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Lightweight, long endurance body cooling for fire fighters

Final Report Summary - STAYCOOL (Lightweight, long endurance body cooling for fire fighters)

Executive summary

Currently, time spent attending to a fire is limited by thermal stress (surpassing the 39 °C body-temperature limit) experienced by the firefighter, and not by the amount of breathing air that is available. Control of wild fires can require firefighters to operate in areas of high radiant heat (from burning vegetation) for prolonged periods of time, and an effective means of personal cooling will improve their effectiveness, and may save lives as heat exhaustion will be delayed and may even be eliminated.

The STAYCOOL personal cooling system is a lightweight mobile active-cooling device adequate for preventing thermal stress on human users, keeping constant heat-extraction temperature within a comfortable range and avoiding the effect of cool spots.

The STAYCOOL system regulates body temperature through a set of patches attached to a garment in contact with skin (likely through a thermal barrier such as some type of clothing). These patches are attached to a secondary heat exchanger cooled by water that removes the heat extracted from the body. The coolant circuit transfers this heat to the primary heat exchanger, where it is finally sent to the environment by evaporative effect.

Features of the developed STAYCOOL personal cooling system include:

1. a lightweight and reusable cooling garment with high heat extraction;
2. lightweight, compact (< 5 litres) evaporative heat exchanger unit with potential to expel 260 W in laboratory conditions;
3. programmable control system for the management of the different elements of STAYCOOL, to maximise endurance and minimise system weight;
4. endurance of the system (> 1 hour) solely limited by size of water tank (1 litre);
5. system is driven by body heat, so power source is only required for low-voltage pump, fan and control system;
6. quick-disconnect pipe connections;
7. total weight of the system < 5kg;
8. applicability of low-cost, high-volume manufacturing processes;
9. applicability to other occupations requiring personal cooling;
10. low unit cost price.

In summary, STAYCOOL personal cooling system has the potential to significantly increase the time attending to the fire by the firefighter and so reduce the time to put out the fire or to attempt a rescue, and consequently reduce damage to property and potential loss of life to the public or the firefighter. It is specially designed for extreme high-temperature environments where heavy, highly insulating Personal Protective Equipment (PPE) and clothing are required.

Although the initial application of the STAYCOOL product is the firefighting market, which imposes very specific use requirements, it is foreseen that after further development iterations the product will be adapted to other applications requiring low weight, mobile and smart thermal-stress control.

Project context and objectives

There are about 500 000 professional fire fighters in the European Union (EU). When called to fight fires they can be exposed to high levels of heat stress, which results in decreased physical performance and even heat exhaustion. If a firefighter succumbs to heat exhaustion he requires rescuing and this then exposes other firefighters and the public to increased risk. In order to reduce the risk of heat stress, the firefighters are limited with regard to the time they can attend to the fire, which increases the number of firefighters needed to fight a fire, and this reduces efficiency and introduces complication into the communications between the crews fighting the fire.

The STAYCOOL project has developed and prototyped a novel system for cooling the body that is lightweight, has low energy consumption and so can be worn for prolonged periods of time. Wearing the STAYCOOL system will reduce the wearer's core temperature and allow firefighters to stay at the fire for greater periods of time, and so improve the efficiency of fighting the fire, extinguishing the fire quicker and reducing risk of loss of life and damage to property.

The STAYCOOL concept is a new innovative personal cooling system, which is lighter in weight and has greater endurance than existing commercially available systems, while offering significant cooling power and keeping a low price. It consists of a garment incorporating 'cooling pads' that are connected to a compact low-energy heat exchanger that mimics sweating. The principle of the system is that it will by-pass the barrier to sweat evaporation created by the personal protective clothing and allow 'sweating' from a biomimetic surface outside of the clothing. This is to provide heat loss comparable to that from a bare torso but in a package that does not interfere with the activities the user has to execute.

The STAYCOOL partnership is ideally placed to develop and exploit this technology, having expertise in protective clothing design and manufacture, physiological and human factors testing, mathematical and thermodynamic modelling, access to rapid prototyping and manufacture facilities, and the ability to design for manufacture to ensure the STAYCOOL system can be fully exploited.

