to put the square peg in the round hole, and you’re forcing it. And anytime you’re forcing foundations, you could have issues arise. So, one of the main contributing factors for foundation design needs to be the geological conditions. And a lot of times, that means a very rigorous subsurface investigation program.
Other Considerations for Design
On top of the geological conditions, the racking system loads, and of course, the tolerances need to be considered. Vishal mentioned the tolerances. One of the challenges with foundations is often they’re very sensitive to potential obstructions in the underground, and obstructions can throw your foundation’s final location out of position to the point where you may need to do modifications to your racking system.
You may need to look at removing that foundation element and replacing it, which is going to be costly for the removal. And then once you get into customizing racking systems that could void your warranty or cause other issues down the road.
The other thing that needs to also be considered during foundation design is load application and frequency. So, what I mean by that is wind uplift acts very differently than frosts uplift. Snow load, obviously not being a thing here but that acts differently than wind compression loads. You always need to think about the interaction between your natural environment (the wind and the ground) and your racking system, in addition to the frequency being applied to the structure.
The Difference between Frost and Wind for Foundation Design
So, anybody that maybe is familiar with the wind. Typically, you might be familiar with the concept of gust wind or an average three-second wind. So, wind acts on a structure, and then, and it calms down. It’s not what you call a long-term sustained load, whereas frost will act over a long duration. And in fact, it’s going to grow with time as the frost in the ground. As the frost penetration in the ground expands, it gets deeper.
If you have more days under zero, the frost is expanding, and it’s going to cause more pressure on the foundation. And that’s going to apply a load over months, typically. If you’re in a Northern environment that, for four or five months of the year, it’s below freezing.
With respect to wind, as I said, it’s slow acting. So, it’s typically three seconds, which is kind of what most of the codes suggest using. But the fact of the matter is, it’s not going to be a long-term load like frost is. And so that’s different. To sustain a load that’s turbulent on-off, on-off, you need to be able to resist the load differently than if that load is slow acting and slowly but surely pushing the foundation element out of the ground. So, it is something that needs to be considered in the design phase.
Common Foundation Types for Solar Systems in the Caribbean
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Now, we want to talk about some of the common foundation types for solar racking systems in the Caribbean. So the three soil types that I’ve listed are going to probably cover 95% of the cases that you would come across in your sites.
And to go over them quickly. So soft bedrock, many of you that have been down to the Caribbean for a vacation, got on the beach, and maybe went for a little snorkel, got to see the nice coral reefs.
A coral reef is a limestone sedimentary deposit. So, it’s very similar to the limestone sedimentary deposits we see in both the Northern United States and Canada. The difference between the rock here and those depositions is that it’s a lot softer in the Caribbean. So, because of that, you can drive a pile through it. Now, well, there are some tests that can be done. But in all honesty, nothing beats doing the actual, physical test yourself on the site ahead of time in the form of pre-production testing.
The Driven Pile: The First Option
A good foundation type that we’re not seeing a lot of people use is a driven pile but that needs to be considered if the bedrock is soft enough to be penetrated. Driven piles should be one of the first options that you’re considering. If that doesn’t go successfully, another option is ground screws.
Ground Screws: Requires Predrilling
One of the challenges with ground screws is you do need to do a pre-drill. So, what that means is that if you’re trying to put a ground screw, which anybody that hasn’t seen a ground screw, just picture a big woodscrew that you use on your deck, going into the ground, it may not be able to penetrate that soft bedrock.
At times it might, depending on how soft it is, but it’s probably best to assume that you’re going to have to pre-drill. So that’s an added step and why the driven pile is more attractive. You go to the pile; you drive it into the ground, and you walk away – you’re ready to rock. For ground screws, typically you’ll need two crews and two sets of equipment. You would have one crew ahead, pre-drilling the holes, and then behind that, you would be putting the ground screw in, and then you’d be ready for racking. But once again, you’re adding a step which, is added costs.
Sometimes the bedrock might be too soft. And the ground screw might not be able to develop adequate resistance because of the disturbance caused by pre-drilling. In which case, then you’re probably looking at a bedrock micropile as the option.
We worked on a project with Polar on this and were able to help save the project almost a million dollars because the original proposition on the table was option three, the bedrock micropile. And we were able to prove that a driven pile would be successful at that site.
