Fullscreen HTML5Med Res (??MB)HTML4

You may not be aware of it but without going to any real expense, you can make major energy savings at home and in the office. Nor do you have to make any compromises in day-to-day comfort. All you have to do is be aware of what all your appliances actually consume and then take appropriate action. How To Cut Greenhouse . . . and save real $$$$ into the W e are all told – increasingly often – to turn things off, use less energy, use energy efficient appliances. But it helps to understand how much appliances and activities use, to know what to concentrate on. To give an example, it makes no sense to turn off just a lamp in a room where an electric heater has been left on. The power used by the lamp may be 100 watts while the heater draws 2000 watts or more. The 100W light globe To start, let’s pick a familiar energy-using object as a yardstick, say the 100-watt light globe. How big a yardstick is 100 watts anyway? Let’s assume that a globe is on every night for six hours. That’s about 2200 hours a year. So to work out the amount of energy used over that year, all we have to do is multiply hours by 10  Silicon Chip watts to get the energy in a unit called watt-hours: 2200 x 100 = 220,000 watt-hours. To make it more manageable, we divide that figure by one thousand to get 220 kilowatt-hours, abbreviated to 220kWh. To many people, a number like 220kWh doesn’t mean much – so let’s convert it into something familiar– say litres of petrol – energy equivalent. A litre of petrol contains about 10kWh of energy. A kWh is 3,600,000 watt-seconds which is 3.6 megajoules (3.6MJ; a joule is a watt-second). An unfortunate consequence of the laws of thermodynamics is that the process of producing electricity by burning fuels is not very efficient. The best that can be achieved by burning brown coal to generate electricity (as is done in Victoria) is 25%. So four times as much energy is used to deliver what ultimately comes through your electricity meter box and power points. So 4 x 220kWh of fuel to produce that electricity = 880kWh. Translated into litres of petrol that comes out to 880/10 = 88 litres – enough for the average car to drive 880km or from Melbourne to Sydney. Surprising isn’t it? That’s just to run one 100W light globe each night for a year. Black coal electricity generation is more efficient – about 30%. So the siliconchip.com.au Part 1 by Peter Seligman, PhD t Your Emissions bargain! figures for other states are 660kWh and 66 litres, etc. A seemingly insignificant light globe used every day goes through a lot of fuel (and energy) over a year. Another way of looking at this is the amount of carbon dioxide (CO2) that is produced to run the light globe compared to the CO2 produced by a car being driven a certain distance. Because coal produces more CO2 for the same energy than liquid fuels, the equivalent distance for the light globe is over a 1000km. Ready for another surprise? You turn on the taps and jump into the shower. I won’t go into the issue of how long you might stay in there but let’s look at how many light-globe equivalents of power is used while the shower is running. If we are talking about an electric hot water service, these are generally heated at night over a period of about six hours – well, slightly less because they build in a safety factor to take into account very cold weather – let’s say siliconchip.com.au five hours. The normal heating element in an electric hot water service is about 4800 watts (4.8kW). Translating that into 100W units – that’s 4800/100 = 48 light globes. Now let’s look at how quickly that water could be used. How long would it take to drain your hot water service if you just showered on until it ran out? About one hour? OK, so that means you can drain it five times faster than re-heat it. So while that hot water tap is on, the energy going down the drain, is the equivalent of – wait for it – 5 x 48 = 240 light globes! I suspect many people, if they could see the 240 globes shining while they were showering, might take much shorter showers. Common myths Now let’s get onto some common myths and misconceptions. Myth 1: how many of us have heard that fluorescent lights are very efficient? It is certainly true that fluorescent lights are much more efficient than incandescent lights. Here the main problem is the sheer numbers of lights installed. A typical 1 to 2-person office may have four twin tube fittings. I’ll let you in on another secret. The tubes may be rated at 36W but the complete fitting (which includes a transformer-like object called the ballast) uses closer to 50W. In a twin tube fitting, that’s about 100W so the office comes to four incandescent light globes. I was amused the other day when a friend was leaving his office. He turned off the 50W desk lamp (to save energy – “well, it felt hot!”) and left on 400W of fluorescent lamps (because they hardly use any energy – you don’t feel the heat from those, unless you are up close). Myth 2: have you heard that it takes more energy to switch lights on and off than leave them on? This is a popular July 2007  11 Here’s a typical 2-tube fluoro fitting as installed quite literally in their millions. These are rather wasteful of power due in part to their “leakage” of light but mainly due to their diffusers (as shown in the inset at right). one because it is so convenient to believe. But it isn’t