The STAYCOOL system is primarily aimed at a launch market for firefighters but there are a number of applications where humans need to work in high ambient temperatures. Additional markets for this technology and associated products include industrial plant operators, miners, underground maintenance, nuclear decommissioning, general policing in hot climates, policing in protective equipment and for use in extreme sports.

The STAYCOOL product will provide the following benefits for the target user.

1. Better working conditions due to the low mass of the new system. The weight of the heat-pipe garment is much less than a liquid circulating vest as only a few millilitres of water are required inside the heat pipe to transfer heat to the outside of the clothing.

2. More efficient than other vests due to enhanced cooling capacity. Good body contact providing high heat-extraction capacity compared to liquid-circulating vests.

3. Useful endurance. As the energy for evaporation comes from the heat of the body and a low mass of water has to be pumped to transfer this heat, power requirements will be modest.

4. Comfort. The water within the heat pipe is kept at a low pressure so it does not need to boil to start the heat-pipe cycle, until skin temperature has risen to a level where cooling is required and the pad will be close to skin temperature (i.e. there will be no uncomfortable cold spots).

The STAYCOOL project aims include several scientific and technological objectives.

Scientific objectives

1. To investigate into wicking and evaporation effects from complex surfaces due to their importance in all the phenomena involved.

Technological objectives

1. To develop and manufacture flexible heat pipes

2. To develop a novel, light heat exchanger, garment and laboratory prototype featuring the following characteristics: cooling power > 250 W; mass of heat exchanger and garment < 4.5 kg; heat-exchanger volume < 1 litre, excluding water reservoir; endurance > 1 hour, evaporation of water.

3. To maximise cooling power of the heat exchanger within volume constraints by increasing surface to volume ratio. Different wicks bonded to cooling fins will be compared in order to select the optimal method of satisfying ratio of area to volume.

4. To develop a control algorithm and sensors to maximise endurance to > 1 hour and minimise system weight.

5. To gather performance and ergonomic data on the laboratory-prototype garments evidenced in a controlled laboratory trial.

6. To deliver laboratory prototypes, capable of being manufactured within final use constraints: cooling power 250 W; achievable fire fighting certification.

7. To demonstrate system effectiveness during field trials with real fire.

Project results

The actual developments obtained for each result after the execution of the STAYCOOL project have been the following.

1. A model of evaporative and wicking behaviour that provides reasonable predictions of surface temperatures and evaporative heat loss, used as a design tool to examine the main parameters for controlling evaporation in the design of heat-pipe patches and the primary heat exchanger.

2. Construction and testing of the laboratory evaporative heat exchanger, proving the concept of the evaporative effect for the project purposes and used as the base for volunteer trials.

3. A control unit has been designed and built to manage the performance of the heat exchanger, including fan, pump temperature sensors and display screen, as used for volunteer trials.

4. A pre-production prototype of the STAYCOOL system has been produced, integrating components of improved designs after feedback from volunteer trials (heat-pipe path, heat exchanger and control unit). The following list provides the main features and specifications, which are pretty close to targets:
(a) lightweight and reusable cooling garment with high heat extraction;
(b) lightweight, compact (< 5 litres) evaporative heat-exchanger unit with potential to expel 260 W in laboratory conditions;
(c) programmable control system for the management of the different elements of STAYCOOL, to maximise endurance and minimise system weight;
(d) endurance of the system (> 1 hour) solely limited by size of water tank (1 litre);
(e) system is driven by body heat, so power source is only required for low-voltage pump, fan and control system;
(f) quick disconnect pipe connections;
(g) total weight of the system < 5kg;
(h) applicability of low cost, high volume manufacturing processes;
(i) applicability to other occupations requiring personal cooling;
(j) low unit cost price.

