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Powering buildings with hydrogen

24 July 2013

Dr Chua with his hydrogen-producing system on the rooftop of an NUS Engineering block
The search for harvesting low-cost hydrogen, an alternative energy source, has taken a step closer to reality with the recent discovery by a group of NUS engineers. 

Existing methods of hydrogen production with little or no carbon in the process include electrolysis to “split” water into hydrogen and oxygen. However, this is a costly technique due to the amount of energy required, and the yield is low.

Dr Ernest Chua Kian Jon and his team from the Department of Mechanical Engineering and Engineering Science Programme at the NUS Faculty of Engineering have integrated two processes – photocatalysis and electrolysis – to channel the energy in sunlight to produce hydrogen from water.

Dubbed the Photocatalysis-Electrolysis-Photovoltaic Tri-hybrid System, the inventors have set up a rooftop pilot comprising three reactor tubes, an innovative hybrid hydrogen filtration system, and two solar panels.

Each reactor tube can produce about 40 litres of hydrogen per hour, which works out to enough fuel to power the communal lights of one building level when all three are working. One level of a typical public residential building can save S$1,000 to S$1,500 annually in electricity costs.

The system is able to function ceaselessly around the clock, powered by solar energy and backed by solar-charged batteries during the night. It works with different types of water, but natural sources containing compounds that accelerate photocatalysis, such as rainwater, would be better.

Water is pumped through the reactors and low-cost efficient photocatalysts are added to speed up the water-splitting process. Once separated, the hydrogen can be piped to a storage system, while the oxygen returns to the air or stored for other applications.  

The separation process is supported by a hybrid mechanism, such that only one or two filtration membranes are needed; too many will increase the risks of fouling. “This way, we can achieve almost perfect purity, 99.8 per cent, a level that is highly desirable in many clean-fuel processing industries,” explained Dr Chua.

He said that by tapping renewable resources such as water and sunlight, the method provides an inexpensive and clean way to produce hydrogen that can be used to provide backup power for buildings. “This system can be implemented easily on the rooftops of any buildings, converting them into energy-generating ones. It will also provide extra shielding from sunlight on rooftops, resulting in a cooler indoor environment due to reduced solar heat gain,” he added.

The project received a National Research Foundation Proof-of-Concept grant for bulk hydrogen production demonstration, and was supported by Singapore Technologies Kinetics Ltd.

“Based on this rooftop design, we can design larger-scale system for bulk hydrogen production, say on the reservoir bed,” said Dr Chua. The team is exploring with department colleague Professor Wang Chien Ming on setting up the system on floating platforms.