Market Driver: When augers, ground screws make economic sense for solar contractors

 

auger-ground-screw

The use of augers and ground screws has been of interest in mounting solar systems for some time, and for the right size job, they offer smaller solar contractors an opportunity to grow their business.

Small site factors

For one, with smaller PV systems, one may not need to spend money on a soil engineering analysis and the cost to permit the design separately. The typical soil type in an area may be known from experience. Perhaps local experience with other construction such as a home foundation or a water line installation can provide clues to the soil type.

A method used by some contractors is to use a hammer drill and ground rod available from an electric supply store and see how easily the rod can be driven into the earth. If the rod hits solid rock 6 inches below the surface, or if the rod is very hard to drive, this could either disqualify the use of ground driven foundations, or in some cases lead to using ground screws rather than augers.

Additionally, many counties and states have published maps showing the soil types for many locations. Other sources of data are well sites where there is often a record by the foot of the surface to depths much greater than one would drive a ground-mount.

Selecting a ground-mount

Once a determination has been made as to the type of soil at a site, the installer should select a ground mount to use at a site. If the soil type is not heavily compacted and not rocky, one can consider the use of augers. Most typically, a ground auger driven 7 to 10 ft. will suffice for most 3- and 4-row landscape arrays.

If the ground is compacted, made up of heavy clay, or has small rocks within the first 10 ft., then a ground screw would probably be a better choice. Ground screws offer lower torque when driving them into the soil and are less likely to break in harder ground. However, in soft, loamy soils a ground screw will not provide big pullout values compared to an auger.

If the ground is too rocky, other options such as post and concrete, ballasted arrays, or rock anchors may be a better alternative. Experience with ground arrays will greatly help in the selection of a ground mounting system.

Driving ground mounts

Some form of tractor or track machine is required to drive ground-driven foundations. These machines are easy to rent and use, and depending on the volume you are doing, worth owning. Small arrays with only 8 or 12 posts are probably not worth the investment, but between that and larger arrays that require a specialized company to drive the mounts, there is a sweet spot that makes financial sense.

The machine used will need some form of rotary head such as the small Bobcats used to dig holes for pole buildings and fence posts. Alternately, some farm tractors have a rear-mounted rotary

driver used for fence posts that may be used.
Most equipment rental yards can supply a small track machine normally used with a hole-digging auger. With the hole-digging auger removed, an adaptor can be used to mate the drive head to fit augers and ground screws. A 2 in. hex adaptor that fits the machine can be purchased by the installer if not available from the equipment rental yard with the machine.

The amount of torque required to drive a ground mount should not be more than a nominal 3,000 lbs. If more torque is required, or if the mounts are breaking, than the wrong mount was selected. If augers break, a ground screw should have been used. If ground screws break, then a non-driven mount should be used.

If occasionally a mount breaks due to an undetected boulder or other issue, a traditional post and concrete mounting should be used. In the case of Groundwater, a 50-kW project in Portland, Ore., where over 400 augers were used, eight anchors broke due to large sporadic rocks and were replaced with eight concrete-mounted posts.

Calculations and measurements

There are many resources available covering the use and calculations for commercial construction using augers and ground screws. These include Chance Hubble manuals, and other commercial suppliers of augers. However, there are some general guidelines one can follow summarized below.

Augers have a pitch determined by the blade angle. Our auger is a 10-to-1 auger. Using a 10-to-1 auger, each ft lb of torque driving the auger provides approximately 10 times the uplift capability when driven to 10 ft of depth. For example, if an auger is driven with 500 lbs of torque to 10 ft. the pullout will be approximately 5,000 pounds. Typically, augers are driven much harder, resulting in tested pullup values of 20,000 to 30,000 lbs. Most often, augers driven in reasonable soil values will dramatically exceed the pullout values actually required to resist pullout or overturn of the array.

In the case of ground screws, they are typically applied to more dense soils and solids with rock intermixed. A ground screw should not be used in solid rock.
Ground screws in hard soils have pullout values of 1,500 to 5,000 lbs at a depth of 5 ft., however this estimate is entirely based upon the soil density. The use of ground screws in soft soils will not provide a satisfactory base for a solar array.

The use of a torque measurement gauge is recommended as an additional check on the drive torque and resulting pullout capability. Some modern machines one can rent or buy have a built-in torque gauge. Additionally, there are devices that can mount between the hydraulic head and the ground mount to measure the torque. However, a careful operator will have some sense of the amount of effort required to drive the ground mounts, and in most cases can successfully install and drive ground arrays without a torque head.

Cliff Schrock is an engineering consultant with SunModo.