5. The STAYCOOL integrated cooling system (cooling vest and primary heat exchanger) has been tested with fire brigades under training fires. Firemen who participated in the cooling-garment trial provided useful and positive comments on the STAYCOOL cooling garment:
(a) the HPG was effective in reducing local skin temperature, improving whole-body thermal comfort, and reducing whole-body and torso heat sensation, although some individuals may perceive the HPG cooling to be ‘too intense’;
(b) the cooling garment could be used as part of a routine to cool the firemen exiting a fire fighting operation, to reduce the risk of heat stress as well as to reduce the recovery time prior to the resumption of operational duties;
(c) the man-portable cooling garment system could be used for forest fires and road accidents.%%Potential impact%%Impact on EU society

There are a number of benefits to the EU that will be provided by the STAYCOOL project and these include:

1. Displacement of non-EU products. One of the additional benefits to the EU is that the sales in Europe and also the rest of the world will be at the expense of other suppliers of competing systems, which currently are from outside Europe (mainly USA but also Australia). This project will increase the competitiveness of the EU in this new and growing market.

2. Reduced cost of fire damage. If the firefighters can spend more time fighting the fire (because of the reduction in physiological stress) then fires can be put out quicker and so less damage would be sustained. This would be particularly true for fighting forest fires in southern Europe.

3. Reduced time off work due to heat stress. The STAYCOOL system will reduce the number of occurrences of heat illness and so reduce the time lost by keeping the body core temperature below a tolerable level and below a limit where damage occurs. This also helps the fire services to maintain their high standards of employee care and help meet health and safety standards for working in hot environments.
4. More efficient use of fire resources. By potentially increasing the time that a firefighter can be at the fire scene by using the STAYCOOL system, the rostering of the firefighters can be made more efficient. This will allow more time to fight more fires or provide additional time within the firefighters schedule to maintain currency on other equipment or undertake more training.

Impact on participants

The most evident benefit for participants resides in accessing a niche market with an innovative product and a production cost of < 250 EUR/unit, within firefighter-market budgetary expectations.

A first estimation of the global firefighting market is described here. Fire services around Europe are made up of a mixture of professional, part-time and volunteer firefighters. Different studies show that the relative proportions of these different classes of firefighter by country across the world are nearly constant. Extrapolating these figures, there is a population of approximately 500 000 professional firefighters across Europe (there are more than 100 000 in Germany, France and Poland alone) and, potentially, significantly more than 2 650 000 worldwide. Extrapolating the figures from the CTIF statistics to take into account significant countries not included in the figures such as Spain, the UK, India, China and Italy, it can be estimated that a worldwide figure of 4 000 000 firefighters can be used for impact modelling purposes.

In general, the fire service market is a fairly static market that tends to renew equipment in a cyclical manner as and when either new products become available that provide a performance or cost improvement, or the useful life of a piece of equipment comes to an end. The firefighting market is seen as fairly traditional in terms of the equipment and procurement processes it uses, as they tend to be state-funded and therefore have to comply with government procurement processes. The market is also fairly fragmented, as in many countries it is left to the individual fire brigades to procure equipment, and purchasing at a national level is seldom seen. This increases the complexity of the sales task but does give the opportunity for new, niche products to penetrate a number of the smaller, more forward-thinking brigades first. Even though the fire services are seen as traditional they are also typically open to evaluate new equipment and tend to be early adopters of new technology. Examples of this are thermal-imaging cameras, network communication systems and personal identification systems.

In future (beyond the frame of the STAYCOOL project), the resulting product could be adapted for other specialised applications, thus increasing the number of potential users. These applications consist of the following.
1. Industrial
There are a number of industrial processes that require human intervention in extremely hot environments or wearing high levels of PPE (e.g. glass manufacture, steel processing, chemical plants, nuclear decommissioning). There are also industries that require working in hot environments as part of the day-to-day tasks and where PPE is required. Examples of these are mining and underground tunnel maintenance. The STAYCOOL system could extend the time that workers are exposed to these environments without causing physiological damage and so increase productivity or reduce the time to carry out tasks.

