Tilley lamp energy efficiency

Hi all

I have been doing a few sums to try to calculate the amount of energy a 300CP Tilley stormlight uses, and how much light it puts out.

A typical '300 candle power' Tilley lamp uses 1.25 pints of paraffin for 10 hours burning, equivalent to approximately 700 watts of heat input. For this, you get a lamp brightness equivalent (in my own estimation) to a 75 watt tungsten bulb. Tungsten bulbs emit around 5% of the energy input as light, and 95% as heat. So, to emit just under 4 watts of light, our classic pressure lamp is consuming 700 watts of power, delivering 0.42 candlepower per watt, at an overall efficiency of just 0.6%!

This is a big improvement on the candle, of course, which emits one candlepower for around 80 watts of input, thus delivering a mere 0.0125 candlepower per watt at an overall efficiency of 0.017%. I won't go into carbon emissions...

Any thoughts, anyone?

 

Hello Phil, those are interesting technical points, but I like the white light from a pressure lamp, I find that electric light always has a yellow tinge to it.

Also, a pressure lamp gives off a fair amount of heat, so that's heat and lght, which is very practical and in my opinion very homely, Jeff.

 

Hmm, I don't think a candle gives out one candlepower any more than a horse gives out one horsepower.

Tilley's 300cp is actually a 'claimed' 300cp and in common with most (not all) manufacturers, is something of an exaggeration. They have been measured, scientifically, at around 180 actual candlepower, although the real figure will vary with all sorts of factors.

I think, in reality, it's not worth exercising too much, or indeed, any brainpower with this kind of exercise, particularly if there are no accurate scientific measuring devices available - the SHE (standard human eyeball) is useless at measuring light output. 8)

Ask yourself, is my lantern producing sufficient usable light for my needs? If it is, fine; if it isn't, light another one!

 

David,

I don't agree with this. You can measure the light output, you can measure the amount of heat produced, you can measure the amount of fuel used in producing both: light and heat.

I can't and most of us can't but the apparatus exist. If you want to know this all is a complete different chapter.

 

Wim, I was a science teacher for almost twenty-five years and I hold a further degree in a scientific subject as well as being a member of a professional scientific society within which I have Chartered status. I'm perfectly aware what kinds of scientific measuring instruments are available. But thank you for reminding me what's possible in the world of modern science...

The bit I was referring to was this:-

- my emphasis.

 

Oh, I am verry sorry your highness.

 

Well, whatever you say Wim, and with the greatest of respect to Phil, the fact remains that without reliable scientific data going into the equations, nothing meaningful is ever going to come out of them.

And as I indicated above, my opinion on this kind of thing is that the figures don't matter a tinker's cuss. What is important is whether the amount of useable light given out by your lamp(s) in any given situation meets your needs. That's it - as simple as that...

 

Neil's light measuring apparatus is always popular at Newark but for me it's just for light-hearted bragging rights or more usually shame.

IMO light output is like boiling times with stoves. If it's bright enough or fast enough that fine.

BTW - you're reet clever you David.

 

Exactly - that's it in a nutshell...

 

A bit like Sloe Gin testing then? Gets better as the evening goes on. Happy dreams - Steve.

 

Complicated game this. My light meter does measure accurately enough but perhaps the results are not important. Useful light is of course and that is more important than just how efficient a lamp can be. Tilley did make a burner which gave an actuall 300cp. I have measeured one new in box early 1950s X246 and got 285 Cp. That is close enough for me to conclude that at least up to the 1950s the claim was not an exagerated boast but simply the truth. Knowing that can make a measurement of some interest on older lamps because you can see how much the passage of time has reduced the efficiency of the burner.

I made up the light meter because I wanted to know what my lamps were actually doing. The results can be interesting but that instrument almost never gets used now except at Newark. It is accurate but really it is only used now for the entertainment value. ::Neil::

 

Stare into the mantle for a minute and you will think you own the brightest lamp in the world! DanL

 

... Then close your eyes and count the red and blue and green dots you see, the more they are the brighter the lamp is

 

Well I didn't want to stir up a hornet's nest with my first posting on this Forum, but I did entitle the thread "energy efficiency" not "light output", and as a Chartered Engineer and Chartered Environmentalist myself I am interested in the development and history of lighting, and the efficiency of conversion of chemical energy into heat and light.

