[pea-jay]

$this->bbcode_second_pass_quote('mistel', '
')
I thought to start I would set it to come on as little as possible then increase the times as neccessary. I set it to come on for two hours in the morning then two hours in the evening, 6 to 8. We have had times when we run out of hot water, but I can just flip a switch and it will turn on until the next shut-off time. And when we run out of hot water, it doesn't go cold suddenly, it merely is less hot. So I have left it at 4 hours a day and it has been fine. I think I may be able to fine tune it even more so that it only comes on in the morning long enough to heat the tank, maybe 20 mins?

I wish I had keep better track of my electricity bill so I could post some numbers, but what I am saying is that it was really surprising how little it needed to be on.

We are a family of 4, two adults and two young kids so right now our hot water needs are low.

Peter

[frankthetank]

If i got a water heater that consumes a certain wattage, and i want to heat water at x degrees to y degrees, how long should that take? I guess i'm looking for a formula or something.

water heater=4500 watts
x=60F
y=120F

looking for time? Do i need more info?

[Twilight]

Energy required (J) = mass of water (kg) x specific heat capacity of water (J/kg/K) x difference in temperature (K)

Q = mc(T2-T1)

Time taken (s) = energy supplied (J) / power of heater (W)

t = Q/P

The specific heat capacity of water is 4200 J/kg/K.

You have not specified the quantity of water, but a litre should take 31 seconds.

[frankthetank]

I knew i'd forget something.

I'll plug my numbers in and see what i get.

Thanks. I googled, but couldn't come up with correct keywords to find this equation. Lots of smart people on this board, so i knew it wouldn't be much trouble

[frankthetank]

Anyone have the plans.

I was thinking:

2x4's for the frame (size?)
Plywood for the back (3/4 inch?)
Insulation (foil foam board-1 inch)
Copper piping (3/4, 1/2)
Black high temp paint
Exterior paint the frame
Caulk?
Some type of black metal mesh?
Glass

I want something ultra simple. Might just want to use it in the warm months. Not sure exactly how this would "plug" into my existing setup.

My thought was just to route the cold water up into this thing, bring it back down into a storage tank(?) that would feed right into the hot water heat??? Would my well pump push water up to the roof?

I've looked at some diagrams, but still not sure.

I've got a bunch of 3/4 pipe leftover from my recent plumbing job and have most of the tools and i know how to solder Also have a 39 GAS hot water heater(17 yrs old/not being used)...

Have a perfect south facing rooftop location.

Heres where my thinking came from:
http://www.fieldlines.com/story/2006/4/9/14621/53240

[steam_cannon]

$this->bbcode_second_pass_quote('frankthetank', 'A')nyone have the plans...

...I want something ultra simple.

[culicomorpha]

[quote="steam_cannon"]
Beer Bottle Solar Hot Water Heater

http://tinyurl.com/ywv4ug
http://www.kk.org/streetuse/archives/im ... echnology/
[quote]

Oh wow, this is the coolest thing ever! It's so.... so.... low tech! I love it!

[steam_cannon]

$this->bbcode_second_pass_quote('culicomorpha', '')$this->bbcode_second_pass_quote('steam_cannon', '
')Beer Bottle Solar Hot Water Heater

http://tinyurl.com/ywv4ug
http://www.kk.org/streetuse/archives/im ... echnology/

[kpeavey]

To test roof water pressure, get up on the highest point of the roof with a garden hose and a 5 gallon bucket, have someone turn on the water. If you can fill the bucket in less than 2 minutes, you should be fine.


About 5 years ago I started working on a solar hot water system in the spring.

The simplest was a garden hose laying in the sun. The hose was getting up to 105 degrees just sitting there. 100 degrees is comfortable enough for bathing or for shaving. 105 is about the minimum for washing dishes.

I measured the amount of hot water from a 50' hose, came out to be about a gallon and a half or something like that. This is enough for shaving, a sponge bath, a few dishes.

My next step was more garden hose. I have a friend who operates an apartment complex, people leave garden hose behind all the time. I put together 200' of garden hose. I was getting more than 4 times the hot water. As the length of the hose grew, the time the water took to get through it increased. The water had time to pick up heat as it travelled through, giving me the unexpected increase.

At this point, I began to unplug my water heater, relying on the sun to heat my water for free when the opportunity appeared. Run the hose into the kitchen, dishes get done. It took 45 minutes to an hour to reheat. I put the end of the hose through the bathroom window, had enough for a bath. I could empty the hose into the tub, let the hose reheat, do it again, have a full bath. The tub did not cool as fast as the hose reheated.

As summer came, the water got hotter, reheated faster. A problem developed with the garden hose bursting from the ongoing heating/cooling and the pressure that came with the heat. Another plan was needed. I turned to PEP tubing in 100' sections, 150 psi, cost was about $9, now over $20. Its the stuff the landscaping guys use for irrigation of lawns at the homes of the swell people.

