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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  • David Haywood, in reply to Shaun Barker,

    In response to the question asked by Steven Crawford, above – the analysis of the net benefit (or otherwise) of solar power (photovoltaics) in NZ has been done – in it’s current form solar has little or negative GHG benefit in NZ if a lifecycle analysis is done (published by Luke Schwartfeger and Allan Miller, EEA Conference & Exhibition 2015, 24 – 26 June, Wellington, available here.

    Thanks for posting that link, Shaun! Photovoltaics (grid-connected) don’t make much sense from an energy engineering perspective in New Zealand either (from the viewpoint of the whole country). I hadn’t seen that paper and must say I’m surprised that the difference is quite that much in terms of GHGs. I shall read it with interest.

    EDIT: Steven Crawford’s quite right then – the electricity companies should be making a huge deal of this…

    Dunsandel • Since Nov 2006 • 1156 posts Report Reply

  • Bart Janssen, in reply to Shaun Barker,

    Yeah it is pretty clear that NZ the best thing to do would be switch the bulk of our transport to electricity since that would convert gasoline use into (renewable) electricity use. Bearing in mind the energy costs of building new cars.

    But there are two things about solar electricity generation that make it slightly better - the first is the value of generating power close to the site of use, that acts to make the network more robust and reduces losses in the distribution network. Not a huge plus but still a plus.

    The second is that by adopting an new, but not yet perfect technology, you drive the improvement cycle and there is still a lot of room for improvement in solar electricity generation.

    That said NZ sucks for solar power, it's not hot enough for A/C to be relevant in summer and it is just too cloudy for really good energy production.

    Auckland • Since Nov 2006 • 4445 posts Report Reply

  • Moz, in reply to David Haywood,

    Photovoltaics (grid-connected) don’t make much sense from an energy engineering perspective in New Zealand either

    Well no, when your existing electricity supply is largely renewable the maximum possible GHG savings are negligible. I feared for a second it was another of the misleading calculations that we see so many of on sustainability.stackexchange, but nope. In Australia, on the other hand, PV very directly displaces brown coal (or carboniferous earth to give it the proper name... 40% or more of the "coal" remains after burning) and it's hard to get a bigger win than that.

    One thing that local generation does is increase resilience. Or it should.

    IMO every single inverter should capable of islanding (operating when the grid is down), and have a large, mechanical switch on the front indicating whether it is or not. Ditto the install. Our system already has labels to encourage emergency services to turn it off before getting involved, and the extra step is from "this might be live so you should treat it as though it is" to "this is slightly more likely to be live, so you should treat it as though it is".

    At least with passive hot water systems they will work as long as there is sunlight and water. If you have a pumped setup, though, it needs power. See above "capable of grid-independent operation" step. I am in the process of designing a sleepout that will have a solar-powered UPS which is an off-grid setup in all but name. Mostly because it's not much more expensive than getting power to the sleepout. Hopefully my free, ex-demolition coolstore panels will arrive in October and I'll be able to start construction.

    Sydney, West Island • Since Nov 2006 • 1169 posts Report Reply

  • steven crawford,

    carboniferous earth to give it the proper name…

    Thanks Moz, I just didn't know how to explain my fetish for paddle pops.

    Atlantis • Since Nov 2006 • 4163 posts Report Reply

  • Shaun Barker, in reply to steven crawford,

    In the question you asked above about concentrated solar power (solar thermal). This data was compiled by Vidal et al (Nature Geoscience, 2013, attempted link here to their supplementary data. In terms of resource consumption, CSP isn't too bad (PV is one of the worst) - not sure how effective it would be in NZ except for a few special areas in summer. The move to the electric fleet is the critical one - there are currently over 3,000,000 registered cars and 600,000 trucks on NZ's roads. Just short of 4,000,000 all up. If we replaced these with electric vehicles in an average battery capacity of 50 KWh, this would be around 200,000 MWh of storage capacity. If this could be charged up during the day via PV, and drawn down during the night time, this would be displace all of our thermal generation. Of course, that would also require us having significant new generation to charge up during the day, and would require the whole country not being covered with cloud for a week or two during winter......interesting times, and requires long term planning to really pull this off.

    Since Jul 2016 • 2 posts Report Reply

  • Lilith __, in reply to Shaun Barker,

    In terms of resource consumption, CSP isn’t too bad (PV is one of the worst) – not sure how effective it would be in NZ except for a few special areas in summer.

    Could it ever be feasible for each house to have a thermal-solar system on the roof to heat the hot water?

    (thanks for the link)

    Dunedin • Since Jul 2010 • 3886 posts Report Reply

  • David Haywood, in reply to Lilith __,

    Could it ever be feasible for each house to have a thermal-solar system on the roof to heat the hot water?

