A. ТЬйг and S. Furbo2

1 AEE INTEC, Feldgasse 19, 8200 Gleisdorf, Austria
2 Department of Civil Engineering, Technical University of Denmark, 2800 Kgs. Lyngby, Denmark

* Corresponding Author, a. thuer@aee. at

Abstract

Based on elaborated knowledge in international research projects within IEA-SHC Task 26 and the ALTENER project “Solar Combisystems”, a new solar combisystem concept was developed. Therefore the focus was concentrated on minimizing the temperature in the system with the goal to reduce system heat losses and to increase the efficiency of the condensing natural gas boiler and the solar collector. After development and test of the first prototype in the laboratory, a demonstration system was built which replaced an old conventional natural gas heating system in a one-family house. Measurements in practice showed how this new natural gas — solar heating concept performs in comparison with the old one. A Solar gain of 370 kWh and energy savings of 536 kWh per m2 collector area were achieved for the new solar combisystem. Domestic hot water consumption reduced by 20 % and hot water circulation losses of only 7% of hot water consumption was achieved. The average space heating temperature difference could be increased by 50% leading to lowest possible return temperatures. In spite of more installed pumps and valves the electricity consumption of the heating system could be decreased slightly.

Keywords: solar combisystem, energy savings, measurements

1. Introduction

The project REBUS — „Competitive solar heating systems for residential buildings” was carried out from 2003 to 2006 with the goal to develop new concepts for solar combisystems in co­operation with industry partners [1]. Prototypes were first built and tested in the laboratory and further on installed in one family demonstration houses for in-situ long time testing and measurements. According to national boundary conditions PhD projects in Sweden and Latvia worked on solar combisystems in combination with pellet boiler and in Norway and Denmark solar combisystems in combination with natural gas boiler were investigated.

This paper summarizes the final results of the Danish PhD project where a new compact solar combisystem concept with direct integration of a condensing natural gas boiler was developed, tested as a laboratory prototype and finally installed as a second generation prototype in a demonstration one family house [2, 3, 4, 5].

2. Demonstration house

The demonstration one family house with 3 occupants is situated in a small city about 40 km north of Copenhagen/Denmark. The old heating system was a non-condensing natural gas boiler (construction year 1990) with 22 kW nominal power in combination with a 50 Liter domestic hot water tank. The heating system consists of old cast iron radiators with thermostatic valves. This old

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heating system was monitored in the period August 2004 to April 2006. In spring 2006 the new solar combisystem was installed: collector area of 6.75 m2 and 360 litre solar tank in combination with a condensing natural gas boiler (Milton Smart Line HR24). Beside the installation of the new solar heating system also two additional rooms were prepared to be used in the basement: one living room and a bath room, both equipped with floor heating. Monitoring of this new system started in October 2006.