*sigh* Retreat version II.

Back again after a marriage breakup last year, which threw a large, property-settlement-sized spanner into the works.

So, I've been drifting a little bit - as one does - and wound up in Tassie for a few weeks last month. I won't describe the events that lead me there in detail, but basically the here and now is this:

- Contract signed for a 4 bedroom fishing shack on 1300m2 on the Great Lake in Tasmania.
- Moving there from Queensland in about a month or so, just in time for winter, with a trailerload of possessions and a cat.

For a bit of an idea of what's there, check out my flickr photos.

All very nice, relatively solid (as shacks go),cheap-ish ($125K) ,good views, etc - but there's no power on. Basically, there's a 2kVA petrol genset powering the place, and nearest grid power is 20km away, so I need to whip up something in a hurry, otherwise that genny's going to drive me mad.

So, the current goal is basically enough solar power to do lights for a few hours a day, plus a TV / stereo for a similar length of time. The genset can stick around for the once a week washing/vacuuming/battery top-up use. As a rough guide, it'll wind up costing about $1500 for the bits to get to this stage.

I'll set out what I'm up to so far in the next few posts, in case someone can learn a bit from it. I'm an auto electrician by trade and I deal with electrickery :lol: all the time, so sing out if I casually gloss over some crucial detail and I'll explain further.

Cheers,
Dave

 

Looks good. Looks like you'll be putting a greenhouse in if you want any vegies.

 

DJ,

Good to have you back online, sorry about the bust-up and thanks for sharing those photos.

Now I am curious... were the sunny days on the beach and the snowfalls taken on the same trip?

The property looks excellent with nice views.

floot

 

Same trip floot - was quite pleasant the whole trip actually, only a grey day or two over the whole three weeks there. Weather systems seem to sweep in and out of Tassie rather quickly - you'd watch the weather on the news and today's map would show a front to the west of Tassie, tomorrow's would show it off over on the east towards NZ. Even the snowy day up in the highlands was fine really - it was 8 degrees on the porch at about 9:30. Was back there again two days later and you'd have no idea that it had snowed - fine and sunny. First cold snap of the year apparently....

As for the coast, not *quite* swimming weather for me, being a sooky queenslander, but there were are few people on the beach in the sun. Couple of crazy Canadians at wineglass bay having a swim, and the water certainly looked inviting - so clear! Not like the green murky stuff you get in the tropics.

As for growing anything... a glasshouse will be needed for any serious growing methinks, although there were a few misc. herbs (under wire mesh) growing round the back of the house ok next to the water tank. It's on my list,anyway. Need to build up some soil too, lotsa rocks. Seems about 7/8ths of Tassie is exposed rock....

 

As for the solar setup , I've a spreadsheet here with some numbers on it. They are the things that need to be run, sans generator, namely:

Lights, TV/Stereo, Laptop/Phone.

That's pretty much it! The fridge is a consul gas one , and a nice new one too. Which is good, as fridges are a big energy hog compared to everything else in a solar setup. The washing machine can run off the generator once a week, and any other misc small appliance doesn't really matter that much if I only use it a few minutes a day (eg shaver, blender, exhaust fan)

Now, during all this, I will be using a unit of energy, called "Watt-hours" (or Wh for short), just like it's bigger brother, the kilowatt-hour (kWh) you get on your electricity bill :lol:
1 Watt-hour is the amount of energy used by :

A 1 Watt light bulb for 1 hour, or,
A 10 Watt light bulb for 1/10th of an hour (6 minutes), or,
A 100 Watt light bulb for 1/100th of an hour (er, 36 seconds).
A 1 Horsepower motor (746 Watts) for about 4 seconds.

So, you can see a Watt-hour isn't that much, but it's a useful unit to use, as you'll see. So I will now work out how much power I'll need every day to use the things I want. Pretty much all appliances have a little nameplate on them showing their voltage and power rating, something like "240V 50W". Some may show current instead "240V, 1A" - multiply the Volts and Amps to get the Watts you need.

Anyway, onto the things I want to run:

Lights - an average of 20W of compact fluoro's + a few of those 4W lightbar LED's from the other retreat thread. For about 4 hours a day, on average. So that's 20 watts x 4 hours = 80Wh

TV - 75 watts for the TV, for 2 hours a day. 75 watts x 2 hours = 150Wh.

