Nepal is currently reeling under acute fuel crisis due to undeclared economic blockade by India. Transportation and cooking are two main areas that have been severely affected due to the fuel shortages. Alternative sources of cooking fuels have become a crucial topic of research and investigation on an international scale and Nepal may require such unconventional solutions to cope with the crisis that does not seem to be winding down anytime soon. The utilization of Hydrogen as an energy carrier with regards to domestic cooking has been explored and studied by countless experts over the years and is still a relatively novel concept that requires further exploration.
2. Hydrogen facts
Lightest
Most abundant
Colourless
Odourless
Non-toxic
Non-carcinogenic gas
Not found by itself on Earth but in its
molecular form combined with another
chemical as a compound (e.g. water, methane)
3. How can it be produced?
Water electrolysis using any power source including wind,
solar, nuclear power
Gasification of Coal
As a by-product from reforming natural gas/biogas with steam
From gas or biomass-derived alcohols
4. Electrolysis
Using electricity to split water into hydrogen & oxygen
Reaction takes place in electrolyzers
Decomposition of water (H2O) into oxygen (O2) and hydrogen
gas (H2) due to an electric current being passed through water
5. Electrolyzers
Consist of an anode and cathode separated by an electrolyte
producing an electrically conducting solution when dissolved in
water
Three types of electrolyzers:
PEM (Polymer Electrolyte Membrane)
Alkaline
Solid Oxide
PEM Electrolyzer:
Electrolyte is a solid speciality plastic material
Electrons flow through external circuit and hydrogen ions
selectively move across the PEM to the cathode
Combine with electrons from external circuit to form hydrogen gas
Operates at 70°-90°C
6. Alkaline Electrolyzer:
Use of liquid alkaline solution of sodium or potassium hydroxide as
the electrolyte
Transport of hydroxide ions through the electrolyte from cathode
side to anode side
Operates at 100°-150°C
Solid Oxide Electrolyzer:
Use of solid ceramic material as the electrolyte
Selective conduction of negatively charged oxygen ions at elevated
temperatures
Operates at much higher temperatures for the functioning of solid
oxide membranes : 700°-800°C
7. The Process
Hydrogen gas produced at cathode (-ve)
Reduction reaction with electrons from cathode given to hydrogen
cations
2H+
(aq) + 2e- H2 (aq)
Oxygen gas produced at anode (+ve)
Oxidation reaction giving electrons to the anode
2H2O (l) O2 (g) + 4H+
(aq) + 4e-
8. Overall Reaction : 2H2O (l) 2H2 (g) + O2 (g)
Twice the amount of hydrogen molecules produced than
oxygen molecules
Produced hydrogen gas has twice the volume of the produced
oxygen gas (assuming equal temp. and pressure for both
gases)
9. The Verdict
Hydrogen production via electrolysis can result in zero
greenhouse gas emissions
Offers opportunities for synergy with variable power generation
Allows for flexibility to shift production to best match resource
availability with system operational needs and market factors
Possibility of the elimination of curtailing excess energy from
renewable energy generation
Grid electricity is not environmentally friendly, energy intensive,
and is not an ideal source for electricity for electrolysis
Renewables integrating hydrogen production through
electrolysis is a possible option to overcome these limitations
10. Storage
Usually stored in a liquid or gas state
Liquid hydrogen kept at temperatures bordering on -253°C in
highly insulated tanks
As a compressed gas underground at pressures up to 150 bar
(15MPa)
Gaseous hydrogen storage is simplest and most extensively
employed for both large and small scale storage
11. Steel cylinders or special composite material tanks (Li, Mg, C
based) are capable of holding the gas at 700 bar
Typical storage: < 1.5% wt H2 , >98.5% wt of cylinder
Increase of % wt of H2: lighter cylinders at higher pressures
High cost of materials required for storage
High amount of energy is required to liquefy hydrogen
12. Hydrogen Compression
Hydrogen gas requires much larger tanks for its storage
compared to hydrocarbons due to its poor energy density by
volume
As a compressed gas usually at pressures up to 200 bar (3000 psi)
Increasing gas pressure improves the density by volume, making
for smaller, but heavier container tanks
Compressed hydrogen storage can exhibit very low permeation
Special composite material tanks are capable of holding the gas
at 700 bar
13. Compressed hydrogen is conventionally stored at near-ambient
temperatures
“Cold” (sub-ambient but >150K) and “Cryogenic” (150K and
below) storage being investigated to achieve higher H2 densities
at reduced temperatures
Cost of current compressed gas systems is dominated by
composite materials & processing with a significant impact from
balance of plant (BOP) components
14. Hydrogen compressors increase the pressure on the hydrogen
and can transport it through a pipe
Approx. 15% of the usable energy from the hydrogen is lost on
compression using today’s compression technologies
Also reduces the volume of hydrogen gas
Examples:
