Living offgrid with small solar system(s)

[George Harmony]

Found a link with many diy examples like per attached pict.

http://rikif.com/solar-water-heater-diy/

[Naam]

Like this one @naam. If its effective, why not??

YES! very effective. but the hose is wound too tight. there should be a distance of 1-2cm which would considerably increase the efficiency (more hose surface exposed to radiation and ambient temperature).

[Muhendis]

Found a link with many diy examples like per attached pict.

http://rikif.com/solar-water-heater-diy/

My first thoughts about this one were the extra weight that the roof needs to support. Those tanks look like 200 Litres each so that's 400 kG plus the steel frame.

This is my setup. It is a flat panel heat exchanger made with copper pipe and aluminium fins encased in a wooden box with polycarbonate cover. size is about 1.2M square. The small pv panel supplies power for the circulation pump and monitoring electronics. The storage tank is 200 litre stainless steel with 50mm insulation. You will notice the temperature probe in a little cutout. Temperatures are usually in the low 40's which is a hot shower. Sometimes the water can be well over 50. The associated wiring is a bit scruffy because I'm too lazy to sort it out, having more interesting priorities to consider.

[KonaRain]

Solar water heater is ^^ above, or Olin brass/black panels which are 98%wet.. or a water sandwich to out it another way. Interestingly, George's method..let us know, okay?

[KonaRain]

Olin brass panels, (2) will make 160 f water which is stored in tank that loses 6 degrees f in 24 hours..

I'm outta charge on my phone..Aloha

[apetley]

Found a link with many diy examples like per attached pict.

http://rikif.com/solar-water-heater-diy/

My first thoughts about this one were the extra weight that the roof needs to support. Those tanks look like 200 Litres each so that's 400 kG plus the steel frame.

This is my setup. It is a flat panel heat exchanger made with copper pipe and aluminium fins encased in a wooden box with polycarbonate cover. size is about 1.2M square. The small pv panel supplies power for the circulation pump and monitoring electronics. The storage tank is 200 litre stainless steel with 50mm insulation. You will notice the temperature probe in a little cutout. Temperatures are usually in the low 40's which is a hot shower. Sometimes the water can be well over 50. The associated wiring is a bit scruffy because I'm too lazy to sort it out, having more interesting priorities to consider.

I've always thought about using a heat exchanger like that but even simpler. How about one at ground level and using the thermosyphon effect, heat rises, to let the hot water rise into a hot water tank higher up in the house, no need for the pump then.

[Naam]

I've always thought about using a heat exchanger like that but even simpler. How about one at ground level and using the thermosyphon effect, heat rises, to let the hot water rise into a hot water tank higher up in the house, no need for the pump then.

recirculating the water for best efficiency requires a pump.

[apetley]

I've always thought about using a heat exchanger like that but even simpler. How about one at ground level and using the thermosyphon effect, heat rises, to let the hot water rise into a hot water tank higher up in the house, no need for the pump then.

recirculating the water for best efficiency requires a pump.

Agree a pump is more efficient at recirculating the water but interested in just how a effective a minimalist solution may be. The temperature of water in a garden hose can be unpleasantly hot so here in the tropics I suspect a passive siphoning effect of the hot water could warm a tank reasonably quickly.

Interested to hear from anyone with a better knowledge of physics who can crunch some numbers on the subject

[Muhendis]

I've always thought about using a heat exchanger like that but even simpler. How about one at ground level and using the thermosyphon effect, heat rises, to let the hot water rise into a hot water tank higher up in the house, no need for the pump then.

recirculating the water for best efficiency requires a pump.

Agree a pump is more efficient at recirculating the water but interested in just how a effective a minimalist solution may be. The temperature of water in a garden hose can be unpleasantly hot so here in the tropics I suspect a passive siphoning effect of the hot water could warm a tank reasonably quickly.

Interested to hear from anyone with a better knowledge of physics who can crunch some numbers on the subject

You don't need much physics to understand that heat rises. Having the panel lower than the storage tank will give you free circulation. Water is heated in the exchanger the hotter water being at the top then flows up through a pipe and into the top of the storage tank. Cold water from the bottom of the storage tank goes down a pipe into the bottom of the heat exchanger.

My system needs a pump because I wanted the heat exchanger on the roof. So with the storage tank below a pump is required to circulate the water. The pump also ensured flow of water even when temperature difference is not so great.