So, major cost savings, we’re not talking about just a couple of bucks here and there. We’re talking major amounts of money that could be saved. And, as I said during my introduction, our goal is ultimately to help you make the rice foundation decision without taking on any additional risk.
Ground Conditions in the Caribbean
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If using a driven pile means that there’s more likelihood of that foundation failing, we, as the engineering team, haven’t been successful in helping you in your project because we’ve just led you down a road of additional risk. So soft bedrock, as I mentioned, one of the key things about it is that it’s penetrable.
Hard and Soft Bedrock
When we talk about hard bedrock, that’s more of an igneous formation, volcanic in origin. This is very hard, like granite, very similar to the material that you’d have for your countertops, hard material of that. You could pound a post on it all day, and you wouldn’t go anywhere.
So, bedrock micropiles, or ground screws, I’d almost say 1A, 1B, in terms of the best option, bedrock micropile. We didn’t talk about it in the soft bedrock section, but what it essentially is, is you drill a hole, you set your pile, and then you grout it. So the added cost is the concrete.
And anybody that has experienced work in the Caribbean knows that concrete and cementitious materials are not readily available. Most of that material needs to come, like anything on the islands, on a boat. So, you’re looking at additional costs to bring in that material. And cement is a time-sensitive material.
And what that means is, when you mix cement to make concrete, and you add water to it, you have a finite amount of time where you can use that. So, it makes construction planning riskier and more challenging. So, if you can eliminate concrete from the design, you’re ultimately making your construction simpler.
With regards to the ground screws, they are a possibility. One of the challenges with the ground screws and to go back to the soft bedrock is those small threads on the ground screw can bite into the bedrock. If the rock is soft enough, it can engage into the rock and you gain your resistance because those threads are locking into the bedrock.
That’s not the case with a hard bedrock. It will file those threads. So, what you need to do in a lot of those cases is, you need to pre-drill a hole that’s larger than your threads. You’ll have to put some sand or screening material in the hole and then drive the ground screw into that after the pile. And once again, if you don’t get torque, you’re likely looking at a resolution with grout. We’ve already talked about the challenges with cement, and that it is going to cause the cost of your construction to escalate.
Deep Soil Overburden
The next type of soil, the most common soil, is a deep soil overburden. So that just means that there’s likely bedrock somewhere down, maybe 10, 15, 20 feet, but it’s deep enough that you’re going to find on the bedrock. So, you need to depend on the overburdened soils to provide your resistance.
So similarly, to the soft bedrock, one of the most, one of the biggest, one of the most usable solutions is a driven pile. The most cost-effective, primarily because it’s one process. Same with the ground screws, into a soil overburden, you may not have as many issues related to pre-drilling, but if you do come across large boulders, cobbles, there could be some obstructions in the way of the ground screws, which will then require you to pre-drill.
So, it’s possible in a soil environment, the ground screw could go in on the first attempt, but there’s also the risk that it doesn’t, in which case, you’re back to the same challenge you are with soft bedrock, in which case you have to pre-drill. So micropile, we have a lot of the same challenges as with the bedrock micropile – we talked about the concrete and cementitious material challenges.
Another issue that comes with soil and micropiles is related to hole stability. If you’ve got a wet site or a shallow groundwater table, or something of that nature, it’s possible that the soils in that borehole will not stay stable. Meaning that when you advance your auger or down the hole hammer to make your hole when you remove it, everything just collapses in.
When everything collapses in, obviously, we’re talking about another added step that the driller then needs to back up, back onto that hole, drill it back down, pull out. And it’s possible that in two, three, four, five attempts, you still don’t have a usable hole. You may need to look at casing the hole. You may need to look at some sort of de-watering method. There are several challenges that will come into play with a soil micropile. That’s obviously why driven piles are the primary choice.
The Benefits to Pre-Production Load Testing
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There are a lot of different foundation options and a lot of design considerations that need to go into designing foundations. Typically, all those challenges can be resolved through a well-thought-out pre-production load testing program. You’re not only testing a couple of different foundation types and a couple of different variations of the same foundation, but also you’re assessing constructability.
So, off the top, one of the biggest advantages of pre-production load testing is you’re verifying design assumptions. Any of you, who have worked with engineers before, know that in most cases, we collect some information about maybe one parameter, and this is very specific to geotechnical engineering.
