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The Best Solar Hot Water System - Is It Available?

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Started 11 months ago by mick_queensland
Latest reply from Greg C

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mick_queensland
Member

Hi All,

Maat, one thing to note about tilting to the optimum winter angle, yes, you maximise your winter solar insolation and production, but you need to ensure your system is designed for the winter level of insolation at your location. Depending on your local weather you may want to round up or down on the size of the collector you choose. What I mean by weather is, what is the normal level of cloud and rain at different times of the year. Just see what hamish and kesa have said here to see how clouds can ruin your day. Thats something that not all suppliers and installers would look at. Perhaps some weather research for your locale.
cheers, Mick

Posted Wednesday 22 Jun 2011 @ 2:01:11 pm from IP #
kesa32
Member

Mick , l think most suppliers and installers look at solar products as an add on bonus , as in it will make a difference , but not many tick the boxes when it comes to optimization of a system , as in sizing and tilting etc , they will if your roof is flat etc , but otherwise "she'll be right" is what most people cop .
In sunny qld , yes definately get it right as you'll kick goals with the right size system , be it HW or electric .......down here it's a struggle sometimes lol ( even had the headlights on driving home at 3pm )

Posted Wednesday 22 Jun 2011 @ 8:03:57 pm from IP #
mick_queensland
Member

Hi guys,

I have been quoted on

1. A system that has 30 wet evac tubes, 350 litre non pressurised tank with copper tube heat exchanger, stainless tank inside and out, no govt payouts, install by my plumber. Cost Approx $1600 then add install and freight. (still waiting in definite quote)

2. A system that has 30 heat pipe evac tubes, 260 litre mains pressurised tank, stainless tank inside and out, frame to tilt to 32 degrees unless I modify it (which will negate warranty I should imagine), fully approved with govt payouts ($1600) and 29 STCs, install by my plumber. Cost Approx $4260 less handouts = $2060 then add install and freight.

Freight on both very similar to my place. So the price difference between approved and unapproved is about $500. I will post again with proper quote on wet tubes and low pressure tank.

The Quest continues!
Cheers, Mick

Posted Saturday 25 Jun 2011 @ 1:08:59 am from IP #
amun-ra
Member

what does the local plumbing inspector think of the unaproved system when your plumber gets the inspection done after install. Doing it by the book so an even playing field for all systems what will it cost for you to get local council approval. Ring the council ask the questions then add this cost to your unaproved system ??????? will be interested in the results. Also with the low pressure tank how will the water get to the taps with enough pressure to satisfy the WAF

Posted Saturday 25 Jun 2011 @ 1:50:13 am from IP #
swanning_it
Member

Mick, I'm only mentioning this in case you don't know, but HWSs are not just required to be approved for rebate purposes, but also because they are a prescribed appliance under Qld (and other state) legislation. Without looking into it too deeply, if your proposed unapproved units have boost (electric or gas) they must be certified by a NATA registered laboritory and registered for sale or they are illegal, which in turn has insurance (not to mention perhaps health and safety) implications.

Posted Saturday 25 Jun 2011 @ 2:17:57 am from IP #
Anonymous
Unregistered

Solar water heating (SWH) systems comprise several innovations and many mature renewable energy (or SHW Solar Hot Water) technologies which have been accepted in most countries for many years. SWH has been widely used in Greece, Turkey, Israel, Australia, Japan, Austria and China.

In a "close-coupled" SWH system the storage tank is horizontally mounted immediately above the solar collectors on the roof. No pumping is required as the hot water naturally rises into the tank through thermosiphon flow. In a "pump-circulated" system the storage tank is ground or floor mounted and is below the level of the collectors; a circulating pump moves water or heat transfer fluid between the tank and the collectors.