[George Harmony]

From warm water to cooling. Ive been wondering before whether its possible to have a combined fridge or freeZer and aircon in one. Here is a guy who did it. Do you think if it will cool a small room of lets say 5x6 or even 3x4m ??

https://m.youtube.com/watch?v=go-5AINpUFY

[Naam]

From warm water to cooling. Ive been wondering before whether its possible to have a combined fridge or freeZer and aircon in one. Here is a guy who did it. Do you think if it will cool a small room of lets say 5x6 or even 3x4m ??

yes it will... provided you have a grid connection to refreeze the content (duration depends on room's heat load) and are willing to pay 25-50% more for energy input than achieved cooling capacity.

[Naam]

I've always thought about using a heat exchanger like that but even simpler. How about one at ground level and using the thermosyphon effect, heat rises, to let the hot water rise into a hot water tank higher up in the house, no need for the pump then.

recirculating the water for best efficiency requires a pump.

Agree a pump is more efficient at recirculating the water but interested in just how a effective a minimalist solution may be. The temperature of water in a garden hose can be unpleasantly hot so here in the tropics I suspect a passive siphoning effect of the hot water could warm a tank reasonably quickly.

Interested to hear from anyone with a better knowledge of physics who can crunch some numbers on the subject

your theory has one big flaw. what you described would only work if the same amount of water is drawn from the tank which rises from the lower positioned heat exchanger.

[Muhendis]

I've always thought about using a heat exchanger like that but even simpler. How about one at ground level and using the thermosyphon effect, heat rises, to let the hot water rise into a hot water tank higher up in the house, no need for the pump then.

recirculating the water for best efficiency requires a pump.

Agree a pump is more efficient at recirculating the water but interested in just how a effective a minimalist solution may be. The temperature of water in a garden hose can be unpleasantly hot so here in the tropics I suspect a passive siphoning effect of the hot water could warm a tank reasonably quickly.

Interested to hear from anyone with a better knowledge of physics who can crunch some numbers on the subject

your theory has one big flaw. what you described would only work if the same amount of water is drawn from the tank which rises from the lower positioned heat exchanger.

Absolutely Naam! When the flow rate is regulated by temperature difference between hot and relatively cold masses of water and the only outside influences are the heat input and the thermal losses, then the point of equilibrium becomes unpredictable. The presence of a speed controlled pump does not overcome the temperature differential problem. But it certainly speeds things up a bundle.

[Muhendis]

I've always thought about using a heat exchanger like that but even simpler. How about one at ground level and using the thermosyphon effect, heat rises, to let the hot water rise into a hot water tank higher up in the house, no need for the pump then.

recirculating the water for best efficiency requires a pump.

Agree a pump is more efficient at recirculating the water but interested in just how a effective a minimalist solution may be. The temperature of water in a garden hose can be unpleasantly hot so here in the tropics I suspect a passive siphoning effect of the hot water could warm a tank reasonably quickly.

Interested to hear from anyone with a better knowledge of physics who can crunch some numbers on the subject

I did the minimalist solution as an experiment in the UK. It was a reasonably nice sunny day and the convection effect started. I left the system to itself for a few hours but it took a disappointingly long time for the convection to build up. I used the same heat exchanger as the one in the picture but the water in the reservoir was only about 40 litres. One of the first things noticed after about 4 hours was the expansion of the volume of water and the increasing flexibility of the reservoir tank (it was a cheap, plastic expansion tank). I didn't bother to measure the temperature of the water because the object of the test was to determine what would happen in a convection system however, the water temperature did rise to a bit higher than lukewarm from something like 15 deg C. My flat panel would never be a goer in the UK but in Thailand? Well as so many have commented. A bit of hose pipe left out in the sun would do an admiral job.

[George Harmony]

Electricity usage of a Freezer

A standalone freezer is a box powered by electricity used to freeze food similar to a refrigerator freezer, standalone freezers typically provide more space than fridge freezers. Older freezers will use over 100% more energy than newer Energy Star rated models, a modern freezer will use between 100 and 400 watts of power, with 200 watts on average.

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@naam, why i must have a grid connection if i m later able to run it with a solar system and re-freeze it when ever i want. Most offgrid examples ive seen run a fridge or freezer.

So what that guy on the vid do is blowing cold air out from the freezer. Lets say he can close it also if he dont use the blower and its again insulated. Perfect or not. When its hot and you want cold air just blow it and your products in the freezer remain hopefully cold.

I m seriously thinking of planning that 260watt aircon setup but if this setup also works i have then also a fridge/freezer.

[Naam]

@naam, why i must have a grid connection if i m later able to run it with a solar system and re-freeze it when ever i want. Most offgrid examples ive seen run a fridge or freezer.

@Indo-Redneck,

before and instead of asking questions based on silly Redneck ass-umptions i suggest to use a little logic considering the facts as specified hereafter:

-estimated content of freezer 400 liters,

-estimated delta t input water temperature > usable ice = 40ºC,

-energy required to achieve afore said delta t = 16,000 Kcal

-required electric energy = ~16.5 kWh

now it's your turn to calculate how many m² of solar panels will need what time to harvest the 16.5 kWh.

