ENERGY
Energy aspects bed cooling
The ‘Together in Bed Cooling Energy’ project examined the energy consumption of bed cooling in a multi-layer bed system. The results revealed that, for the time
being, energy savings cannot be counted among the advantages of bed cooling. By Jan Gielen, DLV Plant Mushrooms
T
he ‘Together in Bed Cooling Energy’ project was run par- allel to the practical network project ‘Together in Bed
Cooling’ to monitor energy consumption of a multi-layer bed system under practical conditions for comparison with a standard cultivation method. The aim was to clarify whether this, in addition to the already known aspects of bed cooling, would also lead to energy savings.
The bed cooling system is based on cooling plates installed on the beds under the nets, which can directly cool, or heat, the compost. As this system is practically only applied for cooling, it is usually referred to as bed cooling. Directly steering the compost temperature, independently to the air temperature, offers a number of interesting benefits and possibilities for cultivation. Bed cooling certainly holds the potential to be extremely interesting for the sector, not only in terms of greater sustain- ability in growing, but also in improving profitably for growers. One of aspects involved is the energy consumption of bed cooling compared with standard growing methods. As direct steering of the compost temperature using bed cooling ensures better control of this temperature– par- ticularly after filling – less cooling energy is expected to be used. Signals from situations in practice do indicate that the position of the cooling valve in the post-filling period is indeed much lower than in a standard growing room. So it should be possible to make savings, chiefly on energy used for cooling.
The energy consumption of a bed cooled room and a standard room were monitored under practical conditions on two manual picking farms with a multi-layer bed
44 MUSHROOM BUSINESS
cooling system for nine months – i.e. four rooms in total. Bed cooling on a single-layer system was not examined, as there is no reference available for a single-layer system without bed cooling. In rooms with bed cooling, energy is consumed by two devices: the climate unit and the bed cooling. Additional to energy measurements on the bed cooling, the energy consumption of the components of the climate unit was also directly measured using a data logger developed specifically for this purpose. The energy consumption in the rooms with bed cooling (climate unit + bed cooling) was then compared with the energy consumption of the standard rooms (climate unit only). Unfortunately, during analysis of the measurement data various factors (techni- cal, practical) meant that the data was not always compete or reliable. However, by eliminating, combining or repairing certain data it was still possible to log between four and six cropping cycles per room and use the measurements for analysis. The results have been incorporated into this article.
Breakdown of results of energy consumption
The table below shows the energy con- sumption broken down over the various
components. For the purposes of compar- ison, the energy consumption has been converted into a value per m2 surface area.
of growing
Fan: As bed cooling can accelerate growth by around three days, and less forced cooling is required, it follows logically that less energy is needed for the fan with bed cooling. This is indeed the case on farm 2, (the fact that the same does not apply on farm 1 relates to a number of cycles producing chestnut mushrooms). Cooling coil: As bed cooling provides some of the cooling effect on the compost, less cooling will be required from the cooling coil. This was the case on both farms. Heating: As with bed cooling a higher air temperature is used after filling (which gives faster colonisation and accelerated growth), more heating will be necessary. In addition, as the underneath of the bed cooling is only poorly insulated, extra heating will also be needed to maintain the higher air temperature. This was also the case on both farms. Bed cooling therefore results in a higher heating demand. Lighting: Despite slightly more energy for lighting being needed in the bed cooling rooms, there cannot be substantiated. As lighting is mainly needed for filling, empty-
Average energy per m2 Average energy per m2
Average energy per m2 Average energy per m2
standard room farm 1 bed cooling room farm
standard room farm 2 bed cooling room farm 2
36,0 1,000 12,553 9,008 0,390 13,388 0,000 0,000 0,000 35,9 1,251 9,975 10,258 0,428 16,652 0,000 3,094 0,575
31,2 0,944 12,808 10,074 0,732 13,417 1,767 0,000 0,000 27,6 0,921 9,209 11,012 0,874 14,482 0,914 3,766 0,659
Cycle length in days Fan kWh-e
Cooling kWh-Th Heating kWh-Th Lighting kWh-e Litres water
Humidifying kWh-Th
Bed cooling kWh-Th Bed cooling pump kWh-e
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