Hydrogen

In the course of evolution, humankind has learned, to a certain extent (only), the art of extracting energy from chemical species that nature has graciously endowed. The focus and emphasis has been on a combination of Carbon and Hydrogen compounds, primarily due to ease of availability in harvestable form and abundant quantity. Energy from Carbon and Hydrogen based compounds has primarily been extracted through the combustion route wherein Carbon and Hydrogen react with Oxygen releasing heat and producing Carbon Dioxide [ CO2 ] and Dihydrogen Oxide or Oxidane (fancy name for Water) [ H2O ] as the byproducts.
While both Carbon and Hydrogen are constituent elements of energy compounds, the respective products of combustion, CO2 and H2O have contrasting environmental implications. While Oxidane, the product of combustion of Hydrogen with Oxygen, condenses to liquid water (the elixir of life) once it is in the atmosphere, Carbon combustion with Oxygen results in Carbon Dioxide, a major contributor to global warming through the green house effect. With the current level of Carbon Dioxide in the atmosphere already resulting in unprecedented and potentially irreversible warming of atmosphere, curtailment of further CO2 emission has become absolutely critical.
The simplest approach of curtailing CO2 emission is through the displacement of Carbon from energy compounds. For the simplest approach to become practical, the displaced Carbon has to be replaced with alternate energy compound. In the current context of overbearing dependence on thermo-chemical conversion process, Hydrogen is the only energy specie that can displace Carbon. As such, efforts are being directed at generating Hydrogen from a variety of resources.
The current segment presents a multifaceted analysis of Hydrogen as an energy specie to displace Carbon from the energy mix.


01 Natural Hydrogen Carriers Click Here 02 Hydrogen Type Classification Click Here
03 Pricing Hydrogen on Equivalent Energy Basis Click Here

Natural Hydrogen Carriers


Hydrogen is the lightest of Baryonic matter (anything constituted of electrons, protons and neutrons) in the universe and is an important energy specie. In nature (atleast on earth), Hydrogne is not available in its free, directly useable state of molecular H2. Hydrogen predominantly appears bound with Carbon and/or Oxygen in three compounds of;

Dihydrogen monoxide OR Water - H2O
Biomass - C1.0H1.4O0.6
Fossilized Hydrocarbon - CXHY

Dihydrogen monoxide, H2O, collectively in its solid, liquid and gaseous form is the most prominent of the Hydrogen carrying compounds. Through the process of photosynthesis, H2O enters into vegetation. It is interesting to note that the generic chemical formula biomass C1.0H1.4O0.6 can be written in oversimplified form as C1.00.7(H2O) taking some liberty in term of potential elemental uncertainties. The colocation of H2O in the biomass structure is clearly evident from the simplified formula of biomass. Subsequently, as biomass gets cooked under high temperature and pressure conditions over millions of years, Hydrocarbons are formed.

It may be noted that, in moving Hydrogen from water [H2O] to Biomass [C1.00.7(H2O)] and subsequently to Hydrocarbons [CXHY], nature invests energy. The energy that nature invests is reflected in terms of energy that can be extracted from each of the compounds on oxidation. Another very interesting analysis is that since nature inherently invests energy in moving Hydrogen up the value chain, if pure molecular Hydrogen [H2] has to be recovered from these compounds, the amount of energy that needs to be externally invested reduces as one moves from water [H2O] to Biomass [C1.00.7(H2O)] and subsequently to Hydrocarbons [CXHY]. Thus, generation of pure Hydrogen from Hydrocarbons is the cheapest route, followed by from Biomass and finally, extraction from water is the most expensive route. The following table consolidates some such critical facts corresponding to the three Hydrogen carriers.

Sr.No Parameter Units Hydrogen carrying compounds
01 Compound Water Biomass Hydrocarbon(s)
02 Chemical formula   a -- H2O C1.00.7(H2O) CH4
03 Combustible Nature Non Combustible Combustible Combustible
04 Lower Calorific Value MJ/kg 0.0 ~ 16 ~ 50
05 Inherent Hydrogen Content   b g/kg 111.11 56.91 250.00
06 Hydrogen Generation Process   c Electrolysis Oxy-Steam Gasification SMR & WGS
07 Inherent Hydrogen Potential   d g/kg 111.11 219.51 500.00
08 Inherent Carbon Footprint   e g/kg 0.0 1788.6 2750.0
09 Process Electricity Requirement   f kWh/kg ~ 55 ~ 2.9 ~ 2.9
10 Process Efficiency   g % ~ 18.3 ~ 46.8 ~ 45.7
11 Process Net Energy Ratio   h 0.18 3.47 3.47
a Methane has been used as a representative Hydrocarbon as it is widely used for Hydrogen generation.
b

Estimated as the ratio of product of number of H atoms and H molecular weight (1 kg/kmol) to the compound molecular weight.