[George Harmony]

My dad learned me:

Better ask questions than not ask queations no matter how silly they sounds.

Thought has nothing to do with ice and just use the cooling part of the freezer also when inside its empty.

Anyway, thanks for your answer. A fact is that my skin cant become red but yours can hahahaha

[Naam]

Thought has nothing to do with ice and just use the cooling part of the freezer also when inside its empty.

please give me a break George, i beg of you. i am a heart patient!

we have a slightly smaller chest freezer that draws 80 watts. it's not rocket science to calculate the potential cooling capacity in btu/h and compare it with the usually available smallest aircon unit having a capacity of 9k btu/h drawing about 10 times the energy.

but here's an idea for you which saves solar panels and rice cookers. all what you have to do is changing your diet to a high protein one.

[George Harmony]

Herr naam,

Im in process to expand my exhaust fans and also to install a powerful attic fan. Warmer air can also escape from the sides of my ceiling which will be sucked by the attic fan later. This all only to cool my small living room where i am most of the time. I intend to install some small fans under my floating dressoir on the colder ground nearly invisible for guests and low noise. Perhaps also all around the room. If this all will not be enough im wondering how to get some colder air in and saw that example of the freezer. Im pretty much aware that sucking warmer air out the room is essential. Ive seen examples of dye cooler with ice and/or copper pipes and a fan. One has to make ice for this. Or will the cold part of a freezer also blow cold air in.

[Naam]

Mijnheer Redneck,

i answered already your question pertaining to the freezer. please be kind enough and ask your secretary to read for you my post #768.

as far as your other ideas are concerned i refrain from commenting as i don't want to violate forum rules (Crossy is watching us!).

you should also be more careful publishing brilliant engineering ideas (home airconditioning) for which you have no patent protection. i am afraid that Muhendis, Jing Joe, IMHO and others might use them without paying you any royalties.

Edited May 3, 2016 by Naam

[IMHO]

Herr naam,

Im in process to expand my exhaust fans and also to install a powerful attic fan. Warmer air can also escape from the sides of my ceiling which will be sucked by the attic fan later. This all only to cool my small living room where i am most of the time. I intend to install some small fans under my floating dressoir on the colder ground nearly invisible for guests and low noise. Perhaps also all around the room. If this all will not be enough im wondering how to get some colder air in and saw that example of the freezer. Im pretty much aware that sucking warmer air out the room is essential. Ive seen examples of dye cooler with ice and/or copper pipes and a fan. One has to make ice for this. Or will the cold part of a freezer also blow cold air in.

I haven't live in Indonesia before, but here in Thailand I would say that roof extraction fans are 99% a waste of time.

To ventilate the attic, use ventilated soffits. Your house is a BIG sail even in the smallest breeze, so just use nature to do the ventilation

As for sucking air our of rooms and into the attic, all making a hole in your ceiling really does is give the expanding hot air in the attic somewhere else to go: your room, instead of out the soffits.

The best way to keep your house cool is, open the doors and windows in the morning when the air is actually cool, then close them all tight during the day. Use good insulation in the ceilings to prevent heat making it down, avoid window orientations that allow direct sunlight, don't make ANY holes in your ceiling at all, and ventilate the soffits to help keep attic temps lower. Of course, also use a radiant barrier under your roof tiles/sheets, to help mitigate as much heat getting into the attic in the first place, and shade your roof / walls with trees and/or PV panels.

Edited May 3, 2016 by IMHO

[George Harmony]

There is a case of this guy who have

Algemene productdetails

Maximale capaciteit (m3) 90 m3
EAN 4250058311634
Merk Suntec
SKU 11634
Verschenen in 2009
Algemene kenmerken
Type Portable
Type gas R 410 A
Koeling
Maximale BTU (koeling cap. per uur) 9000 BTU
redelijk weinig
Maximale koelingcapaciteit (KW) 2,6 KW
redelijk weinig

When he burns 4 lamp the aircon gives an error and the temp in his space quickly rise to over 30. He thought of buying a fan to blow MORE air out and use this aircon to blow cold air in cause even if he put blow air out on max and cold air on min from this aircon it does not help. He tried several things and reaches only 3 degrees C colder.

Another guy suggested to put the movable aircon outside and not inside the room. Seems to help.

So @naam,... 9000 BTU and all that theoretical talk for a small space seems perfect but in this case it does not help. Warm air must be sucked out. Im not ready yet and temp difference is already 5 degrees C. But when its 34, its still 29 C.

Auf wiedershen.