It did the trick. I moved it to the concrete driveway. Being black and dull it increased the water temp to about 115. I have 500; of it in the driveway in a coil about 7 feet across. This was done over several months, another section being added now and then. On a hot sunny day in the summer, the thing gets HOT! I've measured 120-125 on a hot sunny day with no breeze. I can easily run it for 10-15 minutes continually before it cools down. Not being able to regulate the temperature of the incoming water I am relegated to using the tub rather than the shower.

I shot the lock off the wallet, picked up some pluming parts, ran the hot water line from the washing machine to the greenhouse. I added a spigot in the greenhouse. This enabled me to shut off the water at the hot water tank, hook the hose up to the spigot, turn on the outside faucet. Instead of running a garden hose through a window, I open the tap, take a bath, wash dishes, even hot laundry and the dishwasher will work.

As summer turned into fall, the water temp was not getting as high, finally peaking at a point where it was not useful. This takes the thing to the next level: Storage.

I started with a $10 trash can, 34 gallons, in the greenhouse and a $15 pump. I filled the trash can with water, dropped in the pump. The water was pumped from the tank through the tubing and back to the tank. If the sun was out, I plug in the pump. The result was a tank that would reach anywhere from 90 to 120 degrees. The greenhouse was heated overnight as the trash can released its stored energy. Damned effective I must say. The pump runs on 8 watts of electricity. Running the thing 5 hours/day to account for the shade trees across the driveway, 30 days/month, 12 cents/kilowatt hour, heating the greenhouse costs less than 15 cents per month.

I added some foam rubber insulation around the tank as the heat is generally released in the first 6 hours of night, I want it to last until morning when the heat is needed most.

Never lost anything to a frost inside the greenhouse unless the roof was blown off. During the coldest part of the year, the greenhouse and the tank have gotten down to around 40 degrees, when it was 20 outside.

I added a timer. It turns on the pump when the sun landed on the hose coil, turned it off when the big oak casts its evening shadow. The thing will operate when there is no sun. If the tank is warmer than the outside air, it will actually lose heat. I ended up taking the timer out and plugging it in manually. An untested enhancement to this system would be to run the pump off a solar panel. When the sun is up, the tubing heats, the pump turns on. Have not yet gotten to that step.

One day the trash can sprung a leak, it was replaced with a 55 gallon plastic drum. first trials with the bigger drum had it reaching temps of 80 degrees. I had increased the storage mass but not the collector. I got lucky one day when I was turning this guys porch into a sun room. He had a spare 4x20 solar pool collector, sold it to me for 50 bucks. A couple of boots and some pipe clamps and I was back in business.

I use the collector running from the spigot to the hot water in the house in the summer. I use the collector and tank for heating the greenhouse in the winter.

This is the current state of the system. There is lots more to go.

The collector section needs to be increased by a factor of about 2 at least to offer stored heat for on demand hot water. More tubing is a simple matter. I also built a glass covered box, which I intend to run some tubing through in order to boost the intensity of the heat. Initial tests have given me 175 degrees. Unfortunately the heat melted the urethane joining the double pane glass to the aluminum frame, then I hit it with a rock. I'll get that fixed. Tilting the collector to an angle of lattitude + 15 degrees would maximize solar gain during the coldest part of the year

The tank can be improved by increasing its mass. This means adding brick/block/stone, maybe some flattened aluminum cans. After that, a bigger tank or multiple tanks.

With sufficient collection and storage, I should be able to run a copper coil through the tank. Run from cold water, through the tank coil, to the house hot water line, I should have hot water on demand. Not sure if I will need to stir the tank when the brick mass has been added.

Extending the system to its logical conclusion, I should be able to heat the house in the winter. The math says I need a collector area the size of the fence, 40x6, and a tank of about 1500 gallons of storage. Add in baseboard radiators, a thermostat, popcorn and a movie.

The power for the pumps in the house system would require 48 watts of 110v electricity. Grid tied 24/7 would run me $20/month.

So far I have maybe $300 invested in the project, and I've put it all together with off the shelf parts. I have another $180 for 100' of copper tubing yet to be installed. I have estimated a complete house system to be from $2k -$4k. My neighbor spent $6k for central heat and AC added to her house, has a handsome electric bill. If I move, I can take everything with me.

