Kymi-Solar | Greenreality

The system will generate more than half of the building's heat demand and its payback time is less than eight years.






Energy efficiency of old suburban housing blocks is easy to improve

The OptiSun heating system recovers exhaust air waste heat and utilises free solar heat. District heating is only required in the winter.

The main elements of the OptiSun heating system are a rotating solar heat collector, a hot water boiler the same height as the block of flats, and an exhaust air heat pump. They are located in a pilaster structure erected at the end of the building, making it unnecessary to tamper with roof structures.


The system is designed for blocks of flats with exhaust ventilation systems.

 "The biggest energy-saving potential lies in old housing blocks. Their roofs are perfect for instalment of solar heat collectors," says the developer of the OptiSun system, Ville Terävä.

"The rotating collector has revolutionised the dimensioning of solar heat systems in northern conditions. The capacity of the tubular heat accumulator is now designed to meet consumption. This enables us to optimise the operations of the collector and the heat pump," says Mr. Terävä.

In order to minimise heat loss, it is possible to place the heat accumulator inside the central shaft of the stairwell, for example. The horizontally rotating and sun-following collector adjusts the temperature of the collector by stopping in the shade if necessary.

"It is possible to finance the entire investment with the savings it will generate," says Mr. Terävä.


The OptiSun system operates on free solar and waste heat and generates ecological and carbon-dioxide-free heating energy. And it will not increase electricity consumption in the building.



The heat energy consumption of a housing block built in 1970 is 431 MWh/a, of which the OptiSun system can replace 66%. The investment cost is EUR 130,000 with a payback time of 5.4 years.