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Forum Index : Solar : Advice on new solar set up for home and workshop

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Davo99
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Joined: 03/06/2019
Location: Australia
Posts: 298
Posted: 12:26pm 27 Nov 2019
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We recently remodelled our 70 Sqm kitchen and put down new Tiles. I thought of electric underfloor heating and looked into it... Very Briefly.  Even on fleabay it was $130-170 Per sq Meter!!  For some thin wire in some sheathing???

Of course the amount of power it pulls is... inspirational... as well.

I'm sure having heated floors is a very nice thing but a Luxury.... well I can afford, but I'm not inclined to on the basis I think it's a pretty poor investment. Maybe when I win lotto and money doesn't matter any more.

Perhaps Rodger you are looking at the wrong thing with panels.
Perhaps I should be giving you some tips on running a Diesel generator on free waste oil as I think that's going to better serve your needs. Even 3KW extra for the few hours you are likley to generate in winter probably won't do anything more than balance the losses in the slab if you are lucky.

I have over 20 Kw of panels and I still fall VERY short of the power I need in winter to run the Ducted AC. That is about 5 Kw across the 3 phases and combined with the power draw that shoots up in winter from the HWS, -I- couldn't really get a viable amount of panels up to cover it. AC has a multiplication factor in winter that you wouldn't get with direct heating so getting any worthwhile benefit in winter IS going to need those 60 Panels.... as a starting point anyway.

I think that would take 30-40 Kw of panels easily and that's a ridiculous Amount. The thieving power cos won't even buy back the power at the pathetic rates they give you over 10 kw when you could Boil a swimming pool with the power you'd have in summer.

Wood is nice but a pain in the arse amount of hard work. I have been Felling trees, cutting, splitting and stacking wood for my father for years. Even with tractors and forklifts and the biggest splitter they make for domestic use, it's still a LOT of work.  It sure beats trying to offset your winter heating electrically though.

Just on that, My Father rang tonight.  Tight arse Neighbour was complaining about his electric bill.  Dad told him his was $190.  Neighbour went into orbit saying how can he run a business from home and only get $190 bill?  Dad pointed to the shed roof where I put up a solar setup for him.


Dad Said to me tonight my last bill was well over $400, how come this one is less than half? I said because your solar Does nothing in winter, as I told you, it's the wrong direction, the wrong tilt and sees NO sun in winter.  Now however, the thing is running about flat out with the panels you have so that's the difference.
He said so it makes my bills less than half? I said about 8 months of the year it will.
He said well that was money real well spent wasn't it?
I said yeah, payback time of 6 Months and you are 2 years into it so making money.

He said they guy next door was asking when I was coming back up there again as he wanted to ask me a few things about setting up his solar.
I said I haven't got long enough to live to tech him what he needs to know.
I spoke to him about it couple of months ago when I was up there and he admitted he has no clue about electricity. I said you sure picked the wrong game to play then mate!

I don't know what his trade is but I think he should stick to that at least until he learns a lot more. The obvious answer would be to get someone in but like his father, The original Scrooge, his wallet is airtight. I wouldn't mind helping him if he helped Dad a bit but all he does is come and bludge off him and never gives him a thing in return.
 
rogerdw
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Joined: 22/10/2019
Location: Australia
Posts: 76
Posted: 01:52pm 28 Nov 2019
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  Warpspeed said  In winter you are only going to have solar for about six hours out of twenty four hours, and on really cloudy days almost nothing.

Underfloor heating needs to be continuous to work, its so very slow to heat up.
A better bet might be a solar powered heat pump. You can get more heat out than the energy put in, and it starts working as soon as you switch it on.


That's a bit of a let down.

I had done some research a couple years ago  ...  and I understood that it needed to run for maybe 12 - 18 hours a day to warm up the slab and keep the place warm.

Admittedly it is supposed to cycle on and off once it gets to temperature  ...  but it would flippin well want to  ...  two circuits at 3000 watts each  ...  6000 watts total before you even boil your eggs!!!

I spoke to a sales guy yesterday and he says it will reach temperature in half an hour to an hour  ...  but he said as soon as you turn it off there's no retained heat.

I asked if the slab would slowly warm up and help retain the heat at least a bit  ...
and he said no it wouldn't. Was a bit cagey about running costs  ...  but their site claims 2 cents/hr/square meter. We've got about 80 square meters at least.

