Power Electronics / Power Management


LonWorks: energy-saving through networking

12 November 2008 Power Electronics / Power Management

LonWorks is a networking platform designed and optimised for control applications. Built on a protocol created by Echelon, it is nowadays widely used in intelligent building applications and has become a standard in numerous fields such as in-train controls and semiconductor equipment manufacturing.

According to Echelon founder and Apple co-founder A.C. Markkula “Twenty years ago I founded Echelon with a very simple idea: if extremely small computers were installed everywhere to observe their local environment and exchange the collected data with each other, we could change whole industries. We imagined a world full of intelligent buildings, factories, houses and power grids using our technology to work more efficiently, lower prices and improve quality, productivity and comfort. Tremendous inventiveness and readiness to innovate were required to realise this vision, but the reality has now turned out to be far better than I could ever have imagined. Today, devices are linked in networks worldwide thanks to our technology, so that they can introduce intelligence into the infrastructure and enable progress in many different industries.”

Although LonWorks can provide benefits in terms of lowering maintenance costs and increasing productivity, the main motivation for its use is its energy-saving potential.

The basic principle in energy-saving

Anyone can save energy relatively quickly if they know where this energy is being used. This begins in a home environment, but which of us really knows where energy is wastefully ‘burned’? Hence, it is quite conceivable for audio/video systems in standby mode to consume more energy in the course of a year than a modern fridge freezer in the kitchen. Even a little bell transformer, which only needs a few watts, has an effect on the annual energy balance sheet when it is in use 24 hours a day, 365 days a year.

Energy can be saved in practically every area of a private home, and Echelon estimates that building automation also has the potential to save between 25% and 50% of energy costs in large office buildings. Using intelligent networking, it is possible, for example – based on saved data on the sun’s position, determined by means of geographical coordinates – to raise or lower a building’s sun blinds. Devices such as coffee makers, photocopiers and heaters can be automatically switched off by means of presence detectors if no one is in the corresponding area for a set period of time. These sensors can then also be used by other systems, such as the security system.

As energy costs rise, these intelligent systems are gaining traction, and Echelon estimates that in the case of home automation, payback on investment occurs within three years.

Saving energy on street lighting

One interesting application of LonWorks’ energy-saving potential can be seen in its application to the city of Oslo’s street lighting system, where it helped to lower energy costs by a massive 62%.

Previously the street lighting was switched on using ripple control technology, which offered no feedback channel: in the control room the switching on of the lights was commanded and those responsible had to hope that this command also reached the lights. To avoid any negative feedback from the local population, the street lights were consequently switched on relatively early and off fairly late in a conventional system – using repeated on or off commands.

In this application, LonWorks technology enables not only very targeted and reliable control, but also intelligent dimming techniques. For example, if the moon is not shining, the lights can be dimmed by 15 to 20%, since the subjective impression of the light is then stronger. Allowance for brightness and weather sensors, as well as traffic density information and various additional data, can be taken into consideration when setting the light level of each individual light.

In addition, maintenance costs are saved because the service life of each lamppost or lamp can be recorded precisely, and a failure is reported to the control room immediately. As a result, the actual functional ‘life before failure’ can be determined far more precisely, so that the replacement intervals can be adapted accordingly – which in turn allows the longest possible use of the lamp.

Echelon and the LonMark Consortium

Echelon is engaged in continual development of its systems, particularly in the area of its powerline solutions, and provides a complete one-chip solution including all the necessary protocols. This chip covers all communication layers, while at the same time ensuring compliance with worldwide standards.

Users of LonWorks technology have joined forces to form the LonMark Consortium to establish standards. While most bus systems fight for standardisation of the protocol, the protocol in the case of Lon was fixed from the start. Even the first-generation devices from 1992 are still compatible with new devices that have only just been developed.

For this reason, system developers were able to specialise in standardising applications and, as a result, on creating application profiles for pumps, sun protection, room management, etc. Consequently, LonMark is the most advanced among the profiles, and also has the widest profile spectrum.

Echelon has incorporated these profiles into the development environment. For example, if developers need a ‘switch profile’, a ‘sun protection profile’ and an ‘individual room control mechanism’, they combine these three profiles into one result in their Lon planning tool on their PC to produce certifiable source code. The look and feel of the device can of course be individually programmed to provide competitive differentiation.

