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Thread: Combi boilers to work with Evohome

  1. #11
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    Quote Originally Posted by G4RHL View Post
    DBMandrake’s detail on the hydrogen issues has triggered memories. Some of you will share them. Memories of the introduction of natural gas in the mid 1960s. Existing systems had to be converted to handle it. Ovens and boilers. New gas pipes laid all over the country. Roads dug up everywhere to lay or replace gas pipes and massive gas mains cris-crossing the country being laid underground, easements being negotiated and paid for to the farmers. It was a massive undertaking taking several years and costly.

    Now would you fund that or provide massive grants if there was an alternative system already in place? Everybody already has an electricity supply. Methods of producing electricity are getting cheaper. There is surely an obvious solution waiting to be picked up, if has not already.
    That's a great point.

    Installing the original natural gas network would have been quite an upheaval and a major project, but the dividends were obvious to anyone involved - the comfort and convenience of gas central heating vs what was available before. (Expensive electric radiators or a coal fire place in the living room ?)

    To the average household there was a clear benefit to the switch. Switching from Natural gas to Hydrogen doesn't have the same benefits for the end user - in fact it has disadvantages. You're being told to replace your Natural Gas boiler for one that can burn Hydrogen so you can get..... the same functionality you already have ? So that the Government can reach towards their CO2 emissions targets ? Telling the population they have to ditch their old boilers for a new type that they will see no real benefit from is a hard sell.
    Last edited by DBMandrake; 1st December 2020 at 11:13 AM.

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    Quote Originally Posted by paulockenden View Post
    Interesting read here from Siemens : https://www.siemens-energy.com/globa...-hydrogen.html
    Interesting read, albeit from those with a vested interest in keeping the gas pipe infrastructure intact and making profits...

    Lets pick out a few pieces.
    Green hydrogen is becoming economically more viable due to the declining costs of renewable energy as well as of electrolyzers. Linking up all elements of the energy system with hydrogen promises to deliver efficiencies, cut carbon emissions, and increase the robustness of energy systems while ensuring security of supply.
    But would require about 2.7x the electricity generation at the source for the same heat in a household vs a heat pump. So not an efficient use of renewable energy. If they want to transition everyone away from Natural gas heating where is this 2.7x greater generation going to come from to electrolyse water instead of run heat pumps ?

    The electrical transmission system is an important backbone for the transportation of renewable energy across countries. Ideally, this is complemented by the gas system: A standard pipeline can transfer up to ten times as much energy as a 380-kilovolt twin overhead power line with a rating of 1.5 gigawatts, at about one fourteenth of specific cost.
    This is an interesting snippet of information but doesn't include the approx 2.7 times advantage of heat pumps - you just don't need to transport as much energy to operate a heat pump. Also it doesn't give any indication of how suitable the current grid backbone is to carry all the additional power required for heating or what upgrades might or might not be needed. Power carrying ability of a "standard" size gas pipe vs a "standard" overhead line is a bit of a meaningless comparison on its own.

    Another factor is the integrity of the steel pipes and fittings. Depending on the quality of the steel and potential exposure to atomic hydrogen, in principle, embrittlement can accelerate propagation of cracks, reducing the pipeline’s service life by 20 to 50 percent. This is only likely, though, if the pipeline already has fractures and is subjected to dynamic stresses due to fluctuating internal pressure while at the same time being exposed to atomic hydrogen. The confluence of all three factors seems unlikely, however: Under normal operating conditions, there should be little load alternation, and only molecular hydrogen (H2) is conveyed.
    I don't like the way they're essentially brushing aside the worry of Hydrogen embrittlement. It's a very real problem and something that is dealt with a lot in rocketry for example and there is a long track record there of the use of Hydrogen. They also fail to mention the porosity of normal steel pipes to Hydrogen. A significant percentage of the gas in the pipe network will simply diffuse into the surrounding environment, which is certainly not ideal.

    Some adaptations are nonetheless required. To compress the hydrogen to the operating pressure of the pipeline, compressor stations are required along the way. If hydrogen is mixed with methane and the existing compressors for natural gas are kept in place, some parts might need to be adapted, depending on the admixture of hydrogen. If the share of hydrogen exceeds 40 percent, the compressors will need to be replaced. A complete switch to a 100 percent hydrogen pipeline requires installing new and more turbines or motors and more powerful compressors to deliver the three-times higher volume flow of hydrogen compared to natural gas.
    Yep.

