Posts by David Haywood

  • Feed: Fulminating and fermenting, in reply to Fooman,

    Is it better to (re)use an effluent stream in an industrial process, or just release to the environment without making use of it, aside the from the arguments over which industries/end users should use gas as an energy supply or commodity?

    Well, yes, you’re absolutely correct that it’s better to make use of an effluent stream – and, of course, some of the CO2 production systems actually burn hydrocarbons solely for the purpose of making CO2.

    But hell it’s frustrating that they produce CO2 right there in the fermentation process (in the same building) and then chuck it into the atmosphere and bring in fossil CO2 all the way from the Naki. Couldn’t they just leave the CO2 in the beer in the first place (like you do when you’re making it at home) or – failing that – capture it and reuse it for carbonation.

    No doubt someone has worked out that (excluding the environmental costs) it’s cheaper to use fossil CO2 than to capture it from fermentation – but it seems so inelegant from an engineering point of view.

    Maybe I just don’t like fizzy beer.

    Dunsandel • Since Nov 2006 • 955 posts Report Reply

  • Feed: Fulminating and fermenting,

    Russell you lucky, lucky bastard…

    The penny dropped when I discovered that commercial breweries add the co2,

    Yes, and unbelievably they don’t capture and re-use CO2 from the fermenting stage but they actually use fossil CO2 stripped from natural gas. I know it’s completely insignificant in terms of our CO2 emissions but for fuck’s sake…

    Hence my refusal to drink that fizzy Steinlager stuff under any circumstances – unless, of course, no other beer is available (and also because it tastes hardly different from L & P).

    Dunsandel • Since Nov 2006 • 955 posts Report Reply

  • Hard News: Going solar?, in reply to Rich of Observationz,

    Isn’t there a fairly large conversion loss, especially on a battery that’s nearing the end of its days?

    Brief reply because feeling very woozy...

    My understanding from the electrical guys is that on these batteries the BMS prevents excessive charging as the capacity reduces (not like the old lead-acid batteries where you lose a cell and effectively have to waste a bunch of energy into it anyhow to bring the whole battery up to charge).

    In other words, the efficiency remains the same over the lifetime of the battery, but the capacity reduces. And, of course, what is an electric car battery with 50 per cent capacity loss is still a very decent chunk of storage for a house/business.

    But I've never worked with battery packs with modern BMSs myself -- I'm just going by what I'm told!

    Dunsandel • Since Nov 2006 • 955 posts Report Reply

  • Hard News: Going solar?, in reply to Russell Brown,

    Thank you! Nova sells a SolarElite system using these panels.

    The panels have “flow tubes” but I can’t tell from the comments here whether these are the good sort of tubes.

    It appears to be a flat plate absorber not a "heat pipe" system. The disadvantages are:

    1. Uses more energy from your HWC in anti-frosting at night (less of a problem in Auckland than CHCH, of course).

    2. If it gets damaged (hail, overheating, etc) then you have to replace the whole unit, and not just the tubes.

    3. Uses more copper, so more expensive (this model looks like it has copper sandwiched into aluminium, which might cause electrolytic issues in the long term).

    4. Liable to have greater heat losses than a comparable "heat pipe" unit, but again this might not be such a problem in tropical Auckland.

    Having said all that, it might be completely fine for your situation. Alas that I'm not at all familiar with this particular model. Has anyone else had any experience with them?

    1. How many have been manufactured and for how long?

    2. Are there any known problems? Frosting, overheating, pump life, etc.

    3. What is the warranty?

    4. What sort of controller do they use? Does it have a timer, etc. to turn of the HWC during the day?

    See if they will give you the phone number of a customer who has had one installed for ten years or so.

    I'd try to find this out for you but am currently dealing with children (and self) in tricky recovery period... Many apologies!

    Dunsandel • Since Nov 2006 • 955 posts Report Reply

  • Hard News: Going solar?, in reply to James Green,

    I’m curious about the cleaning issue (many claim to require no cleaning). Is it that the kind of scum that normally builds up in drain pipework reduces the HX efficiency, or another kind of problem?

    Yes, the scum reduces the heat transfer. Is your one a gravity film (i.e. mounted vertically) unit? If so, it seems that these are much less prone to fouling.

    The horizontal units seem to be a problem, particularly the ones with the corrugations on the inside to increase the heat exchange.

    Either way, you should definitely install it so that it can be easily cleaned (hopefully just a single grub screw that allows you to remove the final plastic section that diverts the wastewater into the drain). If you can clean it every couple of months it should be no problem at all (regular cleaning is beyond most people, alas!)

    Dunsandel • Since Nov 2006 • 955 posts Report Reply

  • Hard News: Going solar?, in reply to Lucy Telfar Barnard,

    A minor quibble, but presumably you’d need to adjust your shower mixer a bit in the early minutes of your shower, as the cold water starts to heat up and so the hot water needed becomes less?

    You can put the output of your HX into the HWC (saves energy only) or – as you say – into the shower, which means you have to bugger round with the mixer, but also that you can have a much longer shower for a given size of HWC.

    I’ve done heaps of modelling on these systems and they are good in theory. The problem is the HX cost and the cleaning. Most systems use some sort of horrible draino-type stuff every few weeks.

    I’ve actually developed a system that gets round both these problems (cleaning better than cost, alas) but I have yet to get it beyond a prototype (mostly my fault).

