Reversible Power-to-Gas Layout for Low-Loss H2 and CH4 Storage
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Solution Overview
Problem
Current 'power-to-gas' technologies face inefficiencies in hydrogen (H2) electrolysis and methanation processes due to heat requirements for water evaporation and oxygen separation, leading to low energy conversion efficiencies and increased investment costs, which hinder the implementation of sustainable energy storage and industrial raw material production.
Innovation Solution
Implementing a reversible overall concept that provides H2O in a gaseous state for electrolysis, utilizing waste heat or external heat sources via heat pumps to minimize evaporation heat requirements, and optimizing thermal integration of electrolysis and methanation processes to enhance energy efficiency and reduce exergy losses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If liquid H2O is supplied to the electrolyzer and electrically heated for evaporation, then the electrolysis process can proceed, but the energy efficiency decreases due to additional electrical power consumption for evaporation
Solution Approach 1:
The patent creates a thermal copy of the evaporation process by using a separate thermal electrolysis cell that replicates the water evaporation function without requiring additional electrical power for heating. The thermal cell uses waste heat or external heat sources to evaporate water, copying the thermal transformation needed in conventional electrolysis but decoupling it from electrical energy consumption.
Solution Approach 2:
The patent introduces a thermal electrolysis cell as an intermediary component between the electrical electrolyzer and the water supply system. This intermediary handles the water evaporation function thermally, allowing the main electrolyzer to focus on electrical energy conversion to hydrogen without the burden of thermal management and additional power consumption.
2Productivity
If thermal methanation is used to produce CH4 from H2 and CO2, then synthetic fuel can be produced, but O2 separation and condensation of produced H2O require additional energy input
Solution Approach 1:
The patent merges the thermal methanation reactor with the thermal electrolysis cell into a single integrated unit. This combination allows the exothermic methanation reaction to provide the necessary heat for water evaporation, while the endothermic electrolysis reaction absorbs excess heat. The unified system eliminates separate O2 separation and H2O condensation steps by directly producing CH4 and H2O in a combined reaction zone, reducing energy losses.
Solution Approach 2:
The patent converts the harmful waste heat from methanation into a beneficial resource by using it to drive the electrolysis reactions. The exothermic methanation reaction, which would normally release unwanted heat, now provides the necessary thermal energy for water evaporation and sustains the electrolysis process, turning a potential energy loss into a useful input.
3Speed
If high temperature electrolysis is used, then reaction rate increases, but more evaporation heat is required relative to electrical work supplied
Solution Approach 1:
The patent implements a dynamic thermal management system where the operating temperature of the electrolysis cell can be adjusted based on the availability of external heat sources and the desired production rate. The system can operate at higher temperatures when waste heat is abundant to maximize reaction rates, and at lower temperatures when thermal energy is limited, optimizing the balance between productivity and energy efficiency.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach significantly improves the energy efficiency of 'power-to-gas' technologies, reducing investment costs and ensuring a stable power supply by converting fluctuating renewable electricity into chemical potential, while promoting sustainable energy storage and CO2 recycling.
Implementation Method 1
electrolysis cell (1) in which water vapor is electrolyzed
Implementation Method 2
methanation of H2 with CO or CO2, which is essentially based on the Sabatier reaction
Implementation Method 3
utilizing waste heat or external heat sources via heat pumps to minimize evaporation heat requirements
Implementation Method 4
heat requirement for the evaporation of the supplied liquid H2O
Data Source
AI summary
A modular reactor configuration for the production of hydrogen (H2) by means of electrolysis in its single-stage design and of methane (CH4) in its two-stage design with optional gas storage and gas utilization in fuel cells, wherein the single-stage design, consisting of the electrolyzer, the fuel cell, the gas storage tanks for separate storage of H2 and oxygen (O2), the associated lines, the condenser, the H2O container, the heat storage tanks and the evaporator, is based on the principles of a reversible product cycle for H2 according to FIG. 1 and can serve both as electricity storage and for H2 production as fuel gas, and whose two-stage design, exemplified according to FIG. 5 with the additional components the methanation reactor, the lines and, the heat exchangers and as well as the CH4 discharge in the H2O condenser, based on extended reversible reference processes, which describe the possible methanation reactions in this second reactor stage with the reaction equations, which can also run in parallel, and are thermodynamically equivalent to the reverse reaction of the oxidation of CH4 and thus indicate the best possible structures for further technical implementation.