Measuring installation climate unit.
Bed cooling in a multi-layered bed system.
ing and growing and harvesting operations, this should normally be approximately identical in both situations. Water (cook out): The rooms with bed cooling appeared to need a little more steam at cook out than the standard rooms. The reason cannot be substantiated. Possibly the bed cooling with insulation makes it slightly more difficult for the compost to reach the correct cook out temperature, resulting in a slightly longer cook out time. Humidifying: On farm 1 no steam was used for humidification, the floors were just occasionally wettened. Despite farm 2 also indicating that no steam humidification was used, values were however recorded (registration was linked to the humidifica- tion valve). The reason could be that a valve was closed somewhere. The data relating to humidifying is therefore unreliable. What can be seen is that the rooms with bed cooling required less humidification. This correlates to experiences in practice that show that casing soil dries out less with bed cooling, and that not only is less humidifi- cation needed, but also less spraying. Bed cooling (incl. pump): In the rooms with bed cooling, extra energy is of course required to operate the bed cooling itself and the pump that sends the water flowing through the cooling plates. The pump does not have variable frequency drive and runs 100 % if there is a demand for bed cooling. For calculation purposes, it was assumed that the pump runs for a total of one week per cropping cycle. As well as the pump, the bed cooling is cooled by an ordinary cooling system via a heat exchanger. The total volume of heat extracted from the compost via the air (cooling coil) and bed cooling will ultimately still have to be delivered by the cooling system. It is tempting to think that you can save on energy after the room has been filled by operating the cooling coil, for example, at 50 % capacity compared with 100 % in a standard room, but bed cooling also needs energy to work. By definition, the cooling system will have to take the energy from the compost. If the consump-
tion of the bed cooling, bed cooling pump and cooling coil is subsequently added up, the figure is higher for rooms with bed cooling than for the cooling coil in the standard rooms.
Summary of results of energy consumption
The table below summarises the results of the four rooms, showing per farm the standard room first and then the room with bed cooling. For comparison of the energy consumption per room as a single value, all the values have been converted to the primary energy requirement per m2 surface area.
Summary of results
Total primary energy cons. per m2 Total primary energy cons. per m2 Farm 1 compared with normal
growing surface area standard room farm 1 growing surface area bed cooling room farm 1
savings, but rather accelerated growth (more cropping cycles per year) and better controllability of the compost. This conclusion is rather contrary to the expectation that less cooling energy would be required, but this expectation only con- sidered the energy used by the cooling coil and not the extra energy required for the bed cooling and the pump. The theoretical approach to the energy consumption of the individual components also confirms the findings of the measurements.
growing
Recommendations Further technical development of bed cooling can still be effected by better
Primary energy MJ/m2
130,51 155,65 119%
Total primary energy cons. per m2 Total primary energy cons. per m2 Farm 2 compared with normal
growing surface area standard room farm 2 growing surface area bed cooling room farm 2
146,16 157,10 107%
Despite the problems with the meas- urement data mentioned previously, the results clearly point towards more energy being consumed for cultivation in rooms with bed cooling. Taking farm 1, this could even be 19 % per m2
growing
surface area, but on this site a few cycles of chestnut mushrooms were grown, which require more energy than white mushrooms. Looking at farm 2 where only white mushrooms were grown, you get a more realistic picture and can conclude that rooms with bed cooling use 7 % more energy per m2
growing surface area than
standard rooms. With identical yields, this means that 7 % more energy is needed per kg/mushrooms.
. For the present, the cultivation results do not suggest that permanently higher yields per m2
The only way that the energy consumption per kg/mushrooms with bed cooling can be reduced is to realise higher production per m2
growing surface area
can be achieved. The benefits of bed cool- ing should not be seen for now in energy
insulation underneath the cooling plates (savings on energy for cooling/heating) and minor technical and control-en- gineering enhancements. An option to consider that may still save energy if bed cooling is used could be a connection to a heat pump. The cooling delivered on one side of the heat pump can supply extra warmth for the heating on the other side. Connection to a thermal energy storage system can supply the cold for bed cooling for much lower energy costs, as it does not have to be provided by the cooling system.
The most important further developments in bed cooling will have to be driven by ways of improving the production per m2 and the quality. In this case, bed cooling will be extremely interesting. Better utilisation of the nutrients in compost, partnered with the right supplements, should form the foundation for such continued development, combined with optimal controllability of the compost through using the bed cooling system.
MUSHROOM BUSINESS 45
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