Stereo - 10 watts at normal noise levels, for 2 hours a day = 20Wh

My laptop + mobile phone - 25 watts, for an hour a day = 25Wh.

So all up, every day on average, I'll need 80+150+20+25 = 275Wh of energy. I'll round that up to 300Wh, to allow for "extra misc. usage" (eg. 300 watt blender for 10 seconds = 300 x 10/3600 = 0.8Wh)

Note that the TV - oh, that evil,unblinking eye! - is the biggest power user in the place for just a couple of hours usage..... room for improvement there.

Ok, so now I know that 300 Watt-hours a day is what I need to get by. Those of you looking at those 1kWh grid-connect systems - you should now have an idea of exactly what you could run off one. Plenty of energy-saving lights... not too much TV.

I'll leave it at that for this post.

 

Ok, with a requirement of 300Wh a day, time to look at the supply side of things.

There's a few options -

Wind - not sure on the site. Sheltered from prevailing westerlies by a low ridge. I've bought a small weather station (a Lacrosse WS1510-IT - $179 from eBay) to suss it out over the next six months.

Generator - Well, I've got one, and it would be relatively simple to use that to charge a battery bank for a couple of hours every few days. This will be my backup.

Solar - is what I'm looking at.

With solar, the first, most obvious question is, "Do I have enough sun?". If there's 8 months of overcast weather, all the panels in the world aren't going to help. The quickest way to find out is to go to the Bureau of Meterology site, in their climate section and poke about to find the nearest weather station.

For me, it's at Liawenee. "Mean daily sun hours" gives you a reasonable idea, as does the number of clear and cloudy days.

For me, it averages 6.6 hours of bright sun a day, over the whole year. The met boys measure this with a gadget that is basically a magnifying glass on a roll of paper, so only the bright sun is enough to be measured. In July, it's at a low of 3.5 hours/day, in December it's up to 8.9 hours a day.

So I'll work off the 3.5 hours/day, as it's down there for a couple of months a year. A 100 watt panel, in the sun for 3.5 hours, will put out approximately 100 x 3.5 = 350Wh of power a day, on average. With my base requirement of 300Wh/day, a 100 Watt panel is enough to get by on in the winter - the batteries may need topping up on occasion, but the genset will be running once a week anyway. Plenty of sun in summer - at 9 hours a day, that's 900Wh to use. Of course, these are all averages, so the batteries need to have enough reserve capacity to carry us over the lean times. Something to keep in mind.

A quick search reveals 100 Watt panels are expensive, pushing $1000 or so. But.... an array of 5 x 20 Watt panels from Oately Electronics is only $690 (+ freight), so, what the hell, I'll give them a go. It comes with a assemble-it-yerself regulator kit, but I'm planning to get a much smarter regulator, which I'll describe in the next post.

 

Thanks for the informal walk through your thought processes Dave, very educational and interesting reading.

Woz

 

Sorry to hear about your plans up north falling through Dave, good luck with the new venture.

Good onya for continuing the detailed solar info mate, I'm sure that will be helpful for a lot of people.

The Great Lake is a good spot, we mostly used to fish Arthur's Lake (brown and rainbow trout and massive eels) but I've also spent quite a bit of time fishing around at Todd's Corner on The Great Lake with good success. Worth getting a little tinny if you're into fishing because that should be able to take care of a fair chunk of your diet. You certainly won't run short of firewood up there, and give the tip a good check over regularly because we've found a few pleasant surprises up there.

It gets pretty hot up there in summer, so it's a climate of extremes like most highland areas - as I'm sure you're aware of. IMO you're right to plan for no sun days...in winter the weather really sets in up there. I haven't spent much time at Liawenee, but it should give you a reasonable estimate.

If you're going to haul soil in, you can get some pretty reasonable prices on a truckload. I was surprised at the price when I was up at Cradle and got a load of soil up from the NW Coast.

Watch out for the march flies once spring breaks!