Looks like that idea bites the dust.
 
rogerdw
Regular Member

Joined: 22/10/2019
Location: Australia
Posts: 76
Posted: 02:14pm 28 Nov 2019
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  Davo99 said  We recently remodelled our 70 Sqm kitchen and put down new Tiles. I thought of electric underfloor heating and looked into it... Very Briefly.  Even on fleabay it was $130-170 Per sq Meter!!  For some thin wire in some sheathing???

Of course the amount of power it pulls is... inspirational... as well.


Yeah, I'll say. There was actually another complete 3000Watt 238mtr roll in the cupboard as well that they didn't install. Imagine that  ...  9000W on full throttle.  

  Davo99 said  
I'm sure having heated floors is a very nice thing but a Luxury.... well I can afford, but I'm not inclined to on the basis I think it's a pretty poor investment. Maybe when I win lotto and money doesn't matter any more.

Perhaps Rodger you are looking at the wrong thing with panels.
Perhaps I should be giving you some tips on running a Diesel generator on free waste oil as I think that's going to better serve your needs. Even 3KW extra for the few hours you are likley to generate in winter probably won't do anything more than balance the losses in the slab if you are lucky.


Yes, I might have to look into that once the solar side is sorted out. I certainly will hit you up for questions if I go down that path.


  Davo99 said  
I have over 20 Kw of panels and I still fall VERY short of the power I need in winter to run the Ducted AC. That is about 5 Kw across the 3 phases and combined with the power draw that shoots up in winter from the HWS, -I- couldn't really get a viable amount of panels up to cover it. AC has a multiplication factor in winter that you wouldn't get with direct heating so getting any worthwhile benefit in winter IS going to need those 60 Panels.... as a starting point anyway.

I think that would take 30-40 Kw of panels easily and that's a ridiculous Amount. The thieving power cos won't even buy back the power at the pathetic rates they give you over 10 kw when you could Boil a swimming pool with the power you'd have in summer.


We do have a ducted aircon as well  ...  but I've left that out of the equation altogether. We rarely run it  ...  mainly because of the expense  ...  but when it cuts in and out the lights dim dramatically. Does 15kW sound possible?  ...  all on a tiny underground cable 450 metres from the transformer.

I can see a small split system being useful for just one room that gets a fair bit of use and could do with more heat in winter and a bit of cooling in summer.

Summertime cooling should be no issue  ...  it's really only winter warming that might be hard to supply if no sun around.


  Davo99 said  
Wood is nice but a pain in the arse amount of hard work. I have been Felling trees, cutting, splitting and stacking wood for my father for years. Even with tractors and forklifts and the biggest splitter they make for domestic use, it's still a LOT of work.  It sure beats trying to offset your winter heating electrically though.



Yep, agree 100%. Hard work  ...  though is the best sort of heat in my view.

Looks like wood it is for the time being.  

I did look at building a biogas generator a couple years ago  ...  out of 2 or 3 IBC's  ...  and modify a couple gas heaters to run on it.

Could possibly run a generator on it too perhaps. No idea really  ...  need to sort out as much solar as possible first.


Cheers,  Roger
 
BenandAmber
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Joined: 16/02/2019
Location: United States
Posts: 791
Posted: 06:17pm 28 Nov 2019
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Me and my wife both have a lot of broken bones


Wood Heat is the only thing that gets us through the winter

With our electric furnace forced air we can have it on 80 and freeze to death

With electric heat are bones ache like toothaches in the winter

Friend of mine two Winters ago brought up
a big nice 800 lb wood heat stove and helped me install it

It has been such a blessing no more achy bones in the winter you just cannot beat wood Heat

That same buddy comes and gets me about once a month

We go goof off have a good time and cut and split a couple loads of wood

Amber is kind of fidgety and I rarely get a chance to start a fire or add wood to it

Our electric bill ran over $500 a month in the winter before this wood stove

In my personal opinion every solar setup should have a good wood stove for heat

Cut and split your wood with a buddy then it's just a guy's Day Out takes all the work out of it
 
Warpspeed
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Joined: 09/08/2007
Location: Australia
Posts: 2915
Posted: 08:40pm 28 Nov 2019
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About forty years ago I worked as a technical officer for the Victorian Solar Energy Council.
That was a State Government run organisation set up to fund and encourage solar energy projects state wide.
We had wind projects, solar thermal projects, and solar electric projects. I was involved only very slightly with some of the project planning, but more specifically all of the subsequent monitoring, data logging, and any project maintenance and repair once it was all up and running.

