Goal
Provide an inexpensive refrigeration solution by converting a standard window air-conditioner into a walk-in cooler capable of reaching near-freezing temperatures.
Problem
High cost and complexity of conventional walk-in cooler compressors and refrigeration systems for farmers, small businesses, and developing-world users.
Concept Summary
CoolBot is a micro-controller based retrofit kit that interfaces with a conventional air-conditioner, overrides its low-temperature shut-off, and uses frost detection and sensor heating to safely operate the compressor at temperatures down to the low 30 deg F range, enabling low-cost refrigeration without major modifications.
Principles
- Feedback control
- Frost detection
- Temperature sensor heating
- Micro-controller regulation
- Relay-based temperature setpoint override
Scientific Domains
Materials
- Copper wiring
- Nichrome heating element
- Thermistor (metal-oxide frost sensor
- Silicon micro-controller board
- Plastic enclosure
Mechanisms of Action
- Heater applied to the A/C unit's temperature sensor to keep it reading a higher temperature, preventing automatic shutdown.
- Frost sensor detects ice on the condenser fins and disables the heater to avoid frost buildup.
- Micro-controller monitors temperature, frost sensor, and desired setpoint, adjusting the heater or relay accordingly.
- Relay or direct wiring replaces the factory thermostat control to allow lower temperature operation.
Energy Sources
Applications
- Farm walk-in coolers
- Refrigerated transport (RVs, trucks)
- Small commercial refrigeration (restaurants, florists)
- Developing-world agricultural storage
Claimed Performance
Enables a standard window air-conditioner to maintain temperatures in the low 30 deg F range, providing up to 100 % of the unit's rated BTU cooling capacity while shutting off the compressor when frost is detected to save electricity.
Experimental Evidence
The inventor reports having sold about 80 units at $250 each, with users achieving 30 deg F in insulated walk-in cooler spaces; no formal test data are provided.
Replication Status
Commercial units have been sold; no independent replication or peer-reviewed testing is mentioned.
Limitations
- Requires a compatible window-type air-conditioner
- Performance depends on proper sizing of the A/C unit for the insulated volume
- Frost sensor or heater failure could cause premature shutdown or equipment damage
- Not suitable for large-scale industrial refrigeration
Red Flags
- Lack of independent, peer-reviewed performance data
- Claims based mainly on anecdotal user reports
- Possible risk of damaging the original air-conditioner if not installed correctly
