Technical Report - Intensity Distribution and Light Output Ratio
- 1. 1 | P a g e Year 2 Block 5 By Martin Jesson Intensity Distribution and Light Output Ratio (LOR) Abstract Replacement. Equivalent. Energy saving – these are key terms used in the marketing and branding of lamps. The fallacy is that while yes, a given lamp may use less watts and have the same lamp holder, the lamp is only one piece in a two piece puzzle. Overall efficiency is determined by light output of a luminaire, not solely by the type of lamp used. This Report will conduct a basic photometric test of 4 common lamps and compare their light out ratio. Is a CFL more ‘efficient’ than a 100 GLS?
- 2. 2 | P a g e Introduction Light Output Ratio Light Output Ratio (LOR) is essentially the efficiency of a luminaire expressed as a percentage. It’s a measure of how well the luminaire distributes the lumens of its light source. This being derived from the sum of the total lumens of the lamp and the actual measured lumens distributed out of the fitting. These two factors can be further surmised to: • Constant – If maintained, the luminaire will have a permanent level of efficiency as dictated by its design, materials used and thermal dynamics. • Variable – The lamp, any number of different lamps could be substituted into the luminaire which would make its published LOR void. If published photometric data is to be used then it is imperative the listed lamp is also used. Intensity Distribution Intensity Distribution is how a given combination of luminaire and lamp ‘delivers’ light and is often referred to as measurements of ‘Delivered Lumens’. This information is typically conveyed in a polar curve diagram which shows the intensity of the light at any given angle. The sum of intensity values outlined in the polar diagram are used to determine the LOR of the luminaire. The lamp can prove an obstruction to light output. If the lamp ‘Centre’ dimension is changed the reflector will not be optimized . This luminaire is designed to take an 18W PL lamp. Note how the CFL is positioned horizontally.
- 3. 3 | P a g e We can see from this graphic that 100% of the distributed light is thrown downward. Therefore we can determine LOR =DLOR (D =Down). Luminaires can be designed to have an indirect light component in which a percentage of light is cast upwards. LOR of such designation is therefore split to show an DLOR & ULOR. This picture is a graphic illustration of how the polar curve is derived for luminous flux. You can see here how the light is almost at 80deg to the vertical. Note how this distribution is only on one axis. Photometric testing is conducted over many axis in order to get comprehensive information. This Figure is a Photometric illustration of the Dot122 as published by Dot and imported into AGi32 Design software. Note the many planes that are used to give a comprehensive 360deg representation of the distribution of the luminaire. This published photometric data represents a symmetrical circular distribution pattern This published photometric data lists a 100W GLS as the lamp and represents a symmetrical circular distribution pattern with an LOR of 65.2%. Or in other words, the luminaire will deliver 65.2% of the lumens of the 100W GLS. This luminaire is designed to incorporate a 100W GLS lamp and its LOR is only 65.2%. This would not seem very efficient design. The real question is, will other technologies be more efficient? Does an equal lamp lumen output and lower wattage translate into energy efficient? The following experiment will compare 4 typical lamps types LOR to find the highest achiever.
- 4. 4 | P a g e Method Apparatus: • Dot 122 Downlight luminaire • Lamps o Philips Tornado 20W CFL o Philips 100W Softone o Philips 70W Halogen o Sylvania 100W (clear) • Chroma Electricity Supply – Set to 240v ~ 50hz • Illuminance meter – Hagner ECI • Turntable with measurable units of degrees of rotation • Results table Procedure: 1) The Equipment was set up as per figure 1. 2) The Chroma Electricity supply was set to 230v AC 50Hz 3) Inserted CFL lamp into downlight and was turned on 1hr prior to experiment to allow for suitable run in/warm up time. 4) Turn on Illuminance meter and ensure aiming is at Zero degrees. 5) Ensure downlight at zero degrees 6) Take Illuminance measurement and record in results table. 7) Downlight was then rotated left to specified angle outlined in results table and measurement recorded 8) Repeat step 5 until at 90 degrees. 9) Repeat step 6 rotating in direction = Right 10) Repeat steps 5-9 for all 3 remaining lamps. Figure 1
