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Forum Index : Solar : Solar hot water build
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Gizmo Admin Group  Joined: 05/06/2004 Location: AustraliaPosts: 5078 |
A couple of days ago I visited a few of the local solar hot water suppliers to get some prices. The government is offering rebates on solar hot water installations, and I figure, since I've not been eligible for any other government rebate or grant, ever, I should at least take advantage of this one. Not going to happen. The rebate is about $1600 for me, but the solar hot water systems are about $5000 plus. Thats $3600 after the rebate, too expensive! So, inspired by Phills solar hot water build http://www.thebackshed.com/forum/forum_posts.asp?TID=3564&PN =2, I've decided to build my own. My target is the same as Phills, a complete working system for under $400. A visit to the local tip shop and I scored a couple of panels for $30 each. 
I can see some green copper corrosion around the copper tubes inside, meaning there has been water in there. But I also noticed the last owner had smeared silicon around the bottom edge of the glass panel, as though to stop water getting in. So was the water leak from the copper pipes or rain getting into the panel. Removed the aluminum frame and glass. Tip, if your working outside, even if its overcast, dont put your hand on the black panel after you take off the glass, its bloody hot! 
And then drilled out a few pop rivets and lifted the copper array out of the case. 
Used a wire brush to clean off the loose paint and green corrosion, the copper seams to be OK, so set it up for a pressure test. First I filled the array with water, making sure there were no air pockets, and checked for leaks at normal water pressure. All good, so I used compressed air and brought the system pressure up to over 100PSI. Again, no leaks 
I'll test the other panel tomorrow. Glenn The best time to plant a tree was twenty years ago, the second best time is right now. JAQ |
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MacGyver Guru  Joined: 12/05/2009 Location: United StatesPosts: 1329 |
Glen Is the government kickback a true incentive or just a "deal" between the governing body and the solar manufacturers? The reason I ask is, maybe you could recoup the same amount in a home-built unit. You could surely build a dandy collector and storage array for $1600.00 doing everything yourself and use recycled materials! If it turns out not to be the case, it would make a good thing to approach them with. After all, the idea here is to pay it forward so to speak, right? When I was MUCH younger, there was a saying that still rings true today: Use it up. Wear it out. Make it do. Or do without. If the government were true to itself, it would honor your grass-roots effort and give you monitary reward. Then again, that sort of thinking perhaps actually makes sense, so if the idea doesn't fly, it will come as no big surprise, eh? . . . . . Mac Nothing difficult is ever easy! Perhaps better stated in the words of Morgan Freeman, "Where there is no struggle, there is no progress!" Copeville, Texas |
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| AllanS Regular Member  Joined: 05/06/2006 Location: Posts: 67 |
Hi Glen, Since this will save a few megawatt-hours of coal, you should be eligible for STC rebates. Is it practical to get homemade systems accredited? |
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fillm Guru Joined: 10/02/2007 Location: AustraliaPosts: 730 |
Since I have put my system into service , my hot water meter has hardly moved . I have had to turn on the elements only a few times for a total of 53kW/hrs of off-peak power for a period of a little over 4 months, compared to averaging 60kW/hrs a week which would have added up to nearly 1Mega/W of power or $160 , so in the 4 months it has nearly 1/2 paid of the initial $ cost . I doubt the govt would give out rebates to owner/home built Solar hot water systems built with S/H materials without a mile of red tape and getting plumbers etc in to sign of on it which would then gobble up any of the rebate $ and more than likely leave you more out of pocket. If it ends up costing under $400 why not just be satisified with that achievment PhillM ...Oz Wind Engineering..Wind Turbine Kits 500W - 5000W ~ F&P Dual Kits ~ GOE222Blades- Voltage Control Parts ------- Tower kits |
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| VK4AYQ Guru Joined: 02/12/2009 Location: AustraliaPosts: 2539 |
Hi All It was funny to note the price increase in solar HWS when the subsidy was put in place, they went up a bit more than the subsidy. Same thing with the water rebate scheme the price of tanks went up, now no incentive and the price of tanks has fallen again, the whole thing is a scam from both sides the Government and the manufactures, so get your own going and ignore the system you will feel better. My sisterinlaw got one , cost her $3500 got a subsidy of $1000 and her pension rebate $1000 total $5500 and a guy on the gold coast is selling the same unit to the public at $1200 and a plumber charges $500 to install it.profiteering, that's what it is. All the best Bob Foolin Around |
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| Gizmo Admin Group Joined: 05/06/2004 Location: AustraliaPosts: 5078 |
Progress on the panels. When I removed the core, most of the reflective aluminium under it came apart, so I added some strips of kitchen variety al-foil on top of the fibreglass insulation. 
The core back in place and ready for the glass. 
Cleaned up the glass, both sides. Cant see it? Did a good job then didn't I
Finished panel. 
