Opinion

Is it time to answer those awkward questions on CHP and district heating?

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Comments

  1. Bravo – Someone with the sense to stand up to the sheep-like (and incorrect) belief that district heating (Community energy before that) is energy efficient and low carbon. There are appropriate circumstances but inflexibility and underreported losses often make large scale district solutions expensive and far from low carbon. But the flock is well herded I’m afraid.

  2. Good to hear the opinions of a practitioner. It certainly challenges the positive spin we keep hearing.

  3. CHP is of marginal benefit as the grid decarbonises – no arguments there.

    Small scale CHP (with low electrical efficiency) is worse than individual gas boilers – no arguments there.

    All heat sources (CHP, boilers, heat pumps, fuel cell) are worse than individual gas boilers if the engineers screw up the distribution network design and commissioning – no arguments there.

    DCLG’s reliance on BREDEM (SAP) for evaluating the performance of buildings exposes them to the weaknesses of this tool – no arguments there.

    BREDEM (SAP) imposes no requirements on distribution network efficiency and indeed protects engineers who screw up distribution network design, commissioning, and subsequent operation by providing absurdly generous assumed values for distribution network efficiency – no arguments there.

    Unscrupulous engineers exploit these weaknesses to specify terrible systems and win the business of developers on the basis of lowest upfront cost – hardly any surprise here either.

    Summarised in your own words: “There are no statutory requirements for any installation standards or performance standards, so one should not be surprised at the outcome.”

    The industry provides what developers ask for – which is cheap – rather than what UK plc needs – which is good. We could tell the same story about insulation, thermal bridging, ventilation, and air tightness.

    District heating can be done very well indeed, as can insulation, thermal bridging, ventilation, and air tightness. The steps needed to ensure that those developments of yours are to passive house standard are the very steps needed to ensure that their communal hot water systems (insulation doesn’t help with hot showers) are low carbon and future proof.

    Step 1 is probably to stop throwing rocks at your allies in the world of energy efficiency. (there’s a very good reason that the CHPA is no longer about CHP but also incorporates demand response and energy efficiency…),

    Step 2 is working out how to educate lead customers, those with an interest in the lifecycle cost of their buildings, in how to specify a building in order to achieve our aims. Do you have any helpful suggestions on this one Bill?

  4. Three starters for ten:

    1) Delete the get out of jail free clauses in BREDEM (SAP) on the assumed efficiency of heating systems. Require ‘type approval’ of systems or detailed calculations for one-off designs.

    2) Take the NHBC’s technical bod to one side and offer him the opportunity to update NHBC’s absurd hot water requirements before DCLG makes him look stupid by explicitly outlawing such requirements in the building regulations. (DHW at >60C at kitchen sinks, unless you’re installing an individual gas combi boiler in which case no rules apply) Designing efficient district heating solutions for new build would be a lot simpler if the insurer’s performance standard was the same as for individual gas boilers.

    3) Change the BREDEM (SAP) scoring from ‘marginal fuel cost/emissions’ to ‘lifecycle fuel cost/emissions’ to encourage forward-thinking on behalf of planners. Then may the most appropriate solution win. ;-)

    We’d be happy to design you an efficient, cost effective, communal heating system in new build tomorrow. Heat pump based with flow temperatures in accordance with Swedish Building Regulations: max 55C at design condition. You couldn’t insure the finished build using the NHBC though, because we refuse to meet their specifications, and you wouldn’t receive a great SAP rating, because we design for lifecycle cost/emissions not marginal fuel cost/emissions, and that isn’t captured under SAP.

  5. Good to get these issues aired. The caveat in Bill’s opening sentence is crucial – he’s specifically talking about New-build! For existing networks of older buildings – like Universty estates, hospitals etc and housing schemes with group heating then upgrading the energy supply infrastructure to deliver power and heat (sometimes cooling too) does have multiple benefits – displacing high cost electricity can pay for the sunk costs of distribution networks. And once sufficient variety of building types connected our experience at the Univerdity of Edinburgh is that the diversity means we run our four engines 24/7 serving quite diverse campus networks.

    David Somervell, sustainability adviser, University of Edinburgh

  6. Thanks for your comment, Martin.

    Could you please direct me to data from examples of these systems operating at the ‘economic optimum’ in the UK that demonstrate CO2 and economic savings?

    As a matter of interest, do you have any data that substantiates the SAP Calc and its prescribed losses of 5% in dwellings?

    Many thanks

  7. I’m a German Engineer working in scientific analysis of all types of heating systems for many years now. I have a special focus on the comparison of different energy systems, such as buildings with insulation, CHP, heat pumps or boilers or any combination of these. However, so far I have to say that I never heard or read that:

    “…it’s a fact that existing CHP and district heating systems are generally more expensive to run, consume more energy and issue more CO2 than an equivalent “conventional” system.”

    In my view such an aggressive claim would need extremely well grounded evidence, to be taken seriously. Progressive countries like Sweden, Denmark and many cities in Germany use CHP to significantly cut Carbon emissions. This is verified by many studies and I have made enough calculation on my own that I am as certain as a scientist can be that the notion of CHP as an environmentally sensible solution is correct.

