Opinion please – Solar fuel

Transforming sunshine into fuel may seem like an engineer’s pipedream, but Science reports that researchers from CalTech in California and ETH in Zürich have actually produced hydrogen and carbon monoxide by “thermochemical dissociation of CO2 and H2O”.

The gases can be used as feedstock for the synthesis of any hydrocarbon fuel. But as always, there’s a twist: the solar to fuel efficiency is very low – less than 1 percent. For comparison: a standard quality photovoltaic cell typically yields 15 percent.

The process reminds Professor Andrzej Stankiewicz (Mechanical, Maritime and Materials Engineering) of research conducted at Sandia Laboratories in sunny Albuquerque, New Mexico (US). As part of his lectures, the professor shows the lab’s setup for thermochemical CO2-splitting. The working principle is much the same as that reported in Science (24 December 2010): a suitable compound draws oxygen from CO2 and H2O, thus producing CO and H2. Heating the ceramic compound (Sandia uses iron oxide; CalTech/ETH chose ceriumoxide) to temperatures of around 1,500 °Cs makes the oxygen part, after which the cycle can start anew.

The Achilles’ heel in the process as described by Caltech and ETH researchers is the oxygen dissociation: it takes about two hours for the cerium to part with the oxygen, after which it can produce fuel for about two minutes. This asymmetry results in a very low efficiency. Nonetheless, the authors are confident that an efficiency of 16 to 19 should be attainable. Prof. Stankiewicz finds those values highly ambitious and says that re-thinking and drastic improvement of the catalyst nano-structure and the reactor design might improve the efficiency. As an expert in process intensification, Prof. Stankiewicz intends to investigate the same process using microwaves to speed up the heating of the catalyst. Especially in less sunny countries like Holland, speed heating might be a prerequisite for successful solar fuel production.

Professor Hans Geerlings (Applied Sciences) takes another tack entirely. He has been investigating the conversion of sunlight into fuel via another technology, which he claims produces fuel with an overall efficiency of 10 percent or more. Central to his approach is the generation of hydrogen by the electrolysis of water, driven by photovoltaic power. Part of the hydrogen is used for the reduction of carbon dioxide to CO. The mix of hydrogen and carbon monoxide (known as ‘syn-gas’) is the raw material for the synthesis of longer hydrocarbons in a Fischer-Tropsch process. “The technologies may hardly be new,” Prof. Geerlings acknowledges, “but the efficiency is ten times better than the researchers report in Science.” Prof. Geerlings says that electrolysis under pressure may have efficiencies up to 80 percent, and that recent work has been done to improve the conversion of hydrogen and CO2 into water and CO (the reversed water shift reaction). He is now preparing an open letter to inform colleagues of his more efficient alternative conversion from solar to fuel. 

William C Chueh, et al: High-Flux Solar-Driven Thermochemical Dissociation of CO2 and H2O Using Nonstoichiometric Ceria. Science, 24 December 2010.

Delta, 12-06-2008
At football club Sparta they were tired of messing around with ice cubes. Tarek Ghobar and Hicham Shatou of the techno-starter company, IcySolutions, developed a machine that can save them the trouble. 

A bath of cold water to stimulate the bloodstream is just what athletes need to recuperate from a sporting event. That’s what many athletes believe, anyway, and the Dutch national speed skating team is no exception. If the skaters win medals this winter during the Olympics Games in Vancouver, in an event like speed skating where every millisecond counts, who knows, but perhaps their victory will also partially be thanks to IcyDip, a machine that, when connected to a water tap and an electrical socket, delivers a constant stream of ice cold water with adjustable temperatures. No need to mess around with ice cubes anymore.

The idea comes from aerospace and civil engineering graduates Tarek Ghobar (25) and Hicham Shatou (29), who now run their own techno-starters company, IcySolutions. Only three years have passed since they came up with their idea and already they’ve sold a handful of IcyDip machines, the latest one being to NOC*NSF – the Dutch Olympic & Sports Federation. Previous customers included the Dutch football club Sparta, and the German cycling team Milram.

In 2007 the two students were enrolled in the course ‘turning technology into business’, which involved finding applications for a patented technology. They were assigned a patent for making ice slurry. They weren’t particularly keen on making slurry, but they accepted the challenge. “We just wanted to become entrepreneurs,” Ghobar recalls.

After some extensive market research, the two budding entrepreneurs dropped the slurry idea and instead began concentrating on developing a machine that basically works like a fridge. “But smarter and more powerful”, Ghobar explains. “It contains control software that enables it to cool at the desired temperature very quickly.”

The first sports team to show interest was Sparta. “When we plugged it in a socket at the stadium all the lights in the arena went out. We’d blown the fuses. We quickly put sixty meters of extension cord between the plug and the machine to absorb the peak voltage. We were white and pale and had our fingers crossed.”

When the club’s technical director, financial manager and assistant coach arrived about a minute later, the machine worked fine. “The technical director liked it and asked us how much it cost us to make. We threw him a number. ‘Ok,’ he said, ‘leave this one here, send me a bill and go make yourself another prototype’. We weren’t prepared for selling at all”, Ghobar says, laughing.

Editor Redactie

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