Solar Energy

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Radia Lahlou
Research Assistant at SDSU’s Solar Energy Lab (April-September 2013)
French Engineering Diploma in Energy and Environmental Engineering (2013)
National Institute of Applied Sciences (INSA), Lyon, France
Specialization in Thermal Systems Engineering
Equivalent to a combined B.S. and M.S. in Mechanical Engineering

I worked on the issue of carbon particle aerosol generation for the Small-Particle Heat Exchange Receiver (SPHER) http://www1.eere.energy.gov/solar/pdfs/55459.pdf. The volumetric high temperature central receiver uses sub-micron carbon particles dispersed in compressed air to volumetrically absorb solar radiation and heat-up the air to be fed to a gas turbine for electricity production. The particles eventually oxidize before the receiver’s outlet leaving clear air for the gas turbine. The carbon particles size and type determine the absorption and oxidation properties and are therefore to be controlled to ensure optimum receiver efficiency.

A lab-scale carbon particle generator using hydrocarbon pyrolysis previously built at SDSU’s Combustion and Solar Energy Laboratory (CSEL) and tested so far showed limited performance and needed to be scaled up. In this work, I investigated efficient ways of generating the carbon particle aerosol accounting for particles size, mass loading, operating pressure and flow requirements. The required sub-micron particles size and operating pressure raise challenges for the aerosol generation and the particles suspension sustainment. In-situ particles generation and entrainment with a carrier gas versus de-agglomeration and dispersion of pre-manufactured carbon particles in air was investigated. Creating a model of the lab-scale carbon particle generator in order to use it for the scale up was proved of no use. I reported improvements for the lab-scale particle generator in order to increase its yield. I identified a suitable disperser for pre-manufactured particles and ordered it for preliminary tests while other identified alternatives for dispersion still need further investigation. I investigated two types of pre-manufactured carbon particles; vitreous or glassy carbon powder and mainly carbon black. I identified some suitable grades and types of carbon black in terms of dispersion and oxidation. Among others, these carbon black grades will be tested and characterized in terms of oxidation by Mario Leoni. I evaluated as well the coagulation effects of the particles especially between the aerosol generation device and the receiver’s inlet.