Did you know that the modern air-conditioner is just over a 100 years old? Juxtapose that against the fact that humans have been tackling the problem of staying cool for over 5000 years. The ancient Egyptians, the Greeks, the Romans, and closer home, the engineering leaders of the Indian medieval kings have all developed a number of power-free solutions to this problem - evaporative cooling by hanging wet reeds on windows, cooling using water piped from aqueducts, hand-held fans to produce moving air, and cooling towers that draw cool air up from underground channels while pushing warm air out are few of the techniques that have successfully withstood the test of time.
We believe that in our day and age, the solutions that will succeed are the ones that successfully maintain a balance between sustainability and the desire to tune every aspect of comfort to our individual needs, and what better way to do that than by learning lessons from history while staying rooted to the needs and aspirations of today.
Water as an effective heat remover
The human body dissipates ~ 100 watts of power at rest - a simple model for the body is a 100W bulb that emits heat as it glows. This heat needs to escape the system and the body achieves it by moving the heat from the inner regions to the surface of the skin through its 100,000-mile network of blood vessels. Once it gets there, sweat glands release water that moves the heat out of the body through evaporation. Water is a natural resource and one of its incredible properties is that it can remove a lot of heat when it evaporates. Around 2200 Joules/gm. The human body makes use of this property and breaks into a sweat anytime it needs cooling. One way to visualize this is to think of our body’s cooling system as a fan-less evaporative air cooler. We wanted BLU3 E20’s cooling technology to work in harmony with this phenomenon.
The role of air-flow in sweat evaporation
If you live in a humid city, you are probably sporting a puzzled “but everyone knows air coolers don’t work in humid conditions” look on your face. Would you be surprised if we tell you that humid cities like Chennai, Mumbai and Bangkok house some of the largest natural air-coolers in the world? This large natural air-cooler we are referring to is the beach - do you see any sweat on your body when you are at the beach even though the humidity in the air is extremely high. This is because the copious amounts of airflow at the beach works in harmony with the way our body tries to lose heat.
So, two factors matter when it comes to cooling effectiveness - how much air is flowing past you, and how much lower in temperature is that air in relation to your skin.
BLU3 E20 will blow several litres of air on your face every second at a temperature that is at least 5-6 degrees celsius cooler than your skin temperature. We have verified its effectiveness under extremely humid conditions, and are confident about its performance in cities like Bangkok, Manila, Mumbai, and Houston.
Why air cooling? Why not thermoelectric or Peltier coolers?
There are several miniaturized (and portable) refrigerators available in the market, and many of them use thermoelectric/Peltier coolers to remove heat. A Peltier element is made of an array of alternating semiconductors sandwiched between two pieces of ceramic. Current flowing through these semiconductors causes heat to be moved from one side of the element to the other with the direction of current deciding the direction of heat flow. These coolers are characterized by their coefficient of performance (COP) which is the ratio of heat transferred to electrical energy applied. A COP of 0.3 - 0.4 is a healthy metric when the expectation is to remove 15W of heat.
Thermoelectric/Peltier-based coolers work best when
- They are in direct and complete contact with the object they need to cool
- The object they are trying to cool is not constantly dissipating heat (a cool drink can, for example); in other words, a relatively static load.
Violating conditions (a) or (b) will directly impact the cooler’s COP and mean a larger power consumption for the same amount of cooling. A peltier/thermoelectric cooler that attempts to cool the human body violates both (a) and (b) above, and will need to overcome the following challenges, all at the cost of power dissipation.
- When current is applied, heat moves from one ceramic plate to the other - remember that these are only 0.5cm apart - and unless that heat is quickly moved further way through other means, the cooler will be ineffective. If you are looking for an analogy, a peltier module is akin to your sweat gland - it can bring the heat out to the surface but it needs help when it comes to removing that heat away from the surface. A strong blower that removes the heat is one option, but comes with a power and price penalty.
- The “coolness” available on the hyperlocal ceramic plate will need to be extended across the face if it has to be effective, and this will need a second blower - a power and price penalty.
Any effective cooling solution for the face/head will require over 35-40W of power. Compare this with an air cooling technology where the only power you dissipate is for a single fan, and is usually 1 - 1.5W, almost 20-25X lower. Our very first prototypes were based on the peltier module, and the only way we could get the power we wanted for effective cooling was by having a power cable from the product to the bike - imagine the inconvenience for the user with such an approach!
We realized that the best way forward from a rider-experience stand-point is to have an ultra-portable, power-optimum solution and zeroed in on air cooling as our technology of choice for the BLU series of products.
If there is one thing all of us believe, it is that everything will eventually become smaller, sleeker and perhaps even invisible.
So in light of that grand expectation, when we started our journey into the area of personal cooling, one thing was really clear. We have to make this solution as small as possible. If we are looking to build an accessory for the helmet, we have to consider the size and weight of this product. A good helmet today, will weigh anywhere from 1.2 to 1.5kgs. So we are looking at perhaps an accessory that is around the 250-350gms category.
This is where we had our breakthrough. Our solution finds the optimum balance between the fan’s drive, the battery size and the amount of water the cartridge needs to hold. We didn’t get to this stage without trials and iterations and market trials. We have had two versions of the solution hit the market worldwide and have gone through 3 full cycles of summer to get to this point.
BLU3 E20 - Dramatic improvement in the helmet cooler’s performance
BLU3 E20, the next product in this line, will deliver impressive improvements over its immediate predecessor. BLU3 E20’s air-flow will be 100% more than BluSnap2, and will deliver ~ 6 litres of cool air every second into the helmet. We have added the ability to control the airflow in both speed and direction to help our riders find the most comfortable setting. The entire airflow and internal geometry has been looked at to optimise every millimeter of space and make the product sleeker without compromising on performance. We have gone through multiple prototypes and 3D printed parts, testing and cross referencing the performance until we were fully satisfied with the results. Our ride test teams have put the prototypes through rigorous tests and those inputs and insights have helped make all the difference to the end product.
Excited? Want to get one right away? Hang on a bit as we get BLU3 E20 ready for production. If you are interested in knowing more, you can sign up here. We will keep you posted on our production-readiness and share exciting early-bird offers (opportunity to beta-test the product, steep early-bird discounts, etc.)