Compact and sustainable cold storage with Glycerol

AI Quick Summary

The project aims at building the first latent thermal energy storage unit with glycerol as a phase change material (PCM), to be integrated into AC units for residential cooling. This will offer a sustainable answer to the global rising demand for cooling with an easy-to-implement, inexpensive and reliable solution. This allows to improve the energy efficiency of AC units and decrease the CO2 eq emissions from residential cooling by at least an estimated 30%. The problem​To achieve a net-zero future, rapid decarbonization of energy-intensive sectors like mobility and heating is essential. While heating currently dominates residential energy demand, cooling needs are projected to rise by 45% by 2050 due to increasing temperatures and improved living standards in developing countries, particularly in India and Southeast Asia. This growth in cooling demand will heighten CO2 emissions and strain electricity grids. To date, efforts to decarbonize have focused more on heating, with limited attention to cooling, mainly in developed countries. Compact storage solutions using phase-change materials (PCM) offer a promising way to address cooling demands. Glycerol, a byproduct of biofuel production, shows promising properties for cold storage (melting point at 18°C, high energy storage capacity), while also being widely abundant and inexpensive. Our initial simulations suggest that integrating glycerol-based energy storage systems in AC units could increase the energy efficiency and reduce the CO2 eq emissions by 30%.In this project, we strive to create the first glycerol-based thermal energy storage unit to be integrated into both new and old air conditioning units for a sustainable way to cool homes.The USP​There are quite a few advantages to implementing a cold storage with glycerol to traditional HVAC systems. Firstly, the cold storage would allow to store renewable cold during production time, to then utilise it when the demand is high, renewable energies are not available, or the electric grid is under severe strain. This would translate to both reduced CO2 emissions, as well as reduced energy consumption and related costs. In addition, currently for every 10L of biofuels produced, about 1L of glycerol is obtained, which serves solely as feedstock for production of other value-added chemicals. In order to launch biofuels, more usages for crude glycerol need to be found. Therefore, crude glycerol is extremely low priced, and might even be provided virtually for free/with incentives for services that utilise it.Current challenges and activities​​Although glycerol is an ideal candidate for cooling applications, it is afflicted by high degrees of supercooling (i.e. freezing well below the theoretical freezing point) and by slow crystallisation growth rates (< 0.1 mm/min), which limit the power that can be delivered. To use glycerol as a PCM, both problems must be solved. At HSLU we have performed simulation activities, and built a first prototype of an energy storage module with 50L of glycerol as PCM. However, the issues of supercooling and slow crystal growth rates still need to be understood, so that effective solutions to reliably crystallise glycerol in the 50L to deliver cold with reasonable power can be found. Next steps​We aim to understand the crystallisation behaviour of glycerol both at a laboratory scale with a wide variety of analytical techniques and tests (i.e. differential scanning calorimetry, microscopy, x-ray diffractometry, crystal growth speed tests in glass tubes), and in a full-scale in our 50L setup. Once the crystal growth limiting step has been identified (i.e. heat transfer, viscosity, molecular mobility), suitable techniques to counter this effect (i.e. dilution, laser impulse, electric voltage, multi-seeding, etc.) will be implemented in the 50L and tested in a full-scale. The powers delivered by the energy storage unit will be recorded, and the implication for energy savings and CO2 emission reduction potential of both existing and new AC units will be drawn.

Project Idea Metadata

• Project Idea Name: Compact and sustainable cold storage with Glycerol
• Date: 7/24/2024 2:46:28 PM
• Administrators:
  • Rebecca Ravotti

Project Idea Description

The problem​

To achieve a net-zero future, rapid decarbonization of energy-intensive sectors like mobility and heating is essential. While heating currently dominates residential energy demand, cooling needs are projected to rise by 45% by 2050 due to increasing temperatures and improved living standards in developing countries, particularly in India and Southeast Asia. This growth in cooling demand will heighten CO2 emissions and strain electricity grids. To date, efforts to decarbonize have focused more on heating, with limited attention to cooling, mainly in developed countries. Compact storage solutions using phase-change materials (PCM) offer a promising way to address cooling demands. Glycerol, a byproduct of biofuel production, shows promising properties for cold storage (melting point at 18°C, high energy storage capacity), while also being widely abundant and inexpensive. Our initial simulations suggest that integrating glycerol-based energy storage systems in AC units could increase the energy efficiency and reduce the CO2 eq emissions by 30%.

In this project, we strive to create the first glycerol-based thermal energy storage unit to be integrated into both new and old air conditioning units for a sustainable way to cool homes.

The USP

​There are quite a few advantages to implementing a cold storage with glycerol to traditional HVAC systems. Firstly, the cold storage would allow to store renewable cold during production time, to then utilise it when the demand is high, renewable energies are not available, or the electric grid is under severe strain. This would translate to both reduced CO2 emissions, as well as reduced energy consumption and related costs. In addition, currently for every 10L of biofuels produced, about 1L of glycerol is obtained, which serves solely as feedstock for production of other value-added chemicals. In order to launch biofuels, more usages for crude glycerol need to be found. Therefore, crude glycerol is extremely low priced, and might even be provided virtually for free/with incentives for services that utilise it.

Current challenges and activities​

​Although glycerol is an ideal candidate for cooling applications, it is afflicted by high degrees of supercooling (i.e. freezing well below the theoretical freezing point) and by slow crystallisation growth rates (< 0.1 mm/min), which limit the power that can be delivered. To use glycerol as a PCM, both problems must be solved. At HSLU we have performed simulation activities, and built a first prototype of an energy storage module with 50L of glycerol as PCM. However, the issues of supercooling and slow crystal growth rates still need to be understood, so that effective solutions to reliably crystallise glycerol in the 50L to deliver cold with reasonable power can be found.  

Next steps​

We aim to understand the crystallisation behaviour of glycerol both at a laboratory scale with a wide variety of analytical techniques and tests (i.e. differential scanning calorimetry, microscopy, x-ray diffractometry, crystal growth speed tests in glass tubes), and in a full-scale in our 50L setup. Once the crystal growth limiting step has been identified (i.e. heat transfer, viscosity, molecular mobility), suitable techniques to counter this effect (i.e. dilution, laser impulse, electric voltage, multi-seeding, etc.) will be implemented in the 50L and tested in a full-scale. The powers delivered by the energy storage unit will be recorded, and the implication for energy savings and CO2 emission reduction potential of both existing and new AC units will be drawn.

The project aims at building the first latent thermal energy storage unit with glycerol as a phase change material (PCM), to be integrated into AC units for residential cooling. This will offer a sustainable answer to the global rising demand for cooling with an easy-to-implement, inexpensive and reliable solution. This allows to improve the energy efficiency of AC units and decrease the CO2 eq emissions from residential cooling by at least an estimated 30%.