Renewable Energy Questions/Discussion > Solar (heating or electric)
Passive solar air heater - for home
DJ:
I have just bought a new home with a metal roof. A roof is a huge area for solar heat gathering and I plan to use it.
The place has ducted air but I have spoken to a fridgy and he says it's no problem to set up an extra inlet that will draw this warm ceiling air and pump it into the house in the fan mode of the AC. I'll stick a filter on the end of the pickup to eliminate any dust being blown into the home. I already have some thermostats like linked in the previous post so I can compare the home temp and the roof air temp. My thought is that I probably won't be able to run the thing constantly but have to wait for the air to heat up and then run that into the house. Then again, probably depends on the day and if only a small rise is required, may be ok. Otherwise, anything is a bonus and cheaper than running the compressor on the AC unit.
I'm not sure if there is insulation under the tin itself, there probably will be a form of it in a waterproof/ insulation membrane but given the area of the roof and the amount of sun falling on it, I believe worthwhile amounts of heat can still be harvested. There is insulation on the ceiling and the good part about this system is any escaped heat will be re used as it were.
I'm also looking at adding another similar pickup on the AC and putting a radiator in front of it so it can draw through and heat air from an oil fired water heater and disperse that into the house. Main thing is to work out a practical and aesthetic place to put the burner/ boiler.
Looking on the net at DIY heating ideas always does my head in. I literally want to pound my skull against a brick wall at so many of the idiotic concepts and moronic rubbish people go on with.
Are these people mentally impaired to think that a few tea light candles are really heating a room? Are they too stupid or just so wanting to believe it works to do some simple research as to how much heat a candle generates and not see that their plasma TV generates a load more heat and does it at a fraction of the cost of buying tea candles? Amazes me when you see these people are talking about heating a dorm at a university! So much for higher education and learning.
It beggars my belief that they just can't look at the thing and know it's going to put out no worthwhile heat at all.
But then there is the be all and universal method of DIY heating.... a bit of copper pipe coiled and sat over a typically open fire.
Yep, if you wanted to go low efficiency, Couldn't think of anything much worse... or better if low efficiency is what you are after. Just let 99% of the heat from that fire blow away doing nothing at all but kid yourself you are putting 100Kw worth of heat into that pool and it will be warm as toast come summer.
If you want useless, forget about the Candle in the room, try heating an above ground swimming pool with water running through a bit of 3/4 or 1" copper that's sitting over an open fire. Now THAT is kidding yourself.
The internet is for more than watching porn and recordings of video games. There is an incredible amount of information and calculators that would let you see how useless this is through all sorts of heat rise tables and calculators, thermal capacity charts and many other related information. Once you look a couple of these things up and even get a slight feel for it, you can then look at something and straight away have a fair idea how poor it's going to be.... unless you are one of these people that likes to kid themselves badly and cheat themselves.
You don't need to be smart to look this up, I'm dumb as dirt but fortunately, smarter, educated people made it easy for pelicans like me to look up what is going on so we can see if something it worth while or a complete waste of time.
As I like results and loathe Kidding myself, I like to make things that WORK. Like really work.... using all that stuff most of these DIY heating clowns hate... like fact... and physics and scientific principals.... and lord forbid..... Measurements and reality. Yes, I know, using all that stuff limits your thinking and it's much easier to make something that keeps you warm if you don't actually measure the results using something as sophisticated as a thermometer
to verify your delusio... work but it unfortunately, paying attention to fact and scientific principals and laws at the end of the day will keep you warmer.
Like as in really warmer, not just mentally warmer.
It amazes me the way people will spend so much more on their hair brained schemes to save money that what they would spend on conventional practices like electricity or gas. Look up the actual heat energy in that packet of $4.99 tea candles and work out the cost per BTU or KW. Then compare that to what you pay for a KW of electricity. Yes, you just spent 20x more on the candles didn't you? Amazing! Who could have ever worked that out.... except anyone with access to the net and a desire to separate fact from stupidity.
I also want to incorporate PV for heating. I just bought another 2.5Kw of used panels for $500. I'll have a large ( and going to be made larger) shed roof that points directly north that I can put a LOT of PV on before I even get to the house which for the most part is east west. The way the property is means there is nothing to stop me just putting up a ground mounted system which I will use the panels as a roof for a shed or pergola anyway and seal them together with silicone when I mount them.
