Monday, June 28, 2010

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 ...


Friday, June 25, 2010

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

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...


Tuesday, June 15, 2010

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!


Saturday, June 12, 2010

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...


Thursday, June 10, 2010

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.


Wednesday, June 9, 2010

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 :)


Sunday, June 6, 2010

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!

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