    Like the author I am against simple “always do this and it will work” recommendations. For individual constructions like buildings, its simply not a good approach. However, in many cases DH systems are a very promising and good solution to decrease resource consumption and cut carbon emissions. Cost calculations are always very sensitive depending on the underlying basic economic assumptions, especially on those on interest rates, investment costs, taxes, subsidies and CO2 prices – so they are a poor indicator for the benefit our environment (and thus our future) gets from a system. Just so you know in Denmark DH from CHP is the cheapest form of heat.

    I agree with the author that probably DH is not a sensible approach in low heat-demand density areas with new-build single-family houses but in inner cities or even in moderately insulated new build multi-apartment buildings, the situation can be very different.

    The theory behind CHP after all is convincing. If you generate power, you have to generate waste heat (2nd law of thermodynamics). CHP allows you to upgrade that waste heat to a useful temperature level. With this you replace heat that has been generated by using valuable fuels directly for generating “low value” heat and thus reduce resource consumption and emissions.

    If the author doesn’t believe me, I am open for a challenge. The author can send me his calculations for review. I am pretty sure I will find a mistake in the calculations. If I do, the author will pay me for the time the review took – if I don’t I will make the result public here or support his claim in another article for free. If the author is so sure about his claim, I expect to read from him soon.

    Until then I caution everyone against believing this unusual and so far poorly justified opinion.

  8. Most consultants design and commission DH for an overestimated peak demand and see that as job well done. The resulting performance is poor at the everyday much lower loads. It’s no surprise that incorrect design and commissioning lead to poor DH – the problems is many designers haven’t bothering to find out / think the issues before starting work. For instance Bill Watts’s 2010 document against DH and CHP discussed how electrically led CHP, sized to meet the electrical demand of the buildings being heated (so the CHP dumps 20% of heat generated and supplies 40% of total heat demand) showed little environmental benefit- which to me demonstrated that the author doesn’t know enough about CHP/DH. Heat lead CHP with a thermal store sized at the economic optimum (zero heat dumped and CHP supplying about 75% of total heat demand) will deliver far higher CO2 and economic savings and this is what a knowledgeable consultant would suggest and what the profit making ESCOs: Eon, SSE, Cofely etc build.
    Typical UK design of heat networks has been poor and this was Phil Jones’ motivation to behind getting CIBSE and ADE fund the Heat Networks Code of Practice. Members of the industry keen to improve things contributed and the end result is an excellent step forward which will help designers and clients build better DH.
    Bill says there is a dearth of data – well I think a consultancy worth it’s salt should monitor some of the schemes it’s designed. Then it can learn, improve the designs and not accept poorly commissioned systems on their client’s behalf. Invariably this will lower capital cost too. I’ve yet to see a handed over DH system with a temperature difference of more than a few degrees unless an ESCO was involved. ESCOs have worked this out as it costs them money. Commonly low dT is a due to flushing bypasses left open. It shows the lack of knowledge that the consultant can’t spot this or other simple problems. In my view there is a lack of interest in understanding how DH could work more efficiently, an absence of ambition to improve.
    Bill has a go at CHP, which will have reducing CO2 saving in future, but that rather misses the point of DH ? It’s easy to change a few DH heat sources than thousands of combi boilers. Look at how Sweden has fuel switched over the years – this rate of change wouldn’t have been possible if there wasn’t lots of DH. As for a good heat sources can I suggest SELCHP surrounded by inner city London which has be throwing away around 100MW of heat since 1994 – how much of London would that heat? If it were a Danish EfW plant most of the heat would come from the flue gases and result in much less sacrificed electricity. If there is no EfW plant locally how about a heat pump from a river/lake/industrial waste heat /sewage works or deep geothermal or AD etc ….

  9. Thankyou, our new system is installed overhead along our only fire escape staircase on each floor of our tower block, possibly a bit unwise. The pipe is carbon steel and the connectors are brass, probably also a bit unwise. I’m learning to abseil.

  10. Hi Bill
    This is an extremely interesting article that highlights many of the imperfections relating to CHP design. I feel that clients are being mislead and designers should be pointing out that CHP has its downfalls unless its used in the correct application and used correctly.

    I’m currently doing my dissertation on the inefficiency of CHP & CCHP systems at part load operation. If you have any information that could assist me or you could point me in the right direction then please let me know.

    Thanks

    Paul Copper

  11. Its a pitty the DH experts fail to talk about the effectiveness of what is actually installed in the end users home! Whilst some customers are being muted by some protection scheme sponsored by ADE there is no protection for the environment! Just because the experts are waving hardcore reports that are generated within a circle of friends who award each other with annual awards and support seeking GOV handouts nobody is willing to publish how much heat venting inside the customers cupboard was not intentional nor transferable where intended! Are customers simply downloading more heat than they really need to yet amazingly reach low carbon? The more heat downloaded regardless if it was required the more the networks looks “sustainable” and of course receives a second income from the sale of electricity sold to the grid.

  12. It’s an imperfect world and technology, by its nature, changes and reflects not just the advancements brought about by our nature, but also those of the days political backdrop.

    I have worked with many and diverse technologies. I’m not a boffin, nor am I a geek. What I do know (and this is only from decades of shopfloor experience) is that, whether the technology is a huge step forward or simply a stepping stone, it all comes down to the implementers, those who design the product in and those who install the product to specification. Then measure and assess your results honestly and move forward.
    Too many if, buts and may-bes in a life that is and should be better than that. Get the facts, speak the truth and the world will prosper from well used intelligence.
    CHP has a place, simply engineer it in.

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