How to select geosynthetics for wind farms? As energy demands continue to rise throughout the world, renewable energy projects such as wind farms are taking off both locally and globally.
The 2021 United Nations’ Intergovernmental Report on Climate Change (IPCC) states that “global warming of 1.5°C and 2°C will be exceeded during the 21st century unless deep reductions in carbon dioxide (CO2) and other greenhouse gas emissions occur in the coming decades.”
This and other findings have put more pressure on global leaders to transition to renewables, limiting CO2 emissions from fossil fuel energy and supporting renewable energy solutions such as solar and wind power.
While the groundswell of support for these projects represents a step forward from an environmental perspective, the actual construction of wind energy farms can be a challenge. This is due to a wind farm’s unique requirements, such as the incredible weight of the turbines and the ground strength needed to ensure long-term stability on-site.
So how can renewable energy firms manage the construction phase with the least amount of environmental impact and the best long-term outcomes?
Wind farms have unique requirements
Due to their size and the conditions required to ensure the project’s success, wind energy projects are often located in remote greenfield areas. Many of these locations feature poor soil conditions, weak subgrades and other environmental conditions that can make construction a challenge.
Some common design considerations include:
- Subgrade stabilization and improvement
- Strengthening access and haul roads
- Building working platforms or pads
- Creating foundations that can resist rotational movement
- Slope stabilization in the surrounding area
Wind farms require soil that can support extremely heavy loads. This is not just a factor for the installed turbine, but also, crucially, the access roads on-site. With segments of each turbine weighing up to 55 tons (50 tonnes), and the total assembly often nearing 330 tons (300 tonnes), extreme ground reinforcement is needed to ensure each component can be transported successfully to its destination.
Transporting the wind turbines is a mammoth task: for each turbine, approximately 50 concrete trucks, steel reinforcement, the tower, the blades and the turbine must access the site over the course of a few months.
This puts enormous pressure on the access roads, which are often temporary constructions that must endure short-term, heavy loading and then perform well as a light-duty maintenance road for the remainder of their design life—sometimes up to 50 years.
Using geosynthetics to strengthen and reinforce soft subgrades presents a good solution, with a combination of geotextiles and geogrids with heavy-duty loading often providing a positive outcome. Selecting geosynthetics that offer base reinforcement and subgrade stabilization, such as Secugrid and Combigrid from Global Synthetics means that the project will have high strength at low strain—an absolute necessity for this type of application.
Cost-effective, easy to install and with a long design life, geosynthetics can handle the heavy traffic loading (typically axle loading of around 90 kN) without the need to pave miles of temporary road.
These geogrids possess uniform strength in their welded bars, creating a rigid, stable, two-dimensional grid that is as strong in its longitudinal direction as in its transverse direction.
Secugrid has been successful in a range of wind farm applications including a Tasmanian renewables project involving 31 turbines and 12.4 miles (20 km) of access roads. The successful construction of this 112-MW project resulted in Tasmania achieving its goal of a 30% increase to its renewable energy capacity.
Pads and platforms
Like the access roads, wind turbine pads must be strong enough to support the long-term placement and continual rotation of the giant turbines. Base foundations need to be built on strong and stable soil, otherwise, the foundations can sink and knock the turbine out of alignment with potentially disastrous consequences.
In one case, during a wind farm project in Eaglesham Moor in Scotland, the peat subgrade was collapsing while the base foundations for the pads were being dug.
This region’s soils are extremely challenging for this type of construction, with depths of up to 23 feet (7 m) covered with 10 feet (3 m) of glacial till. Roughly two-thirds of the site is located on these types of soils, which are unable to support conventional concrete gravity foundations for the pads.
Geotechnical issues of turbine pads such as this can be managed through a combination of increasing concrete base sizes, extensive pile work geosynthetic support.
Geosynthetics may not always be the sole solution, however, they are frequently used in conjunction with other methods to achieve a good result for pads and platforms
Which geosynthetics are recommended for wind farms?
Engineered geogrids can often provide a sustainable solution for wind farm construction on soft or challenging soils. Choosing a geogrid like Secugrid can reduce the required thickness of the granular layer for access roads and hardstands, providing considerable cost savings and reduced construction time.
This article originally appeared on the Global Geosynthetics Blog, https://globalsynthetics.com.au/blog.