Hard News by Russell Brown

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Hard News: Going solar?

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  • David Haywood, 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 • 1156 posts Report Reply

  • David Haywood, 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 • 1156 posts Report Reply

  • James Green, in reply to Hebe,

    I remember this article: I bored Beloved senseless about it. Where can the systems be obtained?

    I bought ours from a napier company ($425 incl freight)
    http://energydrain.vaportec.co.nz/
    However, you should probably also read David's comments re: mounting and the inner surface, as on closer inspection, it does seem like this one does have a slightly irregular inner surface, but can be installed in a more horizontal position.
    The (better?) gravity film ones are more expensive and can be sourced here
    http://www.quadrix.co.nz/79.html

    Dunedin • Since Nov 2006 • 703 posts Report Reply

  • James Green, in reply to David Haywood,

    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

    As you'll see above, not strictly gravity film, and and at least some very mild corrugations to induce turbulence, which enables it to be installed in a near horizontal position. And we will be installing near horizontally. The current shower waste is all copper(!), but given what you've written, I think I'll get the plumber to put in a Y regular joint, and use the straight access for cleaning. Will update once installed!

    (PS - thanks for the advice! get well soon)

    Dunedin • Since Nov 2006 • 703 posts Report Reply

  • Farmer Green,

    "Old" technology I know, and perhaps more useful for those who can grow their own renewable energy i.e. trees, but a decent second hand wood stove will cover all cooking , house heating , (radiators) and hot water for washing needs, of a large household.

    The only problem might be the life expectancy of such a system . . . 50-100 years.
    Still , good value for the money.

    Lower North Island • Since Nov 2012 • 778 posts Report Reply

  • Bart Janssen, in reply to Alfie,

    Power companies have imposed a moratorium on new solar connections and want to impose a fee on people with solar installations of around $120 a year. In Arizona the PowerCos tried to impose a $50 per month “penalty” on solar powered houses

    This is just the free market system at the stupid extreme. It makes perfect sense for the power company to try and increase its profits - that includes using political pressure to hamstring competitors. It isn't evil as such just "good business" - bearing in mind that's all they've ever learned.

    Stepping back and considering the good of society as a whole is an utterly alien concept and very very hard for them to grasp.

    So while it's worthwhile recognising the sillyness of their actions, heaping scorn on them is not worthwhile.

    Auckland • Since Nov 2006 • 4460 posts Report Reply

  • Jason Kemp,

    I’m late to this conversation but just in case it is still useful I wrote a few blog posts about solar power in NZ back in Feb/ April last year Is Solar Power for Home Practical for NZ?

    I wrote a series of posts at the time and some of it may be dated but the ability to use much less power in the summer is a great thing for most people.

    The quick summary is that if you can do the water heater AND some PV AND you are connected to the grid there are some real savings to be made. The priority is for most households hot water heating so sort that first and then do PV if you can.

    PV panel pricing is about as low as they will go now. Ideally you would want to be connected to the grid as that gives you a storage option.

    One of my brothers has a wind powered generator and whole container shed full of batteries & other tech which at the time cost close to $50k but since it was more than that to connect to the power on his rural property was still worth it. The point for most people though is if you are on the grid then you avoid all of those hard storage related costs.

    Your hot water cylinder is a store of sorts and so making sure it is the right size / fit for purpose may be part of the investigation. Given that power pricing is going up each year there will be a tipping point for most people between 5 & 10 years where they have paid off the bulk of their solar costs and are partly protected against future price rises for any extra power they use.

    If you happen to be building new check out the zero energy house project in Pt Chev, Auckland That house combines solar water heating, solar tiles and other smart design features like LED lighting and a specific design approach to minimise energy usage / maximise light and heat from the sun etc.

    What impressed me about the zero energy house project was that owners had taken extra care to measure everything about their energy usage and that makes the house an exemplary example for the building industry.

