The energy of the sun, wind and sea might quickly mix to supply clean-burning hydrogen fuel, based on a staff of Penn State researchers. The staff integrated water purification know-how into a brand new proof-of-concept design for a sea water electrolyzer, which makes use of an electrical present to separate aside the hydrogen and oxygen in water molecules.
This new methodology for “sea water splitting” might make it simpler to show wind and photo voltaic vitality right into a storable and moveable fuel, based on Bruce Logan, Kappe Professor of Environmental Engineering and Evan Pugh University Professor.
“Hydrogen is a great fuel, but you have to make it,” Logan mentioned. “The only sustainable way to do that is to use renewable energy and produce it from water. You also need to use water that people do not want to use for other things, and that would be sea water. So, the holy grail of producing hydrogen would be to combine the sea water and the wind and solar energy found in coastal and offshore environments.”
Despite the abundance of sea water, it’s not generally used for water splitting. Unless the water is desalinated previous to coming into the electrolyzer – an costly additional step – the chloride ions in sea water flip into poisonous chlorine gasoline, which degrades the gear and seeps into the surroundings.
To stop this, the researchers inserted a skinny, semipermeable membrane, initially developed for purifying water in the reverse osmosis (RO) therapy course of. The RO membrane changed the ion-exchange membrane generally utilized in electrolyzers.
“The idea behind RO is that you put a really high pressure on the water and push it through the membrane and keep the chloride ions behind,” Logan mentioned.
In an electrolyzer, sea water would not be pushed via the RO membrane, however contained by it. A membrane is used to assist separate the reactions that happen close to two submerged electrodes – a positively charged anode and a negatively charged cathode – related by an exterior energy supply. When the energy is turned on, water molecules begin splitting at the anode, releasing tiny hydrogen ions known as protons and creating oxygen gasoline. The protons then go via the membrane and mix with electrons at the cathode to kind hydrogen gasoline.
With the RO membrane inserted, seawater is saved on the cathode aspect, and the chloride ions are too huge to go via the membrane and attain the anode, averting the manufacturing of chlorine gasoline.
But in water splitting, Logan famous, different salts are deliberately dissolved in the water to assist made it conductive. The ion-exchange membrane, which filters ions by electrical cost, permits salt ions to go via. The RO membrane doesn’t.
“RO membranes inhibit salt motion, but the only way you generate current in a circuit is because charged ions in the water move between two electrodes,” Logan mentioned.
With the motion from the greater ions restricted by the RO membrane, the researchers wanted to see if there have been sufficient tiny protons transferring via the pores to maintain a excessive electrical present.
“Basically, we had to show that what looked like a dirt road could be an interstate,” Logan mentioned. “We had to prove that we could get a high amount of current through two electrodes when there was a membrane between them that would not allow salt ions to move back and forth.”
Through a collection of experiments just lately printed in Energy and Environmental Science, the researchers examined two commercially obtainable RO membranes and two cation-exchange membranes, a kind of ion-exchange membrane that permits the motion of all positively charged ions in the system.
Each had been examined for membrane resistance to ion motion, the quantity of vitality wanted to finish reactions, hydrogen and oxygen gasoline manufacturing, interplay with chloride ions and membrane deterioration.
Logan defined that whereas one RO membrane turned out to be a “dirt road,” the different carried out nicely compared to the cation-exchange membranes. The researchers are nonetheless investigating why there was such a distinction between the two RO membranes.
“The idea can work,” he mentioned. “We do not know exactly why these two membranes have been functioning so differently, but that is something we are going to figure out.”
Recently, the researchers acquired a $300,000 grant from the National Science Foundation (NSF) to proceed investigating sea water electrolysis. Logan hopes their analysis will play a important function in decreasing carbon dioxide emissions round the world.
“The world is looking for renewable hydrogen,” he mentioned. “For example, Saudi Arabia has planned to build a $5 billion hydrogen facility that is going to use sea water. Right now, they have to desalinate the water. Maybe they can use this method instead.”