Is Current Model of Hydrogen Powered Economy Really Sustainable?

Latest public announcement by a business giant on betting aggressively on Green Hydrogen by way investing heavily on Renewable Energy and the target of 1-1-1 to produce Green Hydrogen created a buzz.

By name the green hydrogen used electricity produced renewable energy sources for electrolysis process. When the electricity produced from renewable energy sources is converted into hydrogen in power-to-gas plants, “green hydrogen” is produced. It is considered an environmentally friendly energy source and raw material that is easy to transport and store. Renewably-produced hydrogen can be used as fuel for transportation, converted into heat or electricity and used flexibly for domestic energy and electricity supply. Hydrogen, is considered as an enabler for rapid increase in RE power share in a country’s portfolio, ensures that renewable energies are always available in sufficient quantities in the event of weather-related power fluctuations.

Green hydrogen is versatile and can be used innovatively. Hydrogen is the most widespread element on earth and has great innovative potential. It can be used as a fuel or coolant, and to generate electricity and heat, but can also be used as a raw material in industry. Electrolysis technologies are already on the threshold of the growth and profit phase, and fuel-cell systems are already being used successfully today. However, for hydrogen from power-to-gas plants to be successfully marketed economically, a technology-open legal framework needs to be established.
 

Green hydrogen reduces CO2 emissions. Currently, 96% of hydrogen is produced using fossil fuels. The conventional production method produces climate-damaging carbon dioxide that escapes into the atmosphere. In the power-to-gas method, however, water is broken down into hydrogen and oxygen by electrolysis. While further use is made of the hydrogen, the by-product oxygen can either be used for other applications or simply released into the environment.

However, the ethical concern arises, when you break water to produce hydrogen. Simple mathematics say that to produce 1kg of Hydrogen, 9kg of distilled water is required and to make 1 kg of distilled water, you need around 1.25 kg of RO water and further 1kg of RO water requires 1.75 kg of normal water viz. 1 kg of hydrogen needs at-least 20kg of normal water. The numbers when compared with replacing at-least 5% of Oil demand with Hydrogen will require 2.1 billion tons of Hydrogen which in-turn require 42 billion tons of water to be broken. The water loss during cooling at various stages and indirect consumption of water to generate electricity is additional to the above calculation.
 

The water intensity of the transitional hydrogen economy can be roughly and conservatively analyzed by quantifying the direct water requirements to annually manufacture 2 billion Tons of hydrogen by electrolysis. It is determined that up to 42 billion tons of water would be directly consumed as a feedstock, with a total consumption including evaporation of cooling water at various stages of water treatment of 60-70 billion tons annually. Total water withdrawals for thermoelectric cooling (most of which is not consumed) are expected to increase by 25-75%, depending primarily on the aggregate efficiency of electrolysers that will be in place and the portion of hydrogen that is produced by thermoelectrically powered electrolysis. On a per unit basis, thermoelectric power generation for electrolysis will on average withdraw approximately 20 kgs of cooling water and will consume 9kgs of water as a feedstock for every kilogram of hydrogen that is produced using an electrolyser that has an efficiency of 75%. Given that water withdrawals have remained constant if not increasing for decades owing to population pressure and climate change, this increase in water use represents a significant potential impact of the hydrogen economy on a critical resource, and is consequently relevant to water resource planners.

Thus, if minimizing the impact of water resources is a priority and electrolysis becomes a widespread method of hydrogen production, hydrogen production would need to be from hydrogen production pathways that do not use much water (such as wind or solar), or effective water-free cooling methods (e.g. air cooling) will need to be developed and widely deployed.

- Prof. Siddartha Ramakanth, Assistant Professor, Centre for Energy Studies, ASCI