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The aim of the project is to test marketed solar heating systems in a laboratory test facility and to establish contact between installers of solar heating systems and house owners wanting to install solar heating systems.Two small SDHW systems from Batec Solvarme A/S and from Velux Danmark A/S have been tested under realistic conditions side-by-side with a small solar combi system from Sonnenkraft Scandinavia A/S. The thermal performances of the systems have been measured for a long test period. Measured thermal performances have been compared to thermal performances calculated with detailed simulation models for a short period for the three systems. A goodagreement between measured and calculated thermal performances was achieved for all the systems.The yearly thermal performance for the three systems was calculated for different hot water consumptions based on the weather data from the Danish Test ReferenceYear. The thermal performances are compared to the thermal performances of earlier tested marketed solar heating systems.The thermal performances for the three tested systems are lower than the thermal performances of the most efficient of the earlier tested systems. The reason is that the three systems are high flow systems with a hot water tank with a built in heat exchanger spiral, which equalize temperature differences in the hot water tank during operation periods of the solar collector. Low flow systems with a highly thermal stratified hot water tank, such as a mantle tank, have higher thermal performances than high flow solar heating systems based on spiral tanks. Further, two of the tested systems are based on hot water tanks with pipe connections to the upper part of the tank. These pipe connections results in high thermal bridges and thereby in a low thermal performance of the solar heating system. It is recommended to use hot water tanks with no pipe connections and penetrations through the insulation in the upper part of the tank. The tests form a good basis for development of improved marketed systems.

Research on solar combisystems for the Nordic and Baltic countries have been carriedout. The aim was to develop competitive solar combisystems which are attractive tobuyers and to educate experts in the solar heating field.The participants of the projects were the universities: Technical University of Denmark,Dalarna University, University of Oslo, Riga Technical University and Lund Institute ofTechnology, as well as the companies: Metro Therm A/S (Denmark), Velux A/S(Denmark), Solentek AB (Sweden), SolarNor (Norway) and SIA Grandeg (Latvia).The project included education, research, development and demonstration. Theactivities started in 2003 and were finished by the end of 2006. A number of Ph.D.studies in Denmark, Sweden and Latvia, and a post-doc. study in Norway were carriedout. Close cooperation between the researchers and the industry partners ensured thatthe results of the projects can be utilized. The industry partners will soon be able tobring the developed systems into the market.In Denmark and Norway the research and development focused on solarheating/natural gas systems, and in Sweden and Latvia the focus was on solarheating/pellet systems. Additionally, Lund Institute of Technology and University ofOslo studied solar collectors of various types being integrated into the building.

Pilot versions of a solar heating/natural gas burner system, of a solar heating/pellet burner system and of a façade/roof integrated polymeric collector have been installed in the summer of 2006 in a number of demonstration houses in Denmark, Sweden and Norway.These three new products have been evaluated by means of measurements of the thermal performance and energy savings of the pilot systems in practice and by means of a commercial evaluation.The conclusion of the evaluations is that the products are attractive for the industry partners METRO THERM A/S, Solentek and SOLARNOR. It is expected that the companies will bring the products into the market in 2007.Further, the results of the project have been presented atinternational and national congresses and seminars for the solar heating branch. The congresses and seminars attracted a lot of interested participants.Furthermore, the project results have been published in international congress papers as well as in national journals in the energy field.Consequently, the Nordic solar heating industry will benefit from the project.

Within the frame of the project REBUS, "Competitive solar heating systems for residential buildings", which is financed by Nordic Energy Research, a new type of compact solar combisystem with high degree of prefabrication was developed. A hydraulic and control concept was designed with the goal to get highest system efficiency for use with either a condensing natural gas boiler or a pellet boiler. Especially when using the potential of high peak power of modern condensing natural gas boilers, a new operation strategy of a natural gas boiler/solar combisystem can increase the energy savings of a small solar combisystem by about 80% compared to conventional operation strategies.

At the beginning of 2003 the four year long research project REBUS on education, research, development and demonstration of competitive solar combisystems was launched. Research groups in Norway, Denmark, Sweden and Latvia are working together with partners from industry on innovative solutions for solar heating in the Nordic countries. Existing system concepts have been analyzed and based on the results new system designs have been developed. The proposed solutions have to fulfill country specific technical, sociological and cost requirements. Due to the similar demands on the systems in Denmark and Sweden it has been decided to develop a common system concept for both countries, which increases the market potential for the manufacturer. The focus of the development is on systems for the large number of rather well insulated existing single family houses. In close collaboration with the industrial partners a system concept has been developed that is characterized by its high compactness and flexibility. It allows the use of different types of boilers, heating distribution systems and a variable store and collector size. Two prototypes have been built, one for the Danish market with a gas boiler, and one for the Swedish market with a pellet boiler as auxiliary heater. After intensive testing and eventual further improvements at least two systems will be installed and monitored in demonstration houses. The systems have been modeled in TRNSYS and the simulation results will be used to further improve the system and evaluate the system performance.

Recently a number of Chinese companies started mass production of evacuated tubular solar collectors. Contrary to Europe, in China the evacuated tubular solar collectors have reached such a low price level that it has become normal to use these high-efficient solar collectors in many different types of solar heating systems. Four different evacuated tubular solar collectors produced by Chinese companies have been tested in a small solar domestic hot water test system. The test system has been tested under realistic conditions in a test facility for solar heating systems at DTU. By means of the tests a simulation model has been developed for each of the four solar collectors. With the developed models calculations of the yearly thermal performance of different Danish solar heating systems were carried out: Small and large solar domestic hot water systems, combined solar domestic hot water and space heating systems and solar heating plants. Calculations were carried out with the four investigated evacuated tubular solar collectors and with ordinary flat plate collectors. The investigations showed that the thermal performance of solar heating systems is increased by using evacuated tubular solar collectors instead of ordinary flat plate collectors and that the solar collector area of a solar heating system with a fixed thermal performance can be reduced considerably by using evacuated tubular solar collectors instead of ordinary flat plate collectors. The higher the solar fraction and the operation temperature are the greater the advantage of using the evacuated tubular solar collectors will be. For solar domestic hot water systems and for combined space heating and domestic hot water systems with typical solar fractions the solar collector area can be reduced about 2-3 times if the best suitable evacuated tubular solar collector is used instead of an ordinary flat plate collector. The price level of the Chinese evacuated tubular solar collectors that are exported to Europe is relatively high. With these prices it will be possible to improve the price/performance-ratios for solar heating plants with high operation temperatures. For the other solar heating systems it is not possible to improve the price/performance-ratios by using evacuated tubular solar collectors instead of flat plate collectors unless the solar fraction of the solar heating system is unusually high. As the prices of the solar collectors sold in China are very low, it is not unthinkable, however, that the prices of exported Chinese solar collectors can be reduced so that they can become attractive in several types of solar heating systems.