Posted Saturday 25 Jun 2011 @ 7:08:29 am from IP #
mick_queensland
Member

Hi

swanning-it, I asked that question in my last mail to the supplier. I asked if it was certified to be installed in Queensland (the supplier is in queensland too). I know my plumber would not install it if it wasnt certified. I also asked about frames and the definitive price of the larger system. Its the weekend now so I guess I will not hear til the weekdays. When I said unapproved previously, I meant that they are not approved to get the govt handouts. I will post when I know more.

amun-ra, the water in the tank is un-pressurised, but, there is a copper tube heat exchanger which is at mains pressure running through the tank. I feel there are significant advantages to this idea, however, an important point to know is how efficient your heat exchanger is. This is easily measured and should be defined and listed in the advertising. I have asked for the details as they were not in the advertising. I will post when I know more.

cheers for the advice, always good to get warnings etc.
Mick

Posted Saturday 25 Jun 2011 @ 2:50:51 pm from IP #
Johnnojack
Member

Re frames the ones we used were designed to lift from 0 deg to 30deg. You could use them on a 30deg roof to make 60deg but it would have the back verticals leaning forward, ahh more ugly. Also the tank on roof system are only designed for up to about 35deg, beyond that the tank needs extra restraining, which is usually a couple of steel straps tekked to the tank skin and fixed back to the roof, hmmm.
Mick what you are describing above is a bit like mine. I had to do it all myself as the plumber didn't want to know about it. He installed the instant gas and left me to it.

Description: 305 litre open vented copper tank on steel pole and frame in roof space. 4 large Solahart sized panels thermosyphoning to tank angle 30deg on north roof. Why 4 panels, well at $50 each why stop at two. Yes they are used but still good. No electricity connected to tank. Mains water (actually rainwater) passes through heat exchanger made from 25m of 12mm copper pipe coiled up in top of tank. Warmed/hot water exits heat exchanger and temp is topped up if necessary by a instantaneous gas heater which is used from mid May to early September. The remainder of the year there is enough hot water or too much. Over heating is addressed in part by removing insulation batts from the top of the tank leaving the bare copper. This is easy to do as I can access the tank via a door at the top of the stairs. The water in the tank is not used and does not need to be potable, it needs topping up from time to time to make up evaporation loss.
Disadvantages: 1.gas instant heater is sometimes confused by having to lift temp from 38 to 42deg for a shower. 2. Heat exchanger delivers a few litres at high temp then as the top of the tank cools temperature drops, in short it is not nearly as efficient as using stratified hot water from the tank itself. However I have no desire to have gravity hot water. 3. Could improve by inserting a larger heat exchanger ie tank but this could be considered a HWS in its own right and may not always reach safe temperatures for a storage tank. 4. Needs a bit of management from the user.

Posted Monday 27 Jun 2011 @ 12:57:51 pm from IP #
mick_queensland
Member

Hi All,

Evacuated Tubes:
while researching I came across a broad statement that Evacuated Tubes tend to lose their vacuum after 10-15 years.

What do you guys think? Does anyone have any experiences with this occurrence?

I can maybe see how that may happen depending on how the tube is constructed, and since I havent actually seen the tubes personally, I dont know.
It does worry me though, that you may have to replace your tubes after 15 years, that takes a lot of the advantage out of the system.

Heat Exchanger:
Also, I was reading the SHW Installation Book which is a Solar Water heater training Course, and it mentions in there about the efficiency (in broad terms) of heat exchanger coils in hot water tanks. As I thought, they are not very efficient and can usually only output about 12-15Lt/Min of water about 10°C lower than the tank temp.
(nb: to find the manual online search for "SWH_Installation_book_online.pdf" )

So essentially you are losing about 10% efficiency of your system by using the copper coil heat exchanger (in very rough terms) Thats not too good.

May be re-thinking my whole premise here.

Cheers, Mick

Posted Wednesday 29 Jun 2011 @ 2:33:33 am from IP #
mick_queensland
Member

Hi JJ,

thanks for the post, very interesting. I like your use of second hand panels, great money saver. I know someone else that did that and they are really happy with their system. However, this has a really low WAF for me and so I need something that looks like its worth the 2-3 grand its going to cost. Your experience with the heat exchanger confirms what I read in the Solar Water Heater training manual. How long is your heat exchanger tubing, and I assume its 1/2" copper and I am guessing about 25m long. The commercial non-pressure systems use a float valve to top off the tank. They are cheap so maybe you could adapt one for your installation.

