Energy Saving Gets the Green Light Part 2

Transcription

1 Living with Technology, Volume 2, Issue 5 January 2005 Energy Saving Gets the Green Light Part 2 Barry Jerome, Barry Smith & Chris Walker In Part 1, we introduced low energy lighting with a quick run through of the history and the options available for domestic use. We showed that the most efficient lamps provide the same amount of visible light as a traditional GLS (general lighting service) light bulb for a fraction of the cost. The conclusion, however, was that fluorescent lighting is the only viable option for the home and that the most convenient form of fluorescent lighting is the compact fluorescent lamp (CFL). Part 2 will concentrate on the CFL, describing how it works, the types of lamps and fitments, the advantages and disadvantages and where you can get them at discounted prices. What are CFLs? How do they work? Several different technologies are used in a fluorescent lamp to create the visible light. Firstly, there has to be a means of starting up an electrical discharge in the tube. Once an electric current is flowing through the inert gas in the tube, light is generated in the ultraviolet (UV) spectrum. This UV light then strikes a phosphor on the surface of the glass tube and is converted into visible light. In Part 1, we described the advances in phosphor technology that allowed the creation of progressively narrower tubes which led to the development of the CFL. The type of phosphor also determines the quality of light output compared to daylight. Advances in the device used to start up electrical discharge (the 'ballast') have also had a dramatic impact on the size, weight and efficiency of the CFL. 1

2 The first type of CFL commercially available - the Phillips SL In the first generation of CFLs, the ballast was a large coil. This, together with a bulky tube, resulted in a large, heavy lamp. One of the first examples sold was the Phillips Comfort range of lamps, but the weight and size prevented them from being widely adopted as a replacement for the incandescent (GLS) light bulb. They were priced at about 10 per light bulb which put off many prospective purchasers, despite having a life eight times that of a 'normal' bulb and the fact that it only used a quarter of the electrical power. The increased lifetime and much greater efficiency represented a major breakthrough in domestic lighting. For the first time, there was an energy-efficient lamp, producing more visible light than heat, that could be plugged into a normal electric light socket. The next step forward was the development of the 'electronic ballast'. This had two effects: it was much lighter than the earlier ballast and, in addition, because it converted the electricity supply from 50Hz to 30kHz, it increased the efficiency of the lamp by a further 10%. The picture of the Phillips' packaging shows the reduced energy consumption of these early lamps in comparison to the ordinary (GLS) bulb. 2

3 What do they look like? As the technology has evolved, the creation of ever narrower tubes has resulted in smaller and smaller CFLs. There are several distinct designs used which are shown in the diagrams. The latest design uses a spiral tube to reduce the size even closer to that of the ordinary GLS lamp. Some of the CFLs have the tubes enclosed in a glass bulb to give a closer appearance to the GLS equivalent. What type of fitments? The advantage of the standard CFL is that it has a bayonet (BC) or Edison Screw (ES) fitting so that it can directly replace a GLS light bulb. There are versions of CFLs which don't have a BC or ES fitting; these have two or four pins, similar to a standard 3

4 fluorescent tube, and don't have a built-in ballast. They are smaller than the lamps with built-in ballast, but can only be operated by plugging them into an adapter containing a ballast. The adapters generally last for 32,000 hours (32 years of normal use!). This means that only the lamp needs to be replaced when it expires, which gives further reductions in cost. Unfortunately, these adapters aren't readily available in the shops (possibly because a 32-year life-cycle doesn't generate much trade?) and are not therefore as convenient to purchase. This may change in the future as the new UK building regulations begin to have more impact (see the table on the following page). The new regulations, introduced in 2002, require a percentage of the light fitments in a new house, or new extension, to be permanent low energy fitments. These could be standard fluorescent tube fitments, or the new low energy ceiling pendants. A low energy lamp ceiling pendant with built-in ballast, designed to accept a 4-pin lamp 4

5 Summary of the Building Regulations (2002) for Domestic Energy Efficient Lighting Internal Lighting Reasonable provision should be made for dwelling occupiers to obtain the benefits of efficient lighting. A way of demonstrating compliance is to provide, at a reasonable number of locations (where lighting can be expected to have most use), fixed lighting that only takes lamps having a luminous efficacy greater than 40 lumens per circuit-watt. Circuit-watts means the power consumed in lighting circuits by lamps, their associated control gear and power factor correction equipment. Lamps that achieve this efficacy include fluorescent tubes and compact fluorescent lamps (see the table in Part 1 of the article). A way of establishing how many locations to equip for efficient lighting is given in the following table: External lighting fixed to the building External lighting includes lighting in porches, but not lighting in garages and car ports. When providing external lighting, reasonable provision should be made to enable effective control and/or the use of efficient lamps. A way of showing compliance when providing external lighting would be to install systems that: a. automatically extinguish when there is enough daylight, and when not required at night; or b. have sockets that can only be used with lamps having an efficacy greater than 40 lumens per circuit-watt (such as fluorescent or compact fluorescent lamp types). 5