I'd like to heat water and then back feed the excess through the old analogue meter and run it backwards so what I make during the day can be used at night.
As mentioned, PV, particularly used is so cheap now if one has the situation for it, it's a very viable and practical thing. You hang your panels and don't have to change anything else in your home or the way you live. Using the grid for a power bank and getting a 1:1 feed / return ration although a little " grey" market is very efficient and serves the green principals and objectives that we are constantly having shoved down our throats so is something able to make use of that crock as well.
rossw:
--- Quote from: DJ on May 22, 2017, 09:52:55 pm ---If you want useless, forget about the Candle in the room, try heating an above ground swimming pool with water running through a bit of 3/4 or 1" copper that's sitting over an open fire. Now THAT is kidding yourself.
--- End quote ---
--- Quote ---I also want to incorporate PV for heating. I just bought another 2.5Kw of used panels for $500. I'll have a large ( and going to be made larger) shed roof that points directly north that I can put a LOT of PV on before I even get to the house which for the most part is east west.
--- End quote ---
From a purely EFFICIENCY point of view, using all that roof space for PV, at a return of around 15% (by the time you take out inter-cell space, inter-panel space etc), assuming you then use resistive heating to heat water, it's still a low yield.
Evacuated tubes (wet or heat-pipe) can give you around 4 times that, and achieve decent temperatures.
--- Quote ---I'd like to heat water and then back feed the excess through the old analogue meter and run it backwards so what I make during the day can be used at night.
--- End quote ---
Of course, it's more difficult to run hot water backwards into the grid :)
Don't count on your old analogue meter staying there for too much longer. As soon as you start using it to YOUR benefit (like, reducing your power bill), they'll be out to change it over. Either because they think it's gone faulty (and reading less power than you're using) or that you're running it backwards (which they don't want!).
--- Quote ---Using the grid for a power bank and getting a 1:1 feed / return ration although a little " grey" market is very efficient
--- End quote ---
There seem to be different interpretations of "net metering". A number of authorities add up the "numbers" and then charge you at their sell rate, or pay you at THEIR buy rate, on the net. That's not "net" in my view. Still, it's better than the alternative of selling ALL your power to them at their buy rate, and buying ALL your power from them at their sell rate!
eidolon:
Heating with PV may not be great area wise, but it is cost wise. PV also works in the summer which the evacuated tube people never talk about. If you don't keep the panel voltage at MPPT, you will waste half the power over the day. I do this with elaborate electronics, but if multiple heaters (as few as 4) can be switched in and out throughout the day more than 85% efficiency can be maintained. See electrodacus.com for an explanation, I don't approve of his product at all. I have a small efficent system of heating water with waste PV, enough for my limited use. More interesting is my system works with only one car battery. It is only used for motor surge current and a couple minutes of running the fridge. I store cold with large fluid mass to keep the frequent cycling. You could easily run the refrigerator all day with PV, switching in and out of grid power during the day. All this takes intelligent control that isn't practical at this time, maybe in 15 years it will be common.
Wife wants a dishwasher this year. Saying I thought I married one apparently wasn't a correct answer. So, I will fill and then heat. When up to temp I'll start the cycles. A cloud comes over and I will stop for a while then restart. Might take twice as long, so what.
There is a big difference between possible and probable..
DJ:
--- Quote from: rossw on May 23, 2017, 03:01:29 am ---
From a purely EFFICIENCY point of view, using all that roof space for PV, at a return of around 15% (by the time you take out inter-cell space, inter-panel space etc), assuming you then use restive heating to heat water, it's still a low yield.
--- End quote ---
I have looked into this and done my homework about as best as I can figure.
For me personally, there are a number of factors that make PV the preferred method....
As far as roof space, I went and looked at some options for a patio roof this afternoon. I'll have 40 SqM facing north with that, another 50 Sqm on the shed and probably about 10 SqM on the house directly facing and 150?? sqm orientated east/west. -I- am NOT going to be short of roof area in any way shape or form!! :0)
From what I can look up, a 10Kw system of 250W panels is only going to take 65 Sqm of roof. Thats not going to be a problem and 10Kw is probably as much as I can use in reality.
The PV won't just be used for water heating. Once the water is up to temp I can switch that power to something else. I'm looking at a controller to say kick in the clothes dryer, run the pool pump ( when I put one it) run the AC or just back wind the meter for later use.
