Sizing the Pump and Plumbing for a Solar Water or Space Heating System

I go through a fairly simple procedure that will allow you to pick the right size pump and the right diameter plumbing for your solar water or space heating system.

I use my Solar Shed space heating system as an example, and go through sizing it in detail. 

The Solar Shed is a fairly large 240 sqft of collectors system, but the procedure can be used for any size system.

The procedure covers:

1. Estimating the flow rate that a set of collectors will need
2. Estimating the pressure drop in the pipes due to pipe friction
3. Using pump curves to pick the right size pump for the system

 All the details on picking pump n' pipes for solar heating ...

Gary

NEW STUFF: Solar pump, Portable solar jar cooker, Mist cooler, Strawbale home site

New Taco Pump for Solar Hot Water Systems Integrates Controller

This new series of pumps from Taco combines one of their regular circulator pumps with an integrated differential controller.  This makes for a bit less wiring and a more compact system.  The pump is also variable speed, and the controller takes advantage of this to use lower flow rates at low sun levels -- this (presumably) saves some pump power and allows the collector to operate in lower sun levels where short cycling would result with non variable flow controllers.

I've also separated out tanks, pumps, and heat exchangers on their own page and expanded the number of items and explanations.
(thanks to Jan and Sean for pointing this item out)

Details on the new solar pump with integrated controller...

Compact, Simple Portable Solar Cooker

This is a neat little solar cooker sent in by Tony.  Just the thing for a hot beverage or a hot dog at the job site, camping, ...

Its made from cardboard with aluminum foil glued to it and a couple of jars that nest inside each other with the inner absorber jar painted black.

Details on the Solar Jar Cooker...


Mist Cooler Kit

This is an inexpensive mist cooling kit from DripWorks.com.

If you've not experienced outdoor mist coolers on a hot day, you might be surprised by how effective they are -- they cool well without feeling wet.

Each mister head uses about 0.75 gallons per hour, so there some water use.
The kit costs $25 and is said to cool 25 lineal feet of space.
I've ordered one to evaluate it.

Details on the Mist Cooler Kit...


Strawbale Home Site

This is a nice site for potential owner builders of strawbale homes.

Workshops, videos, articles, ...  looks like good stuff from people who really build strawbale homes.


Strawbale home site details...


Gary

320 Watt Truck Mounted Solar PV System

Here is a good and detailed description of the construction of a mobile solar electric (PV) system mounted in a pickup truck.  The system can be used for providing power for remote locations, homesteads, jobsites, camping, emergencies, cabins, ....

 MightyBooBoo describes the system in detail.  He was able to buy many of the components through Craig's List, and the full system cost him less than $1000 -- about $3 per watt!
 
The system components are:

•  Four 80 watt monocrystalline PV panels for 320 watts total of PV power.
•  Four 12 volt, 95 amp-hour AGM Batteries (3+ KWH of storage)
• Two 10 amp charge controller and fuse blocks.

An inverter will be added to the system when 120 VAC  "house" power is needed.

The picture shows the four 80 watt PV panels mounted on the existing truck rack. 
Some new angle iron was added to the rack to support the edges of the panels.

The truck has been driven some 2K miles over rough roads and at speeds up to 70 mph with the panels mounted as shown -- no problems.

The picture shows one of the two MorningStar charge controllers and the fuse block.  The system is set up as two independent systems -- each has two 80 watt PV panels, one charge controller, and two 12 volt batteries.

Full details on how to construct this mobile PV system here...

Lots more on building PV systems of all sizes and shapes here...

Thanks to Boo for sending this in!

Gary

Knick's "$1K" Solar Water Heating System

Knick has sent in a detailed description of his very nice, solar water heating system project.

The system loosly follows the $1K design, but includes a number of unique features as well as some very nice workmanship:

•  A very aesthetically pleasing collector -- the nicest I have seen.
• Large area, double glazed collectors oriented vertically should provide good performance through the winter without summer overheating.
•  Some unique wrinkles in the collector internal design.

Detailed construction with lots of construction pictures are provided...

