On the blogby Alfred
July 25 2018

All you need to know about compressor-powered wine cellaring cooling systems – Part 2

by Alfred

As we promised last week, the Alfred blog presents, this week, the second part of the interview with Mr. Normand Blais, ex-professor at the École Polytechnique de Montréal on the subject of compressor-powered wine cellar cooling systems. To read the first part of the interview click here!

 

Alfred:
How does the continuous cycle of starts and stops affect the uniformity of the overall temperature of the cellar?

 

Normand Brais:
This creates inevitable cycles of cooling, followed by gradual reheating which is far from what is found in a natural wine cellar. I visited quite a few wine cellars in Europe, and these cellars are very profound and often built deep underground in either stones or clay, with a natural humidity level and a constant temperature. This temperature will vary depending on the seasonal temperature, but these changes happen over very long periods. I was in Italy last fall and all the temperatures in the wine cellars visited were synonymous with the current seasonal climate. During the winter season, these cellars reach a temperature of around 14 °C, and during the summer, around 16 to 17 °C. These winemakers were adamant about the fact that this change was not perceptible at all due to the fact that it happened over such a long period of time. It is also important to note that this small variation in temperature happens in very humid cellars, which prevents the corks from drying and, therefore, offers ideal conservation conditions.

 

Alfred:
These observations on natural wine cellars are quite different from what was observed concerning “mechanized” wine cellars, where the focus is often centered around a very precise temperature of 12 °C that must be maintained at all costs, disregarding almost fully the “humidity” factor…

 

Normand Brais:
These compressors dry up the air in the cellar and, regarding the energy required to condense the water that must then be evacuated, this process is extremely energy consuming. This is a very important point that warrants more attention: the changes between the different water states requires an extreme amount of energy.

As an example, a cauldron filled with water that is brought to ebullition will not have its temperature change; it will always remain at 100 °C. Why? Because all the energy is used for this change from the liquid to its gaseous state, which requires a very high amount of energy. This process is quite simple: when the temperature is below 100 °C, only 1 calorie of energy must be used to bring up the temperature of water by 1 °C. To bring water from its liquid state to its vaporous state, 1000 calories are needed, which is 1000 times more energy required for the same quantity of water. When a compressor needs to maintain a high humidity filled cellar while also cooling the air, the system will need to work 4000 times harder than when trying to cool air that is already dry at its initial state.

This is why these compressor based systems are very powerful and also quite energy consuming because this energy isn’t really used to cool the air in the cellar, but more so used to remove the condensation from the cellar. Now, to illustrate the completely ridiculous aspect of this element, today, many cellars are equipped with humidification devices (that are also consuming a lot of energy) that counteract what these compressor based systems are doing by trying to humidify the cellar!

The best analogy to describe this absurdity is having water be poured in a bath where the drain isn’t blocked, while also having to constantly pour more and more water to compensate for the water that is evacuated. On one side, the compressor system works to remove all condensation from the cellar and, on the other hand, the humidification devices generate more and more water to keep the humidity levels at acceptable levels. These two machines are, quite literally, working against one another (laughs). This makes no sense; it is just like driving your car and keeping the manual brake on!

 

Alfred:
What is the solution, then?

 

Normand Brais:
The cooling liquid would need to be very close to the temperature at which the cellar needs to be operated. As an example, if the cellar needs to be maintained at 15 °C and this cooling source is at 14 °C, there would never be any condensation of the water, which would remove the need to artificially add more humidity.

This solution already exists on the market. The CUBE system is the first of its type, as it allows the elimination of the dry air problem in the cellar that is sometimes quite hard to grasp. In the context of a wine cellar, dry air is one of the worst things that could happen, but so is reaching very high humidity levels that would create condensation. It is precisely this problem that CUBE resolves by adjusting the temperature of its cold source to never create condensation.

In summary, the system brings forth these three advantages :

1)    The humidity in the cellar is not fully removed by the cooling system;
2)    No need to drain the water created by condensation as this process simply never happens;
3)    The system uses very low levels of energy by never passing the famous 1000 calories per gram mark. It is not only fantastic for the quality of the conditions of a wine cellar, but also for our planet!

 

Alfred:
The fact that the CUBE system can adapt the temperature of its cold source allows it to continuously function?

 

Normand Brais:
Exactly, the system is never interrupted. The temperature is therefore very stable and enables an environment where wine can age in the best of conditions at all times.

 

Alfred:
How does this function? Is there a compressor inside this system?

 

Normand Brais:
This system contains no compressor. In fact, it is a semiconductor technology, inspired by the Peltier effect. Nowadays, all systems use transistors and diodes (semiconductors), which allows us to not have to wait for five minutes every time we want to open the radio. The reliability of these systems is much better than in the past. The e-cool technology found in the CUBE works the same way, by having one side of the source element creating cold, and the other side, heat.

