10.07.2015   EUROSUN 2008

Projects within Subtask C

There were five PCM related projects included in IEA SHC Task 32. A summary of these projects is given in Table 1.

Three projects dealt with macro-encapsulated PCM containers in water stores. All of these projects include the development of TRNSYS models for the PCM stores:

• At Lleida University, Spain, bottles and filled up heat exchangers of PCM material with graphite matrix for the enhancement of the heat conduction and increase of power input/output were tested. Applications are free-cooling and DHW tanks.

• At the University of Applied Sciences Western Switzerland in Yverdon-les-Bains/Switzerland a parametric study for the use of PCM in heat stores embedded in aluminium bottles for solar combisystems was carried out.

• The Institute of Thermal Engineering at Graz University of Technology performed tests and simulations with different PCM materials encapsulated in plastic tubes and steel containers for stores for conventional boilers to reduce the number of start-stop cycles of the burner.

The two other projects are slightly different:

• At the Department of Civil Engineering, Technical University of Denmark the use of super cooling of PCM materials for long-term heat storage was investigated with simulations. This project showed that a 10 m3 only PCM seasonal storage using the supercooling effect is theoretically possible. Experimental setup assessed some assumptions on heat transfer in a bulk PCM tank

• The Institute of Thermal Engineering at Graz University of Technology performed tests and simulations with PCM-slurries of microencapsulated paraffins for stores for conventional boilers to reduce the number of start-stop cycles.

The above project is also dealing with heat exchangers immersed in PCM material Table 1. Summary of prototype storage units studied in Subtask C.

Type of Technology

Material

Stage of Development

Investigating

Institute

PCM seasonal storage using subcooling

Na(CH3COO)3 H2O

Lab prototype; Simulation model for store developed and seasonal simulations of the system were performed

Technical University of Denmark (DTU), Denmark

Macroencapsulated PCM in storage tank

Na(CH3COO)3 H2O + graphite

Lab prototype; Seasonal simulations of the system were performed, using the model developed by the Institute of Thermal Engineering, Graz Unviersity of Technology

University of Lleida, Spain

Macroencapsulated PCM in storage tank with integrated burner

Na(CH3COO)3 H2O + graphite

Lab prototypes; Simulation model for store developed and validated; Seasonal simulations of the system were performed according to the reference conditions from Subtask A

University of Applied Sciences Western

Switzerland (HEIG — VD), Switzerland

Microencapsluated PCM slurry

Paraffin,

Lab prototypes, Development of simulation models for a store filled with slurry with various internal heat exchangers and flow/return pipes and an external heat exchanger with PCM slurry on one or both sides.

Graz University of Technology, (IWT — TU Graz), Austria

Macroencapsulated PCM in storage tank

Paraffin,

Na(CH3COO)3 H2O

with/without

graphite

Simulation model for store developed and validated; Seasonal simulations of the system were performed for various hydraulic schemes for heating systems in order to analyze the reduction of the boiler cycling rate compared to water stores.

Graz University of Technology, (IWT — TU Graz), Austria

Immersed heat exchanger in PCM

Na(CH3COO)3 H2O without graphite

Simulation model for store developed and validated; Seasonal simulations of the system were performed for various hydraulic schemes for heating systems in order to analyze the reduction of the boiler cycling rate compared to water stores.

Graz University of Technology, (IWT — TU Graz), Austria

• The Institute of Thermal Engineering at Graz University of Technology performed tests and simulations with a bulk PCM tank with an immersed water-to-air heat exchanger for conventional boilers to reduce the number of start-stop cycles of the burner.

For a summary of these projects see Table 1; the main results are given in the following chapters.