    I also saw a few weeks ago Warren Buffett going large on Solar and promising to double his investment in that sector to something like $15b which in the US is small but it is a clear signal to market of some kind of tipping point for investors there ( and elsewhere.)

    Buffett ready to double solar, wind bet

    For Russell – Shay Brazier & Jo Woods are very close neighbours of yours and it would be worth a chat with them about the zero energy house if you haven’t already done that.

    what power crisis is a local (Auckland) company who have done many of the residential and larger PV projects over the last few years. Their 2Kw residential system is down to $8,995 which is very similar to what it was back in April 2013 when I first looked at their systems.

    Most houses would want / need more like 4-5kw systems which are also priced in that link.

    Auckland • Since Nov 2006 • 368 posts Report Reply

  • Lucy Telfar Barnard, in reply to Farmer Green,

    a decent second hand wood stove will cover all cooking , house heating , (radiators) and hot water for washing needs, of a large household.

    The only problem might be the life expectancy of such a system . . . 50-100 years.
    Still , good value for the money.

    We used a wood stove through my childhood on the commune. The only problem being life expectancy is only the only problem if you're time rich. Apart from the additional maintenance and cleaning (compared to an electric or gas cooktop/oven), they're not much chops for coming home at 6.30pm and whipping up a quick dinner in 15 minutes or so for the tired hungry troops. The fire needs to be stacked, and lit, and coaxed (if it's winter). And you can forget about whipping up a quick batch of muffins before your short-notice guests arrive, as it takes a lot longer for the oven to warm up, and keeping it at the required temperature to bake takes more input as well.

    I love wood stoves, but they suit my country life, not my city life.

    Wellington • Since Nov 2006 • 585 posts Report Reply

  • Lucy Telfar Barnard, in reply to Farmer Green,

    a decent second hand wood stove will cover all cooking , house heating , (radiators) and hot water for washing needs, of a large household.

    The only problem might be the life expectancy of such a system . . . 50-100 years.
    Still , good value for the money.

    We used a wood stove through my childhood on the commune.

    The only problem being life expectancy is only the only problem if you're time rich.

    Apart from the additional maintenance and cleaning (compared to an electric or gas cooktop/oven), they're not much chops for coming home at 6.30pm and whipping up a quick dinner in 15 minutes or so for the tired hungry troops. The fire needs to be stacked, and lit, and coaxed (if it's winter). And you can forget about whipping up a quick batch of muffins before your short-notice guests arrive, as it takes a lot longer for the oven to warm up, and keeping it at the required temperature to bake takes more input as well.

    I love wood stoves, but they suit my country life, not my city life.

    Wellington • Since Nov 2006 • 585 posts Report Reply

  • BenWilson, in reply to Lucy Telfar Barnard,

    Don't forget all the wood collecting, chopping and stacking too. You probably should have a decent chainsaw unless you're really handy with an axe.

    Auckland • Since Nov 2006 • 10655 posts Report Reply

  • Lucy Telfar Barnard, in reply to BenWilson,

    Not forgotten by any means (collecting brush and wood, breaking and splitting kindling were all part of my chores as a child), though if you don’t mind spending the money you could get round some of that by buying your wood pre-split. Though of course that eats into the savings.

    Wellington • Since Nov 2006 • 585 posts Report Reply

  • Farmer Green, in reply to BenWilson,

    But don't forget that those planting trees at a steady rate have older trees which have to be used . Not to mention the odd wind-blow.
    And of course communities are far less common than they once were ; a lot of social capital has gone down the drain in the last 50 years.. But family farms remain as the type of sustainable community where firewood harvesting is a low-key social activity which provides employment, as well as renewable energy on top of the straight production and amenity values.

    Lower North Island • Since Nov 2012 • 778 posts Report Reply

  • Farmer Green,

    In the first decades of the third millennium, notions of household self-sufficiency , in anything, seem quaint.