 

A tinny is on the list Jez, boat ramp's about 150 meters down the road. Mind you, at 16 metres below full at the moment, it's a long way to the water. I'm relatively used to extremes - used to deal with 0 to 40+ at Mount Isa without too much hassle....

Anyway, the solar regulator turned up in the post yesterday arvo.
It's a 40 amp "Conergy SCC 40 Vision" , via eBay, for $230 + $18 for pretty quick freight. A general idea of it's capabilities can be found here

Yes, it's rather expensive - I could buy a solar charge regulator for $75 - but there are reasons behind that :

- 40 amps charging capacity (about 480 Watts) is big enough that I can upgrade with extra panels later on , and not have to get another regulator.
- Does the full range of battery charging - bulk/absorption/float/equalise to make sure the batteries are all good.
- It can control your load (again up to 480 Watts), switching it off if the battery gets too low.There are variable low voltage cutoff points, with a self-adapting one that changes the cutoff point if it thinks the battery is getting flattened too often, helping make your batteries last longer.
- Similarly, it can switch *on* an extra load if the battery is fully charged and all that sunlight's going to waste. Eg, a water pump to pump to a header tank.
- It has a "night-light" function that can switch off the load a certain time after sunset, and a certain time before sunrise - so you can turn pretty much the whole system off between, say 10pm-6am automatically. This helps to prevent the "oops I left the porch light on overnight and flattened me battery" problem.
- It has an inbuilt data logger that can store a year's worth of info about power in and power out, number of low voltage tripout's etc.
- It has a relatively informative screen on the front that tells you the state of charge (roughly).

For $230, it's actually pretty decent, and hopefully one of the more longer-lasting bits in the system as things get upgraded. There are basically 6 wires to hook up - two from the solar panels, two to the batteries, two to the load.

So that's the charging section sorted out. Of course, you actually need something to charge up, which is what I'll cover next.

 

this sort of detailed, specific discussion is absolute gold.
Well done, I look forward to more of your posts.

 

This topic is very interesting! I look forward to reading your future posts.

Could you elaborate a little on this?

 

Bulk/Adsorption/Float/Equalise are the four stages a lead-acid battery should go through to charge for the longest life.

Bulk - is just that, the charging system crams as much power in as possible. Battery voltage will rise as the battery charges, normally up to 15V or so, when it will normally be about 80% charged. A bit of bubbling in battery cells generally happens.

It then switches to :

Adsorption - this is a final "top-up", at a high-ish voltage, about 14.7V or so, normally once the current tapers off, the battery is considered full. A fair bit of bubbling in cells happens here.

These two stages normally take about the same amount of time, so the last 20% or so is quite a drawn-out process.

After the current drops off, the charger switches to :

Float - normally at 13.8V, this maintains the battery at 100%. Should be bugger-all current going in, and no bubbling of cells at all. Batteries usually can sit indefinitely at this point for years with no degradation.

Which leaves Equalise, which is a bit of a special case.
In batteries, you have a number of cells joined in series - 6 cells for a 12 volt battery. They're never quite the same in storage capacity - one cell might be a fraction smaller, one a fraction larger. But they all get the same charging current, as they're in series. So after a few dozen cycles, cells tend to wander a bit and some will end up being flatter than others, which is bad for their lifespan (flatter cells wind up with less capacity, which makes them flatter next time, and so on). And you can't just chuck out one cell from a 12V battery - they're all in the same case! So, equalisation is a deliberate overcharge of a battery. The charger will aim for 16 volts or so, for a few hours, and this will bring all the cells up to full capacity and thus they are all balanced and in sync with each other again. It also stirs up the acid in each cell which helps cell performance a bit.

Normally you only equalise once every few months, or when you notice a cell has a lower reading than the rest with a battery hydrometer (the thing with the squeeze bulb and the float). If the cell fails to 'come up' in line with the rest of the cells in the battery, you've a weak cell on your hands, and that's the time to think about a new battery.

Hopefully that makes some sense. Battery theory takes up many pages in any decent textbook, so you'll have to deal with the abridged version here.

 

Following on from my previous post, we're up to an important part of an off-grid system - batteries.