The principle of the paraffin vapour lamp (and the blowlamp, Primus stove etc) is particularly fascinating to me, and I have a small but growing collection of restored devices. I noticed that the brightest by far is my X246. It's brighter than my X246A and two X246Bs. It also emits a lot more heat, so much that holding the lamp by its handle whilst burning gets very uncomfortable! By contrast, the X246A and B are OK to hold.

I wonder if this is the reason Tilley possibly downrated the later models? I'm not saying they don't give a good light, they certainly do, and my eyes tell me that they are about as bright as a 75 watt bulb. I also agree that the colour temperature and heat output makes them eminently suitable and user-friendly for camping trips.

For what it's worth, Camping Gaz lanterns have been sold as "80 watt" equivalents for some time.

This nominal 300CP rating may be a convenient balance between light output, heat emission and fuel consumption. Anyway, in the interests of research and furthering my knowledge, a vintage Avo lightmeter is on its way...

Thanks for everyone's comments!

 

Phil... any update with this thread? I watched with interest when it was 'fresh' - what did your light-meter reveal?

 

Has the energy required to pump it up been taken into account here?..

I find with these calculations it's quite often the human effort that gets ignored

 

Hi both and thanks for your interest.

Sadly, Jim, I was 'sniped' at the last minute and my purchase of a light meter fell through, although I have been offered one to borrow at some future date.

Nothing much has changed regarding my assessment of energy efficiency. As you noticed, Gneiss, I have ignored the pumping energy because it is insignificantly small compared with the chemical and heat energy involved in the fuel combustion process. However, my collection of X246s has grown since I started this thread, and I have noticed considerable variation in light output between the lamps I have restored. They are all good and bright, but I now have a chrome-plated X246B that is near-as-dammit as bright as the old Guardsman.

I suspect the mantle itself, and the condition of the burner, are responsible for a good deal of the variations seen.

I want to try polishing the internal passages within the burner to see whether gas-flow and reduced turbulence can create improvements in light output. I am also working on a 500CP version of the X250B, and await a delivery of Tilley 500CP mantles. However, the light output will always remain a tiny proportion of the total energy consumed by a Tilley lamp, and as this is moving away from 'energy efficiency' into 'light output', I think I will post these results in another thread.

Best regards,

Phil

 

LUX meter : ebay 220674770459

 

Thanks, Wim, but in keeping with my vintage techology interests I am looking for something more along the lines of an Avo analogue light meter like this one, calibrated in foot-candles: 251163994619

Kind regards,

Phil

 

Ah but there is a problem with an old Foot candle meter. To read CP direct the detector has to be 1 foot from the light. That means it is near impossible to filter out the ambient light. It will give you decent comparisons of course but it can never be accurate unless you can be sure to elliminate all the reflections and other light contaminations. The Lux meter we use does allow for a long enough baffled tube to be used to eiliminate reflected and ambient light and therefore it will always tend to be more accurate. Another problem is with a shorter reading length any slight variations in distance mean a more exagerated variation in the perceived CP than with the lux meter. Some years ago Fil Graff and I used both Ft/candle and lux meters on the same light source and found the ft/c meter was less reliable so we abandoned it in favour of the more accurate instrument or rather the instrument that was better suited to our purpose of making a photometer that was not influenced by ambient light and could be used in daylight and still give an accurate reading. ::Neil::

 

Hi Neil, thanks for all the advice Yes, I realise that I will only be able to make comparative measurements, but that's all I really want to do anyway.

I've arranged to borrow a meter next Monday so will have a play later next week.

Phil

 

This should get you all going,in my opinion, a 246B shines at about magnitude -10!

 

nice one John!

 

The same as comet Ikeya Seki, then!

 

Somewhat dimmer than Old Man Sol at -26.

 

A vintage Avo foot-candle meter is now on its way to me, and test results will be posted in due course.

Phil

 

That is sort of where I started. I used an old photo light meter which did not read direct to cp but did enable comparisons. Handy for a while but then I got increasingly irritated with not having an accurate measure so ended up spending a deal of cash on the Lux meter.

I am sure you will be having trouble believing your results though because in general these lamps just don't work near where the advertised power.
::Neil::

 

I'm sure you're right. I didn't pay much for the FC meter anyway, so it will just be an interesting experiment!

 

Well said!

 

This is a very old thread.
From the Wikipedia,: Luminous efficacy - Wikipedia ,
it looks like gas mantles have miserably low overall luminuous efficacies around 1-2 lumens per Watt and overall luminuous efficiencies around 0.15-0.3%.