Page 1 of 2 12 LastLast
Results 1 to 10 of 16

Thread: roof top solar arrays and geothermal heating?

  1. #1
    Join Date
    Aug 2013
    Location
    US
    Posts
    108

    Default roof top solar arrays and geothermal heating?

    How prevalent are solar arrays on homes in New Zealand? On one hand I'd think they'd be popular due to the cost of normal electricity, but is this just one more thing that is more expensive in NZ compared to many other places in the world?

    Also, is geothermal heating popular? It's generally expensive to install, but after that it's effectively free.

    Anyone know what the ROI (in years) would be for major green energy systems?

  2. #2
    Join Date
    Apr 2009
    Location
    Sandwich Islands
    Posts
    758

    Default

    Quote Originally Posted by Alistair View Post
    How prevalent are solar arrays on homes in New Zealand? On one hand I'd think they'd be popular due to the cost of normal electricity, but is this just one more thing that is more expensive in NZ compared to many other places in the world?

    Also, is geothermal heating popular? It's generally expensive to install, but after that it's effectively free.

    Anyone know what the ROI (in years) would be for major green energy systems?
    Geothermal heating is very popular (in geothermal areas like Taupo and Rotorua) for building power stations. AFAIKT it is not terribly common for providing electricity to individual homes.

    We looked into putting solar panels on our (existing home); a 17k investment would have taken care of half our power bill...maybe a thousand dollar a year savings. The power companies will buy surplus power back from you, but at about 10 percent of what they sell it for.

    There is no government push for individual solar panel. The government is very much in the electricity business, and as most of their business is already renewable (hydroelectric, geothermal, and wind), there is not much environmental reason for people to put up solar panels.

  3. #3
    Join Date
    Aug 2013
    Location
    US
    Posts
    108

    Default

    ouch, ~17 year ROI... I can see why solar is not popular.

    Geothermal is usually used for direct heating/cooling. It's possible to do in any climate, as the ground temperature 2 - 3 meters down is usually fairly consistent year round.

  4. #4
    Join Date
    Feb 2007
    Location
    Wanaka
    Posts
    293

    Default

    17 year ROI seems pretty damn high - we've just put in a 5kw solar pv system for around the same price and we reckon ROI is 6-8 years. We're sunny down here in Wanaka though for 11 months of the year, and the PV will provide power for our house and also the bore pump for the vineyard. Genesis buy back the electricity at a decent price too.

    Maybe we just use less electricity than most people

    it makes you feel righteous too...but it'd be nice if there was some (no matter how small) incentive from the government to go greener.

  5. #5
    Join Date
    Jan 2007
    Location
    Chch, NZ
    Posts
    2,226

    Default

    Yes 17 years seems high and 6 - 8 years seems far too low. This website below says about 11 years.
    http://www.ecobob.co.nz/EcoArticle/2...x?PageNumber=5

    Posters there also claim huge limitations on a 4kW install that it won't meet the needs of the typical home. That is, good luck roasting a turkey in the oven. 4 or 5kW figures are only at peak maximum / most idea conditions. Likewise with the manufacturer's claims of constant output over the 10 or 20 years time as no one would be able to claim the warranty.

    As for geothermal, there's a lot of that in the Rotorua area (N. Island). But winter time isn't that harsh there so heating requirements would be minimal. Such energy sources is better served to be in the S. Island. Speaking to an ex-Rotorua council worker, I remember him saying it's difficult to get a consent to build a house on geothermal as the greenies have discovered the use of geothermal does affect the ground temperature and the ecology.

