Living offgrid with small solar system(s)

[KonaRain]

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

Right! I've been in many areas in Hawaii with small window units, which are pretty warm when run as a fan only..then as I turn down the temp / thermostat make that click and then shudder ..

We, our hosts and us, had two Mitsubishi in the bedrooms,

and I think they were very efficient.

I just thought of walking past apartments, and getting warm air blown on legs from window units. .

Fond memories. ..

Edited May 4, 2016 by KonaRain

[KonaRain]

@ naam..

Warm air out..

Old units do it, Mitsubishi do it..

And naam do it..

Birds do it, bees do it. .

Didn't mean to disagree with crossy. .

Aloha everyone!

[Muhendis]

@ naam..

Warm air out..

Old units do it, Mitsubishi do it..

And naam do it..

Birds do it, bees do it. .

Didn't mean to disagree with crossy. .

Aloha everyone!

Crossy is absolutely right if he, as I suspect, is talking about split A/C units. That is with one heat exchanger on the outside and another on the inside of the building. The inside unit blows room air through it's heat exchanger which is cooled like a freezer by a compressor mounted in the outside unit. The internal room heat exchanger takes heat from the room air and transfers that heat to the outside heat exchanger which passes it into the environment. No air is sucked from the room so we can all still breath ok when the air con is running.

Why does the inside air lose it's moisture? Go to google and read up on latent heat.

Why does a fan make you feel cooler? Your body makes the local air warm and the fan blows it away. Also there is a pressure change caused by the fan blades as they pass through the air. This removes some of the heat but maybe not enough to compensate for the wasted heat from the inefficiency of the fan motor.

[Naam]

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.

what have i done to you that you torture me? did i kill your sons? did i rape your daughters? did i kidnap your dog?

are you genetically handicapped?

[George Harmony]

I think you are @naam.

If you have a fan brtween 2,000 cfm and 6,000 cfm it quickly exhaust the hot indoor air, allowing cooler outdoor air to enter through the windows. Once the house has cooled off, the fan can be turned off and the windows closed. Most people who have whole-house fans keep their windows closed from early morning until evening, so that the cool air inside the house doesnt escape.

So how about trying to get cooler air during a hot day thus not through windows during cooler evenings. Thats im trying to figure out. Blow colder air from a freezer perhaps hehehehe

[Gary A]

I think you are @naam.

If you have a fan brtween 2,000 cfm and 6,000 cfm it quickly exhaust the hot indoor air, allowing cooler outdoor air to enter through the windows. Once the house has cooled off, the fan can be turned off and the windows closed. Most people who have whole-house fans keep their windows closed from early morning until evening, so that the cool air inside the house doesnt escape.

So how about trying to get cooler air during a hot day thus not through windows during cooler evenings. Thats im trying to figure out. Blow colder air from a freezer perhaps hehehehe

How about we try a different tactic. We keep the warm air in and let it go through the air conditioner to make it cool?

[Naam]

your torture does not work anymore George even though i have a huge whole-house fan, an attic exhaust fan and 8 small exhaust fans. 3 of the small fans run permanently, the others when required. except for running the whole-house fan in the cool season none of the fans are meant to "cool" the house but to replace used air with fresh air.

p.s. as of now i will use your comments on thermo-physics and engineering for entertainment purposes only

[Gary A]

Naam, you should investigate the solar powered attic fans. That is an ideal application. The fans run fastest when the sun shines brightest and that is normally when the attic is the hottest. No batteries, switches or timers required.

[George Harmony]

Up to you @naam.

Fans,whatever type it may be, are not ment to cool a space

Hmmmm.....

Perhaps this is also for you as entertainment.....

http://www.investinganswers.com/personal-finance/smart-consumer/old-fashioned-trick-can-slash-your-summer-cooling-costs-4391

Or this: http://m.wikihow.com/Use-Window-Fans-for-Home-Cooling

Edited May 4, 2016 by George Harmony

[Crossy]

Fans do not cool. Period!

However, as illustrated by the above links, they can be used to move cooler air into your occupied spaces.

They also provide air movement, which can assist the body's natural cooling system (evaporation of sweat).

