A desire to teach students to model online prompted senior researcher Niels Holst from the Department of Agroecology at Aarhus University to set up an online PhD course. The course, which started as a didactic experiment, has over the last 10 years taught students from all over the world how to model.

“My students have been able to model pretty much anything. And even though the course was free, it required a lot of work. The course was standardised at 10 ECTS credits at the PhD school, and it corresponds to 270 working hours, so you did not get results easily. But everyone who has completed the course succeeded in building a model of their system,” says Niels Holst, who has also written several scientific articles with the students.

“The experiment convinced me that the way course was conducted was not the most effective. So now I am instead producing shorter do-it-yourself videos and inviting students to visit my lab.”

That offer has been accepted by a lot of students. So far, 12 external PhD students have visited Niels Holst’s laboratory in Flakkebjerg - typically for 3-6 months - and he has collaborated with just as many virtually.

Universal Simulator

As part of the course, Niels Holst - who majored in biology and computer science - developed a tool called Universal Simulator.

“Universal Simulator is an open-source tool I created. It can model systems. And that's the tool my students use. You can simply download the software and use it on the models that have been published so far. And Universal Simulator is growing all the time, because all the models that the students manage to get published, become a part of this open-source tool, ”says Niels Holst.

And it is not only students who have the privilege to use Universal Simulator and collaborate with Niels Holst. 

"Together with the Danish Technological Institute, I have been involved in two projects that deal with greenhouses in Denmark, where they have implemented Universal Simulator and created a commercial product that can be used by Danish greenhouse gardeners," says Niels Holst.

The Virtual Greenhouse

The collaboration with the Danish Technological Institute led to the Virtual Greenhouse, which is a model-based online tool that can calculate the effect of new initiatives on energy, climate, and plant yields in greenhouses.

“The Virtual Greenhouse is a model implemented in Universal Simulator. Here, the gardener and a consultant can build a greenhouse on his computer, and the model can show what happens if, for example, you put up new curtains or insulate better. The computer model can also show what happens to the microclimate and plant growth if, for example, you change the lamps,” says Niels Holst.

In other words, the model can help greenhouse gardeners test the effects of new technologies or change plant cultures virtually before investing. The model can compare the greenhouses' current energy consumption and plant yield with consumption and yield from changes or introduction of new technologies.

Academic leader at the Danish Technological Institute Jesper Aaslyng has, with Niels Holst, been responsible for the collaboration between Aarhus University and the Danish Technological Institute.

"In fact, there are two tools we have developed. There is the Virtual Greenhouse and Infogrow, and together they make up what we call Digital Twin Greenhouse,” he says. 

InfoGrow

The Virtual Greenhouse is thus part of a two-part solution at the Danish Technological Institute, which is called Digital Twin Greenhouse. The second part is called InfoGrow. And here too, Niels Holst and Universal Simulator have played an important role.

“The same model that is used in the Virtual Greenhouse is part of an online system called InfoGrow. Here, the model runs all the time on a web-based platform that gardeners can connect their greenhouses to,” explains Niels Holst. 

When the greenhouse is connected to InfoGrow, the gardener can use a control panel to keep track of how photosynthesis is going, temperature, heat consumption, etc. InfoGrow thus functions as a decision support tool for optimising the climate settings in Danish greenhouses. 

In short, the idea behind Digital Twin Greenhouse and the two tools is that you not only have a climate computer that can register the physical conditions such as temperature and CO₂, but that it can also tell how the plant growth is. For example, we have used mathematical models to calculate how the photosynthesis is due to the climate in the greenhouse. Just as we can calculate energy consumption. In this way, the greenhouse gardeners can get coherent data for both energy consumption and production,” explains Jesper Aaslyng.

From open source to commercial product

But how can the Danish Technological Institute sell something that comes from an open-source tool from Aarhus University?

“The business idea is quite interesting, because how can you sell a service that is based on an open-source scientific background? You can only do that because the interface to my tool is so scientific and looks scientific. It is not something a gardener will be able to use or something others can use for decision support. You can use my tool for research. What the Danish Technological Institute has done is that they have made a commercial packaging, in which Universal Simulator lays hidden,” explains Niels Holst.

So, it is not Niels Holst's Universal Simulator, the Danish Technological Institute sells, but rather digital and virtual systems, which have the model as a background, but also have a large digital structure on top, which makes the results understandable and not least useful for greenhouse gardeners.

“We have worked closely with Niels Holst and Aarhus University. There is both a research and commercial angle on this project. We have made a commercial product, but behind it is this open-source tool that Niels Holst has created at Aarhus University. But the rest of the framework is not open source. As Digital Twin Greenhouse is based on an open-source tool, the opportunities for collaboration internationally increase. And we also have plans to move outside the Danish borders with the two software systems as soon as they have been tested in the three Danish pilot greenhouses,” says Jesper Aaslyng.

The future looks bright

So far, Digital Twin Greenhouse has been implemented in three Danish greenhouses, and here they will undergo a trial period before they can be expanded to more greenhouses in Denmark and the Netherlands, respectively.

“We also see a great opportunity in implementing these programs in vertical farms. It is a completely new area, which is a new way of farming, and they would be able to get good use out of these two products. Therefore, our collaboration with Aarhus University will continue in the future. Among other things, the Department of Food has become part of the project in relation to research into plant physiological aspects. So, it is an ongoing collaboration that is constantly evolving for the benefit of us and the university,” says Jepser Aaslyng.

And Niels Holst has no doubt that the collaboration will continue, and that Universal Simulator will continue to launch more new collaborations in the future.

“Although you cannot immediately see my model when you look at the two systems from the Danish Technological Institute, neither of them would exist without Universal Simulator. And when I look at the PhD students I have worked with, I have no doubt that not only will many good research results come out of the model, but also more exciting and research-lucrative collaborations in the future,” he says.