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
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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.
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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
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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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