Reciprocating Compressor Heat Exchanger Thermal Storage
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Solution Overview
Problem
Conventional CNG stations are energy inefficient due to compressor design limitations that require sacrificing gas pressure, leading to limited flow capacity and inability to control flow rates, as they are typically custom-designed for specific site conditions and operate at fixed speeds.
Innovation Solution
A reciprocating compressor system with a high-pressure storage vessel letdown mechanism that de-pressurizes gas from a high-pressure storage vessel, increasing inlet gas pressure and allowing adjustable flow capacity by using a heat exchanger with thermal storage media to condition the gas temperature for improved dispensing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If conventional compressors operate at fixed speed with inlet gas from local utility, then the system is simple to operate, but the flow capacity is limited and cannot be adjusted to meet varying demand
Solution Approach 1:
The patent implements a nested system where a high-pressure storage vessel (3600-4500 psig) contains a lower-pressure storage vessel (200-3600 psig) within it. This nested configuration allows the system to store multiple pressure levels in a compact arrangement, enabling flow capacity adjustment without requiring separate external storage systems for each pressure level.
Solution Approach 2:
The system pre-pressurizes storage vessels to high pressure (3600-4500 psig) before peak demand periods. During non-peak hours, the compressor charges the nested storage system, preparing it in advance for rapid gas delivery during peak hours when flow capacity must be increased without running the compressor at full speed continuously.
2Productivity
If the compressor is designed for high flow capacity, then it can meet peak demand, but it consumes excessive power during non-peak hours when demand is low
Solution Approach 1:
The system dynamically adjusts the compressor speed based on real-time demand conditions. During peak hours, the compressor operates at high speed to meet maximum flow capacity requirements. During non-peak hours, it automatically reduces to low-speed operation, matching the lower demand and minimizing power consumption while maintaining readiness to ramp up when needed.
Solution Approach 2:
The system employs periodic charging cycles where the compressor alternates between high-speed charging of the nested storage vessels during low-demand periods and maintenance operation during peak periods. This periodic action allows the compressor to build up stored energy (pressurized gas) when power consumption can be lower, then rely on stored pressure during peak demand without continuous high-power operation.
3Reliability
If the inlet gas pressure is reduced by an inlet regulator to meet compressor design specifications, then the compressor can operate within design parameters, but gas pressure is sacrificed and energy efficiency is reduced
Solution Approach 1:
The nested storage vessels serve as an intermediary between the high-pressure gas source and the compressor inlet. Instead of using an inlet regulator to reduce pressure, the system uses the pre-pressurized storage vessels (containing gas at 200-3600 psig) to provide appropriately pressurized inlet gas to the compressor, eliminating the need for pressure-reducing regulation and the associated energy losses.
Solution Approach 2:
The system changes the pressure parameter of the inlet gas by utilizing gas already stored at various pressure levels (200-3600 psig) in the nested vessels. This allows the compressor to receive inlet gas at optimal pressure levels without undergoing pressure reduction through regulation, thereby maintaining energy efficiency while ensuring reliable operation within design parameters.
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
The system enhances energy utilization by increasing flow capacity during peak hours and reducing power consumption during non-peak hours, enabling active management of gas supply and demand while maintaining temperature control for efficient CNG refueling.
Implementation Method 1
Some embodiments of the invention feature a heat exchanging mechanism (e.g., a heat exchanger) having a thermal storage media (e.g., water or glycol solution). During use of the heat exchanger, heat from the thermal storage media is added to the gas, thereby cooling the thermal storage media to a low temperature state.
Implementation Method 2
When CNG from a high-pressure storage vessel (or from a compressor high-pressure discharge line) is de-pressurized, the temperature of the de-pressurized gas is significantly reduced due to the Joule-Thomson effect of natural gas.
Data Source
AI summary
A reciprocating compressor comprises a gas inlet section including an inlet gas meter for metering inlet gas from a high pressure storage vessel, a compressor, a valve control panel and storage, a pressure let down that depressurizes the high pressure gas from the high pressure storage vessel to the inlet of the compressor section, a heat exchanger having thermal storage media, and a dispenser.