To test different materials as insulation materials for BILS, we are setting up an insulation test rig. Not only the thermal conductivity of the material is relevant, but also the behaviour under water.
Insulation test rig.
On one side (left) "the BILS storage", heatable, 100 litres volume in a flexible skin.
On the right side "the lake", kept at a fix temperature. The volume is not relevant. Water currents are simulated using a submerged pumping system.
In between, the possibility to test different potential insulation materials. The idea is to heat up the BILS, observe the behaviour, then measure the time to cool down again.
View from the lake side. The black face is the insulation material to be tested.
A submerged pump is simulating natural currents.
The first experiments in the BILS simulator were more challenging than expected. Side effects such as stratification, adding heat form the pump etc.
Now, in a first series of tests, the insulation properties of different wet materials are compared. The "lake" is kept at 10°C and the "storage" heated up to 60°C. The insulation materials are
- Standard storage insulation, submerged. Most probably still some air enclosed.
- PU open porous filter foam (PPI=20)
- Saturated Superabsorber
all with a thickness of 10cm
The four materials and their thermal losses.
The open porous PU foam is more or less the same as pure water.
The conventional material is much better even when wetted. However it is not clear how much air is still contained. Previous test show that it is virtually not possible to completely wet this material.
The good result is the superabsorber. This material contains about the same amount of water as the pure water insulation. The thermal insulation properties are however much better. This is what we are looking for.