Solar Pool (and Hot Tub) Heating

Solar pool heating systems will save you lots of money, and reduce reduce greenhouse gas emissions.

 

Pool heating is a very good solar application.  The systems are simple and relatively inexpensive.  Pool systems usually use simple, low cost, unglazed plastic collectors.  The pool itself is the thermal storage for the system, and the pump you already use for filtering pool water will also circulate water through the solar collectors.  All of this leads to inexpensive systems -- some of the simplest solar pool heating systems cost as little as $100.

 

Some states offer tax incentives for solar pool heaters.

 

Directory for this page:

Two NEW  ideas for homemade pool collectors

 

PV pool pumping ...


Questions? 
Report Broken Links ...

Pool Cover -- A must

Pool Cover -- a must

Energy.gov on pool covers...

 

 

One of many, many suppliers of pool covers:
http://www.solarcovers.com

Using a good pool cover is the most effective thing you can do to save pool heating costs and reduce greenhouse gas emissions. 

"Pool covers cost between $85 and $150 for most residential pools. In fact, all of the other pool heating methods discussed in this article should only he used in conjunction with a pool cover. Not to do so would be like running your house air conditioner during August with the doors and windows open. The system will still work, but the operating cost will be as much as three times" higher."  David Boehmer.

Pool covers work by reducing evaporation, which accounts for about 70% of pool heating cost. Clear covers have the advantage that they not only reduce evaporation, but also allow solar gain through the cover.

Fuel Cost Savings for Using a Pool Cover

 

Energy.gov on pool covers...

 

 

This Energy.gov page provides estimates of pool heating costs with and without a pool cover for a number of US locations. 

For example: Denver without cover $2120, with cover $168.
These are for a 1000sf pool at 80F, and 50 cent per therm natural gas burned in an 80% efficient gas heater.  In the above example, the no cover case would result in about 6 tons more of CO2 emissions per year.

Solar Rings

Do a Google search on "Solar Rings pool"

These are a potential substitute for a full pool cover.  The are rings that are several feet in diameter.  You buy enough of them to cover about 80% of the water area.
I have been a bit skeptical of how well these would perform, but have a report form one person that is quite happy with them, so they may be a candidate if you don't want to mess with a full pool cover.  Not as good as a full cover, but much better than nothing?   (thanks to Amy for suggesting these)
Solar Pool Heating Basics
Solar Pool Heating Basics, Two part article
Tom Lane
 


How to get articles from Home Power ...

"Three gallons of oil refined and burned provides 400,000BTU ... Once.   Three gallons of oil, made into a 4 by 12 foot solar collector, can provide over 10 million BTUs per year ... year after year"

Home Power magazine articles, issues 94 and 95.

VERY good hands on how to size and install a pool heating system.

FESC Solar Pool Heating,
 

Florida Solar Energy Center
http://www.fsec.ucf.edu

 

The FSEC is a very good source of pool heating information.

They cover collector sizing, economics, system installation, and provides collector and system ratings based on FSEC testing.

While aimed at Florida residents, the information is widely applicable.
Conserving Energy and Heating Your Swimming Pool with Solar Energy,
National Renewable Energy Laboratory (NREL)

Download here... (pdf)

 

This NREL document gives some good strategies for reducing the energy required to run and heat a pool.
The material on sizing the pool pump and how much circulation time is required is very good, and could save you up to 75% in  pumping energy.
Residential Solar Pool Heating System

Natural Resources Canada

Buyer Guide (1.8MB pdf)

 

 

A good guide on solar pool heating systems from Resources Canada.  Describes types of systems, sizing system, and some installation detail. 

Shows that solar pool heaters can show VERY good payback even in the "frozen north". 

FlaSolar.com

http://www.flasolar.com

 

A very simple calculator for estimating solar panel collector area required to heat a pool from the FlaSolar website.

Solar Site Survey...

 

If you are going to do a solar project, you need to do a Solar Site Survey to make sure that your site gets enough sun during the right times of year to make the project work.
This free and simple survey only takes an hour and is fun and educational.

 
Installation Manuals and Specifications
See also the first article above from Home Power Magazine on pool heating basics.
 
 
SunTrek Solar Pool Heating Installation Guide...   (pdf)


The Suntrek site has other helpful material and supports DIY installations...
installing solar pool heating collectorsThis is a very detailed and practical 48 page manual on installing solar pool heating collectors.  Covers attaching the collectors for various types of roofs, collector plumbing connections, ...