One project (which started before my time) was the hydronic heating of the Patch Primary School up in the Dandenongs in Victoria. This was a solar thermal hydronic system which used a massive array of solar panels mounted along the full length of the building. These panels were north facing and mounted at a sixty degree elevation for best winter performance.

The school was a long skinny building running east/west with a passage down the middle and classrooms set either side of the passage. Solar panels ran the full length, there must have been sixty yards of them, the panels themselves would have been about six feet high.

Water heated by these panels was pumped into a large insulated 10,000 gallon water tank. Hot water was then pumped to fan coil heat exchanges in each classroom.
About one third the way from the top of the tank were three 15Kw electric heating elements.

The control strategy was to gain as much temperature rise as possible in the tank by cycling the pump to the solar panels during the day, in the usual way. If at the end of the day the tank temperature was judged to be too low, the heating elements would kick in, (on off peak power) and only heat the water in the top third of the tank. It was thought by the original designers that 3,300 gallons of fairly hot water would contain enough heat to heat the school.

The whole thing was a bloody disaster. The School principal would arrive early and start up the system so the school was warm before the kids started to arrive. By mid morning the heating had diminished to almost nothing, there simply was not enough stored heat, and the electric power bills were eye popping.

The main problem was that the top third of the tank heated up o/k at night and remained stratified, while the lower two thirds stayed almost stone cold on grey cloudy days. As soon as water was pumped around through the fan coil units from the top of the tank, the hot returning water was diluted by the cold water in the lower tank through mixing.

All I could do was install a third circulating pump to circulate the water continuously around the tank at night.
Whenever the heating elements came on, the pump would run, and that heated the whole tank not just the top third. That improved things, it now heated the school to around lunch time, and the electricity bills were about triple eye popping.

The school was still getting pretty cold in the afternoons, so it was decided to run the electric elements during the day from full tariff. That was an expensive project funded by the State Government. The education department were paying the power bills and were having absolute hysterics. That was certainly not our most glorious project.

In summer it boiled of course.  If you have ever heard steam bubbles imploding in a 10,000 gallon steel tank, its a pretty loud scary sound.

One memorable lesson I learned from all this, was that if its a very cold cloudy day, maybe one of several in a row, expecting solar to keep you warm just ain't gonna happen.
Cheers, Tony.
 
Davo99
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Joined: 03/06/2019
Location: Australia
Posts: 298
Posted: 11:20pm 28 Nov 2019
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  rogerdw said  

We do have a ducted aircon as well  ...  but I've left that out of the equation altogether. We rarely run it  ...  mainly because of the expense  ...  but when it cuts in and out the lights dim dramatically. Does 15kW sound possible?  ...  all on a tiny underground cable 450 metres from the transformer.


On that significant detail.....
You will be able to run AC to your hearts content in summer.  You won't have any supply problems being the power will be coming in from the load ( your) side not the supply side and that 450M run will be taken out the equation. Of course the cost will be non existent as well. If you were worried about the cost of the AC, the underfloor  heating would really make your eyes water.

It would be unlikely that the AC PULLS 15 KW. It probably is rated for 15 Kw output but AC is one of those things where you get more out than you put in, power wise at least. If it's a 15 ton machine, same as Mine, it's probably around 2-3 Kw per phase or 5 Kw if single phase.  If it's a 3 Phase, one phase will work 1/3rd of the compressor draw Plus the fans and roof blower so will be higher draw. The other 2 phases will be lower as they will just supply the motor.

I shifted the phase rotation on my machine because the Highest phase was on the electronic meter I couldn't back feed. Now it's on one I can. I have a small 1.5Kw inverter on a relay on the 3rd leg. When the compressor boots up a DPDT relay is activated so the power from the inverter is switched from supplying one of the other phases to feeding that one. Doesn't do a lot at night of course but During the day the ac costs  me nothing to run which is a VERY satisfying luxury to have. As such I run it flat out during the day to Cool soak the house much as I can and Minimise Night useage.  Days can easily be 40+ here and the night temps fall to 20 so that part works pretty nice.

