OPINION


Your letters


This month: Discussion on the merits of district heating networks


Seeking good-quality combined heat and power… Following the article by Peter Hamnett and Phil Jones (‘Power Debate’, May Journal, page 38), in response to my article in March (page 55), it is clear that our principle difference relates to the reference factors taken for calculating fuel savings and carbon dioxide intensity in district heating (DH) networks. Hamnett and Jones (and previously Paul Woods, on page 16 of the April edition) argued that an average electrical grid factor should be used for combined heat and power (CHP) – or possibly that a worse effi ciency fi gure should be used – to maximise their CO2 emission-reduction claims. The ‘EU Directive on the promotion of cogeneration based on a useful heat demand’ and the CHPQA take the view that fuel savings are measured against a ‘same-fuel’ source, with the CO2 intensity of heat being calculated against this comparison. The Directive is described in the


above article as being ‘quite removed in purpose’, despite the fact that its


of this utility and have no infl uence on the CO2 intensity of the heat delivered. We know that DH networks


can be economically feasible but the question is, can they meet our requirements of virtual zero CO2 heat before 2050? James Thonger


intention is to ensure the installation of ‘good quality’ CHP. The authors further suggest that a calculation methodology used for building regulation compliance should be used in lieu of the Directive to calculate the CO2 intensity of their DH networks; but this methodology leads to the outcome that signifi cant CO2 savings can be claimed for DH networks that use more primary fossil fuel than conventional supplies. DH networks are a monopoly


utility provider and, given the vast amount of fuel that they consume, should be subject to national policy decisions on effi ciency of fuel usage. Consequently they should comply with the requirements of the Directive. Building services engineers are simply the recipients


…Making emissions factors count The combination of Paul Wood’s letter with the Peter Hammett/Phil Jones deserves further comment. Most importantly, the Directive applies to all energy using buildings individually as well as to grouped energy users. For compliance, there is no escape from this. Effectively the Directive states


that, given a combination of loads or a single load, to be met in whole or in part by different systems using the same fuel(s), the same factor(s) for emissions must be applied to the different systems. Different systems or combinations of systems will use different combinations of different fractions of different fuels, of course. Thus for new loads to be met by


use of additional supplies of natural gas, the only relevant emission factors are those applied to the use of the gas. Also, if other fuels are ‘displaced’ by any or all of the feasible systems, then the emission


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a new brand; a new HVCA 20 CIBSE Journal June 2012 www.cibsejournal.com www.b-es.org


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