Waste incineration plant stores waste heat in plastic pipes underground
A Finnish waste incineration plant stores waste heat in GRP pipes underground. It can be retrieved in the winter months and used to heat homes.
The GRP pipes of the storage system before installation. The heat will later be stored underground in the green pipes.
(Image: Exel Composites)
A waste incineration plant in the Finnish city of Salo stores excess heat in around 1.9 km of glass fiber reinforced plastic (GRP) pipes underground. Up to 14 GWh can be temporarily stored in the granite rock beneath the plant and retrieved when needed, according to a press release from Exel Composites, the company involved in the project.
The heat storage concept was developed by the operators of the waste incineration plant together with the composite material manufacturer Exel Composites and the geothermal technology company QHeat.
Durable and heat-insulating pipes
The system consists of GRP pipes that have been specially developed for the underground storage of heat. The pipes are lightweight, corrosion-resistant and have particularly efficient thermal properties. The pipes are the result of a collaboration between Exel Composites and QHeat, which took several attempts to develop the pipes in such a way that they achieve a balance between strength and thermal insulation.
Strength is important so that the pipes can withstand the immense pressure that is exerted on them at their destination in the granite rock. At the same time, however, the thermal insulation must be so good that the waste heat is not released into the rock in order to be energy-efficient. The two companies also developed a concept for assembling the pipes quickly and simplifying their installation.
The heat storage facility, which was completed at the end of July 2025, can store up to 14 GWh of heat generated as a by-product of waste incineration. Around 120,000 municipal waste items are incinerated in the plant every year. Previously, the excess heat was released into the air in summer. The energy from the heat was thus lost. With the new heat storage system, the heat generated by the plant in summer can also be called up in the -20 °C cold Finnish winter.
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The plant operators want to use the energy from the heat storage system to heat 700 single-family homes. This will reduce heat emissions and increase the efficiency of the incineration plant.
(olb)
