Thermochemical water splitting and oxy-hydrogen steam turbine

Traditional steam generators are heavy and bulky. Metal pipes have to work in high pressure and temperature environment.
Efficiency of the steam powerplant is limited by maximum temperature of the steam from steam generator.
This temperature usually is around 1000-1100F and in certain conditions can be up to 1500F:

High performance steam development. Final report, Phase No. 3: 1500{degree}F steam plant for industrial cogeneration prototype development tests
[digital.library.unt.edu]


Modern gas turbines using hydrogen as a fuel can work with steam temperature up to 1600C (2912F).
[www.mhps.com]

Alternative way to generate very hot energy dense steam flow is
oxygen-hydrogen combustion steam generator. Oxygen and hydrogen are generated by thermochemical water splitting. Exhaust steam is condensed and returned to water splitting processor. Cycle efficiency is over 60% which is higher than the best marine turbocharged diesel engine efgiciency.

[link.springer.com]


[www.sciencedirect.com]

[www.sciencedirect.com]


Water can be split either by heat of combustion or by solar

[www.ncbi.nlm.nih.gov]
[www.ncbi.nlm.nih.gov]

[www.mdpi.com]



Edited 1 time(s). Last edit at 04/09/2020 10:00AM by novice.

I'm curious as to the energy balance needed to decompose water into its constituent elements. According to my old chemistry class, the amount of energy required to do that would be equal to the energy released upon combustion. Given a steam plant efficiency of (maybe) 20%, this doesn't look viable.

Am I missing something?

Regards,

Ken

Hi Ken,

The attached link will explain the energy required. This uses the Gibbs Free Energy equation.

Electroysis Model

Note that the free energy part is the -T*Delta S. What this means is that the higher the temperature, the less energy needed to split the water. Hence my interpretation of the free energy.

My concept is to take the water from a separator drum/tube and super heat it and bring it to an electrolysis device. This would be part of the high flow IR burner concept I posted in another thread. Note that its important to keep the water under pressure w/out phase change to vapor and allow the electrolysis to occur as it is released, during the pressure drop. What would make this really cool is to go super critical with the water. This would be over the top of the bell curve in the attached T-S diagram.

If Novice would like to correct me...more than welcome.

Enjoy,
Rick

Hi Ken
As I understood all that matter by diagonal scanning... Here heat used not for direct making steam but for splitting water (not without some energy lost of course). After that this heat recovers to the cycle in the form of highly superheated steam produced by combustion of hydrogen in the oxygen with cooling by saturated or even “normally” superheated steam. Such steam otherwise would need super alloys (not existed) to produce and contain. Like in ICE temperature of working fluid much higher than could hold material of cylinder. So now You can have steam engine, where normal and “holdable” steam comes into the cylinder and get much higher superheat by combustion of hydrogen-oxygen mixture which comes into the cylinder simultaneously. Such steam engine could work on, say,1800 F steam which impossible by ordinary means without super materials. This steam can have high expansion ratio without going through saturation line. You can also try to prolong combustion along expansion process not going too high at once, just keep temperature out of normal dropping, for lubricating issues. Thermodynamics of such Internal Combustion STEAM engine could be rather high... I understood that this way...
Don’t think all that machinery would fit in the vehicle…
Regards,
Serge



Edited 1 time(s). Last edit at 04/14/2020 12:15PM by russt.

Water splitting process efficiency is 40-50%, lower than water electrolysis 70-80%. But because electric energy is usually produced with efficiency 20-40%, thermochemical process is 2-3 times more efficient.
Main application of this technology is solar steam power stations. Solar energy powered metal oxide catalytic generator splits water into oxygen and hydrogen.
These gases can be easily stored in pressure vessels in large quantities. Direct combustion of oxy-hydrogen mix generates very high temperature steam and overall efficiency goes up.

Metal Oxides Applied to Thermochemical Water-Splitting for Hydrogen Production Using Concentrated Solar Energy

[www.mdpi.com]

World’s Largest Solar Reactor Will Split H2O into Hydrogen

[www.solarpaces.org]


Study of the Hydrogen-Steam Turbine Composite Cycle

"It is proposed a new type of the thermodynamic cycle in this article. The cycle is mainly composed by Hydrogen Generator (HG), Hydrogen Turbine (HT), Hydrogen-Oxygen Combustor (HOC) and Steam Turbine (ST). The pure hydrogen is generated in HG at high pressure and is heated up. The hydrogen with high pressure and high temperature develops power by flowing through HT. The hydrogen passed through HT is burned with pure oxygen in HOC, and the generated steam provides power by expansion in ST sequentially. Different from the conventional Combined Cycle (CC), this thermodynamic cycle is series-wound by hydrogen turbine and steam turbine. Based on these features this cycle is called as the Hydrogen-Steam Turbine Composite Cycle (HSTCC) in this article. It is indicated that HSTCC has a higher efficiency. It should be a competitive power generating system using the sophisticated turbine technique for hydrogen energy in future."

[www.sciencedirect.com]

Hydrogen Oxygen Steam Generator Integrating with Renewable Energy Resource for Electricity Generation

[www.sciencedirect.com]

All files from this thread

File Name	File Size		Posted by	Date
materials-05.png	332.3 KB	open | download	novice	04/09/2020	Read message
Oxy hydrogen steam engine.png	208.7 KB	open | download	novice	04/09/2020	Read message
Oxy hydrogen steam turbine.png	317 KB	open | download	novice	04/09/2020	Read message
Solar hydrogen.jpg	55.6 KB	open | download	novice	04/09/2020	Read message
Solar hydrogen2.jpg	89.4 KB	open | download	novice	04/09/2020	Read message
Solar1.jpg	44.6 KB	open | download	novice	04/09/2020	Read message
Thermo hydrogen.png	191.4 KB	open | download	novice	04/09/2020	Read message
TS Diagram.gif	53.1 KB	open | download	Rick.H	04/14/2020	Read message