The Collector
The collector is three bays of the copper grid with aluminum fins that has been used in many of the $1K collectors.  Knick used twinwall polycarbonate for the glazing, which improves winter performance and has a very nice look.

Collector Installation
Knick mounted the large collector vertically on the wall.  This philosophy of using a somewhat oversized and vertically mounted collector gives good performance in the winter (when the sun is low) but does not tend to overheat in the summer when the sun is high. The result is a higher year round solar water heating fraction.

The wood frame collector is trimmed with aluminum, which gives good weather protection and also looks very nice.

Heat Storage Tank
The non-pressurized 300 gallon heat storage tank is built using the "tried and true" plywood box over a 2 by lumber frame with an EPDM rubber sheet liner.  The tank is insulated with rigid foam board insulation between the liner and the plywood box.  This design has a 30+ year track record of being durable and trouble free.  Knick used the large coil of PEX heat exchanger design.

Great job --thanks to Knick for sending it in!

All the details Knick's system here....

Details on the $1K Solar Water Heating System ...

More examples of the $1K Solar Water Heating System...

More on DIY Solar Water Heating Systems of all types...

Gary

NEW: Two solar pool heaters, $1K Solar DHW After a Year, Hybrid Bus

The Mother of All Pipe Coil Solar Swimming Pool Heaters

 This is the Mother of All pipe coil solar pool heaters.  It uses 4000 ft of black poly irrigation pipe. 
A very nicely done project with lots of good detailed pictures, and some performance data.

Details here...





More Information on Tom's Large Pool Heating Collectors
Some additional data on Tom's well designed DIY solar pool heating collector project.
Tom's collectors uses PEX tubing with aluminum fins and (like most pool heating collectors) are unglazed.
Construction details here on BuildItSolar...


More information on Tom's new website....

Update on Woodsy's $1K Solar Water Heating System

Woodsy's $1K Solar Water Heating System is a year old, and he provides and update on the system that includes estimated energy and dollar saving. The first year of operation has been trouble free.

The performance report for 1 year of operation...





Fisher Coach GTB-40 Hybrid Bus

The GTB40 buses from Fisher Coach are about twice as fuel efficient as conventional buses.  There is an all electric version powered by batteries, and a range extended version that uses a CNG powered generator to charge batteries.  The buses are about 1/3 rd lighter than conventional buses due to a stainless steel unibody design.
Details...


Gary

Low Tech (but very efficient) AC

I guess its time to start thinking about cooling again.

It occurred to me that  a low tech, but very efficient air conditioner might be put together by combining two items from the Experimental page. Warning -- these are simple test setups just to look at feasibility and performance -- if you are looking for pretty, you won't find it here.

The first is the Evapro-Radiative cooler.  This is a very simple gadget that runs water from a coolth storage tank over a metal surface at night.  The metal surface faces the night sky, and the water is cooled by a combination of radiation to the sky and evaporation.  As the little test shows, it is an  effective cooler, and the only power consumption is for the small circulation pump (which could be PV powered using a battery).

Even with the not very efficient pump I used, the COP was over 12 (SEER 40+).

The 2nd item is Nathan's car radiator coolth distribution system.  The radiators turn out ot be very effective water to air heat exchangers -- and, cheap to boot.

So, the evapro-radiative cooler would cool an insulated water tank at night, and a small pump would be used to circulate the cooled water to the radiators inside the house during the day.
The combination of the efficient cooling provided by the evapro-radiative approach and the efficient distribution of coolth by the radiators should make for a very high COP system.  With a little bit of PV, it could have a COP of infinity.  It should also be a good system for off-grid homes.

The system does not remove humidity, which would be a problem in some climates.  I guess its possible that some water would condense on the radiator coils and could be collected and drained for a bit of humidity removal.

I was tempted to call this RedNeck AC, but Nathan is now a PhD (congratulations!) and might be offended :)

Gary

Got any DIY Pool Heating Ideas? Projects?