Certification can be achieved simply by connecting the newly-developed device with a certified reference device and then automatically testing each of the individual functionalities.

Energy-saving in practice

In a LonWorks network, all facilities within a building are merged so that a logical connection exists between the areas of heating, instrumentation and control, sun protection, etc.

For example, previously it was fairly common for three individual thermostats to work in parallel with each other in hotels. Since each of these thermostats had hysteresis, the energy costs sky-rocketed in the transition period, because the systems worked against each other. The heating tried to compensate for the airconditioning and vice versa. Building equipment providers finally attempted to get this unfortunate situation more or less under control by the use of relays.

In contrast, in networked buildings, a single thermostat is sufficient to achieve ideal regulation. Moreover, there are now several sensors in one room – specifically for temperature, presence, light, etc.

For instance, it is possible with sun protection systems to set the upper slats so that light shines on the ceiling to keep the room sufficiently light. Consequently, no energy needs to be used for lighting, and there is also no wasted heat from the lighting.

This function can of course also be used in reverse: if a room is not in use and the room temperature falls a few degrees below the target level, the heating would normally be activated. In an intelligent system based on LonWorks with appropriate programming, the sun protection slats could first be raised to use the heating power of the sun, if no sun protection is required.

Intelligent network

In large buildings, a system integrator takes care of the connection of the individual building facilities at the network level, with the integration occurring via a PC, since in LonWorks there is no control room in the classic sense. Admittedly there will always be a technical function control room in a network, in which all devices can be switched off, for example. However, this control room only serves for simple operations, and from the point of view of the LonWorks network, this control room is only one operating possibility of many, since the control itself takes place within an intelligent network.

For example, the street lights mentioned earlier are equipped with Echelon’s i.LON web servers. On the one hand, they have a LonWorks connection via powerline or twisted pair connection and on the other hand there is an Ethernet connection. Every i.LON web server has its own web address: the user simply enters the specific address of the web server from any PC with an Internet connection to acquire access to the device after successfully completing the login procedure. In this device with an i.LON web interface, various data sets are then stored, such as sun position curves.

An i.LON network node is a complete device that comes ready for direct on-site installation on the DIN rail. Compared to the energy consumption of the consumer load to be controlled, the energy consumption of the i.LON network is negligible.

Additional benefit

The use of i.LONs saves service costs, since in many cases no service engineers have to travel to the location of the network installation to fix faults. Very often, a remote diagnosis or remote control is enough, since the same diagnosis possibilities are available from a distance via the web connection as would be possible via an on-site connection.

Complete downloads are also possible – and this does not just involve the downloading of new parameters but also the downloading of a complete application, so that practically the complete software of an additional application (or an update of already-implemented software) can be downloaded.

Energy-saving in refrigeration and in solar technology

In the McDonald’s fast-food restaurant chain, for instance, the entire care and remote maintenance of the refrigerating and freezing rooms now occurs via LonWorks. In this way, peak loads can be avoided – for example by cooling down the refrigeration rooms very early in the morning to two or three degrees below the normal recommended value so that the compressor can rest when all the cookers are switched on at the beginning of the shift. Similarly, the load peak at midday can also be avoided.

Another example of energy-saving is in large solar energy systems. The inverters installed here for feeding into the grid achieve their maximum effectiveness at about 90% of their maximum load. However, when clouds cover the sun, for instance, an inverter normally works only with a lower load due to the lower insolation (measure of solar radiation energy received on a given surface area in a given time) eg, 30%. However, if such inverters do not work in the optimum range, then their effectiveness rapidly falls by a significant amount – often to as low as 30%. Consequently, a large part of the energy produced by the solar cells is no longer fed in, but is completely lost in the inverter.

By using smaller inverters, it is possible to switch on the solar panels to the inverter – depending on insolation – so that it always works with the greatest possible level of effectiveness. The corresponding switching can be achieved with relatively little effort via a LonWorks network so that the maximum effectiveness is always achieved. In addition, it is possible to prepare the corresponding data graphically, so as to provide a constant overview of the energy that is currently being effectively generated or supplied.

For more information contact EBV Electrolink, +27 (0)21 402 1940, capetown@ebv.com, www.ebv.com



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