Autonomous portable refrigeration unit
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Solution Overview
Problem
Existing refrigeration systems are inadequate for maintaining temperature-sensitive materials like blood in remote or off-grid locations due to reliance on AC power and limited temperature control in extreme conditions.
Innovation Solution
A portable refrigeration unit with a phase-change material (PCM) and vapor compression system, controlled by an electronic control system, maintains a predetermined temperature without external power, using a double-walled design and PCM to absorb heat, and a battery-operated compressor for extended operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a conventional refrigeration system using AC power is used, then temperature control is reliable, but it cannot operate in off-grid locations
Solution Approach 1:
The system pre-charges a battery with excess power when available, and pre-cools the storage compartment to a target temperature before entering standby mode. This preliminary action ensures the refrigeration system can maintain temperature for extended periods without power, resolving the contradiction between off-grid operability and temperature control reliability.
Solution Approach 2:
The system uses phase-change material (PCM) that transitions between solid and liquid states to store and release thermal energy. When the battery powers the compressor, it cools the PCM to freeze it; when power is unavailable, the PCM melts, absorbing heat and maintaining the storage temperature. This phase transition mechanism enables reliable temperature control in off-grid locations.
2Device complexity
If passive cooling with ice is used, then the system is simple and portable, but temperature control is limited and duration is short
Solution Approach 1:
The system uses a battery-operated compressor that automatically cycles based on temperature sensor feedback. When the storage compartment temperature approaches the target, the compressor shuts off and the system relies on the thermal mass of the PCM and insulation to maintain temperature. This self-regulating mechanism extends cooling duration while keeping the system portable and relatively simple.
Solution Approach 2:
The system combines multiple materials and mechanisms: vapor compression refrigeration system, phase-change material (PCM), and thermal insulation. This composite approach integrates active cooling with passive thermal management, extending the duration of cooling action while maintaining portability and reasonable complexity.
3Temperature
If active refrigeration with compressor is used, then temperature control is precise, but power consumption increases
Solution Approach 1:
The refrigeration system operates in periodic cycles rather than continuously. The compressor runs intermittently to maintain the PCM in a frozen state, then shuts off to allow the PCM to melt and absorb heat. This periodic operation maintains precise temperature control while significantly reducing average power consumption compared to continuous operation.
Solution Approach 2:
The system leverages the phase transition of PCM to reduce compressor runtime. By freezing the PCM during active cooling and allowing it to melt during standby, the system uses the latent heat of fusion to maintain temperature without continuous compressor operation, thereby reducing power consumption while maintaining temperature precision.
4Use of energy by moving object
If insulation is increased to reduce power consumption, then energy efficiency improves, but device size and weight increase
Solution Approach 1:
The system uses phase-change material (PCM) with high latent heat capacity to store thermal energy. This allows the insulation to be thinner because the PCM compensates for heat ingress during the melt phase. The PCM's ability to absorb large amounts of heat during phase transition reduces the reliance on thick insulation, thereby reducing device weight while maintaining energy efficiency.
Solution Approach 2:
The system combines moderate insulation with high-performance phase-change material and optimized thermal pathways. This composite thermal management approach achieves high energy efficiency without requiring excessive insulation thickness, balancing energy efficiency with acceptable device weight and size.
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 provides precise temperature control and extended operation in extreme conditions, ensuring the integrity of temperature-sensitive materials like blood in off-grid environments.
Implementation Method 1
A portable refrigeration unit with a phase-change material (PCM) and vapor compression system
Implementation Method 2
using a double-walled design and PCM to absorb heat
Implementation Method 3
An evaporator may include a coil... The coil may be at least partially disposed in the volume between the inner bucket and the outer bucket
Implementation Method 4
A refrigeration system may be disposed in the case and may have a compressor
Implementation Method 5
A condenser may have an inlet in fluid communication with an outlet of the compressor
Data Source
AI summary
Systems, methods, and devices may include a cooled storage system with a case having an outer bucket with a first bottom wall and a first sidewall. The outer bucket may include a flange protruding from the first sidewall. An inner bucket may be disposed at least partially within the outer bucket and may include a second bottom wall and a second sidewall defining a storage compartment in the case. A coil may be at least partially disposed in the volume between the inner bucket and the outer bucket with a phase-change material disposed about the coil. An electronic control system may actively and passively cool the storage compartment resulting in extremely efficient and precise temperature control.