Build a Solar Water Heater: An Intregal Passive Solar Water Heater

Passive solar water heaters are easy to build, install and use.


| January/February 1984



085-058-01-triple-tank

A horizontal, in-line, triple-tank integral passive solar water heater under construction.


David Bainbridge

For the do-it-yourselfer searching for an inexpensive, easy-to-build solar water-heating system, the integral passive solar water heater (IPSWH, pronounced ipswah ) is a dream come true. All you need to get going on this down-to-earth water warmer is a discarded electric water heater tank rescued from the local dump, a homemade plywood box to house it in, a can of flat black paint, a sheet or two of used window glass or clear plastic, a few common plumbing fittings and some pipe and insulation. Combine all that with some spare hours of satisfying sawing, hammering and wrench-turning, and you'll have an ongoing supply of hot water provided virtually free from that friendly furnace in the sky.

But before we get into the nitty-gritty of integral passive solar water heaters, let's run through a quick review of the basics of solar heating for those who may be new recruits to this wonderful world of free energy.

We'll be discussing solar collection systems for heating purposes — not for charging photoelectric cells or for other power applications — and there are only two basic types: active and passive. The essential difference between them is the use of external power: While active solar heating systems employ fans or heat pumps to circulate the Btu they gather, passive setups don't. As their name defines them, integral passive solar water heaters work on the latter principle, and that lack of power dependency and resultant energy savings is one of the IPSWH's greatest selling points.

Passive solar heaters can be subdivided into two classes: units in which the functions of heat collection and storage are separate, known as thermosiphon flat-plate systems, and arrangements that combine collection and storage into one integrated unit, namely, integral passive solar water heaters.

Since the flat-plate passive solar water heater is the predominant type in use today, most folks think of such collectors as being the best available for solar water heating. But in fact, for many uses, especially owner-built applications, IPSWH's outshine their flat-plate competition in almost every way — including ease and economy of installation, reliability and higher resistance to freezing.

How Solar Water Heaters Work

The design of all IPSWH's is based on a tank (or a series of tanks) painted flat black to absorb heat from the sun and then transfer the tapped Btu to the water stored within. IPSWH's are sometimes called batch heaters, because the heart of the system is the "batch" of water stored in the tank(s). To increase heat collection and reduce heat loss, a combination collection/storage tank is enclosed in an insulated box covered on the south-facing side and top with a glazing material, usually glass or molded plastic.

steve billingsly
4/2/2012 11:49:59 PM

http://www.sunbelt-solar.com/solarwaterheaterkits.htmlDIY Solar water heater


steve billingsly
4/2/2012 11:46:50 PM

How does the efficiency compare for passive vs. active solar water heating? http://www.sunbelt-solar.com/solarwaterheaterkits.html


b knight
6/23/2011 11:46:29 AM

A passive solar water heater is very simple and easy to build yourself. These do-it-yourself models won't run during winter months where temperatures go down to freezing, but for the cost (under $100) they are well worth the effort to put in place. Here's the batch solar heater I built for our outside shower: http://greenterrafirma.com/batch_solar_collector.html Here's a good overview of evacuated tube solar heaters with pictures of my brothers setup in his backyard. http://greenterrafirma.com/evacuated_tube_collector.html Enjoy..


radiantmanifold
2/4/2010 9:18:30 AM

Radiant Heat Manifolds are suitable to a wide range of heating applications, including radiant floor heating, baseboard heating and snow melting. I think tis is very useful information for all us! Useful sources http://www.builditsolar.com http://www.pexuniverse.com/store/category/radiant-heating-manifolds


green guy
8/4/2009 11:35:06 AM

A do it yourself solar water heater is very difficult to do right. Professionally manufactured and installed systems can be pricey, but in the long run, they’re less expensive than electric or gas water heaters. And you have the peace of mind of a long warranty. http://www.sunbelt-solar.com


green guy
8/4/2009 11:22:11 AM

A solar water heater is a great investment. The Return on investment is very favorable compared to solar electric PV panels. www.sunbelt-solar.com


green guy
8/4/2009 11:21:51 AM

A solar water heater is a great investment. The Return on investment is very favorable compared to solar electric PV panels. www.sunbelt-solar.com


theresa norman
9/2/2008 10:51:50 PM

oops. the rest of troy's comment got cut off. sorry for taking up so much of the post here. TROY: Here’s what I was thinking relating to shut-off valves. If you have pressure coming from the north side of the house (electric water heater) and pressure from the south (solar) into the bathroom fixtures, you’ll have conflicting pressure, which may change as the temperature of the water changes. Also, if you’d turn on the hot water in a room on the north side of the house, you may be getting water all the way from the solar collector depending on pressure. ME: pressure! i didn't think of that. i guess i'm thinking schematics, not dynamic system. so, troy, you seem to suggest that one factor in the pressure is water temperature. is that correct? i would presume that the solar water, being both hotter (since i would turn the electric one way down) and located above the showers, would be the one getting tapped. for the solar to be providing water to the north side would mean the hot water was going backwards through the pipes. as long as that isn't inherently bad, that's fine with me. dear readers, what are your thoughts or suggestions?


