Droplet curtain lowers heating costs while achieving higher yield in closed greenhouse

The Finnish cucumber grower Puutarha Timo Juntti Oy, based in Kaarina eliminates extra humidity and heat while maintaining high CO2 concentrations thanks to the Novarbo Heat Reuse™ System. With the Efficient Climate Control tool, they maintain vigorous growth and increase the cucumber yield. Reuse of the waste heat removed from the greenhouse is considered as the most significant advantage.

Finnish cucumbers
Puutarha Timo Juntti Oy is located in Kaarina, Finland (60°24′N 022°22′E) and produces cucumber and tomato in their 20 000 m2 (215 300 ft2) greenhouse, of which a quarter is equipped with the Novarbo Heat Reuse™ System.

“We followed with interest the Natural Resources Institute Finland’s research in the neighboring Piikkiö experimental greenhouse. Their research focused on climate control but we were also interested in the affordable and clean energy that the Novarbo droplet curtain collects from the greenhouse. I myself use geothermal energy at home and I’m familiar with heat pump technology. It encouraged the development of this idea” recalls the CEO Tero Juntti.

Inexpensive and Clean Energy for Heating
In 2015 the Novarbo Heat Reuse™ System was installed for 2500 m2 (27 000 ft2) area. The core of the system is a droplet curtain that collects humidity and thermal energy from the greenhouse air. The heated water is led to an insulated 1000 m3 (35 300 ft3) outdoor pool from where it is transferred by a 500 kW heat pump to the boiler and further to the greenhouse heating circuit. About 3500 MWh of heat is recovered annually by the droplet curtain system.

Good experiences with the Novarbo Heat Reuse™ System encouraged further investment. In 2019 a 2500 m2 (27 000 ft2) extension was completed with a similar system with Novarbo droplet curtains and an outdoor pool but with an even more efficient 750 kW heat pump. With the new expansion and hardware upgrade it is possible to recover up to 7000 MWh of energy per year.

Waste heat
“In cucumber cultivation for example lighting generates a lot of waste heat. We have been able to cover up to over 80 percent of the annual thermal energy demand with waste heat thanks to heat recovery. Heating used by greenhouses comes from the droplet curtain system for most of the year and around half of it even in winter frosts. The rest is supplied via liquefied petroleum gas of which combustion gases are utilized as CO2 supplementation” says Tero Juntti.

Better Growing Conditions Increase Yields
In addition to the benefits of heat recovery, effective climate management of a closed greenhouse improves also growth conditions and yield. Carbon dioxide levels remain high while excess heat and humidity can be removed without opening the vents. Cucumber benefits from a high CO2 concentration which is clearly visible in the harvested yield.

“Midsummer is the most challenging time for cultivation. In a normal greenhouse all other conditions are easy to adjust except removing unwanted heat. During a heat wave it is evident that plants in the droplet cooled greenhouse remain in better condition and this also results in a bigger harvest” Tero Juntti explains.

New systems require learning and getting used to but we have been satisfied with the Novarbo Heat Reuse™ System. In addition to increased yield we have obtained low cost clean energy for heating” concludes the CEO Tero Juntti.

For more information:
Puutarha Timo Juntti Oy
Number of Staff: 25
Cultivation Area: 20 000 m2 (215 300 ft2)
Cultivated Crops: Cucumber and Tomato
Novarbo Heat Reuse™: 5000 m2 of Cucumber (54 000 ft2)

For more information:
Novarbo Oy
Arttu Lammensalo – Project Engineer
+358 40 846 9086

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