2. Policing
There are two areas of police work where STAYCOOL would improve effectiveness. The first is in public order operations. Anytime large numbers of people are brought together (e.g. sporting events, demonstrations), there is a risk of anti-social and even violent behaviour. Police personnel are equipped with PPE to protect them from violence aimed at them. However, this PPE is highly insulating and relatively impermeable to sweat loss resulting in a risk of a heat-related illness. Also, terrorist threats in the current world political climate create the requirement for police to operate in a contaminated environment wearing high levels of PPE. The heat stress in these situations is exacerbated for example in southern European countries in the summer. STAYCOOL would provide cooling to the police officer and allow a longer time on duty, thereby assisting in continuity of operation and contact with the public and increasing the success of the mission.

3. Extreme sports
Body cooling prior and potentially during some sporting events can increase performance. Sports that would benefit could include motor sports, marathon running and long-distance cycling. The STAYCOOL system would provide a method of either cooling the body whilst carrying out the activity or ensuring the body does not overheat during the warm-up for an event, and so increase performance and competitiveness.

Dissemination activities

Several partners have attended different dissemination events where the prepared communication materials such as project brochures and presentations have been distributed.

Relevant events where STAYCOOL has been present

1. Conference: 'Numerical Simulation of Heat Pipes in the STAYCOOL Project' presented at Workshop on Industrial Problems (26 October, 2012) the University of Santiago de Compostella on the 26 October 2012.
2. Conference: Textile International Forum and Exhibition 2012 & 3rd Asian Protective Clothing Conference. Location: NTUH International Convention Centre, Taipei. 26-27 September 2012.
3. Conference: EURATEX 7th Annual Public Conference: 29-30 March 2012, Brussels. The Conference specifically supported dissemination of the following EU-funded projects.
4. Trade fair: A+A Safety, 'Security and Health at Work’, International Trade Fair with Congress, Düsseldorf, Germany, October 2011
5. Trade fair: TECHTextil exhibition in Frankfurt, International Trade Fair for Technical Textiles and Nonwoven, June 2011.

A project brochure about project aims, needs to fulfil, strategy, and expected benefits to users was distributed among the partners in order to be used in every conference or trade fair they attended.

The coordinator Steve Kay (NWT) was asked to produce a piece on STAYCOOL for publication in ‘Polymeric Protective Technical Textiles' 2011, conference proceedings.

Intense activity has been carried out by the RDT performers to show technology developments to SMEs. Much of this activity has been conducted in devoted meetings, some of it carried out after or before the consortium meetings (to save project resources), but some also took place by teleconference or special visits.

Exploitation of results
The STAYCOOL project foreground exploitation strategy is constructed under the following pillars:
1. to identify key user groups who have influence in their own regions;
2. to work with key user groups to test and trial the product to ensure the end product is what the market needs;
3. to develop product champions throughout key European markets.
The consortium has performed a market search identifying market needs, target customers, market segment, competitors, and SWOT. A strategic approach for investments, commercial activity and an implementation schedule has been developed. The business plan has estimated pricing for the final equipment and a sales forecast. Different options for public and private funding mechanisms for future investments have been evaluated.
The STAYCOOL results are outstanding, but despite significant advances the consortium recognises that further development is required to fully commercialise this product. It is the intention of the SME’s to retain the foreground intellectual property (IP) as 'trade secret' know-how. The advances that have resulted include the following.

1. Significant enhancements in effectiveness/efficiency of heat-pipe patches. The project has succeeded in increasing performance from 25 to 65 W per patch, where the original 25 W patches are protected by QinetiQ’s background IP, United Kingdom Patent Application number: GB1006620.7 entitled Flexible Heat Pipe Structure for Body Cooling, dated 21 April 2010.
2. A prototype primary heat exchanger with a unique multi-plate construction and integrated coolant-pipe configuration.
3. The background IP protection held by QinetiQ provides enforceable protection, which protects these developments through the development stages. The consortium needs to have a financial figure from QinetiQ to use it, but it is very difficult to quote nowadays given that the factors that would influence a financial figure ,including exclusivity, volume and selling price, are still undefined.

The SME partners have worked well together through the project. To make the advances necessary we propose to apply for a demonstration activity.

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