CAREL offers solution to improve the energy efficiency of Data Centers

Data Centers normally have huge energy consumption demands. Extensive research is being devoted to reducing the energy footprint of Data Centers worldwide.

As a result of the research done in integrating electronic controls and humidification technologies for this application, CAREL has developed a new, high efficient solution for part of the overall energy demand.

This technology is the new evaporative cooling system called optiMist.


This new product works both as an evaporative cooler and a humidifier. That means a single product inside the air conditioning unit serves two functions. The evaporative cooling produced by the optiMist reduces the air conditioning cooling load and refrigeration compressor run time.

The optiMist is installed in the AHU with humidification distribution in the humidification compartment AND in the exhaust air flow (upstream of the heat exchanger) of the Data Center air conditioning units.

It receives two separate signals, one relating to humidification (winter) and one for evaporative cooling (summer), producing a flow of atomized water inside the AHU during both seasons.

The optiMist summer/winter feature includes a water inlet circuit, a volumetric pump and two solenoid valves to distribute atomized water at 232 psi (16 bars). Inside the CAREL electrical panel is the power circuit, a programmable electronic controller and an inverter.

The optiMist receives the control signal from a remote control device or directly from temperature and humidity probes. The electronic controller calculates the flow-rate of atomized water required to meet the evaporative cooling or humidity demand and signals the required pump speed to the inverter. This avoids waste by ensuring linear modulation of atomized water producing precise temperature and relative humidity control.

Evaporative cooling occurs due to the spontaneous evaporation of atomized water droplets that are introduced upstream of the cooling coil. This change in phase from liquid to vapor extracts heat (energy) from the air. Evaporation of 220 lbs/hr (100 kg/h) of water absorbs 235,438 btuh (69 kW) of heat from the air. Depending on the air flow rate the return air can be cooled by several degrees inside the air conditioner before being discharged into the Data Center. This cooling capacity can be exploited to cool the fresh inlet air by using a heat exchanger, with an efficiency – depending on the heat recovery unit – that may exceed 50%! This means the size, capacity and power consumption of the cooling coil and chiller can be reduced and still meet the load requirement of the Data Center.

Special care has been paid to hygiene when designing the optiMist for Legionella bacteria prevention. Hygiene concerns have been an chronic problem with ultrasonic-style humidifiers that are used by some Data Center air conditioner manufacturers.

The built-in CAREL pCO sistema+ controller automatically:

• Fills the lines only when humidification or evaporative cooling are required

• Empties the lines when there is no humidification or evaporative cooling demand for some time

• Periodically washes the lines

The washing cycle is performed using dedicated solenoid valves, and not by spraying the water being drained.

CAREL offers the following energy efficient, innovative features with this new product:

1. optiMist guarantees considerable energy savings year-round by providing evaporative cooling in summer and precise humidification control in winter.

2. Unlike evaporative coolers/humidifiers that use wet deck technology, optiMist does not create additional pressure drop for the fans on the air handling unit.

3. optiMist can receive a limit signal directly from the exhaust air fan or from the re-circulation damper actuator. This innovation optimizes evaporative cooling by ensuring water is not wasted.

4. Compared to existing systems on the market that use the wetted media technology, optiMist optimizes pump operation using an inverter, meaning no energy is wasted.

Another energy saving option is a special inverter that can control the atomizer pump with permanent magnet brushless motors (BLDC/BLAC) called power+.

Modulating the pump speed and the capacity of the refrigeration unit by integrating a CAREL pCO sistema+, produces significant energy savings. Variations in the cooling loads are managed precisely and with constant control of the compressor envelope.

This produces significant increases in the unit’s refrigeration cycle COP (Coefficient Of Performance) during operation at part load, giving higher summer cooling operational savings.

Other advantages obtainable with DC inverter technology include:

• More precise control of water temperature even in response to peaks in demand, reducing or avoiding the use of water storage tanks.

• Working at part load, the heat exchangers become more efficient and the unit can work at higher suction pressure and lower condensing pressure.

• The outdoor coil ices up less, reducing the need for defrosts on air and water source heat pumps.