Example for biomass would be [1.4/(12+1.4+0.7*16) = 1.4/24.6 = 0.05691 kg Hydrogen per kg Biomass]

c

Oxy-Steam gasification converts biomass to a gaseous mixture of H2;CO;CH4; CO2. Mixture separation (typically swing adsorption process) enables generation of pure stream of Hydrogen.

SMR is Steam Methane Reforming (CH4 + H2O = CO + 3H2) and WGS is Water Gas Shift (CO + H2O = CO2 + H2). The collective reaction will be CH4 + 2H2O = CO2 + 4H2. Mixture separation (typically swing adsorption process) enables generation of pure stream of Hydrogen.

d

The inherent Hydrogen potential indicates the maximum theoretical Hydrogen that can be produced considering the potential of the inherent Carbon to reduce Water (Steam). Every atom of Carbon can theoretically produce two Hydrogen molecules through the reaction C + 2H2O = CO2 + 2H2 (practically this is a homogeneous - heterogeneous combination reaction).

e

The inherent Carbon footprint corresponds strictly to the quantity of Carbon Dioxide that is formed from the inherent Carbon present in the base compound. There is one atom of Carbon in both Biomass and Methane which is used for reducing Water(Steam) and generate H2O. Each Carbon atom will form one molecule of Carbon Dioxide in generating Hydrogen. No Carbon Dioxide emission pertaining to process energy requirement is considered in this assessment.

f,g,h

The numbers correspond to a typical 10 kg/h Hydrogen generation plant.


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Hydrogen Type Classification


Hydrogen as a fuel has multiple applications ranging from use in industrial burners for thermal energy to use in space vehicles for propulsion. Depending on the end utility, quality specifications (purity of Hydrogen and permissible contaminants with their limits) have been established and Hydrogen as a fuel must mandatorily meet such specifications to safeguard the terminal use systems. Towards establishing the specifications, Hydrogen as a fuel has been classified into different types (I,II,III) as the first categorization followed by grades (A,B,C,D,E) for each type and finally category for each grade (1,2,3). Thus, depending on the terminal application, Hydrogen is categorized in Type-Grade-Category format. It is however important to note that while TYPE is mandatorily assigned to Hydrogen, not all applications have a GRADE and CATEGORY. The Type, Grade and Category description for Hydrogen are presented as below.

Type - I

Gaseous Hydrogen

Type - II

Liquid Hydrogen

Type - III

Slush Hydrogen #

#   Slush Hydrogen is a mixture of liquid and frozen Hydrogen in equilibrium with the gas phase Hydrogen at its triple point (13.8 K). Slush Hydrogen is currently used exclusively for Aircraft and Spacecraft propulsion applications.

Type - I / Grade - A
  • Hydrogen fraction (by volume) in gas should be minimum 98.000%
  • Internal combustion engines for transportation application.
  • Other residential and commercial combustion applications like boilers, cookers etc.
  • Excludes Proton Exchange Membrane Fuel Cell based systems
Type - I / Grade - B
  • Hydrogen fraction (by volume) in gas should be minimum 99.900%
  • Industrial use for power generation applications (like stationary combustion engines OR gas turbines).
  • Industrial use for heating applications (using direct/radiant burners).
  • Excludes Proton Exchange Membrane Fuel Cell based systems
Type - I / Grade - C
  • Hydrogen fraction (by volume) in gas should be minimum 99.995%
  • Ground support systems for aircraft and Space vehicles
  • Excludes Proton Exchange Membrane Fuel Cell based systems
Type - I / Grade - D
  • Hydrogen fraction (by volume) in gas should be minimum 99.97%
  • Proton Exchange Membrane Fuel Cell based road vehicles
Type - I / Grade - E
Category - 1
  • Hydrogen fraction (by volume) in gas should be minimum 50.00%
  • PEM Fuel Cells for Stationary Systems : Low power - High efficiency systems
Category - 2
  • Hydrogen fraction (by volume) in gas should be minimum 50.00%
  • PEM Fuel Cells for Stationary Systems : High power systems
Category - 3
  • Hydrogen fraction (by volume) in gas should be minimum 99.90%
  • PEM Fuel Cells for Stationary Systems : High power - High efficiency systems

Type - II / Grade - C
  • Hydrogen fraction (by volume) in gas should be minimum 99.995%
  • Aircraft and Space vehicle on-board propulsion systems
  • Aircraft and Space vehicle electricity requirements
  • Off road vehicles (through the combustion or electrochemical route)
Type - II / Grade - D
  • Hydrogen fraction (by volume) in gas should be minimum 99.97%
  • Proton Exchange Membrane Fuel Cell based road vehicles

Type - III
  • Hydrogen fraction (by volume) in gas should be minimum 99.97%
  • Aircraft and space vehicle on-board propulsion.

