Author Topic: Blasphemy..... Solar power.  (Read 148451 times)

Nonni

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Re: Blasphemy..... Solar power.
« Reply #300 on: December 12, 2017, 11:09:24 AM »
This is all certainly interesting, but it's hard for me to understand. I heard the opinion from my friends and read many articles about the advantages of water heaters (if you would be interested one of them https://www.newtanklesswaterheaters.com/7-myths-tankless-water-heaters-need-stop-believing/). I'm interested in how much battery power and what do I need to connect tankless water heater, and not worry about the electricity bill....

AdeV

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Re: Blasphemy..... Solar power.
« Reply #301 on: December 12, 2017, 05:02:53 PM »
They're talking about gas-fired combi boilers. Solar panels might run the igniter and the pump, but it won't replace the gas....

To run an "instant" electric shower you need between 7.5 and 10.5 kW at around 230V~; that's a 40-45amp breaker, if your PV battery setup is at 48 volts, you're looking at supplying a constant 200amps to run your shower. That's pretty meaty, and I'm not entirely sure there's an inverter built to cope with that, and you'll need a beast of a battery bank to power it...

Nah - if you're going off-grid with solar, you're FAR better off heating a big tank of hot water using direct solar energy, rather than making electricity then using that to heat the water. Then simply mix with hot & cold under gravity (or pump) for your actual shower. Or use the "bush shower" idea that Mike showed in another thread.
Cheers!
Ade.
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BruceM

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Re: Blasphemy..... Solar power.
« Reply #302 on: December 12, 2017, 05:53:25 PM »
Try builditsolar.com to get better educated on solar hot water. 

On demand gas h/w for a backup to solar is reasonable, if your water mineral content is suitable. On demand uses lots of surface area of fine tubing to quickly transfer a LOT of BTUs to the water.  This small tubing is vulnerable to scale and mineral build up so it's a bad choice for some water sources.  The flow sensing to turn on the gas and flow/temp gas regulation has also been failure prone on some models for some water sources.

So depending on the unit and water mineral situation, on-demand can be a far cry from the reliability of the old electronics-free tank with pilot and burner, with it's inherent low efficiency (about 60%) due to stack heat loss. (Vent stack inside tank creates thermosiphon of air to cool tank 24/7.)


basewindow

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Re: Blasphemy..... Solar power.
« Reply #303 on: December 12, 2017, 09:04:56 PM »
I've had an 'Off Grid' place for a good few years now,  being there 3 days a week, four back at home (still have to work unfortunately). Its only a small place with one bathroom with shower and bath and sink, small kitchen, small laundry. So a total of 4 hot taps. I had the same dilemma when installing hot water. After much consideration i ended up going with an propane (LPG) on demand unit. I used a Bosch Hydro Power 16 for several reasons.

Pros: Reasonably cheap to purchase(compared to other models/brands), easy to install and maintain, quite efficient on gas(over tank and pilot based system), requires no extrnal elecricity to run. Instant* hot water (after about 20 seconds of cold)
Cons: Takes some getting used to in operation, one part is prone to failure and expensive to replace, as the units are not manufactured and used to the same degree as the normal grid connected units, parts are harder to come by.

Efficiency wise its one of the things that uses the least gas, probably becase it only gets used 2 to 3 times a day for short showers, washing dishes etc. The gas fridge uses more.

I dont have to heat a tank full time when im not there or wait for it to heat up once I get there if I turn it off.

The part that fails quite often  is the is the small water turbine that creates a spark to ignite it once water starts flowing. It is well documented. I purchased mine 2nd hand and it failed after 2 years. The parts are available but hard to find and from memory cost around $250 au. But there is a work around, that although not perfect worked for me. Simply replaced the power source with a couple of D cell batteries with a switch to inside. Switch on hot water. Batteries last about six months.

Requires a certain flow rate to ignite, so hot water has to be turned on first and cold added to reach the required temperature. A bit fiddly sometimes when you want a shower.