  6. #6
    Join Date
    Aug 2013
    Location
    US
    Posts
    108

    Default

    Quote Originally Posted by Super_BQ
    As for geothermal, there's a lot of that in the Rotorua area (N. Island). But winter time isn't that harsh there so heating requirements would be minimal. Such energy sources is better served to be in the S. Island. Speaking to an ex-Rotorua council worker, I remember him saying it's difficult to get a consent to build a house on geothermal as the greenies have discovered the use of geothermal does affect the ground temperature and the ecology.
    Geothermal to provide all heat (~20C) obviously requires being close to a heat source such as Rotorua. However, below ground temps (~10 m+) are usually around 13-14 C in most places. Thus, if it is colder than that outside, you can get free (ignoring pump energy requirements) heating up to the 13-14 C level. Yes, there will be a heat exchange below ground, but over a large enough area, that is usually not a problem. You will have to supplement the 13-14 C to get to your desired temperature, but it's better than using supplemental heating to go from <<13 C to ~20C. Thus, geothermal heating/cooling is viable in many locations.

    As an extreme example, in northern Greenland we considered geothermal cooling (yes cooling) because the ambient air temperature would occassionally hit ~15+C. We used ambient air to cool our equipment, which became a problem at high temperatures. Problem with sinking pipes into the ground (besides the difficulty of actually getting them through the rock hard permafrost), was that you could melt the permafrost and thus cause the land to sink. General solution for buildings that must be built on a foundation, rather than raised above the permafrost, was to have foundation cooling. This consisted of large diameter pipes that went under the foundation. During the summer, air would be allowed to flow through the pipes, cooling the foundation and surrounding ground. In the rare instance this failed to work, the building would begin to sink into the ground. The solution we looked at (in addition to the foundation cooling) to get around the permafrost issue was to build a large mound of dirt above the ground. Goal was to run pipes through this mound vice below ground. Not as efficient, but far less likely to cause a permafrost issue.

    At the opposite extreme, Spaceport America in southern New Mexico has a cooling system that uses a series of tunnels just below ground level to cool incoming air. Even if it is 30+C outside, the incoming air will be cooled to ~15C.

    I'm no expert, so I'll defer to someone who really knows what they are talking about.

  7. #7
    Join Date
    Apr 2009
    Location
    Sandwich Islands
    Posts
    758

    Default

    Quote Originally Posted by Super_BQ View Post
    Yes 17 years seems high and 6 - 8 years seems far too low. This website below says about 11 years.
    http://www.ecobob.co.nz/EcoArticle/2...x?PageNumber=5

    Posters there also claim huge limitations on a 4kW install that it won't meet the needs of the typical home. That is, good luck roasting a turkey in the oven. 4 or 5kW figures are only at peak maximum / most idea conditions. Likewise with the manufacturer's claims of constant output over the 10 or 20 years time as no one would be able to claim the warranty.
    That website uses a lot of clever math to get to 11 years.

    Part of the payback comes from increased home value--but they are using data from the US...I have serious doubts that the average Kiwi buyer is going to see solar panels and pay more accordingly. Everyone would have insulation and double glazed windows if this were the case.

    The website uses a 3.5% increase in annual power costs; assuming this increase is correct over the next 10 years, couldn't I bank the money and (more than) offset the increase with interest on a savings account?

    My quick read through didn't see any mention of selling power back to the grid. If you use most of your power when the sun is up, the figures come closer to working out; maybe it varies by region, but in Hawke's Bay, only 2 power companies will buy home generated power. Neither came close to buying it at the same rate they sell it at. So although a 3KW system can generate 4.2 KW of electricity per year, the average person would not realize full benefit.

    Aberdian, have your calculations been as good as promised so far? It doesn't get much sunnier than Hawke's Bay; we really would like to put in a system if it made any sort of financial sense.

  8. #8
    Join Date
    Jan 2007
    Location
    Chch, NZ
    Posts
    2,226

    Default

    The website uses a 3.5% increase in annual power costs; assuming this increase is correct over the next 10 years, couldn't I bank the money and (more than) offset the increase with interest on a savings account?
    I think banks now are paying 4% for 1 year on deposits. But if you minus the with-holding tax, it would be a lot less than 3.5%. Power prices have kinda sky rocketed in the past few years (at least, here in Canterbury region). Last year they hiked it up some 12% and this year they're talking another stellar price rise. Without a doubt, after the NZ gov't is finished selling off these power companies, expect higher electricity prices again (as shareholders will demand more profit maximisation). But from what i've been hearing, the RBNZ is signalling that OCR lending rate will go up significantly next year. So term deposits won't be 4% but maybe 6 or 7% in the coming 2 or 3 years.