 


On the Scene

Ready to rack

AP Alternatives’ Ready Rack mounting hardware is designed for both large utility-scale projects and small commercial projects. The small helical anchors and quick-install cross bracing make the simple system robust even for high wind zones. The mini-tilt brackets are adjustable and allow for quick field alignment of the post height. This allows the anchor posts to be installed rapidly and any terrain variation can be accounted for by simply adjusting the tilt bracket up or down to achieve the best aesthetics on an ungraded site. This system is nimbly installed with an attachment that fits on a skid steer.

— Solar Builder magazine

APA Solar Racking explains its concrete-free ballast ground-mount system

APA racking geoballast ground mount

APA Solar Racking has changed the ground-mount ballast market by offering a concrete-free design. Featured at Intersolar this year, APA’s Geoballast Foundation was developed after years of installing ballasted solar projects. The utilization of wet concrete simply had so many hidden extra steps that would constantly increase man hours on every job. After a large amount of engineering and R&D, APA was able to take the idea of a standard Gabion Basket and transform that idea into the most cost effective ballasted solution in the solar industry.

The Geoballast was soft launched in late 2017 and is proving to be a very popular and cost-effective solution for ballasted projects of all sizes. With multiple projects underway, APA customers have improved their installation time and maintained their budgets.

RELATED: We shift you not: A ground-mount solar system without piles

The galvanized steel Gabion baskets are hot dipped and epoxy coated for extra protection and ideal for landfills, pavement and brownfield sites. The ballast foundation is shipped 70 percent pre-assembled and filled onsite with standard quarry rock. Anchor tubes connect the ballast and racking with no earth penetration. Ballast staging can also greatly reduce installation time. They can be easily moved with a skid steer or carried to each location before filling with rock.

APA racking geoballast

The Geoballast is compatible with 2 in portrait or 4 in landscape designs and can accommodate snow loads to 70 psf and wind speeds to 130 mph.

— Solar Builder magazine

Total clean energy disruption is here and three other takeaways from Intersolar 2018

Starting with the opening keynote presentations on through the innovations on the expo floor, Intersolar 2018 was all about disruption. Yes, even those of you already succeeding in solar today, if you’re not careful, you could be disrupted too. Here’s what jumped out at us in San Francisco last week.

1. Total clean energy disruption is coming, and it’s bigger than you think it is.

Intersolar 2018 coverage (53)

Keynote speaker Tony Seba was the disruption tone setter. For those unfamiliar, Seba is a Silicon Valley entrepreneur, an instructor in Entrepreneurship, Disruption and Clean Energy at Stanford’s Continuing Studies Program and author of Clean Disruption of Energy and Transportation. His work focuses on clean energy, entrepreneurship and market disruption of the world’s major industries, such as energy, transportation, infrastructure, finance and manufacturing.

Yea, it’s a lot, but luckily he summarized it all in his presentation to kick off Intersolar. He makes the case that energy storage, EVs, ride-sharing and autonomous vehicles are on a path to converge very soon, and that the convergence of technology and business models in such a way is always the heart of true disruption.

“Every single technology has been adopted as an S curve. It is never a line,” Seba said. Consider the fact that cars replaced the horse and buggy in a mere 10-year span – and that’s in the days of, well, horse and buggy. His research shows how the tipping point for disruption has always led to a sharp S-curve trajectory, which is only getting sharper in our current time. “S curves are accelerating. It takes months or a year or two. More like J curves now. But yet there are still just straight lines in projections.”

Fast forwarding to the end scenario he lays out (which he originally laid out four years ago, and is right on track) is a world with little to no car ownership because of how much more economic sense it will make to “Uber” everywhere via fleets of automated ride services. This scenario upends much of our modern infrastructure — an abundance of storage on the grid, no use for parking lots, etc. I can’t really do it justice, so I’d recommend watching the full presentation for way more details.

The takeaway I’d like to highlight for the solar industry though is how winners of a disruption are rarely incumbents. Seba points to Kodak as a quick example. Kodak invented digital photography, had its best year ever, and then was basically out of business in under 10 years. Yes, despite that constant steep S curve, projection systems and experts and thought leaders are never prepared when that disruption hits. Companies you’ve never heard of are already ramping up to own the automated driving fleet space and random companies like Dyson are taking educated stabs in the dark at launching their own line of EVs.

For clean energy, the technology and economics are already there, it’s just a matter of a few other chess pieces moving into place, or dots connecting, or whatever other game analogy you’d like to use. If you smell what Seba is cooking, make your plans for this new world now.

2. You should try and win this funding competition.

Intersolar 2018 coverage (42)

Did that disruption talk get you excited, or get the gears turning on the next big idea? Well, hurry and tell the Department of Energy about it and you might get hooked up with a network of people to help implement it, along with some cash.