Im sure there are better more reliable units available but I was doing this on the cheap.

Its all pressurized to 30psi and uses a small on demand 12v pump, Flojet or similar.

I thought of solar hot water in its various forms, hot water solar panels and tank on roof, gas assited solar, the old layers of black tubing on the roof. It either got needlessly complex or too expensive.

There are many other options off gridders use as well that aren't solar related.

Just my experience for my circumstances.

1953 CS Lister 3.5hp, 1938? Bamford SD1 3.5hp, 1962 Fordson Super Dexta, 1969 International 434.

starfire

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Re: Blasphemy..... Solar power.
« Reply #304 on: December 12, 2017, 09:36:06 PM »
We call these things a caliphont here in NZ, and can highly recommend them. Mine is a "Rinnai" brand, it uses 2 D cells to run the igniter, these last around 5 years.. Despite its cheap appearance, it has served me with no issues at all for 17 years. It has many  safety features,  a 20 minute timer that limits the time it can run.... in case a pipe bursts etc. It will shut down if water pressure drops, and requires a minimum flow rate of 2 liters a minute. This runs my shower, and kitchen tap.. I use around 9 kilos of LPG in a 6 week period, showers every night. One nice feature is the instant hot water when the tap is turned on.... no waiting cause they can be mounted close to the tap.  Also saves money on not needing a shower mixer, the water temperature is adjusted  on the caliphont instead, and will hold its setting very accurately over time. The flow rate can also be adjusted with a second knob.
Rain water is fine for these, after all, rain is distilled water and has no added "goodness" unless you live in a some polluted place.

buickanddeere

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Re: Blasphemy..... Solar power.
« Reply #305 on: December 14, 2017, 08:19:53 PM »
Due to to high retail rates in Ontario that support the subsidized whole rates to solar, wind and natural gas generators . A do it yourselfer with some solar panels and a grid tie inverter can break even during the air conditioning and pool pump season.

starfire

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Re: Blasphemy..... Solar power.
« Reply #306 on: December 15, 2017, 09:22:16 AM »
My Lister has not run for months, the solar panels daily are giving 30 amps for around 5 hours, obviously tapering off morning and evening as the sun moves around. Given the capacity of my battery bank, thats as much as I can store, in fact most is now being wasted. I may change to a 48 volt system next year if this global warming thing takes off, its improved our weather enormously, thanks to all the high emission Lister owners. There is something hugely satisfying making and consuming ones own power.

Tom

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Re: Blasphemy..... Solar power.
« Reply #307 on: December 15, 2017, 05:35:55 PM »
A 40 gal electric is a good place to dump a lot of extra power when the batteries are full. We use one to preheat the water before it goes into the gas heater.
Tom
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LowGear

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Re: Blasphemy..... Solar power.
« Reply #308 on: December 15, 2017, 05:44:18 PM »
I think Tom's excess storage method is why PV is often recommended over direct hot water generation.  Once everything is warmed up then the water collector is through for the day.  PV continues to provide storage or grid credits.  Of course it's tough to beat the ROI of a coil of HDPE on the roof.
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mikenash

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Re: Blasphemy..... Solar power.
« Reply #309 on: December 15, 2017, 07:51:42 PM »
I think Tom's excess storage method is why PV is often recommended over direct hot water generation.  Once everything is warmed up then the water collector is through for the day.  PV continues to provide storage or grid credits.  Of course it's tough to beat the ROI of a coil of HDPE on the roof.

