Vehicle AC Cold Storage Unit Using Phase Change Materials
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Solution Overview
Problem
Public transport vehicles face challenges in maintaining thermal comfort for passengers while minimizing energy consumption due to frequent starts and stops and short trip times, making it difficult to achieve a high coefficient of performance (COP) in air conditioning systems and manage energy loads effectively.
Innovation Solution
A vehicle air conditioning system that employs a refrigeration circuit with a compressor, mixer, absorber, separator, condenser, and evaporator, integrated with a cold storage unit using phase change materials, and a regenerative braking energy recovery system to alternate between high-power and low-power refrigeration cycles, optimizing energy usage by storing excess cold during braking phases and releasing it during traction and coasting phases.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If the air conditioning system operates continuously at high power to maintain thermal comfort during frequent starts and stops, then thermal comfort for passengers is improved, but energy consumption increases
Solution Approach 1:
The system pre-cools the passenger compartment during periods when thermal comfort requirements are lower (e.g., when doors are closed and occupancy is stable), storing cold energy in the thermal mass of the compartment structure, seats, and air. This preliminary cooling action reduces the need for high-power operation during subsequent high-demand periods such as frequent door openings or rapid temperature changes, thereby improving thermal comfort while reducing overall energy consumption.
Solution Approach 2:
The control system dynamically adjusts operating parameters including compressor speed, fan rates, and refrigerant flow based on real-time conditions such as outdoor temperature, solar load, occupancy, and door status. By changing operational parameters rather than maintaining constant high-power operation, the system maintains adequate thermal comfort during critical periods while significantly reducing energy consumption during transitional or low-demand periods.
2Use of energy by moving object
If the air conditioning system operates at variable power levels to match thermal demand, then energy consumption is reduced, but thermal comfort control becomes more difficult
Solution Approach 1:
The system incorporates multiple sensors that continuously monitor temperature, humidity, occupancy, door status, and solar radiation. This feedback information is fed to the controller which automatically adjusts compressor speed, fan operation, and refrigerant distribution to maintain thermal comfort. The closed-loop feedback control eliminates the complexity of manual variable power operation while optimizing energy consumption based on actual thermal demands.
Solution Approach 2:
The air conditioning system integrates multiple functions including cooling, dehumidification, air circulation, and thermal energy storage within a unified control architecture. The controller manages various components (compressor, condensers, evaporators, fans, valves) as an integrated system, allowing variable power operation across different operating modes while maintaining simple user interaction and consistent thermal comfort through coordinated control of all components.
3Loss of energy
If excess cold is stored during braking phases and released during traction phases, then the coefficient of performance (COP) is improved, but system complexity increases
Solution Approach 1:
The system combines the air conditioning refrigeration cycle with the vehicle's existing thermal management infrastructure, including the radiator and coolant system. The AC condenser is thermally coupled with the vehicle coolant loop, allowing waste heat from the engine to assist in condensing the refrigerant during braking and coasting phases. This merging of functions improves COP by utilizing otherwise wasted thermal energy while avoiding the need for separate dedicated components.
Solution Approach 2:
The system utilizes the vehicle's own operational characteristics (braking, coasting, engine heat) to provide cooling services. During braking and coasting phases when the engine is off or running at low power, the system automatically switches to alternative cooling modes using stored cold energy and passive heat dissipation. The engine coolant system automatically serves dual purposes of engine thermal management and AC condensation, requiring no additional active components or complex control mechanisms.
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 reduces energy consumption, enhances thermal comfort for passengers, and improves the coefficient of performance (COP) of the air conditioning system by smoothing energy demand curves and utilizing regenerative braking energy efficiently.
Implementation Method 1
cold storage unit using phase change materials
Implementation Method 2
cold storage unit using phase change materials
Implementation Method 3
evaporating the refrigerant in an evaporator with transferring thermal energy between the refrigerant in the evaporator and air flowing through the evaporator
Implementation Method 4
condensing the refrigerant in a condenser
Data Source
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AI summary
The invention is a method of cooling air in a vehicle using a cold storage unit (60) in the refrigeration cycle. The air conditioning system and its cold storage unit is adapted to work according to the operation of the vehicle. The method produces cold in excess to be stored in the cold storage unit (60), using the phase change heating of materials, in at least an operation mode of the system. This cold in excess allows to cool the supply air to the comfort volume, in at least one other operation mode. These charge/discharge of the cold storage unit (60) and the refrigeration cycle associated could correspond to a minimization of consumption criteria of the vehicle, for example, a regenerative braking period and a traction/coasting period, or alternatively, according to the optimization of the variable condenser capacity of the refrigeration cycle.