I need 300 Watt-hours a day of power. If it's sunny at my place for more than 3-4 hours a day, it's all good, the panels will generate more than that. But they can't put out more than 100 watts at any given time, and of course, they don't work when it would be really useful to have power, namely at night. So, you need batteries to store the excess energy for use later. As such, you need to size them correctly and take into account a number of important factors.

The first thing is to determine how long you want your system to run for with no power being generated. Typically , 5 days is used for an off-grid system - enough time for the weather to clear a bit generally, or long enough between generator starts to not be too much of a nuisance.

So, 300Wh/day by 5 days gives 1500Wh of battery capacity needed.

Batteries are normally measured in amp-hours (Ah) - so you multiply by the battery voltage to get watt-hours. A typical 4WD battery is 70Ah, thus giving 70 x 12 = 840Wh. Two of them in parallel (that is, side-by-side, plus to plus, minus to minus) to give a total capacity of 1680Wh and you'd be right, right?

Not quite. Funny thing about lead-acid batteries is that they don't like to be used. ("So, what's the bloody point then?", I hear you ask...) If you use up all their capacity and charge them back up (one full cycle), well, next time there's a little bit less to take out. And the next time a bit less than that. If you're using normal car batteries, well, you might get 20 to 30 full cycles out of them before they hold very little charge at all. So, when sizing a battery bank for your system, there's one simple rule : More is Better.

The batteries I'm looking at are Trojan T105's. Let's look at the specs.

- They are 6 volt deep cycle batteries, originally made for things like golf buggies. "Deep Cycle" meaning they are specifically made to be run nearly flat, unlike typical car batteries. They're a 6 volt battery, so you need 2 in series ( end to end, positive to negative ) to make a 12 volt system.

- They are rated at two different capacities : 225Ah (1350Whr) at a 20 hour discharge rate and 250Ah (1500Whr) at a 100 hour discharge rate. The two differing ratings is because of the inherent inefficiency in a battery - the more current you draw from it, the less total capacity you have to use. Going from those ratings, I could draw (225/20) = 11.25 amps for 20 hours before it went flat, or I could draw (250/100) = 2.5 amps for 100 hours before it went flat. Extrapolating from that, I could probably get 275Ah from the battery if I only drew 1 amp out (for 275 hours), and 180Ah if I drew 20 amps out (for 9 hours). So, it's something to keep an eye on when comparing/sizing batteries - make sure you're using the correct discharge rate. If you're using a big load, like a 1000 watt inverter (about 100 amps at 12 volts), this becomes important.

- They are also rated at 750 cycles to an 80% depth of discharge (that is, 20% remaining) and 1825 cycles to 25% depth of discharge (still 75% full). So, here is the most important tradeoff when making a battery pack. I can buy more (or bigger) batteries now, not flatten the total pack as much, and they will live longer. But batteries are expensive, so by not buying as many, I could save a bit of cash up-front but have to change batteries more often. This is why you don't use car batteries, unless they're free.

With my system, I need 1500Wh to get my 5 days of runtime without sun. Two 6 volt T105's in series gives me 12V at 250Ah or 3000Wh. This means my 5 days with no sun will only half-flatten the batteries, thus I should get about 1000 cycles out of them, or 3-ish years even if they were only charged once every 5 days. In reality, I have no idea of how many 5 day periods I'll get with no sun, but I'll wager that it's not *that* often. In summer,with 9 hours a day on average, I should only be discharging the batteries 10-20% overnight (200Whr or so), so it's quite possible the batteries will last 5 or 6 years before they start to get weak. It also gives me a little bit of extra reserve - so I can hold out for 8 days ( 3000Wh * 80% / 300Wh a day) if I wanted to. Seeing as I'll be running a generator for a couple of hours every week regardless, this will be fine for me. At about $500 for two of them, it's not too bad for 3 to 5 years life.

Well, that's the batteries. It's probably the trickiest part of the whole thing - and probably the worst part to bugger up, as a battery bank will cost you a lot in replacement batteries if you get the depth of discharge wrong. But you can't accurately size the batteries without going through all the previous stuff I've mentioned, so sing out if anything doesn't make sense.

After this, I'll move onto the bit that all this gibberish has been for - the loads.

