Sustainable Hydrogen Flashcards
What was the Hindenberg accident
- It was a very famous accident involving an airship, which spontaneously combusted and burned as it was coming into doc in the US
- This incident scared people from using hydrogen and the thought of containing pressurized hydrogen worried people
How does the enthalpy of vapourization different between hydrogen and methane
The enthalpy of vapourization is very small in hydrogen
Hence if hydrogen was split, it would evaporate very quickly
What is the energy availability of hydrogen as a fuel?
Hydrogen has a great energy density (greater than any liquified fuels we use now)
And no carbon is released upon burning either
Why could hydrogen be described as a clean, safe and versatile energy carrier?
- Can be produced without a C footprint (through electrolysis + CCS)
- Can be transported over long distances (allowing the distribution between countries)
- Has a high energy density (making it suitable for long-term storage)
- Produces clean power/heat
- Required as a clean feedstock for recycling capture CO₂
How can hydrogen be produced through steam reforming?
- A reactions of CH₄ (or other organics) with steam at high temp
(most common - also known as grey Hydrogen)
How can hydrogen be produced from electrolysis?
Through splitting water into hydrogen and oxygen
(can be done using either renewable/non-renewable energy)
How can hydrogen be obtained from biomass conversion?
- via either thermochemical or biochemical conversion to intermediate products
- which can then be seperated or reformed to hydrogen
(or fermentations techniques that produce hydrogen directly) - However efficiency of hydrogen recovery is quite low
How can hydrogen be obtained from solar conversion?
- By either thermolysis, using solar-generated heat for high temperature chemical cycle hydrogen production
- Or photolysis, in which solar photons are used in biological or electrochemical systems to produce hydrogen directly
What are the drawbacks of steam reforming?
- high temp process
- uses natural gas or other hydrocarbons
- Highly endothermic process - takes in a lot of energy
- The CO byproduct is burnt off to further driven the furnace for the steam reforming
- known as grey hydrogen
How can steam reforming be altered to form blue hydrogen?
- The fuel which drives the reactor is combusted which would give rise to the generation of CO₂ which is then emitted to the atmosphere
- BUT if we use CCS (permanent storage) parallel to the steam reforming process, we produce blue hydrogen
What is a drawback of blue hydrogen?
The carbon capture and storage itself costs a lot of energy and material
What is a way of producing green hydrogen?
- Through electrolysis of water (splitting water through passing a current through the sample) - called a proton exchange membrane electrolyser
- Using energy from renewable processes
(possibility of a low impact process where we could yield vast quantities of hydrogen due to water availability)
What is power to X?
- Using the CO₂ from CCS, in a direct hydrogenation reaction to make 1C fuels/fine chemicals which can be used to supplant the peterochemical feedstock
- This process can have different degrees of sustainability depending on which colour hydrogen is used
What is Pink Hydrogen?
- Hydrogen which has come from the electrolysis of water
- The energy coming from nuclear power
What is Yellow Hydrogen?
- Hydrogen coming from the electrolysis of water
- The energy coming from solar power
How would the Principle of Green Hydrogen best be applied to a country like the UK?
- The renewable energy source which would be most applicable to the UK would be solar
- This power would transmitted through the national grid to a place where the water is electrolysed to hydrogen gas
- The hydrogen is the stored, compressed and transported ( as a liquidfied gas or complex)
Why is Yellow hydrogen not really a feasible process?
- The idea of yellow is to use photovolatics to generate currents that can then be directly used to electrolyse water
- However the energy density of photovoltaics is not always great
- The photo shows the largest solar farm in the US, which only has a capacity of 50MW
- Quite a tall ask from solar energy
Describe the use of Solar Thermal to generate electricity
- The use of mirrors/helistats to concentrate solar energy onto a boiler
- That boiler would heat a fluid salt (salt with a high heat capacity and hence store a lot of heat within it)
- The molten salt can then be used to vaporise water and generate electricity under traditional turbine type conditions
(these solar farms do exist in part of the world which receive a lot of direct sunlight)
What is the efficiency of, Steam Reforming, Biogasifers, Electrolysis and Photolysis to deliever Hydrogen?
In what ways can we use Hydrogen to reduce the dependence on Peterochemicals?
- Can use hydrogen in the existing gas grid which we use to heat + cook
- Use hydrogen for fuel transportation (internal combustion/fuel cells)
- As a chemical feedstock
The Haber process is an example of a industrial process, green hydrogen can be applied to
Explain the benefit of this
- Through sustainably producing hydrogen, we can produce green ammonia and push down the impact of the Haber process
- Ammonia can also be used as a fuel like hydrogen and add to the energy balance - overall producing lower impact fuels
How has Iceland used geo-energy to produce more sustainable fuels?
- Renewable methanol can be produced from CO₂ from CCS and green hydrogen (fueled by geo-energy)
- The geo-energy is used to vaporised wateer which runs a turbine to generate electricity which will drive the electrolysis of water
How can CCS and sustainable hydrogen close the loop on carbon?
- CCS and sustainable hydrogen can be used to produce simple 1C units
- These can then be extended and adapted using the Fischer Tropsch process, to produce more complicated peterochemcials
- These in which can be used for fuels, argochemicals, fine chemicals etc
- Reducing the dependency of peterochemical feedstock
What is the basic idea of the Fischer-Trosch process?
Hydrogen reacts with CO, over an elaborate catalyst to make a whole range of hydrocarbon products which can then be cracked and reformed to produce the peterochemicals we know and use today
What two big process of Fischer Tropsch which came about in the 1920 due to peterochemicals shortage due to war
- Coal-to-liquid and Gas-to-liquid
- End products being Synthesis gas: CO + H₂
- the coal process uses higher temperautres
What would be a much better way to produce syn-gases rather than using gas and coal?
- If H₂ was cheap, the Fischer Tropsch chemistry could be used in conjunction with the Water-Gas-Shift reaction to activate CO₂
