E NE RG Y MAT TER S FACT SHEET 8: REDUCING CONSUMPTION There are many ways in which energy consumption can be reduced, but basically they fit into one of two categories: • only using devices when actually needed • making sure that when the device is being used that energy is not being wasted 1. Managing The “On” Time The most powerful technique of energy conservation is turning off equipment when it is not needed. If the device is switched off when not needed, it doesn’t consume energy. The switching can be: • manual – they require a person to switch them on or off • individual timers – a mechanism within the switch itself, which could be a push button which releases itself slowly or a dial which allows the user to set a time that the device stays on for • scheduling systems – remote control systems which are programmed to switch equipment off and on at preset times or conditions (eg temperature) • occupancy or temperature sensing – a sensor recognises when the equipment (eg lighting, air conditioning) should be on Time clock controls are a primary tool for this latter function, because most equipment is needed on the basis of specific time schedules. Achieving effective and long-lasting clock control involves a number of key design features: • sufficient flexibility to adapt to all the predictable variations in schedule, such as weekends, public holidays, leap years and daylight saving • • very clear instructions for setting and adjusting them easily used overrides that allow users to easily bypass the timeclock when equipment is needed during unscheduled periods Lighting control systems also need to have some warning system in place, so that persons still in the facility when the lights are due to be switched off know that this is about tho happen, and can use the override if necessary. Occupancy recognition is the strategy applied to intermittently occupied areas to turn lights on when people are present and automatically turn lights off after the room is unoccupied. The two principal technologies used for occupancy sensors are passive infrared (PIR) and ultrasonic. Standby power Many modern appliances, such as TVs, computers and ovens, use power all day and night, even when not in use. This standby power may be substantial and required to maintain a convenient 'ready' state for instant, on demand use. However, in some cases, standby power serves no useful function or operates at excessive levels for the background task being performed. Standby becomes necessary to power certain core functions or to sense communication for those products that are waiting to provide full services. This power is consumed not while the appliance is being fully utilised but while it awaits instruction; while it is "standing by". Some appliances also perform a continuous function that requires small amounts of continuous power. Getting the message across Much of the energy consumption within a facility is in the control of people, not electronics. Therefore, education of the workforce is essential. This can mean training sessions for the “big picture” but on a day-to-day basis, means signage. Some of the communication problems that workforce education can solve are: • lack of awareness of how much energy equipment uses • lack of awareness of what can be done to conserve energy • lack of awareness of how and/or when to carry out energy conservation actions • controls are difficult to use • unwillingness to act • lack of motivation Signs will address many of the problems, and do so by in effect granting people permission to do something. However, it is critical that the signs are relevant to the environment they are placed in and specific in their information. Generic “conserve energy” signs are not worth the paper or plastic they are printed on. LOCATION • on all devices affecting energy consumption that require human action, eg windows, light switches, fan controls • in areas automatically controlled, eg lights Energy Matters 8. Reducing Consumption • where they are visible and “connected” to the equipment or switch they are related to, eg next to the switch CONTENT • purpose or identity of the item • what to do (or avoid doing) • when to do it • how to do it • what response to expect • how to get help, if needed Some of these can be omitted if obvious. 2. When the switch is “on” When the device must be on, it is important that it does not use more energy than necessary to do the job that is required. There are various reasons why this is not the case: • over-specification of equipment • losses, eg poor insulation • inefficient design of equipment • operational problems It is beyond the scope of these notes to cover in detail all types of energyconsuming equipment. However, lighting is common to all situations, and Chapter 4 covers in some detail aspects of making lighting as efficient as possible. Over-specification This is where through careless, ignorance, over-conservatism or enthusiastic salesmanship, the equipment being used is more than sufficient to do the job. This is most common in lighting where the area is flooded with light, providing more illumination than is necessary for the tasks being performed. With other equipment, such as refrigeration or heating, it means that the equipment should be off more often than a lower powered equivalent, but when it is on, it is drawing more power, and the overall energy consumption is greater. However, if the over-specification is not the equipment, but the “space” that the equipment is servicing, such as a refrigerated warehouse, this will use lots of energy for no benefit. The problem of course with such over-specification is that the