Paybacks could be shorter

Thermal Technology has been involved with supply and application of all forms of air to air energy recovery devices for over 30 years, so we do claim to have a reasonable knowledge of the topic.

The article covers the subject very well, but there does seem to be one glaring omission, the effect that energy recovery devices have on the sizing of other plant.

If an air to air energy device is fitted into an air handling unit, then it acts as a pre-cooling or pre-heating device. This in turn reduces the load on the heater battery (winter) and cooling coil (summer) – this is how energy is saved.

More importantly, it is possible to reduce the capacity of the heater battery and cooling coil by taking into consideration all or some of the energy saved by the device (depending on application). This has various knock-on effects – the pipe and insulation sizes to the coils will be smaller, valve sizes smaller, pump sizes smaller, even the boiler and chiller capacities may be reduced.

To give an example to highlight this point, some years ago we were asked to supply thermal wheels to be fitted in an air conditioning system for a Middle East project. The thermal wheels reduced the cooling load and cooling coil capacities to such an extent that one chiller was deleted, saving more than the cost of the thermal wheels.

I think that the real payback periods are in fact far better than indicated in the article.