Just a wealth of good practical install info.  Many roof styles covered, and good coverage of ground mounting racks as well.

SunTrek's collectors are basically matts of EPDM tubing that connect to 28 inch wide manifolds.  Its a very flexible system that allows collectors of just about any width and length to be built...
Solar Pool Heating System Installation
Florida Solar Energy Center

http://www.fsec.ucf.edu

 

 

Good tutorial from the FSEC on installing a solar pool heater.  Quite a bit of how-to detail.

Colder climates may require some changes for freeze protection if not drained.

RimStar Solar Pool Heating

http://rimstar.org/renewnrg/solarpool.htm

 

Nice rundown on installing a solar pool heating system for a cold climate.
Hot Sun Industries

http://www.h2otsun.com/

The installation manuals give quite of detail on installing pool heating systems.

Pretty good write up on what is involved in installing a solar pool heater with some hands-on information.  Quite a bit of information on installation and sizing.  One of many manufacturers.
SolarHOT

Detailed instructions on installing pool heating collectors...

 

SolarHOT provides a detailed installation manual for their line of pool heating systems. 

The instructions have a lot of generally useful information that might be helpful in your installation.

Other helpful info on their site including manuals, piping diagrams,...

Above Ground Pool Heating

http://www.smartpool.com/website/solar.html

Installation Manuals

Another supplier:
http://www.solardirect.com

(Note: I don't know anything about either of these suppliers -- its just a place to start looking)

One example of a simple above ground pool heating package.  Comes in a 21 lb UPS-able package!

About $110 for one panel and $170 for two (the picture shows two panels).
 


 


Costco currently has a 40 sqft pool collector of this type for $99.99   -- what do you think the payback period for this collectorl is ...
Go Solar

http://www.solarexpert.com/poolheat.html

 

 

Supplier of pool heating systems.  Web site has some useful technical information and a fuel saving calculator.
Homemade Pool Heaters
 
Tom's PEX/Aluminum solar pool heating collector

Full details on construction...

 

NEW More about the pool heater on Tom's new website...

This is a nice, simple, cheap pool heating collector you can build that uses PEX tubing for the manifolds and risers, and aluminum heat collection fins.  

It should be a very efficient collector.

Full construction details...

 

Be sure to protect all PEX from sun exposure -- this is particularly important when Chlorine is present in the water.  Note that Tom's collector leaves no PEX exposed to direct sunlight. 

A Large Ground Mount Solar Pool Heating System

www.mindchallenger.com/solarpool/
This is a fairly detailed description of a 340 sqft solar pool heating system that uses the rubber mat style commercial pool heating collectors.

The author measured the collector output at over 100,000 BTU per hour -- equivalent to more than 1 therm of natural gas per hour, or 30 KWH per hour!

Lots of detail on building the ground mount system.
A Pool Heating Collector from PVC Pipe


Full details on PVC pool heating collector...
pvc pool heating collectorMatt provides a detailed description of how to design, size and build this pool heating collector from regular PVC pipe.

It uses readily available materials and is easy to construct.  It can be sized to the exact space you have available.

Full details on PVC pool heating collector...
Matt's inexpensive, simple, PV power pool heating collector

Full details on construction...

 

Matt's pool heater in the Burlington Free Press...

This is Matt's very inexpensive, efficient, pool heating collector.  This collector can be built for about one third the cost of commercial collectors and has comparable  efficiency.
Matt used a PV powered pump, so the pool pump does not need to be run, and no external power is used for pool heating.

For more on why this simple design works well, see the entry just below.

Simple Pool Heating Idea

 

Gary

This is an idea for a simple, cheap and efficient homemade pool heating collector.  Some experimental results are presented...

See the entry just above for an actual very nicely done  real implementation of this idea.

 

Solar Pool Heater in Tuscany

http://rimstar.org/renewnrg/solar_pool_heater_diy_fp.htm

 

This is a very nicely designed pipe coil style pool heating collector in Tuscany. 
Good detailed description.  Very flexible plumbing arrangement.

Good performance numbers (see note below for more on performance)

Thanks to Steve for sending this in!

A nice pipe coil solar pool heater for a 9000 gallon in-ground pool

 

www.mildevco.net/solar_pool_heater.htm
solar pool heaterThis is a pipe coil heater that does a very nice job of blending the coils into the landscaping around the pool. 