    Since major milestones of such a large scale hydrogen energy system transition are not expected in Germany before 2030, the first pilots to convert existing pipelines to hydrogen duty are already under consideration and the hydrogen infrastructure should be built up in parallel with existing gas assets.
    So it's just a feasibility study at the moment with a transition not expected for at least 10 years, if it happens at all, which I think it won't.

    Nowega’s CEO Frank Heunemann believes that the German hydrogen strategy has set the right priorities. “Now it is important to set the concrete framework conditions as a basis for the development of green hydrogen as a fundamental element in the energy transition,” he says.
    Says the CEO of a gas transmission network.

    The article is a good example of those already in the Natural Gas ecosystem looking around to see if they are still relevant in a post natural gas environment and finding that yes, they could, in theory still be relevant by using Hydrogen, but the real question is a level above that - is using gas for home heating at all the right direction in the future or should it be electricity and heat pumps, and you're not going to get an honest answer to that from anyone in the gas industry.
    Last edited by DBMandrake; 1st December 2020 at 11:15 AM.

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    Good points. But the thing about 2.7 times the power isn't really fair because I'd expect hydrogen production to be sited close to sources of zero carbon electricity (solar farms, wind farms, tidal basins, etc.) And because (unlike electricity) it isn't an easily storable form of energy it doesn't matter that zero carbon energy production isn't constant.

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    Quote Originally Posted by paulockenden View Post
    Good points. But the thing about 2.7 times the power isn't really fair because I'd expect hydrogen production to be sited close to sources of zero carbon electricity (solar farms, wind farms, tidal basins, etc.) And because (unlike electricity) it isn't an easily storable form of energy it doesn't matter that zero carbon energy production isn't constant.
    But if the desire is zero carbon emissions then you donít produce hydrogen. Not with current technology. The answer is a no brainer. Everybody already has electricity, no pipes or gas needed. It seems silly to invest in what is really an out of date technology. It could well be explosive!

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    Quote Originally Posted by DBMandrake View Post
    Has there been any real movement on this though or is this just wishful thinking on the part of the fossil fuel industry?

    You can't just pump pure Hydrogen gas through the existing natural gas pipe network without replacing pretty much all the piping and joints because the tiny Hydrogen molecules are so prone to leaking through typical pipe materials and fittings as well as causing metal embrittlement of the pipes.
    .....
    Fascinating post, thanks for that. Iíve been wondering about hydrogen and heat pumps. Maybe this thread should be retitled and made a sticky, itís getting very educational.

    One of my neighbours recently removed a fairly new (maybe a year or so old) oil fired boiler and replaced it with a heat pump (looks like air source to me). Must ask him about it as it would have been an expensive job. It seems a shame to throw away a nearly new boiler (maybe he was able to sell it). Maybe he just didn't want to be dependent on oil deliveries.

    We're fortunate, despite living in rural Worcestershire, we have mains gas.

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    Not to hijack the thread but a little more info on hydrogen here: https://www.carbonbrief.org/in-depth...climate-change

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    I can see hydrogen working in new housing estates where bulk storage is employed, in much the same way that some rural housing estates now are run off communal bulk LPG when it's impractical to run a gas main to them. It could work as a drop-in alternative to individual houses supplied with LPG too, assuming their pipework is either capable of taking it or easily renewed. Beyond that, I think hydrogen is a distraction rather than a solution. The cost and upheaval of changing everyone over would be enormous, likely resulting in higher fuel prices to the end user as costs are clawed back for no tangible benefit to them. Heat pumps, and cleaner fuels for off-grid gas, have to be the way forward. Oil-fired boilers could be switched to biodiesel relatively easily - B10 blends can already be accommodated, and up to B30 with a simple pump change - although the difficulty with that ultimately becomes the supply of sufficient quantities of fuel.

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    Presumably, hydrogen can't be manufactured at the domestic level? It's a simple process, after all.

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    Quote Originally Posted by filbert View Post
    Presumably, hydrogen can't be manufactured at the domestic level? It's a simple process, after all.
    Unfortunately I don’t believe it is a simple process but a costly one and at present using natural gas is cheaper than electrolysis. My own view is the government is better looking toward reducing prices for electricity, subsidies and more investment in generation, even massive heat pumps underground somewhere, as the infrastructure for every home and business is already in place. It does not look as though it is going to happen and the potential running costs of an electric system at present are worrying. Such that my final decision may be to replace the gas boiler with another and install a thermal store which will then give me some future proofing if the costs of thermal panels or other methods of generating power come down. Indeed including electricity.

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