Southerly by David Haywood

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Southerly: A Tale of Two Iceblocks: Part 1 (Or How Analysis of Greenhouse Gas Emissions in New Zealand Can Cause Us To Do the Wrong Thing)

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  • Ian Dalziel, in reply to Moz,

    the body electrick…

    I’m in inner-city Sydney wondering why my internet connection is so awful today. Ditto the different provider cellphone internet. First world problems… but it does remind me why I want to be grid-agnostic for electricity.

    We (the planet) may still be in the tail end of a Geomagnetic Storm…

    Christchurch • Since Dec 2006 • 7953 posts Report

  • Ian Dalziel, in reply to David Haywood,

    My (small & homebuilt) PV system as well as my wind turbine have been sitting in the loft of my workshop since the earthquakes. Quite unforgivable, I’m afraid.

    Totally forgivable - it's good to have 'lofty aspirations'...
    ;- )

    Christchurch • Since Dec 2006 • 7953 posts Report

  • Alfie, in reply to Rob Stowell,

    Solar City, who have taken over the sales are, are … hopeless (in my experience.)

    I was speaking with a local Solar City installer last week who told me they've been instructed to flat mount all panels to save money. So instead of lifting the rear of panels by mounting them on a framework to achieve the optimum angle, they now have to go with the existing roof pitch. That's an extremely poor decision from one of our biggest solar players.

    Dunedin • Since May 2014 • 1440 posts Report

  • Moz, in reply to Alfie,

    Solar City

    Over here that name is one used by a succession of phoenixing solar scammers, IIRC. is a geek forum with a useful green sub-board for that stuff.

    Over here they just charge you if you want tilt rails, and most companies will do it if you ask. With the granny flat I was torn between an off-centre roof peak to get the north face to 50 degrees, and a single-piece roof with more panels at about 10 or 15 degrees. The cost difference meant it was cheaper to go one-piece, but the winter performance was noticeably worse. Still arguing with the architect (my partner) while the granny flat is on hold - we're probably moving instead.

    Sydney, West Island • Since Nov 2006 • 1233 posts Report

  • Moz, in reply to David Haywood,

    composting lavatory

    We have one in the shed, packed away, because I never really solved the vinegar fly problem to my partner's satisfaction, and with six people we really do need the second toilet working all the time. The "toilet room" is big enough to fit the composting toilet in front of the water-waster, but having it there makes the water one unusable. I really want to put squat rails on it, too, but have not yet got round to that. Maybe I should do that today rather than sitting on the interwebs.

    I've often had to strip them at the door, wipe off the worst of the mud, and then carry them into the shower.

    You're too kind. My mum used to hose us off on the lawn, then make us strip and go through the bootwash barefoot before we were allowed in to shower. We quickly learned that cold, windy days were a time for caution around mud.

    But the difference between six adults who all understand that we have 300 litres of hot water each day, the end, and two children who like to play with dirty things is huge. We also live in Sydney, where heating is basically optional and cooling is becoming less so. So a lot of our "efficiency" comes from living in a mild climate.

    Sydney, West Island • Since Nov 2006 • 1233 posts Report

  • Brent Jackson,

    When we had our solar hot water installed (an Edwards LX305 in 2004), I asked about increasing the angle of the panels, and was shown a convincing graph of the efficiency based on angle, and basically the efficiency does not fall off all that rapidly. Basically, if your panel is facing within 30degrees of north, and is tilted between 15 and 50 degrees you'll be getting over 95% of the optimal annual solar input for a fixed panel.

    Our return on investment calculation at the time, was that the system would never pay for itself (we'd make more money by investing the funds, and paying more for our electricity). We installed it anyway because we felt it was a good thing to do. As it turns out, investment returns have dropped, and electricity prices have increased, so it was probably a good investment. We turn the mains feed to the cylinder off at the start of November, and turn it back on at the end of April, so basically have free hot water all summer. Of course it is still helping the rest of the year, so our power bill is less than similar families (2 teenage children). We use 14kw/day around this time of year (electric blankets and heaters), and about 8kw/day in summer (really should get a more efficient fridge).

    When our dishwasher was installed, I asked for the plumber to connect the hot pipe to it, but he refused, saying it would invalidate the warranty. Of course the dish-washer is out of warranty now, but I don't think the $200 (or more) it'd cost to get it changed over now would be recouped, but it does annoy me that we have to unnecessarily heat water to run it in summer.

    Auckland • Since Nov 2006 • 620 posts Report

  • Moz, in reply to Brent Jackson,

    Lost my reply, FFS.

    was shown a convincing graph of the efficiency based on angle

    Was that the misleading raw output one or the seasonal output graph that actually matters? Until you can save the excess hot water from summer to use in the winter, it doesn't matter how much excess you have in summer.

    This graph is probably what you were shown, and it's a class case of "technically correct but irrelevant and misleading". For PV it works because most people have a year-round surplus from their PV during weekdays, and don't store their PV output. So all they care about is maximising their annual output.

    With hot water that is very rarely true. Most systems have storage, and the cost of extra collectors is low compared to the overall system cost so it makes sense for most people to over-collect. That means the desirable system characteristic is to maximise output in the winter trough in order to reduce the need for boost heating.

    Especially for people who are switching from off peak resistive systems to on-peak boost (as in Australia and very probably NZ) because the boost cuts in in the evening when it's clear the solar has not got the water hot enough. A poorly set up system can end up increasing energy costs because while you're buying less total electricity, the electricity you do buy costs a lot more.

    This blog post amusingly manages to both quote the correct text, then immediately summarise it but get it backwards. The bold text is wrong :) Full pdf (2 pages) and has better graphs of how tilt affects seasonal output.

    Sydney, West Island • Since Nov 2006 • 1233 posts Report

  • Brent Jackson, in reply to Moz,

    Thanks for that Moz. According to that we should have the panel at 33 degrees for maximum annual solar input with a fixed panel. But as you say that is not what we should be trying to maximise. What we want is sufficient hot water all summer, extended as far as we can for spring and autumn. Based on when we currently turn the power supply on (May to October) it appears that we need about 5kwh/m2/day, so setting to the winter tilt angle won't give us sufficient heating all summer. So, eye-balling the Adjusting the tilt four times a year table, probably 45 degrees would maximise electricity savings.

    However, this may be overly simplistic, as the turning on of the power booster is usually the result of 4 cloudy days in a row, which will occur much more often in the seasons other than summer.

    Especially for people who are switching from off peak resistive systems to on-peak boost (as in Australia and very probably NZ) because the boost cuts in in the evening when it’s clear the solar has not got the water hot enough.

    We don't have peak and off-peak power charges, and the booster is not timed, so as we mainly shower in the morning, the booster will heat the cold water being added to the tank, which would be unnecessary on a sunny day, as the sun itself can achieve it by the end of the day.

    But better to spend a little bit more than to suffer luke-warm showers in the colder months.

    Auckland • Since Nov 2006 • 620 posts Report

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