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Risks and benefits of eco mode in server room UPS
In today’s business world, energy saving” and “eco mode” are two phrases that conjure up positive connotations. After all, given the global drive towards improved energy efficiency, and a local need to save electricity in order to save costs, anything to help to save energy can generally only be a good thing. By Elrica Quick, APC product specialist at Drive Control Corporation
However, the reality is that this is not always the case. When it comes to Uninterrupted Power Supply (UPS) solutions, eco mode is not necessarily desirable in all applications, including the server rooms of many Small to Medium Enterprises (SMEs). The benefits and the risks of eco mode need to be carefully considered before such a solution is implemented, in order to ensure that any unanticipated side effects do not cause adverse conditions that can be detrimental to business and sensitive IT equipment.
Different vendors have different names for eco mode, and there are also a number of different technical terms, all meaning the same thing. These include bypass, advanced eco mode, energy saving systems, super eco mode, voltage and frequency dependent, and maximum energy saving mode. These names all ultimately translate to the same thing: a method of operating a UPS at reduced power costs in order to obtain improved electrical efficiency and save energy. Eco mode does save energy, although not as much as one would expect, and the amount saved is often surprisingly small. In addition, this energy saving typically comes at the price of reduced reliability and reduced protection. Organisations need to make an informed decision as to whether or not the energy savings are worth the risks and potential problems.
Ultimately, eco mode is very similar to the basic mode of operation used in an offline UPS. This is also known as standby mode. There are two modes for a UPS which are standby and line Interactive. A standby UPS, also called an “offline UPS”, is the most common type of UPS found in a computer or office supply store. It draws current from the AC outlet and switches to battery within a few milliseconds after detecting a power failure. An online, double-conversion UPS, on the other hand, will ensure that load is not subject to power disturbances, even during mains power problems such as load shedding. In eco mode, however, the UPS allows raw mains power to supply the load. Using a double-conversion UPS operating in eco mode, as with an offline UPS, will therefore typically expose the load to raw utility power, making it susceptible to voltage fluctuations and surges.
The benefit of eco mode is that it can improve efficiency by between two and five percent. However, this comes at the cost of exposing the load to raw mains power, without the conditioning normally provided by the double-conversion, online UPS. The UPS must continuously monitor the mains power and quickly switch to the UPS inverter when a problem is detected, before the problem can affect the critical load. This is a fairly complex process that introduces a number of risks to the process, and can have several side effects that are less than desirable for critical applications such as server rooms.
Estimated energy savings of using a UPS in eco mode is approximately 2.3% for a system operating 100% of the time in eco mode. These savings will be proportionally reduced if the system only operates in eco mode for part of the time, and are also dependent on the configuration of eco mode on the UPS. However, while a saving in energy of 2,3% can be fairly substantial for an energy-intensive business, there are a number of consequences associated with utilising eco mode, including reduced electrical protection, impact on reliability, and operational issues.
One of the key functions of a UPS is to provide clean power without fluctuations of voltage and frequency, which often occurs using raw mains utility power. These fluctuations can interfere with sensitive equipment and cause a number of issues. The more sensitive the UPS load, the more susceptible it is to unstable power supply, the more important it is that the UPS provide line conditioning, which negates the use of eco mode. Eco mode takes time to respond to power problems, and problems with the mains power can therefore make their way to equipment in eco mode. Reductions in power protection using eco mode need to be carefully considered before the decision is taken to use such a system.
Eco mode can also affect system reliability, as a system operating in eco-mode will need to start the inverter and transfer in response to detected power events. This change in power can cause problems such as thermal shock, which in turn can cause failure of electronic power systems. Furthermore, battery life can be adversely affected by utilising eco mode, as it can create unnecessary battery wear depending on the implementation of eco mode, local power quality, and eco mode settings. In addition, eco mode may switch off fans, which will result in batteries operating at higher temperatures, again shortening their usable lifespan.
Finally, eco mode can have operational consequences, and it is therefore essential for organisations to test in order to determine whether or not eco mode is compatible with the environment, as well as to determine appropriate eco mode settings. Eco mode settings can be adapted to the requirements of a particular site, including adjusting sensitivity and delays. It is important to adapt eco mode settings according to actual conditions, in order to ensure it continues to provide the right level of protection and functionality.
Eco mode has the potential to help organisations save energy, and the savings realised depend on the configuration, load and application to which the UPS is being used. However, as newer generation UPS systems feature improved efficiency, the associated energy savings of eco mode are reduced. In addition, eco mode has a number of undesirable side effects, such as reduced power protection and unpredictable responses. Organisations need to carefully consider the benefits and risks before making a decision as to whether or not to implement eco mode in their UPS environment.