Some of the main features include:

• Sensorless motor control technology
• Custom acceleration ramp
• Wide operating range, up to 140°F (60°C) ambient
• Low noise due to the high switching frequency, up to 8 kHz
• Safety torque off input

The optiMist control can easily be installed in electrical panels thanks to the gasket and smart bracket system. The heat sink can be located in the condenser compartment.

Complete integration of the pCO sistema+ means:

• Envelope control
• Integrated electronic thermal expansion valve management
• Quick inverter setup using a preloaded table of parameters based on compressor type

Carel has completed projects for Data Centers in the USA and Europe. They have also partnered with most of the important Data Center temperature control players in the market.

For further information contact:

Laura Galvani
Corporate Communications Manager
direct +39 049 9716 785

CAREL INDUSTRIES S.p.A. (Headquarters)
Via dell’Industria 11
35020 Brugine (Padua) – Italy
phone +39 049 9716 611
fax +39 049 9716 600


Woodworking and Humidification

In Winter when the outside temperatures fall below inside temperatures the cold, moist air entering the warmer building becomes hot, dry air. In the same way that moisture in the air will be absorbed by materials in a building, this hot, dry air pulls moisture from everything it comes in contact with, trying to reach “equilibrium” (the point at which the material no longer loses or gains moisture). Moisture always travels from wet to dry.

When outside air at 20°F and 65% RH is drawn inside and warmed to 70°F without humidification, its relative humidity drops to about 10%. Air travels from hot to cold.

If you take wood from outdoors that has equalized with the outside air moisture content, into a heated building with a lower moisture content, the wood will begin to give up its moisture to the dry air in the building. As the wood loses moisture it will shrink and begin to crack and check. If the wood doesn’t crack, then warping is the result. Cracking and warping is just the beginning of dry air problems in a woodworking environment. Dry wood will suck the solvent from glues before they can properly cure, leaving only the glue residue in a very weak glue joint. Shrinkage of the wood in the glue joint or warping on either side can then literally pull the joined wood apart. Dry wood also sucks solvents from paints and finishes, often leaving a rather dull finish that won’t last very long.

Cutting and sanding dry wood results in a much higher production of dust due to the dry wood fibers breaking off during the process. Moist wood fibers cut more easily, rather than breaking. Cutting dry wood increases the sharpening frequency required with many blades.

The sound of wooden musical instruments will change as the moisture content changes. , Electric, acoustic and Spanish guitars should be built in humidity controlled environments to insure the rich sound musicians expect. Most insurance companies require proper storage of valuable instruments, such as a Stradivarius violin, to be in humidity controlled environments. Mahogany sounding boards used in pianos require proper humidity control or they will dry out changing the sound quality. In addition, when the pegboards dry out the pegs become loose. Dry pianos require more frequent tuning.

In the case of a museum, where expensive paintings, sculptures and other hygroscopic materials are kept, repeated, rapid changes in the relative humidity can be devastating and  eventually destroy the artifacts.

The key to protection of wood and wooden artifacts is the stability of the environment where they are kept. It is detrimental to permit the relative humidity to vary rapidly or widely throughout the year where precious wooden articles are stored. The expansion and contraction as the wood takes up and gives off moisture will pop joints, crack paint finishes and fade finishes.

Dry air results in as much as 50% more dust in the air. Humidity levels below 35% relative to the temperature will allow electrical static charge buildup inside non-grounded exhaust ducts and other metal surfaces. Humidity levels above 40% in a confined space promotes dust particles in the air to agglomerate (attach to one another), become heavier and fall to the floor more rapidly resulting in less dust to breathe. Larger dust particles are also more easily captured by filters in the air handling system. Viruses will also stick to the larger dust particles that fall faster. That results in a reduction of air borne contagious agents. The flu season really means the dry, winter season when small flu viruses stay dispersed in the air longer after someone sneezes.

In most woodworking, painting and printing environments, a Carel® humidification system will pay for itself in reduction of scrap and quality improvement in less than one year. Woodworkers should also recommend to their distributors and retailers that their high quality furniture, instruments and cabinets be stored and displayed in a humidity controlled environment, and that the owner do the same.

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