Alejandro Gracia-Zhang

MIT Department: Mechanical Engineering
Undergraduate Institution: Harvard College
Faculty Mentor: Asegun Henry
Research Supervisor: Mehdi Pishahang, PhD, Caleb Amy, Colin Kelsall
Website: LinkedIn, Portfolio

Biography

My name is Alejandro Gracia-Zhang and I am from Ukiah, CA. I am a rising senior studying Mechanical Engineering at Harvard University. I’m interested in renewable energy and in ways that engineering that can positively impact communities in developing countries. I enjoy art, music, being outside when it’s warm, visiting new places and revisiting old places, and spending time with friends.

2019 Research Abstract

High Temperature Coatings for Cement Infrastructure Concentrated Solar Power

Alejandro Jose Gracia-Zhang1, Mehdi Pishahang2, Asegun Henry3
1School of Engineering and Applied Science, Harvard University,
2, 3Department of Mechanical Engineering, Massachusetts Institute of Technology

Concentrated solar power (CSP) is a reliable, emissions-free source of electric power.  CSP plants have the potential to be much more cost effective if the temperature of the molten salt used is increased to 750 °C, since the efficiency of the steam turbines increase with higher temperature differences, and the chloride salts used for higher temperatures are cheaper than the conventional nitrate salts.  However, current metal alloys used for CSP tanks and pipes that can withstand molten chloride salts at 750 °C are expensive. Castable cements have been proposed as an economical alternative material for the CSP infrastructure; these cements are insulating, have smooth surfaces that allow sealing between pipe flanges, and are inexpensive . However, the molten chloride salts slowly penetrate the cement, corroding it and decreasing the cement’s lifespan. There are certain high temperature ceramic coatings that are potentially effective in protecting the cement from the molten salt corrosion. With an in-depth understand of the chemistries of the salts and cements, this project tested multiple coatings in a furnace that was in an inert environment and used Scanning Electron Microscopy and X-Ray Diffraction to analyze the penetration and reactions of the salt through the coating. Initial results show that Silicon Carbide coating resists corrosion from the molten salt and decreases penetration of the salts in the cements. This is a significant step in ensuring the cement infrastructure can last for the lifespan of the CSP plants operating with chloride salts at 750 °C, which would make the system well below well below the goal of $15/kWh-t.