 

This is a great discussion. I'd been thinking of buying a grid connected system, but having read this, if I can supply some of my power needs with a standalone system, that'sw the way I'd like to go.

would you be able, as the story progresses, detail the other hardware required to get the system up and running and how it all goes together. I'm sure there is plenty of literature out there but your posts are very easy to understand and i'm hoping a resonable practical person could get such a system going.

Cheers

Steve

 

Well Steve, I've got about another 3 weeks to get all the bits together, then I have to assemble it all there. I'll be documenting all the bits'n'pieces needed (and any other bits I need at short notice).

Coincidentally, the inverter + cabling + a few misc bits turned up today. I ordered a 300 Watt inverter from Jaycar, 10 meters each of red and black 8GA cabling and 4 x 50 Amp Anderson plugs.

Connected the inverter to a small mower battery - it works. Back in the box it goes for the trip down. I have a spare already (a 1000 watt one), but that one won't be used as it's standby draw is in the order of 12 Watts or so. Doesn't sound like much, but that's 200Wh a day if it's on 16 hours a day. Which is nearly what my panels will put out in winter....... the standby current on the new one is about 4 watts,which is 64Wh a day - a lot lower. Its the little things that get you in a solar setup.

The cabling is of a suitable size that I can do the run from the panels and the inverter/battery wiring with it. I plan to put the panels on the shed where the generator is, and the inverter inside in a different room from the generator. The cable run should be about 3 or 4 meters, tops. I may yet put them on the northern side of the shed near ground level - so's I can clear the snow off. :lol:

You want to size your cabling so that there's minimum loss by the time you get your power to where you want it. Cabling has a fixed resistance, measured in Ohms per metre. You want to figure out how much is lost along the cable as heat, so that you don't spend $700 in panels to electrically heat your woodshed instead of lighting your house. This is Ohm's law at work.

Ohms law is basically :
Voltage Drop (in Volts) = Current flowing (in amps) x Resistance (in Ohms)

Remember also that :
Power (in Watts)= Volts (Voltage drop, in our case) x Amps

So putting the two formulae together, you can get :
Power lost = (Current x Resistance) x Current again, or
Power lost = Current (squared) X Resistance.

So with a certain resistance of a wire, and a certain current flowing, you can determine the power lost in Watts (as heat in the wire). This is why you have high-voltage power lines - by increasing the voltage, you reduce the current needed to transfer the same amount of power. By reducing the current, you reduce power losses due to resistance of the wire, and you end up with powerlines that have half a million volts at 10 amps spanning the country. Wish they would span a little further to my place, so I didn't have to sort all this out!

So, firstly, the bulk of my loads will be supplied by the inverter. The power lost along 240V wiring is minimal, so I'm happy to leave the house wiring as-is. I'm sure my local electrical authority is happy about that too, athough 30-year-old shack wiring is a little bit..... iffy sometimes.

The main DC currents will be:
- Panels (100 Watts at 12V - 9 amps)
- Inverter (600 Watts peak at 12V - 50 amps)
- Battery charger (600 Watts peak at 12V - 50 amps)

The wiring to the panels will probably be 3 to 4 meters. I'll say 4 meters. So, this is 9 amps along 8 meters of 8GA wire in total (4 meters positive and negative). 8GA is an archaic indicator of wire size (thank you, Imperial system), in which lower numbers are bigger. 8GA is about 4mm2 of copper, or what you'd find hanging off the back of the alternator in your car. And for good reason.

(A quick note about wire sizes - as most ladies will tell you, ignore any claims about size. Most automotive wire sizes seem to include the insulation as well,which strangely enough, doesn't conduct electricity and gives you a false impression of the current a wire can carry. Alleged "4mm2" automotive cable has a lot less copper than the stuff I'm using. Usually on the side of the roll it will tell you the true conductor size.)

Anyway, the specs for the wire state it has a resistance of 0.00252 Ohms per metre. Sounds like bugger-all, and it is, until you do long runs or high currents.
Thus, with the power loss equal to Current squared times Resistance and 8 meters of cable, you get:
9 x 9 x 0.00252 x 8 or 1.63 Watts lost along the cable.

