After our kickoff meeting with Facture, it was time to tackle the fundamental question at the heart of VASSR: what's the most efficient way to melt snow using battery power? The physics behind this question are fascinating but also present a substantial challenge to the weight tradeoff for the product. To transform snow into drinkable water, we need to overcome two thermal hurdles: first, warming the snow to its melting point (if it's below 32°F/0°C), and then providing the energy needed for the phase change from solid to liquid.
This phase change, known as the latent heat of fusion, requires 334 joules of energy per gram of ice, regardless of the starting temperature. To put this in perspective, heating liquid water by one degree Celsius only takes 4.186 joules per gram. The energy needed to melt ice is equivalent to what it would take to heat the same amount of liquid water by about 80°C! This high energy requirement explains why you can't simply stuff snow into your water bottle and wait for it to melt – there isn't enough ambient heat energy available to drive the phase change efficiently.
We set up a controlled testing environment to compare different heating methods. The goal was to find an approach that could efficiently convert electrical energy into the heat needed for this transformation. Our benchmark would be an isobutane camping stove – the current gold standard for backcountry water production.
The testing setup was methodical. We conducted all experiments in a 70°F room using identical vessels. Each test began with approximately 400g of shaved ice and 100g of water, mimicking the real-world scenario of starting with some liquid to help initiate the melting process. For our electrically powered tests, we maintained consistent power input using a DC power supply targeted at 120 watts (12V at 10 amps).
The results were illuminating. The isobutane stove set an impressive benchmark, melting our test sample in just 5 minutes and 22 seconds with 97% efficiency, using only 3g of fuel. By comparison, our electrical methods showed varying levels of promise:
The resistive coil emerged as our top electrical performer, melting the ice in 16 minutes and 52 seconds with 87% efficiency, consuming 31 watt-hours of energy. Its direct contact with the ice/water mixture proved crucial for efficient heat transfer. Extrapolating the overall power usage, with approximately 30Wh used to melt 400mL of ice, means that about 75Wh will be required for 1L of water.
The resistive sheet followed closely in terms of time, taking 16 minutes and 48 seconds, but showed lower efficiency at 70%, using 33 watt-hours. The heat loss to surrounding materials was evident in these numbers.
The ceramic radiant heater lagged significantly, requiring nearly an hour (59 minutes and 29 seconds) and showing only 13% efficiency while consuming 38 watt-hours. This poor performance quickly eliminated it from consideration.
Yes, isobutane's performance is impressive – so why pursue battery power? The answer lies in both practical advantages and our vision for the future of outdoor recreation. While traditional fuel stoves offer excellent efficiency, they come with significant limitations. Setting up a stove requires stopping, finding a stable surface, and managing an open flame with most stoves – often challenging in winter conditions with wind and snow. On day trips, it’s often not in the cards, due to time constraints, weather conditions or even team dynamics, to stop for an extended period of time to wait for a stove. VASSR's battery-powered approach allows for continuous melting while you move, whether the bottle is in your pack or an outside pocket. There's no stoppage time and no need to manage exposure to the elements.
More fundamentally, we believe the outdoor industry needs to evolve toward sustainable energy solutions. While battery power may not yet match the energy density of liquid fuel, the technology continues to advance rapidly. By developing VASSR now, we're positioning ourselves at the forefront of this transition. Just as electric vehicles once lagged behind gasoline engines in range and performance but now compete head-to-head, we envision a future where battery-powered outdoor gear offers superior performance while reducing our environmental impact.
With our heating method selected, the industrial design team began exploring different form factors for the lid. They developed several intriguing concepts:
The "Cap Scoop" design featured a dual-purpose cap that could be used to gather snow, with a simple twist-to-lock mechanism. This approach emphasized simplicity and ease of use, though it limited the amount of snow you could gather at once.
The "Cup Scoop" concept introduced a larger secondary vessel for snow collection that could double as a drinking cup. This offered more versatility but added complexity to the overall design.
The "Shovel Scoop" pushed the concept further, with an ergonomic handle and shovel-like profile for easier snow collection. While this might be the most efficient for gathering snow, it represented the biggest departure from traditional bottle designs.
The “French Press,” as we called it, tried to incorporate a moveable filter into the vessel. It would have been used to filter small particulates and to compress the snow toward the heating element on the bottom. We evaluated various spring-loaded mechanisms and protrusions from the bottle. However, all options were too complex, particularly for how to maintain a water-tight seal for while the bottle is jostled around in a backpack.
Each concept incorporated practical features like over-molded rubber grips for better handling with gloves, and careful consideration of the battery and electronics placement in the base. Ultimately, we were very intrigued by the shovel-scoop concept and decided to integrate it into the initial prototype. We could always fall back on a normal lid if it proved too burdensome or if people didn’t care about it.
This is where I'd love to hear from you, the winter adventurers who might one day use VASSR. Which design approach appeals to you most? How do you envision using VASSR in your winter activities? Would you prefer the simplicity of the Cap Scoop, the versatility of the Cup Scoop, or the utility of the Shovel Scoop? Share your thoughts at vassrbottle@gmail.com or reach out on social media @vassr – your input could help shape the future of winter hydration.
Next time, I'll share how we took these insights and began to develop our first working prototype. Stay tuned, and don't forget to drink your snow!
