In hot countries such as South Sudan, laptop cooling systems are ineffective and laptops run inefficiently. hipsterIce is an inexpensive, non-powered cooler that gives laptops five hours of efficient use every day, increasing performance and lifespan.
The problem was the focus of the IET Global Challenge 2015, the brief being provided by RedR UK, a humanitarian training organisation. For those working in aid organisations where resources are limited, it is critical that their supplied equipment is functional and durable. However, laptops are not designed for high ambient temperatures, and the resulting performance loss has a huge impact on the productivity and morale of their users. Available cooling technology is either ineffective or inappropriate for the context of aid operations, and we realised that a successful design had to be simple, robust and entirely non-powered.
hipsterIce uses thermal conduction through the base of the laptop to cool it down. The heat from the laptop is conducted through thermal pads and aluminium plates into a large quantity of a mixture containing Glauber’s salt (sodium sulphate decahydrate). The heat is distributed throughout the mixture using an embedded aluminium honeycomb.
As the salt melts, it remains at a constant temperature of 32 ˚C, thus maintaining a large temperature gradient between the base of the laptop and the aluminium for a high rate of conduction. This cools the laptop, enabling it to remain functional even in elevated ambient temperatures.
Once the mixture has melted, hipsterIce can be left in temperatures below 30 ˚C overnight; this refreezes the mixture, allowing it to be reused the next day. In order to reduce the refreezing time, the salt container can be removed from the insulating box, which gives a larger surface area for heat loss.
The initial concept was developed over multiple brainstorming sessions. Various concepts were evaluated for removing heat from the laptop, and this concept was chosen as it was non-powered, which we felt would be useful given the limited energy supplies available to aid workers.
The concept was then modelled in CAD following sketches, and rough thermodynamic calculations were performed to estimate the effectiveness of the cooler; these were used to refine the design to give the desired characteristics in terms of thermal energy absorbed and rate of heat transfer from the environment.
The initial prototype was constructed as a proof of concept; functionally sound, but with questionable aesthetics. It was tested using a thermal chamber and a laptop. The laptop was put under heavy load, and its internal temperature was monitored. The laptop was subjected to various ambient temperatures in the thermal chamber; in all tests, hipsterIce dramatically improved the performance of the laptop over a period of eight hours when compared with the control.
The main drawback in the first prototype was the long period of time taken to refreeze the salt. Thus the second set of prototypes allow the salt-containing box to be removed from the insulation, which allows for much faster recooling.
The novelty of hipsterIce comes from the combination of three key aspects: Glauber's salt providing passive cold storage, an aluminium network thermally connecting the salt to the laptop surface, and the laptop-to-cooler interface - aluminium discs, each with a thermal pad, creating a deformable and configurable surface for maximum contact area with the base of a laptop. Other devices that use Glauber’s salt as the active component exist, but none of them incorporate the other aspects of our design; these features make hipsterIce the only effective way to cool laptops in ultra-hot, power-limited environments.
The other commercially available products commonly use a fabric pouch filled with the salt, and are marketed more as devices to protect the user from discomfort. The key drawbacks of these are a lack of a thermally conductive path into the salt, and a low capacity for heat storage - problems which hipsterIce overcomes, despite a low unit cost of £15-20.
The second set of prototypes will be field-tested by aid workers in the near future; the feedback from this will allow the design to be refined, especially in terms of usability and ergonomics. Further prototyping and testing will lead to a final design; once this has been achieved, the product will be marketed, and we will seek investment to bring hipsterIce into production. Our initial target market is aid organisations, but there are other markets into which we are looking to expand. We have already formed a business, Pembroke Innovations Ltd, which will initially be focused on hipsterIce.
Winner - IET Global Challenge 2015
National Runner Up - James Dyson Award 2016