A necessity in harsh climates such as that in Finland, conventional glass-built greenhouses are notorious for their low efficiency: they need to be heated extensively in the winter due to poor insulation but are too hot in the summer unless the roof vents are opened to allow some of the carbon dioxide-rich hot air to escape, which impedes the growth of the plants.
Cucumber harvests in the country, for instance, are twice as big in the winter than summer for that very reason, despite the fruit requiring a stable growth temperature of 27 Celsius.
His solution is a windowless greenhouse constructed of plywood walls that are lined with black rubber mass to guarantee air-tightness and coated with aluminium to create a surface that reflects light onto the plants, making it ideal for housing vertical farms.
The 36-centimetre-thick wall modules have been treated utilising vacuum drying, a method that has been used on wood for over a century but never before on entire walls. The integrity problem caused by the intense pressure applied during the process was solved by inserting a structure between the plywood panels.
“The hardest part was developing the right coating to keep the module air-tight,” he revealed.
50% less energy, 99% less water
Using LED lights enables farmers to regulate not only the amount but also the wavelength of light to boost the growth of the plants while eliminating the need for a separate heat source – even during the frosty winters of Finland.
Herranen explained that plants convert light to thermal energy so efficiently that the well-insulated structure can be kept warm without a separate heat source also in the winter, meaning it consumes roughly 50 per cent less energy than a conventional glass-built greenhouse in year-round cultivation in Finland.
“There’s even enough excess heat to be distributed to others through the district heating grid,” he added.
Water consumption, in turn, is 99 per cent lower than with traditional farming methods, as the air-tight modules mean the only drops of water leaving the ecosystem are those contained in the harvested plants.
A market worth billions
Herranen originally developed the wall modules for office and residential buildings but realised their potential in greenhouse farming partly by accident, after reading a report on cucumbers by Natural Resources Institute Finland (LUKE).
“The commercialisation possibilities were better for greenhouses,” he said.
The project team is nevertheless confident that demand for the modules will emerge also in residential and commercial construction. As the modules are suitable for the equally harsh but distinct conditions of Finland and Sahara, the potential market for them is estimated to be worth billions.
The innovation was commercialised with the help of Business Finland’s New Business from Research Ideas (TUTLI) funding.
Good News from Finland is published by Finnfacts, which is part of Business Finland.