Always constant temperatures in new storehouse CULTIVATION AND TECHNOLOGY ventilators switched on to remove the surplus of CO2 from the storage units. That’s exactly what happens, because the EC ventilators – also from Tolsma – change direction to subsequently suck the air from the heap of potatoes. ‘This needn’t be too long, 10 minutes at the most, because CO2 gas is heavier than air, which means that you only need to refresh the bottom layer of air and you keep the air flow limited to a minimum’, Van der Maas explains. It would be a good idea to start using white corrugated roofing instead of the darker ones, for example. However, there isn’t a single Dutch building inspector who would allow this. Stop Ready. Normally speaking, many growers with outside air cooling already start with additional gas treatments at the beginning of January. However, in this optimally-insulated storehouse that also only uses outside air ventilation, gas treatments are not used at all. Because the temperature has always remained an absolutely constant 7.5 degrees, there’s still no sprout to be seen halfway through the month of May. The frying quality is also still very good according to buyer Farm Frites. What does require careful monitoring is the CO2 concentration in the units, says Van der Maas. If there isn’t sufficient fresh air, the CO2 concentration can become too high, which subsequently may lead to deterioration in the frying quality. For that reason, Van der Maas always leaves the swing-up doors slightly open (1 cm) to enable a bit of fresh air to come in continuously. In addition, the Tolsma Vision storage computer boasts an air refresher program to prevent the CO2 concentrations from becoming too high. At set times, the shutters are briefly opened and the No mechanical cooling needed Because this building construction can keep all the heat and cold out, mechanical air cooling is not necessary, which saves energy costs. Moreover, a minimum of ventilation is needed and in combination with energy-efficient ventilators and a state-of-the-art storage computer program, the total energy use is exceedingly low. Van der Maas has experienced that the energy use per ton of stored product is half of what he used to use in his air-cooled storehouse in Waddinxveen. The lower energy costs make up again for part of the extra investment costs of the optimally-insulated storehouse. According to Hoeckx, the costs are roughly 20 eurocent per kilogram of potatoes, installation costs excluded. This means that Van der Maas’ invested a gross amount of 600,000 euros for the storehouse piling included. ● Leo Hanse The continuous half-roof of the storehouse clearly shows how the air insulation moves freely from the ridge to below. Potato World 2013 • number 3 27 Pagina 26
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