Muzzle Outfit

Inspiration:Frostbite Injuries

Frostbite is defined as injury to body tissues caused by exposure to extreme cold, typically affecting the extremities and often involving only the skin, which initially becomes white and hard, but in severe cases resulting in gangrene of deeper tissues and loss of the affected parts.

According to some papers, frostbite injuries affect 36% of high-altitude mountaineers.

Frostbite is more prevalent among homeless people, along with an increasing participation in outdoor activities such as mountain hiking and skiing.

The idea: A ‘Muzzle’ to avoid frostbites

The idea is to develop a winter outfit for extreme weather conditions able to avoid or diminish the risk of frostbite with a heating system added in gloves and shoe palms.

The heating system will be similar to an electrical blanket: a 5 V electric heating pad fed by solar PV cells attached to the jacket and trousers.

Functionality

The main piece will be a third layer jacket waterproof and wind-stopper with pv cells attached in the external part of the sleeves.

These cells will be flexible Si-amorphous or OpV technology (ASCA PV modules) in order to allow the whole range of movements required in alpine sports. The cells will be settled into transparent plastic pockets with the aim of being easily removable for cleaning or maintenance.

The PV cells will charge two 2000 mAh Li-ion batteries (cell phone standard) attached at the back of the jacket in a protected area.

The back of the jacket area will not include active pv cells considering the need of carrying a backpack or similar.

The batteries will be enough for feeding the electrical hand heaters for an estimated period of 93 minutes or the feet electrical resistor for 85 minutes. The four electrical heaters working simultaneously could have an autonomy of 44 minutes, which might be providential for saving a mountaineer for severe frostbite injuries.

The user will be able to select which part of the body wants to prioritize through a source selector button attached in the neck of the jacket. With this device the person could also select LED lamps for lighting dark environment. These lamps will be hidden in a mini-velcro pockets at the end of the sleeves of the jacket.

Additionally, a security red-light with a small magnifying glass attached (for reducing energy demand) in the pit of the jacket system could be activate in order to facilitate the localization of the mountaineer in case of getting lost or accident.

The technology

A set of eight 100 x 150 mm PV organic solar films (ASCA) distributed over the sleeves and trousers are suggested for feeding the electrical devices included in the Muzzle Outfit.

The operating available power was considered as 2-3 mW/cm2, that means a power between 2, 5 o 3, 9 W for charging batteries with 1.300 cm2 of active (solar film) area.

It is important to highlight that the snow albedo factor (proportion of the incident light or radiation reflected) of around 80% could increase the estimated electrical generation. Paradoxically, the factor that might cause sunburns in mountaineers could also boost solar power generation.

For an extra power generation, two ideas were added in the project:

1. All solar films will be surrounded by a reflective aluminized frame. These solar frames could be ‘open’ and act as a small solar concentrator in case of clear sky.

2. Two extra solar films folded in shoulder pockets that could deploy in case of need and proper weather conditions (not very windy, for instance). These solar shoulder pads could act as an extra solar collector and could be also bifacial for capturing solar radiation reflected by the snowy terrain.

This possible extra power was not considered in calculations but could increase the electrical power available up to 5 W or even more.

The charging process

As the power available expected from the solar cells doesn’t fit the heating requirements, two Li-ion batteries were added in the system. The batteries specifications are similar to many typical smart phones: 2000 mAh capacity and 3, 7 V. This means an energy capacity of about 8 Wh.

The cells will be connected in parallel (in case of damage of one, all others can still work) and the positive and negative cables will run insider semi-rigid mini-duct inside the insulation layer of the jacket to the batteries on the back. As the current expected will be less than 1 A, 1, 5 mm2 section for each cable or less will be enough. Flat cables would be the best solution for better comfort.

For a complete charge of the batteries by the solar cells, and considering 95% of efficiency in charging/discharging processes, it was estimated a charging time between 5 and 7 hours (with 2, 6 W of DC solar power from the photovoltaic system). This might seem a lot but it is a reasonable time for sports that normally spend the whole day outdoors.