During the summer, the Solar Pool Heating page is often the most popular on the site getting about a thousand visitors a day.   So, there is a lot of interest in solar pool heating.  This is good as its probably the most cost effective solar application out there.  

People have worked out several Do-It-Yourself approaches to solar pool heating, and I've tried to provide detailed how-to's for each of them on the Pool Heating page. 

There is so much interest in this area, and it is such a good energy and CO2 saver, that I would like to expand the pool heating page to cover every credible scheme.

If you've done a pool (or hot tub) heating project or know of a link to a project, or have a idea on solar pool heating then please send it in -- there will be lots of people interested in seeing it!

You can leave a comment on this blog entry, or email me  

One thing in particular that is lacking on the page are some good examples of what's involved in buying commercial pool heating collectors and installing them yourself on your pool -- I'd love to add some good, detailed examples.

If you are looking for energy efficient ways to heat your pool, there are a lot of them on the Solar Pool Heating page. 

My favorite quote on solar pool heating from Tom Lane:

"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."


And, thanks again to all the people who have already sent in their pool heating project details!

Gary

DIY Thermosyphon Solar Water Heating System

This is a very nicely done thermosyphon solar water heating system. 

Thermosyphon systems use the lower density of the water heated by the collector to drive water circulation around the collector and tank circuit.  The systems are simpler than most solar water heating systems in that the need for both a circulation pump and a controller are replaced by the thermosyphon natural circulation.

As the schematic above shows, the only conponents of the system are the collector, the storage tank, and the connecting plumbing -- sun and gravity takes care of the rest.  The system is simpler, less costly, and lower maintenance than most solar water heating systems. 

Lonnie did a very nice job on this  system, and provides full construction detail.  While the collector construction follows the general design of the $1K collectors, Lonnie includes some new wrinkles in the collector that should improve performance.

While thermosyphon systems are very straight forward and simple, there are some things that must be kept in mind:

• The tank must be above the top of the collector.  This allows the hotter water in the collector to rise upward into the tank.  It also automatically shuts off the circulation when the water in the collector cools below the tank temperature.
• The plumbing between the collector and tank must slope upward toward the tank.  And, since the thermosyphon forces driving the flow are relatively weak, the collector and connecting plumbing should have low flow resistance.
• This thermosyphon design does not include freeze protection, so is only for situations in which no freezing weather occurs, or the collector can be drained for the winter.  There are thermosyphon designs that circulate antifreeze through the collector and use a heat exchanger to transfer the collector heat to the storage tank.

If you can meet the above criteria, the thermosyphon systems are a good choice for simple, cost effective, and maintenance free solar water heating.

Full details on Lonnie's Thermosyphon Solar Water Heater...

Details on other DIY solar water heating systems...

Gary

Finding an Efficient TV (and problems with Energy Star)

We purchased a new TV a few weeks ago, and I thought I would pass on some of what we learned along the route to trying to find an energy efficient TV that was also a step up in picture size and quality. The TV we replaced is a 10 year old Toshiba 34 inch CRT style TV.  While the TV was showing some signs of age, it was still serviceable, and we did find a good home for it over the FreeCycle Program.  After quite a bit of thought and looking, we replaced it with a 46 inch Sharp LC-46LE700UN.  The material below says how we got there and gives some (hopefully) helpful resources if you are searching for a new TV.

Bottom Line messages from this quest for an efficient new TV:

• TV's vary a lot in power use, and most people watch them enough that they are a major user of power in the home, so shopping for a low energy use TV can save a lot of energy and carbon over the life of the TV.
• Its not that easy to get actual power use numbers for TV's, but if you use some of the resources listed below, you can easily find a TV that uses (roughly) half as much power as its next door neighbor on the store shelf, and has just as good (or better) a picture.  You will likely have to pay a bit more for it, but the energy savings over the life of the TV will pay you back, and you can save a lot of carbon emissions.
• Energy Star labels are not very helpful in their current form.

Features

We decided that the new TV for us should be:

• 
  
  Energy efficient
   
• 
  
  Have a screen size around 45 inches for our room size and viewing distance.
   
• 
  
  Support HD TV.
   