The DOE’s American Made Challenge Solar Prize competition is awarding $3 million in prizes as well as support from the DOE’s U.S,-based network to help grow, build business plans, prototypes and funding sources for labs and innovators. Additional cash prizes are then awarded to the most viable concepts.

“What role does DOE want to have? To focus on early stage research and forge strong partnerships with the private sector,” said Elaine Ulrich, Senior Advisor, Solar Energy Technologies Office, Energy Efficiency and Renewable Energy, Department of Energy. “We know this is the cornerstone of our success, so a new way we speed innovation is through prize competitions.”

And speed it, it does. This isn’t a laborious grant application process, but a series of contests. Record a 90 second video with a strong pitch and answer four questions: What’s the problem? What’s the solution? Who is on the team? What’s the plan?

The field will be winnowed to about 20 to 40 winners (for a max of $50,000 each) to about 12 after the proof of concept stage (an and additional $200,000 possible), until finally two winners will emerge with $500,000 to launch company.

“Within six months, you could have $750,000 in cash and $150,000 in facility vouchers and tapped into a full network,” Ulrich said. “This is just the first, of hopefully many of these contests.”

Oct. 5 is the submission deadline.

3. Yes, there is still new ground to break in ground-mounted solar.

We saw and heard about several design changes in ground-mounted solar that can forge new paths in underserved segments or take over/grow established segments. We can’t talk about all of them right now (stay tuned for Solar Power International), but here are a few to note.

AP Alternatives Ready Rack

AP Alternatives Ready Rack.

AP Alternatives‘ Ready Rack mounting hardware is designed for both large utility-scale projects and small commercial projects. The small helical anchors and quick install cross bracing make the simple system robust even for high wind zones.

What we liked: This system is nimbly installed with an attachment that fits on a skid steer, which opens up the 20 to 100-kW market up much more for small solar contractors to grow and scale their business.

Soltec bifacial tracking

Live at the Soltec Bifacial testing facility.

We will have more on this topic in our Sept./Oct. issue, but just know that the industry is very focused on finding true, objective results for bifacial modules deployed in various tracker combinations. The price point on bifacial modules may not make sense for wide deployment just yet, but when it does, highly bankable systems from Soltec and Array Technologies, to name two, will be at the ready. Soltec has built a testing ground and is working with NREL and Black and Veatch to gather a complete data set on the harvest of bifacial modules on solar trackers.

Alion tracker

Alion Energy tracker.

This Alion Energy tracker is definitely not for all sites – it has a very specific value proposition for tough and dusty terrains by incorporating a self-cleaning function. There is a lot of concrete needed to install this system, but you could picture it opening up new sites in remote, harsh desert landscapes because of how often its panels could be cleaned with an automated system that uses much less water and no labor.

4. Solar + storage value is much clearer on both the large and small scale.

SolArk

You’ll want to check out the Sol-Ark inverter.

On the small-scale side, we saw the most efficient solar + storage inverter on the market, and it isn’t from SolarEdge or Tesla but from little-known Sol-Ark. We explain DC transformerless architecture in greater detail in our Sept./Oct. print issue, but the quick story is this inverter is able to maintain an impressively high efficiency – both peak and consistent – in battery and grid tied scenarios.

On the large-scale side, more and more storage is being built into projects. First Solar recently signed a project contract for 150 MW of storage, for example. The key stat came from Joachim Seel, Scientific Engineering Associate at the Electricity Markets and Policy Group, Lawrence Berkeley National Laboratory, U.S.: At least six PPAs this year have featured PV-plus-long-duration storage that do not seem to be priced at a prohibitive premium to PV only.

Oh yeah, that reminds me of one more quote from Seba’s presentation: “At some point soon solar-plus-batteries will be cheaper than transmission,” Seba stated. Insert thinky emoji here.

— Solar Builder magazine

H&H Solar completes largest solar project in Iowa

H&H Solar completed two of their latest solar energy projects in Iowa. For both projects, H&H Solar provided the design, engineering, construction and final installation.

H and H solar projects

The West Dubuque project, now the largest and most powerful solar energy location in Iowa, is a 5 MWdc ground mount installation sitting on a 22 acre parcel utilizing AP-Alternatives Fixed Tilt Ground Mounted Racking, Canadian Solar Modules and Canadian Solar Inverters. In addition to the design, engineering and construction services provided by H&H Solar, the company also handled the procurement and permitting for the project. Because accessibility to the site was a challenge, the construction of 2,000 feet of service roads was required for a successful installation.

Officially named the Port of Dubuque Solar Garden, the second project’s 1.2 MW capacity is located on a 5 acre parcel that was originally an industrial site which created a litany of problems and challenges.

