Published
19th FEBRUARI 2007
10th APRIL 2007
 


10th APRIL, 3rd DAY OF EASTER
In week 11, we have harvested the first vines. The fruit’s weight with some 100 grams was not quite as good as expected. At the moment, the fruit’s weight fortunately is increasing, and in the meantime we have picked the first 2 to 3 vines. The quality is great. In general, you can say the plants are growing very well.

Heat excess
The first two months of the crop have elapsed with not enough light, statistically speaking, but during the last few weeks we really cannot complain of this anymore. By now, considerable radiation of some 750 W/m2 maximum is involved at the warmest time of the day. This also then gives us a considerable excess of heat in the greenhouse.
We should be able to eliminate a part of this using adiabatic cooling (cooling by evaporation). Another option is to use mechanical cooling via the air treatment boxes. However considering the vegetative, growth-related state of the crop, and the very quick flowering, we decided to only vent “as usual” for the time being.
Obviously, this is of some consequence to the CO2 content. At the highest opening point of the vents, this slumps to a level of ca. 500 ppm. The fact that our variable CO2-dosing installation is not operational yet does not have a positive effect in this respect. Luckily enough, this part will be delivered on Friday, the 13th (!?) of April.

Strategy
Once the CO2 dosing installation is in operation, we want to implement the following strategy. First we have to get the plants to a more generative state by dosing more CO2. After that, halfway through the summer we want to use the adiabatic cooling or humidification to guide the heavily-loaded plants through summer at a good balance.
We are saving the cold we will have collected in the aquifers in the meantime for the second half of the crop to limit the high 24 hour temperatures then occurring. Adiabatic cooling then works at a less optimum level as the outside air then holds considerably more humidity than in the period before the longest day. In this way, we think we can “help” the plants during those times they need it the most.

New questions
Over the last weeks, we have spoken to quite a few people about conditioned growing methods. Our conclusion is that there are still very differing opinions about what the optimum climate for the plant really is. The longer we talk about this, the more questions arise. It is not that simple after all! We will not have any unequivocal answers that quickly anyway. For the time being, we will stick firmly with our mapped-out strategy… to be continued!



19 FEBRUARY 2007
Our plants were placed into our new 47,000 m2-size greenhouse on 5th December. In the meantime, the 5th vine is now flowering fully. The lower vines are also starting to swell nicely. Generally, we find that plants are growing well.
It was quite exciting right from the point of planting onwards. There were the usual uncertainties,  such as the fact we wanted to heat the greenhouse with a maximum supply temperature of CV water of 50 degrees. We use the pipe network and 248 air treatment units for this. This temperature is the maximum a heat pump can produce with an acceptable performance ratio between electricity input on the one hand and heat output on the other hand. In case of any heat shortage, the additional heat was to be supplied by the nearest existing site. There is also no supplementary heat producer. In the Aircokas, we therefore have to completely do this thermically with a 4.2 MW heat pump exchanger.

At this moment, our conclusions are as follows:
1. It is possible to heat the greenhouse with our heat pump exchanger and the accompanying heat distribution system. It should of course be no longer any problem once the wells are full up, like last year. You have to consider with this though that we did not have a proper winter yet, except for a few snowfalls.
2. Temperature distribution, as far as it is achieved in the greenhouse, is very acceptable. Only a few differences between plants are obvious.
3. If the sun shines strongly, there is strong radiation immediately. For the time being, we are still just ventilating away the excess heat “as usual”. CO2 is still no problem, as it is supplied by the boiler of the existing site. Shortly, the “cooling season” will start however, and we will start working with adiabatic cooling or with the humidification installation. We can also use mechanical cooling via the air treatment units.

It will then take quite some more time to clearly establish what the correct cooling strategy is. I will report more about this shortly – for the time being, we are now coming up to the first harvest!