• 
  
  Have high picture quality in a bright room
   

Energy Use

One objective we have is that any new item that comes into the house has to use less power than the item it replaced -- preferably a lot less.  We also try hard to get close to the lowest power use designs available without spending the price through the roof.   This is part of our long range plan to get down to zero net electricity with the modest size PV array that we have.  Basically, our use was about 1000 KWH a month a couple years ago and we cut this down to 500 KWH a month via conservation and efficiency measures that are part of our Half Program.  We then added a 2150 watt PV array that we expect to cut our net usage by about 250 KWH a month.  So, to eventually get down to net zero electricity use, we have to cut our monthly consumption by another 250 KWH through further conservation and efficiency improvements.

Our old set used 148 watts in steady use as measured by a KillAWatt meter.  So, the objective was to get a somewhat larger screen set that did HD and used substantially less power.  This seems like a fairly tall order in that larger screen sets generally use more power and we wanted to increase screen size, but it turns out to be very doable due to improvements in TV energy efficiency and to recent developments in LCD backlighting.

Resources For TV Selection

It is not that easy to find good energy use data for TV's.  Even the models that are efficient tend to be rather vague about how much less power they use.  Statements like "uses 30% less power" are tacked on some models, but 30% less than what?

These are some resources we found to be helpful (if you know of others, please let me know):

• 
  
  Energy Star Labels
  Energy Star provides labels on some sets that meet their current criteria for low power consumption -- generally the label means that the set might use at least 20% or 30% less than an average model in its size class (or something like that -- varies with the appliance and time).
  
  We found the Energy Star labels to be more or less useless because: 
  1) they are awarded by screen size class, so a large screen set with an Energy Star label uses a lot more power than a smaller screen set with the label.  I really want to know how much power a set actually uses, not that it uses somewhat less power than the other energy hogs in its size class.
  To me this use of screen size classes is a flawed idea -- It would be kind of like giving a Hummer an Energy Star label because it has the best fuel economy of the Ultra Pig class.  It hides the basic truth that larger screen TV's use more power.
  2) the Energy Star label requirements can be very flaky.  Up until recently TV sets were only rated on how much power they used when they were turned off!
  3) I guess the Energy Star folks think we are too dumb to know what a watt is, and are trying to get to something that is easier to understand, but to me the label just hides important information. 
  Oddly, the Energy Star yellow labels that are required for all clothes washers and refrigerators provide all the information you need on a simple and easy to use label  -- no idea why we can't get this on TV's, which can actually use more power than a fridge.
   
• 
  
  Energy Star Database
  The Energy Star database on power consumption is much more useful.   The spreadsheet like listing for all Energy Star qualified TV's are here ...
  This listing does give power use under various conditions and estimated annual use. 
  If you are spreadsheet savvy, you can download the file and sort it by power use, or whatever you like.
   
• 
  
  Consumer Reports
  Consumer Reports magazine (or the website) gives some useful info on TVs.
  Unfortunately they just give you a poor -> good rating scale on energy use without giving specific numbers.  And, they don't provide any information on how they go about determining the energy use rating.
   
• 
  
  CNET Reviews
  I found the CNET reviews the be the most helpful resource for information on how the sets perform visually, and on their energy use.
  They have a good review process that includes energy use numbers for various viewing modes.
   
• 
  
  KillAWatt
  At one point when we were getting a bit frustrated with trying to find actual power use numbers for some sets we were interesting in, we actually brought along a KillAWatt to the store to measure power use.  The store people were very cooperative in this -- no push-back at all.
  The down side of doing it this way is that many sets have a "store mode" that that the set can be put on that is intended to provide a very bright picture for in store comparisons of picture quality.  This "store mode" uses more power, and can be a bit misleading. 
  
  
  
  

  What We Picked

  The TV we picked is a Sharp 46 inch -- Sharp LC-46LE700UN
  
  As it turned out, for LCD sets the big recent development that does make a significant difference in power consumption is the LED backlight.  The sets with LED backlights use substantially less power than sets with the still more common fluorescent backlights.  
  
