Jesús Areso Salinas – Building towers to trigger rain, to help nature sweat and cool

A conversation with Jesús Areso Salinas, retired from work as patent examiner at the European Patent Office and now active with his project to fight climate change combining water, katabatic tower and moisture. Another record-breaking summer in the global north, where temperature records were shattered repeatedly, prompts us to ask: is there a sustainable future for places like the Mediterranean? Jesús wondered how does nature cool? and, crucially, could we help nature kickstart the cooling of ambient air?”

Imagine cooling our surroundings during a heatwave—cooling town squares, vegetable gardens, or farms on a small scale. What if, over time, this approach spreads, with more people cooling their surroundings, allowing plants and trees to continue growing through the summer and helping to cool the air? Could this restoration of local cooling contribute to rebalancing water cycles, bringing back summer rains, and even creating a lasting cooling effect? These are big, almost magical questions, and they are exactly why we tackle them here with Jesús, an engineer turned permaculture expert, who is now building towers to help nature “sweat” and cool.

Sure, we could retreat to air-conditioned spaces, but air conditioners only worsen the problem by using energy to move heat from inside to outside without solving anything at its core. And what about plants, trees, and animals? They need a humid, comfortable environment to thrive, yet during hot, dry summers, they’re focused on survival rather than growth—or the cooling process essential to their function. Mediterranean farmers, in particular, take note: during the peak of summer, your plants and trees often stop growing because it’s too hot and dry.

So, how does nature cool itself? Through transpiration, plants and trees release moisture, which cools the surrounding air. However, as heatwaves become stronger, it’s often too hot for them to function, meaning they can neither grow nor cool the air. This lack of cooling is a problem farmers and investors need to understand—especially those in warmer climates, where plants and trees may be unable to photosynthesize or grow for weeks. Cooling ambient air is essential, and air conditioning isn’t the answer.

LISTEN TO THE CONVERSATION ON:

HOW DOES NATURE COOL? BY SWEATING

Jesús explains the importance of evaporation in cooling, comparing it to the cooling power of trees and forests.

”The other way of cooling is the way nature does it. How do they do it? Simply, they use water, and they evaporate it. It’s not very far away from us because we do it as human beings. When we sweat, we cool ourselves. This has been a success of human evolution. This is sweating.” Jesús Areso Salinas

”This is the way that the trees and the forests do it. They are able to cool the ambient, and they cool gigawatts of power by evaporating water. So, I was already working on these ideas, and I came to this concept that I call the katabatic tower. But basically, it’s a very efficient way of evaporating water in order to support, for example, a garden or the plants or a square in a town, for example, or a park in a city.” Jesús Areso Salinas

[…] I met a very interesting group of very motivated young men, much younger than me, certainly who were worried for the life around them, for the planet, but they were taking care of the trees and the plants. And then I learned the importance of the soil…” Jesús Areso Salinas

PLANTS AND TREES NEED A LOWER TEMPERATURE TO THRIVE. IN WARMER CLIMATES, THEY CANNOT PHOTOSENSITISE FOR MANY WEEKS AT A TIME AND THUS DO NOT GROW.

Summers and heatwaves are quite detrimental for plants, as they might go for weeks without any growth. Without the necessary nutrients to grow, produce fruits, or generate flowers.

”The first threshold, which is very, very dry, before this threshold, the plant is in what we call hydric stress. It doesn’t breathe. It’s like you and me; when it’s 45 degrees, we can’t do anything. You can drink water, but you cannot work. Then, if the humidity raises a little rest and you go beyond this first threshold, then the plant can’t produce photosynthesis, and with that, it is able to transform CO2 from the air into very complex molecules that are charged with energy. These molecules are, let’s say, what we can eat, sucrose, for example, saccharose, and other molecules.” Jesús Areso Salinas

”In the second step, the plant needs to use this to eat these molecules in order to grow. And when we say grow, we refer to cellular growth. The cells of the plants grow either because they increase the volume and the mass or because they divide into two molecules, and the mother cells become two or more daughter cells that grow. In order to do this growth, they eat these molecules. They use this energy that they have produced in photosynthesis. But they can only do it if there is a certain hydrostatic pressure inside of the cell. If there is not this pressure, the cell is somehow flaccid, and it cannot grow, even though the food is around. These molecules, charged with energy, are around, but it cannot use it, and it cannot divide, either. It has to wait until the second threshold is overcome.” Jesús Areso Salinas

WITH STRONGER HEATWAVES IT IS GETTING TOO HOT FOR PLANTS AND TREES TO FUNCTION, AND FOR WEEKS OR MONTHS THEY CAN’T GROW AND CAN’T COOL.