Glenn The best time to plant a tree was twenty years ago, the second best time is right now. JAQ |
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| VK4AYQ Guru Joined: 02/12/2009 Location: AustraliaPosts: 2539 |
Hi Glenn This is recycling at its best from potential scrap or land fill to a fully functional unit again. All the best Bob Foolin Around |
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| Georgen Guru Joined: 13/09/2011 Location: AustraliaPosts: 462 |
Looks great. What are you going to do to make sure it is water-tight? Is silicon enough? I thought about something like that as pre-heater for my gas hot water system. What stops me is that solar panel can effectively boil the water and I am scared to have hot water at different temperatures depending on time of day/night or season summer/winter. Is there a thermostat/mixer that I can put in to always have the same (45 deg C) water temperature irrespectively of what water temperature is inside the tank? Suppose there is George |
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AMUN-RA Senior Member  Joined: 10/03/2007 Location: AustraliaPosts: 144 |
Georgen just go to a plumbing supply and buy an orange cap mixing valve they are required by law anyway on all new hws in australia Every day the sun shines & gravity sucks= free energy. |
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| Gizmo Admin Group Joined: 05/06/2004 Location: AustraliaPosts: 5078 |
Today I picked up the tank. $220. 
Its a DUX 315 litre tank, with 2 inlets, 2 outlets and 2 heater circuits. The elements and thermostats test fine. I removed all fittings, including the sacrificial annode, and hosed the insides with the garden hose. I'll replace the annode as a maintenance measure. Pretty happy with this, should get a few years out of it and its a good size. Glenn The best time to plant a tree was twenty years ago, the second best time is right now. JAQ |
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| Barry T Coles Senior Member Joined: 30/07/2009 Location: AustraliaPosts: 109 |
Hi Glenn Good pick up for that price. Annode replacement is a must & if you want to keep the system for the rest of your life; it's worth replacing the annode every 2-3 years, I replace mine at around that time mark & my Solar Hart is now 32 years old & narry a problem, the annode not only protects the tank but the pannels & copper pipeing as well. Cheers Barry I need to learn from the mistakes of others. I dont have the time to make them all myself. |
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| Gizmo Admin Group Joined: 05/06/2004 Location: AustraliaPosts: 5078 |
Yesterday I started on the pump controller. I'm modifying a PicAxe based pump controller I build a few years ago http://www.thebackshed.com/Windmill/PumpControler.asp. To measure temperature I'm using a couple of little NTC thermistors from Jaycar, part number RN3440. These are very cheap, and measure about 10k at 25 degrees C. One will be mounted at the hot water tank and the other at the panels. The software in the PicAxe will compare the two readings and switch on a relay when the panel temperature is a few degrees hotter than the tank temperature. It also monitors the battery ( 12V supply ) voltage and shuts down for 30 minutes if its below about 11 volts. I'll write it up as a different posts when its all working and tested. 
Glenn The best time to plant a tree was twenty years ago, the second best time is right now. JAQ |
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| fillm Guru Joined: 10/02/2007 Location: AustraliaPosts: 730 |
Hi Glenn, The hystersis value will be dependant on where you put your tank temp sensor. With a low differential temp of 2~3 deg you will need to be measuring temp at the top of the tank, or you will be cooling the stored hot water at the top . It will also cycle the circulating pump at a higher frequency. I have my tank sensor on the outlet of the circulating pump which is the lowest tank temp and the diferential temp set to 20deg , this then ensures hot water that is feed into the top of the tank is not to much lower in temperature and does not dilute the stored hot water with luke warm water, and keeping the hot at the top ready for use. The other problem I found with the temp sensors is the lag time in temp drop and mainly at the top sensor, keeping the pump on and allowing cool water from the collecter again diluting the hot stored water due to the sensor not being in direct contact with the water , after a bit of modification and some heat transfer liquid all around the sensor the problem was fixed . The modification I did to my existing electric hot water system to solar has reduced the power usage for heating water to almost nothing . Prior to the mod in average I was using 60kW/H a week in off peak power ( 3120kW/H per year ), since doing the mod in Sept last year to now I have ony had to turn the elements on a few times which has used 153kW/H to date ( approx 4.5kW/H a week). This is with using Hot Water for laundry/dishwasher/teenage son who likes 20min hot showers and all the others thrown in . PhillM ...Oz Wind Engineering..Wind Turbine Kits 500W - 5000W ~ F&P Dual Kits ~ GOE222Blades- Voltage Control Parts ------- Tower kits |
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| Gizmo Admin Group Joined: 05/06/2004 Location: AustraliaPosts: 5078 |
Thanks Phill To reduce the lag I was going to use a old trick I picked up when fitting electric radiator fans to speedway cars. I'll solder a 30mm long length of 8mm copper pipe to panels 19mm outlet pipe. One end is closed off, I squeese in some heat transfer compound, then slide in the sensor and cable tie in place. I'm wondering about the air bleed valve, if its really needed. If I pump water into the panels bottom inlet pipe, then its going to completely fill with water, no matter how much air is in the system. The only air that could get stuck is after the top outlet, where the pipe turns down. Thats not going to be a problem, and besides a air pocket will stop syphoning at night. If I have a check valve on the pump, then when the pump is off, the water level in the panel will stay at the top, and not creep back down, exposing the panel core to air. I know a air bleed is only about $40 but the money is tight and if I dont really need it then I wont buy it. If it was a system that relied on convection instead of a pump, then I could see the need for the air bleed. Glenn The best time to plant a tree was twenty years ago, the second best time is right now. JAQ |
