By P.K.Ranganathan, SECO Controls P. Ltd.
Compact Fluorescent Lamps (CFL) are making a definite, positive impact in the quality of lighting and on the energy footprint, particularly in the residential lighting sector; so much so that they are fast replacing the ubiquitous incandescent lamp.
CFLs consume about 80% less energy than an equivalent incandescent lamp for a given lumen output. In this article we will look at options as available in Compact Fluorescent lamps.
CFLs should be promoted in place of incandescent lamps. There are many types of CFL lamps, each with different construction, but with similar technology. Some are more beneficial to the Energy System than others. CFLs do use mercury in small quantities, and Mercury contamination is a serious health hazard. Used lamp disposal is a very expensive, laborious exercise. Governments, Utilities and NGOs should promote the best option that has the least life-cycle society-energy system cost, for residential lighting.
CFL options in the order of merit:
1. Best: Permanent ballast CFL - 0.95 PF* (12,000 hrs life – 79% reduction in VA demand – 80% reduction in energy). Less mercury is used over time because of extended life. Permanent ballast CFL is more recycling/disposal friendly. Maximum initial cost.
2. Second: Integral ballast CFL with 0.85 PF* (6,000 hrs life – 78% reduction in VA demand – 80% reduction in energy). Helps utilities to get full benefit of changeover from incandescent bulb. Moderately more expensive than Option 3.
3. Third: Integral CFL with 0.50 PF * (6,000 hrs life – 60% reduction in VA demand – 80% reduction in energy). Least initial cost.
* PF-power factor—Power factor determines the ability of the Utility to operate its supply system at maximum efficiency. Ideal PF = 1. Ideally energy and VA demand should be equal.
Currently, CFL options are more efficient than incandescent lamps as they save about 80% on energy. There is a need to standardize and limit CFLs sizes and shapes. We must remember that TFL or tube-lights are more energy efficient than CFLs.
Simultaneously there is a need to establish a proper fluorescent lamp disposal system and contain mercury pollution.
Need for promoting CFLs:
Energy costs are rising. Residential and public service lighting are seen as an obligation of the Government. They provide for the well being of the society. A variety of direct and indirect subsidies are made available to utilities all over the world to meet the power needs of residential and public service lighting.
The public at large sometimes takes the availability of electric energy for granted. They are largely unaware of or indifferent to the problems faced by utilities, in meeting the needs of this segment.
Politicians can be very sensitive to this segment. For most utilities, power supply to this segment is the least profitable and at the same time, the most demanding in terms of service availability. Utility's ability to meet energy needs can be maximized only when energy and VA demand are equal (PF=1).
It is clear that Energy Pricing as a tool for optimization is not an available option. So CFL technology has to be made acceptable to public-at-large by attractively pricing the product. Society, the government, and utilities have a direct stake in this development. The CFL Industry, like any other industry, will be market driven.
As volumes are built, competition will bring down the unit cost of CFLs. Governments should help by lowering/eliminating taxes and duties for this industry. This will ultimately result in reduced subsidies being made available to Utilities presently to meet their obligations for this segment.
CFLs – Technology Evolution
CFLs belong to the family of fluorescent lamps and use the same technology as Tube-lights or Tubular Fluorescent Lamps(TFL) or Linear Fluorescent Lamps, as they are specified. The advent of reliable electronic ballasts and tri-phos coatings revolutionized the lighting industry. Typical modern (T8 and T5) TFLs use a high frequency (20 to 30 KHz) ballast to excite the medium (Mercury) and use phosphor coatings on the inside tube wall to produce visible light. By varying the phosphors, it is possible to produce different color combinations. So typically a fluorescent lamp can be made with CCT ranging from 3000 to 6500 K and CRI greater than 0.8. Today it is possible to get TFLs with life of 20,000 hours or more. Lumen maintenance factor over half-life can be > 90%. Lumens are a measure of the quantity of light emitted by a lamp.
Tubular Fluorescent Lamps (TFLs) are the mainstay of commercial lighting and are also widely used in public service lighting. Modern T5-based tri-phosphor coated TFLs give up to 105 lumens/watt. TFLs are the most energy efficient among the fluorescent lamps.
In any situation where aesthetics and decorative lighting are as important as the lighting level per-se, TFLs are sometimes not preferred. TFL does not merge well with conventional luminaries and light fittings. Residences, Hotels and Restaurants and other such places often call for compact lamps to be used in conjunction with decorative luminaries, so as to produce a pleasant ambiance.
So there was a need to suit fluorescent lamp technology to meet this very large segment. CFLs are the solution. CFLs offer 45 to 60 Lumens/watt depending on their size, shape and quality. They are made in U , 2U, 3U, or spiral designs to make them short, and a compact low cost ballast is added at the base to make it an integral lamp unit. With standard lamp bases to suit existing incandescent lamp sockets, CFLs became a practical alternative to incandescent lamps.