I also on the real hot days water mist the condenser.  I just have 2 Micro Mist water  sprayers in front of the Condenser unit. They are pretty offset but the airflow from the fans pulls the mist through the condenser fins very evenly and the temp DROP on the air coming out the unit I have measured at 28oC on occasions.  That's making life much easier for the unit and much more efficient as well. They have an efficiency curve and over about 35o things start falling off fast. When it's 43 here, the thing is probably putting out less than 1/4 the output.  If I'm lowering the output temp 20+o, then the machine is right in it's curve and giving me max Cooling.

I think the misters are 3L Hour so not much at all and very worth while the bit of water. I also Sprayed water through the thing one Freezing night when there was no heat coming out at all. If the water is about 8oC, it's a lot warmer than the sub freezing air temp.  You have to run a lot of water to stop the thing icing up and give it enough energy to work off but work it did.

There is one potential problem I see with your setup.
With that 450M run to the pole of what you say is thin wire ( Have to be over 16mm surely) You might have voltage rise problems with your solar.  Just as you get voltage Drop with the lights dimming, Pushing the power back the other way may cause voltage rise. It's basically like water, Trying to push water a long way gives you higher pressure at the pump ( voltage)  but low pressure at the outlet.

It won't matter if you are intending to use all the power or most of it your solar generates but if you are wanting to send some back to the grid to get a FIT,  A fit is exactly what your inverter(s) may have when the voltage is too high your end. You might be wise to look into this and perhaps pay extra for an inverter you can set the export limit on. That way instead of your inverter trying to push say 5 Kw down the line and tripping out constantly due to high voltage, you may be able to back it off to say 4 KW which it will be happy with and you'll get a FIT on 4 KW all day instead of never getting 5 KW and Only getting 4 KW or below on the ramp and fall off periods.

You can manage the voltage rise like I did with my hot water on the Voltage relay and you could put things on timers/ relays etc but if your mains voltage is already high or conversely, if you are getting a lot of voltage sag, then your power management will be even more important.


  Quote  I can see a small split system being useful for just one room that gets a fair bit of use and could do with more heat in winter and a bit of cooling in summer.


I'd be trying to work out what might happen with this Voltage rise and if it will be a problem first.  Might just be that you are better to run the main AC to keep the whole house Cool in summer certainly because if you don't burn some of that power, your inverter may trip out and do nothing. Your supply lines should take the run into consideration and I'd be thinking you should have something like 32 mm cable But I'd be trying to take that into account before you install your solar so you get the equipment you may need. When you say the lights dim, that's not a great sign.

  Quote  Summertime cooling should be no issue  ...  it's really only winter warming that might be hard to supply if no sun around.


I fully agree with Tony's Conclusion.  Using solar for heating in winter is folly.

Few months ago I was looking at 4 Kw Inverters pushing 3.5Kw most of the day and thinking if the thing is at about 80-90% all day, how come the generation is through the floor? I thought the over drive of panels I have on the inverters would cancel the lower radiation to a decent amount which it did as could be seen in the instant output, but totals were terrible.
Then the 2V light in my head flickered Dimly and I realised it was due to the short sunlight hours. There is no effective way around that. Putting up enough panels to compensate is just not viable.


  Quote  
Yep, agree 100%. Hard work  ...  though is the best sort of heat in my view.


I think the thing with wood is there is so much heat. I know my Fathers wood Burner is rated at 35KW output. That's a LOT of heat! Imagine trying to get that with electric  (145 A) and gas heating for that would be pretty substantial as well.

Now If I can convert that 100Kw spa heater to Oil...... :0)
Actually, the biggest challenge I see in that is making a burner LIMITED to about 10Kw output.

  Quote  I did look at building a biogas generator a couple years ago  ...  out of 2 or 3 IBC's  ...  and modify a couple gas heaters to run on it.


Umm, Biogas would also be useless in winter unless you put it inside and heated the tanks. I played with that myself and From memory the lowest temp the tanks need to be is about 28 I think. Under 20 and they die. Great in India where the temp never falls below 30 but when you are talking  5o or less...
 
