climate modules
Inlet air measurement with wet and dry bulb sensor (and double-walled reservoir).
unable to withstand cook out, and had to be removed during this phase. The current version supplied by one company has been modified and coated so it is now resistant to cook out. The systems offered by the other suppliers use wet and dry bulb sensors. For inspection and maintenance purposes these sensors are installed at working height in the growing rooms on most of the farms, and connected to the air inlet duct via an insu- lated pipe. In the early stages, many problems were caused by the unreliable air inlet measurements. These were triggered by the growing room temperature influencing the water reservoir. This issue was solved by making a double-walled reservoir and blowing the inlet air into the space between the walls so that the influence of the growing room air was eliminated. This version (photo 3) turned out to be the most practical and reliable model using a dry and wet bulb sensor. To calculate the evaporation levels the air volume of the fan is also needed. This figure can be entered based on manually taken readings - so that no hardware is required - or taken from the pressure difference measu- red over the fan.
Influence on quality and production The growers generally share the opinion that their investment has been beneficial to quality. Evaporation- related problems, such as bacterial blotch caused by too low evaporation with inactive compost with a too low CO2 production, have been prevented. Van Nieu- wenhoven: “We used to have a lot of moisture problems with the last mushrooms in the 1st flush (watery stipe and bacterial blotch) and internal moisture in the 2nd flush. Now we see that a lot less and we harvest firmer mushrooms. Growing the 2nd flush is much easier than before, we can almost do it automatically.” Van den Oord: “We have significantly fewer issues with discolouration of the cut edge/hollow stems. In the past it was unclear what the effect was of certain actions on moisture extraction and growth. Now the readings signal flushes that are potentially problematic, and you can take action to stimulate good growth - like setting the fan speed a little higher, for example. The growers are unanimous in their experiences that the better quality has had a positive effect on yields.
Linking the spraying computer and the climate com- puter - a possibility in the future?
The mushrooms can stay on the beds for longer and so can be harvested when they bigger. As the mushrooms can evaporate properly, the individual weight is higher. Two of the farms have a central air duct, which also has good results. Weijers: “If you have a central air duct the situation is less critical than if you use individually controlled climate units.”
Influence on energy consumption How much energy the new controls actually save is less easy for the growers to define than the influence on quality - and production - but the general feeling is that a more stable climate does lead to energy savings, par- ticularly for cooling (lower cooling demand). Thijssen mentions another point: “The minimum oxygen limit is also a good control feature that saves energy during extremely cold or hot weather.” Willems emphasises that energy savings begin by implementing good hardware, such as a good climate unit, an energy efficient cooling installation with heat recovery and a low temperature heating system. “As far as the controls go, a stable control without any overlap will save energy - certainly with individual climate units.”
Knowledge
One of the obstacles mentioned by the growers was lack of knowledge about the new control options. The suppliers, and some of the growers, indicated in some cases that insufficient knowledge meant that only part of the new controls were fully utilised. As there are not that many fellow growers using the same system or growing method there are limited opportunities to exchange knowledge, and some growers think the suppliers could be more supportive and explain the system in more detail. But: “What’s important is the wil- lingness of the grower - whether he or she is prepared to invest time in getting to know the system”, says Willems. Weijers agrees: “Growers would rather not sit at a computer for too long, even though that’s where they can reap all the benefits, by analysing the graphs for instance. An automatically generated graph of the evaporation pattern can be very useful, especially if you have a lot of growing rooms.”
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Display in the growing room, including measu- red evaporation values.
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