Initially unit costs were very high. As with all commercial technologies, as time and volumes progressed, the products have become better and cheaper.
So today we have CFLs with integrated ballast ranging from 5W to 40W giving an equivalent incandescent lamp rating of 25W to 200W. However, they have 3 intrinsic deficiencies. Because of the cost factor, compact electronic ballast tends to restrict the life of the lamp unit to 6000 hours as compared to the 20,000 hours of T 5 – TFL. Mercury is also a function of the number of tubes, and hence more tubes (2U or 3U), more mercury. So CFL tends to have more mercury than linear lamps or single U lamps. Lastly the intrinsic power factor is very low.
Standard CFLs have a power factor of 0.5. Low power factor reduces ability of the utility system to maximize its resources. By increasing the power factor to 0.85, the full benefit of the reduction in energy savings can be realized by utilities without any additional investment. Otherwise the Utility has to invest in capacitor banks to gain an additional 16% benefit.
Considering this, marrying a T5 - TFL's technology ballast to a CFL tube is a good option. In fact, this technology came first, and only cost considerations have given it a back seat. It is readily available. IESNA standards prescribe a penal loading when universal fittings are used (Lighting load for purposes of conforming is taken at the maximum value of the lamp that can be fitted in the luminary).
CFLs with permanent ballasts can have an extended life of >12,000 hours compared to 6,000 hours of standard integral CFLs. Since the ballast and lamp are separate, they are more amenable for recycling/safe disposal.
Mercury contamination assumes importance as the world starts changing over to CFLs in a very big way. These lamps are going to be used about just anywhere and it is difficult and expensive to establish and maintain a good collection and disposal system.
Lamp caps can be readily recycled, but recycling glass/phospor/mercury waste is a very expensive process presently. Only laboratory grade systems are available. As on date, TFLs' and SFLs' disposal is by shredding, packing, and dumping is select approved landfills.
So it becomes necessary to look at options to reduce the total usage of mercury, adopting a life-cycle concept. See table 1 for Basis – lamps – parameters
See table 2 for a comparison of 3 types of CFL performance.
60 W and 100 W incandescent lamps have been chosen because they form the bulk of residential lighting. Percentages will remain more or less the same for 40W bulb also.
It can be seen that improving the PF to 0.85 from 0.50 results in further reduction in VA demand to 76% from 60%. This will be of immense benefit to utilities, other things being equal.
Way Forward - Suggestion
Integral CFLs have a role to play in residences, hotels and restaurants and other such places where aesthetics play an important role. Applications will be to replace existing incandescent lamps in the range of 25W to 100W. There is a good case for standardizing and restricting the manufacture and marketing of CFLs to the following sizes only: 5W, 8W, 12W and 20W. This will meet practically all the requirements for this sector.
A common permanent ballast can serve 5W and 8W bulbs. Similarly, a common ballast can serve 12W and 20W CFLs. Beyond 20W, only linear FL should be allowed. Eventually, standardized prices of permanent ballasts will start falling, and will become economical in due course.
To reduce mercury levels, only U, 2U and spiral designs should be allowed. 3U and 4U constructions should be banned.
Lamp manufacturers should be offered incentives for changeover and disincentives for persisting with earlier models. A planned phase out scheme can be worked out.
In this manner all the stakeholders, individuals, lamp manufacturers, utilities and the environment will benefit.
Integral CFLs with 0.5 PF offer a practical, economical, energy efficient alternative to incandescent lamps. To attain the full benefit of the reduction in energy consumption, utilities have to invest in additional capacitor banks and improve PF to 0.95. This can be mitigated to a large extent by the use of CFL with 0.85 PF.
However the promotion of the use of permanent ballast CFLs is most beneficial. This can reduce mercury pollution (50%) and reduce energy/ VA demand by 80%, thus rendering maximum benefit to the utility, society, and the environment. Permanent ballast CFLs offer better recycling/disposal opportunities.
1. Published brochures of Philips / GE / Osram lamp manufacturers.
4. US Department of Energy web-site
Mr.P.K.Ranganathan is a Director, of SECO Controls P. Ltd. He leads the Energy Services Division, and is a Certified Energy Auditor with more than 12 years of experience in Energy Efficiency studies. He graduated in Electrical Engineering, from IIT Madras and has a Post Graduate Diploma in Management. He has designed and executed large captive Power plants, providing standby Power, to many leading Industrial Organizations. He has introduced many new products in the Utility Sector, for protection and control of HV & EHV – Electrical Power Switchgear. He is a life member of the Institution of Engineers and the Institution of Plant Engineers.