In this project two sorts of solar collectors are used: an individual solar system with return reservoir and a collective solar system with a chemical product in the water.

Individual solar system with return reservoir (Block 1; 3 units) In three houses an individual solar boiler with return reservoir (make Izen) was placed. Figure 1 depicts a flow chart of the installation. On the roof oriented to the south of each house a solar collector with a surface of 2.75 m² was installed.

The solar heat is stored into a boiler of 100 litres. The circulation pump only runs if the temperature measured in the solar collector is 10° higher than the temperature in the solar boiler. If the temperature difference is less than 2° C, the circulation pump is switched off. In this case, the water in the solar collector automatically returns to the return tank. A multifunctional device on natural gas ensures the after-heating of the domestic hot water and radiators; the heating and the heating of the ventilating air is based on the condensation technique (see text about the individual multifunctional heating plant with condensing gas boiler and integrated ventilation).
 

Figure 1: flow chart of the installation of block 1 at Zonnige Kempen, Houtvenne.

Supplier of Technology:

The manufacturer of the solar system with return reservoir is:

Izen
Hoeksken 56
B-2275 Lille
Phone: +32 14 55 83 19 Fax: +32 14 55 83 17
e-mail: info@izen.be
www.izen.be


Collective solar system with chemical product (Block 2; 12 units)
The heating of the domestic hot water in the big block with 12 building units is also ensured by solar boilers, but here a collective system of 24 flat-panel solar collectors of 1.7 m² each is used.

Figure 2 depicts a flow chart of the installation. The heat is stored in four boilers with a content of 500 litres each. One boiler also serves as peak boiler. To this boiler the condensation boiler is connected for additional heating in the transitional season and in wintertime. The circuit between the solar collectors and the four boilers is filled with a certain chemical product so that the pipes must not be drained in winter. The solar system was supplied by the company Viessmann.
 

Figure 2: flow chart of the installation of block 2 at Zonnige Kempen, Houtvenne

The manufacturer of the solar system with chemical product is:

Viessmann – Belgium bvba
Hermesstraat 14
B-1930 Zaventem (Nossegem)
Phone: +32 02 712 06 66 fax: Fax: +32 02 725 12 39
www.viessmann.be

Monitoring results for the solar systems:
In block 1 (3 dwellings) an individual solar collector system for domestic hot water has been installed. In block 2 a collective solar collector system for domestic hot water has been installed.

Type of system: Domestic hot water system
Number of dwellings: Block 1: 3
Solar collector orientation and slope South (194°) 60°
Total collector area Block 1: 2.76 m²
Storage volume Block 1: 80 litre

The table below shows the results from block 1 (results of the individual system) with a surface of 2.76 m².

	Solar radiation in collector surface kWh	Hot sanitary water heated by sun kWh	Hot sanitary water heated by boiler kWh	Efficiency of solar collectors  %	Share of sun in heat demand for domestic hot water %
June 2000	260	128	57	49	69
July 2000	221	85	122	38	41
August 2000	354	163	96	46	63
September 2000	242	98	86	40	53
October 2000	185	75	86	41	47
November 2000	117	42	105	36	29
December 2000	92	38	133	41	22
January 2001	127	54	139	42	28
February 2001	143	56	101	39	36
March 2001	136	53	119	39	31
April 2001	239	88	74	37	54
May 2001	363	141	35	39	80
Total	2479	1021	1153	41	47

For block 2 we can fall back on measurements carried out by students for their civil engineering thesis. We notice that here as well a saving of more than 50% has been realised, namely 50.6% for the year 2000 and 23,033 MJ/year without collector 35,521 MJ/year and with collector 12,488 MJ/year), being 65% for the year 2001. It shows that the financial cost-effectiveness improved because the basic costs could be divided over a larger number of entities.