The finalists for the Global Cooling Prize reveal a diverse range of approaches to reducing carbon output
Barocal is a start-up spun off from the University of Cambridge, Here researchers at the University of Cambridge’s Department of Materials Science and Metallurgy are developing a solid-state cooling technology to solve the cooling challenge.
This solid-state Barocaloric cooling technology takes advantage of the properties of solid organic “plastic crystal” materials to provide cooling. By applying pressure to these organic solid crystals, it is possible to change their molecular orientation which results in a solid state phase transition, thus causing a change in their entropy (degree of disorder) which leads to a temperature change of the system.
The process of continuously “applying and releasing pressure” on the Barocaloric material results in solid-to-solid phase changes in the crystals which results in large thermal changes due to molecular reconfiguration. This produces a cooling effect which can be delivered either to the room air or to produce chilled water for cooling. These plastic crystals are flexible materials that are widely available and are low-cost and non-toxic. Research shows that the thermodynamic behaviour of these plastic crystal materials is very similar to commonly used refrigerants, which has the potential to create a viable and alternative cooling approach to the century-old vapour compression technology.
Daikin India has proposed a cooling system integrating a multi split arrangement, connecting three indoor units with one outdoor unit, with evaporative cooling technology. A controls system will automatically spray water under the conditions with high ambient temperature where cooling load sees particularly high. Significantly Daikin proposes use of the low GWP HFO R1234ze(E) refrigerant, based on the criteria of the Global Cooling Prize, although the company notes that as per its current refrigerant policy, R32 is considered to be the most balanced refrigerant; and Daikin will continue to proactively promote it.
Godrej and ATE Enterprises
Godrej has partnered with evaporative cooling specialist ATE Enterprises to develop an advanced hybrid cooling technology, leveraging its own and well-established environmentally friendly natural refrigerant based technology used in its present domestic air conditioners.
It says this cooling technology integrates Godrej’s own well-established high-efficiency vapour compression system with a natural and low global warming potential refrigerant and advanced evaporative cooling technology to provide cooling.
The advanced evaporative cooling technology reduces the air temperature without adding to its humidity level. This cool air is then either supplied directly to the indoor space or passes through the vapour compression system which optimises compressor performance depending on the set indoor temperature and humidity requirements of the space. The grid electricity consumption of the cooling system is further reduced by improving the heat exchanger efficiency and by using a small integrated solar PV panel to offset part of the total power demand of the solution. The integration of these advanced technologies is achieved through smart controls that optimise the performance of this integrated solution.
Gree, the world’s largest residential air conditioner manufacturer, is collaborating with Tsinghua University, one of the top universities in engineering field in the world, to develop a ’super-efficient and climate-smart residential cooling solution.’
The innovative hybrid solution is designed to have an automatic, climate-smart operation in three unique modes – vapour compression refrigeration; direct evaporative cooling; and ventilation – which will switch between each other or operate the three modes in parallel to each other depending on the outside weather conditions to provide optimsed indoor cooling.
The vapour compression refrigeration mode of the cooling solution adopts an innovative temperature-humidity-independent-control cycle. It uses an ingenious compressor technology with a low GWP refrigerant in conjunction with improved design of evaporator and condenser systems to more effectively cool and dehumidify the air, thus using dramatically less energy than today’s typical products. The solution has a small solar PV panel integrated into the outdoor unit to further lower the overall grid-electricity consumption of the solution.
Kraton Corporation, a global speciality chemical company, is collaborating with Infosys , the Indian Institute of Technology Bombay, and Porus Labs to develop a hybrid cooling solution called NexarCool, using a membrane dehumidification system based on its Nexar polymer.
NexarCool technology integrates an electro-osmotic membrane dehumidifier with a water-based direct evaporative cooling system to achieve air conditioning without using any refrigerant.
By applying a small voltage across the membrane dehumidifier system, water vapour from the indoor air is ejected to the outside air, thus making the indoor air dry in the process. The dry indoor air is then cooled via a direct evaporative cooling process, where the moving air loses its heat to evaporate the water, and in the process, gets cooled. This integrated approach to cooling is expected to have significantly lower energy consumption than conventional air conditioners sold today. Additionally, as no refrigerant is used, the technology has the potential to dramatically lower climate impact, the firms say.
M2 Thermal Solutions
M2 Thermal Solutions, a startup company based in the United States, is developing a cooling solution that uses a combination of evaporative cooler and membrane technologies to independently cool and remove moisture from room air, and this technology requires no compressor or refrigerant.
This cooling solution integrates an evaporative cooling technology with a membrane system in a packaged design that is able to independently cool and dehumidify room air, which enables dramatically less energy to be consumed. In this system, an evaporative cooler first operates to cool the room air while increasing its humidity. The cool and humid air is then passed through a membrane system to remove the excess water vapourfrom the cool air, thus decreasing its humidity. The solution also has the capability to bypass either of these processes, and just use a ventilation mode depending on the outdoor weather conditions. Furthermore, the vast majority of the water supplied to the evaporative cooler is generated by the membrane system – thus minimising the water footprint of the solution. With no compressor or refrigerant, and an innovative approach to independent cooling and dehumidification, this solution has the potential to achieve significantly lower climate impact than typical AC units sold today.
S&S Design Solution
S&S is a group of mechanical engineering researchers and innovators with expertise in air conditioning design and development are developing an efficient hybrid residential cooling solution maximising the heat utilisation combined with primary evaporative cooling, secondary liquid cooling and tertiary refrigerant cooling, using low GWP refrigerant.
This combines a two-stage cooling system with direct evaporative cooling of the condenser to achieve a significantly higher efficiency as compared to the typical AC units sold today, they say. The two-stage cooling system integrates a water loop and a traditional vapour compression system to optimise the performance. The water loop pre-cools the room air which is subsequently cooled and dehumidified to the desired conditions at the evaporator of the vapourcompression system. At the condenser section, a part of this conditioned air is further cooled using direct evaporative cooling, thus significantly improving the condensing efficiency. The performance is further optimized by using a variable speed compressor and with the application of a natural, low GWP refrigerant, the proposed solution has the potential to achieve dramatically lower climate impact. The use of DC electrical componentry in the design allows for easy integration with renewable power sources, and together with the solution’s low-cost potential, provides an opportunity for increased access to cooling.
Transaera is a manufacturing start-up from the Massachusetts Institute of Technology, which is developing a hybrid cooling solution with desiccant dehumidification technology based on novel materials discovered at MIT.
The cooling solution is designed to operate a high efficiency room air conditioner in parallel with a moisture storage battery (MSB) to provide cooling and dehumidification, while using dramatically less energy than typical room air conditioners sold today.
By separating the temperature and humidity control processes, this air conditioner has the potential to reduce the energy consumption significantly while providing the desired comfort level. Humid air is difficult to cool because of the large amount of water vapour in the air. Transaera’s Moisture Storage Battery (MSB), comprising a novel desiccant material, has the capacity to adsorb a large amount of moisture allowing room air to dehumidify, the firm says.
Dry air is easier to cool with the high-efficiency AC unit, thus reducing the overall electricity consumption. Additionally, while typical desiccant materials require a high-temperature source for regeneration, the MSB material can regenerate using waste heat from the vapour compression system as and when it gets saturated, thus reducing the energy consumption of the overall solution. The system also has a provision for direct evaporative cooling of air at the condenser inlet to improve condensing efficiency, a small integrated solar PV panel and battery to reduce grid-consumption and collects rainwater for use to improve the overall environmental impact of the solution.