[George Harmony]

There is a case of this guy who have

Algemene productdetails

Maximale capaciteit (m3) 90 m3
EAN 4250058311634
Merk Suntec
SKU 11634
Verschenen in 2009
Algemene kenmerken
Type Portable
Type gas R 410 A
Koeling
Maximale BTU (koeling cap. per uur) 9000 BTU
redelijk weinig
Maximale koelingcapaciteit (KW) 2,6 KW
redelijk weinig

When he burns 4 lamp the aircon gives an error and the temp in his space quickly rise to over 30. He thought of buying a fan to blow MORE air out and use this aircon to blow cold air in cause even if he put blow air out on max and cold air on min from this aircon it does not help. He tried several things and reaches only 3 degrees C colder.

Another guy suggested to put the movable aircon outside and not inside the room. Seems to help.

So @naam,... 9000 BTU and all that theoretical talk for a small space seems perfect but in this case it does not help. Warm air must be sucked out. Im not ready yet and temp difference is already 5 degrees C. But when its 34, its still 29 C.

Auf wiedershen.

[IMHO]

There is a case of this guy who have

Algemene productdetails

Maximale capaciteit (m3) 90 m3

EAN 4250058311634

Merk Suntec

SKU 11634

Verschenen in 2009

Algemene kenmerken

Type Portable

Type gas R 410 A

Koeling

Maximale BTU (koeling cap. per uur) 9000 BTU

redelijk weinig

Maximale koelingcapaciteit (KW) 2,6 KW

redelijk weinig

When he burns 4 lamp the aircon gives an error and the temp in his space quickly rise to over 30. He thought of buying a fan to blow MORE air out and use this aircon to blow cold air in cause even if he put blow air out on max and cold air on min from this aircon it does not help. He tried several things and reaches only 3 degrees C colder.

Another guy suggested to put the movable aircon outside and not inside the room. Seems to help.

So @naam,... 9000 BTU and all that theoretical talk for a small space seems perfect but in this case it does not help. Warm air must be sucked out. Im not ready yet and temp difference is already 5 degrees C. But when its 34, its still 29 C.

Auf wiedershen.

Portable aircons suck. Buy a proper split system, which recycles the air in the room only, and does not need any "fresh air" in because it's not wasting air out.

[Naam]

So @naam,... 9000 BTU and all that theoretical talk for a small space seems perfect but in this case it does not help. Warm air must be sucked out. Im not ready yet and temp difference is already 5 degrees C. But when its 34, its still 29 C.

i have no idea what you are talking about and what the reference to "this space" means.

[George Harmony]

@naam,

In this case a space of 2.4x2.4m only.

I forgot to paste the link for this case. In dutch: http://www.wietforum.nl/topic/101065-wat-is-beste-zwaardere-airco-of-grotere-afzuiging/

[KonaRain]

Aloha! I still like the vented Mitsubishi aircon that we had in C.Mai..We had it on highest temp setting for a rather small room. Ceiling fans work pretty well for livable space.. when too hot get a cool shower to cool body temp... do some cooking, then back to to cool room..

Actually, the fans in the living room were ok MOST of the time. .

[Naam]

So @naam,... 9000 BTU and all that theoretical talk for a small space seems perfect but in this case it does not help. Warm air must be sucked out. Im not ready yet and temp difference is already 5 degrees C. But when its 34, its still 29 C.

"this case" is the case of absolut ignorant people who don't get 9,000 btu/h from anywhere because they are not recirculating.

we have two 9k btu/h installed in our home, one in my wife's bathroom ~14m² and one in the former maid's room ~16m² where my engineer/handyman cum wife's drive sits. both areas can easily be cooled down to 22-23ºC if necessary even if ambient temperatures are 35º, but it takes of course a few hours.

note: only suckers suck continously warm air out and replace with ambient hot air which is of course only slightly cooled down. in your case, if without airconditioning the result will be even worse.

again i would like to remind you 'why not apply a little logical thinking before coming up with assumptions such as -warm air must be sucked out- that do not apply?'

[George Harmony]

I thought aircon sucks warm air and through a process blows/circulates cool air in again. As mentioned in the case above,you can blow cool air in as much as you want it does not effect the room temperature if you do nothing against the warm air. Dont know if this is true. One thing for sure is that an attic fan certainly helps for cooling between your ceiling and roof.

Ive made this test. Around noon, nearly no wind, all curtains, windows and doors open. Very hot outside and a 20wp panel gives 17+volt as an indication and all fans are out. After 1.5 hours i measure the inside temp. Then i closed windows and doors,close curtains and run the fans and exhaust fans. See the attached pict.

Not a representative test but a la......

[Crossy]

A regular aircon takes warm air from the room, cools it, then returns it to the room. No sucking out of anything.