SUBTASK A: EVALUATION METHOD AND DISSEMINATION OF RESULTS

Subtask Lead Country: Switzerland
Subtask Leader:

The main activity of Subtask A during 2006 has been the follow-up of the sales of our “State of the Art” handbook on short term heat storage. It has been sold through the internet since the beginning of 2006 for a price of 35 euros plus shipping. Sales went smoothly about 1 copy per week without strong promotion.

The final reference conditions and the final reference system for comparing different storage options with the same framework was completed by the Austrian team. It has been pre-tested by some of the participants and will be used intensively in 2007 by all teams. It is an important outcome of this Task and will be used in the simulation work on solar combisystems for heating and cooling a single family house in four different climates.

The Task web site can be found at www.iea-shc.org under Task32. It has been updated with working documents and is the Task platform for exchanging information with more than 230 documents, meeting presentations and articles on heat storage. An electronic Newsletter will be issued at the beginning of 2007.

SUBTASK B: CHEMICAL AND SORPTION STORAGE

Subtask Lead Country: Sweden
Subtask Leader: Chris Bales

Six projects are being investigated. Subtask B has promising technologies for dense storage. However the task is difficult. Material characterisation at SPF Switzerland and setting up of projects was longer than anticipated.

Project TCA in Sweden is the most advanced and suited mainly for cooling applications. Project Modestore in Austria came to disappointing field results for a seasonal storage with silica gel. The material appears not to be suited to this application. At SPF in Switzerland, a project aims at understanding how a zeolite or silica gel bed is behaving. The German project  called Monosorp has the potential to give a seasonal storage with only 8 m3 of zeolite for a passive house. Theoretical concept is now proven and laboratory tests started in July 2006. Two new projects (thermochemical storage in the Netherlands and NaOH storage in Switzerland) joined our Task during 2006. The work on chemical heat storage is unfortunately still in its infancy due to low budgets in all countries on this topic.

SUBTASK C: PHASE CHANGE MATERIALS

Subtask Lead Country: Austria
Subtask Leader: Wolfgang Streicher

Six projects are being developed. Most of them use sodium acetate as the phase change material. Subtask C is progressing well with combisystems in focus. The Danish project shows that a 10 m3 only PCM seasonal storage using super cooling effects is theoretically possible. Experimental setup will assess some assumptions on heat transfer in a bulk PCM tank.

The Austrian team on PCM in tanks tried to tackle the thermal properties of sodium acetate with graphite problems and the power rating of several heat exchanger arrangements:
with a 30% SA+G PCM tank, can be achieved a 1.4 to 2 density compared to water over 50-90C. Project CosyPCM in Switzerland is similar but focuses on the number of cycles that can be achieved by a tank with 14% volume of PCM in the upper part.

The Spanish team has shown that the cost of a PCM tank in a combisystem can double the price of the tank, but save 25% space in a Spanish cellar. The team at the University of Lleida is also working on the enhancements of the heat exchange quality for sodium acetate in aluminum bottles.

SUBTASK D: WATER TANKS

Subtask Lead Country: Germany
Subtask Leader: Harald Drueck

Six projects are under investigation. Subtask D is focusing on improving tank storage and regular combisystems. ITW has already done a lot of work in this area and will contribute more to Task 32. The Danish project is well advanced in comparing several devices to enhance stratification effects and several ways to produce tap water from the storage tank.

The SPF team in Switzerland is studying a drain back-pressureless tank. New TRNSYS types are being developed for flue gas so able to have accurate CO2 emission calculations for combisystems.

Two new projects from the Netherlands and Germany started recently. In Spain, a theoretical project showed interesting results in dimensionless numbers analysis to evaluation stratification effects.