true. Its origin can be traced to a time when fluorescent tubes were new, expensive and their life was shortened by frequent switching. But in terms of energy – an hour switched off is an hour’s worth of energy saved. And it doesn’t use even a little bit more when you switch it on again. Today’s tubes last for tens of thousands of hours whether you switch them or not and they cost about $3. The rationale for leaving them switched on has long passed – if it ever existed. This myth was recently thoroughly debunked on the American “Myth Busters” show on SBS. If you are to leave the room for more than 10 minutes, turn the lights off. Here’s another tidbit of information: in an air-conditioned building, it takes 30W of air-conditioner power to extract every 100W of heat generated (by the lights or anything else). So a 100W fitting effectively uses about 130W once you take air-conditioning into account. You might have the impression from what I have said that fluorescent light tubes are very inefficient. Not at all! They are amongst the most efficient means of lighting – in fact they are more efficient than compact fluorescent lights (CFLs). The problem is the way they are used and over-used. A single unencumbered tube can adequately light a kitchen-sized room or office. Recessed lights with diffusers waste a lot of the light. Newer fittings with 12  Silicon Chip You don’t see this type of fluoro fitting much but it is generally much more efficient than the diffused type at left. The vertical reflectors are shown close-up at right. In this case they are bright, shiny metal but some types are plastic. These ensure as much light as possible goes down – where it is wanted! reflectors and no diffusers are much better. Finally, you will be surprised when you change older tubes for the new Tri-phosphor types. Their light output is so much higher that you can omit one-third of the tubes and still get the same light level. 12V halogens are huge power wasters output than a 50W halogen has just been announced (see p15). CFLs? As far as CFLs are concerned, see the comprehensive article in the April 2007 issue. In general they cannot be regarded as direct replacements for 12V halogens. However, there are now compact fluorescent replacements which only use about 11W. Don’t get fooled by the ads, the 9W watt ones are not as bright. I have tried 18-watt incandescent replacements which seem to be quite satisfactory for spot or feature lighting. Let’s now look at low-voltage downlights, ie, 12V halogens. Whoever thought that these were a good idea? Not only do they only light a small area, they use lots of power. Because of the 240VAC to 12VAC step-down transformer, each downlight, rated at Computers, too! 50W, actually uses about 60W. Many consumers believe low Desktop computers are another voltage means low energy – in fact, you power hog. How many of us have a often see adverts implying this. And desktop computer churning away all if you ask any salesman in a lighting day and maybe all night, too. These store, well . . . But nothing could be further from the Laptop computer power consumption over one day truth. The main problem with these lights, apart from their inherent inefficiency, is that too many must be installed to get adequate lighting. It is not uncommon to find six or more in a kitchen – another 400W. Here’s a sobering graph: laptop power consumption But there is light versus that of the average desktop! With the performance of today’s laptops, which would you go for? on the horizon: a LED with higher siliconchip.com.au This entertainment unit has 10 different devices all consuming standby power day in, day out – from the TV itself to a satellite TV receiver, digital set-top box, DVD and CD players, DVR and even a couple of VCRs (count the remotes!). The total is revealed as a whopping 55W by the SILICON CHIP Energy Meter (published July/August 2004). That’s 1.3kWh per day or 481kWh per year. typically use about 120-160W – some significantly more – although this drops to about half if the monitor switches to standby. Nevertheless, on average it may be about 100W for eight hours per day or more. Think in terms of that Melbourne to Sydney trip each year. The good news is that laptop computers use only about 25W – and even less on standby (my laptop uses a remarkably low half a watt of mains power on standby). LCD monitors also use less power than CRT monitors – about 20W. The only reason to leave a computer on continuously is if it is very close to the coast. A cooling computer (after you turn it off) is bound to condense the moist, salt-laden air which the fan has drawn in – with usually disastrous results in just a few months. Standby power – the “hidden” energy gobbler You should be aware that many appliances and electronic devices, particularly those in the entertainment area, use power all the time – even when they are “switched off”. Of course, they are not actually “off”. This “standby power” is largely unnecessary. Until recently, designers didn’t give this aspect much attention. The result is that many modern appliances can use more energy on standby than doing their job, because they are left permanently on. siliconchip.com.au As an example, consider a typical new washing machine with electronic controls rather than a simple mechanical timer. On standby, when it is doing absolutely nothing, it uses about 5W or 120 watt-hours