6 Advantages and disadvantages Although CFLs have a definite running advantage compared to ordinary GLS lamps there are some disadvantages which need to be considered. CFLs aren't suitable for all situations; for example, many types aren't suitable for dimming or use with PIR (infrared movement) detectors. Inappropriate use of a CFL can lead to much shortened lifetimes and reduced efficiency so that it may no longer be cost-effective. CFL GLS Notes Initial cost Running cost Size Weight Life of bulbs Lifetime costs Light spectrum Light output Use in dimmers Use in PIR fitments Temperature Use in bathroom/toilet Failure of bulb CFLs were 20 to 30 times the cost of GLS but are getting cheaper all the time (see table of 'best buys'). 4-5 times more efficient than GLS CFL is larger than equivalent GLS, but getting smaller This used to be a problem for CFLs, but latest models can be no heavier than the equivalent GLS. Lifetime is 3 to 15 that of a GLS bulb. Much cheaper over the life of the lamp (see section on 'Total cost of Ownership') GLS has a full spectrum (see Part 1), but the phosphors used in CFLs also give a good spread of light coverage. Much more visible light is provided for the electricity used (see table of equivalent wattages), but light level can be lower from switch-on for about a minute. Most CFLs aren't suitable for use in dimmers and will have a very short life if dimmed. The 2- & 4-pin lamps are generally OK but need a suitable adapter. When OK they have the usual cost advantages over GLS. Frequent switching on and off shortens the life of the bulb. The same comments apply as for dimmers. CFLs are much cooler than an equivalent GLS and can be used in fitments with limited wattages to give more light. For example, many light fittings have a 60W maximum rating. A 20W GLS lamp can be used to give the equivalent of 100W light output (if the bulb will fit). CFLs are best used in rooms where they are left on for long periods. Frequent switching on and off shortens their life (see use with PIRs). A GLS bulb has a sudden death leaving you in darkness. A CFL fades out gracefully after its normal life (becomes dimmer), but you do need to decide when it needs to be replaced. Table comparing the advantages and disadvantages of CFL and GLS lamps = Advantage, = Advantage or, no disadvantage, in certain circumstances 6

7 Total cost of ownership (TCO) Total cost of ownership is taken very seriously in business when applied to personal computers and printers. The lowest initial cost is usually not the best purchase when taking into account running costs. Many factors such as cost of consumables, reliability, operating system complexity, ease of use, etc all need to be considered (but that is another article). The same principles can be applied to light bulbs, at a simpler level, to determine the 'best buy'. The graph shows how much it would cost you to use an ordinary 100W GLS bulb for lighting, compared to an equivalent 6000 hour CFL (the low lifetime end of the CFL range), assuming average usage. If your electricity supplier doesn't charge quarterly standing charges, but includes all charges in the cost per KWh, then the savings will be even more dramatic. Graph comparing the total costs of providing an equivalent amount of light from a 100W GLS and an 18W CFL (stick type) over a six year period Total Cost of Ownership (TCO) also applies to selection of the most appropriate CFL for your needs. A cheap, low lifetime CFL may have a higher TCO than a more expensive longer life bulb. The second graph is intended to provide a guide for selecting best value between different initial prices of lamps. To use it, identify purchase price on the vertical axis and the life in 1000s of hours (or in years) on the horizontal axis. The green area indicates good value and the orange area lower value compared to our 'best buy' bulbs (which are listed later). 7

8 Graph to assist in identifying the 'best buy' from a number of options for purchasing a CFL. The diagonal line represents our 'best buys'. Above this line is lower value per bulb, below the line is better Other shapes and sizes We have mostly discussed the standard 'biaxial' or 'stick' CFLs until now because they are the most commonly used. There are a variety of other shapes (see earlier table) with varying uses. At this point, it's worth mentioning the Circolux circular lamp which started the discussion thread on the LwT forum in the first place and led to this article. The Circolux was made by Osram and is a circular version of a CFL with a BC or ES fitting. It comes in higher wattages (typically 26W or 32W) than the 'biaxial' or 'stick' versions. This gives an equivalent light output of a 130W or 150W GLS lamp. It comes in warm white or cool white, and is particularly suitable for a larger room such as a dining area. 8

