Energy Assessment: Over-accounting

1 to 30 of 47

- CommentAuthortony
- CommentTimeMar 21st 2011
There has been a very rapid rise in the use of low energy lighting luminaries in the last few years. At first sight it would appear that as a consequence large amounts of energy are being saved. However if we look a little more closely we quickly realise that that this might not be the case.
In a heated building at a particular point in time the amount of energy required to keep a room at its design temperature is fixed. For the sake of argument let us say that the room in question needs 500W to keep it warm. This energy is supplied by a radiator that emits 400W and a 100W light bulb. Now someone fits a low energy light bulb which only needs to use 20W to light the room to the same level as the old incandescent one did. The problem now is that the room has only got 420W of energy going into it but its heat loss is 500W so it will be colder. In order for us to maintain the temperature at the same level as before we must now supply 480W through the radiator. Thus no energy has been saved.

400W + 100W = 480W + 20W

The uptake and increase in the use of low energy light bulbs is being used by central government as way of meeting our carbon reduction targets YET NO ENERGY IS BEING SAVED!
Many reports on energy use in buildings are assuming quite incorrectly that energy and costs are being saved in the winter, whereas, no energy is being saved although some costs might be depending on the relative costs of the different energy sources used. In the summer there will be a cost saving but lighting is used less as it is lighter for later into the evening and light early in the mornings. In this way 80% of the savings being claimed are not being made in the real world.

I call this over-accounting.
- CommentAuthorsune
- CommentTimeMar 21st 2011
Hi Tony - I'm not anti what you say here but just thought: aren't most lights usually near the ceiling? - ie not the best spot to site a tiny radiator?
- CommentAuthorpmusgrove
- CommentTimeMar 21st 2011
What about lighting in the summer when we don't need to heat our homes (if the insulation and thermal capacity are balanced). No need then for that lighting heat?
- CommentAuthorDamonHD
- CommentTimeMar 21st 2011 edited
Tony: you keep raising this old canard as if repeating it will change the laws of thermodynamics.

If you want to heat with high-grade energy such as electricity, use a heat-pump, not the waste heat from what Edison used to call 'lighting'.

Or use lower-grade energy such as heat from burning relatively-clean fossil fuels such as natural gas.

Rgds

Damon
- CommentAuthorjoe90
- CommentTimeMar 21st 2011
Tony, I am with you mate, I have used this argument many times and untill a decent low energy lamp at a decent price is sold I am not changing "some" of mine, however I dont mind using CLF's in places that require lamps on for a long time and you dont mind the bad quality of the light. I think LED's will come on a long way and eventualy give us a good replacement.
- CommentAuthornigel
- CommentTimeMar 21st 2011
A kWh of peak rate useful electricity emits 0.41kg of Co2
A kWh of useful gas heat emits 0.22kg when using a modern gas condensing boiler.

The same applies to the cost, it costs more for a kWh of electricity than a kWh of gas.

So whilst you are correct in terms of energy you are not correct in terms of carbon emissions.
There is also the issue of having unwanted heat from lighting in the non heating months.

Therefore low energy lighting is unequivocally beneficial financially and environmentally.

The bad quality of the light is a typical excuse but in fact low energy lights are available in many colour frequencies to suit most requirements.
- CommentAuthorSteamyTea
- CommentTimeMar 21st 2011
Posted By: DamonHDTony: you keep raising this old canard as if repeating it will change the laws of thermodynamics.

Sing along now

The First Law of Thermodymamics:
Heat is work and work is heat
Very good!

The Second Law of Thermodymamics:
Heat cannot of itself pass from one body to a hotter body
Heat won't pass from a cooler to a hotter
You can try it if you like but you far better notter
'Cos the cold in the cooler with get hotter as a ruler
'Cos the hotter body's heat will pass to the cooler

First Law:
Heat is work and work is heat and work is heat and heat is work
Heat will pass by conduction
Heat will pass by convection
Heat will pass by radiation
And that's a physical law
Heat is work and work's a curse
And all the heat in the Universe
Is gonna cooool down 'cos it can't increase
Then there'll be no more work and there'll be perfect peace
Really?
Yeah - that's entropy, man!

And all because of the Second Law of Thermodynamics, which lays down:
That you can't pass heat from the cooler to the hotter
Try it if you like but you far better notter
'Cos the cold in the cooler will get hotter as a ruler
'Cos the hotter body's heat will pass to the cooler
Oh, you can't pass heat from the cooler to the hotter
You can try it if you like but you'll only look a fooler
'Cos the cold in the cooler will get hotter as a ruler
That's a physical Law!