per day. The machine uses about 50 watt-hours (not counting the energy to heat the water, which is less common these days with “cold water” detergents) to do a load of washing. Its direct drive motor is superbly efficient but for the rest of the day it uses 120 watt-hours doing nothing! The solution: simply turn it off at the power point. It is the sheer numbers of these appliances which is the problem. We have microwave ovens, TVs, VCRs, DVD players, sound systems, all with their individual clocks and displays. A typical household might have 10 such units. So unless an appliance actually has time setting functions you need to program – switch it off at the wall. Is there really any need for the TV to sit there all day and night just waiting for you to press the remote control? (Editor’s note: some home theatre and other entertainment equipment cannot be turned off or you will lose all your preferred settings – another case of bad design). Here’s another example along those lines. My son recently installed a new split-system air-conditioner. It’s a 5-star rated system but here’s the surprise. This air-conditioner draws 10W on standby. Let’s do the calculations: 10W for 24 hours a day, 365 days a year comes to 88kWh per year. Now let’s work out the likely usage when it is running. In Melbourne, there are perhaps 20 hot days a year, when it would be used for eight hours and for those eight hours it would run nearly flat out. That’s a crude assumption but it will serve as an illustration. Running flat out, it draws 550W. At eight hours for 20 days, its air-conditioning energy consumption comes to 88kWh per year! So this 5-star rated appliance uses as much energy on standby, as when it is doing its job. That’s just crazy. What to do? Get a switch installed so you can just turn if off completely for most of the time. And do you really need all those devices with digital clocks, showing the same time in every room (and sometimes two or three per room!), all chewing up “standby power” 24 hours a day? Solar energy? Umm, well . . . Finally, let’s get onto solar. Why don’t we just go solar? This is excellent for water heating. You won’t have to think about 240 light globes, just about wasting water. Actually, water isn’t just water. There is a substantial energy cost in delivering water to consumers. July 2007  13 Think about the infrastructure cost (and energy input) to build and run dams, pipes, pumping stations, water treatment (filtering & chlorination), then sewage pumping and treatment. But solar for electricity? Well let’s do the sums. It costs about $10 to provide a watt from a solar panel in brilliant sunshine, when the sun is shining straight onto the panel. Panels are sold by this “peak” power. However, you have to take into account the varying sun angle, nighttime and the weather. For Melbourne or Sydney you would find that average power is about one seventh of the peak power. That’s right, one seventh. They don’t tell you that in the glossy brochures. So an average “solar” watt costs about $70. Then there are the frames, the installation cost, wiring, etc. Generally that doubles the cost again. In some states the government will pick up a proportion of the cost. But think of it this way: how much does it cost to save a watt? Changing an incandescent globe to a compact fluorescent saves on average usage (80 watt saving for say 6 hours 14  Silicon Chip out of 24) about 20W. Cost to make the change? About $7. Replace 10 times over 20 years – say $70. Cost of a solar system to provide an average of 20W? Wait for it: $20 x 70 = $1400. Or if the government is paying half, about $700. In this example, it costs10 times as much to provide the power as it costs to save it in the first place! Huge potential for saving I hope I haven’t depressed you too much but there is good news! The potential for saving energy really is huge – if you just understand where it is all going. I was sitting with my colleagues having Friday afternoon drinks in our lunch room when I thought about how to present these ideas to them. I counted the double fluoro fittings. Six hundred watts to light a room which has large windows right across one wall. “Look at these lights” I said. “There’s no need for them to be on at all”. “Look at those spotlights – lighting the floor behind the desk – when would they ever be useful?” They looked at me askance, as if I had suggested that missing dinner was a good energy saving measure. Were these the same colleagues who asked me if I had seen the Al Gore movie? (I hadn’t). But why would anybody who was troubled by the Al Gore message think that even these trivial “sacrifices” were asking too much? I didn’t even get to point out that we had a total of 6000W of lighting switched on. You see the office only has three switches, which are not zoned in any sensible way – so we were lighting the whole office while we were using only one room! A couple of hours of an electrician’s time fitting new switches could cut this significantly. As it is now, say 10 hours per day (it’s probably more) x five days a week (often six!) x 52 weeks x 6000W . . . 15.6MWh! How many times did you say you wanted to drive from Melbourne to Sydney and return each year? Want to detour via Perth and Darwin as well? In the next part of this article, we will investigate how to make big savings in water heating and space heating. SC siliconchip.com.au