    Dunsandel • Since Nov 2006 • 955 posts Report Reply

  • Hard News: Going solar?,

    Russell, sorry not to have replied earlier but have had bad cold followed by possible "mild" influenza -- also looking after children with same.

    I'm going to be annoying by saying that you should definitely install solar water heating -- in about the year 2000. Given the problems with time travel then your biggest question should now be: will I still be in the same house in 10-15 years?

    The price sounds no worse than the standard rip-off as long as it includes everything -- HWC, plumbing, building permit, etc. You should double-check that there are no extras hidden away anywhere. As someone else has pointed out, the Chinese systems land in Auckland for about a grand, but there is nothing you can do about all the other fingers that manage to get in the pie on the way to your house.

    In general, the "heat pipe"* systems have a bunch of advantages over the flat plate absorbers -- in other words, the glass tube jobs are better.

    An important exception to this is the Thermocell panels, which look like a flat plate absorber, but are actually are a flat "heat pipe" system. These panels are easily the most elegant design available anywhere from an engineering perspective, and I know of 30 year old systems that are still going strong without any maintenance ever. The downside is that they're expensive.

    If you flip me the specs, I'd be happy to have a look at the proposed system for your house.

    In general, the inverter required to drive your HWC from a PV array would be pretty chunky -- don't want to go into a lot of detail but I'm not a huge fan of heat-pumps for HWC though I have designed/built them myself. I'm currently recommending that grid-connected PV should be only what you use as a "base load" during the day -- sounds like under a kW from what you say. This will change in the future.

    I guess I also have philosophical objections to the conversion of 100 per cent exergy from your PVs into 100 per cent anergy in your HWC. It's contrary to everything I do.

    My guess is that the biggest change in NZ will probably come when 2nd-hand batteries from electric cars start to enter the market. That will enable a very cheap battery to be integrated into your house/business and will change everything.

    I hate to answer money questions about the future, but I had the same debate (solar HW now -- or wait for cheap PV) with myself about 18 months ago. I installed solar HW. I guess that's sort of an answer.

    [* Not strictly a heat-pipe, I know, I know, because no wick.]

    Dunsandel • Since Nov 2006 • 955 posts Report Reply

  • Hard News: Going solar?, in reply to Stamper Stamp,

    Folks – if it was a ‘no brainer’ to move to solar – every one would do it; instead we have the arguments for/against for trying to save planet/energy/money.
    It you have to argue – it is obviously NOT compelling.
    So – are we going to save planet/energy/money – or are we just going to “feel good” ?

    What an extremely strange comment.

    The biggest problem with (non off-grid) residential energy systems in NZ is that the payback period is usually a bit longer than the period that we own a particular house, e.g. payback period is seven years and on average we buy/sell houses every six years.

    That means the next person gets all the savings and you get to pay for it (the evidence is that such systems don’t significantly increase the selling price for your house).

    It may seem like other things, but essentially that’s the “debate” when it comes to installing this technology in NZ. And that’s why there’s essentially no debate in some of the other countries that people have listed.

    That, and most people don’t like paying a big chunk of money up front.

    Maybe green energy isn’t a reality after you have looked at the whole picture – a bit like the bio-energy fiasco.

    I can answer that for you. I have looked at the whole picture in NZ (it was my job for a while), and green electricity is a trivially easy “reality” in this country. Green transport energy is much more difficult in NZ, but huge reductions in dirty energy are also possible there.

    Dunsandel • Since Nov 2006 • 955 posts Report Reply

  • Hard News: He Panui: Media Take, in reply to Steve Curtis,

    Is there a problem in that your media review is partly like travel journalism which as we know is mostly sponsored by the places visited. Im not saying its the fawning kind but if your format requires ‘guests’ where you then take their head off, they sure arent coming back in the small pond of NZ journalism.

    Yes, and Russell’s interviewing technique is somewhat in the mould of Geoff Robinson – very polite and courteous (which I personally prefer). But you’ll also notice that Russell gives his interviewees a lot of rope. Pretty often they’ll use this rope to hang themselves at some point during the interview; sometimes they don’t even notice that they’ve done it because it's all happened so subtly.

    It’s pretty clever.

    Dunsandel • Since Nov 2006 • 955 posts Report Reply

  • Southerly: Who was George Hildebrand…, in reply to Greg McCreanor,


    I tend to think that the relationship between Alington and Eliza began when he was at the Mount Hutt Roads Board in Methven and she was living with family there having been deserted and awaiting divorce. Alington was in the Hunt Club with Coleman I seem to recall…the Colemans were obviously unable to have children and an adoption would mean that Alington could see his daughter as ‘uncle George’ perhaps.

    Thanks so much for posting all that information, Greg -- fascinating stuff! And an intriguing theory...

    Do you have any theories about who paid the legal bills for Eliza Winter's divorce -- I've seen all the paperwork and it must have cost a packet! I wondered if it might have been Alington, who perhaps intended to marry her. But then his family intervened and procured a young heiress who was more suitable?

    On the subject of Eliza Webb, it would have been her 150th birthday today. In one of those funny co-incidences, it is also my son's seventh birthday. He said that Eliza could share his cake (see attached).

    The cake is supposed to be a pirate ship sailing through a tempest-tossed ocean, with cannons and a plank at the stern to allow victims to be conveniently flung off. [And yes, that is our clawfoot bath in the background with a laptop sitting in it -- don't ask].

    We hope that Eliza would have liked such a cake.

    Dunsandel • Since Nov 2006 • 955 posts Report Reply

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