Warpspeed
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Joined: 09/08/2007
Location: Australia
Posts: 2915
Posted: 12:42am 29 Nov 2019
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If a lot of continuous winter heating is required, probably the most efficient way to do that would be with a water cooled diesel powering a heat pump.

The heat pump evaporator might commonly use ambient air, but it could also be buried, use ground or tank water, or even be solar boosted.
If its really frosty very early in the morning, ambient air might not be the best heat source.

The heat pump would provide rapid fast acting space heating, and the engine cooling system provide domestic hot water (via a heat exchanger).
Cheers, Tony.
 
Davo99
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Joined: 03/06/2019
Location: Australia
Posts: 298
Posted: 08:42am 29 Nov 2019
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  Warpspeed said  If a lot of continuous winter heating is required, probably the most efficient way to do that would be with a water cooled diesel powering a heat pump.

The heat pump evaporator might commonly use ambient air, but it could also be buried, use ground or tank water, or even be solar boosted.
If its really frosty very early in the morning, ambient air might not be the best heat source.

The heat pump would provide rapid fast acting space heating, and the engine cooling system provide domestic hot water (via a heat exchanger).



I would use the heat from the engine through the evaporator rather than bury it.
The heat in the exhaust alone would provide a lot of energy for the heat pump to work off and certainly be a lot higher than ground temp. As an internal combustion engine's turns 1/3rd of it's fuel to waste heat, it would make a huge benefit to efficiency to recuperate this energy. An aircooled engine could easily have it's cooling heat directed through a condenser.

The other reason I would keep air as the heat transfer medium is because in summer you could merely redirect the gas flow through the condenser and use ambient air for cooling from the same unit.

A large car AC puts out the same sort of capacity as a medium size split AC. Easy to get everything one needs from a wrecked Vehicle. Add and RX valve and you have heating and cooling. LPG works perfect as the refrigerant and for those concerned with legalities, There is none with it unlike R-134a etc. Instead of using charge weight to gas the system, just use pressure which will take into account the length of your extended pipe runs.


I have been toying with the idea of using a 5000L water tank I have as a thermal storage bank.  Circulate the water through a radiator during the day for cooling the house. Run the water through an external radiator at night to cool the water back down. Here it's common for a 20o temp drop and more over night.  Bit of a water spray wouldn't hurt the cooling effect either.

10o Difference in 5KL of water is almost 60 Kwh of energy.  That's worthwhile.
If I could get the tank temp down to 15o, I'd really be laughing.  That said, even having 30o air blowing in here many days would be a help.
Edited 2019-11-29 19:03 by Davo99
 
Warpspeed
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Posted: 08:48pm 29 Nov 2019
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Some great ideas there Dave.

Using exhaust heat can have some practical difficulties. An exhaust heat exchanger will fill up with soot pretty quickly if the temperature of the surface inside the heat exchanger is low.

Even the fire tubes in a steam boiler need to be blown down with high pressure steam, or rodded out with brushes, to shift all the soot that builds up fairly quickly. So whatever kind of exhaust heat exchanger you are planning needs some fast and easy way to clean it out fairly frequently.
Cheers, Tony.
 
Davo99
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Joined: 03/06/2019
Location: Australia
Posts: 298
Posted: 11:18am 30 Nov 2019
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  Warpspeed said  Some great ideas there Dave. So whatever kind of exhaust heat exchanger you are planning needs some fast and easy way to clean it out fairly frequently.


I have done some rough experiments with this.  What I found was a water spray works very well.  It removes the carbon which is soft and fluffy and leaves no more than  a base coat on the ally fins, If that.

I believe a regular dosing of water in the exhaust, Possibly with a little detergent added to soften the water would work well. I also think water injection into the engine would also help the engine and the Build-up from the soot on the condenser.

That said, I also am of the opinion from what I did that if the engine is not overloaded and the engine is running well with a good injector, the fact a diesel will operate with excess air means the over all running will be quite clean with more ash particles that will blow right through rather than soot which seems to be more sticky.
If an engine were somewhat oversized to ensure it always ran lean, this would help a lot.

As I said my tests were rough but I believe were indicative of what would happen in this scenario and that water injection into the engine and the exhaust, Possibly with a strong direct water spray, would keep a condenser clean enough to operate efficiently.
 
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