Research has long shown that fog with water droplets of a certain size can significantly reduce, or even entirely prevent, crop damage from frost or excessive heat damage. The reason for this is that the individual droplets in the mist cloud reflect the long-wavelength heat radiation that transmits energy from solid objects under these conditions.
For the reflecting to be effective the droplet size has to be roughly the same or even a little larger than the wavelength. In noticing these effects in the natural world, scientists and engineers have tried to replicate these results but attempts to date have quite often failed because of the inability to create the right size droplets relative to the radiation wavelength that will allow for reflectivity.
Protecting from freezing & burning
Top image shows grapes damaged by frost. Bottom shows grapes damaged by heat-stress from prolonged temperatures +40ºC for successive days.
In this interview with Dr Pratik Desai, he outlines how he and his colleagues have been able to achieve the creation of droplet sizes needed for reflectivity by use of their patented fluidic oscillator. What has also become apparent is that it is not just freezing conditions that can be guarded against, but also hot conditions where sustained hot temperatures can burn crops leaving them with seasonal of permanent damage.
Although currently in the R&D stage, the ramifications for this technology as a crop guard in extreme climate conditions are potentially huge. For the wine industry, in particular, it may offer a solution to late-season frost damage as well as sustained summer hot days where temperatures exceed 35ºC.
Interview transcript: Dr Pratik Desai
Nick Breeze (NB): Can you tell me, in terms of crop protection, what was the problem you set out to solve with your technology?
Dr. Pratik Desai (PD): The problems were based on frost protection, fire preventions, especially targeting the solution to the crops, rather than targeting everything around it rather than the crops itself.
NB: You mention fire protection but one of the impacts we are seeing now are increasing temperatures over 35ºC for sustained periods. Is this something that this technology can also tackle?
PD: Yes, it can do. The approach we are talking about takes care of the latent heat of the system and therefore it is a mitigation against high temperatures, as well as fires and frost as well.
NB: Can you explain, how it actually protects the plant?
PD: What we do is something called the design nanodroplet approach and the way we do it is millions of these tiny droplets are produced along with wet gas. This gas can then be activated to be targeted towards the plant.
What happens with that is that it creates this buffer zone where water is one of the best methods of having latent heat. Therefore it can take in a lot of temperature or store a lot of cold as well, so the major point is that it will act as a buffer for moderating the temperatures either way, whether it be too cold or too hot, and that should protect the plant easily.
NB: Thinking specifically about viticulture, we are seeing how vulnerable vines are to impacts from climate extremes, so you are saying that this could be a frost protector, or, it could be a heat stress protector?
PD: Absolutely. This is a very likely approach. It has been used in many systems around the world for this purpose. The only problem is that they are quite expensive to run operationally and capital intensive as well?
Mine is potentially a cheaper and more environmentally sustainable approach for this same process.
NB: Cost is very important but also we are talking about using water ultimately. How much water do you need for this?
PD: So, what we found is that using the current approach for a whole hour we produce droplets of about 300 nanometers to 3 microns in size, and we are using, in an hour, 250 millilitres of water but producing a gas throughput of 16,000 litres of gas per hour.
NB: Is there any way at this stage to measure how much water you need for any given area, such as an acre, a hectare, etcetera?
PD: If we were using this I suspect it would be about 200mm per hour per unit. There is some R&D required based on specific terroir and climate and weather so that you know exactly what the air temperatures are and how much you need to do for protecting the plants.
NB: You just mentioned R&D; what is the current status of this technology?
PD: The current status is, because we are a market pull and not market push company, we have been focusing on certain aspects. One of these aspects for the Desai MMD program is the fact that at the moment I can produce 16,000 litres of microdroplet mist per hour using 250mm of water per hour. That produces 300 nanometers to 3 microns of droplets in size. It is highly scalable, it can be multiplexed and it depends on each specific operational requirement that we can actually get down costs based on how many and where we install it.
NB: On this scalability issue, you go to some vineyards and the parcel may be an acre, and at another, a hundred hectares or more. Do these scales concern you?
PD: No, it would not be a problem but there is, as I said, some R&D work and design work required to specifically address this problem. However, once it is addressed, we have the expertise with a wide range of partners, as well as our own to design systems to be as inexpensive as possible and multiplexed but it will need specific inputs from the end-user to what is required and then we can do it fairly easily.
NB: Moving straight on to deployment, how easy is it to deploy?
PD: Currently the fluidic oscillator that I have invented with my colleague in Sheffield can be used with a very low-pressure drop of about 100 millibars. What that actually translates to is that it could be deployed with a blower and photovoltaic array of batteries. Therefore, you can multiplex these units at each point source where you require them.
This way your costs are lower and it is also a clean and sustainable process.
NB: You don’t really see this as being prohibitively expensive in cost?
PD: The R&D we need to do will be slightly expensive to begin with, relatively speaking, but the scope of the problem and the scale of the problem can be addressed.
NB: Is this a technology that could be put in place and activated by something like a satellite weather station via an app or is it a manual system?
PD: It can be designed to target an Internet of Things approach. So you don’t even need a satellite, you can use it via an app, or as required by the user.
NB: Is this something that can much further beyond the wine industry as all forms of agriculture are under threat from climate impacts?
PD: Absolutely, this is a very good point. It is a global system approach that I am trying to achieve with this and it should be able to work with every system depending on what is the cost/benefit analysis that they have found with the end-users but this is not a problem at all.
Additionally, what I have mentioned with the internet of things previously, now if you go for the approach of using a cheap sensor known as a thermal couple, sorry to get technical but if you use that, you can basically control it in an inexpensive way so therefor, whilst wine has a higher value product at the end, others systems need not have it yet it might still be sustainable to be controlled even electronically.
Current status of the technology is that is only being developed where there is an industry demand, or “pull”. Pratik emphasises that they do not wish to “push” their technology in any one direction because the potential uses for the fluidic oscillator span many different essential industries. These include in-door crop growing using nutrient mists and waste cleaning by separating toxic substances. UK company, Envisionation Limited has just partnered with Pratik and his team in order to further explore the potential uses of the fluidic oscillator, especially in the area of crop protection, and are currently looking for industry partners to accurate the research and development of the solution.