The Discharging process: the heat requeried

From different bibliography (as NTP 1037, Spanish Prevetion Technical Norm) was estimated a heat loss in hands and feet of about 136 W/m2 and 119 W/m2 respectively. This means that a heating power of about 5 W per member should be enough for keepin skin temperature in values that avoid cellular injuries cause by cold.

Depending on the cloths insulation, external wheatear conditions and the exposed time to cold, the power needed for keeping the member warm could be less, so a potentiometer for heating power control was included in the outfit.

This power supply is easily achievable through current DC electrical heaters available in the market (see figure below). The supplier in the figure below suggests a 0, 4 W/cm2 of heat supply which means a 48 W (we don’t need so much!) for a 10 x 12 cm surface (equivalent area for one hand of foot electrical blanket). Anyway, there are also DC warm wires available that can provide 4 W for 0, 5 meters length. This power should also be enough for heating purposes.

(Imagem heating pads and wire)

It is important to note that the solution suggested intends to be an emergency system. Due so, there will be a button for activate or deactivate the heating devices and keep the batteries unloaded.

In case of need, was calculated an autonomy from the batteries of 44 minutes for keeping the 5 W heating supply in the four members. In case of only heating hands or feet, this time would increase up to one hour and a half.

The materials

For the winter clothes no innovation related to materials or fabric was included. The high-altitude clothes already carry a big technology development and it would be reckless to intend to bring any changes onto it.

It was considered a three layer jacket and two layer trousers with proper insulating materials (inner layers) and wind protection (outer layers).

For the gloves inner liner it was consider a rock wool material or polar fleece liner able to keep the heat produced by the electrical blanket. For the outer shell, windproof and waterproof, breathable fabric with a final skin leather. Anyway, additional pair of mittens might be needed for extreme cold conditions.

As the high-altitude boots are also very specific products, the suggestion is to include a shoe electrical heater palm in each of them made of fleece and properly insulated for avoiding risck of electrocution.

The gadgets

Hand LED lamps

It was considered two head lamps hidden in hook & loop fasteners pocket in both jacket sleeves. These lights can be activated through a button attached in the pit of the jacket.

Electrical mini-blanket for gloves

The heater pad/mini-blanket will be fed by the batteries. The cables will also run inside semi-rigid ducts hidden inside the clothes from the back of the jacket to the gloves. The gloves will join to the jacket by a fabric connection that will shelter the passing cables from the batteries to the heater, as shown in the figure below. There will be a zipper running the wrist in order to take of the hand from the gloves in case of need.

Shoe palm electrical heater

A mini-electrical blanket shoe palm shaped will be added to the mountain boots. The shoe palm will have a flat cable at its back, running through the heel, that will carry the electrical current from the batteries.

The cables feeding it will run first from the jacket to the mountain trouser through a quick two-poles connector insulated an easy to plug or unplug by a simple pressure click.

The cables will come down in semi-rigid ducts inside the trousers to the end of them, where will be placed another connector able to plug with the flat cable of the electrical palm shoe.

Extra: Rescue signaling

The remaining energy stored in the batteries could be derived to a blinking red-light LED alarm added on the pit of the jacket. This light would be embedded in a special augmentative plastic cover that allows to see the light in the distance in case of the user's need.

About electronics

In the figure below it can be observed a block diagram of the basic idealization of the system.

A TP4056 will be responsible for battery charging. The circuit will also have a microcontroller ATMEGA328P responsible for managing the power of heating resistors by Pulse Width Modulation (PWM), reading 5 switches for activating LED’s lights and reading the analogic signal of temperature sensors embedded in the electrical heaters.

The circuit was developed in Proteus 8.13 software which also permitted simulate the basic functionality of the system.

For voltage regulation would be used a low consumption device. For simulation purposes only, was used a LM7805. For the first prototype was used a ATMEGA328P microcontroller from AVR, the same used in Arduino platform. Microcontrollers with Bluetooth or Wi-fi incorporated could be used in following versions.

The power regulation of electrical heaters will be possible thanks to PWM control, adapting the voltage in the resistors by switching mosfets and, consequently, the passing current on them.

Finally, some suggestions of cable routing in the complete outfit (it is important to highlight that the cables would be hidden inside the clothes):