WELL-ADAPTED SOLAR HEATING SYSTEMS
EKSTA's solar systems were developed in stages over more than 15 years. The first solar collectors were installed in Fjärås in 1979. The plant, 380 m2 of
roof-mounted collectors (AGA air modules) combined with a heat pump, was rather complicated and expensive. This experience showed that the investment cost had to be reduced and that the design and mounting of the
collectors had to be better adapted to the ordinary building process in order to bring about competitive heat costs. In this first plant the extra cost for the solar system was covered by an experimental building loan
from the Swedish Council for Building Research (BFR).
A new line of development was then initiated and the result was a pilot plant with 150 m2 of site-built and roof-integrated collectors mounted on a children's
day-care centre in Vallda in 1981. This development resulted in a much cheaper and better adapted collector system compared to Fjärås, but other parts of the system, such as a pressurised buffer tank, were still too
A small system with 150 m2 of further developed roof-integrated collectors, combined with a non-pressurised buffer storage with immersed heat exchangers, was then introduced in Åsa in 1984. A major design
philosophy here was to have the buffer storage shared by the boiler and the solar system, as well as the domestic hot water and the space heating system, resulting in further cost reductions.
The next step was a
similar but larger system in Kullavik in 1987: 700 m2 of collectors combined with 50 m3 buffer storage and a wood pellet boiler. To increase knowledge about the direct extra cost for the solar system, EKSTA asked for
parallel tenders both in Åsa and Kullavik (conventional heating plant versus solar heating plant). This documented extra cost was then used to calculate the capital cost for the solar system.
totalling 4,200 m2 of site-built roof-integrated collectors (TeknoTerm IT) were installed from 1985 to 1992.
The latest development, a 220 m2 roof module collector, has now been applied in a new residential area
in Onsala. Prefabricated roof modules with integrated collectors (A-Hus AB), mounted on the heating plant and a carport, are designed to cover 25% of the annual heat demand in nine buildings with 36 residential units (2
500 m2 heated area). This development has resulted in even better integration in the building process, and has reduced investment
cost further and improved thermal performance.
EKSTA has also built two experimental
solar heating plants with seasonal storage; one using pipes in clay in Kullavik in 1983 and one with a folded steel tank in Särö in 1989, with the aim of achieving a larger solar coverage. However, at present these
technologies cannot compete with stored solar heat in the form of processed wood.
At present EKSTA owns and operates 6,000 m2 of collectors (generating heat equivalent to
250 m3 of oil per year). All plants
are still in operation with very low operation and maintenance costs. Main partners in the development of the solar systems are Andersson & Hultmark Projektering AB (engineering consultant), TeknoTerm Energi AB and
the Department of Building Services Engineering and the Monitoring Centre, Chalmers University of Technology.