Operating a roof system during the summer would have the effect of removing sunlight heat from the house, offering a cooling benefit. I have no data to support this, but it makes sense to me that it would be a cooler house

Some Numbers for the Geek inside us all:
collector area 108 sqft
Insolation: 856 BTU/sqft/day, Dec flat ave, US Navy data
daily exposure=92448
max gain of 55 gallons in the tank, starting at 44 degrees, end at 117=73 degrees, 440 pounds=32120 BTU gain, giving me 34.7% efficiency

Storage capacity of 100 degree tank, 40 degree min GH temp=24000 BTU
volume of greenhouse 8x8x8=512 cuft
GH BTU/cuft=46
House heat demand: 200k BTU/day
house volume 9500cuft
house BTU/cuft=21
I have twice the heat per unit volume in the greenhouse than I do for the house. I'd sleep out there but the house does not cool down to 40 degrees by morning. That and theres bugs in it.

-US Navy data is in kWh/m2/day
To Convert kWh/m2/day into BTU/sqft/day multiply by 317.2


Good Luck

[steam_cannon]

$this->bbcode_second_pass_quote('kpeavey', '.')..So far I have maybe $300 invested in the project, and I've put it all together with off the shelf parts. I have another $180 for 100' of copper tubing yet to be installed. I have estimated a complete house system to be from $2k -$4k. My neighbor spent $6k for central heat and AC added to her house, has a handsome electric bill. If I move, I can take everything with me.

[Mesuge]

$this->bbcode_second_pass_quote('steam_cannon', '
')
It reminds me of this soda can room warmer...

http://tinyurl.com/37j5le

[Mesuge]

Solar thermosyphon>>

The author claims from $350 (hardware only) thermosyphon solar heater system peak output in sunny conditions (locat. Montana, USA) ~ 25,000 Btu/hour, and the total daily heat gain about 130,000 Btu (38 kWh) !

details here:
http://www.builditsolar.com/Projects/Sp ... roject.htm
http://www.motherearthnews.com/Alternat ... eater.aspx

more of his and other projects:
http://www.builditsolar.com/

[steam_cannon]

$this->bbcode_second_pass_quote('Mesuge', 'T')here is a whole communty improving this "soda can room warmer concept":
http://blog.hemmings.com/index.php/2007 ... t-of-soda/

[Blacksmith]

OK, now you guys are starting to make some sense. Some of the concepts on this post are brilliant, my faith in mankind is restored.

[frankthetank]

I'd rather stick with copper tubing. Its expensive, but it has been tested for a long time and it works!

I also need this thing to be on the roof. Won't work on the ground here.

I pretty much want it to act like a preheater for the hot water heater. I figure its better if 80-100F is going in vs. 55F well water. Over the course of a couple years i could probably pay it back.

I have most of the materials i need. I have large pieces of glass that will be coming out of a picture window i'm going to remove. It will be a good way to recycle them. Also have 2x4's/plywood etc already. My problem will be getting the water up to the roof. That will require a good 50 ft total, which is $100 for a copper or i might use PEX (but i would need the crimping tool) because its 1/3 the price. It would be nice to build it over the winter.

[WisJim]

If you use copper tubing (which will contain a minimal amount of water, a gallon or so at most in the collector), you will have to circulate the water between the storage tank and the collector. Won't work well to use well pressure and use the collector stricly as a preheater. You would need substantially more volume to do that. Used solar water heating panels seem to be available sporadically at low prices, so I don't know if it would be worth it to build one.

Best current book: Solar Water Heating, by Bob Ramlow
http://www.arthaonline.com/bookpage.html

[frankthetank]

Never thought of the volume problem. So i would need a pump too, which thing would require some sort of closed system.

Maybe this isn't worth it in my case?

I figured we use 20 gallons of hot water a day (tops), so it isn't that expensive, its just all summer long i have a rooftop that is scorching hot, while i'm sitting here using electricity to heat my water.

[steam_cannon]

Solid Thermal Mass Water Heater

$this->bbcode_second_pass_quote('frankthetank', 'N')ever thought of the volume problem.

[steam_cannon]

Solar Hot Water System Types: Advantages & Disadvantages
http://www.azsolarcenter.com/technology/solarh20.html




And my addition
------------------------------------------------------------------------------------------
Thermal Mass Water Heater || Open Loop, Integrated || Simple, few materials || Experimental

[oowolf]

My solar water heater uses 11/2" black poly pipe. It's about 2x4 feet and holds 5 gallons. Has a glass storm window covering. Everything was scrounged except the elbows and tees used to connect the lengths of pipe (around $15). I carry water from the creek upstairs to the 2nd floor balcony which is above the bathroom roof and pour it in manually thru a big mechanic's funnel stuck in the top pipe. I have the exterior bulb of an indoor-outdoor thermometer dangling down into the piping to gauge temp. When heated I open a valve, draining water down into a salvaged 10 gallon water heater tank (I also can drain cold water from a 5 gallon bucket also connected to the infill line if the water's too hot.

I then close all valves and pump up the water pressure using a hand operated air pump connected to the water heater tank intake; this gives a good strong stream of water to help wash off dirt.

Requires only human power and sunshine.