The system is fairly simple to build and the total cost was only about $200, which should give a very fast payback.
A very large pipe coil solar pool heater

http://pasarlascanutas.com/...

 

 

This is the Mother of All pipe coil solar pool heaters.  It uses 4000 ft of black poly irrigation pipe. 
Very nicely done, lots of good detailed pictures, and some performance data.
Its in Spanish, but the Google "translate" button is your friend.
Solar Thermal + Cheap = Inexpensive Pool Heater!

whereisholden.blogspot.com/...


Here is an updated post with more details and questions answered...
solar pipe coil pool heaterThis is a good description of a solar pool heating collector made from several spiral coils of black irrigation tubing. 

Total cost $300 -- compared to commercial system bids of $5000!
Very Simple Pool Heater from SugarMtnFarm

 

http://sugarmtnfarm.com ...

 

A nice simple pool heating scheme for small pools from SugarMtnFarm.  Also, some ideas on saving pump energy, and keeping your pool clean without Chlorine.

I was a bit surprised that such a small collector (only about 10 sqft) was able to do worthwhile heating, but the secret is keeping the pool volume fairly small.  Walter's pool has about 14,000 lbs of water to heat, where a 20 ft diameter by 4 ft deep pool has almost 80,000 lbs of water to heat -- a good reason to use a small pool!
(Thanks very much to Walter for sending this in!)

My Homemade Solar Pool Heater

Andy

http://www.thecasualtraveler.com/solar.htm

 

 

A nicely done DIY solar pool heater made from 100 ft coils of half inch plastic pipe.
Performance data coming later in the Spring.

Details ...

Andy has some other renewable energy projects in mind, so keep an eye on his website.
Video on a Pipe Coil Pool Heater

http://www.truveo.com/...

 

 

 

Video on a simple, homemade pool heater that uses a large pipe coil on the roof of an adjoining building.
 
Homemade pipe coil solar pool heater

http://rimstar.org/renewnrg/splyucca.htm

 

A pipe coil style pool heating collector made from 10 mm black irrigation pipe.

The collector is piped off the main circulation pump and receives a small fraction of the total pump flow.

The 12 kw output is a bit hard to swallow given the size of the collector, but the collector appears to work well and cost little -- hard to beat that.

Gull Industries Pipe Coil Pool Heater

www.gullsolar.com ...

 

A commercial version of a pipe coil pool heater.

Some good pictures of this type of collector ...

Paint South Side of Pool A Dark Color

Details...

black pool water heaterThis is a REALLY SIMPLE idea from Deane to heat an above ground pool in the early and late season.

Details...
Thoughts on Efficiency of the Various Styles of Collectors Shown Above
In spite of the fact that most of the entries in this section are for pipe coil style heaters, I have slightly mixed feeling about how well these will work out for most people.  All things being equal, a square foot of commercial mat style pool collector is going to be about equivalent to a square foot of a pipe coil collector.  The message here is that its going to take a lot of pipe to to heat a pool.  A 300 ft coil of 1 inch pipe has a solar collector area of 25 sqft, so its going to take a lot of pipe to get up to half your pools surface are.

The Tuscany pipe coil pool heater (see above) provides performance numbers, and appears to verify that a given area of pipe coil will have the same performance as the same area of rubber mat style collector -- both about 80% on a warm summer day.

I think that all of the DIY collectors shown above will have about the same heat output per sqft as the commercial mat style collectors, so, I think its mostly a mater or comparing costs and what fits for your location.
PV Powered Pool Pumps

A DIY solar powered pool pump installation

All the details on design, build, and economics...

 

PV Powered Pool PumpBruce cut his total home electricity usage by 25% using this PV powered pump for his pool.

The system uses two 170 watt PV panels to power a Speck Swimming Pool and Spa pump through a Lorentz controller.

All the details on design, build, and economics...

Field Studies of Two-Speed and PV-Powered Pumps and Advanced Controls for Swimming Pools,
Springer, Rohe approximately 1990

 

An interesting paper that looks at the savings for 3 approaches: 1) using a 2 speed AC pump running longer on low speed, 2) a PV powered DC pump, and 3) controlling pump operating time with a turbidity meter.

Note that since the paper dates back to 1990, the costs of the PV system have dropped significantly and need to be updated for comparisons.

The use of a turbidity meter to regulate pump on time seems promising, but I've not seen any further developments on this.