The plant thrives in a highly humid environment, where it grows during the day, especially when it rains. This allows for photosynthesis and turgor pressure, both essential for its growth. Conversely, if the conditions are very dry and hot during a heatwave, even at night, the plant struggles to reach its growth potential.

”Our problem is this horrible heat that is coming, these heatwaves that are more recurrent and bigger, and you want to have something precisely there. And I realized that actually this energy, which is so destructive, is thermic energy that is making hell in our cities and in our forests. This energy is actually the driver of our engine. So, I’m using our problem as the source of energy for a solution.” Jesús Areso Salinas

”The drought, the heatwaves—I don’t have any doubt that they are going to be more, even more intense. Now we are worried because we have reached somewhere in the world, 52. Sometimes we will reach 55, maybe 58. What now we call a heatwave is going to be the normal summer then, and when they will have a heatwave, this will probably mean that, if you are outside, you die.” Jesús Areso Salinas

”And this second threshold- because temperature and relative humidity are very, very interlinked, normally- is only reached late at night; when the temperature goes to a very minimum, then the relative humidity goes to its maximum, and the second thread is overcome, and then the plant finally can use this food that has been produced during photosynthesis and grow.” Jesús Areso Salinas

EARLY PROTOTYPES SHOW IT IS POSSIBLE TO COOL AMBIENT AIR

Jesus emphasizes the potential of the katabatic tower to create a siphon effect, drawing cool air downwards and enhancing evaporation.

”Mothers and grandmothers taught us to hang the clothes vertically because this is the most efficient way to dry a cloth. It’s an efficient way to produce evaporation. And starting from there, I thought, what is going on here? What happens when you have a vertical geometry, which is like a sheet, a wet sheet hanging, compared to a horizontal geometry for evaporation? For example, the surface of the sea is horizontal. It is not a very efficient way of evaporating.” Jesús Areso Salinas

”When the wet cloth is in contact, in microscopic contact with a coat of air, the air does this process I told you earlier. It takes some molecules of water to jump into there, cooling it immediately. And the fourth, the cloth becomes a little bit drier. But the air in close contact with it is wetter and colder. It’s much colder. And because it is colder and gases, when they are cold, they compact and compress. Because it becomes heavier. So, it glides down along the wet, and it creates a current of air moving downward. And this movement of the air is also very good for the renovation, because in order to dry, you need to renovate constantly. So that’s why the clothes dry much better when it is windy. But if there is no wind and your clothes are vertical, they create their own wind downwards. And if you put your hand below, even if you are inside your house, you are going to feel it.” Jesús Areso Salinas

HOW DO WE COOL OUTSIDE AND INSIDE (AIR CONDITIONERS ARE NOT A SOLUTION)

We need to always look at nature and try to do as they do

”Air conditioners are good machines for us, but if you look at the whole system from the outside, air conditioners are part of the problem. Because what an air conditioner does is take heat from your cool house; remove the heat and put it outside where it is very hot. How they do it is clever way of engineering. But to do it, you need to add energy to it. In other words, if I’m taking five units of energy from my house and put it, maybe at 20 degrees, and put it outside where it is 40 degrees, I need to add one unit of energy. So, if you look at the whole system, you have added energy to the global system.” Jesús Areso Salinas

OTHER POINTS DISCUSSED

Koen and Jesús also talked about

More tests are needed at scale
The challenges of building large-scale katabatic towers and the need for collaboration
The concept of reverse waterfalls

LINKS:

LINKED INTERVIEWS:

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The above references an opinion and is for information and educational purposes only. It is not intended to be investment advice. Seek a duly licensed professional for investment advice.

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