Breastshot Waterwheel & Heat – Project Case Study

5.2m breastshot waterwheel

A mid‑to‑late 19th‑century breastshot waterwheel in rural Oxfordshire is being restored and upgraded to provide continuous renewable heat for an attached property.

The wheel, originally part of a corn mill, had seized and remained stationary for many years. Rather than preserving it as a static heritage feature, the owner has chosen to return it to productive use — not for electricity generation, but for direct mechanical‑to‑thermal conversion (a shaft‑driven heat generator rather than an electrical generator).

This project is part of Rotaheat’s programme to support the adaption of heritage and modern water‑power assets for low‑carbon heat. While this installation is in the UK, the principles apply to mills across Europe and other regions where functional hydraulic infrastructure remains under‑utilised.

Project Objectives

• Restore the wheel to reliable 24/7 mechanical operation
• Maintain historic integrity wherever possible
• Deliver approximately 10kW of sustained thermal output
• Achieve a levelised cost of heat below 2p/kWh
• Reduce carbon intensity to under 1 g CO₂/kWh

For context, conventional gas heating typically carries a carbon intensity in the region of 180–200g CO₂/kWh.

Background: Initial Wheel Release (Early 2026)

Waterwheel, prior to work commencing

When first documented in late 2025, the 5.2‑metre wheel was fully seized, with steel piling jammed into the buckets to prevent rotation. Teme Valley Heritage Engineers led the first phase of work, completed in early 2026, focused solely on:

• freeing the seized wheel using traditional millwrighting methods
• returning the wheel to rotation for the first time in many years

This preparatory work provided the foundation for the structural and mechanical upgrades that followed.  With the assurance that the waterwheel could reliably rotate, the project moved into strengthening the surrounding structure and preparing the drivetrain for continuous operation.

Structural Repairs and Mechanical Preparation (April 2026)

With the waterwheel turning again, April 2026 saw a coordinated programme of structural and mechanical work to stabilise the installation and prepare the drivetrain for continuous 24/7 operation:

• Repair of a fractured spoke on one of the steel rims
• Brickwork repairs within the wheel pit to restore structural integrity
• Machining and installation of a new stub shaft on the original wheel shaft
• Installation of a precision‑engineered steel base platform over the original stone plinth
• Fitting of new SKF Cooper split bearings to support continuous rotation
• Installation of a high‑capacity flexible coupling, rated for up to 13,000 Nm of torque, to safely transfer mechanical power to the heat subsystem
• General mechanical preparation, including checking alignment, for sustained operation under load

These upgrades formed the complete mechanical interface between the historic wheel and the modern heat‑generation equipment. Together, the new stub shaft, bearings, baseplate and flexible coupling form the mechanical interface that will transfer power from the wheel to the heat‑generation equipment.  These works collectively mark the transition from heritage restoration to controlled mechanical power delivery suitable for renewable heat generation.

Fitting new stub shaft

Dry-fit of new steel baseplate over existing stone plinth

Fitting of new bearing and plinth to waterwheel

Next Steps: Heat Subsystem Installation and Automated Flow Control

With the mechanical interface now complete, the project is ready to integrate the heat‑generation subsystem.  Beginning next week, work will start to install and couple Rotaheat’s heat-generation subsystem to the waterwheel. This will allow the wheel’s mechanical power to be converted directly into thermal energy via a shaft‑driven heat generator.

Following this, the project will move to automating the control gate, enabling the system to regulate water flow and mechanical power output in response to:

• river flow conditions
• required thermal output
• protection limits for the waterwheel and heat generator

Automation is essential for stable heat production, equipment protection, and unattended 24/7 operation.

Why Waterwheels for Heat?

Many historic mills retain viable hydraulic infrastructure but lack an economically compelling route back into use. Direct heat generation offers clear advantages:

• no grid connection constraints,
• no reliance on export tariffs,
• low conversion losses,
• very low operating costs and
• near‑zero operational carbon intensity.

This project shows how heritage hydro assets can materially reduce heating costs while supporting local decarbonisation goals.

Follow the Project

Further updates — including heat‑generator installation, commissioning results and measured performance data — will be published as each milestone is reached.

If you own or manage a site with an existing waterwheel or hydro turbine and are exploring options to reduce heating costs, we would welcome a conversation.