theresa norman
9/2/2008 10:47:08 PM

here's a conversation between troy and myself, following my question about direct connection instead of routing solar heated water to the existing electric heater. TROY: Thanks for your comment. Yes, it should be possible, but you’ll probably want to install shut-off valves so that you won’t have backflow concerns. But when you have the valves shut, you won’t have hot water from your electric water heater if you run out of solar heated water. So there are a lot of variables, including the climate where you live. ME: thanks for your fast and informative response. by "backflow" do you mean the house water going back into the collector rather than just out of it? i want to mount the solar heater on the roof; does that change the equation at all? i like the idea of shut-off valves, though i was thinking about a valve that would isolate the collector, that is, one that could close the loop from the house water into the collector at all, temporarily returning the system to its original configuration. hmm, i suppose i'd need another on the hot water pipe coming out of the collector, too. i don't know that without one, air wouldn't get sucked into the house lines, or the solar heater wouldn't get too hot and do something creepy. you seem to suggest a shut-off valve that would turn off all hot water in the house, yes? our climate is pretty warm with temps running from lows of mid to low 50s on dreary winter days (of which we have three all year) to highs in the low 100s on the worst summer days. average temps are 65-73 winter, 85-95 summer. (in 2005 we had the first snow here in 125 years.) so i'm not concerned about freezing, but my solar water heater may not do a great job in february. cold temperature seems like the only reason i would have (other than occasional maintenance or repair) to shut off the solar heated water. is there something i'm missing? TROY: Here’s what I was thinking relating to shut-


theresa norman
9/2/2008 2:52:23 AM

i would like to install a solar water heater because my current electric one is on the north side of the house, near the kitchen and laundry, but the bathrooms are on the south side of the house. as a result, if someone wants a hot shower, they have to run a LOT of water before the hot water gets there. (i have given up washing my face in hot water at night in the winter.) everything i've read so far talks about routing the solar heated water into the conventional tank. this would make my hot water cheaper, but it would still waste the same amount of water. i would like to install the solar heater on the south side of the house, near the bathrooms, and have it connect directly to the hot water pipes, thereby by-passing the electric tank entirely. is this possible?


theresa norman
9/2/2008 2:39:35 AM

i would like to install a solar water heater because my current electric one is on the north side of the house, near the kitchen and laundry, but the bathrooms are on the south side of the house. as a result, if someone wants a hot shower, they have to run a LOT of water before the hot water gets there. (i have given up washing my face in hot water at night in the winter.) everything i've read so far talks about routing the solar heated water into the conventional tank. this would make my hot water cheaper, but it would still waste the same amount of water. i would like to install the solar heater on the south side of the house, near the bathrooms, and have it connect directly to the hot water pipes, thereby by-passing the electric tank entirely. is this possible?


dw loyd
7/25/2008 11:29:16 AM

Most estimates of hot water needs I see when reading about solar heaters are 20 gallons per person per day. That is an outrageous amount of hot water use even if you are home all day every day. Currently, our total water use is somewhere between 400 and 600 gallons per month for two people. We rainwater collect from a 1200 sq ft roof. Our area gets less than 20" of rain a year. Currently we are at over 80% capacity (4000 gallons or so) and the monsoon season is far from over. 20 gallons a day is, unless I can no longer count, 600 gallons a month per person just for hot water. We are at about 250 gallons per person total water use.


tom_47
1/9/2008 1:15:56 PM

Yes, Gas heater cores work fine. You can mount them easily (horizontally by putting a pipe through the flue in the middle and securing the two ends of the pipe to supports. then no part of the tank touches anything that would conduct the heat away.


kjohnson10
9/28/2007 8:15:32 PM

I notice the article mentions using electric water heater cores. I have two old gas heaters. Can those cores be used?


tara_4
8/7/2007 10:30:00 AM

I plan to add the passive solar hot water tank to my home as seen in your article. Due to the buildings position, space & sun. I am thinking about housing my tank in a vertical position. I notice that most of your examples are lying on their sides what is the reason for this? Is it a mistake to place my tank in a vertical position? Tara Cox


andy_9
7/29/2007 12:27:29 PM

Hello I am very interested in your article. But, I'm wondering if it's possible for me to have a similar construction during my extreme winter (Lapland) weather conditions within the Arctic Circle where temperatures are as much as -30 during the coldest part of winter. As a novice I understand the basic principles of your system but how would it function in cloudier or even days with small light. Currently, I am looking at more cost effective ways to heat my cellar which I intend using during the winter, without splashing out too much money on heating bills. Electricity is fairly expensive here and I need to create something like you have to cut the costs. Any info or help would be much appreciated. Thanks Andy


p.rajarajan
7/10/2007 1:11:45 AM

i need details about how solar heat becomes elecrtric energy ?


jamie_6
7/4/2007 2:47:08 PM

My Mom and Dad bought our family home in 1963. The house had been built in 1923 and had a VERY old gas hot water tank that my Dad replaced. He replaced a 40 gallon model with a 50 gallon model because of our family size of 2 adults and 5 kids! That hot water tank lasted at least 35 years for that was when we sold our family home after my parents passed. The plumbing was such that there was a 50 gallon storage tank BEFORE the cold water entered the standard gas fired hot water tank. My Dad said it was free heat, the storage tank raised the water temp to room temperature (70 deg. located close to the furnace!) He also thought that the conventional hot water heater lasted EXTRA long because it was never shocked by cold water entering the tank.


les_5
4/15/2007 2:23:00 PM

I thinking of making a solar hot water tube for my swimming pool 15' Dia, A series of pipes going back and forth, water coming out of the filter through the pipe work into the pool, the pipes and backing being black with glass covering. could you tell me if i'm on the right lines. Thanks Les cook


thom_3
3/6/2007 8:21:42 AM

Lately I haven't been able to read the best magazine in the world we live in but alas life is what you make it and I have gone in the complete opposite of of live within ones means I will be getting back there next year I hope. For a while I couldn't find you anywhere I live on an Island in the northeast but travel every week around the country of north and south america you would be surprized but your magazine is only getting to about 20% of the pop. maybe circulation should.






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