The general rule (well, it's *my* rule) is that if you have any more than 5% loss (compared to what you're transferring), you should get thicker cable that has less resistance. 1.63 Watts out of 100 Watts is pretty ok. Gives me a bit of leeway, so that when I increase the number of panels in the future, I don't have to increase the cabling size. Cable is expensive. All that shiny copper...

The batteries will be enclosed in a box and vented to the outside to keep explosive gases down. The other bits will be on top of the box. The regulator is in the middle, with the batteries, panels and inverter all connected to it.

All up, I would expect there to be about a metre of wiring here and there around the batteries in total. So, losses in the wiring from the batteries to the inverter, at 2 metres of 8GA cable at 50 amps is 50 x 50 x 0.00252 x 2 = 12.6 watts. Still only about 2%, but I wouldn't want to go much further. The 600 watt figure for the inverter is a peak load, so normally the loss here would be a lot less, at least half or a quarter of that. Remember all these losses could be powering your lights instead of heating your shed - a 13 watt compact fluoro is pretty bright!

Finally, I want to use the 4 x 50 amp anderson plugs to make a small extension lead that will connect my car (an ageing Hyundai Excel, bless it's Korean heart) to the battery pack. More importantly, it will connect it's alternator to the battery pack so I can top the pack up with the relatively quiet car as opposed to a roaring old genset. There'll be a socket near the house batteries, a socket under the bonnet, and a small-ish lead with matching plugs on each end to join the two. Best part about Anderson plugs is that there's no male/female version, they will all plug into each other and keep the polarity right.

I'll have about 5 metres of cable (again, positive + negative, 10 metres all up) from the car to the batteries, and I expect that about 40 to 50 amps will flow when the car's running. So, again it's 50 x 50 x 0.00252 x 10 = 63 watts. This is a fair chunk of lost power - about 10%. You'd probably find that the cables would get a little warm after a while too. I will let it slide, simply because of the fact that I won't be doing it every day, and the next size up cable is significantly more expensive. I will attempt to keep the jumper lead as short as possible though.

So this is the wiring and load calculations done with. There are a few final bits that I've gotten from here and there, and I'll describe them in the next post.

 

Re: *sigh* Retreat version II.

Solar panels turned up yesterday - pulled them out of the box and had a good look at them. All seem to be OK, look to be well sealed against the elements. Tested one with a 12V 21W stoplight bulb in full sun, lit up brightly. 5 x 20W seems to be a standard quantity from the manufacturer, as there were "proper" styrofoam holders in the box, which looked like it was shipped unopened from some Asian country. Also came with a basic solder-it-yerself regulator kit, which I don't really need.

Got a quote from a guy near Deloraine for two T105 batteries - $257 each. Have also ordered 3 x 10A circuit breakers and a 50A breaker ($22 each), plus a housing to hold them in ($24). Also got a generic 200Amp battery isolator from a boating/camping/fishing shop for $12.

I'll do up a diagram later,but basically :

- The isolator will disconnect the batteries from the system. It also has a set of auxiliary contacts that can be used to cut the power from the panels as well, to completely shut off power to the whole system in one hit.
- The 50A breaker is the main breaker from the batteries, before the regulator (The regulator has a built in electronic 40A cutout. Don't trust your house to it, put a fuse/breaker in as well.)
- One 10A breaker will be for the panels.
- One 10A breaker will be for a few small DC loads.
- One 10A breaker will be for the things I have forgotten/later use.

This will hopefully keep the fires at a minimum. Before you think I'm kidding, I've melted a few cables (and spanners!) over the years discovering that fuses and isolators are a Good Thing (and that other people have left them out...) At the very least, fuse your batteries - they are quite capable of making battery cables act like bar heaters for a good 5 or 10 minutes before they explode.

Anyway, that's enough for me today!

 

Re: *sigh* Retreat version II.

Dear dgriffith,
I just want you to know that, along with many other appreciative readers, I'm finding this thread extremely valuable.

Surely this is where the power of the Internet lies, in connecting people and sharing knowledge. I really appreciate your patient, by the numbers, explanations which I find clear and empowering.

In the not too distant future I plan to build a rural home for my family and have been researching many aspects of design and construction, from passive solar orientation and straw bale walls to rainwater harvesting and solar hot water. I'm not sure that my family are ready to live off the electricity grid just yet but it's finding people like you and threads like these which makes me think it's possible.