Cheers, Mick

Posted Thursday 30 Jun 2011 @ 1:50:58 am from IP #
Jeffbloggs
Member

Mick
Why not add concentrated PV strips to the inside of the ET, to make use of a reflective coating on the back of the ET, and use the heat pipe cooling to lower the PV temperature and decrease the PV temperature derate? Plus add some daily 1 axis tracking by rolling the tubes in between two frames. That adds 25% more power. In other words a PVET system with hot water and PV power. Possibly use the array as heat dump radiator at night to run hydronic AC heat pump off peak. Add individual micro-inverters per tube and simple current and heat connection clip in system which allows for progressive expansion of the system....is an old idea of mine, but a goodie

Posted Thursday 30 Jun 2011 @ 11:37:35 am from IP #
sun2steam
Member

JB, we are drifting a bit off topic, but I agree evacuated tubes should have PV included.
I think a thin film PV coating (of course silicon and not one of the toxic metal combinations with Cd or Se) should replace the existing sputter coating on the outside surface of the inner tube. As this layer is 'protected' by the vacuum even more strange chemical modifications might be feasible which in normal atmosphere might not be stable. There may be a lot of research required to get similar optimized properties to standard tubes in regard of maximum adsorption of visible light and minimized emissivity in the IR range.

No need to roll the tubes. I would coat the tube in exactly the same way as they are now. There is an issue with electrical wires that have to go through the glass but this has been solved for radio tubes long ago.

The existing coating cannot be used as a dump radiator because the emissivity in the IR range has been minimized to a very low value.

I would love to look into this but it needs the financial backing of a larger company to cover the cost and the testing of many prototypes.

So after all PV tubes may not be more expensive than flat panels and would offer to use much larger areas for thermal use of solar energy as well for heating in winter and cooling in summer.

Posted Friday 1 Jul 2011 @ 1:38:58 pm from IP #
Jeffbloggs
Member

S2S
Thanks for the feedback. I wasn't quite sure about the radiator dump via ET, but it would make sense given the nature of the ET ie to collect IR.

I agree the electrical connections wouldn't be a problem, but the rotating/rolling of the tubes for daily tracking would be much more important with a collector style PV array. Ambient diffraction of light will not allow the relatively small PV strip to function efficiently.

The strip would probably be only 3-5mm wide, not much surface to produce power with, without the reflective back of the ET oriented properly. It would need to point at the sun most of the time. Nearly all concentrating PV designs are tracking for this reason. One good thing with the concentrating trough design is that it shouldn't be affected much by seasonal variation.
http://en.wikipedia.org/wiki/File:SolarPanel_alignment.png

It could also be possible to have a small mechanical thermal solar tracker built into the end of each tube, That attaches to the mounting frame so that it can rotate, even just 45 degrees of motion would be good enough, and then they could back track when the sun goes beyond that angle, if they are mounted close together.

One other advantage of the concentrating PV design is that you can get the PV efficiencies up to 40% without to much of a cost increase, as the PV area remains relatively small.

I'd love to development it...I'd even employ you to help, but I currently have other priorities atm as well. I could spend a little time and money on it, what would you need to start? I suppose the first thing would be to source and trial the PV cell strip, then optimize the IR collection and then streamline the manufacturing process. Ideas are free...I can send you some 3D drawings to give you an idea of what I mean. I'll leave finding the right ET coating up to you..

BTW they are already doing some micro-inverters for PV modules, but they aren't retailing yet. It would be good to have some universal DSP powered power conditioners that could change from AC to DC and back, with voltages from 5 to 240V...that's how they do it on the ISS, every appliance is running at it's required/best voltage etc, makes sense if you have the budget...the DSP actually smooths the output digitally by sampling the output and using filtering algorithms re-modulates the switchmode...all done in software, pretty cool stuff.

Price wise a PVET system should become equal in cost, plus the embodied PV energy should be lower, the glass recylable and the heat reclamation at a higher temperature more useful ie water purification, steam powered air cavitation pumping, even steam powered cooking and cleaning appliances like dishwashers of clothes washers etc. Steam can do a multitude of tasks with nothing more than water and heat...no detergents, chemicals or scrubbing! Maybe we can even add some solar cooling?

PS I think we're on subject, just advancing it a bit more...

Posted Friday 1 Jul 2011 @ 2:30:12 pm from IP #
Maat
Member

Well....the quotes for our new evacuated tube solar water heater are in! We considered that 3 quotes would be enough to make a reasonable decision.
The parameters....remove old system, install 30 tube, 300 lt vitreous enamel tank, pump, connected to tariff 33 off-peak, only rebates to be REC's (replacing an old flat panel system).

