ENERGY SAVING
Air distribution and air movement
Poor air distribution and air movement in growing rooms can impact negatively on mushroom production, but also waste energy unnecessari-
ly. We have summarised the most important things to remember. By Jan Gielen, DLV Plant Mushrooms, Manager / Climate & Energy Specialist,
j.gielen@
dlvplant.nl
I
n practice, the incidence of problems relating to air distribution and air movement is remarkably high. These complications manifest themselves as difficulties with evaporation and noticeable variations in development between mushrooms at the front/rear of the room, left/right/upper/ lower shelves and over the width of the beds. The result in all cases is poorer quality and lower yields. Inefficient air movement also wastes energy unnecessarily. When tracing the cause, it is important to differentiate between problems caused by air distribution (along the length of the growing room) and problems caused by movement (across the beds).
Climate unit at the front As a rule of thumb, the climate unit can be placed at the room entrance to distribute air along the length of the room when shelving systems are used of up to approx. 30-35 metres. Achieving even air distribution and tempera- tures along the length of the room will be more difficult with shelving longer than this – for a variety of reasons. In long growing rooms there is a risk of temperature differences between the front and end of the air duct. Distributing the air correctly in such long rooms is also a challenge.
Per air duct, the growing surface area in square metres is so large that air ducts with a larger diameter are required. However, space to accom- modate this is not always available. If growers make concessions and install smaller air ducts, air distribution along the length of the room will not be sufficient. To get around the issue of using larger air ducts, but still being able to construct longer growing rooms, when shelving exceeds 30-35 metres the climate unit is sited at a central position in the growing room. The air – from the left and right side of the room- is distributed to the front and back of the room via a T-piece. So in fact there are actually four air ducts in a growing room. By applying this method, uniform air distribution can be achieved for up to double the length – in other words shelving of approx. 60-70 metres long. Theoretically, growing in even longer rooms is also possible by installing a further two T-pieces at the left and right of the room.
Air distribution
This article was made possible due a contribution from the Dutch Steering Committee for Clean & Efficient Mushroom Growing. This committee unites LTO Mushroom Group, the Product Board for Horticulture, the Ministry of Economic Affairs, the Netherlands Enterprise Agency and Dutch mushroom growers and aims to facilitate energy savings and the application of renewable energy.
The greatest culprit behind problems with air distribution is often air ducts with an insuffi- ciently large diameter. This creates too high air velocity in the ducts, which means air is expelled from the openings too quickly. The use of air ducts with a too small diameter is often related to a general lack of space for picking, spraying systems and the total cropping surface area. In line with a large cropping surface area in square metres, a proportionally larger air duct is required. As mentioned above, in large growing rooms the climate unit can be located at the centre of the room to enable smaller diameters of air duct to be used, as each duct then only has to transport half the required volume of air. Another mistake commonly made by growers is making extra openings in places where too
14 MUSHROOM BUSINESS
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