equipment has already been purchased, and can only Page 2 of 4 be downsized when it has to be replaced. With lights, this is a relatively cheap option, and in fact, in multi-lamp fittings, such as fluorescent housings, one of the tubes can be removed before it fails, and be used as a replacement later on, thus economising in two ways. It should be said however that some spare capacity in any system is essential to deal with extreme situations and to reduce wear on the equipment, which would otherwise be on all the time. Losses Losses of energy in this context generally refer to heated or cooled air, but can have other meanings. INSULATION Insulation acts as a barrier to heat flow and is essential to keep your home warm in winter and cool in summer. A well insulated and well designed home will provide year-round comfort, cutting cooling and heating bills by up to half. Table 1 shows the losses and gains of heat in a temperature climate such as Newcastle’s. TABLE 1 Heat losses/gains Part of building Ceiling/roof Window %loss/gain 25-35 10-20 (loss) 25-35 (gain) Wall 15-25 Floor 10-20 Air leakage 15-25 (loss) 5-15 (gain) There are two types of insulation – bulk and reflective. Each works in a different way, and has its own uses. Bulk insulation mainly resists the transfer of conducted and convected heat, relying on pockets of trapped air within its structure. Its thermal resistance is essentially the same regardless of the direction of heat flow through it. Bulk insulation includes materials such as glass fibre, wool, cellulose fibre, polyester and polystyrene. Energy Matters 8. Reducing Consumption Reflective insulation mainly resists radiant heat flow due to its high reflectivity and low emissivity (ability to re-radiate heat). It relies on the presence of an air layer of at least 25 mm next to the shiny surface. The thermal resistance of reflective insulation varies with the direction of heat flow through it. Reflective insulation is usually shiny aluminium foil laminated onto paper or plastic and is available as sheets (sarking), concertinatype batts and multi-cell batts. Commercial insulation materials are sold with an R-rating, which is a measure of their effectiveness in preventing heat conduction: the higher the R-rating, the less heat passes through. Fibreglass insulation “batts” are typically at least 10 times better insulators than the common wall and roof construction materials. Different levels of insulation are recommended for ceilings and walls. The means by which the insulation is put in place obviously differs from one type of house to the next, and also if it is going into a new building, or being retrofitted to an existing one. AIR LEAKAGE This means the unintended passage of air through the outer structure of the building, i.e. doors, windows, ceiling and walls. Leakage is caused by: • pressure imbalances – air moves due to a difference in pressure between two points; air conditioning generally causes high pressure zones, and the air inside them attempts to find means of escape • “chimney” effect – cold air is denser than warm air, and can create convection currents through a building, drawing cold air in and pushing warm air to the top of the building and out; if this is in summer, it is not a problem, but it certainly is in winter! The moving air will find “breaks” in the internal lining of the building, resulting in losses of heated air (in winter) or cooled air (in summer). Unintended breaks can best be found by “smoke testing”, using specially-designed “smoke pencils” which generate small plumes of smoke which will show up the air currents. Page 3 of 4 Maintenance All the schedulers, signs, efficient design and loss minimisation in the world will not overcome poorly running equipment due to lack of maintenance. Unfortunately, preventative maintenance tends to be the first thing cut when short-term savings need to be made. Then the inevitable happens. Breakdowns occur that could have been avoided by a regular maintenance program. Examples of maintenance failures that would cause wasted energy consumption include: • dirty light fittings • flickering fluorescent tubes • blocked air conditioning filters • faulty thermostats – a very common problem, which causes cycling (rapid stop and start) or overshooting (not stopping or starting when exceeding the set values) • motors with worn bearings or requiring lubrication • leaks in water heating or steam piping • incorrect readings on control dials and meters • broken seals on oven or refrigerator doors • poorly fitting external doors must display a standardised energy rating label, as shown below. Products regulated under the rating system include: • refrigerators and freezers • mains pressure electric storage water heaters • air conditioners • fluorescent lamps Maintenance isn’t difficult or that expensive, it just isn’t an obvious benefit until things break down. Inefficient design For much of the time that electrical equipment has been designed and built, most thought went into making sure it did the job it was supposed to as well as possible. In a lot of cases, this meant using lots of energy in the process. In the last decade or so, conscious efforts have been made to improve the energy efficiency of a wide range of equipment, and in dong so, create another selling point to distinguish item A from competitor’s item B. As householders, we are all aware of the star rating system for whitegoods, such as washing machines, air conditioners, refrigerators, dishwashers and clothes driers. What you may not have known is that it is now law that all whitegoods Energy Matters 8. Reducing Consumption Page 4 of 4