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Wednesday, November 24, 2021

Role of Hydrogen in decarbonisation

Hydrogen has been used as a reducing agent in chemical industries for decades but its usage as a fuel is a recent development. It has been demonstrated that it can be electro-chemically combusted using air as an oxidant to generate electricity and heat with only water as by-product. The result? Fuel cell was born. Japan has demonstrated that Fuel cell can be successfully used for transportation applications substituting fossil fuels. The first alkaline fuel cell was used by NASA which was in Gemini spacecraft which was run 1000 hours to demonstrate the long-duration functioning. A fuel cell is like a battery continues to generate current as long as the reactants are supplied. Currently this fuel cell is in Museum. Later Honda of Japan successfully demonstrated the first fuel cell car using compressed Hydrogen around the beginning of this new millennium. It is more than two decades since the fuel cell car was introduced. But it has not been commercially deployed on large scale till date. Though it was a clear demonstration that Hydrogen can substitute gasoline (petrol) successfully and eliminated Carbon pollution emitting only just water vapour and with zero noise pollution. Fuel cell without any mechanical components unlike IC engines was able to generate DC current that runs the propulsion. Unfortunately, it could not substitute IC engines run with gasoline due to high initial cost and lack of filling stations around the world. Though emission is only a harmless water vapour (as being claimed) it is a more potent greenhouse gas (GHG) than CO2 and in combination of CO2 present in the atmosphere it is likely to enhance the global warming by “feedback” effect shown by NASA. Too much water vapour in the atmosphere will have devastating consequences to climate change. “Water vapour feedback can amplify the warming effect of other greenhouse gases, such that the warming brought about by increasing CO2 allows more water vapour to enter the atmosphere…And since water is itself a greenhouse gas, the increase in humidity amplifies the warming from CO2”- NASA. It is unlikely fuel cell transportation will substitute IC engines soon. Electric cars too have their own issues. In either case availability of electricity with zero Carbon emission is the key, without which the consequences of global warming and climate change will remain the greatest threat to the planet earth and the humanity. The only potential role for Hydrogen will be continued to be a reducing agent in a typical redox (reduction -oxidation) reactions in power generation. For example, Carbonaceous fuels such as coal, oil and gas are combusted to generate thermal energy which in turn converted into electricity using IC engines, steam and gas turbines. But bulk of the heat is wasted as a waste heat (potentially contributing to atmospheric warming) achieving low electrical efficiencies with unabated emissions of CO2 in the atmosphere. In such a dire situation the potential use of Hydrogen can only be a reducing agent to reduce oxidized Carbon (CO2) into CH4 to be recycled once again as a fuel. By this way the fossil Carbon can be recycled indefinitely while Hydrogen can be generated from water using a renewable energy source. The trade-off will be between whether renewable energy can be stored in batteries and used as direct electricity or use renewable Hydrogen to be used as reducing agent for decarbonising fossil fuel emissions. Hydrogen using renewable energy will be expensive, but it has a potential to be used a renewable synthetic methane gas (RSMG) for base load power generation on long term basis. Renewable energy using battery storage will be attractive in short term, but it cannot be used for baseload power generation and for larger capacity plants due to high cost of batteries beyond a point. With current power generation capacity exceeding 65% from fossil fuel there is no easy solution to achieve zero emission by 2050. The one and only option will be to use renewable Hydrogen to generate RSMG which can be used as fuel of the future with a potential for Carbon recycling. This is the only way the world has a hope to achieve zero emissions by 2050. US government should impose price on Carbon while subsidising renewable Hydrogen for the purpose of converting it into RSMG. In the beginning RSMG will be more expensive than natural gas but it will eventually substitute natural gas as alternative fuel to generate baseload power with zero emissions. The key will be large scale deployment of renewable energy and reduction of cost of renewable energy to less than $20/Mwh.

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