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mac46 Guru Joined: 07/02/2008 Location: United StatesPosts: 412 |
Hi Glenn, I would say that you will need the air bleed valve because over time the water will "gas" out, or inother terms it will expell o2 into the gas state, as well as other gasses if it is contaminated. Off the subject, Has anyone noticed that the earth is about 2 degrees off of its normal rotational progression, or is this because of the last bottle of prescription pills I picked up? And why have'nt the governments of the world said anything about this? Mac46 I'm just a farmer |
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| Gizmo Admin Group Joined: 05/06/2004 Location: AustraliaPosts: 5078 |
Yes very off topic Mac. Earthquakes can affect the axis, but only a few seconds, not degree's. It's not really a government thing, to report changes in the axis ( or solar flares, magnet pole variations, etc ), its more of a scientific community thing. I would look for answers on a renowned science institution web site. Also check out NASA.gov, if anyone needs to allow for axis shifts its them. Back on topic please. The best time to plant a tree was twenty years ago, the second best time is right now. JAQ |
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| AMUN-RA Senior Member Joined: 10/03/2007 Location: AustraliaPosts: 144 |
glenn dont waste your money on a avv for your solar you dont need them on a pumped system sush as yours Every day the sun shines & gravity sucks= free energy. |
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| Gizmo Admin Group Joined: 05/06/2004 Location: AustraliaPosts: 5078 |
I've moved into the new house and needed some hot water, its cold here! So I connected up the hot water tank and wired up a power lead so I could heat it with my generator. The tank has two 3500w elements, one at the bottom for heating the whole tank using off peak power, and one at the top for heating 50 odd litres as a top up. First day, used the top element, took the generator about 30 minutes before the tanks thermostate switched off. That gave enough hot water to wash some dishes and have one shower, and that went cold before I finished 
Next day I connected the generator to the bottom element. 2 hours later it was still running, so shut it down and had a tank full of luke warm water, better than cold water I guess. I worked out I needed to run the generator for 1.5 hours each day to keep this water luke warm  Thats a lot of fuel to give me warm water!
I needed to get the solar panels working. Built a basic but secure frame from timber, fencing wire and some star pickets, and mounted the solar panels. It's set up as a syphon system with no air pockets, and I'm using a gate valve to turn it off at night. Its works a treat  End of first day I had half a tank of hot water, next day it was full. A full tank will last me a few days if its overcast.
No leaks in the tank or panels. Next step is to mount the panels on the roof of the house, but that will be a few months away, got some other jobs to finish before then. May have a problem with the local council. I was talking to a council inspector who was checking off my septic system, and he said they wont approve an old electric hot water system, not green enough. I explained to him I was adding solar heating panels, and he said that it still needs electricity from time to time to top up the heat. I tried to explain my electricity is off grid and comes from solar panels, so it was green. He was unsure if the rules would bend enough to think out side of the square, but I could try. We'll see. The big surprise in this is just how much energy is needed to heat water. Glenn The best time to plant a tree was twenty years ago, the second best time is right now. JAQ |
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yahoo2 Guru Joined: 05/04/2011 Location: AustraliaPosts: 1166 |
You will have to read the fine print, for a NEW install I think you need to be eligible for a minimum number of REC's for the size of the house to pass muster or they will make you fit a heat pump or bottled gas system .
For replacement there is an exemption if the gas supply is not going past the property until the end of 2012. Dept housing electric hot water service replacment Plumbers reference guide PDF energy wise qld PDF I'm confused, no wait... maybe I'm not... |
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| Gizmo Admin Group Joined: 05/06/2004 Location: AustraliaPosts: 5078 |
Thanks for the links Yahoo. Even though its a old house relocated, I've had to abide by rules for a new house, which is a real pain. For example, its a 2 bedroom house, so they designed the septic system for 5 people, even though its only me at this time. The septic tank it 4,000l and the evaporation trench is bigger than the house pad! Cost me a fortune. I've also had to change the stairs because they are not complient with new rules, and fit heaps of insulation, but thats not so bad. One thing I learned, quotes are not worth the paper they are written on and 2 weeks equals 2 months in the building industry. The Owner Builder course I had to do tries to prepare you for this, but it falls very short. They say allow 20% variance, but its closer to 60%. The plumbing inspector did say I should have a case, it depends on the person interpreting the rules at the time. Glenn The best time to plant a tree was twenty years ago, the second best time is right now. JAQ |
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