    Lower North Island • Since Nov 2012 • 778 posts Report Reply

  • Steve Barnes, in reply to Farmer Green,

    In the first decades of the third millennium, notions of household self-sufficiency , in anything, seem quaint.

    And this entire thread seems almost 90s.
    Less than 20K
    2kw PV panels
    60 amp Mppt controller
    4.5kw Inverter/Charger
    400 Ah Lithium iron phosphate battery stack (600x400x800mm) @ nominal 55 volts (54-58 @ 75-100% charge)
    5.2 Kva diesel generator (for long cloudy periods, run for 3-4 hours a day (3 ltrs diesel) )
    On demand Gas hot water with solar preheat.

    To connect to the grid would have been 40K soo.. no brainer.

    Peria • Since Dec 2006 • 5521 posts Report Reply

  • James Green,

    So I think in the public interest, I might invest in a bit more plumbing (so I can bypass our drainwater heat exchanger), and update with some data, both on how much money is saved, and how much efficiency is reduced through fouling.

    Dunedin • Since Nov 2006 • 703 posts Report Reply

  • steven crawford, in reply to Lucy Telfar Barnard,

    I love wood stoves, but they suit my country life, not my city life.

    Same here. But I did put one in for my city life. Cost an absolute fortune.

    Atlantis • Since Nov 2006 • 4414 posts Report Reply

  • BenWilson, in reply to steven crawford,

    Cost an absolute fortune.

    What? You didn't forge it yourself? You soft city slicker.

    Auckland • Since Nov 2006 • 10655 posts Report Reply

  • Hebe, in reply to steven crawford,

    Reading the Ecan clean heat appliance regs, it seems that we could put in a wood-fired wetback cooker with radiators in a new build. Which would then be close to my ideal system: wetback/solar PV and running radiators off that and no grid connection.

    Christchurch • Since May 2011 • 2899 posts Report Reply

  • steven crawford,

    What? You didn’t forge it yourself? You soft city slicker.

    We chose a fabricated steel rather than cast iron model. The townie council wouldn’t let me do a homemade job. Now that we have the stove dimensions (and documents) I can fabricate a replica.
    Don’t tell anyone;-)

    Atlantis • Since Nov 2006 • 4414 posts Report Reply

  • steven crawford, in reply to Hebe,

    Here, this is the most reasonably priced machine I found. These modern wood stoves make the old clunkers I grew up with seen like the Austin A55 compared to the Datsun 120Y.

    There is this the Bentley of NZ made wood stoves. These, last I know, are manufactured at the old money factory in Whangarei. The people I know that live next door to there, grow there firewood on half an acre. I don't remember tree breed, but they worked a two year pruning turnaround.

    Now for my own plug. I am a fabrication engineer, which required six mouth linguistics training at the polytechnic. But, I also hold a BA in applied arts, which required me learning how to read and write. So, If anyone is interested in setting up an elegant aesthetically pleasing, wood powered radiator system, or any other metal craft project--- Linda and I, run a cottage industry, to serve your dreams and aspirations. Email:)

    Atlantis • Since Nov 2006 • 4414 posts Report Reply

  • Worik Stanton, in reply to Russell Brown,

    I have a friend who has both. Installed the hot water system first and a year later installed the PV. Says now doing it again he would not have installed the hot water system.

    Do the research. Price the PV system. Watts per square metre hot water will be better. Dollar per watt, it may well be PV

    Otepoti • Since Nov 2007 • 41 posts Report Reply

  • Hebe, in reply to steven crawford,

    Grumble grumble bloody Ecan. I like those stoves. Filed thanks.

    Christchurch • Since May 2011 • 2899 posts Report Reply

  • Shay Brazier,

    Hi Russell, and other commenters

    Russell your question has received a lot of great answers. If I can add one more hopefully useful view and share our lessons from the Zero Energy House. At the zero energy house we assessed the solar on the basis of savings vs increased mortgage cost.