Please continue.
Warm regards
Nigel Haslam

 

Re: *sigh* Retreat version II.

Thanks for that Nigel, I'm glad someone's getting something out of it - even if it eventually winds up as a warning for others :lol: But seriously, once you have enough power for lighting and a few small appliances, the rest of the power-sucking modern appliances don't seem to be as important.

Well, the big day slowly approaches - down in Tassie now, waiting for the paperwork to clear before moving in.

Went to Agfest (a yearly agricultural show) yesterday, wandered all through the place - got a price for a set of T105's from a local battery shop in Launceston - $240 each. Also picked up a 15% discount voucher, which makes it just over $400 for two of them. Interesting to see a 55 watt amorphous solar panel there for $449 ($559 normally)... got my 5x20 watt panels for $690. The amorphous panels are pretty big for the power they put out - it would have been about a metre square - the 5 panels I have are about the same in total area and they have twice the output.

Also bought a mini-greenhouse while we were there, from a company called Cyclad Buildings. Small (3 shelves of 3ftx3ft sqaure), lightweight, double-walled polycarbonate sheets for glass, access by sliding windows from two sides. Will put it in a sunny spot in the yard, stick a min/max thermometer in it and see how it goes growing a few things. From observing the weather so far, we seem to get a few days of clear weather, an overcast day, then a few days of clear weather again.

Sussing out a similar design that can go on a side wall of a house, like a conservatory. We've got an extra northeast wall/door on the new place that it might be able to fit onto nicely.....

 

Re: *sigh* Retreat version II.

Hello again,

Your mini greenhouse experiment sounds like a good idea.

The key passive solar element of my future home design is a large solar greenhouse and in my trawlings I found this web page interesting..

https://www.survivalplus.com/foods/page0009.htm

The website is a survivalist one, so there are some fairly 'out-there' ideas elswhere on the site but as far as maximising solar use is concerned the topics covered by the solar greenhouse page are pretty good.

I did bookmark another page which had many solar greenhouse ideas but I've lost the link. I think it was one of the home power type sites. If anyone has some good links for solar greenhouses, perhaps you could post a few up here?

Cheers

Nigel

 

Re: *sigh* Retreat version II.

Thanks for the link Nigel - there's a few ideas that I can put to use there.

One of the other things I'm looking at is using the excess heat from the wood-stove wet back hot water heater circuit to warm a bedroom at the far end of the house. The previous owner has said that the hot water gets "bloody hot" and will boil "after a couple of hours". The hot water tank looks to be 40 gallons or so.

The problem is that the room is a good 40ft away,at the other end of the house and the hot water tank is level with the stove. There's no crawl space in the roof, so for easy pipework it'd have to go under the floor - there's a foot or so gap under there.
I want to regulate the temperature of the tank to an acceptable level, to avoid people getting burnt when they turn the tap on, and it's wasted heat if it's just boiling away. Thermosyphon is out due to the pipe layout, so I'm looking at getting one of these. It's relatively low power - 1.3 amps or about 15 watts max.

This will circulate water from the hot water tank to a normal hydronic radiator in the room when the temperature in the tank goes above a certain temperature. You can use a special controller ($$) that will continuously vary the pump voltage to keep the temperature you want, or just a simple thermoswitch in an on/off arrangement..... which is what I'll probably do.

I don't really want to power this from my solar setup - every watt counts.
So to power all of this, I'm going to try something different - using a peltier cooler module from one of those car cooler/warmer boxes to convert heat from the stove directly to enough power to run the pump. These modules are cheap ($20 or so) and while not exactly their intended use, are apparently usable to some extent 'in reverse'. Seeing as they normally need 60 watts to run normally (to heat/cool), even with terrible efficiency it should put out enough to spin the pump (hopefully!). To do this, it needs to be hot on one side and as cool as possible on the other, so I will clamp it between the stove and a big finned heatsink on the other and see what comes out. Should be interesting to see how much power it can put out, if any.

Real (as in 'designed for this') thermoelectric generators can be found here and are nearly-cheap-enough that I can go with one from their shop if mine doesn't cut it.