Cutting the concrete and steel used in its battery storage facilities has enabled Statera Energy to reduce its carbon footprint.
One of the biggest factors holding back the transition to 100% renewable energy is that the output from the two most used sources – the sun and wind – isn’t continuous.
This makes matching supply and demand a challenge.
On one hand, when it’s not sunny or windy but demand for electricity is high, more carbon-intensive sources of energy, such as fossil fuels, still have to be used to top up the supply.
On the other hand, solar and wind farms can be highly productive during periods of low demand, meaning that some of their output can be wasted.
The solution is to efficiently store the excess renewable energy generated whenever supply exceeds demand, so that this can be released when the situation is reversed.
Although several storage technologies are being developed, lithium-ion rechargeable batteries remain the most viable option, according to National Grid.
Opportunities to cut carbon emissions
Statera Energy operates in this market, owning and running battery energy storage systems (Bess) at a growing number of sites around the UK.
The firm was keen to determine whether the construction of these facilities could be optimised to reduce their carbon footprints. It also wanted to make the whole building process more efficient.
Statera’s Bess facilities house the batteries in specially designed shipping containers.
The delivery weight of these containers is restricted by law on UK roads. As such, they arrive empty and the batteries are installed onsite, bringing the weight of each one up to 50t.
A foundational problem
The industry-standard method of supporting a container is to cast a reinforced concrete slab as a foundation and then install precast plinths. This spreads the load beyond the footprint to minimise settlement.
Each slab is typically reinforced with A393 steel mesh. Given that steelmaking is a major source of global carbon dioxide emissions, Statera wanted to see whether there was scope for reducing the total embodied carbon of these structures.
It worked with its Bess supplier and civil engineering designer to define requirements for lower-carbon container foundations.
These were to be built at a site next to its existing battery storage facility near the Wiltshire village of Minety. The facility had entered service in early 2022.
An innovative solution
The design solution was to replace the standard raft slab with 10 individual plinth foundations for each container.
These square-section plinths were built by pouring a 60cm-deep mass concrete base and topping them with 45cm precast concrete units to set the container at the right level for cabling and drainage.
Building individual plinths runs a higher risk of one area of the foundations settling more or faster than others, in comparison with using the standard raft design. But it uses significantly less concrete – which is also carbon-intensive, mainly because of its cement content.
And, since the bases don’t need mesh reinforcement, all of the embodied carbon from that steel is eliminated.
The mass-poured bases also remove the need for formwork (temporary or permanent moulds), enabling Statera’s construction partner to further cut the amount of material, traffic and time onsite.
Reducing risk
The designers considered the ground conditions and calculated that the 1m x 1m plan dimensions of the mass concrete bases would limit the risk of settlement.
The total settlement of the foundation is less of a concern.
This risk is already mitigated in the cabling design, which enables the cables to move without applying stress to their endings.
Scaling up the carbon savings
Statera used the same design approach to support the containers housing the system that converts the low-voltage direct current from the Bess units to high-voltage alternating current for export to the grid.
The firm also adopted a plinth design to support the control room at the site as an alternative to tanked basement foundations.
The facility, known as Minety South Storage 2, is made up of 30 containers, offering a maximum output of 50MW.
Statera reduced the amount of concrete in the foundations here by 16%. It also eliminated the reinforcing steel and made other savings on materials.
As the firm continues to expand its facilities, these gains will build up.
Minety South Storage 2 entered commercial operations in the summer of 2022.
Since then, Statera has applied the same design approach to seven further projects, preventing an estimated 470t of CO2e from entering the atmosphere to date.
Other decarbonisation options for future projects could include the use of lower-carbon cement or steel and the careful selection of new Bess sites to minimise delivery mileage.
Name of project:
Minety South Storage 2
Project team members:
- Sina Atabak, Statera Energy
- Jeremy Collins, GGP Consult
- Charlie Gomer, Statera Energy
- Simon Johnson, Statera Energy
- Jon Lee, GGP Consult
- Evangelos Pastras, Statera Energy (now at DNV)
- Jason Tilley, ByrneLooby (now at Geo-Environmental Services)
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