Get in contact
Would you like to make an appointment with one of our specialists? Please fill out the form below, and we will contact you within one business day to schedule it.
"*" indicates required fields
In greenhouse horticulture, the focus is gradually shifting. For a long time, everything revolved around capacity — more heat, more power, more technology. Now, the emphasis is increasingly on control. Not what you can install, but how you deal with peaks and fluctuations in supply and demand. Several years ago, this development prompted Genap to start developing insulated cold and heat storage systems, in which energy can be buffered in the form of temperature-controlled water.
That development comes together in a project in Zeeland, where Genap is involved in the realization of a cold storage buffer in an existing greenhouse. The starting point came from Harvest House, which, together with CombiCoop, is exploring ways to become more sustainable without losing sight of practical reality. The ambition was clear: cut gas consumption in half, reduce CO₂ emissions and at the same time increase production. But just as important was the condition attached to it: it had to work in greenhouses that already exist today. “Current greenhouses are already highly efficient,” says Arjan Flikweert of CombiCoop. “So there was little point in designing something completely new. The real question was: what can we improve without starting all over again?”
From closed greenhouse to a new challenge
That question led to a fundamental choice in the cultivation strategy. By keeping the greenhouse as closed as possible, CO₂ is retained more effectively and unnecessary heat loss is prevented. On paper, that is a logical step, but in practice it immediately creates a new problem. “If you keep everything closed, humidity levels become too high,” Flikweert explains. “Especially in winter, that becomes a limiting factor. You need to be able to actively reduce the moisture.”
The challenge therefore shifts. It is no longer just about retaining energy, but about maintaining a controllable climate within a closed system. Dehumidification becomes essential, and for that, cooling is required. That cooling can be produced with a heat pump, but that alone does not solve the issue. “The demand for cooling constantly fluctuates,” he says. “At one moment you need a lot, the next almost nothing. If you want to respond directly to that, you end up with a relatively large and expensive installation that is constantly switching on and off. That is neither efficient nor stable.” This reveals an important insight: the problem is not the available capacity, but the timing of when energy is needed.
Storing cold instead of producing it on demand
From that realization came the idea of separating cooling demand from cooling production. Instead of producing cooling only when needed, it could be temporarily stored. The question therefore changed from ‘how do we create cooling?’ to ‘how do we manage it?’ That was also the point at which Genap’s insulated silos entered the picture. “That’s when everything quickly started to fall into place,” says Flikweert. “We were talking about a buffer, and then it turned out that the solution already existed. After that, it becomes a matter of integrating it properly into your system.”
The silos function as storage for cold water, but their strength lies in the way that storage takes place. By introducing the water gradually, thermal layering is created, allowing cold and warmer water to separate naturally. “The cold water stays at the bottom, the warmer water at the top,” he explains. “And they remain separated because you do not mix them. That means you can use exactly what you need, when you need it.” This characteristic makes it possible to better align supply and demand. The heat pump no longer has to constantly respond to peaks in cooling demand but can run more steadily while the buffer absorbs the fluctuations. “Without a buffer, the system continuously switches on and off,” says Flikweert. “With a buffer, you create stability within the installation.”
First results and the reality of system control
The system has now completed its first winter and spring, providing enough experience to evaluate the results. “It works,” says Flikweert soberly. “We achieved the objectives. Less gas and lower CO₂ emissions. But you have to stay realistic: that is the result of the complete system, not one individual component.” At the same time, it is clear that the installation is not yet ‘finished’. The system offers many control possibilities, but a full year is needed to truly understand and optimise them.
"The greatest gains are not found in adding more technology, but in using it more intelligently."
Arjan Flikweert, CombiCoop
From solution to system
With these experiences, the focus is now gradually shifting from realization to optimization. Not by redesigning the system, but by making smarter use of what is already there. For example, the team is looking at using outside air more intelligently as an additional cooling source and at the possibility of storing heat as well. “That heat pump naturally produces two things,” says Flikweert. “Cooling and heat. And we do not always use the heat.”
A logical next step would therefore be applying a similar buffer on the warm side of the system, for example in the form of an additional insulated silo for heat storage. This would make it possible to temporarily store the generated heat and use it later when needed.
The project is therefore evolving from a solution for a single challenge into a broader energy system in which multiple energy flows come together.
What is being developed in Zeeland is not the final vision of the greenhouse of the future, but a working intermediate step. A system that demonstrates that the greatest gains are not found in adding more technology, but in using existing technology more intelligently — allowing growers to steer proactively instead of correcting afterwards.
