Often you hear people talk of ‘Green IT’ but, love or loathe it, it’s here to stay and proven to be more than just a passing fad, today it is rather an economic necessity. Green IT is not only concerned with saving energy, but involves other factors, such as the use of non-toxic and recyclable components. nevertheless, the key issue remains saving energy, which is unlikely to change. There are many options available for IT managers to save energy, but in reality success can only be achieved through a combination of methods
The use of power saving server systems, using classic technologies such as APM (Advanced Power Management) and ACPI (Advanced Configuration and Power Interface), has now become an industry standard. There has also been a great deal of progress made in regards to the energy efficiency of CPUs within modern systems, in some cases saving up to 90%. However, the methods and systems that ensure data centre infrastructures save power are far more interesting than the above-mentioned technologies. Uninterruptible power supplies and climate control systems play a central role in green IT as, alongside the servers, the UPS and cooling systems consume the most energy.
Progress made in semiconductor technology means there are nowadays no problems in building UPS systems without a transformer. A DC booster is used for the transformer-less technology which is a DC/DC converter that converts the voltage behind the rectifier to a significantly higher direct voltage. This increased direct voltage then allows the inverter to create a higher alternating voltage without needing a downstream transformer.
Transformer-less technology provides several advantages. Firstly, UPS systems without transformers can be built with very compact dimensions. Secondly, the transformer is not exactly a ‘lightweight’ which means systems without one are significantly lighter than conventional systems with one. Furthermore, the noise level of a UPS system without a transformer is significantly less than a comparable system with one. The efficiency over the complete load range is better for the transformer-less technology than for UPS systems with transformer.
Powerful UPS systems, such as the PMC (Power Modular Concept) from Rittal, can provide efficiency up to 95 % at under full load and up to 94% under partial load or with non-linear loads, CO2 emissions can also reduced by around 20%.
Battery management systems should also be considered to monitor all the relevant data such as battery voltage, internal resistance, discharge curve and temperature. This data can then be evaluated and used to control the charging process which can increase the lifetime of the battery by up to 30%.
System integrators and engineers should increasingly think about the enclosure and approaches to thermal management foremost in the design process. This used to be something of an afterthought, which can lead to a poor and ineffective system cooling solution, creating the problem of excessive energy costs for the end user as well as expensive down time, due to premature component failure.
So much of today’s selection criteria for an optimal enclosure solution centres on thermal performance. Thermal performance, more than any other single element of the design, will form the base line for the design of any enclosure. Depending on the application, size, and external ambient and internal heat load can each have an impact on the design used to solve the system cooling. As equipment is becoming smaller and requires dissipation of larger heat loads, a larger portion of the design effort should be dedicated to optimising the thermal efficiency of the system.
Fan and filter units are still ideal for dissipating heat loads cost effectively. The pre-requisite is the ambient air must be relatively clean and with a temperature below the desired enclosure internal temperature. Products are also now available with EMC shielding and IP54 protection category as standard and by utilising fine filter mats and hose-proof hoods higher IP ratings can also be achieved. However, in many situations, this method of cooling is not ideal, especially in environments with higher ambient temperatures or where dust or oil particles may be present.
Air-air heat exchangers use the ambient air to cool the air within the enclosure interior. Based on the counter flow principle, the completely separate airflows are routed through the heat exchanger by powerful fans; separating the internal and external air circuits prevents the ingress of dust into the enclosure. Air-air heat exchangers are best suited where the ambient air temperature is below the required enclosure internal temperature.
Cooling units maintain the enclosure internal temperature at a constant particular level which is often below the ambient room temperature. Two separate circuits prevent the ingress of dust from penetrating the enclosure. This option is normally available as a wall or roof mounted option and can be individually tailored to suit each particular application.
Air-water heat exchangers are a relatively low maintenance option to effectively dissipate high heat loads. By using the spatial separation of the heat exchanger and the re-cooling system, the room housing the enclosure is not burdened with the waste heat. In all areas with extreme ambient conditions, enclosure and climate control components are subject to special requirements but for application areas with high ambient temperatures up to 70°C and extreme dust contamination this technology offers an effective solution.
Recooling systems ensure centralised, efficient cooling using a cooling medium (generally water), to dissipate particularly high heat loads. These units can serve several pieces of equipment simultaneously such as the air-air heat exchangers. If the equipment has different requirements in terms of inlet temperatures or flow rates, multi-circuit systems can be tailored to the respective needs. Units can be provided for either internal or external siting for a vast range of kW cooling capacity.
Direct cooling packages are best for effectively cooling power electronic components. Heat loads are cleverly dissipated from the enclosure or housing using cold pate technology without compromising the high enclosure protection. Devices such as inverters are physically attached to a cooling plate which is fed by cold water from a re-cooling unit. This method of cooling is not only quiet, but also a thousand times more efficient than heat dissipation via air.
Liquid cooling packages (LCP), cater for extremely high heat loads typically found in IT or server racks. Liquid cooling, using water as the medium to transfer energy can offer the solution to localised cooling due to its close proximity to the racks. Manufacturer Rittal’s LCP is fitted as an extension to the rack or, in some cases, inside the rack itself so cooling takes place where the heat actually rises – in the server rack itself. LCP needs to be fed with a constant flow of water at a specific temperature to feed the air-water heat exchangers - normally an external IT fluid chiller. However, significant energy savings can be made if free cooling is used. A free cooling unit (FCU) uses the outside ambient air to cool the heated water by means of built in fans and delivery pumps which are integrated into the cooling unit. Free cooling cannot be used in a unrestricted way in every region and only functions when the external air temperature is at least 3k below the allowed inlet temperature of the cold water system (so is ideal for anywhere within the northern hemisphere). Depending on geographical location, up to 50% of the water can be cooled by free cooling, again, offering significant energy savings.
Today the data centre is not only being scrutinised for up time but is also importantly targeted on its environmental impact. For years silicon chips just burned energy to ensure that the data rates were maximised, now, as a result, the carbon footprint is a significant factor in any data centre design. We know the carbon footprint looks at the effect of the generation of CO2 into the environment but the more CO2 we generate the more the planet needs to absorb, and to maintain that balance is essential.
Hot aisle cold aisle systems are a common method of delivering cold air to the servers within a data centre. Using a computer room air conditioning system, generally abbreviated to CRAC, the cold air is pushed under the floor. Using vented tiles, statically positioned in front of the server enclosures, allows cold air to escape and then pulled into the server inlet. In essence a CRAC system can be broken down into three elements, an air to water heat exchanger, a fan and a chiller to provide the cold water. The hot air within a data centre is drawn through the heat exchanger by the fan and then the cold air is dispersed under the floor. Therefore, when looking at energy efficiency, there is a need to look at these elements in detail.
Software calculation programmes, such as Rittal Therm, for the climate control of enclosures, have been developed to eliminate the laborious calculation of climate control requirements. An easy to use interface leads the user to the appropriate and correctly dimensioned cooling solution.
Whether your requirement is for a new build or upgrade you can tune the energy savings to not only meet your business needs, but also provide a future proofed, energy efficient system. Going green is not a fad; it is ‘good engineering’.