The storage elements (CSM-panels) within the compact storage unit are filled with a latent heat storage material, the Phase Change Material (PCM). PCM uses the latent heat during the phase change from solid to liquid or from liquid to solid (see graph).

Using a latent heat storage unit makes sense if a minimum of 50 % of the storage unit's volume is filled with PCM and if the working temperature difference is maximally 15-20K.

2.  Technology

2.2 Compact storage unit

In addition to the wide-spread use of CSM based devices specifically designed for the respective buildings (see examples under 3) we are currently advancing the development

of complete heat-/cold storage units for use in existing and newly developed

air conditioning systems.

The compact storage unit holds 50 CSM panels 5/10 with a maximal storage capacity of 4000Wh. The extended version contains 100 panels with up to 8000Wh. Because of the modular construction of the unit it is possible to extend it in steps of +4000Wh.

In the housing the CSM panels are placed at a defined distance of 5 mm on a twin rail system.

Casing

The storage casing is assembled from modular EPP components. EPP is a solid

elastic foam with a closed-cell surface. The advantages of this housing are:

-         low weight

-         good insulation against warmth and cold

-         high absorption of kinetic energy (also in case of multiple impacts)

-         good dimensional stability and resilience against static and dynamic strains

-         good resistance to chemicals

-         easy to disinfect because of the closed surface pores

Recommend air flow:               230 – 420 m³/ h

The total heat transfer area is 12,04 m² (50 panels x 2 sides x 0,43m x 0,28m).

To handle higher air flow rates it is recommended to use additional compact storage

units in parallel to increase the system capacity.

Example:

At a volume stream of 310 m³/h and a cross section of 0,0014 m² (0,005m x 0,28) per gap

between the panels this corresponds to a stream velocity of 2,37 m/s. This ensures an optimal heat transfer between air stream and panel.

3.  References

3.1 Main tropical greenhouse – Botanical Garden Berlin

The two towers of the air circulation system have been specifically designed as giant jungle trees to blend in with the tropical plants surrounding them. Their purpose is to guarantee an optimal temperature distribution in the greenhouse. Inside the tower our CSM panels with a special PCM operating at 25°C are installed. They temporarily store “heat” or “cold”.

During the day the air at the roof of the greenhouse heats up quickly. An extractor fan at the top of the tower draws in this air and transports it down to the plants. On the way down the excess heat is absorbed from the air stream and stored in the CSM, with “cooled” air arriving to the plants. During the night cool air is taken from the roof area, heats up on the way down and arrives warmed up at the plant level.

Both cooling & heating are accomplished using only a small electrical fan, thus saving fossil fuels, carbon dioxide and costs whilst considerably smoothing the temperature profile!

For further informations, please take a look on our Video.

Click here.

The technical details are the following:

Volume air stream              :           7.500 m³/h

Pressure drop Δp               :           50 Pa

Connected power (el. fan)    :           1,1 kW

Storage capacity                :           110 kWh / cycle (8 h/d)

PCM – mass                      :           ca. 3000 kg

Estimated saved thermal energy over approximately 200 days (= 200 cycles):

ca. 22.000 KWh/a (corresponds the savings of 5to CO²)

Example of measurement report:

Heat pumps for an industrial production hall

The system consists of two heat pumps with a total volume flow of 4000 m³/h, solar thermal collectors and 6 compact storage units. Each contains 100 CSM modules. The RT12 PCM inside, has a storage capacity of around 26 KWh for the low temperature months where it stores the heat of day for use in the night. This leads to an efficiency increase of the heat pumps whilst also decreasing the peak loads.