Thermal Energy Storage Solution Optimises Cooling With Phase-Change Materials

Data centres and telecommunications sites require reliable and cost-effective cooling solutions as they need to be cooled 24/7 and to operate optimally at 24-28°C. Typically, these sites are cooled using centralised chiller plant systems. With growing concerns on increasing energy costs by facility owners, there is a need to seek alternative means of cooling.  

The technology providere described herein has developed a cooling technology using phase-change materials (PCM) to store thermal energy by melting and solidification in a concentrated way. Its ability to optimally manage thermal energy offers the potential for a wide range of applications, such as cooling data centres, telecommunication sitesas well as office buildings and districts. The technology has been proven with a working pilot to provide cooling at a telecommunications site in Hungary, which achieved 54% energy savings with 4 years return on investment. The technology provider is keen to seek potential partners for test-bedding and commercialisation purpose. 

This technology uses thermal energy storage, where excess thermal energy from the night is stored to be used in the day or vice versa. PCM is used as the storage media to capture latent heat for thermal energy storage. Instead of changing the temperature to store heat, the phase of the material is changed through the processes of melting and solidification. This approach allows for more concentrated storage of thermal energy because its latent heat is much higher than the specific heat. In contrast,  the typical approach of using water for thermal energy storage would store energy by changing the temperature of the water and using its specific heat. This is an inefficient process due to the low specific heat of water, which is 4.2 kJ/kg K.

The technology comprises:

• Tank with patented design and structure that contains PCM
• Controller unit made up of hardware and the software, which serves to optimise energy management

The tank contains buffer storage arrangement filled with PCM that is adapted for storing and releasing thermal energy. It allows the PCM to freely move over the entire internal volume of the arrangement, thus improving heat efficiency.

An example is when the PCM freezes due to heat removal due to the cool temperature of the night air. When the outside temperature rises in the day, the air-conditioner will cool the room, but this is aided by the PCM which melts and removes heat. This approach results in 30-40% energy savings. If the outside air is cold enough in the night, “free cooling” which uses the cool outdoor air as a free cooling source, can be used to freeze the PCM and cool the servers, without having to turn on the air-conditioner. This results in an even lower energy consumption.

The control system controls the charging and discharging periods to ensure that the thermal heat management system works at an optimal level to gain even higher energy savings. This also allows the development of energy reports regarding the operation of the energy systems and the amount of saved electricity. 

This thermal energy storage solution is applicable for the following: 

• Data center/telecommunication site cooling: Increases energy efficiency by 20-40%, and reduces the storage size by 60% (compared to water storage solutions)
• District heating and cooling systems: Increases energy efficiency by 20-40%, and reduces the storage size by 60% (compared to water storage solutions)
• Office buildings heating and cooling: Reduced energy consumption and operating costs; help to attain green building certification 
• Industrial heating and cooling solutions and heat recovery

The cooling systems in the IT and telecommunications sector may account for up to 30-40% of the energy demands of such sites. Any reduction in energy cost would result in a significant cost savings for owners, operators, and telecommunication service providers.

The benefits of the technology include: 

• Decreases energy cost by 20-50%: The technology transfers cheap energy to peak periods by increasing and balancing the efficiency of the cooling/heating system
• Backup cooling: There is an energy buffer with an independent control logic that acts as a redundant factor in the event of equipment failure
• Reduced maintenance: Requires less maintenance and offers reduced operation costs
• Reduces CO₂ emission by 30-50% 
• Peak performance management
• Reduced investment costs
• Remote control and data analysis
• Lifetime: minimum 30 years
• Space saving. System is 90% smaller than the traditional water storage solutions and an innovative rectangular shape helps save space
• Average return on investment (ROI) is 3 years