Casey, when I built the shed/house/workshop outside which the coil of HDPE lurks I put in a lot of time in the planning stages - going out  to the site in winter and driving pegs into the ground to see what the sunshine did in relation to trees and hills etc, and I looked up the govt stats on sun elevation at the lowest midwinter point and the highest midsummer point and drew up some side elevations, then when building I put a big overhang porch on the building, but set up about four metres high - so the low summer sun come in underneath it and shines all the way in through all of the glass in the front and the high summer sun is shaded by the overhang etc etc

I reckon commonsense stuff like that gives you a big head-start on low energy requirements

Just my $0.02  Cheers

mikenash

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Re: Blasphemy..... Solar power.
« Reply #310 on: December 15, 2017, 08:02:27 PM »
Actually, Casey, I got sidetracked during the typing of that reply by a call from a client who had torn off a hydrant riser from his irrigation system.  The sun is shining, the irrigator has stopped and his sense of urgency translates into an early-hours Saturday call to me . . .

What I was going to say is you can't beat the ROI on good planning . . .

Especially when, like me, you don't have any investment funds and your labour is your investment and your future leisure is your return

Cheers

dieselspanner

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Re: Blasphemy..... Solar power.
« Reply #311 on: December 16, 2017, 08:32:06 AM »
Up here in the Pyrenees the locals have been building solar efficient houses for hundreds of years.

They are long and thin, east to west, facing south. a balcony on the south side, as Mikenash describes, inset on both floors with few to no openings in the north side.

Around a quarter of the length, is the dwelling the rest is the sheep barn with a hay loft above. There is always a small door between the kitchen and the sheep pens. so you don't have to go outside to tend to the animals, very useful given we can get a metre of snow in a few hours sometimes.

Around 50% have an asymmetric roof with the steeper side to the south in order to make the most of the winter sun to warm the bedroom or the hay loft.

I remember the trumpeting in Milton Keynes (UK) when they started solar passive building 40 years back, should have popped down here first!

Cheers Stef
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buickanddeere

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Re: Blasphemy..... Solar power.
« Reply #312 on: December 16, 2017, 05:37:26 PM »
I think Tom's excess storage method is why PV is often recommended over direct hot water generation.  Once everything is warmed up then the water collector is through for the day.  PV continues to provide storage or grid credits.  Of course it's tough to beat the ROI of a coil of HDPE on the roof.

Casey, when I built the shed/house/workshop outside which the coil of HDPE lurks I put in a lot of time in the planning stages - going out  to the site in winter and driving pegs into the ground to see what the sunshine did in relation to trees and hills etc, and I looked up the govt stats on sun elevation at the lowest midwinter point and the highest midsummer point and drew up some side elevations, then when building I put a big overhang porch on the building, but set up about four metres high - so the low summer sun come in underneath it and shines all the way in through all of the glass in the front and the high summer sun is shaded by the overhang etc etc

I reckon commonsense stuff like that gives you a big head-start on low energy requirements

Just my $0.02  Cheers

Around here with freezing temperatures . It is cheaper and less trouble to use solar PV to power resistance water heaters .

mikenash

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Re: Blasphemy..... Solar power.
« Reply #313 on: December 16, 2017, 11:06:36 PM »
It's fascinating the solutions folks have found - especially those without much money.

All those years of experience and learn-by-mistake

I wonder what the mean age of folks on this forum would be?

Cheers

LowGear

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Re: Blasphemy..... Solar power.
« Reply #314 on: December 17, 2017, 06:39:24 AM »
Quote
It is quite ironic that despite having a power shortage almost country wide here, the gubbermints are in fact detering people putting PV on their roof.

I don't get it either.  It happens all over the US as well.  There are companies specializing in stand alone pool pumps here to get around the long arm of the power utility.  When you think 4 hours a day at 750 watts is 3 KW a day of 1.20 here 365 days a year and you have $438 a year.  I wonder when oil will start to go up because it's more expensive to run plants at 60%?

Quote
I reckon commonsense stuff like that gives you a big head-start on low energy requirements

It sounds like a big head-start on many endeavors.  I like to believe there is as much commonsense today as there was during the time of Benjamin Franklin.  Unfortunately there are too many people today so that limited supply can get spread out pretty thin.
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