Duke University’s Hybrid Solar System Produces Hydrogen

Duke University assistant professor of material sciences and mechanical engineering Nico Hotz has come up with a fantastic rooftop photovoltaic system that converts the solar energy not into electricity but gives out hydrogen that can be later on used in the fuel cells. Unlike the conventional photovoltaic set up, it doesn’t require silicon based solar panels for energy conversion. Instead, this hybrid model uses sun’s rays to heat up a mixture of water and methanol in a panel made up of zigzag arrangement of glass tubes and generally placed on your rooftop. The water reacts with the methanol by absorbing the heat and after two catalytic reactions has taken place; the resultant hydrogen is much purer than that obtained using other techniques. Also, this technology for Hydrogen production is cheaper than all the other current alternatives.

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Schematic of the hybrid solar system

Exergy is a term used to calculate the maximum amount of input energy that can be theoretically converted into useful work. Thus a device or method with better exergetic parameters will have much more efficiency and conversion rate. Hotz compared his approach with 3 distinct alternative technologies for exergy results and found out his to be the best. And statistics prove this new and unorthodox approach a success. Hotz’s technology achieved exergetic efficiencies of 28.5 percent in the summer and 18.5 percent in the winter. The other techniques came a distant second with 5 to 15 percent in the summer, and 2.5 to 5 percent in the winter. Hotz's comparisons took place during the months of July and February in order to measure each system's performance during summer and winter months.

Prof. Hotz had also presented a paper describing the results and findings of his hybrid solar system for hydrogen production at the ASME Energy Sustainability Fuel Cell 2011 conference in Washington, D.C and secured the first prize for this awesome piece of research. He did his post graduation from University of California, Berkeley where he started with this project. Now, at Duke, he is planning to construct a practical model to check out its actual efficiency.

In this system, initially the sunlight is gathered by the traditional looking solar collector. However, the collector consists of aluminum and aluminum oxide coated thin capillary like copper tube network through which a combination of water and methanol flows. The tubes are vacuum filled so that the solution is free from any contaminants. However, a small amount of catalytic nanoparticles are present in them. This collector is able to successfully capture 95% of the incident light. Such large amount of heat enables it to achieve really high temperature up to 200º C. The evaporated liquid comes in contact with the nanoparticles and the reaction takes place resulting into hydrogen production. The hydrogen can be either compressed or stored in cylinders for future use or can be immediately supplied to fuel cells for conversion into electricity. This simple rooftop generator is also the cheapest and efficient system that can compete in performance and costs with the commercial fossil fuel based generators. This alternative solution can truly be used for securing a greener and cleaner future.

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