Energy efficiency is key to the total cost of ownership of enclosure climate control solutions, and electricity consumption is a major element of operating costs. Hybrid technology, developed and patented by Rittal, combines conventional compression cooling, similar to what has been used in traditional air conditioners, with a heat pipe. The heat pipe uses evaporation of a working fluid in an evacuated tube.

Eric Corzine, Climate Control Product Manager, Rittal
“The system uses two circuits, which is why we call it a hybrid system,” said Eric Corzine, Rittal’s Climate Control Product Manager. “We have the traditional compressor-based cooling system, like you’d see in air conditioners prior to this, but then we’ve also included a heat pipe.”

The vapor moves along one side of the heat pipe while the condense liquid moves along the other without the need for active components. The system relies solely on physical principles, including gravity and capillary action. No compressors or pumps are required; the only power-consuming components are the fans. Heat pipes are ideal when the temperature inside the enclosure differs greatly from that of the ambient air. The system’s compression cooling system is highly energy efficient. Frequency converters precisely adjust the speed of the DC motors for the fans and compressors to achieve the exact cooling output required. As a result, the system consumes considerably less electricity than conventional technologies.

Best of Both Worlds

With the hybrid system, once the interior temperature of the enclosure reaches the predefined threshold, the frequency inverter automatically decreases the compressor’s speed, lowering cooling output. The controller continuously monitors the temperature, and adjusts cooling output accordingly. This method saves energy, and increases compressor service life as it greatly reduces the number of times the unit is switched on and off. “You want a stable, constant temperature, which prolongs the life of the components not only within the enclosure, but also the life of the air conditioner,” said Corzine.

“With active and passive systems, you get a lot more control over temperature,” explained Corzine. “In traditional systems, you have a set point. If it was at 95 °F, as the enclosure heats up above that, the air conditioner would kick on 100%, it would cool the enclosure down below that 95°, and then it would shut off. It would then heat back up above that and you’d get a sine wave effect.”

The hybrid system provides the best of both worlds. “It’s not your traditional AC motor or compressor where it’s on or off,” added Corzine. “The board knows that the compressor doesn’t have to be run at 100%. It uses the heat pipe 60% or 80%, and only needs the compressor-based system to be 20 to 40%. It just uses what it needs on the compressor-based system.”

Using inverter technology, the hybrid systems can be used universally. “With the global economy, you may not know where a finished article is going,” said Corzine. “Previously, you had to know because you needed to understand the electrical requirements. If it was going to a country requiring 115V, you needed one item, and if it was going somewhere that needed 230V, you needed another item.” Only one item is required regardless of which electrical supply is being used. “This makes it easier for the OEMs and distributors,” explained Corzine. “They only have to stock one item.”

Other advantages in terms of product engineering include standard cut-out sizes in enclosure doors and side panels, and simplified installation of fans, cables, and control panels.

Rollout at Hannover

At last year’s Hannover Fair industrial trade show in Germany, Rittal announced Blue e+ enclosure cooling units incorporating the hybrid technology. Corzine explained that while Rittal unveiled the systems last year at Hannover, the company did not enter full manufacturing production until last August and September. The U.S. launch occurred in January of this year. A full rollout of the commercial units will take place at Hannover Fair this year, which takes place April 25-29.

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