A lot of people want to use boreholes as the main means for design. Boreholes are good. I don’t want to say they’re great. They’re good, they give you some information, but they’re very restricted. And more importantly, you do need to make some crude assumptions to transfer your SBTN value into a usable design value for a driven pile of a ground screw, or even a micropile. Anytime you need to make a correlation in an assumption, there’s going to be some level of conservatism.
So, this pile testing allows us to assume and then verify it during testing. And by verifying it, we obviously, as the Engineer of Record have a lot better grasp on what that actual value is, meaning we could reduce the factor of safety while maintaining the same resistance and confidence in the design. We’re not trying to increase your risk profile here. We’re de-risking your position by verifying our assumptions.
I talked about constructability. A design on a piece of paper with a stamp on it is all fine and dandy. But if it’s not constructible, it does nobody any good. This provides us an opportunity before you go to your site and hire a contractor to put in 3,000, 4,000 piles to assess the constructability and to provide feedback to the contractor, the developer, and the racking company on the potential construction risks? So those can be considered and resolved before going into production.
You develop a better understanding of subsurface consistency. So, what I mean by that is the ground is not like steel. Steel, when you order a piece of 33 KSI steel or 55 KSI steel or whatever you’ve specified, you are, as a minimum going to get those properties. The ground, unfortunately, doesn’t work like that. The ground could be one condition in one place. And 5 feet, 10 feet, 20 feet over, it could be completely different. And because of that change in the subsurface conditions, you may need to be looking at multiple designs.
The Benefits of a Back-up Design
A good foundation design for a site, is it one where you have one design? It’s one where you have maybe one primary design and know the constructability challenges you’re going to have and what the subsurface inconsistencies are going to be. You’re also ready with a secondary design solution that as soon as that condition arises, you’re going to pull out and you’re going to put it into action.
That’s why having a good understanding of subsurface consistency is good. And there’s no magic number. Everybody always wants to say, “Okay, well, I got a 60-megawatt site. How many test piles do I do?” Or, “How many test piles do I do?” Well, a lot of it comes down to consistency.
How many test piles is ideal?
If we go to the site and we dig 15 test piles or we put 25 test piles in and they all give us the exact same results, we’re probably good. But if we go do the same thing and half of those results are saying one thing, and half those results are saying another thing, and we’re starting to delineate the site, and we’ve got a pocket of design one here, pocket design two here, then we ask, what’s going on in this area between those? That’s where additional understanding of the subsurface conditions comes into play and is going to de-risk your project at the construction level.
If you do a good rigorous pre-production program with remediation designs in place, and you’ve got a contractor that can execute the primary design, but also the alternative designs, then you’re going to have a successful project.
The Importance of Construction Oversight
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And this is obviously very important. The other side of this is construction oversight. A lot of the projects we’ve gotten involved with after the fact, when we’ve been asked to come and look at foundations that maybe didn’t go as smoothly as they hoped, a lot of the time, it’s because there was no oversight.
So, you need to have somebody on-site during construction who understands the design, the alternatives and in what conditions. It’s not important if they’re with the construction team, the developer, or the racking team – all projects are put together differently. But ultimately, there needs to be somebody on-site who, for lack of better terms, can police the foundation design because of the inconsistency that the ground can throw at you.
Vishal Lala: Thank you very much for that, Arash. Really appreciate it. Very insightful. And, for anyone who has built projects and run into ground issues, I think they can all appreciate how important it is to get a solid foundation design before you hit the ground.
And you said it, we don’t only try to give you the right foundation design but also want to make sure to identify potential construction issues in the pre-production testing. When you’re going to the site with the information upfront, as opposed to, just saying, “Yeah, I’m going to go with a graded pile,” it will result in a cost-effective roll-out.
When you show up on-site and figure out what bones are buried in the ground while you’re there, it usually ends up costing you a lot more time and money doing it that way. I highly recommend a very solid pre-production test plan before you start building on these sites.
Case Studies from the Caribbean
Cane Gardens, Barbados
We’ve done a lot of projects in Barbados. I love this picture here, Cane Gardens, because, off to the right, you can see some of our flush mount project product on that rooftop as well. This was a 1.2-megawatt ground mount solar system with 150 miles per hour winds. We used 2×10 tables here, 150 tables, and they used a grouted pile design here because the ground was hard. We couldn’t test here, so the grouted pile was a good default in the absence of testing. Had we been able to test, there may have been a chance that we could’ve gone for a driven pile. Beautiful project, nonetheless, and very well constructed by one of our customers in Barbados.
