Sensors Mag

Energy Saving: Measure It To Manage It!

July 31, 2009 By: Loïc Moreau, LEM

Loïc Moreau

Today energy efficiency is paramount in the minds of most organisations. Yet most organisations have little idea of how they use energy, whether they are efficient, or what are the opportunities for improvement.

Because energy usage often represents a large proportion of an organisation's costs, any improvements in efficiency will benefit both the bottom line and the environment. Despite this fact, many organisations spend a large amount of time minimising equipment purchase costs, but pay little or no attention to the running costs. For equipment that consumes power this is a big mistake! For example, 95% of the costs of a motor may be the energy it consumes, with maintenance accounting for 3% and the motor's price accounting for only 2% of its total lifetime costs.

Organisations need to understand where and how energy is being used if they are to identify opportunities for reducing energy use. As Lord Kelvin stated more than 100 years ago, "If you can measure it, you can manage it".

Energy monitoring is a key factor for compliance with a range of regulations being enacted throughout the EU. Through legislation, governments hope to achieve carbon dioxide emission targets and to make businesses in their countries more competitive. In the U.K. the carbon reduction commitment requires large organisations to monitor energy use and report on their equivalent carbon dioxide (CO2) emissions and its building regulations require new commercial buildings to record, by function, at least 90% of their energy usage.

Because most organisations don't have a good picture of how and where they consume energy, they need to start measuring without delay. The benefits are clear, so why is it not being used to its full potential? The principle reason is the association of monitoring with conventional sub-meters, associated with difficult, disruptive, and expensive installation. Modern wireless energy meters offer a simple, low-cost and flexible approach that allows organisations to acquire detailed measurement data, providing facilities managers the information they need to track and allocate energy costs to particular activities, allowing them to identify areas where energy is being wasted.

Measuring energy consumption can be particularly useful in industrial applications where it can be used, for example, to benchmark one production cell against another. Any major discrepancy indicates a need for investigation, which may reveal problems such as motors using too much energy because they have worn bearings, or equipment that is operating inefficiently because it is in need of lubrication or other maintenance. Identifying such issues not only eliminates energy wastage, it also helps to prolong the life of machines and equipment by highlighting potential problems so they can be remedied before developing into full scale failures.

Wireless communication is ideal for installations in existing buildings, allowing deployment with little or no disruption to the organisation using the premises. It also enables measurement of energy use to be implemented in applications such as historic properties, where installation of additional cabling is not permitted and therefore monitoring usage would previously have been difficult or impossible.

The process of minimising energy consumption is an iterative one, typically following a cycle of plan-do-check-act (also known as a Deming or Shewhart cycle). This iterative approach often means systems measuring energy use need to be modified to allow for more detailed investigation of potential wastage, or to accommodate changes to the internal layout of a building. Wireless transducers can be moved around as needed, with minimal disruption and very little cost. New technologies mean that no reconfiguration of the equipment is required as the transducers automatically recognise and communicate with the nearest repeaters and gateways. This also ensures exceptionally reliable operation, as the system can reconfigure the network to bypass equipment that has failed. The latest devices also offer an RF output power of 10 mW, providing a long range within the building, even when transmitting through walls.

Unlike conventional sub-meters, modern energy monitoring systems can provide detailed information on parameters such as active and reactive power, current, and voltage in real time. Understanding short-term changes gives greater insight into the way energy is used and helps organisations reduce peaks in consumption, which are often linked to higher tariffs.

Modern energy management solutions give organisations the opportunity to integrate their measurement of energy use by monitoring other utilities such as gas and water as well as environmental information such as temperature and humidity. This approach provides much richer measurement data that can often make it easier to identify problems. For example if a heating system is operating on a warm summer day, there is clearly a problem that needs immediate investigation.

The benefits of measuring energy usage are well understood, yet because of concerns associated with conventional sub-metering, many organisations fail to take advantage of these benefits. Modern wireless solutions, such as Wi-LEM, offer straightforward, non-disruptive, and inexpensive installation and operation as well as the opportunity to monitor other utilities and environmental conditions. With so many benefits and none of the old drawbacks, there are no excuses: organisations must start measuring energy usage now!

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