Far as I can see, when your tube heater had the tank boiling probably by 9am here in summer when it can already be 30oC easily, WTF is the thing going to do the rest of the day? Boil off water? Not even sure how they work once up to temp and with excess solar energy going onto them.
To me that's the thing, a solar water heater heats water, that's it. Nothing else. PV can do a lot more for me.
For heating water, with PV I don't have to change a thing. Can use my current heater and for me, a bit of wiring is a lot easier and cheaper than plumbing. I'm thinking of running a 2nd heater as well. This could be run as either a full temp heater to boost capacity or as a dump load pre heater feeding the existing tank. I'm not sure how much hot water I'm going to need as yet. Our old heater died a couple of years back and as I had in mind to move, I put in a tiny one that I got cheap to get us by. We are all looking forward to long hot showers and something we have never had before, a bath.
No idea what the usage will be as the "facilities" for bathing in the home are different as is the current family size.
Solar water heaters here are a LOT more exy than PV, used or new. For me putting up PV and wiring it is also far cheaper than plumbing and running pumps etc. It's also less difficult from an aesthetics POV.
One other thing for me is Oil heating. I have built all sorts of weird, wonderful and powerful oil burners and converted gas heaters. When our electric hot water blew I plumbed up the oil fired gas heater and we used that for a few days. Once up to heat the thing could keep up with the demand indefinitely.
When push comes to shove, my oil fired heaters will outdo any form of solar heating and the gap gets wider the worse the weather. :0)
--- Quote ---Evacuated tubes (wet or heat-pipe) can give you around 4 times that, and achieve decent temperatures.
--- End quote ---
If I have 10 or even 5 Kw of solar on teh roof, I don't think there will be many days in the year I'll have to rely on grid power for hot water if I go a PV system. I figure about 30 a year max. With the feedback I can get the rest of the time, I think I'll be far better off in the big picture. If I double my tank capacity, I can probably go 5 days with water of sufficient temp before I have to boost from outside sources. That said, I also have my own generatorS I can and will hook into the grid power to backfeed or if I want direct feed. I'm going to set my lister genset up in the garage and put on a transfer switch so I will be self sufficient if need be and can generate power during rainy periods if I want to still offset my grid consumption.
--- Quote ---
Don't count on your old analogue meter staying there for too much longer. As soon as you start using it to YOUR benefit (like, reducing your power bill), they'll be out to change it over. Either because they think it's gone faulty (and reading less power than you're using) or that you're running it backwards (which they don't want!).
--- End quote ---
No, I'm sweating that's what will happen when the owners of the new place disconnect and I re connect. I have already said to the Mrs that I will want it in writing the meters won't be interfered with as a condition of who we go with. They have wanted to change them here where I am and do the bare minimum to comply with the law as far as notice and compliance. The letter I got said they needed to do safety checks and Maintenance. A call and some very specific questions which they skirted around ( telling me they KNOW people don't want these things) uncovered that their real intention was to take away my spinny meter and replace it with a smartarse meter.
One " Supervisor" I spoke to whom thought he had all the pat answers, went on about saving me money and checking my usage at any time and all the rest of their predictable and parroted crap they use world wide.
I said to him, you really expect me to believe your company is spending tens of millions on equipment and installation that is going to loose them tens to hundreds of millions in revenue by reducing your customers bills when they could spend nothing and make more? Do you really believe that or is that what you have been brainwashed to believe or are you just hoping I'm stupid enough to fall for it?
Then I got the bit about being able to monitor my homes power use even from my phone. By this time I'm asking the guy if he's for real? I said I have better things to do in my day than check what time is the cheapest to do a load of washing. And as for phones, if they don't have a 30" screen I'm not going to bother looking at them, I'll use my computer but again, WTF makes you think I want to be checking my power bill all day and have nothing more important to do with my time?
Good job this was over the phone and not in person or I may have been tempted to smack the guy for insulting the little intelligence I have.
I plan to cut a hole in the meter box, put a perspex panel over the meters so they can be read and then lock the box securely. Technically illegal here to deny them access however the amount of cases where they have illegally swapped meters with no notice would make any any action on their part a very unwise move in negative media coverage I would create let alone anything else.
--- Quote ---There seem to be different interpretations of "net metering". A number of authorities add up the "numbers" and then charge you at their sell rate, or pay you at THEIR buy rate, on the net. That's not "net" in my view. Still, it's better than the alternative of selling ALL your power to them at their buy rate, and buying ALL your power from them at their sell rate!
