Gas Calorific Value

lindabea

I have recently switched to Scottish Hydro Electric (SHE) from British Gas. When I received my first bill, I was surprised to see that SHE are using a calorific value of 39.5897 when converting my meter units to BTHU. British gas have always used 39.1 in all the years we been with them. When I called SHE yesterday to discuss this issue, I did not feel that they gave me a satisfactory explanation why this difference which of course, is inflating the number of BTHU - hence a bigger bill!!! They told me that the calorific value is based on a figure set by Tranco and the government which changes depending on the gas pressure through the pipes. They will then take an average of this figure during the billing period. This sounds like a load of nonsense to me, but then I don't fully understand the concept.

Does anyone know what/how this figure is set? Surely, it should be a figure set as standard to be used by all gas suppliers. I'll see what response I'll get from anyone who has some knowledge on this matter - I may refer this to the energy watchdog to see what they have to say.

Thanks to anyone who can shed some light on this issue.

espresso

It sounds like you have been given a reasonable explanation. I have seen various figures used on bills i.e. 39.4363, 39.4843, 39.2813, 39.2672. The calorific value varies depending on where the gas is produced, so if we import more gas this would also affect the figure.

The calorific value of a fuel is the quantity of heat produced by its combustion, at constant pressure and under the conditions known as " normal " of temperature and pressure (i.e. to 0°C and under a pressure of 1 013 mbar).

I too would like to know how often this figure is set.

HTH

Cardew

From memory - or ain't Google wonderful!!

From a Government regulation

Calculation of Thermal Energy on Basis of Declared Calorific Values
Calculation of thermal energy
7.—(1) Where a public gas transporter makes a declaration of calorific value or adopts a declaration of calorific value made by another public gas transporter in accordance with regulation 8(1) below in respect of any area within an authorised area of the transporter, the number of therms or kilowatt hours conveyed by the transporter to any take off point situated in the area to which the declaration relates during the relevant period shall be calculated in accordance with the following formulae—
number of therms so conveyed = A × B

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105.5
number of kilowatt hours so conveyed = A × B

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3.6


where
A is the number of cubic metres in the converted volume of gas conveyed to the take off point during the period and B is the declared calorific value of the gas.





(2) In paragraph (1) above "a relevant period" means any gas period during which a declared calorific value has effect.

Declarations of calorific value
8.—(1) A public gas transporter shall not make or adopt any declaration of calorific value in respect of an area within an authorised area of the transporter in respect of which he has made or adopted no previous declaration unless he has given to the Director and to each relevant licence holder who is a gas shipper two months' notice of his intention to do so and the notice is accompanied by a map (drawn to an appropriate scale) delineating the area to which the notice relates.

(2) Where a public gas transporter makes or adopts a declaration of calorific value in respect of the area delineated in a notice given under paragraph (1) above, he shall do so at such times and in such manner as the Director may direct.

(3) A public gas transporter shall publish as soon as practicable any declaration of calorific value made or adopted by him, or any revocation of such a declaration, in such newspapers as are calculated to ensure that the declaration or revocation is circulated throughout the area to which the declaration relates.

(4) No declaration shall take effect until the declaration has been published in accordance with paragraph (3) above.

Uniformity of calorific value
9.—(1) Where a public gas transporter has made or adopted a declaration of calorific value under regulation 8(1) above, he shall secure that any average calorific value of the gas conveyed to any take off point situated in the area in respect of which the declaration is made or adopted and while it has effect during any gas period of three months commencing on 1st January, 1st April, 1st July or 1st October in any year is not less than that declared calorific value.

(2) For the purpose of paragraph (1) above, an average calorific value of such gas means the value given by adding the average of the calorific values of the gas on each of not less than any six different gas days in any such gas period and dividing the sum by the number of those gas days, but so that any amount of less than 0.1 megajoules in any average shall be ignored.

Tests of calorific value by public gas transporters
10.—(1) Where a public gas transporter has made or adopted a declaration of calorific value under regulation 8(1) above, he shall carry out tests of the calorific value of the gas being conveyed to any take off point situated in the area in respect of which the declaration is made or adopted at such places or premises, at such times and in such manner as the Director may direct.

(2) A public gas transporter shall—
(a) notify the results of any tests carried out under paragraph (1) above to the Director or a gas examiner appointed under section 13(1) of the Act for the purposes of paragraph (c) of that subsection of the Act within 7 days of the end of the calendar month in which the tests were completed; and
(b) make available for inspection free of charge during normal office hours by any person the results of such tests carried out within the preceding 12 months at—
(i) an office reasonably accessible to the public; and
(ii) the place or premises at which any such tests were carried out.

JasminB

If you wish to know your exact calorific value at any date over the last five years click onto the page:

http://energylinx.co.uk/calorific.html

As you will see the figure changes on a daily basis and the UK is split into 16 seperate geographic areas.

When you see this information printed on a gas bill, the supplier will have taken the average for the period concerned. The good news is that all suppliers will be using the same data.

When looking at any date please remember that today's data will never be available as this table provides data up to end of the day just completed, we do not publish real time data.

Hope that this helps. Place it in your favourites and that way you can refer to it at any time.

lindabea

Jasminb - thank you for your very useful link. You've been very helpful and it's just the kind of information I required.