Energy Transport

Mobile heat supply independent of supply lines

The system developed under the project facilitates the storage of waste heat generated in a landfill gas plant in a mobile container. This heat is supplied to a local public indoor swimming pool where it is fed into the heating system.

Summary

Initial situation

LaTherm GmbH developed a mobile latent heat accumulator that can store and transport large quantities of heat and introduced this to the market.

LaTherm stores heat produced in cogeneration plants (CHPs) and as a by-product of industrial processes in containers filled with the storage material sodium acetate trihydrate. Lorries transport the heat-filled containers from source to the location at which the heat is to be used. There, LaTherm feeds the heat into the existing heating systems. Water is used to transfer the heat.

The technology applied works on the principle of physically storing the heat within a phase change material (PCM).

The sodium acetate used is a fairly low-cost storage material with a high storage capacity. It is made from acetic acid and sodium hydroxide, which are both generated in large quantities as by-products in the chemical industry.

The patented technology ensures that as the accumulator discharges heat, crystallisation occurs automatically as soon as the phase transition temperature passes 58.5°C.

LaTherm used this method in the pilot project to supply the waste heat generated by the CHP modules in a local landfill gas plant to a city swimming pool in the Brackel district of Dortmund, where it was used to heat the pools. Parts of the process were also optimised at the same time. For example, thermal insulation of the flexible connection pipes was found to be necessary for a significant reduction of the heat losses occurring during both the charging and discharging processes.

Findings

LaTherm supplied approx. 264 MWh of heat per annum to the pools. As this thermal energy was not generated from natural gas, 80t of CO2 were saved each year. If this method were to be integrated fully into the heating system at the swimming baths, it would be possible to save as much as 290t of CO2 per annum.

In all, particulate emissions were lowered in the area of application by the use of the LaTherm system despite the transportation process. Transportation is responsible for less than 3.5% of the CO2 emissions.

Conclusions

The mobile supply of useful heat independent of supply lines represents a new form of energy supply for consumers who are not connected to a local or district heating network.

The method makes it possible to re-use industrial waste heat in a way that is flexible with regard to both time and distance.

The feasibility of the mobile heat concept is of particular interest to the operators of biogas plants in rural areas who do not have a waste heat concept.

Source: Final report

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Source: Environmental library of the Federal Environment Agency (UBA)