- 5. 5 | P a g e Results Intensity found by: I=E.D² where E = measured Illuminance & D = 1.5m 20W Philips Tornado CFL Angle θ Distance (M) Right Illuminance Left Illuminance Mean Intensity (cd) E (lx) I (cd) E (lx) I (cd) 0 1.5 163.000 366.750 163.000 366.75 366.75 10 1.5 163.000 366.750 163.000 366.75 366.75 20 1.5 161.000 362.250 158.000 355.5 358.875 30 1.5 151.000 339.750 143.000 321.75 330.75 40 1.5 120.000 270.000 115.000 258.75 264.375 50 1.5 89.000 200.250 78.000 175.5 187.875 60 1.5 44.000 99.000 36.000 81 90 70 1.5 12.000 27.000 8.000 18 22.5 80 1.5 1.700 3.825 1.100 2.475 3.15 90 1.5 0.000 0.000 0.000 0 0 100W Philips Softone Incandescent Lamp Angle θ Distance (M) Right Illuminance Left Illuminance Mean Intensity (cd) E (lx) I (cd) E (lx) I (cd) 0 1.5 192.000 432.000 192.000 432 432 10 1.5 183.000 411.750 183.000 411.75 411.75 20 1.5 163.000 366.750 166.000 373.5 370.125 30 1.5 131.000 294.750 134.000 301.5 298.125 40 1.5 87.000 195.750 85.000 191.25 193.5 50 1.5 40.000 90.000 39.000 87.75 88.875 60 1.5 13.000 29.250 12.000 27 28.125 70 1.5 4.300 9.675 3.600 8.1 8.8875 80 1.5 0.800 1.800 0.700 1.575 1.6875 90 1.5 0.100 0.225 0.100 0.225 0.225 70W Philips Halogen Energy Saver Incandescent Lamp (Pearl) Angle θ Distance (M) Right Illuminance Left Illuminance Mean Intensity (cd) E (lx) I (cd) E (lx) I (cd) 0 1.5 202.000 454.500 201.000 452.25 453.375 10 1.5 192.000 432.000 188.000 423 427.5 20 1.5 164.000 369.000 158.000 355.5 362.25 30 1.5 127.000 285.750 123.000 276.75 281.25 40 1.5 83.000 186.750 81.000 182.25 184.5 50 1.5 34.000 76.500 32.000 72 74.25 60 1.5 10.000 22.500 10.000 22.5 22.5 70 1.5 3.000 6.750 3.100 6.975 6.8625 80 1.5 0.800 1.800 0.700 1.575 1.6875 90 1.5 0.000 0.000 0.000 0 0
- 6. 6 | P a g e 100W Sylvania Double Life Incandescent Lamp Angle θ Distance (M) Right Illuminance Left Illuminance Mean Intensity (cd) E (lx) I (cd) E (lx) I (cd) 0 1.5 247.000 555.750 247.000 555.75 555.75 10 1.5 219.000 492.750 251.000 564.75 528.75 20 1.5 187.000 420.750 220.000 495 457.875 30 1.5 145.000 326.250 167.000 375.75 351 40 1.5 101.000 227.250 118.000 265.5 246.375 50 1.5 28.000 63.000 32.000 72 67.5 60 1.5 9.000 20.250 10.200 22.95 21.6 70 1.5 3.500 7.875 3.400 7.65 7.7625 80 1.5 0.900 2.025 0.700 1.575 1.8 90 1.5 0.000 0.000 0.000 0 0 Zonal Flux Calculations: Mid Zone intensity found by: cd Zonal Flux found by: = Mid Zone Intensity x Zone Factor Lamp Type Zone Mid Zone Intensity (cd) Zone factor Zonal Flux (lm) 20W Philips CFL 0 - 10 366.750 0.095 34.841 10 - 20 362.813 0.283 102.676 20 - 30 344.813 0.463 159.648 30 - 40 297.563 0.628 186.869 40 - 50 226.125 0.774 175.021 50 - 60 138.938 0.897 124.627 60 - 70 56.250 0.993 55.856 70 - 80 12.825 1.058 13.569 80 - 90 1.575 0.091 0.143 Total Zonal Lumens 853.251 100W Philips Softone 0 - 10 421.875 0.095 40.078 10 - 20 390.938 0.283 110.635 20 - 30 334.125 0.463 154.700
- 7. 7 | P a g e 30 - 40 245.813 0.628 154.370 40 - 50 141.188 0.774 109.279 50 - 60 58.500 0.897 52.475 60 - 70 18.506 0.993 18.377 70 - 80 5.288 1.058 5.594 80 - 90 0.956 0.091 0.087 Total Zonal Lumens 645.595 70W Philips Halogen (Pearl) 0 - 10 440.438 0.095 41.842 10 - 20 394.875 0.283 111.750 20 - 30 321.750 0.463 148.970 30 - 40 232.875 0.628 146.246 40 - 50 129.375 0.774 100.136 50 - 60 48.375 0.897 43.392 60 - 70 14.681 0.993 14.578 70 - 80 4.275 1.058 4.523 80 - 90 0.844 0.091 0.077 Total Zonal Lumens 611.514 100W Sylvania (Clear) 0 - 10 542.250 0.095 51.514 10 - 20 493.313 0.283 139.607 20 - 30 404.438 0.463 187.255 30 - 40 298.688 0.628 187.576 40 - 50 156.938 0.774 121.470 50 - 60 44.550 0.897 39.961 60 - 70 14.681 0.993 14.578 70 - 80 4.781 1.058 5.059 80 - 90 0.900 0.091 0.082 Total Zonal Lumens 747.101 Light Output Ratio: Lamp Rated Flux (lm @ 240V) Total Zonal Flux DLOR ULOR LOR 20W Philips CFL 1350 853.251 0.632 0.000 0.632 100W Philips Softone 1200 645.595 0.538 0.000 0.538 70W Philips Halogen (Pearl) 1200 611.514 0.510 0.000 0.510 100W Sylvania (Clear) 1340 747.101 0.558 0.000 0.558
