Building a ground-mount solar racking system in cold environments requires contending with the challenges of frost and snow. The harsh conditions introduce challenges for cold weather solar racking systems, such as foundations lifting out of the ground, that need to be considered at the design phase. When designing systems for cold weather climates, it is essential to treat foundations as an interconnected system, instead of as individual components. In this post, we will discuss the key design considerations for designing solar racking in Canada under cold weather conditions.
Solar Racking Canada:
Impact of Frost and Permafrost
When we design projects for solar racking in Western Canada the key cold-weather considerations are related to the subsurface condition and the presence of water.
Frost uplift or frost heave caused by expansion of water in the pores of the soil is the main concern of designing cold weather solar racking. Not all cold climates present issues with frost uplift – it will only happen when building in frost-susceptible soils with water present. Even among sites with frost susceptible soils, there is a varying degree of severity.
Permafrost is a unique subsurface condition seen in colder northern climates, including Canada. As a result, engineers with expertise in extreme cold weather design of ground-mount solar racking in Canada are not common. The main challenge with permafrost is discontinuous permafrost, which is when the permafrost has unfrozen layers within it, allowing water to move between layers and cause instability.
In addition to concerns around cold weather conditions affecting solar panel racking in Canada, wiring and cables can also be affected. There is a risk of ice hanging from wires and snow pulling out wiring without the proper DC cable management. There should not be a reliance on zip ties or cable clips, as these are not robust enough to combat ice and snow long-term.
Managing Shorter Construction Timeframe
In harsher cold seasons construction crews are limited to shorter seasonal windows to complete installation. If installation needs to be pushed into months with dropping temperatures and heavier snowfall, there will be an increase in labor costs due to needing to clear the site of snow and labor requirements under cold weather. Trenching also cannot be done in the snow.
Many developers elect to delay any remaining installation until the spring, which then delays revenue from the project and may incur additional costs. Therefore, it is essential that the cold weather conditions are taken into consideration from the start so that any risks can be factored into the construction timeline.
Cold Weather Solar Racking Systems:
Fixed-Tilt and Single-Axis
There are two main types of solar racking systems that will work in cold weather environments with heavy snow: fixed-tilt and single-axis trackers. When considering using single-axis trackers the added generation needs to be weighed against the higher cost compared to fixed-tilt trackers. Generally, the more north you go, a fixed-tilt tracker is the most financially feasible choice.
In extremely cold temperatures, there is a high risk of issues rising with trackers given their safe mode settings to protect the panels and racking functionality. Safe modes are triggered when wind speed hits a certain point that could cause damage. There are also sensors that use algorithms to predict whether it is going to snow and upon hitting several thresholds the tracker will put itself in the vertical position to safeguard the system from snow.
In addition, the sensors and electronics monitoring the functioning of the single-axis trackers are vulnerable to failure in extremely cold temperatures.
In some cases, there can be competing safe modes triggered. For example, in the Prairies where there is both high wind and snow, winds could prompt the sensor to flatten the panels, thus causing more snow accumulation than would happen with a fixed-tilt system.
Fort Chipewyan Solar Project:
A Case Study in Alberta
The Fort Chipewyan solar project is an example of a successfully designed and engineered solar project in the frost-susceptible region of Western Canada.
Fort Chipewyan, a remote community of 1,000 indigenous people in Northern Alberta, Polar Racking is providing the ground-mount solar racking system for what will soon be home to the largest off-grid solar and storage farm in both Alberta and Canada. Together with a 600 kilowatt (kW) solar project completed in 2019, the 2,200 kW project will help reduce reliance on the costly, polluting diesel fuel the community was using to power its homes and facilities.
These solar projects will supply over 25 percent of the community’s power.
A successful commercial or utility-scale ground-mount solar project in cold environments begins with assessing the degree of risk frost, permafrost, snow accumulation, and high winds pose to the system. A system must be designed with these factors in mind to optimize long-term performance and minimize O&M costs.