Oh, I'm hot!
Hot? That's because you've been working!

Oh, Beatles - nothing!
That's the First and Second Laws of Thermodynamics!"
- CommentAuthorjoe90
- CommentTimeMar 21st 2011
Nigel,

"The bad quality of the light is a typical excuse but in fact low energy lights are available in many colour frequencies to suit most requirements."

It is not an excuse, it is a reason because I have not found an low energy lamp that gives the same quality of light that I like. Please suggest a low energy lamp that I can try to replace a 60watt incandescent that gives the same colour balance and I will try it and report back here.
- CommentAuthornigel
- CommentTimeMar 21st 2011
Incandescent lights have a colour temperature of 2700k to 3300k.

There are numerous bulbs available in this colour temperature often termed warm white or soft white but always check the colour temperature.
- CommentAuthorjoe90
- CommentTimeMar 21st 2011
Nigel,

I would still like you to recommend one please!
- CommentAuthornigel
- CommentTimeMar 21st 2011
try a philips softone about Â£7 each.
- CommentAuthornigel
- CommentTimeMar 21st 2011
actually Â£3.99 from argos - bargain
- CommentAuthortony
- CommentTimeMar 21st 2011
Nigel -- I like you answer the best

you said, "So whilst you are correct in terms of energy you are not correct in terms of carbon emissions."

so in energy terms you agree yet you say in environmental terms it is all good :-

400W of gas = 88 g of carbon plus 100W electricity = 41g >> 129g of carbon

480W of gas = 105.6g plus 20W electricity = 8.2g >> 113.8g of carbon

difference is 12% yet HMG is claiming 100% of the 80W saved and this is what winds me up as it is untrue.

Not all the energy that is being saved by using low energy light bulbs is being saved nor is all the carbon only a proportion of it is

Yet this 100% is being used to meet our carbon targets -- OVER- ACCOUNTING in my book
- CommentAuthorseanie
- CommentTimeMar 22nd 2011
You should only incorporate the replacement heating in the calculation.
- CommentAuthorjms452
- CommentTimeMar 22nd 2011
Tony - you keep raising this exact same point.

When we loose the will to keep pointing out what you are saying is only partly correct that won't make it undesputed fact...
- CommentAuthorPaul in Montreal
- CommentTimeMar 22nd 2011
Where I live (electricity 99% hydro) low-energy lights increase carbon emissions in winter in all houses that heat by gas or oil. The only saving is for outside lights or lighting used outside of the heating season. However, in summer, I'm outside enjoying the warm weather rather than sitting inside with the lights on. In the case where people heat with heat pumps, then there is a marginal saving in electricity by switching to low energy lights, but no difference in carbon emissions (as there aren't any in the first place).

Paul in HydroElectric Montreal.
- CommentAuthortony
- CommentTimeMar 22nd 2011
OK then guys so are you saying to me that HMG is correct to claim that all of the 80W saved by using low energy bulbs can be multiplied by the number sold and their average use and then that figure turned int carbon saved and deducted from the target set?

I do not agree and this is why I am on the case of over-accounting.
- CommentAuthorevan
- CommentTimeMar 22nd 2011
If a house has effective enough heating to compensate for the difference of 80W worth of incandescent lighting, it's probably also the type of house which has air conditioning.

So the chances are, it all cancels out.
- CommentAuthorjoe90
- CommentTimeMar 22nd 2011
Nigel,

Thanks for the recommendation, have looked at the argos website and indeed a bargain at Â£3.99 but I notice that quite a few people give the bulbs a poor rating for longer than standard CFL startup time and some say not bright enough. I will however buy some and give them a go.
- CommentAuthordimengineer
- CommentTimeMar 22nd 2011
<blockquote><cite>Posted By: SteamyTea</cite><blockquote><cite>Posted By: DamonHD</cite>Tony: you keep raising this old canard as if repeating it will change the laws of thermodynamics.
</blockquote>

Sing along now

The First Law of Thermodymamics:
Heat is work and work is heat
Very good!