9 On the left, an Osram Circolux 32W from the late 1990s, showing signs of age but still providing a useful output. On the right a recently purchased Osram Circolux 24W. In addition to the smaller diameter glass, note the different fittings (BC and ES). In the centre a conventional 150W GLS lamp. All three are designed to provide a similar light output. Adaptors are available to convert ES to BC (or vice-versa). Double-D (2D) lights are used mostly in applications requiring a broad spread of light, but without taking up a lot of space. Two frequent uses are for workshop lighting and temporary or emergency lighting. As with the Circolux, the 2D lamps also give a higher light output (higher wattages) than the standard 'stick' type CFLs. As for all CFLs, they don't get hot which can be an advantage in emergency situations. Candle bulb replacements have presented a significant challenge for CFLs, as the size of the bulb has been a major problem. 9W lamps have been acceptable, but higher wattages haven't aesthetically fitted the candle lamp fitments. Two products have been introduced to address this: the CFL 'candle' and the mini-spiral. The CFL candle looks like a candle bulb but still has some way to go on size. The mini-spiral doesn't look like a candle bulb, but does have a similar size and is unobtrusive. 9

10 The combination of smaller, lightweight ballasts and spiral tubes is succeeding in getting CFL lamp sizes to compare favourably with GLS lamp sizes. The problem has been on the higher wattages (18-20W = 100W GLS equivalent). This is because a GLS lamp doesn't need to increase in size with wattage to generate the light, whereas to generate more light output from a CFL, it requires a larger area of phosphor. A larger area of phosphor means a physically larger lamp. A conventional 100W lamp and a Philips Ecotone 20W lamp providing a similar light output Dimmable CFLs Most CFLs aren't suitable for use in dimmers. If a standard CFL is used with a dimmer switch, it won't fail immediately, but the lamp will fail in a fairly short time 10

11 (probably less than the lifetime of a GLS bulb), and any energy efficiencies will be limited. However, it's possible to buy CFLs which are designed for use in dimmers. Generally, these don't have a built-in starter and ballast, but have separate control gear which they plug into. The four-pin CFLs are the type most usually suitable for use in dimmers. Normally, those with a BC or ES fitment aren't suitable. Where to Buy Them? As the compact fluorescent lamp has become more popular, it has become much easier to buy them. A wide range of different bulbs are available from supermarkets, DIY stores, electrical suppliers, utility companies and via the internet. This is good, but it creates another problem: how to decide which lamp is the best buy. N.B. Although the prices given are those found when writing the article, prices are constantly changing. As part of the preparation for this article, we have investigated the different places where compact fluorescent lamps can be purchased, and compared prices. The tables on the previous page show the 'best buys' that we found at the time of doing the survey (August-October 2004). It's not exhaustive, but it does cover a lot of the places where CFLs can be readily purchased. The tables include several different types of CFL bulbs including 'stick'/spiral, candle, reflector/spot. In the table, the 'best buy' for each expected lifetime is the cheapest bulb we found for that lifetime (in thousands of hours, or years). The 'overall best buy' is the cheapest option if you take into account the total cost of ownership (TCO). For example, a 20W 8000 hour bulb costing 6 is a better buy than a 20W 3000 hour bulb costing 3. 11

12 Hopefully, you have found this article both informative and, as we mentioned in Part 1, shown how to save money from the use of compact fluorescent lamps. Using CFLs, or additional CFLs, offers big savings on your electricity bill, but it's not always obvious which are the best deals. Competition in the marketplace is driving prices down, but you need to be careful of the apparent 'bargains'. Once a product becomes popular, marketing hype takes over and the 'low cost' bargains may also be low life expectancy and therefore not the best buy. The 'best buy' tables we have assembled contain the latest information we have obtained and should be able to help you to get the best value for money when you buy CFLs. Originally, this was going to be the final part of the article on low energy lighting. However, in Part 1 we briefly mentioned the advances in LED technology and have decided to extend the article to a third part to include more information on LEDs, plus other projected advances in low energy lighting. The LED has been in use for decades as a low power light in electrical equipment. In the last few years, much higher power versions have been developed. The potential for this new light source is extensive, offering efficiencies as good as the most efficient sodium lamps and lifetimes in decades rather than years. Barry Jerome, Barry Smith, Chris Walker, This article is part 2 of a series of related articles 12