Pool pump powered by grid-tied PV system

As an alternative to a dedicated PV system for the pool pump (as above) one could add a grid-tie system that provides power for the home (including pool). This has the advantage of using the same system for both home power and for the pool pump. The downside of the grid-tie system powering a conventional AC motor is that it is much less efficient than a system that drives a DC pump from dedicated PV panels via a controller.

It would be nice to get a precise comparison, but as a rough guide, the montly cost of running a conventional AC 1.5hp hp pool pump for 8 hours a day is about 400 KWH per month. A grid-tie PV system to generate an average of 400 KWH a month would require an about 3000 watt PV array. Contrast that to Bruce's (and others) use of about 400 watts of dedicated PV to direclty drive an efficient DC pump.

Something Else to Try?
Taking the Plunge Naturally,
Permaculture Magazine

Building a Natural Pool (pdf)

Mother Earth News Article: How to Build a Natural Swimming Pool, Buege
Finding Mother Earth News articles...

Description of an article from Permaculture Magazine:
www.permaculture-magazine.co.uk/...

These beautiful swimming pools clean themselves naturally (no chemicals). 

Less impact, less energy, nicer looking, less expensive to build and maintain.


(Thanks to Paul for finding this)

Natural Swimming Pools -- Conventional Pool Conversions, Michael Littlewood, 2011 Natural Swimming PoolsThis is a good book describing how natural swimming pools work.  The emphasis in this book is on converting an existing pool into a natural pool, but I think it also works fine as a "how-to" on designing and building a good natural swimming pool. 

There is enough material on design and building in this book to be a good start on designing and building (or concerting) your own pool.

The book is a UK book and most of the examples are from the UK, so if your climate is markedly different from the UK, you may have to seek additional information.
Embedded Pool Deck Collector

www.pacificgunite.com/solar%20pool%20heating.htm

 

 

 

This seems like a potentially good idea for integrating a collector with the pool deck, or other nearby dark surface.

Tubes embedded in the dark colored deck concrete pick up heat from the solar warmed deck to heat the pool.

The Rutgers Solar Heating System for Greenhouses
Mears, Roberts, Simpkins, and Kendall
Rutgers University

The Rutgers Solar Heating System for Greenhouse - 1977 (0.8 MB pdf)

Greenhouse Solar Heating-1981 (2.5MB pdf)


 

 


A related paper on a solar home using a similar flooded subfloor heat storage scheme.

The solar collector shown here was developed in the 70's as a very inexpensive greenhouse heater.  It works well for situations in which only low temperatures are required (like greenhouses and pools).

While I do not know of anyone who has tried this as a pool heater, it seems to me it might work well, and it would be very inexpensive -- perhaps $2 per square foot?

The papers give information on a several greenhouse energy schemes, so you have to wade through all this to find the details on building the collector.  The collectors described in the paper are quite large, but could be scaled down.  Note that even though this is a very simple collector, there are details that you must get right for it to hold together -- so read all the construction notes.

If you build one of these PLEASE let me know -- Gary

A number of other interesting commercial greenhouse related papers at the Rutgers Horticultural Engineering Website: http://aesop.rutgers.edu/~horteng/

Old Swimming Pool Converted to a Greenhouse to Grow Produce and Fish

http://gardenpool.org/
pool to greenhouseThis family converted an unused swimming pool into a greenhouse that grows produce tilapia fish, and chickens for eggs.
Pretty ingenious.
Their motivation for doing this is to be self sufficient in case of a major disaster, but it could certainly work for people not expecting a major disaster.
The family was featured in a National Geographic special on major disaster preparation --the video shows more details on the system they set up...
Hot Tubs
Hot Tub Energy Use
Hot tubs use a staggering amount of energy.  The Davis Group says that annual energy use for a hot tub in a mild climate is around 2500 KWH per year, and that for people who own hot tubs, the tub will likely be their largest energy use.  To put this in perspective, 2500KWH is equivalent to running 5 refrigerators, and will result in about 4000 lbs of carbon emissions per year.  Energy use in cold climates is even greater.

So, 1) really evaluate whether a hot tub is worth all this energy, cost, and carbon before you buy, 2) look for the most efficient one you can find -- paying extra for a well insulated and energy efficient tub will save you money and reduce carbon emissions, 3) have a very good cover and use it, 4) use one of the solar or wood heating schemes listed below.

Energy use of hot tubs...                  More on energy use...

Solar Collector Size to Heat a Hot Tub... solar collector size for heating hot tubThis simple method will give you a pretty good estimate of how large a solar collector you will need to heat your hot tub.