Thermoelectric systems have existed for quite a long time, but its core elements have been drastically improved by increasing the quality of the materials that were used and by using purer metals which allow for the production of source elements that are very performant and that can last for a much longer period.

Also, contrary to traditional mechanical systems, thermoelectric systems such as the CUBE have no moving parts that partake in the production of the cool and the heat, as there is only a closed water circuit, which offers an immense improvement to the lasting capabilities of this improved technology.

 

Alfred:
Only a few years ago, thermoelectric systems did not always benefit from a very good reputation in regards to efficiency… Have all those changes mentioned earlier affected the technology in such a way that it is a now very potent, reliable and durable solution?

 

Normand Brais:
Indeed, a better quality for materials, purer metals, and better assembly lines have impacted the thermoelectric market in a huge way. The demand is now much higher, with the technological implications related to cooling down very high performing pieces of equipment found in high-end computers.

 

Alfred:
Concerning the precision of the sensors of temperatures in systems such as the CUBE – are they more performant if the control of the temperature is optimized?

 

Normand Brais:
Yes, in fact, it is much easier to be precise with a thermoelectric product such as the CUBE. The measuring systems can be much more precise, while the compressor-based systems cannot. As an example, if a sensor is placed inside a compressor powered wine cellar with the task of maintaining the system at 15 °C with ±0,1 °C of difference allowed (14,9 /15,1 °C), the system would be so powerful that it would enable itself for 20 seconds and would then shut down for another 30 seconds, endlessly repeating this cycle.

 

Alfred:
So, this means that if a sensor in a compressor powered wine cellar is too precise, it would directly affect the longevity of the system?

 

Normand Brais:
With the extraordinary amounts of starts and stops, it would probably last for a few months, at best. It is a system that simply has no middle ground: it has to be on, or it has to be off.

 

Alfred:
What is your opinion on sensors directly placed inside a bottle? Is it efficient and does it benefit the wine?

 

Normand Brais:
It is, in fact, not very effective because placing this sensor in the bottle simply delays the activation of the system, as the bottle must fully change temperature before the system understands that the temperature has changed in the cellar. Specifically, if I wish to keep my bottle at 15 °C, the system will stop functioning only when my bottle will reach this specific temperature. Even if the overall temperature of the cellar is at 16 °C, it can take hours before the bottle reaches the temperature of 16 °C. This means that the cellar is most likely, as a whole, at a much higher temperature than the 16 °C of this specific bottle, which adds a delay in the reaction of the system in something that is often referred to as “inertia”.

 

Alfred:
Is it then counterproductive to use sensors inside bottles to try to create a stable environment in a wine cellar?

 

Normand Brais:
Yes. Using a sensor creates cycles that are much more pronounced, which increases the highs and lows of temperature in the cellar. This is, at first glance, something that seems to be a good idea but the laws of physics quickly remind us that is not quite one! … (laughs)

 

Alfred:
Do you have a wine cellar at home?

 

Normand Brais:
Yes, with around 1500 to 2000 bottles.

 

Alfred:
In which type of environment are they stored?

 

Normand Brais:
In my basement, where no windows are found and where walls are very well isolated, with the goal of keeping the most stable temperature possible and by also avoiding the creation of dry environment during the winter.

 

Alfred:
Are most of your bottles kept for a shorter or a longer aging period?

 

Normand Brais:
Just like everyone, I have a few long terms projects and wines that are ready to be tested immediately. Most of my wines are to be aged for less than 10 years. I have mostly 500 to 750 bottles to keep for a longer period, with the rest of them to be enjoyed in the upcoming 10 years.

 

Alfred:
Your last trip in Italy visiting various wine cellars must have validated all your thought on elaborating your own wine cellar…

 

Normand Brais:
Absolutely, I tasted wines that were more than 50 years old that were simply incredible, a proof that the conditions in which they aged were impeccable.


Alfred:
Have you had to chance to compare the quality of the conditions of your cellar? For example, tasting the same wine, of the same vintage, but originating from two different cellars (one being from your own)?

 

Normand Brais:
I never had this opportunity. One thing is certain; when it comes to the quality of the cork, it is almost instantly possible to understand in which conditions the wine was aged in. When the cork simply disintegrates in tiny pieces, or is very dry at the top but soaked at the bottom, it usually is already a good sign for the quality of the product that we are about to taste!

___

PHOTO:
Normand Brais: former teacher at l’École Polytechnique de Montréal, mechanical engineer, owner of a master degree in aerothermal and a doctorate in nuclear engineering.

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