Making hydrogen fuel from solar energy is pure green idea - Elko Daily Free Press

Making hydrogen fuel from solar energy is pure green idea

You have to agree that hydrogen is the ideal fuel.

Hanington

Although it is not a "natural" fuel, and not available from the Earth by drilling or mining, hydrogen can be readily produced simply by splitting molecules of water with an input of electrical energy derived from a source such as a large solar cell.

But maybe the greatest advantage that hydrogen has, at least from an environmental standpoint, is the fact when hydrogen burns with oxygen, its only combustion product is … water! None of the traditional fossil-fuel pollutants such as carbon monoxide (CO), carbon dioxide (C02), sulfur dioxide (S02), particulates, photochemical oxidants and so on are produced in a hydrogen flame.

Nobody can fault it, and it’s coming soon to your house and car because it makes sense.

Let’s see if this is practical to make hydrogen from sunlight. We sure don’t want to make it from fossil fuels (as it is being made now) and because of our spineless government, nuclear power accounts for less than 20% of our energy needs and is a long way off in the future.

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To see if this is feasible, consider a large solar cell field 1 mile square. Since the power delivered from the sun to the Earth’s surface is about one kilowatt per square meter, the large array would produce 2.58E6 kilowatts maximum in full sunlight, assuming the cells were pointing directly and track the sun in its path across the sky. But, let’s say we were cheap and just laid them flat. We would have to use the cosine of our angle on Earth (41 degrees for Elko), so we would only get 75% of the incoming energy — still not too shabby — and we don’t have to worry about any complicated pointing mechanisms. Countries on the equator don’t have this concern and tilting isn’t required.

How much would this cost? Figure about $20 per square foot, so the 1-mile-square array would cost $557 million — and this may seem like a lot of money but it will return energy. With an average solar cell efficiency of 11%, and the fact that the sun is gone half the time, we would only get back 106 megaJoules on average every second, figuring over a 24 hour period. This corresponds to $3.53 back every second at the rate of 12 cents per kilowatt hour (from my electric bill). We would get back about $304,000 a day and it would take 5 years to recoup our investment.

So far so good. But we should think about providing power at night as well from our power system.

That’s where the idea of storing some of this energy by making hydrogen gas comes into use. Placed in sealed tanks at a relatively high pressure, the hydrogen can power generators in the evening providing clean continuous energy to our cities.

How efficient is this conversion of water to hydrogen gas? Large-scale industrial plants that do this say it’s about 70%, so we again take a hit in the process. However, there is some good news on the horizon — scientific teams are working on processes to make the generation of hydrogen more efficient.

Just last week, researchers at Oregon State University developed a material that shows a remarkable ability to convert water into clean hydrogen. According to their website, a collaboration led by Kyriakos Stylianou of the OSU College of Science created a photocatalyst that enables the high-speed, high-efficiency production of the gas using a material that utilizes a crystalline, porous material known as a metal organic framework, usually abbreviated as MOF.

Made up of positively charged metal ions surrounded by organic “linker” molecules, MOFs have nanosized pores and adjustable structural properties. They can be designed with a variety of components that determine the MOF’s special properties.

In this study, researchers used a MOF to derive a metal oxide heterojunction — a combination of two materials with complementary properties — to make a catalyst that, when exposed to sunlight, quickly and efficiently splits water into hydrogen and oxygen. This heterojunction, which they refer to as RTTA, features MOF-derived ruthenium oxide and titanium oxide doped with sulfur and nitrogen. They tested multiple RTTAs with different amounts of the oxides and found a clear winner.

“Among various RTTA materials, RTTA-1, with the lowest ruthenium oxide content, exhibited the fastest hydrogen production rate and a high quantum yield,” Stylianou said according to the university website. In just one hour, he noted, a gram of RTTA-1 was able to produce over 10,700 micromoles of hydrogen.

“The remarkable activity of RTTA-1 is because of the synergistic effects of the metal oxides’ properties and surface properties from the parent MOF that enhance electron transfer,” Stylianou said. “This study highlights the potential of MOF-derived metal oxide heterojunctions as photocatalysts for practical hydrogen production, contributing to the development of sustainable and efficient energy solutions.”

We will see this if this method will beat the current electrolytic process for producing hydrogen from water. Typical numbers show that this is about 60% efficient currently. Based on this, our 1 mile solar array will generate at least 17E6 cubic feet of hydrogen per day, about 100,000 pounds. This will enable 42,000 cars (probably all of Elko County) to drive 300 miles every day. Again, not too shabby. Perhaps this new method by OSU will improve this value.