    Sorry Lilith – hasn’t realized you were asking about CSP (my earlier answer referred to solar thermal for hot water production)…

    Dunsandel • Since Nov 2006 • 1156 posts Report Reply

  • Lilith __, in reply to David Haywood,

    solar thermal for hot water production

    I remember having some quite acceptable washes under one of those "solar shower" things you can take camping. (essentially a black plastic bladder you fill with water and lay in a sunny spot). Admittedly, that was summer, and one has lower standards when camping, but...

    Dunedin • Since Jul 2010 • 3886 posts Report Reply

  • steven crawford,

    My favourite carbon neutral fuel for water heating is fire wood. But council dosn’t seem to like fires to heat water. There emissions tests measure the radiant heat as beneficial but they don't see how stored heat can justify the chimney smoke.

    Atlantis • Since Nov 2006 • 4163 posts Report Reply

  • Rich of Observationz, in reply to David Haywood,

    Also, you could maybe make near zero-energy iceblocks in winter in somewhere like northern Manchuria (or indeed the Mackenzie basin) by pumping input water from the zero degree layers of a semi-frozen reservoir?

    Back in Wellington • Since Nov 2006 • 5550 posts Report Reply

  • Rich of Observationz, in reply to David Haywood,

    Total digression, but something just occurred to me about HFO-1234yf.

    When CCl4 was widely used in the home, a noted hazard was that if you smoked whilst using it (the sixties were the sort of time when you could work with one carcinogen whilst deliberately inhaling another), it would be oxidised to phosgene (carbonyl chloride), which isn’t good for you.

    If an aircon filled with CH2=CFCF3 leaks and somebody is smoking in the car, it’ll get oxidised to COF2 which is similarly bad for you. I guess it’ll remove people who smoke in old cars with leaky aircon from the gene pool.

    Back in Wellington • Since Nov 2006 • 5550 posts Report Reply

  • Rich of Observationz, in reply to Moz,

    I think the problem with islanding is not so much worker safety (as you state, electricity network techs are trained to treat all circuits as live at all times) as problems of restart and load.

    If your local substation trips, then a small number of inverters will try and drive all the local loads – which they obviously can’t do, so they’ll go into a trip/restart cycle, which might break stuff. Then, if an island does get established (middle of the night, most loads switched off) it’ll be out of sync with the grid, so on restart, everything will trip (possibly accompanied by blown pole fuses) again.

    I guess there’d be ways to deal with this, like locking inverter phase to a GPS time reference, but it isn’t implemented now (and of course, since we import all such things, NZ can’t take a lead here).

    Back in Wellington • Since Nov 2006 • 5550 posts Report Reply

  • linger, in reply to Rich of Observationz,

    zero-energy iceblocks in winter

    Pretty sure that method won’t lead to any major energy saving: either you’re pumping liquid water, in which case the energy needed to then actually freeze it is of the same order as that needed to cool it from 25°C to 0°C, or else you’re trying to pump semi-frozen slush, which takes more energy.
    If you have subzero nocturnal temperatures, surely you’d be somewhat better off just leaving a tray of water out overnight to freeze, then bringing it in next morning?

    Tokyo • Since Apr 2007 • 1860 posts Report Reply

  • Rich of Observationz,

    True as, forgot latent heat. But yes, making the ice blocks in the day and leaving them out at night would work in many climates.

    Back in Wellington • Since Nov 2006 • 5550 posts Report Reply

  • David Haywood, in reply to Rich of Observationz,

    True as, forgot latent heat. But yes, making the ice blocks in the day and leaving them out at night would work in many climates.

    This was a genuine trick employed for icecube production in colonial India (apparently it was one of the big spreaders of typhoid amongst the elite).

    Dunsandel • Since Nov 2006 • 1156 posts Report Reply

  • steven crawford,

    I've realised what I said about firewood is a bit silly. It's carbon neutral but if everyone heated there hot water with wetback systems, we wouldn't be saving anything. It would a neutral, not an improvement. I have met people who farm firewood for there own use. There have about half an acre tied up for that.

    Atlantis • Since Nov 2006 • 4163 posts Report Reply

  • Moz, in reply to Rich of Observationz,

    If your local substation trips, then a small number of inverters will try and drive all the local loads

    No, no, no, that would be insane and dangerous. I can't imagine anyone certifying an inverter that does what you're suggesting. The idea is that you mechanically switch so you're isolated from the grid and the "island" is your house. Modern inverters all electronically switch, but to get an install signed off you need a separate mechanical switch.

    The mechanical switch is so that electricity and emergency workers can see easily that this is the case, and smite you with fire if you bypass that and back-feed a dead grid (which probably wouldn't work, but you still don't want to be the one holding the wire when it happens).

