ENERGY SAVING
(+/- 14 °C) and cold (+/- 9 °C). The aquifer must obviously be suitable for this use, which is the case at many sites in the Netherlands. Depen- ding on the time of year, heat or cold from this source is used. A heat exchanger heats or cools the air for the growing rooms, then pumps it back again into the other source of storage. This makes it a closed system that leaves groundwa- ter levels intact.
If there is a high heating or cooling demand, the low level heat or cold provided by geothermal energy will not be able to meet the demand. In this case, additional heating or cooling is needed which is usually supplied by a heat pump. A heat pump works like a cooling unit which supplies heat on one side and cold on the other. The combination of geothermal energy and a heat pump does away with the need to use gas for heating. Gas is only required for cook out. Any surplus heat or cold from the heat pump can also be stored. As the sources in the ground must not be ther- mally influenced, an energy balance must be established over a period of five years between the heat and cold that is extracted from and returned to the sources. The energy requirement of a mushroom farm, in combination with summer and winter conditions, is however such that more heat is always pumped into the ground than cold. So part of this heat must always be removed in another way, or more cold has to be pumped back to the source. There are two possibilities: using a cooling tower or a dry cooler. These systems additionally cool the water before it is pumped back to the cold source. This method creates a thermal balance. A well-functioning geothermal installation
must therefore always be combined with a heat pump and a cooling tower or dry cooler.
Conclusion: proven energy saving techniques
Energy consumption in the mushroom sector on comparable farms can differ by even up to a factor of two. These disparities are not only caused by the technical installations, but also by the cultivation methods and behavioural factors. Behaviour here includes aspects such as regular and timely maintenance of cooling, heating and steaming units, filters, door seals, avoiding unnecessary energy consumption caused by leaving lights on and suchlike. The cultivation methods include good understanding of and insight into the evaporation process and ways to realise this using a minimum amount of energy. Setting a wider CO2 bandwidth will ensure better utilisation of outside air, resulting in energy savings. There are various tried and tested technical possibilities to save energy that can be used on any farm such as high efficiency boilers, energy efficient cooling systems with heat recovery, low temperature heating systems, frequency controllers, energy efficient climate control settings etc. In addition, recent years have seen the arrival of many new techniques which have also proven their suitability for application in mushroom growing. A geothermal energy storage system combined with a heat pump and cooling tower or dry cooler can make a valuable contribution to energy saving. Renewable energy systems such as PV solar panels and wood combustion, and in the near future probably spent mushroom compost combustors too, are also good options.
Schedule WKO (heat-cold storage) installation.
30 MUSHROOM BUSINESS
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