With the rapid economic development, China is facing many challenges in energy supply. Energy-saving and emission-reduction has become a basic national policy, and the data center is one of the industries consuming huge energy.

A constant cooling indoor temperature throughout the year in the data center should be maintained, so a huge amount of power consumption and electricity cost is produced. The dual pressures of energy-saving and reduction of operating costs force people to develop new energy-saving technologies and products continuously. Room air conditioning needs refrigeration all year round, but when outdoor temperature is lower than room temperature in transition season, a rich cooling source exists in nature, how to take full advantage of the natural cooling source to refrigerate is the key issues of energy saving of room air-conditioning.

From the above figure, in China’s north, northwest and northeast regions, the percentage of days that outside temperature is below 10℃ of the whole year is quite considerable. Nature is the best source of cooling, not only saving the energy consumption of mechanical refrigeration, but also providing adequate supply with non-polluting, belonging to the green cooling source.

The cooling solution of data center used for natural cooling source is mainly divided into two ways, indirect natural cooling and direct natural cooling.

Indirect Natural Cooling

Air-Cooled Chillers With Natural Cooling Energy Saving Module
In spring and autumn transition season and in the evening, when the environment temperature reaches 2℃ or more lower than the temperature of chilled return water, turn on the natural cooling module to refrigerate without compressor power consumption. If the natural cooling part is not enough, start compressor refrigeration to the required cold requirement. As the outdoor environment temperature decreases, the proportion of the natural cooling is growing gradually until it reaches 100% to completely natural cooling refrigeration without compressor power consumption.


Water Side Panels Energy-Saving Devices

It is comprised by large cooling towers, water-cooled chiller, plate heat exchangers. Chillers and cooling towers will be used to refrigerate in summer. In winter, panels will turn impurities cooling water into clean chilled water, and then delivered to the air conditioner indoor unit, chillers shut down.

Double Coiler Glycol Natural Cooling
On the direct expansion evaporator coil and a set of chilled water coil regulate water through two sets of two-pass valve to decide whether through a plate heat exchanger or chilled water coil. Outdoor dry cooler in summer provides cooling water board for direct expansion refrigeration. In winter it will provide chilled water to the coil for chilled water cooling.
Fluorine Pump Natural Cooling
In summer, the refrigeration compressor runs. When the outdoor temperature is below the set point, automatically switch to run the fluorine pump energy-saving system, then, stop the compressor to ensure the safe and reliable operation of room air-conditioning throughout the year. Fluorine pump consumes not higher than 10% of the power of the compressor running. Relative to the water system of air-conditioning, it needs no addition of antifreeze and no flooding worries.

Assisted Evaporation Of Natural Cooling
Atomized water spray system of air conditioner outdoor unit pressurizes the water through high-speed DC motor atomization. The every drop of atomized water becomes about 1/500 of the volume of raw water, spraying directly to the fins of condenser reaching the target of auxiliary evaporation. The overall heat dissipation of the condenser increases, and power consumption reduces. The way of extending running time through the outdoor unit atomized spray natural cooling is most effective in dry climates, such as western and northeast of China.
Direct Natural Cooling

New Wind Natural Cooling
Room cooling is realized by getting directly the outdoor air with hot and cold channels, for different climatic conditions of the region, the new wind needs to go through the filter, humidification, dehumidification, and sends back to the wind mixing pretreatment before entering the room.
It does not need mechanical help, and dissipates heat directly relying on the power generated by server natural heat. Collect the heat from the server, use upward momentum resulting from the expansion of the air, and allow the hot air to rise driven by air flow through the chimney high enough to finish cooling cycle.

Wheel Heat Exchange Natural Cooling
Take advantage of the storage function of filler within the runner to make the wheel slowly rotating in the two closed duct, the filler cooled by the outdoor air is used to cool the inside air.
　　

In summary, a comprehensive comparison of several common natural cooling refrigeration ways is conducted below.