1. Vitreous enamel tank $5260:00 Stainless steel tank $5630:00

2. Vitreous enamel tank $5257:00

3. Vitreous enamel tank $3840:00

Quotes 2. & 3. were from different companies however both used the same product...Ecovation/Heavenly solar. Quote 1. was Apricus.

Like most people these days we have to watch our $$'s so we have decided to accept the 3rd quote. Deposit has been paid so now we wait and see how things go. I'll keep you appraised of installation and performance.

Posted Thursday 21 Jul 2011 @ 11:15:39 am from IP #
rockabye
Member

I posted this in another thread but it fits with a couple of recent posts on combining hws with pv.

http://cses.anu.edu.au/hybridsystems

Posted Thursday 21 Jul 2011 @ 8:16:10 pm from IP #
Anonymous
Unregistered

mick_queensland said:
Hi Sun2
I havent added anything, I am looking for a manufacturer. So far, I dont think the current crop of solar hot water systems is as good as they could be. So, if $50,000 was amortised across all their sales, and if they only sold 50 systems, that would add an extra $1000. Hmmmm. Some of the "non-approved" systems are selling for under an approved system less the rebates....

Anyway, still hoping someone out there sells one similar to what I would like.

Cheers, Mick

Hi, Mick, are you still looking for the supplier? send me a email, then I will reply to you about our products.
Thanks!
Helen

Posted Wednesday 27 Jul 2011 @ 8:47:57 am from IP #
mick_queensland
Member

Just an update on the tedious journey to solar hot water. I was getting close to a final choice but after doing some more checks on my roof site I have found that I will get shade from about 2:30 til dark in winter. DRAT! Summer and the seasons around it should be fine though so I am now thinking of how to improve winter production without poisoning the neighbours giant gum tree..... hhmmmm.

If I put enough tubes in to do winter it will make too much the rest of the time due to the shade. Maybe just bite the bullet and live with boosting in winter until the tree gets lopped. (nb this tree is large enough to fall on and crush one of the two houses (mine or neighbours) or power lines should it "die and fall over"

later, Mick

Posted Monday 15 Aug 2011 @ 1:41:15 pm from IP #
Russell Moore
Member

In winter the power from the sun is vastly reduced after 2pm anyway, so maybe shade from 2.30pm will not be a major problem, at least in winter.

All I can suggest is that you place the tubes/panels as far away from the shade as possible.

Don't lop a gum tree, all that does is to encourage it to grow back with thicker growth, and hence more shade. If at all possible could you tie ropes to the top of the tree and bend it towards the sun's position at 2.30pm? Ultimately the only way to remove the shade is to remove the tree. I would have a civilised talk with the neighbour and see if you could come to an agreement to remove the tree and replace it with a more suitable tree/s, at a shared cost?

Posted Tuesday 16 Aug 2011 @ 12:58:59 am from IP #
Skysolarman
Member

Hi Mick , i have exactly what you are wanting , I own solar heating companies in New Zealand and Australia , i import evacuated tube systems from Italy and China and a solar pool heating system from Germany , all my products are AS/NZS2712:2007 certified except for the Alpha Combo which has a look similar to Solarhart but actually has a lower profile on the roof , it is a heat pipe system that connects into pockets within the tank so the heat pipe connections to the tank are dry , the tank has an element added if required , the pressure is mains/high

http://kloben.it/ll.dhtml?PHPSESSID=aa2a203885afb05efdd51290443d5686 use the link that takes you direct to the Italian website or contact me tony@alphaenergy.co.nz and I will email you what i can

Posted Tuesday 16 Aug 2011 @ 11:41:41 pm from IP #
mick_queensland
Member

Hi Russel,

thanks for the encouraging tip about winter sun after 3pm. I was thinking I could even point the array more east. I am thinking about it, maybe even just 10 degrees would make a difference in winter.
Oh yes, the tree was "lopped" by cyclone yassi and it is sprouting now. It is all lower than the problem shade though. I have "sown the seeds of doubt" with the neighbour and I took out my 5 palm trees that the neighbour didnt like so we shall see what happens on the other side of the fence. A tree like this is not going to easy or cheap to remove.

Worst of all, if it grows a bit higher it is going to affect half my PV array (array is split in two) on the upper storey roof.