--- End quote ---
Yeah, net to them means net profit and nothing else.
A big flaw I see in this net metering is Hot water.
Here off peak around the country is 11PM to 5am. where I am off peak is about 15C kwh all up. Where my father is it's about 20.
Almost universally, bar remote locations, the feed in tariff is 6-8C Kwh.
Therefor what happens is, you sell your solar at 8C kwh through the day but then even the cheapest buy back is 15C. Great deal for the power companies. NEVER seen them ever mention this little cash cow they have. Big Ra Ra about saving with solar but they have it sussed as always. They never make mistakes in the revenue improvement department.
Here I have the off peak connected and the heater coupled to the normal circuit. My current solar system is back feeding and winding the meter backwards so I get back what I give at the same rate which to me is only fair. Their malarkey about maintenance cost and distribution is just that, crap. It costs NOTHING to send the power I make next door or 10 houses up where it will be consumed because not everyone has solar and those that don't are more than putting in enough for maintenance. Of course that's just domestic, what about the megawatts used by factories and office blocks and people in units?
The power companies post tens of millions in net profit per QUARTER here. Can't tell me they need the money for maintenance and I'm doing them out of income when they are making all that profit. They want to jump on teh green bandwagon ( again purely for profit) then you stick to it. I'm making green power, saving loads of Co2 and all that garbage and also saving the company a heap of losses in transmission by giving them something they are selling every bit of at a LOWER cost than their own wholesale. If' its all about saving the planet and they charge so much more for " green " power, then why the heck aren't they paying me MORE for what I'm putting in not less!!
No, I have no compunctions about rewinding my meter what so ever.
The new place actually has one smart meter now on one of the 3 phases the home is wired into . Currently does the hot water peak and off peak, one leg of the AC and either the lighting or septic system.
First thing will be to remove everything from that phase including the water heater leaving only the AC which I need that leg being a 3 phase unit. That's OK, I'm happy to pay what I am here, about 150 a quarter just to keep from having to go off grid and not to arouse too much suspicion. The rest I'll move onto the other 2 phases which I'll identify to back feed. What I have looked up tells me that the smartarse meter on the place will register any back feed as a cost so I'll ignore that leg of the supply although If I am running the AC I can measure the draw on that leg and feed a limited supply to offset the grid cost.
Don't think I'll need to though. Should have the consumption low enough and I don't want a zero bill in fact.
MadScientist267:
--- Quote from: DJ ---Are these people mentally impaired to think that a few tea light candles are really heating a room? Are they too stupid or just so wanting to believe it works to do some simple research as to how much heat a candle generates and not see that their plasma TV generates a load more heat and does it at a fraction of the cost of buying tea candles?
--- End quote ---
I doubt I'll convince you otherwise, but while I haven't gone along with the whole "tea light" thing in whatever cultish forms it takes, I can attest that the pilot light of a propane heater is a viable source of heat under the right circumstances. I'll add to this by saying I didn't set out to exploit it from the beginning, it was noticed almost as an "irritation" of sorts, until I found the conditions that it is most useful in, and set out to exploit *those*.
As for the TV mention, indeed this is just as true. And while mine is almost never on these days (probably going to remove it soon even), I exploit numerous other "waste" sources of heat to augment space heating in winter. Namely, the fridge, inverter, charge controller, and laptop.
The fact is, heat is heat. It's the "final form" of energy that it all ultimately becomes, and aside from a bunch of magic tricks to keep it under control... in places we want it and out of places we don't, it's there, and adds up. Don't just make blind assumptions based on some theories that don't add up in your head.
There's a lot of crap out there, I completely agree. There's also a lot of goodies wedged in the cracks here and there. I've played with countless ideas in the thermal department, some my own, some borrowed from elsewhere, and everything in between. To the same end, the results have been everywhere from worse than useless to beyond what one would think is possible.
All that said, I'll leave it up to you to figure out how a whole 25W of battery power at night can let me cut the main propane burner off at night and let the main box cool down to save energy (and by extension in that case, *money*), all while making the difference that allows me to remain cozy in the process. Try and bust it all you want and say it doesn't work, won't bother me, I not only know *that* it works, but *how* it works, and *why* it works, despite the fact that at a glance, it appears "delusional". The word I used in a previous post was "finesse", I meant and maintain it.
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