Project focus: Taff's Well

Harnessing the heat produced by the historic thermal spring in Taff’s Well is providing low-carbon heating and hot water for two buildings at the heart of the local community.

The project to replace the gas systems at the primary school and the bowls pavilion with a complex and efficient open loop water source system was completed by Kensa on behalf of Rhondda Cynon Taf County Borough Council and is expected to cut carbon emissions from heat by up to 80%.

“We have an ambition to decarbonise the council by 2030 and we understand there is no one solution, so it is important that we look at what heat resources are around or under us,” says Jon Arroyo, energy and carbon reduction manager at the council. “We see our role as exploring alternative solutions to help steer our businesses and residents in their journey towards a net zero future.”

Untapped resource

Taff’s Well, a village just north of Cardiff, is the site of the only natural thermal spring in Wales. The average water temperature is 21.6°C, more than 10 degrees warmer than the average groundwater temperature in Wales, which is just 11.3°C.

The thermal spring is contained within a Grade II-listed brick well structure and building within Taff’s Well Park, which meant that the council had to get consent for any building work from Cadw, the historic environment service of the Welsh Government.

Water source systems are highly efficient because water has a higher heat transfer rate than the ground. The primary school benefits from the high heat capabilities of large-capacity heat pumps, while the bowls pavilion is heated by more compact units.

Grand designs

Kensa, a CIPHE Industrial Associate, designed an open loop system to harness the heat energy provided by the flow of warm water from the spring. Unlike traditional ground source or closed loop water source systems that circulate a heat transfer fluid through pipework to harness the heat, here the water is extracted via a pump and used directly within the system.

After the energy has been transferred to the heat pumps, the cooler water is discharged through the well’s overflow, which emerges several metres to the west of the spring on the eastern bank of the River Taff. The well water has no contact with any other substance, so there is no issue with contamination or pollution. Kensa and the council did need to obtain the appropriate licenses from Natural Resources Wales, though, due to the requirement for water extraction and reinjection.

Open loop systems require filtration and regular maintenance, so to avoid the water freezing at the point of energy transfer in the heat pump, intermediate heat exchangers are used to separate the hot and cold circuits, protecting components from the risk of corrosion.

One for all

Bringing an extra level of complexity to the design, Kensa added the school buildings and bowls pavilion onto a network of shared pipework, into which the warm water from the well is circulated. This shared ground loop array distributes warm water to the heat pumps installed in the separate buildings, avoiding the need for a central plantroom and giving each facility control over its own heating.

The distance between the well house and the school is approximately 360m, a route filled with pipes for existing utilities, as well as mature trees with large root beds. Trenching in the traditional way was virtually impossible, so Kensa horizontally drilled for hundreds of metres between the well, the school and the pavilion.

“The council was keen to utilise the well as it provides an unlimited amount of free renewable energy that was just flowing straight into the River Taff,” explains Matt Zealley, sales manager at Kensa. “The school and bowls pavilion were obvious beneficiaries as they are so close to it.

“The installation of the heat pump system has not only relieved the school and pavilion of its gas dependency, it has reduced the carbon output from its heating systems by around 80%. With the heat pumps producing no emissions or pollution, this scheme will also have had a positive impact on the air quality for the pupils and the local community.”

Successful system

Ground source heat pumps usually source energy from the ground to provide heating and hot water, but the unique installation at Taff’s Well pumps warm water from the spring and passes it through a nearby heat exchanger, which is connected to ground source heat pumps housed inside the school and pavilion.

In this highly efficient system, heat energy stored in the warm spring water is absorbed and converted by the heat pumps into energy for the heating and hot water systems.

While in the system the water is confined to its own pipework, mostly hidden underground and out of sight, to ensure there are no issues with contamination or pollution. After passing through the system, the water empties into the well’s overflow, from where it feeds back into the River Taff.

“We are very excited about how Taff’s Well thermal spring has been utilised for the whole school community,” says Kathryn Price, headteacher of Ffynnon Taf Primary School. “Our Eco Committee thoroughly enjoyed learning more about the heat pump system and how this helps to reduce the school’s carbon footprint. We will continue to celebrate the success of the thermal spring installation in our community for many years to come.”