Solar energy is the most limitless, accessible and cost-effective renewable energy. CSP technology holds a pivotal position in the DOE's strategic plan for harnessing solar energy to generate electricity at higher efficiency, enhanced system capacity and better grid stability. Current CSP systems concentrate sunlight with mirrors to heat up molten salt and deliver thermal energy at only 560°C. To achieve the maximum energy efficiency while minimizing costs in next-generation solar power plants, CSP needs to operate at much higher temperatures (>700°C). Sand-like particles have been identified as the most promising heat transfer media for meeting these ambitious targets. I developed Modulated Photothermal Radiometry (MPR), a non-contact frequency-domain technique, to measure high-temperature particle flows in harsh conditions. Using MPR technology, I performed a series experimental and theoretical studies to investigate heat transfer properties of the particle flow, guiding optimal heat exchanger design. These results have been published in top physics and engineering journals and conferences, driving the frontiers of Gen3 CSP design. 

Related Publications: 

MPR technology: 

• X.Zhang*, S.Adapa et al., Physical Review E (2024)

• J.Zeng, X.Zhang et al., Annual Review of Heat Transfer 25 (2022)

Heat transfer of granular media: 

• X.Zhang et al., International Journal of Heat and Mass Transfer (2024), under review

• S.Adapa, X.Zhang* et al., Solar Energy (2024), under review

• X.Zhang et al., ASME Energy Sustainability Conference (2024)

• J.Zeng*, X.Zhang* et al., Journal of Applied Physics (2021)

DEM simulation platform:

• X.Zhang et al., ASME’s International Mechanical Engineering Congress & Exposition (2021)

*Equal contribution

The exponentially growth of artificial intelligence (AI) requires substantial computational power, resulting in considerable heat generation that could exceed 1,000W/cm2. Cooling AI workloads poses a significant challenge for high performance chips. Spray cooling with liquid nitrogen or helium is bulky and inconvenient. Conventional cooling technologies such as heat pipes is only capable of dealing with heat flux 1-2 orders of magnitude lower than this demand due to its fundamental limitation. I engineered a hydrogel-coated glass fiber network to exploit its unique osmotic pressure and extraordinary wettability for maintaining a high fluid supply rate during evaporation. 

Related Publications: 

• J.Zeng, X.Zhang et al., Cell Reports Physical Science (2023)

Wearable devices have been developed for various applications such as sensing, medical and communication. In particular, wearable devices that provide virtual reality (VR) capabilities have achieved remarkable success. There are a lot of advances in improving an immersive visual experience via these devices. It is necessary to supplement these devices with actuators to enhance sensory feedback through tactile interactions beyond just displaying images on a screen. I designed a flexible thermoelectric actuator by combining liquid crystal elastomer (LCE) with thermoelectric (TE) device. The on-going research aims to create fast, compact and energy efficient thermal actuators for applications such as VR, medical prosthetics, and wearable technology.

Intensive human industrial activities have created immense prosperity and convenience, while emitting billion tons of greenhouse-gas into the atmosphere each year, leading to severe environmental problems. To tackle global warming and ocean acidification as a result of CO2 emissions, efforts have been made to develop carbon capture technologies. As the cost of carbon capture acts as one of the largest roadblocks for its application, the use of high temperature molten salts has the potential to reduce the operational cost by recovering the heat generated during reaction. I leveraged the MPR technique to achieve precise characterization of molten borate salt thermal properties at various temperatures and compositions.

Related Publications: 

• K.M.Chung, X.Zhang et al., International Journal of Heat and Mass Transfer (2023)