NOTE :- Reviewing the consolidated information, it is evident that the most stringent quality requirement (on Hydrogen volume fraction basis) is for Aircraft/Space vehicle applications followed by Proton Exchange Membrane fuel cell systems for automotive applications. The least stringent requirements are for Proton Exchange Membrane fuel cell systems used in stationary power generation applications and other combustion systems. It is however also important to note that there are stringent restrictions on what constitutes the balance (100 - Hydrogen volume fraction) and that aspect is described in discussing the individual standards.


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Pricing Hydrogen on Conventional Hydrocarbon Equivalent Energy Basis


In the context of the present-day technological development, Hydrogen as an alternative to Carbon based fuel(s) for curtailing green house gas emissions is a settled debate. While there are a number of techno-economic challenges in respect of Hydrogen as a fuel, the aspect hogging the most limelight is the costing. Some aggressive pricing models are pitching for Hydrogen generation at 1 USD a kilogram. In the context of Hydrogen pricing, the perspective, at the minimum should be from the price point of convention fossilized hydrocarbon energy. Such a perspective is being proposed, under a hypothetical scenario of complete displacement of fossilized Hydrocarbons by Hydrogen, considering that any aggressive pricing for Hydrogen can potentially push the availability timelines of Hydrogen to a much later date into the future while any liberal pricing of Hydrogen has the potential to induce destabilizing inflation. As such a range of sensitive factors will have to be considered and accounted for in the pricing of Hydrogen. The following calculations arrive at Hydrogen costing from equivalent liquid and gaseous hydrocarbons perspective.

Lower calorific value of Hydrogen on mass basis 120 MJ/kg
Lower calorific value of Hydrogen on volume basis (1 bar / 25 deg C) 9.68 MJ/m3
Average cost of crude oil (USD basis) - June 2022 110 USD/barrel
Average cost of crude oil (INR basis @ Rs 80 per USD) - June 2022 8800 Rs/barrel
Energy equivalent for one barrel of crude 6004 MJ/barrel
Cost of crude per unit energy (USD basis) 0.0183 USD/MJ
Cost of crude per unit energy (INR basis) 1.4657 Rs/MJ
Cost of Hydrogen on energy equivalent basis (USD basis @ Rs 80 per USD) 2.2 USD/kg
Cost of Hydrogen on energy equivalent basis (INR basis) 175.88 Rs/kg


In regards to the above pricing, the basic challenge is that the crude as received will not be in the ready to use form and will have to be processed in a refinery. Typically, about 85% of crude in a barrel is refined to Gasoline + Diesel + Jet fuel + LPG with an average calorific value of about 45 MJ/kg. In the course of refining, additional cost gets added. It is reported that typically about 15% of the base crude cost is the additional cost of refining. Considering about 85% recovery from the barrel for automotive refined fuels and 15% as the refining cost. The new costing for Hydrogen on equivalent energy basis evolves as below.

Lower calorific value of Hydrogen on mass basis 120 MJ/kg
Lower calorific value of Hydrogen on volume basis (1 bar / 25 deg C) 9.68 MJ/m3
Average cost of crude oil + refining cost (USD basis) - June 2022 126.5 USD/barrel
Average cost of crude oil + refining cost (INR basis @ Rs 80 per USD) - June 2022 10120 Rs/barrel
Energy equivalent for one barrel of Gasoline + Diesel + Jet fuel + LPG 5103.4 MJ/barrel
Cost of crude per unit energy (USD basis) 0.0248 USD/MJ
Cost of crude per unit energy (INR basis) 1.9830 Rs/MJ
Cost of Hydrogen on energy equivalent basis (USD basis @ Rs 80 per USD) 3.0 USD/kg
Cost of Hydrogen on energy equivalent basis (INR basis) 237.96 Rs/kg


The same analysis can be extended to Natural Gas. The following table presents the typical energy equivalent costing of Hydrogen. Note that no processing cost for Natural Gas is considered.

Lower calorific value of Hydrogen on mass basis 120 MJ/kg
Lower calorific value of Hydrogen on volume basis (1 bar / 25 deg C) 9.68 MJ/m3
Average cost of Natural Gas (USD basis) - June 2022 6.22 USD/MMBtu
Average cost of Natural Gas (INR basis @ Rs 80 per USD) - June 2022 497.6 Rs/MMBtu
Average cost of Natural Gas energy basis (USD basis) 0.0059 USD/MJ
Average cost of Natural Gas energy basis (INR basis @ Rs 80 per USD) 0.4716 Rs/MJ
Cost of Hydrogen on energy equivalent basis (USD basis @ Rs 80 per USD) 0.7080 USD/kg
Cost of Hydrogen on energy equivalent basis (INR basis) 56.59 Rs/kg


It is important to note that on Natural Gas energy equivalent basis the cost of Hydrogen is extremely low primarily due to the fact that the energy base cost of Natural Gas itself is extremely low. It is over 75% cheaper than refined crude.


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