Stepped Isotherm Adsorbents for High-Density Methane Storage
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Solution Overview
Problem
Natural gas storage in vehicles is hindered by low volumetric energy density at ambient temperature and pressure, requiring large storage tanks and facing challenges in designing practical systems with high methane storage capacity, sufficient thermal management, and low cost.
Innovation Solution
Development of adsorbents with stepped isotherms, specifically flexible metal-organic frameworks that undergo structural phase transitions, allowing for high-pressure gas storage with reduced heat release and cooling during adsorption and desorption, and tunable pressure and energy through chemical or mechanical means.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If natural gas is stored at ambient temperature and pressure, then the system is simple and safe, but the volumetric energy density is low requiring large storage tanks
Solution Approach 1:
The patent employs porous adsorbent materials with stepped isotherms that can store methane at high densities through adsorption mechanisms. The porous structure provides large surface area and volume for gas storage, achieving high volumetric energy density without requiring proportionally large tank volumes.
Solution Approach 2:
The patent utilizes phase transitions in the adsorbent material, specifically the transition between low-pressure and high-pressure phases, to enable high-capacity methane storage. The phase transition allows the material to take up large amounts of methane at relatively low pressures, then release it when needed.
2Quantity of substance
If high capacity adsorbents are used to store methane, then the storage capacity increases, but heat release during adsorption becomes significant requiring thermal management
Solution Approach 1:
The stepped isotherm with phase transition creates a natural thermal management mechanism. The phase transition occurs at a specific pressure threshold, allowing the system to store large amounts of methane while the transition process itself manages the heat release by occurring in a controlled manner at defined conditions.
Solution Approach 2:
The adsorption process utilizes periodic pressure cycling with distinct phases. During the charging phase, methane is adsorbed at high pressure; during discharge, pressure is reduced and methane is released. This periodic action allows thermal management by separating the high heat-release adsorption event from the lower heat-absorption desorption event.
3Quantity of substance
If the adsorbent releases gas at low pressure, then the delivery pressure is low and safe, but the amount of gas remaining adsorbed reduces the usable capacity
Solution Approach 1:
The stepped isotherm creates a sharp transition point in the desorption process. When pressure drops below the step threshold, a large amount of methane is rapidly released. This allows the system to maintain high usable capacity because the phase transition ensures that even at low minimum desorption pressures, the amount of methane remaining adsorbed is minimal.
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
Enhances methane storage capacity, reduces thermal management requirements, and maintains volumetric usable capacity even at minimum desorption pressures, offering a more efficient and compact gas storage solution.
Implementation Method 1
the flexible metal-organic frameworks are shown to undergo a structural phase transition in response to specific CH4 pressures
Implementation Method 2
Adsorbed natural gas (ANG) systems have the potential to eliminate these issues by storing high densities of methane within a porous material at ambient temperature and reduced pressures
Data Source
AI summary
The disclosure provides for adsorbents with stepped isotherms for gas storage applications.