Rooftop hydrogen is the next big thing. Although it is still a few years away, many in the scientific community and industry believe it will happen sooner or later.
Consider an electrolyzer on your roof, which is connected to a cylinder or pipelines that run to a large tank in your basement. You put water in one of the device’s chambers. Your cylinder or tank is full of hydrogen the next day, which you can use to power your automobile or cook with.
The intransigence of India’s state-owned energy distribution firms has played a large role in the problem with rooftop solar. In India, rooftop solar expansion has been limited by a lack of guaranteed offtake for extra energy generated and poor pricing paid for it.
Previously, storing solar energy in batteries was a costly proposition, but the dramatic decline in battery costs is encouraging. However, since the world is rapidly heading toward hydrogen, there is a viable battery alternative.
Again, the electricity from the rooftop solar plant may be used to split water right on the roof to produce hydrogen; better still, emerging technologies are allowing photolysis – splitting water directly using sunlight without the use of electricity — utilizing photoelectrochemical cells (PEC).
Prof Aravind Kumar Chandiran, the head of IIT Madras’ Solar Energy Research Group, claimed in August the invention of “a novel substance” (a “distorted hallide perovskite”) that can divide water under sunshine.
Prof Mohammed Qureshi of IIT Guwahati recently stated that his team created a catalyst (cobalt-tin layered double hydroxide and bismuth vanadate) that can split water into hydrogen and oxygen when employed as a ‘photoanode.’
Prof. Qureshi told Quantum that it’s too early to say whether this could be scaled down for a rooftop plant, but many others in academia and industry believe modest hydrogen producers will become commonplace in the future.
Even if you ignore technology for splitting water straight from sunlight and focus solely on traditional electrolysis, there is plenty of evidence that small-scale hydrogen plants are on the way.
“These are technologies where size does not matter,” says Arne Ballantine, CEO and co-founder of Ohmium, a US-based business that has begun producing electrolysers in Bengaluru.
“Yes, the concept of ‘rooftop hydrogen’ becomes quite real,” Ballantine said, adding, “We are going past the world of chemical plants, when the most efficient method to create hydrogen was with a massive installation.”
According to the business’s Executive Chairman, Umesh Sachdev, a newly formed company named Hydrogenium Resources is in talks with rooftop solar installers about installing small electrolysers alongside solar plants to manufacture hydrogen from surplus solar power.
Sebastian-Justus Schmidt, the Chairman of Enapter, a German electrolyser manufacturer, has mentioned devices the size of microwave ovens. They can be connected to a solar plant on the roof.
“Today, we only need 4.4 kWhr of power to make one cubic metre of hydrogen,” Schmidt remarked in a news statement in February 2020.
A 1 kW rooftop solar plant now typically produces 4.4 kWhr of power.
Small electrolysers are already being produced by companies like the Pure Energy Centre in Scotland and H2B2 in Spain.
“By 2030, demand for hydrogen is predicted to expand by a factor of 1,000 or more, and decentralized systems that produce the gas on-site with no transportation costs will make a major difference,” Schmidt added.
Households on rooftops or other on-premise plants may clearly produce (and consume) hydrogen.
It’s something Ballantine is adamant about. “Water electrolysis, or electrochemical hydrogen creation, will follow semiconductor and chip patterns. “Mini-, micro-, and nano-structuring will continue to win,” he predicts.
Of course, cost is an issue today — one estimate puts the cost of rooftop hydrogen at roughly $7.50 per kg due to electrolyser costs; but solar photovoltaic modules, too, were selling for over a dollar per watt-peak before falling to a fifth in less than five years. Scale will help cut down the cost of electrolyser manufacturing as it develops traction.
The ‘cold-start’ and ‘quick start-stop’ cycle characteristics are crucial enablers for rooftop hydrogen, according to Chock Karuppiah, Ohmium’s CTO.
Photoelectrochemical systems “may appear to be an excellent option” for splitting water straight from sunlight without the use of electricity, according to Karuppiah, but there are other obstacles to solve.
“The design of a single device solution must strike a balance between a variety of requirements” (properties of light, ionic species, electrical flows, liquid water and gaseous hydrogen). “It’s quite difficult to execute that well in a single device,” Karuppiah explained.
He went on to say that combining solar cells and electrolysis cells will speed up commercialization.