According to Dave Garner, Project Developer for H&H Solar, “This was an extremely challenging project, not because of its scope, but because it was an industrial site located adjacent to downtown Dubuque. Thoughtful consideration by our engineers and designers was required to workaround factors of density, bike and pedestrian paths, and ornamental fencing, for instance, and these types of issues aren’t necessarily what we deal with in many other solar projects we design and construct.”

2017 Solar Builder Project of the Year Winners

The Port of Dubuque Solar Garden features ground-mounted, fixed tilt ballasted racking from Solar Flex and Solar Modules and Inverters from Canadian Solar. The installation provides power to the grid at 13.8 kV and features a Learning Center that offers information about the site to the public.

Combined, these two projects are expected to power 850 homes from their 19,160 panels that rest on a total of 27 acres. These sites will be the catalyst for additional solar projects throughout Iowa which has traditionally relied on wind energy as their primary source for alternative energy.

— Solar Builder magazine

Mounting Pressure: Today’s large-scale PV boom demands new levels of service from racking companies

Solar FlexRack

For the first time ever, in 2016, U.S. solar ranked as the No. 1 source of new electric generating capacity additions on an annual basis. In total, solar accounted for 39 percent of new capacity additions across all fuel types, and these big numbers are coming via big installs as the utility-scale segment grew 145 percent from 2015.

“In a banner year for U.S. solar, a record 22 states each added more than 100 MW,” says Cory Honeyman, GTM Research’s associate director of U.S. solar research. “While U.S. solar grew across all segments, what stands out is the double-digit gigawatt boom in utility-scale solar, primarily due to solar’s cost competitiveness with natural gas alternatives.”

The trend shows no signs of reversing, and as utility-scale solar projects continue to boom, the industry demand for material and logistical services will keep increasing pressure on suppliers like never before.

Raw materials bottleneck

“It’s a simple matter of supply and demand,” says Chuck Galbreath, VP of supply chain at SunLink. “If I have more time, I can find more options and drive down costs. When schedules are compressed and I’m forced into a tight delivery window, I have to go with the supplier who is able to deliver in the time allotted, which allows less room for negotiation.”

Others agree: “We often encounter requests for expedited finished product that can be more aggressive than the lead times from the steel mills. For our proprietary racking systems, OMCO is now maintaining a responsible level of steel inventory to support these instances,” states Todd Owen, General Manager of OMCO Solar.

The time pinch has led to more in-house manufacturing. “The top five racking manufacturers have reached economies of scale where additional volume no longer decreases price, forcing manufacturers to vertically integrate by producing more parts and material in-house,” says Paul Benvie, VP of engineering at TerraSmart.

Because the sector is so dependent upon the steel market, finished product pricing can be volatile. The recent anti-dumping lawsuits spurred market increases that were felt in all steel industries, including solar. Benvie says TerraSmart has countered the pricing roller coaster by making strategic hedge buys and leaning on suppliers to honor and hold pricing so they are capable of manufacturing product at a reliable price point.

To help combat delivery delays, more mounting companies also are establishing regional centers. “Steel delivered to and from opposite coasts can have a significant impact on costs and schedules,” Benvie says. “Strategic manufacturers have set up facilities that are centrally located and/or have different branches at opposite ends of the country. For example, TerraSmart has opened a new manufacturing facility in Columbus, Ohio, and can manufacture identical parts out of the Southeast, Southwest and New England.”

RELATED: We look at the value decentralized tracker systems bring to a project 

Timelines keep shrinking

“As the solar industry matures and adopts the more typical rigid large-scale construction approach to project schedules, timelines have been compressed and suppliers are now expected to adhere to strict, tight daily schedules,” says Nick Troia, VP of corporate quality and project management at SunLink. “It is a more professional atmosphere that in some cases is straining the less sophisticated suppliers.”

The compression is substantial: “We ask customers for a 12-week lead time, but in this market we are lucky if we get eight,” says Larry Reeves, a project manager for Array Technologies Inc. (ATI). “Schedules are crazy now.”

Seasonal variations also intensify weather constraints. “The solar industry is challenging, as many financiers, developers and EPCs push to close projects out in Q4,” Benvie says. “In New England, this can be increasingly challenging with projects kicking off as the daylight hours get shorter, temperatures drop and field conditions deteriorate.”

“Without getting into the dollars and cents, delays can be very costly, such as the triggering of liquidated damages that could accumulate at thousands of dollars per day or by hindering project completion for a tax credit deadline,” observes Troia.

Losses can be the cost of customer maintenance, too. In some of these unavoidable situations, someone involved in the project has to recognize and proactively eliminate a delay before it happens.

“We believe we are truly partners with our clients, so we commonly shoulder costs or increase productivity to minimize the sting of a delay, regardless of who caused it,” Benvie says.

Next, we look at the turnkey services and systems designed for saving time on project development.

— Solar Builder magazine