[Muhendis]

Fans,whatever type it may be, are not ment to cool a space

Well done George. Fans move air. They have very little if any actual cooling effect. If the air they are moving comes from a cool place and is blown into a warm place then the warm place gets cooler and vice versa. The fans themselves don't have any significant cooling effect on the air.

Dam! Crossy got there first

Edited May 4, 2016 by Muhendis

[Jing Joe]

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

\For what its worth; Some council authorities in Aus maybe in more commercial situations used to stipulate a minimum of about 15% fresh air introduced.

Some larger air cons used to have the option with a push rod and a small air flap for this.

[Jing Joe]

Surprising how much air goes up the 300mm x 2m high chimney/vent here. The Chinamans hat on top only need small breeze across to suck so much air sometime that the fan at the lower end of the tube could just about generate power if it were DC.

Painted black it might be even better at passively venting and imagine if it was 3 or 4 m high, the chimney effect would increase. Food for thought George even higher. Then again there is that 500m (??) high tower that does produce power somewhere.

Edited May 4, 2016 by Jing Joe

[Naam]

Naam, you should investigate the solar powered attic fans. That is an ideal application. The fans run fastest when the sun shines brightest and that is normally when the attic is the hottest. No batteries, switches or timers required.

Gary,

my policy is "don't fix it if it ain't broken!" my two attic fans, each ½hp one on timer the other one manual, are doing a proper job. most important is that the installation was done ok, meaning never any leak even when heavy rains were combined with high winds.

moreover, a solar powered fan could not perform the secondary but important task of running in the evening 2-3 hours after sundown.

[Naam]

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

\For what its worth; Some council authorities in Aus maybe in more commercial situations used to stipulate a minimum of about 15% fresh air introduced.

Some larger air cons used to have the option with a push rod and a small air flap for this.

all old style "wall/window units" had this option. all of them were exhausting about 5% of the rated airflow. split units don't have that option.

[Jing Joe]

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.

Probably the first solar hot water in Oz was a backyard guy about 1948 using thermo syphon principle and was the only way till suitable pumps became available. K.i.s. keep it simple you bet. He probably developed the concept from the very popular combustion stoves with their wet back copper tank(or hair pin shaped tube) in the fire box. Given suitable diameter panel pipes, interconnecting pipes, and the difference in general elevation let alone the minimum difference from top of plate to bottom of storage tank(About 500mm?) they really worked very well. Night time back syphon didnt happen. I rented with one for 6 years and was great. Cant remember how they bled the dissolved gasses/steam out.

The obvious advantage of pumps allowed the storage below the plate but night time back cycling needs addressing.

Edited May 4, 2016 by Jing Joe

[George Harmony]

If the air they are moving comes from a cool place and is blown into a warm place then the warm place gets cooler and vice versa.

This is what i mean. A fan is an instrument which you can achieve a cooler space, lower room temp.

Ofcourse the fan itself does not lower a room temperature. It can blow warm air out and it can blow cooler air in.

In the evenings in many areas its colder. Blow that colder air in and try to hold it as long as possible.

Now im still figuring out how can i blow colder air in during a hot day for example at noon without using an aircon. One has to create cold air. Evaporate cooler is not effective in humid areas. Cold air from freezers also not...hehehehe.... Any ideas??

[Naam]

lukew@rm engineering f@rts won't cool either

[George Harmony]

a solar powered fan could not perform the secondary but important task of running in the evening 2-3 hours after sundown.

why not?? With a bit diy sure it can if you connect to a battery.

[Naam]

those who can, respectively are willing to read have clearly an advantage and refrain to make useless suggestions

my comment referred to this posting:

Gary A, on 04 May 2016 - 17:00, said:

Naam, you should investigate the solar powered attic fans. That is an ideal application. The fans run fastest when the sun shines brightest and that is normally when the attic is the hottest. No batteries, switches or timers required.

[George Harmony]

Suggestion...very simple...ever heard about relay...use it.

Regards,

George

Added/edited:

Or timer ....

Edited May 4, 2016 by George Harmony

[Jing Joe]

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.

