[westi]

... and if so, what do you think of it ?
We have to replace our old electric water cylinder and have been advised to change to gas, but thought i'd find out about solar first.
Any thoughts ?

[Super_BQ]

The house we live in is 2 years new. It was fitted with a Bealey (Australian brand) hot water solar system. Price tag was around $8000 for the 2 solar FLAT panels, heat exchange, & 360 Litre hot water tank. ALL ON THE ROOF outside.

I can't say i'm impressed with this system. I've heard others having much better luck with the cheaper China made vacuum tube hot water panels and modular to boot! My uncle told me that he's talked to an expert up in Auckland (teaching at AKL University) and he's found that the flat panel vs vacuum glass tube offers no real difference in performance.

I beg to differ. I think the old fashion flat panels have to be angle tilted towards the sun while the vacuum tubes ones aren't as so critical to the angle of the sun light.

My uncle also said that ideally, you need 1 panel for each person living in the house. So if you have 4 people living, you need 4 panels - for Auckland climate.

The advantage of the Bealey solar system is the heat exchanger allows for below 0°C frost. The possibility that the water in the panels will freeze up and permanently damage the panels during the cold Christchurch winters.

I don't like the idea of having the hot water tank outside. The hot water has to compete with the cold temperature outside so the energy lost can not be gained ie. having a hot water tank inside the house, the loss in heat transfers within the house (not lost outside in our case). However, this system requires no use of an electric pump - so purely maintenance free.

BQ

[westi]

Thanls for your reply Super BQ. That gives us some thing to think about. At this stage I'm thinking it's too expensive for us to install as we also need to replace the cylinder.

[Moorf]

We had our hot water cylinder replaced a few months back and it cost $1200 including labour, fitting and all the hardware...

We have such huge rooves here that we're also considering solar but we haven't delved in to it much so far (and after this summer we may rule out solar altogether!!) :roll

[Rizak]

Given the chance, we may go with a tankless system for instant hot water.

http://www.tanklesswaterheaters.com/lib/lowenergysystems/paloma-ph16fs-sm.gif

They come in both electric and gas. You don't pay to keep a tank full of water hot all the time. You never run out. You do have to watch that you aren't washing the dishes and a machine full of clothes and taking a shower all at the same time, but for the two of us it should be just fine.

[Trigirl]

thats what we've got for our house (a gas one)

[Moorf]

We had one in the UK and found the water pressure a problem at first but had additional pumps fitted where necessary.

[renew]

Hi,
Solar water heating would be good to reduce the fuel bills, you would still require a secondary heater. The amount you will save will depend on how much hot water you use and the orientation of your roof. It will also depend on the system that you buy. Expect to get more hot water from an evacuated tube system that from flat plate, though flat plate systems are usually considerably cheaper to buy.

If you are looking to reduce your heating bills (or your CO2 emmisions) then you may want to consider spending money on insulation if you have not already done so rather than on solar water heating.

good luck

[andrewandjane]

hi ,

i currently work for an energy company in the uk advising clients on energy systems from a renewable energy point of view, cant say how it is out there as not there for another few weeks...

BUT in the UK evacuated tubes perform significantly better as they dont loose heat because of the vacuum wheras the flat plates loose some and dont perform at all well in winter (here in uk) the evacuated tubes perform very welll in summer and still produce useull heat in the winter and dont actually need direct sunlight as willstill collect some solar radiation through the clouds and as the collected heat cant be lost they are still usefull.

IN short my advice for UK is dont get flat panels but get evacuated tubes, i presume this advice would be similar to NZ in terms of just performance of panels not taking climate difference into account.

average house and family in cold uk climate needs two panels of evacuated tubes.

hope this helps.

[Super_BQ]

I must be getting some mis-information but my feeling is that the academics (my uncle and that dude from AKL uni) hasn't gone to comparing "real world" conditions. Probably a typical lab room result. Though I did hear him say that it has something to do with the clouds in the sky - perhaps NZ has more clouds throughout the year which means the the vacuum tube ones don't catch as much light?

If freezing was ever a problem, I would seek advice from my friend back in Canada that showed me their hot water solar system. The vacuum tubes are lined with a "fire-wire" which is temperature controlled. Whenever the temperature outside drops below 0, small amount of electricity is used just to keep the tubes safe from ever cracking. I'm sure the Beasley system using a heat exchanger is far from efficient as this Canadian variant unless they were thinking of huge gains without the use of a pump?

Hot Water on Demand? When my uncle built this house (not the other uncle that advised to use the Beasley) thought of a hot water system like this. But again the laws of physics apply. There is no way you can get enough hot water to service the house under 'single phase' supply. The limit being just under 3HP or 2.2KWs continuous load. You can get a lot more under 3 phase supply but the majority of homes in NZ are wire feed only single phase.

Problem? Imagine this. How long does it take for 1 cup of water from the tap to heat up in the microwave? 1 minute? A good microwave can do 1KW of power of heating. So even we operated at the max. Kw supplied (2.2Kw), it would still take 30 seconds to get the water hot. But, if a hot water tap can flow 2 or 3 litres of water less 30 seconds, there's simply no way these devices can do it. Unless we're talking about small slow flows of warm water from the tap?

BQ

[Rizak]

Well, I've never used one myself ... but I'm sure someone is going to chime in here any minute to correct you.

Someone? Anyone?

[Mr TW]

http://www.solarsmarter.org.nz/ is the new website that has been launched to promote solar energy in NZ

[renew]

the major difference in evacuated tube and flat plate is down to the better thermal insulation of the precious hot water with a vacuum tube as opposed to flat plate. Especially important for windy areas. For those of you who are Excel minded you can use software which is freely available from RetScreen to do some calculations. The solar thermal database has a number of systems and the performance. You can also work out the financial aspects as well as performances.

http://www.retscreen.net/ang/home.php

their documentation is also very good


http://www.retscreen.net/download.php/ang/120/0/Textbook_SWH.pdf

[Croft]

the major difference in evacuated tube and flat plate is down to the better thermal insulation of the precious hot water with a vacuum tube as opposed to flat plate. Especially important for windy areas. For those of you who are Excel minded you can use software which is freely available from RetScreen to do some calculations. The solar thermal database has a number of systems and the performance. You can also work out the financial aspects as well as performances.

http://www.retscreen.net/ang/home.php

their documentation is also very good


http://www.retscreen.net/download.php/ang/120/0/Textbook_SWH.pdf

An excellent resource, thank you very much renew - not only solar heating but other alternatives such as GSHPs.