    For Solar water heating:

    A solar hot water system of around 4m2 (2 x 2m2 panels) might generate around 2200kWh of hot water per annum, at $0.22/kWh this is a saving on your power bill of $485/a. At $7360 it would cost around $575/a to repay the additional mortgage a repayment over the same period as the system life of 25 years, at 6%/a interest. Where energy prices go up at 3% per annum you have saved more money than your repayments (including interest) after 8 years. The obvious risk is that the interest rate goes up. The nice thing about an agreed repayment plan with Nova perhaps, or though it is a little hard to see how your power bill will less when you are saving much less than $123/month.

    For Photovoltaic:

    A typical 4kWp system would probably generate 5,000kWh/a, and might cost around $12,000, at the same mortgage terms as above the repayment cost is around $940/a. Assuming you manage to use 25% of the energy generated directly in the house, and export the rest you would avoid paying $264 for imported energy and be paid $446 for exported energy, a saving of $910/a, (assuming an export tariff of $0.17kWh and import price of $0.22/kWh). Where energy prices go up at 3% per annum you have saved more money than your repayments (including interest) after 2 years. There are 2 obvious risks here, 1) interest rates go up, 2) export price goes down.

    There are of course a few other questions to consider including:
    - The quality and longevity of the system components and installation
    - The energy tariffs you are currently on and how it changes over time
    - If you sell your house are the buyers willing to pay you more as a result of the solar hot water system to allow you to recover the invested money if this hasn’t already been recovered from the savings
    - How long will there be 4 people using hot water, as reduce hot water usage, will reduce your savings.
    - Are there other technologies to consider such as hot water heat pumps, and could these be combined with one of the technologies above

    I’ll leave you to work out if these figures apply to you, and draw your own conclusions. Do drop us an email via the Zero Energy House if you want to discuss more, or wanted to drop in for a coffee some time.

    Pt Chev • Since Jul 2014 • 1 posts Report Reply

  • Brent Jackson,

    With respect to instant hot water from electricity, when we put in the Solar Hot Water System, we looked at getting an electric instant hot water for the kitchen sink (because it was as far from the roof HWC as possible). What I wanted was a thermostat regulated one that I could put on the Hot Water pipe that would heat the water to the required temperature, so once the water sitting in the pipes had drained through and the water from the cylinder started arriving, the electric instant hot water wouldn't be doing much any more. Unfortunately, I couldn't find any product that worked like this. All of them seemed to assume a cold water feed, and heated for a fixed time to give an approximate output. So I did the math and wasting the 5 litres of water in the piping and then using the Solar hot water, was much better than using electricity to heat cold water. In point of fact, the water is not wasted, as we use it to rinse things off before we start the dishes anyway.

    I also wanted the hot water pipe connected to the dishwasher, but the plumber talked me out of it, and stated that it would invalidate the warranty. I still regret that I wasn't more forceful about it. Has anyone else ever connected a hot water feed to the dishwasher ?

    Auckland • Since Nov 2006 • 619 posts Report Reply

  • Lucy Telfar Barnard, in reply to Hebe,

    Grumble grumble bloody Ecan

    Not just Ecan, it’s the whole MfE list system I have issues with. The best that any woodburner on their list can claim is that it’s not quite as ugly as most of the others. Being a pyromaniac, I want a small woodburner for my city life, for aesthetic purposes rather than heating necessity. Because I want it for aesthetic purposes, I want it to be pretty, or cute. To be precise, I want it to be this: http://www.stovesessex.co.uk/wp-content/uploads/DovreVintage30Enam.png. According to Norwegian testing standards, it meets our requirements for efficiency and emissions. But New Zealand doesn’t accept foreign testing standards, because… our wood might be different. Or foreign stoves might be dangerous in wood-framed houses. Or some other excuse for protectionism. Getting it tested to NZ standards would be over $10K, which is well outside the budget. So all I can do is sulk, and rage to anyone who will listen (or read. Thank you for reading.)

    Wellington • Since Nov 2006 • 585 posts Report Reply

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