Keeping battery storage cool with uninsulated PP-R

Location	Scotland
Product	PP-R
Installer	A.Alexander & Son (Electrical) Ltd
Year	2026 (case study released)

Windfarm battery storage kept cool with pipework chilling system

From the opening of the first commercial farm to contribute to the National Grid in 1991, wind now accounts for around a third of the country’s annual electricity supply.[1]

But while astonishing progress has been made, new obstacles have arisen, especially around the storage of electricity. This was the situation facing one of Scotland’s leading windfarms, where batteries for storing turbine-generated power for future use were vulnerable to overheating, necessitating innovative use of REHAU pipework to create a first-of-its-kind cooling system.

Wind power is now the UK’s leading renewable energy source and represents a great British success story. But intermittency has long been a concern, with questions arising about how this power can be stored for periods of lower energy generation. The answer revolves around battery energy storage system (BESS) technologies, which stabilise wind power output to support the National Grid.

Consequently, it is increasingly standard practice for lithium-ion batteries to be installed on-site at windfarms in dedicated facilities. Yet with the pressure to make as much use of a building’s footprint as possible, these BESS solutions are often densely packed together into tight spaces, leading to overheating risks and subsequent health and safety concerns.

Keeping Precision Cooling

This was the issue facing one of Scotland’s largest windfarms. With precise cooling and heating needed to maintain optimum operational conditions, a pipework system was needed to deliver chilled and low-temperature hot water (LTHW) to the BESS facility adjacent to the farm. Given the tight spacing and space constraints the pipework needed to be easy to handle.

A.Alexander & Son (Electrical) Ltd, a Glasgow based Mechanical and Electrical contractor, was engaged to meet this challenging brief. The specification called for two air-cooled chillers with free-cooling capability to supply water at 15°C to a set of two buffer vessels. These vessels would maintain a mean water temperature of 18°C, with a design delta of 6°C (21°C return).

From these buffers, five header circuits would distribute chilled water to the battery racks. Each rack required a constant flow of 0.75 litres per second at 18°C (±3°C), with accompanying inlets, outlets and isolating valves. Finally, the system needed reversible heat pumps as part of a dedicated closed heating system that would provide LTHW up to 40°C to an additional two buffer vessels with a design delta of 5°C.

A First-of-its-Kind Challenge

All of this had to be achieved within a building where every millimetre mattered. As described by Bernard Diamond, Director at A. Alexander & Son (Electrical) Ltd: “The density of the battery racks presented a major challenge for our team. Structural constraints meant there was almost no spare space, which lead to Alexandra from the REHAU team being enlisted to support redesigning areas to ensure the installation was possible and would offer the required performance.”

The design team behind the system had already selected REHAU as the pipework supplier to be used throughout. For A. Alexander & Son, this was good news, as they had previously worked with the polymer solutions supplier on earlier projects. However, these works had involved burying pipework underground for conventional plumbing and heating applications. By contrast, this project would involve working above ground in uniquely challenging circumstances.

“This particular project was not just about being able to supply pipework in certain sizes,” Bernard continues. “It was about engineering a system that could meet very specific hydraulic requirements while fitting around complicated routes. This meant we literally had to consider all angles when looking at how everything would connect.

“This involved a long list of considerations, including component redesigns, sizing adjustments, and adapting to work with non-standard bends and tees to fit in challenging spaces and pinch points. On top of this flexibility, everything needed to be easy to fit, as welding and hot works simply weren’t possible in these confined spaces. We found the only way to achieve this was to pre-fabricate in an onsite workshop compound and using two teams, one to fabricate and one to install.”

Making It Fit

Customised, smaller versions of REHAU’s PP-R pipework solution were fabricated for use in the chilled and LTHW circuits, with 5.8m-length pipes ranging between SDR 11 and 17.6 in 40-250mm diameter used for both the chilled and LTHW circuits. These were accompanied by elbow, tee, reducer, header connector, flange and flange adaptor fittings similarly sized down to suit the site-specific requirements.

REHAU’s calculations confirmed that even under a worst-case 20°C differential, pipework expansion would not exceed 15mm, meaning it could be easily absorbed by existing elbows and bending arms without additional, space-consuming expansion loops.

The pipework’s lightweight, flexible construction also proved invaluable to working to the complex design of the project. With weights ranging from just 0.438kg to 10.965kg per metre, A. Alexander & Son’s team could more easily manoeuvre and bend lengths within the battery hall’s confined spaces.

Getting Beyond the Pipework

REHAU’s role extended beyond fabrication and supply. It also advised on flow rates and delivered training that gave the A. Alexander & Son team, the confidence to install the required cooling and LTHW system in such demanding conditions.

“From the outset, we knew this project would test our design and delivery offering,” said Kenny Boyle, Sales Manager for REHAU Building Solutions. “As a first-of-its-kind project for REHAU, ongoing collaboration between the technical, planning and sales teams at REHAU and A. Alexander & Son’s team was key to mitigating potential issues during the system’s construction and subsequent operation.

“Alongside this, REHAU pipework needed to be integrated alongside other components A. Alexander & Son’s team were using during this project. Despite these challenges, we were able to help deliver a functional and effective system that could provide the LTHW and cold water the BESS facility needed to harness energy from adjacent turbines.”

Setting Future Standards

On commissioning, the system achieved its demanding specification with chilled water flowing to every rack with operators able to adjust flow and temperature, while the reversible heat pumps provided LTHW support to allow for a further degree of control. Despite the degree of difficulty on the project, the installation was completed successfully as a functional prototype that can provide valuable learning for future full-scale deployment across other windfarms.

“Once our team had received training and routing and sizing was agreed, the project progressed at a steady pace,” said Bernard. “The PP-R pipework provided delivered on what was promised – light to lift, and the modularity was ideal for confined spaces in comparison to traditional jointing and pipework”.

“Reliability is crucial on a project of this complexity, from product delivery to component integrity and performance. REHAU delivered on these criteria, and our partnership was invaluable to completing this project successfully.”

“Projects like this show the real value of collaboration,” Kenny concluded. “Given the spatial challenges of working within the battery hall, this was a triumph of design, good planning, and being present to provide support when it matters most.

“The end result is clear for all to see – a system and concept that keeps batteries cool and could be a lynchpin in future energy storage projects at windfarms, data centres and beyond. We’re proud to have played our part in making it happen.”

[1] https://reports.electricinsights.co.uk/wp-content/uploads/2024/09/240902_Drax_24Q2_2024.pdf