YES YES YES. Probably the first solar hot water in Oz was a backyard guy about 1948 using thermo syphon principle and was the only way till suitable pumps became available. K.i.s. keep it simple you bet. The hotter the sun; maximize the flow automatically. No sun; no flow. He probably developed the concept from the very popular combustion stoves with their wet back copper tank(or hair pin shaped tube) in the fire box. Given suitable diameter panel pipes, interconnecting pipes, and the difference in general elevation let alone the minimum difference from top of plate to bottom of storage tank(About 500mm?) they really worked very well. Night time back syphon didnt happen. I rented with one for 6 years and was great. A 2 gallon cistern with float valve water inlet kept pressure low on the tank and a goose neck copper pipe vented steam.

I used a goose neck here for years then changed to the steam release device we discussed about 20 pages back. The obvious advantage of pumps allowed the storage below the plate but night time back cycling needs addressing.

Edited May 4, 2016 by Jing Joe

[Gary A]

When I was planning a new house, the solar unit and tank were going on the roof. The roof in that area had to be reinforced because the unit and tank weighed more than 300 KG. The only pump was the household unit on the ground. Mixing valves were required. My wife decided she would be satisfied adding on and remodeling our existing house. I was a little disappointed but it saved me a LOT of money.

[George Harmony]

We did talk about alternatives for aircons.

Attached pict you can see heating elements which i used in NL before. According to a dutch company its possible to cool a room when such elements are filled (pump around) with cold water when there is also an efficient condensate drain system.

Is it true??

[splitlid]

This thread is sooooooo painful. Please stop.

[Naam]

This thread is sooooooo painful. Please stop.

[Crossy]

We did talk about alternatives for aircons.

Attached pict you can see heating elements which i used in NL before. According to a dutch company its possible to cool a room when such elements are filled (pump around) with cold water when there is also an efficient condensate drain system.

Is it true??

For similar heat-exchange efficiency the water inside will need to be as much cooler than your ambient as it was warmer than your ambient when you used it as a heater. Say a delta-T of 30C, so your water would need to be about 5C here.

Unless you have a deep bore that produces ample water at 5-7C you need a means to cool down the water and a circulating pump.

Once you've done that you have something called a chilled-water air-conditioner!

http://www.slideshare.net/taratitz/airconditioning-repaired

As noted earlier, you cannot change the laws of physics, it's all been done before. If there was a magic and cheap means of cooling your home significantly below ambient you would be able to go and buy it in HomePro. There isn't, so you can't.

What you CAN do is move cooler air around and reduce heat gain during the hot period. Use fans, shade, ventilation and light weight materials (which don't retain heat), just like the locals have been doing for centuries.

[Jing Joe]

Fans,whatever type it may be, are not ment to cool a space

Well done George. Fans move air. They have very little if any actual cooling effect. If the air they are moving comes from a cool place and is blown into a warm place then the warm place gets cooler and vice versa. The fans themselves don't have any significant cooling effect on the air.

Unusually hot weather here causing a twist to my regular season/automatic solar situation. The sun now enters nearly 2 metres across the floors on the glassy north side of house but makes the well insulated house too warm so I'm needing fans to get that air out and let the cooler air in. So in this twist, the fans are moving cooler air as you guys have discussed. The way the seasons are going I'll need winter time shade to stop the sun. How bizarre. But there's hope for cooler weather with snow predicted for July, much further South.

[Jing Joe]

This thread is sooooooo painful. Please stop.

Splitlid I'm sure is joking and you Naam have enjoyed it with the laughing icon. Good on ya. It actually is a credit to the whole mob that by page 33 now after George started it rolling, that speaks volumes how it is really not boring as splitlid jokes.

We've all learnt to remain "gentlemen" with Naam leading the way, and sooo much about Georges question "living off grid with small solar systems". This would have to be a TVN record? well done guys.

[Jing Joe]

APETLEY ---Referring to your post #802--- Keep thinking about the simplest design as you do.

Other than generous pipe sizes, there is one factor I forgot; the steeper the angle of the plate obviously augers better for the turnover of the tank contents. This is really the "thermal pressure pump" if you'll allow. This would give George some grief how to set it, he being right on the equator? Can you enlighten us please George? What is the best angle all year round for steeper (as suggested) solar hot water panels without a pump and indeed solar P/V panels when fixed all year round?

Edited May 5, 2016 by Jing Joe