To grade or not to grade? How SIFT determines optimal layouts for challenging solar sites

Terrasmart Rumford Project
This 6.5 MW Rumford site features precipitous slopes throughout its rocky Maine landscape. Photo via Nexamp and Terrasmart.

We focus a lot on the new structural solutions engineered by solar tracker manufacturers to mitigate challenges from undulating and difficult terrain — shorter torque tubes, ground screw foundations, more robust bearings, and so on. But those tools are only deployed after a thorough site assessment.

Site assessment is another area of crucial innovation in large-scale solar. Traditionally a time- and resource-intensive piece of the solar development puzzle, site assessment often involves third-party civil engineers to perform granular topographical analyses on-site — the more you can understand at the outset will keep construction on time and on budget.

However, keeping site assessment “on budget” can be another story. Oftentimes, developers consider multiple plots of land and hire engineers to evaluate all scenarios. And even after it’s complete, revisions may be required to determine a suitable site plan.

But now there are smarter, faster ways to analyze everything from module procurement value to a site’s topography.

SIFTing through scenarios

SIFT heat map

An example here is Terrasmart’s Solar Instant Feasibility Tool, or SIFT. Terrasmart design engineers use SIFT to help developers and EPCs bring in system design, performance, and financial modeling early in the project cycle. SIFT helps them identify the right racking system and optimize the layout, components, and construction, as well as energy yield, returns, and value. It can streamline slope analysis and optimize site design from the start. It can also iterate multiple cost/benefit scenarios.

For example, SIFT is used to understand when a 2P tracker vs. a 1P tracker is needed to maximize production or minimize land grading and keep construction on track.

Another key to SIFT though — despite it being an assessment tool from a supplier — is the optionality it can provide due to Terrasmart’s portfolio of products and turnkey services. Terrasmart has both pile and ground screw foundations as well as in-house wire management and eBOS solutions. Users can optimize configurations and components, import their own module and inverter data from multiple industry databases, and run IRR and LCOE models.

SIFT has already been applied to 250 GW of potential capacity, helping developers and asset owners extract from 5% to 15% higher returns on their projects by rapidly simulating thousands of different layouts in minutes. Here are some examples:

Rumford Solar Project: Production Yield Advantages

The 6.5 MW Rumford site features precipitous slopes throughout its rocky Maine landscape. But with its 20% grade tolerance and positioning using SIFT on south-facing slopes, TerraTrak 2P has been able to generate 4.3% more energy than Tracker 2 and 4.7% more than Tracker 1.

Looking at the various parameters pertaining to yield, TerraTrak’s advantage in the “no-grade capacity” metric stands out. For this site, TerraTrak delivers a 7.1 MW capacity potential without grading, while the other options offer 5.9 MW and 4.6 MW without grading.

Jay Solar Project: Less grading equals maximum savings

The 7 MW Jay site also presented slope challenges that would have required substantial civil work had the EPC selected Tracker 2 or 3 rather than TerraTrak 2P. In this scenario, TerraTrak’s slope adaptability resulted in 90% to 99% less grading than the alternatives. On this site, a 15% grade tolerance would require moving 25,227 cubic yards of earth; a 10% grade tolerance would have required eight times that amount — 205,932 cubic yards. With TerraTrak 2P, the EPC and its contractors only had to move 1,545 cubic yards of soil.

At an estimated cost of $30 per yard to cut and $20 per yard to fill on this site, TerraTrak delivered huge cost savings to the EPC, the developer, and the asset owner: $567,000 less than Tracker 2, or an $0.08/ Wp difference. Compared to Tracker 3, TerraTrak’s cost saving is an astounding $5.1 million in avoided grading costs, or a $0.08/ Wp cost difference.

Read more about SIFT in this “Navigating Slopes to Gain a Competitive Edge” report.

You can also learn more in this video:

— Solar Builder magazine







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