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Thermal energy harvesting from natural resources and waste heat is becoming critical due to ever-increasing environmental concerns. However, so far, available thermal energy harvesting technologies have only been able to generate electricity from large temperature gradients. Here, we report a fundamental breakthrough in low-grade thermal energy harvesting and demonstrate a device based on the thermomagnetic effect that uses ambient conditions as the heat sink and operates from a heat source at temperatures as low as 24 °C. This concept can convert temperature gradients as low as 2 °C into electricity while operating near room temperature. The device is found to exhibit a power density (power per unit volume of active material) of 105 μW cm −3 at a temperature difference of 2 °C, which increases to 465 μW cm −3 at a temperature difference of 10 °C. The power density increases by 2.5 times in the presence of wind with a speed of 2.0 m s −1 . This advancement in thermal energy harvesting technology will have a transformative effect on renewable energy generation and in reducing global warming.
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Organic Rankine Cycle as a Waste Heat Recovery System for Data Center, Design and Construction of a Prototype
As a result of constantly increasing data center utilization, many challenges have appeared for thermal engineers over the last few decades. Advanced cooling systems for servers are of significant interest, particularly, technologies which can also reduce electricity usage. One known technology called Organic Rankine Cycle (ORC) is considered a viable alternative for this purpose. It can both the heat from a server and then transfer the server heat into a power cycle to generate electricity. This study consists of the design and construction of an experimental prototype of 20kW of waste heat, representing two common rack servers operating at full capacity. The range of server waste heat temperatures is between 60°C to 85°C, which is far below the normal operating range for ORCs. This ultra-low-grade waste heat leads to an expected thermal efficiency between 2%-8%. Tests on the experimental rig showed a maximum thermal efficiency of 3.33%. The system is both absorbing all the waste heat from the data center and at the same time providing an economic benefit back to the data center in form of electricity. Through experimental investigation, this study provides the first evidence for using ORC system as a valid solution for ultra-low-grade waste heat recovery.
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- Award ID(s):
- 1738782
- PAR ID:
- 10065782
- Date Published:
- Journal Name:
- ITHERM
- ISSN:
- 1936-3958
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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