Electrochemical hydrogen compressor
Hydrogen supplied to the anode
Compressed hydrogen is collected at the cathode
Energy efficiency up to and even beyond 80%
Pressures up to 700 bar
Linear compressor
Piston moves along a linear track to compress the working fluid
Used under cryogenic conditions
15. Utilization
To provide electricity and heat through its use in fuel cells
Fuel cells generate electricity from an electrochemical reaction
where oxygen and hydrogen combine to form water
Electricity produced used in a variety of applications
Heat produced as a by-product used for heating and cooling
purposes
16. Why Hydrogen?
A clean energy carrier produced from any primary energy source
Pros of Hydrogen as an energy carrier:
Security of Energy Supply
Air Quality & Health Improvement
Greenhouse Gas Reduction
Ensures Economic Competitiveness
17. Hydrogen Safety
Knowledge gaps have existed for several decades regarding:
Conditions of ignition
Flame acceleration
Structural protection
Ventilation
Public perception and confidence in hydrogen relies on
credibility, transparency, and individual benefit
18. Exhibits wider limits of flammability, high detonation
sensitivity, and relative low ignition energy if mixed with air,
in comparison to conventional fuels
19. Codes & Standards regarding Hydrogen Safety:
Safety distances
Design of buildings & containers for housing hydrogen equipment
Earthing & lightning protection
Materials & components used in hydrogen systems
20. Risks & Challenges
Mixtures of hydrogen in are flammable over a wide range of
compositions
Energy required to ignite a hydrogen/air mix can be very low
Burns with a flame that is invisible in daylight
Small molecule that can leak very easily
If released and ignited, it burns with a rapidly moving flame
21. Conclusion
Sophisticated battery for energy
storage
High potential as a relatively clean
fuel of the future
Negative net energy i.e. it takes more
energy to produce it than it contains
Very low calorific value
Requires larger and heavier fuel
tanks
Extraction methods are extremely
energy intensive (e.g.. Electrolysis of
water)
22. Thank You
WindPower Nepal is looking for technical assistance to find out if
Hydrogen could be used as a Cooking Fuel in Nepal. For further
information, please write to us at
info@windpowernepal.com
Editor's Notes
Non-carcinogenic : Non cancer-causing
Mostly found in its molecular form combined with another chemical as a compound (eg. Water, methane)
Gasification : Reacting coal with oxygen + steam under high P & T to form synthesis gas (CO,H2)
Gas cleaned of impurities and the CO is reacted with steam to produce additional H2 +CO2
H2 separated and CO2 steam can be captured
Natural Gas Reforming: Methane from Natural gas used to produce H by steam-methane formation and partial oxidation
Steam Reforming: Achieved in a processing device called a reformer which reacts steam at high temps with a fossil fuel
Electrolyte : Produces an electrically conducting solution when dissolved in water
PEM operates at 70°-90°C
Alkaline operates at 100°-150°C
Reduction : Atoms have their oxidation state changed (i.e. involves the transfer of electrons between species)
Cation : Any positively charged atom or group of atoms
Oxidation : Gain of electrons
Today’s grid electricity if not the ideal source of electricity for electrolysis because most of the electricity is generated using technology that result in greenhouse gas emissions and are very energy intensive
*Li, Mg, C based composites used
Hydrogen gas has good energy density by weight, but poor energy density by volume when compared to hydrocarbons
Permeation : chance of penetration from foreign bodies/substances
BOP : All other components excluding the actual storage cylinder
Security of Energy Supply: Access to a broad range of primary energy sources such as fossil fuels, wind solar, etc
Enhances energy security through increased diversity
Air Quality & Health: Power generation fuelled by H2 are zero-emission at the point of use
Greenhouse Gas Reduction: H can be produced from carbon-free/carbon-neutral energy sources or fossil fuels with C02 capture + storage
H2 use could eventually eliminate greenhouse gas emissions
*Economic Competitiveness: Development & sales of energy systems are major components of wealth creation
Safety Distances : Separation is required between H2 equipment and hazardous sources (power lines, elec eqiupment, combustibles)
Buildings: Good ventilation is required to avoid explosive mixes forming if H2 is released
Design of buildings to prevent H2 accumulation
Materials & Components : Pipework, hoses, connectors, valves,etc
Standardization of nozzles for H2 dispensers
Sophisticated Battery: Low volumetric density so there may be other energy carriers better suited to sustainable energy systems with decreased conversion efficiencies (ethanol, methanol, alcohol all based on shorter carbon cycles)
Low calorific value: for example, it takes about 4 times the volume of H2 compared to petrol to travel the same distance
Electrolysis : Cleanest and most appropriate process for obtaining H2 from wind & solar, but also most energy intensive – 75% efficient
Gas Reformation : Simplest, cheapest and most efficient – 85%, but it is less polluting and resource intensive to simply burn natural gas