Laboratories use cold plates to maintain specimen samples for dissection at desired cooled temperatures. A conventional cold plate utilizes a closed refrigeration circuit including an evaporator coil positioned within the cold plate, a compressor, and a condenser. The compressor compresses evaporated refrigerant drawn from the evaporator and passes the compressed refrigerant to the condenser, which removes heat from the compressed refrigerant. Compressed gaseous refrigerant, having a high temperature, is cooled in the condenser to become liquid. The cooled liquid refrigerant flows into the evaporator to cool the cold plate. At the same time, heat transfer from the air surrounding the cold plate evaporates the refrigerant within the evaporator, which is drawn back into the compressor.
There are two common techniques to control the temperature of the cold plate. These techniques include (1) turning the compressor on/off to control the flow of refrigerant to the cold plate and (2) turning an electric heater coupled to the cold plate on/off to warm the cold plate. 
In systems that turn the compressor on/off to control temperature, the compressor cannot be turned on until the pressure on both side of the compressor equalizes. Turning on the compressor too soon requires a lot of power to overcome pressure differences, which may cause the compressor to overheat and/or malfunction. In addition, longer times between turning the compressor on and off may cause temperature overshoots and undershoots (e.g., +/−5° C.). In techniques using an electric heater, additional component are needed to heat the cold plate and additional energy is added to warm the cold plate, thereby increasing the cost and reducing the efficiency of these systems.
During use, water vapor in the air condenses on the cold plate. The condensed water on the cold plate becomes ice, which interferes with the use of the cold plate. Typically, the cold plate is periodically turned off, for example, at the end of each day, to allow the ice to melt. Often, laboratory procedures require disposal of liquid due to the defrost process prior to leaving the laboratory. Allowing the cold plate to defrost simply by turning it off may take fifteen minutes or more. Thus, the operator is inconvenienced by having to wait for the cold plate to defrost in order to dispose of the resultant water.
Accordingly, improved methods and apparatus are needed to control the temperature of a cold plate that are not subject to the above limitations. The present invention fulfills this need among others.