The Second Law of Thermodymamics:
Heat cannot of itself pass from one body to a hotter body
Heat won't pass from a cooler to a hotter
You can try it if you like but you far better notter
'Cos the cold in the cooler with get hotter as a ruler
'Cos the hotter body's heat will pass to the cooler

First Law:
Heat is work and work is heat and work is heat and heat is work
Heat will pass by conduction
Heat will pass by convection
Heat will pass by radiation
And that's a physical law
Heat is work and work's a curse
And all the heat in the Universe
Is gonna cooool down 'cos it can't increase
Then there'll be no more work and there'll be perfect peace
Really?
Yeah - that's entropy, man!

And all because of the Second Law of Thermodynamics, which lays down:
That you can't pass heat from the cooler to the hotter
Try it if you like but you far better notter
'Cos the cold in the cooler will get hotter as a ruler
'Cos the hotter body's heat will pass to the cooler
Oh, you can't pass heat from the cooler to the hotter
You can try it if you like but you'll only look a fooler
'Cos the cold in the cooler will get hotter as a ruler
That's a physical Law!

Oh, I'm hot!
Hot? That's because you've been working!

Oh, Beatles - nothing!
That's the First and Second Laws of Thermodynamics!"</blockquote>

Flanders & Swann - marvellous!! I was brought up on this, and now my children are too
- CommentAuthorseanie
- CommentTimeMar 22nd 2011
A lot of the carbon calculators and figures for estimated savings (financial and CO2) do take the heat replacement effect into account.
- CommentAuthorSteamyTea
- CommentTimeMar 22nd 2011
Posted By: dimengineer 'Flanders & Swann - marvellous!! I was brought up on this, and now my children are too'

Do they chuckle at this too?
http://www.youtube.com/watch?v=b3cc9rXB27o
- CommentAuthortony
- CommentTimeMar 22nd 2011
seanie -- show me these please
- CommentAuthorseanie
- CommentTimeMar 22nd 2011
http://efficient-products.defra.gov.uk/spm/download/document/id/579

http://efficient-products.defra.gov.uk/spm/download/document/id/605

http://www.energysavingtrust.org.uk/Energy-saving-assumptions

"Where appropriate, adjustments to account for the Heat Replacement Effect have been made in our calculations. For instance, our lighting, appliances and standby savings incorporate reductions to the savings to account for the potential increase in space heating that may be required when more energy efficient products are installed. These heat replacement effect factors have recently been revised by Defra (March 2010), which has led to a small change in many of our lighting and appliance savings this year."
- CommentAuthorseanie
- CommentTimeMar 22nd 2011
And I've come across it elsewhere. It's a well known factor even if there's uncertainty about the extent of the effect.
- CommentAuthorseanie
- CommentTimeMar 22nd 2011
From the BRE;

"Energy efficient lighting is cost-effective and offers the potential for a significant carbon
saving, even taking into account the heat replacement effect."

http://projects.bre.co.uk/PDF_files/ReducingCarbonEmissionsHousingv3.pdf
- CommentAuthorCWatters
- CommentTimeMar 22nd 2011
Posted By: nigelIncandescent lights have a colour temperature of 2700k to 3300k.

There are numerous bulbs available in this colour temperature often termed warm white or soft white but always check the colour temperature.

What I don't quite understand is this table...
http://www.efi.org/factoids/cri.html
It says warm white CFL have a worse CRI than cool white. Yet many people seem to prefer warm white?

The philips softone has a CRI around 80 I think.
- CommentAuthorseanie
- CommentTimeMar 22nd 2011 edited
Defra's revised heat replacement factor seems to be 21% for lighting.

Using that, what would be the outcome of replacing a 100w bulb used 1000hrs/yr?

100 kWh equates to about 54kg of CO2, and about Â£12 in cost.

Replace that with a 20w bulb and that'll be 11kg of CO2 and about Â£2.40 in cost.

Add to that 21kWh of gas and that'll be about 4kg of CO2 and about 84p in cost.

So the energy saving is about 59%, the CO2 saving about 72%, and the cost saving about 73%.

Of course there are lots of things that can effect that, but for your typical house low energy bulbs do seem to make sense.
- CommentAuthortony
- CommentTimeMar 22nd 2011
Sounds like over-accounting to me still

21% sounds like a very low figure for heat replacement compared to the 80% I am suggesting
- CommentAuthorseanie
- CommentTimeMar 22nd 2011
Where did you suggest an 80% figure?

And what did you base it on?

1 to 30 of 47



	Site Map \| Home \| View Cart \| Pressroom \| Business \| Links	Contact Us
Logout
© Green Building Press

Green Building Forum

Categories

Feeds

Energy Assessment: Over-accounting