10
CLIMATE
Experiences How do the growers get along with using the new con- trols? Van Nieuwenhoven: “The most obvious difference is that you have a lot more figures and measurement values than previously. This information wasn’t availa- ble and everything had to be done based on estimates. The data makes you far more aware of what is going
Four energy efficient climate modules
Moisture deficit regulation With traditional RH control, the moisture absorbency capacity of the growing room air also depends on the temperature. This means that adjusting the temperature also affects the moisture absorbency capacity and therefore evaporation. To achieve more stable evaporation, it is better to base control directly on the moisture absorbency capacity or the moisture deficit of the growing room air. An additional advantage here is that moisture deficit-based control is also unaffected by any changes in the air pressure.
Oxygen corrected maximum CO2-limit/ Air pressure correction As well as supplying CO2, moisture also suppresses oxygen. The com- bination of a high CO2 and a high absolute humidity can also entail the risk of a too low oxygen content. This can have negative consequences on the decomposition process in the compost. In order to prevent the risk of a too low oxygen content, the new climate programmes not only display the calculated oxygen values, but the maximum CO2 limit can also be corrected based on the absolute humidity value. If the air is too humid (summer), the maximum CO2 limit is decreased. If the air is too dry (win- ter), the maximum CO2 limit is incre- ased. This relationship corresponds to the methods used in practice. In a standard climate computer, all the calculations of the internal Mollier diagram are based on an outside air pressure of 1013 mBar, in other words the average air pressure at an altitude of 0 metre, or sea level. However, climatic influences (or the altitude) can result in a lower or higher actual air pressure. A lower air pressure in particular, which can occur during thunderstorms, has a negative effect on evaporation as at times of low air pressure the actual moisture content of the air will be higher than the indi- cated moisture content. This situation
may inhibit evaporation and can cause earlier maturation. By instal- ling an air pressure meter the correct Mollier values can be calculated, which can help prevent the problems mentioned above.
Inlet moisture control Controlling the RH (or moisture deficit) differences in the growing room based on the air inlet moisture content creates a two-stage control, which prevents the effects of lag ( comparable with the principle of air inlet temperature control). As humidi- fying and dehumidifying are adjusted based directly on the air inlet moistu- re content, the climate differences will be smaller and less heating, cooling and humidifying will be necessary. By comparing the air inlet moisture con- tent with the content in the growing room, it is simple to clearly indicate if moisture is being extracted. This can help signal the stagnation of evapo- ration can be signalled in time. This control features requires the system to be equipped with RH measurement of the inlet air.
Measuring systems for heat, moisture and CO2 This is not a control as such, but a measuring system which can be used to measure how much heat, moisture and CO2 the developing mushroom release to the surrounding air. If the temperature and RH of the inlet air are also measured, the difference with the values measured in the growing room indicates how much heat, moisture and CO2 is being released. Using a software tool that determines the volume of air entering through the air inlet, the total amount of heat (activity), moisture (evaporation) and CO2 being emitted can be calcu- lated. The measured evaporation especially appears to be very useful in adjusting the climate and in being able to choose the correct moment to spray - and the right amount of water- with more certainty (e.g. based on the amount of evaporation between spraying cycles).
on and gives a far clearer total picture than before. The measurements are very important and good monito- ring for abnormalities is necessary”. The most used controls at the moment are the moisture deficit, the air pressure correction and the air inlet moisture control. The minimum oxygen limit and the evaporation measu- rement are not used, but the grower does intend to use them in the future. Thijssen: “What you notice most is the more stable con- trol. We use the moisture deficit, minimum oxygen limit and the air inlet moisture control. We don’t measure evaporation, and we have no air pressure measurement on the farm.” He would like to introduce air pressure measurement, and use the evaporation measurement in the future. Weijers: “The greatest difference is the air inlet moistu- re measurement. Thanks to this measurement you know just what the computer is doing - whereas before you didn’t. We use the moisture deficit, minimum oxygen limit and the air inlet moisture control.” He mainly looks at the difference between the air inlet moisture content and the content in the growing room, and the evapora- tion measurements of the past 24 hours. There is no air pressure measurement. Willems: “You have a wider variety of data (evapo- ration measurement) at your fingertips and can see different patterns more easily. That gives better insight than ‘using your instinct’. The difference in moisture between the inlet air and the growing room can indi- cate certain tendencies.” He controls based on evapo- ration, as the RH is adjusted within a certain bandwidth if evaporation deviates. Van den Oord: “The growing room climate is control- led via the inlet, which is far more stable.” He uses a fixed moisture deficit during cool down and follows the evaporation values in relation to the particular moment of cultivation (see photo 5). “Now that we have figures at our disposal, we can intervene in time.”
Wishes The growers can list a number of improvements. Weijers: “You could show the S-curve (growth) in a graph with the help of cameras, and relate this data to the evaporation so that the harvest planning can be optimised.” Linking evaporation to the volume of water to be sprayed was also mentioned (see photo 4). Com- ment: with cooled beds very little moisture is lost when the mycelium is colonising the beds so in this case up to a quarter less water can be sprayed. Van den Oord: “Maybe at some time control within a bandwidth based on evaporation levels. For me- chanised cutting farms in particular, the relationship between evaporation and spraying could be very handy. Following pinheading with cameras in order to detect obstructions to good growth at an earlier stage, and so growers can take action. This visual assessment of the growing rooms could - certainly if large num- bers are involved- be converted into a ‘growth index’ alongside the evaporation data so that growers have all the information they need to correctly assess the status of their mushrooms. Analysis of the evaporation would certainly be a welcome addition, definitely on farms with large numbers of growing rooms.” A suitable quote to conclude this article is a comment made by one of the growers “I am really pleased with the system I have now. It saves me loads of time and money!” ◗
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