The method is based on the size of your hot tub and how much your hot tub temperature drops over a 24 hour period.  Using the temperature drop takes into account how well you tub is insulated, how you use it, your climate, and all sorts of things that would otherwise be hard to account for.
My Solar Heated Hot Tub
 

Bob Owens

How to get articles from Home Power ...

Home Power Magazine article in issue 104.  Good hands on description of building a drain-down style solar water heater to heat a hot tub.
Glazed PEX Collector for Hot Tubs -- experiences

 

Tom reports on a couple schemes to heat his hot tub with a glazed PEX collector, and with a copper collector.  Here are the results...

The results of Tom's testing make me wonder how good a solution the Home Power article above is.

Woodstoves for Tub Heating (or for heating thermal storage tank?)

Chofu: supplier (one of many):
http://www.thesolar.biz/Chofu.htm

Mother Earth News article: Wood-Fired Hot Tub, Stocking
Finding Mother Earth News articles...

pdf describing the Chofu
www.revolutionearth.com/download/ChofuDataSheet.pdf

Snorkel and Scuba Underwater Woodstoves:
http://snorkel.com

Cowboy Hot Tubs:
http://www.cowboyhottubs.com/

Alumi-Tubs Inc.
www.alumitubs.com/ 

Chofu: This is a simple, wood fired heater for soaking tubs. 
It uses a simple thermosyphon system to circulate heated water (no pumps, no electricity).  The full stainless steel case is a water jacket for efficient heat transfer.


Snorkel & Scuba: These wood stoves for heating tubs actually live in the tub water, so heat transfer is directly from the stove walls to the water.



It seems like this might be a simple, and greenhouse gas friendly  way to add heat to a solar heat storage tank when there is not enough sun?

How to build a wood fired hot tub,
from Instructables

 

http://www.instructables.com/ ...

 

Pretty funky wood fired hot tub heater.  The tub is made from a big plastic tote tub, and the heater from an old propane bottle.
Brian's $350 Solar Heated Hot Tub

Details...

 

 

This is a nice simple design for a solar heated hot tub that uses a Rubbermaid plastic stock tank, and a solar collector made from CPVC pipe.

Details...

Build Your Own Solar Hot Tub,
Robert Herman

www.hotspringsenthusiast.com/SolarTub.asp

 

A fairly detailed article on building your own solar heated hot tube.
The author used a stock tank and a used solar collector to keep the total cost down to $100. 
The collector is hooked up as a simple thermosyphon, so that no controls or pumps are needed.
A Low Tech Hot Tub & Solar Heater

http://eco-ants.co.nz/projects.html

 

 

 

Here is a low tech hot tub and a simple, but effective solar and wood burning hot tub heater.

 

(I think there is some risk here of getting the plastic pipe to hot if the collector stagnates -- see notes on our PEX collector and stagnation)

Large Drainback System for Home and Hot Tub

www.solarbair.com/articles/horsecreekarticle.html

Eric's site home page:
www.solarbair.com

This is a very nicely designed and built system by Eric.  The system includes 320 sqft of drainback collector supplying heat for both Eric's home and hot tub.  The storage for the system is a precast underground tank that is quite cost effective.  A conventional boiler is integrated into the system for back up heating.  A very nice system explained well.
Tom's 330 sqft Solar Space Heating System

This is another larger solar heating system that includes Hot Tub heating.

Full design and construction details...

More on Tom's site about solar hot tub heating...

Tom's other projects fine on BuildItSolar...

Tom's very well done  solar system for heating the house and domestic water heating.  This is a great project with details on design and construction of a large solar collector array, a large thermal storage tank that doubles as a work bench, integrating solar and wood boiler heat sources in the same system, a very nice heat exchanger fabricated from rigid copper pipe, and details on integrating radiant heating with solar. 

This is Tom's 3rd generation of building solar water heating collectors, and he has incorporated refinements in each generation -- the collectors are  efficient and well proven..
Some Additional Thoughts on  Tub Heating

Given the very large energy consumption of hot tubs, maybe its worth considering some of these:

- Enclose the hot tub in a sun space, which would raise the ambient temperature the hot tub sees and reduce heat loss.

- Build a well insulated enclosure for the hot tub that includes insulation around all 6 sides.   The enclosure could be hot tub height, and opened only when the tub is in use.

- Use a scheme like the one described in this fish tank heating article ...

- PV powered pump for the basic circulation pump?

Any other ideas?  email me...