The solar trajectories and the environmental conditions set special requirements for the solar collectors in the areas far from the equator.
Thanks to the vacuum tube absorbers, the temperature of the environment or the outdoors or the wind does no longer have a major impact to the production of solar energy. The number of sunshine hours and the sunbeams’ angle of incidence to the collector (altitude and direction angle) have greater importance.
Near the equator, between the Tropics of Capricorn and Cancer, the sun rises and falls quickly. The direction angle and altitude of the sun are both about 180 degrees. In Finland, the altitude of the sun is highest in Southern Finland, about 53 degrees, and the change of the direction angle is about 330 degrees. Above the Arctic Circle, the sun’s change of the direction angle is 360 degrees in summer and 0 degrees in winter.
Due to the above described solar trajectories, the problem of sun heat systems in northern conditions has so far been the disposal of excess heat in summer. It can be difficult and expensive. Usually it has led to oversized capacitor volume, which increases the costs, or too small collecting area. In both cases the sun heat part remains small and the stored heat transfer fluid isn’t hot enough to produce warm water in autumn, winter and spring. Together with the OptiSun hot water boiler, the OptiSun solar collector solved these former technology’s problems.
The development of the OptiSun Solar collector
There were no solar collectors optimized for Finland’s conditions in the market, so in 2012 we started a product development project together with Tampere University of Technology with the purpose of developing the OptiSun collector. The structure and function of the OptiSun solar collector developed by Kymi-Solar Oy, has been optimized with a calculation software created during the project.
On the basis of simulations operated with the software, we ended up to the structure where the vacuum tubes are horizontal and the CPC (Compound Parabolic Consentrator) reflectors behind them reclined to 27 degrees compared to vertical. Then the reflectors centralize all the sunshine in Finland’s conditions, also the diffuse radiation from the snow cover, to the vacuum tube absorbers in the focal point.
In addition, we ended up to the horizontally sun following structure, not because of the multiple heat dissipation but specifically because of its ability to turn into the shadow. This is an important feature in the areas where the sun’s change of the direction angle is great, so we get much more sunshine in summer than in winter.
The sizing of the OptiSun Solar collector
You usually need one OptiSun solar collector per every high block house staircase. For smaller block houses, one collector can be enough. The collector’s max dimensions are about 5m x 8m (height x width). The size and number of collectors are calculated based on the property’s heat demand.
The main parts, installation and connection of the OptiSun Solar collector
The main parts of the collector are the horizontal vacuum tube absorbers with the CPC reflectors and steel grate where the absorbers are attached and which is working by the stepping motor. The grate with the absorbers and the pillar form a whole, which you raise to the roof in one piece.
The best target for the collector is a gabled house, where the grate’s pillar, worm gear and stepping motor with its control unit are in the attic under the rooftop. There they are easily reachable and protected from the weather. In addition to that, the pillar of the sun heat collector can easily be anchored to the reinforced concrete floor which has been cast in place or built of cavity slabs, instead of the rooftop.
The OptiSun Solar collector will be connected to the OptiSun hot water boiler.
The structural and functional security of the OptiSun solar collector
The structure of the OptiSun solar collector has been designed in accordance with EU Machinery Directive to be safe and withstand among other things all the winds in the installation place. That’s why the OptiSun sun heat collector’s production versions are provided with the CE Marking. The installation will be planned according to the same principle and each target’s structure.
The function of the OptiSun solar collector
The collector and the whole OptiSun system is controlled with the remotely accessible control unit of the stepping motor.
The OptiSun solar collector follows the sun’s horizontal movement synchronized by the clock. If there is a threat of too much heat, the collector stops and stays in the shadows if needed. Thanks to this, the OptiSun solar collector can adjust the temperature of the hot water boiler, regardless of consumption. Then the size of the boiler can be optimized according to heat demand, without fear of overheating. It saves space and costs.
With the OptiSun solar collector it’s possible to collect sun heat more than twice as much compared to a sun energy system with stationary collectors.
The condominium can lease the backside of the OptiSun solar collector for advertising
The absorber parts of the OptiSun solar collector are reclined to 27 degrees compared to vertical. However, they are put one on the other, which prevents snow to drift, so the backside of even about 5m x 8m sized collector is vertical.
In the dark when sun energy is not available, the collector’s backside with a neon sign or a led display can be controlled so that it turns to the wanted direction, and it can be used as leased advertising space.
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