  At this time, you do pay a cost premium for the LED backlighting.   In our case, the LED backlit models were about $200 more than similar performance models with fluorescent backlights.  But, we believe (based on actual power measurements) that over the life of the set and with our viewing habits, the power saving at current utility rates would pay back the extra with a bit of interest, and the carbon emissions saving over the life of the set is significant. 
  
  LED backlit sets also have a much longer life -- long enough so that its unlikely you will ever have to replace a backlight.
  
  While LED backlit sets as a class have lower power consumption, there is still a significant difference in power use between the various LED backlit models.  So, it still pays to look into actual power use of the sets you are considering even if they are all LED backlit. 
  
  The set we got has a feature that adjusts the backlight intensity to the room light level.  That is, it turns the backlight down when room lighting is lower.  I have found that this saves a significant amount of energy -- so, its probably worth looking for these kinds of features.
  

  
  Power Use

  I figure our TV is on around 8 hours a day -- this seems like a lot, but I think its pretty close -- we each tend to want to watch different things and we have digital recorder -- both of these extend the time on.
  
  New Set:
  

  Power use per year = (8 hours/day)(360 day/yr)(68 watts) = 196 KWH per year

  Cost of electricity at 11 cents/KWH = $21 per year

  CO2 emissions at 1.5 lbs/KWH = 294 lbs of CO2 per year

  
  

  Compared to the old set, this is a saving of 230 KWH a year, $26 per year, and 350 lbs of CO2 a year.
  
  Its a bit hard to compare the savings for this TV to other new ones out there.  But, its certainly safe to say that if you don't consider power usage when you do the selection you could easily end up with power consumption that is more than twice the numbers above -- its important to do your homework.
  
  

  Findings To Date

  We are very very pleased with the new TV. 
  
  The picture is just outstanding -- my untrained eye just cannot find any flaws.
  My feeling is that some of the places that do TV reviews (including my favorite CNET) obsess over tiny picture quality details that most people will never notice.  I think that they don't feel they are earning their paycheck as reviewers if they can't find some flaws in the picture to comment on.
  
  The power consumption is actually lower than anticipated.
  The set has this very neat feature that you can enable that adjusts the back light level depending on room light.  So, in a bright room with sun streaming in the windows, the power consumption is 83 watts, but as the room gets dimmer because you lower some shades or at night, the power consumption drops all the way down to 51 watts!  So, under night viewing conditions, the new 46 inch set uses only about 1/3rd the power that our old 34 inch set used -- nice.
  
  The power use when the set is off is lower than my KillAWatt goes.  The CNET labs report says 0.07 watt in standby/sleep mode -- also nice.
  
  The only negative in the whole picture is the amount of work we had to put into finding a set that had very low power consumption and good performance -- its just seems like this should be easier.  In particular, it seems like the Energy Star program could be a lot more helpful than it is now.  Why can't we have the same kind of label that clothes washing machines and refrigerators have on all devices that use a significant amount of electricity (or any kind of energy)?

 Tons more conservation and efficiency ideas ...

Gary

A $1K Solar Water Heating System from the UK

This is a very nicely designed and built system by Neil in the UK. 

While the system is modeled after our $1K system, Neil has included a number of unique features including a fiberglass tank liner, a very nice large copper coil heat exchanger, integration with a combi boiler system, and a unique design for the collector absorber plate. 

Some of the highlights

Tank

The tank is tall with a small footprint in order to take up less floor space. 

Instead of using an EPDM membrane for the waterproof liner, Neil used several layers of fiberglass to provide the waterproof lining.




Collector

The collector absorber plate is a unique design that  uses a single sheet of aluminum that all of the riser tubes are thermally bonded to. 

The thermal bonding is provided by a narrow, grooved strips of aluminum that snap over each riser tube and then riveted to the

full width aluminum sheet.

Heat Exchanger

Neil made a very compact and efficient single pass heat exchanger from copper tubing as shown in this picture.




The full 26 pages writeup on how to make this system...

Details on may other solar water heating systems...



Gary