When it comes purely to sustainability, dehumidifying greenhouse air combined with harvesting heat is the best option. Ton van Dijk of Van Dijk heating has no doubt about that. A grower saves gas and uses 'green' electricity to run the heat pump that comes with it sustainably.
Yet not every grower immediately goes for AVS-C, the abbreviation for Active Ventilation System with heat harvest by Van Dijk heating. And this is logical, believes the sales manager. "In horticulture, there is always a balance between what is good for the environment and sustainable and what is cost-efficient and good for cultivation. The situation really differs per company."
Greenhouse as battery
Ton spoke at the Canadian Greenhouse Conference in early October about the Kas als Energiebron (Greenhouse as a Source of Energy), specifically not about the Dutch innovation program of the same name, but more broadly and internationally. After all, even outside the Dutch context, a greenhouse is a source of energy that is not yet optimally used. "Energy goes in via the sun, lights, and heating, but a lot of energy is also lost. The idea of the greenhouse as a battery is starting to catch on more and more."
With the right systems, it is possible, for example, to recover latent heat from moisture. "In the Netherlands, we have been involved in trials in various crops for years. Our AVS systems are used in chrysanthemum, gerbera, pepper, aubergine, and tomato cultivation, among others. As a result, we learn more and more about the most efficient use of technology because that's what it's all about. The gas savings you achieve are obvious. But a grower also has to be economical with electricity."
Highly topical
The Active Ventilation Systems, of which there is also a version without a cooling block and direct heat recovery in addition to the AVS-C on the market, are still being developed at Van Dijk heating. "But what it's also mainly about is fitting the technology optimally per location. The greenhouse the existing installations, such as the amount of lighting and the heating system, are often different for each company. That involves calculations, not to mention the financial calculations now that interest rates are higher and growers' investments are therefore also calculated in more detail."
For the people in the field at Van Dijk heating, it is important to inform as many people as possible about the (cultivation) technical possibilities. "Getting the complete principle of AVS to land well takes time, even still in the Netherlands." Compared to about five years ago, a lot has also changed. "The advance of LED lighting and the scaling back of pipe temperatures in combination with twice as well-insulating screens have a lot of effect on the greenhouse climate, and especially on humidity. That combination has made dehumidification extra topical."
AVS in LED cultivation
Helping plants
Trials within the Dutch innovation program Kas als Energiebron have shown the importance of insulating the greenhouse properly, as well as the importance of allowing the plant to continue evaporating. "In the Netherlands, we are good at constantly pushing the boundaries. You can see that in energy consumption. We can grow with less and less energy input. However, the plant must be able to continue evaporating. The right combination of techniques is crucial here. I think that is the most important improvement in the past five years."
In the Netherlands, dehumidification is currently topical because of the energy crisis and changing growing conditions. Investing in systems, like Van Dijk heating's, gives growers an extra tool in their cultivation. As a former growers, Ton understands all too well that this can sometimes be difficult. "It also requires a different way of growing the moment you choose AVS. You have to take time for that."
Look at quality
At Van Dijk heating, during the calculations, which they currently do a lot at the office in Bunnik and at the customer's coffee table, they always approach the issue from a cultivation perspective first. The special ACT configuration tool they have been working with for about a year now helps with this. "For example, we first look at the customer's demand and what capacity is optimal in this respect. From there, a further substantive discussion follows."
The sales manager notices that customers sometimes find it more difficult to calculate on the cultivation side. "For example, what value do you attach to no longer having to fight mildew and fungi? What does that provide? Seeing your crop lost to mold quickly costs more than the investment in dehumidification."
There is also a lot to gain with AVS in the quality of cultivation, Ton stresses. "Internationally, where saving energy because of lower costs is not always at the top of the lists yet, you see that it is precisely in that quality of cultivation that investments are made with AVS. In all the 'peripheral issues' besides energy saving, a lot of profit can already be made. On average, it is easily ten percent, depending on each location. Only then do sustainability and financial calculations with energy prices come into play."
Installation in AVS greenhouse façade
Internationally, people look to the Netherlands in terms of horticultural technology. Fossil-free cultivation, as is the ambition in the Netherlands in the coming years, seems even further away internationally. "There are other arguments at play when it comes to the choice of dehumidifiers, but the solutions are the same. That is why my message recently in Canada but actually also last year was: look around, realize that it is an investment for many years. Be aware of what is technically possible and how you can use it in your own location, especially in the longer term. That could be for new construction, but upgrading existing greenhouses certainly also offers opportunities."
For more information:
Ton van Dijk 
Van Dijk heating
Tel.: +31657298725
Email: [email protected]
www.vandijkheating.com