St Thomas, US Virgin Islands
And the second project is a project that we’re building this year. It’s a six-and-a-half-megawatt project at St Thomas, US Virgin Islands. The wind loads here are extremely high, 180 miles per hour. We’re using a mix of 2×10 and 2×5 tables. This is a site that we went out to in November 2020, and we tested. As a result, we’re using a driven pile on 95% of the site.
And we have remediation options available at our disposal if, for any reason, the driven piles won’t work. There are over 2,500 foundations here, and we can’t wait to have this one completed.
Polar Racking’s Caribbean Portfolio
We’re not new to the Caribbean. We have been building projects in the Caribbean for the last eight years, and lots of rooftops as well. So, contact us if you have rooftop projects coming. We’re quoting a lot more solar carports for the Caribbean now and ground mounts all over.
Where do you manufacture?
We manufacture in Canada, overseas in Asia, in the U.S., and we direct ship into the Caribbean. Depending on where your project is, we will find the best place to manufacture it for you and get it to you cost-effectively and on time.
To what wind speeds are solar carports rated?
It’s all custom designed to your wind speeds. We’ve quoted many projects recently in Barbados, but we can design whatever wind it is. It’s a structural design as well, so we make a custom fit to the project area.
Do you have an east-west racking system? And the wind load requirements?
We haven’t supplied an east-west system, but we do have a design ready for the east-west system. Generally, we find that east-west systems are very low tilt, five degrees – there’s a lot of benefit to going with the east-west system if that’s the direction you choose to go in for. From a wind perspective, it’s easier to build.
Does your system’s design consider high salinity environments?
We do. And, for all of these Caribbean projects, as I mentioned, we use a G210 or higher and we use stainless steel fasteners. Again, that’s all to adapt to the environment that these projects are located in.
Do you have a design for Guam wind speeds?
We have designed and quoted on a project in Guam before. Unfortunately, we did not end up supplying that one. The projects that we’re doing in the US Virgin Islands are at 180 miles per hour. And I believe that Guam is the same.
What’s the model that can withstand 175 miles per hour?
It is a PRU, but again, we custom-designed this for each site. Depending on the ground conditions and the location, we’ll supply you with a design that can withstand that wind rating.
Do you have a ground table for four posts front and back posts?
The Caribbean best practice recognizes wind speeds and CARILEC recognized wind speeds is 180 miles per hour. CARILEC has accepted the RMI’s, Solar Under Storm recommendations of a four-post-per-table design as the best practice.
Yes, we do have a front and back leg design, and we do supply it all over. We’ve supplied in the Caribbean and for projects in Canada and the U.S. as well.
The RMI report is well thought out, and we appreciate what they’re saying. However, we differ in our methodology, and in the prescription to go with a 4-post design front and back leg regardless of the ground conditions is something that we don’t agree with. In certain areas, it’s going to make more sense to go with a single post design if the ground allows for it. Our ultimate objective is to give you the best design for your sites. If the best design is going with a single post driven or a single post grounded, we’re not going to push you to go to a front and back design.
There are a lot of factors to consider before landing on a design, including constructability, ground conditions, topology, and wind loads. At Polar Racking and PRI, we don’t believe that we should just ignore the two posts or single post design, as we call it, and just always go for the front and back. We have the option, we’re happy to supply it. It just has to make sense. And the engineering has to tell us that it makes sense. And that’s where we stand on that.
Would you use geo-ballast foundation in the Caribbean?
We could but it’s very site-specific and depends on what’s available. The density of the stone, the size of the stone, and how we’re going to measure the weight are all things that we need to consider. But for the right site, we’re open to looking at a geo-ballast foundation as well. We offer pour-in-place and pre-cast ballast options also.
What’s your opinion on using earth anchors on ground mount projects in the Caribbean?
Arash Yazdani: If you don’t mind, I’d like to take that question with another one because they’re kind of related. I’ll start with the anchor. One of the challenges with the anchors is going to be our subsurface condition.