On the subject of a SHWS, the guy I chose seems to have gone on holidays! I am starting to wonder if I will ever get a system installed.

cheers, Mick

Posted Monday 22 Aug 2011 @ 2:17:09 pm from IP #
mick_queensland
Member

Hi all,

thought I would update with news on my system. YES, I finally made a decision!
The guy that "went on holidays" stopped talking to me so I moved on :?. After some discussions with Amun-ra I have decided to go with a "standard" Apricus system. Thanks Amun-ra (he dropped it around really quickly)

I will not be tilting it up (as in a a steeper angle than the 22.5° pitch) due to the excess loading during cyclonic winds would thus need to strengthen the roof trusses and therefore I need an engineer and a builder. Geeez! How many of you guys thought about that, hey?

I did not opt for the Stainless tank since the Glass Lined tank gets better RECs/STCs and there doesnt seem to be a great deal of advantage for either tank. The price saving on the GL tank is lost when you replace the sacrificial anode.

Plumber and sparkie show up tomorrow if the rain holds off, fingers crossed!!! (Amun-ra is coming round to watch his baby get plugged in lol)

cheers, Mick

Posted Thursday 19 Jan 2012 @ 6:42:16 am from IP #
mick_queensland
Member

mick_queensland said:
Hi all,

thought I would update with news on my system. YES, I finally made a decision!
The guy that "went on holidays" stopped talking to me so I moved on After some discussions with Amun-ra I have decided to go with a "standard" Apricus system. Thanks Amun-ra (he dropped it around really quickly)

I will not be tilting it up (as in a a steeper angle than the 22.5° roof pitch) due to the excess loading during cyclonic winds would thus need to strengthen the roof trusses and therefore I need an engineer and a builder. Geeez! How many of you guys thought about that, hey?

I did not opt for the Stainless tank since the Glass Lined tank gets better RECs/STCs and there doesnt seem to be a great deal of advantage for either tank. The price saving on the GL tank is lost when you replace the sacrificial anode.

Plumber and sparkie show up tomorrow if the rain holds off, fingers crossed!!! (Amun-ra is coming round to watch his baby get plugged in lol)

cheers, Mick

Posted Thursday 19 Jan 2012 @ 6:44:49 am from IP #
hamish05
Member

Hope you are as happy with your Apricus SHW as I am with mine Mick.

I have only boosted ten times since 01Nov. 10 x 7.2kWh x 10.5cents/kWh = u do the math.

Its a good system.

Posted Thursday 19 Jan 2012 @ 9:29:52 am from IP #
mick_queensland
Member

Hi Hamish,

system installed for one full day now and I am very happy with it.

Its almost 6pm, Qld time now and its still making hot water. Temp on roof is 73°, temp in tank is 67°. One day in the sun here in Townsville and the 315 lt tank is pretty much full of hot water with the elec boost off. Today we have used hot water for showers, laundry, kitchen and we havent tried to save on it, I wanted to see how it would perform, so in fact I used it more than the old system. Installation was completed yesterday afternoon about 2pm.

Now all that remains is to see how well it goes in winter.

Many thanks to Amun-ra (Mike the system supplier) who came round to assist with installation as my preferred plumber had not done a tube system before.
Rain threatened play early in the morning with a tropical downpour dampening things. The rain moved on and we got started in earnest. The whole installation took my plumber and his apprentice and Mike about 5 hours. I assisted a bit and had the Installation Instruction printed out for Peter the Plumber to use as reference. I ran a power cable out to the pump station until the sparkies showed up to connect the booster and add an outdoor power point for the system to use. That took another 1 1/2 hrs. So if you are organised you can have it all done in 1 day and have hot water for showers that night.

Now the paper work, painful but worth it.

Cheers, Mick

Posted Saturday 21 Jan 2012 @ 8:09:40 am from IP #
Greg C
Member

The big problem with lie down tanks is boosting only a small amount of water is problematical. It is better to have an upright tank so you can top off the top 200mm when needed. That is how ours is set up. While with the right (unusual) house design it would be possible to couple the collectors to the tank via, thermosyphon, in most instances a pump will be required. Our system is 22 years old and the original Grundfoss pump is still going strong. Admittedly I have had to replace the thermisters twice but that was due to my poor installation - they have to be kept dry under all circumstances. The other advantage of a split system is you can stand the collectors up to the correct angle boosting efficiency.

Our system provides 82% of the energy to heat the water and that is with old (35 years) flat plate collectors. It is in Sydney

Posted Sunday 12 Feb 2012 @ 5:34:46 am from IP #

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