FREE COOLING

Data center designers and managers who are looking for ways to reduce water usage and energy costs often find that traditional cooling technologies are not the answer. For example, traditional direct expansion (DX) systems, while simple and scalable to deploy, do not typically have the energy efficiency of chilled water systems or evaporative air-handling systems. However, chilled water systems are not easily scalable, and large air-handling systems are not ideal for data center applications.

In response to these challenges, Vertiv introduced the Liebert DSE™ Free Cooling System with pumped refrigerant economization. This stand-alone system is highly scalable and can be applied in new construction, retrofit, and expansion situations with mixed cooling systems, such as legacy DX and chilled water systems.

“The Liebert DSE Free Cooling System is a breakthrough technology with significant energy savings and no water usage,” said JP Valiulis, vice president of North America thermal management product strategy and marketing, Vertiv. “It is a pumped refrigerant economization system for data centers that provides free cooling throughout much of the year.”

The DSE system’s four components — a computer room air conditioning (CRAC) unit, refrigerant pump, high-efficiency condenser, and iCOM controls — work together to maximize free cooling and ensure the highest protection by providing free cooling economization with DX backup. The system components are managed by the iCOM unit control, which allows the unit to go into economization mode automatically when conditions meet the criteria to support the load.

“The economization mode is not based on a fixed outdoor temperature or chilled water temperature, Valiulis said. “The unit can operate at the most efficient levels according to heat loads and ambient temperatures. It can turn off one or both of its unit compressors and instead engage the refrigerant pump, which uses just 7 percent of the energy used by the compressors.”

The Liebert DSE was designed specifically for mission-critical data centers, and while it can operate in any location, optimal full economization occurs in locations that enjoy relatively cooler seasonal or nightly temperatures. The Vertiv Free-Cooling Economizer Calculator can show the amount of full and partial economization estimated for cities throughout the world, noted Valiulis.

LOW SPEED VENTILATION

Servers in data centers can generate huge amounts of heat, which, if left unchecked, can result in premature equipment failure. Conventional server cooling technologies often involve high air speeds of 8-9 meters per second, but moving air at this speed can not only be energy intensive, it can trigger the Venturi effect, which leads to air pressure variations and the hot spots that can cause servers to overheat.

To solve this problem, Alfa Laval introduced Low Speed Ventilation (LSV) technology, which delivers air at a considerably lower speed of 1.5-1.8 meters per second.

“Low-speed ventilation works by flooding the server room with enough air via large air coolers. By using slow-moving air, no Venturi effect is introduced and no pressure variations will occur,” said Mats Carselid, business development manager, Alfa Laval.

LSV coolers, located outside the server room, are typically connected to a chiller in the summer and to free cooling equipment in colder periods. Reducing air speed and delivering an optimum airflow minimizes pressure differences in the space and therefore prevents problems, such as hot spots.

“Other key benefits of LSV include less infrastructure, simpler control, no water in the server room, and less maintenance,” said Carselid. “And, of course, reduced energy consumption. Energy savings in kW are in the range of 40-50 percent compared to conventional server cooling technology, and the return on investment can be as low as one year.”

The LSV system can be used in any type of data center, large or small, and in any geographic location.

REMOVING HEAT

Thanks to the need for extensive cooling infrastructure, data centers are one of the fastest-growing energy consumers on the planet. Indeed, the cost to cool data centers is one of its biggest expenses, often outpacing the costs of the actual electrical equipment and infrastructure. In addition, data centers use a lot of water with an average unit of compute using up to 9 gallons of water per hour.

Recognizing the need to significantly reduce the amount of power and water used in data centers, Aligned Energy designed a cooling system that uses up to 85 percent less water and up to 80 percent less energy than traditional data centers.

“We designed our cooling technology with two specific goals in mind,” said Earl Keisling, CEO, Inertech LLC, a division of Aligned Energy. “The first goal was to design an advanced system that was just as efficient at part-load conditions as it would be in full-load conditions. Secondly, we wanted to treat the system as a heat removal problem versus a cooling problem.”

The system close-couples heat extraction exchanges at the heat source and utilizes technology that extracts the heat from the local environment to do the majority of the cooling throughout most of the year. “We deconstructed the standard chiller plant and put the major components in the most efficient places,” said Keisling. “The eSync is essentially an evaporator that is installed over the hot aisle between IT racks. The cooling distribution unit (CDU) is made up of a refrigerant pump and a heat exchanger, which, in conjunction with the patented, efficient CACTUS cooler — our version of a fluid cooler — allows us to remove heat using less water and energy.”

While other cooling systems are typically mechanical systems with free cooling benefits, Aligned Energy’s solutions are free cooling systems at their core with mechanical enhancements that come into operation only when the local environment cannot perform all of the cooling necessary to operate the data center by itself or when water or power are in short supply. The cooling technology can be used in any environment, but its benefits are even more pronounced in high-temperature and high-humidity environments.

“Our system components are also prefabricated and rapidly deployable, so contractors can be trained to install and service systems very easily,” said Keisling.

LOW-CHARGE AMMONIA

In addition to reducing energy consumption, many data center owners and designers are looking to utilize refrigerants that have no global warming potential (GWP), such as ammonia. While ammonia has been used for decades in large, industrial systems, it has not been seen as an attractive option for smaller facilities or facilities in highly populated areas due to safety concerns (ammonia does not harm the environment but can be toxic to humans in certain concentrations). But low-charge packaged ammonia systems mitigate much of the safety risk and are opening the door for ammonia to be used much more broadly in commercial applications, such as data centers.

“Low-charge systems work by limiting amounts of liquid in the system that do not benefit the system from an efficiency or reliability perspective,” said Caleb Nelson, vice president of business development, Azane Inc. “Charge is also reduced by close-coupling all of the ammonia containing components inside the package and distributing the package closer to the load.”

Ammonia must be used in indirect systems where the refrigerant itself is isolated from HVAC airstreams in occupied spaces, said Nelson.

“For HVAC and other applications, ammonia chillers can provide the cooling of a water or glycol loop, which can safely be pumped through air handlers or other heat exchangers for a variety of uses,” he said.

One of the main benefits of using ammonia is that it will not be restricted under the Montreal Protocol, like R-22 or hydrofluorocarbons (HFCs). It is also a safe-to-use, energy-efficient refrigerant that can be used in just about any location or climate.

“Similar refrigeration systems using HFC refrigerants may consume 15-25 percent more energy than an ammonia system,” said Nelson. “When you consider the higher operating costs, increasing refrigerant prices, and potentially higher maintenance costs of synthetic refrigeration systems, we see ROIs of five to seven years with ammonia.”

Azane low-charge ammonia chillers also use no water, as they are designed with an on-board air-cooled condenser, said Nelson. “The Azanechiller has been designed to reliably operate in ambient temperatures up to 105°F, so there’s a large geographic area where the air-cooled option is available.”

Low-charge ammonia systems are built in a factory with the condenser integrated into the package, so the on-site installation process involves setting the system on the ground (or roof) and connecting power and cooling lines to the load. The systems are designed to operate automatically with on-board controls, so there is no need for constant on-site technical support, which has traditionally been required with large ammonia systems.

“Contractors who offer low-charge ammonia systems will have an opportunity to increase their customer bases as well as provide an efficient, future-proof solution that makes business sense for their customers,” said Nelson.   

Publication date: 8/14/2017

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