Let’s think about the three common subsurface conditions we did talk about in the presentation. That’s going to be soft, rock, hard rock, or soil overburden.
One of the challenges with the earth anchor is penetrating the rock. And then in terms of the actual engagement of the anchor in the bedrock, it’s not able to really perform like it’s intended to. How they work is you pound a steel rod, then there’s an anchor at the bottom, and then there’s a mechanism that creates tension. And then that rotates a piece of steel that creates an anchor in the ground. It can only disengage in soil. There are some challenges when you’re dealing with bedrock.
The issue or the concern when it comes to the table with soil is the hurricane season. Obviously, installation, getting it in, is not a problem.
When you have a soil site, that means it’s going to be easily erodible. And if the soil is easily erodible, there’s a very good chance you could compromise the soil cover over the actual earth anchor. Meaning that if it becomes uncovered, it’s not going to do its job. If it comes uncovered, it’s not engaged in the soil anymore. And it’s not going to give you your resistance.
We have used earth anchors as a last resort to remediate piles where there are lateral issues. But to be honest with you, in a lot of cases, we only got to that case because a contractor did the work unsupervised and they ended up not following the design, and all other remediations were too costly. We used the earth anchor because that was the best means in the situation we were in.
I wouldn’t say that earth anchors should be a status quo foundation design, but they definitely could be used as a remediation option as a last resort. And I will say that if your project has gotten to the point where you’re using that as a last resort, you are going to want to circle back and verify your QC and your contractor’s installation process. There are probably some challenges there that can probably be corrected for future projects, which would eliminate the need for those risky foundation types.
Vishal Lala: Thank you for that.
I appreciate the cost will depend on ground conditions, but do you have an average cost per megawatt, in the Caribbean that we can use for budgeting?
If you’ve been on my other webinars, you know I do not like to answer this question about costs because there are so many different factors, ground conditions, the size of the module you’re using, the wind speeds, and the orientations.
Have you worked with any drainage management systems, big tables, and high rainfall rates or equal potential ground damage?
Arash Yazdani: This is the one that I wanted to deal with the earth anchor. Obviously high rainfall rates and potential ground damage.
That’s the erosion I was alluding to with earth anchors that is problematic. One of the biggest deterrence or biggest safety net for reducing your potential for erosion is getting your ground covered. You must make sure that there’s a proper growing medium as the final step. Put down four to six inches of topsoil as a growing medium that is often skipped.
It’s also important to make sure that you’re revegetating or allowing the natural vegetation to take over the site that is by far your best thing to combat erosion. That root structure is a natural system that can take care of that.
Other options are some engineered solutions such as placing a stone, or other geotextile or ground-improving measures that basically would make the ground less erodible. I’m sure all the developers in the room are saying that’s going to add a lot of costs. Your best bet is to try to maintain your vegetation as much as possible. That is by far your best form of attack against erosion and runoff.
How often do you see the three rail support requirements from module manufacturers for high wind loads?
Do you have a listing of module manufacturers who have modules that can handle wind loads?
Vishal Lala: So, the answer to your question is we don’t have a full list of everyone that can handle wind loads. Module manufacturers are constantly making our lives difficult by changing their size, and their ratings, et cetera. It’s very hard to keep track. We are seeing the requirement for three rails and more based on updated module data sheets and the install manuals, especially these new split cell modules.
If you do have a project a d a module in mind, we’re happy to collaborate with you and figure this out, together.
Do you use the HVHZ building code requirements for your wind designs in the Caribbean?
HVHZ is high-velocity hurricane zones and is part of the Florida building code. Yes, we are using high-velocity building code requirements. We provide you with stamp drawings from, either a Florida engineer or, an engineer local to the island that you’re working in.
It’s great to have a great foundation design. It’s great to have a great product but having a competent contractor to put it in and someone representing your best interests on-site to make sure the foundation is installed correctly is key to managing that risk. We think it’s worth the money because once the foundations are in the ground, someone can’t walk the site and tell you if they were done right or not.
Have a PRI engineer on-site while they’re going in and testing foundations, exactly like what we’re doing in the US Virgin Islands. And like they’ve done on many projects in New York and around Canada. It cannot be understated how valuable that will be to building a project that is going to last for a very long time.
Look forward to hearing from a lot of you on your upcoming projects and seeing you at one of our next webinars.