    My somewhat simpler plan is to use a UPS-style system: grid feeds house, UPS plugs into wall and charges battery, solar also feeds UPS/batteries, I plug stuff into the UPS. Most small off grid systems have a generator input what can also run off a single phase socket, to look at it another way. But there's a couple of companies in Oz doing UPS-sytyle systems for on-grid urbanists like me. Largely as a regulatory hack - in OZ it's almost impossible to get any feed-in payment at all if you have batteries, and almost as impossible to be allowed to buy off-peak power if you have batteries (yes, they are that dumb). But a plug-in system doesn't count (otherwise even a battery backed alarm clock would trigger their "no grid connected battery systems" clause)

    Sydney, West Island • Since Nov 2006 • 1169 posts Report Reply

  • Paul Campbell, in reply to David Haywood,

    This was a genuine trick employed for icecube production in colonial India (apparently it was one of the big spreaders of typhoid amongst the elite).

    I believe the Egyptian Pharaohs got their ice the same way (maybe even their typhoid ...)

    Dunedin • Since Nov 2006 • 2600 posts Report Reply

  • Alfie, in reply to Rich of Observationz,

    If your local substation trips, then a small number of inverters will try and drive all the local loads – which they obviously can’t do, so they’ll go into a trip/restart cycle, which might break stuff.

    As Moz says, that ain't gonna happen. Our solar system is grid-tied and while we have manual isolation switches with bloody great warning signs, an essential part of the sign-off is automatic shutdown whenever the grid fails. We had a six hour (planned) outage last week and our solar simply shuts down until it detects live power from the mains. Then it boots up and resyncs again.

    What Moz is discussing is actually quite cute -- a dual system with mains power wired seperately from an off-grid solar setup charging a UPS. That would also provide a way of getting around the lines companies stupid "solar tax" which the Commerce Commission seems set to approve.

    Dunedin • Since May 2014 • 1360 posts Report Reply

  • Rich of Observationz, in reply to Alfie,

    There has been interest in the electricity profession in enabling islanding (which normally refers to multiple connection points rather than a single house) - e.g. this paper: http://vbn.aau.dk/files/19638822/Publication in order to improve network resilience. I thought that was what you were about.

    However, your idea, which is basically engineering your system to detach it from the grid when the grid fails is perfectly sound. For NZ, it's questionable if the cost of breakers and/or UPSs is justified by the frequency of power failures.

    Back in Wellington • Since Nov 2006 • 5550 posts Report Reply

  • Alfie,

    Substituting battery storage with a large UPS and keeping it seperate from the mains supply was actually Moz's idea, and it's a damn good one. ;-)

    Dunedin • Since May 2014 • 1360 posts Report Reply

  • Ian Dalziel,

    Ice has a rich literary heritage as well
    who can forget the slush the Trask's trainload of lettuces became when their Ice-packed carriages got held up by snow then sidetracked in a Chicago heatwave ( East of Eden, John Steinbeck) ]]
    or Fat Boy the ice machine in Paul Theroux's The Mosquito Coast

    filmed by Peter Weir an acknowledged Ice Wrangler

    Christchurch • Since Dec 2006 • 7848 posts Report Reply

  • Lilith __,

    Attachment

    So, I was just talking about why does everybody not have hot-water-heating solar panels and my sister pointed out that our neighbour does. This is apparently what they look like!

    Dunedin • Since Jul 2010 • 3886 posts Report Reply

  • Lilith __,

    Disappointingly, Consumer says they're not great. Too costly for too little benefit.

    Dunedin • Since Jul 2010 • 3886 posts Report Reply

  • Moz, in reply to Lilith __,

    One point to keep in mind is that most of NZ's population lives in Auckland, so there is a big difference between "most people" and "most land/most towns/most houses". If you restrict discussion of solar to "Auckland and points north" the numbers look much better. Not good, but better.

    why does everybody not have hot-water-heating solar panels

    Because almost all solar water heaters lose energy on cold cloudy days, and much of NZ's land area has those for half the year.

    Now, some pointed remarks. The ideal angle is somewhere steeper than your latitude, so for NZ that means 45 degrees. Which doesn't really go with most rooflines. The one pictured will largely stop working at the start of winter, even on sunny days - it's just not going to collect enough sunlight to be useful. A more sensible setup won't really peak at all - it will heat all the water as hot as it's allowed to, for more than 70% of the year. But for most of NZ that means 2-5 square metres per hundred litres of tank which is ridiculously expensive.

    You want to over-steepen, so the orientation is best in winter and in summer when you more collector than you need the orientation isn't ideal... but that doesn't matter, because 3x the area you need working at 80% of potential... is still 2.4x as much collector as you need.

    There's a circular process at work too - they don't make sense, so there aren't many of them, so there are no skilled, experienced solar hot water system designers or installers, so most installs are sub-optimal, which means the economics are even worse than expected, so people don't install them,

    In Sydney it's the other way round - there aren't a lot of heat pump hot water systems, the ones we have are mostly imported, few plumbers know much about them so it's hard to get one fitted, so few people install them. It's getting better, but it still is not great. But then, we also have the opposite "problem" to NZ - solar hot water systems work well, are cheaper than electric, are not powered by coal, and there are a lot of options from a lot of installers.

    Sydney, West Island • Since Nov 2006 • 1169 posts Report Reply

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