The frost heave challenge in solar installations
From pv magazine USA
Frost heave is one of the most common concerns in the Midwest and especially in Illinois, which is prone to frost heave due to the combination of bitter winters and one-of-a-kind soil composition.
Because frost heave is the process of soil expanding after it absorbs water and then freezes, Illinois and other states with periods of sub-zero temperatures for prolonged periods of time are especially vulnerable. It’s not possible to completely prevent the physics of frost heave, but it is possible to prevent these physics from wreaking havoc on solar sites even in the depths of winter.
Nearly all soils can heave, but certain soils are more susceptible than others, such as varied clays and other fine grained branded sediments common in Illinois. It’s also important to understand the rate at which soil can heave, dictated by its grain size, structure, permeability, and capillary flow. Illinois sites frequently have more than one type of soil on the same site, and design and installation need to be adapted accordingly.
Installations in Illinois can be tricky. The Midwest tends to have loose topsoil, but it can still be hiding boulders, bedrock, and cobble, even if it’s been used for agriculture for years. The depth of frost also significantly impacts foundation design, and Illinois winters can generate frost depth of more than five feet. Developers are faced with all of these considerations on top of variations in slope and undulating terrain.
Most vulnerable sites
A common mistake in weather mitigation is focusing on one piece of a timeline. Sites can be vulnerable from the planning stages to years post-operation.
In the planning process: Before a site is developed, failing to adequately assess soil or topography or making incorrect assumptions about frost depths or snow accumulation can create vulnerabilities.
During installation: Refusals occur if a pile takes longer than five minutes to install or doesn’t advance 12 inches within 30 seconds. During installation, conditions that lead to frost heave can also lead to refusal risk, which in turn leads to project delays and budget escalation.
Over time: Even if a site operates successfully and without incident for a year, it can still be vulnerable to frost heave over time. Ice lens growth can cause soil to freeze to foundations, a process known as adfreezing, and create an upward heaving force. If a site wasn’t developed with the variety of unique site conditions in mind, frost jacking may happen years after installation.
How to frost heave-proof a site
Giving frost heave the heave-ho entails a one-of-a-kind approach to every site, following these steps:
Assess the site: Even though silt is a common soil across Illinois, there may be other soils mixed in adding complexity to a site. Developers and EPCs can protect a site by reviewing a report of soil properties and refusal risk estimates. In other words, decision makers need to accurately perform pull tests at multiple spots on the site and extensive geotechnical assessments before moving on to installation.
Build a strong foundation: If a developer and/or EPC selects a foundation before choosing a racking partner, they may miss critical assessments, such as subterranean issues that inform the right foundation options. One of the biggest foundation questions in any site planning process is piles vs. ground screws. Ground screws are uniquely suited to deep freezing regions, are usually more cost effective and faster to install, and ensure the best long-term reliability. Still, there may be unusual conditions that make piles a better choice. A racking partner can offer a break-even analysis to help determine the best site approach.
Prepare for snow load: The majority of frost heave considerations are focused on what’s happening in the ground, but preparing for snow load is also important. Racking that’s not designed to withstand snow load can weaken foundations, increase costs, reduce productivity, and decrease longevity. Snow load preparation may include module tilt, higher module front edge height, reinforced material, and an individual table-based design approach.
What to ask
With all this in mind, developers can protect their sites by asking a partner these questions about their expertise and experience.
Frost Heave
Where do you get your adfreeze and frost depth values?
How do you calculate frost heave loads and forces?
What’s your process of performing soil analysis?
Have you worked on sites that have experienced frost heave, and if so, how have they performed in the long term?
Snow loads
How do you calculate snow loads for a project?
What’s the heaviest snow load you have installed?
How do you track the weather? Do you have trackers with snow sensors and snow shed features?
Topography
What slope tolerance can you accommodate?
What slope tolerance have you installed in?
Is your racking adjustable during installation?
Installation
How many foundations do you plan to install per day, and what is the basis for that assumption?
Have you accounted for refusal risks and costs during the planning phase? How did you arrive at these results?
Where have you installed projects? What’s your familiarity with the regional and local specifics?
What are the steps you take to make installations more predictable so costs and timelines don’t escalate?
Customized/OEM/ODM Service
HomSolar Supports Lifepo4 battery pack customization/OEM/ODM service, welcome to contact us and tell us your needs.
HomSolar: Your One-stop LiFePO4 Battery Pack & ESS Solution Manufacturer
Our line of LiFePO4 (LFP) batteries offer a solution to demanding applications that require a lighter weight, longer life, and higher capacity battery. Features include advanced battery management systems (BMS), Bluetooth® communication and active intelligent monitoring.
Customised Lithium Iron Phosphate Battery Casing
ABS plastic housing, aluminium housing, stainless steel housing and iron housing are available, and can also be designed and customised according to your needs.
HomSolar Smart BMS
Intelligent Battery Management System for HomSolar Energy Storage System. Bluetooth, temperature sensor, LCD display, CAN interface, UART interface also available.
Terminals & Plugs Can Be Customized
A wide range of terminals and plugs can be customised to suit the application needs of your battery products.
Well-designed Solutions for Energy Storage Systems
We will design the perfect energy storage system solution according to your needs, so that you can easily solve the specific industry applications of battery products.
About Our Battery Cells
Our energy storage system products use brand new grade A LiFePO4 cells with a battery lifespan of more than 4,000 charge/discharge cycles.
Applications in Different Industries
We supply customized & OEM battery pack, assemble cells with wiring, fuse and plastic cover, all the cell wires connected to PCB plug or built BMS.
Applications: E-bike, Electric Scooter, Golf Carts, RV, Electric Wheelchair, Electric Tools, Robot Cleaner, Robot Sweeper, Solar Energy Storage System, Emergency Light, Solar Power Light, Medical Equipment, UPS Backup Power Supply.
We can provide you with customized services. We have the ability to provide a vertical supply chain, from single cells to pack/module and to a complete power solution with BMS, etc.
HomSolar (Shenzhen) Technology Co., Ltd
