Solar Simulator in Use in Finland


by V Erkkilä and H Suokivi, Solar Simulator Finland Ltd


A solar simulator, is, in effect, an "artificial sun" which can be used indoors, independently of weather conditions. It is used in tests where solar-like radiation is required and is especially useful in testing solar energy devices.


View of the solar simulator with a solar thermal collector (made by Neste Oy) in stagnation test.


The energy crisis of the early 1970s sparked a universal interest in renewable energy technology. One symptom of this was the need of solar simulators, and Finland was no exception. The planning and building of the solar simulator were carried out by the University of Turku and the work was completed in March 1982. The project was financed by the Finnish National Fund for Research and Development (SITRA). Between 1982 and 1996 the solar simulator was used by the solar energy research team at the Department of Physical Sciences. In spring 1996 the solar simulator with attached measurement
equipment was purchased by a private research institute.


The intensity, spectrum and uniformity of the radiation of the solar simulator should correspond to the qualities of solar radiation as closely as possible.

Uniform radiation, corresponding to the AM2 spectrum of the real sun, can be produced on an area of 1.2 x 2.2 m2 placed 4-6 m away from the solar simulator. The 35 lamps (Thorn CSI) are mounted on a panel in seven rows. Each lamp can be rotated around two axes in order to make the uniformity of the radiation better than 10%. The spectrum produced is continuous and corresponds very well to the wavelength distribution of the real sun (figure 1). The intensity of the radiation can be adjusted between 500-1,300 W/m2; it is measured with a pyranometer Eppley PSP/Kipp & Zonen. Wind (on the surface of a solar collector, for example) can be simulated with a crossflow fan. The velocity of the air is 3-6 m/s.


Figure 1: Spectra of the solar simulator and the real sun.


The main uses of a solar simulator are product development tests of solar energy equipment; for example, the efficiency and heat loss measurements of thermal solar collectors, and determination of the characteristic curve of PV-panels. For PV-measurements, the spectrum can be calculated to correspond to the AM1.5 spectrum. Constant measurement conditions are necessary for observing changes in efficiency when the collector parameters are modified. One of the major advantages of a solar simulator is fast feedback. In this way the best combination of materials and structures can be found for different applications.

Other solar energy applications that have used the solar simulator are:

  1. testing of window materials and prefabricated units,
  2. testing of materials and structures used in passive utilisation of solar energy in scale models and
  3. research of peat drying.

The solar simulator can also be used in materials testing; for example, to discover the effect of radiation on surface temperatures of different materials, and fastness and fading of dyes.

For more information please contact the CADDET Finnish National Team in Helsinki.

The CADDET Renewable Energy Newsletter is a quarterly magazine published by the CADDET Centre for Renewable Energy at ETSU, UK.

The articles published in the Newsletter reflect the opinions of the authors. They do not necessarily reflect the official view of CADDET.

Enquiries concerning the Newsletter should be addressed to
Pauline Toole, Editor, CADDET Centre for Renewable Energy, ETSU, Harwell, Oxfordshire OX11 0RA, United Kingdom. Tel: +44 1235 432968, Fax: +44 1235 433595.