- 8. 8 | P a g e Discussion Limitations: On the whole, the data does not replicate that published by Dot. We must acknowledge the limitations of the experiment in order to explain this. Firstly, we are only measuring intensity of one plane. This presents a problem because if you look closely at our lamps filaments, they are not symmetrical. The Filament is long and skinny, essentially the end of the filament is closer to the reflector then the middle, which creates two different points of distribution which cannot be equal. This is further identifiable by analysing the ‘left’ and ‘right’ illuminance readings, we can see they differ. Lamp positioning within the luminaire is also an inaccuracy which must be taken heed of. This luminaire is orientated on a horizontal plane which may cause the lamp to be positioned off centre. The lamps were not burnt into their 100hr threshold, and they are subject to manufacturing tolerances, so the rated flux may be at the extreme of the ± parameters. The experiment was not conducted at 25°C controlled temperature. Analysis of Results: If we look at the below polar curve published by Nimbus lighting for the DOT122 downlight as used in this experiment. We can clearly ascertain the intensity at a given angle. It can be determined that maximum intensity values will be at angles 20deg from the vertical. We can also determine the beam angle of 90deg. Predominantly downlights designed for CFL lamps incorporate ‘PL’ lamps which are compact tubes arranged in a longer format which better suits fluorescent technology. Refer ‘CFL Downlight’ diagram in the introduction. This luminaire has larger CFL lamps which are more efficient and uses them horizontally in order to negate any potential for glare nuisance. If we now look at the Philips 100W soft tone and the 70W Halogen. Both have rated output of 1200lm but the halogen consumes 30% power. For the Dot122 luminaire we can see that the halogen doesn’t do as greater job distributing its lumens as the 100W with an LOR of 51% - 2% less If we refer to the CFL Illuminance data we notice that the values are markedly increased at the larger angles. For example at 50,60,70deg the CFL has more than double the output of the other incandescent lamps. This would translate to a wider beam angle then the published data. The Sylvania 100W GLS and the CFL have similar outputs of 1340 and 1350 respectively, yet the Sylvania had 8% less LOR. Reasons for this is because physically the CFL is longer and wider which enables more light to be distributed without the aid of the reflector. Essentially, the in-efficiency of the reflector doesn’t feature as its not used. Whilst the CFL may deliver more lumens, a glare issue may also present itself.
- 9. 9 | P a g e than the 100W. From this analysis it can be determined that the Halogen would be an energy efficient option over the 100W Softone as although it has a 2% reduction in light output, it does have 30% energy saving. Conclusion: Despite its limitations, this experiment does highlight the variable nature of the output due to the physical nature of the lamps. The small compact design of the Dot122 means the lamp poses a hindrance to the light output which probably accounts for the relatively low LOR of all 4 lamps. By measuring only one plane of distribution the asymmetrical characteristics of the lamps were amplified. This was especially visible in the CFL which had a larger beam angle then the incandescent samples. This can only be attributed to its larger size and would most likely have a greater potential to present a glare of all the lamps tested. Which leads to a compromise of energy savings over comfort which I believe is the greatest issue facing todays lighting designer. The balance of comfort and cost.
- 10. 10 | P a g e References Illuminating Engineering Society of North America (1993) Lighting Handbook, 8th Edition, Warren G Julian (2011, February). Lighting: Basic Concepts, 6th Edition, http://archive.luxmagazine.co.uk/2011/07/all-led-downlights-are-100-efficient/ http://www.emmlight.com/producten/thorn-led-downlights/ http://www.pge.com/myhome/edusafety/workshopstraining/pec/tour/light5.shtml http://www.dotdownlights.com/