    My quick read through didn't see any mention of selling power back to the grid. If you use most of your power when the sun is up, the figures come closer to working out; maybe it varies by region, but in Hawke's Bay, only 2 power companies will buy home generated power. Neither came close to buying it at the same rate they sell it at. So although a 3KW system can generate 4.2 KW of electricity per year, the average person would not realize full benefit.
    If selling power back to the grid is such a huge barrier (to get fair pricing), then there's not much point in using PV on urban homes. But for the homes that are remote / rural and where the grid is not available - PV makes complete sense. As an example, my uncle in Auckland had installed a large PV array last year. At the time it was not connected to the grid as it required compliance (it's not simply connecting a couple of wires to the meter box). But what the power company was willing to pay him per kW/Hr was so measly that he told me they were better off to use the power direct from the panels; in times like when they cook dinner. My thoughts were, that's a lot of $ spent just so you can use less grid power during dinner time (while it sits on the roof for the most part of the day).

    The other aspect is the PV panel can power the electric heating of the hot water tank. My thoughts to this is you're better to use solar hot water tube/panels to heat the hot directly from the sun, rather than to have efficiency losses by converting DC to AC power.

  9. #9
    Join Date
    Aug 2013
    Location
    US
    Posts
    108

    Default

    Quote Originally Posted by Super_BQ
    The other aspect is the PV panel can power the electric heating of the hot water tank. My thoughts to this is you're better to use solar hot water tube/panels to heat the hot directly from the sun, rather than to have efficiency losses by converting DC to AC power.
    Solar hot water panels are probably the simplest to install and maintain.

    In my book, the ideal design would use PV for electrical devices and some sort of heat pump for heating. Given all the USB powered gadgets people seem to have these days, it would make sense for a limited set of DC wiring from a PV system (if you instal when you build), thus avoiding the DC-AC-DC conversion losses.

    That being said, PV prices are dropping and the technology is changing so rapidly, I'm not sure it makes a whole lot of sense to buy a PV system at the current time. They just hit 47+% efficiency on a new type of PV cell; not that I'd expect to see that commercially available for 10-15 years (they are usually more exotic materials and not necessarily scalable). In the US, leasing PV seems to make a lot more sense. One company offers zero up-front cost and leases you panels. You won't save as much money, but you have zero out of pocket expenses. Plus, given all the talk I've seen about windy Wellington and other areas, it seems like wind might make more sense, if you are allowed to do so on an individual home.

  10. #10
    Join Date
    Feb 2007
    Location
    Wanaka
    Posts
    293

    Default

    Quote Originally Posted by 72andsunny View Post
    Aberdian, have your calculations been as good as promised so far? It doesn't get much sunnier than Hawke's Bay; we really would like to put in a system if it made any sort of financial sense.
    They've only been in a couple of weeks so all we have to go by is the word of the installer (who is a family friend so hopefully he'll not lie too much) and my back of a fag packet calculations - luckily the two methods seem to come up around the same value, installer says payback in 7 years, my numbers reckon about 8. Bear in mind that we'll be a net exporter to the grid based on our usage pattern and the size of array we've put in.

    Looking at our numbers, we'll only have a deficit in June and July when the inversion layer is in and the sun's hidden - not a huge one, we don't have heat pumps or electric ovens to run and the vineyard bore is switched off so it's just appliances and lights etc.Bear in mind that I tend to be VERY conservative when it comes to numbers, I'm reasonably confident(ish) that I've got a good handle on how much power we should be producing......ask me in a year if that's true!!

    Apart from the money, the great thing about it is that it makes me feel righteous....

Page 1 of 2 12 LastLast

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •