Saturday, February 12, 2011

New: PV pump for solar DHW, 3 day EV conversion, PV system sizer

Just a few new content items on Build-It-Solar:

TOPSFLO PV powered pump for solar water heating systems:
This is a new and very low cost pump that is intended for circulating water in solar water heating systems.  Its a DC pump and is designed to be driven directly by a small PV panel.

It has a startup head capability of about 9 ft, and a nominal flow rate of about 2 gpm -- good for 60+ sqft of collector area.  It is also good for temperatures up to 200F and has automatic shutdown for higher temperatures.  Its a brushless design and should provide a long life.  But, it is new, so I suppose there is a bit of buyer beware. 

Thanks to Rodney for sending in a note on this.

Gas to Electric Car Conversion in 3 Days!
This is an interesting project that took on converting a small gas powered Daihatsu Charade in a weeks time -- they actually managed to do it in 3 days!

They did quite a nice job of documenting the whole thing including a very nice video that gives a good feel for what's involved in a EV conversion.  I suppose its only fair to say that there were as many as 10 of these guys working on the car at once -- it might take one of us a bit more than 3 days.

PV System Designer
This is a handy calculator to get several alternative actual system definitions based on your available PV panel area, climate, and power range you are interested in. 

It will pick several alternative actual systems based primarily on lowest price.  The definition includes specific PV panels and a specific inverter with prices, but does not include other details that make up the system -- so, there are still a lot of things to add to get to a full system.

Getting close to putting up the detailed how-to on our new, simple, solar water + space heating system -- maybe Monday.

Gary Feb 12, 2011


  1. This solar pump is only $62 each if you order 4 of them. I've got a couple on the way for testing.

  2. Hi Kevin,
    Could let us know how they perform and how the workmanship looks?

    They look to be somewhat like the SwiftTech pumps, but with a higher temperature capability and built better for not much more money. Hope they live up to expectations.


  3. Other than being driven by DC, I'm not too impressed with the photo. They look to be mostly plastic, and have threaded fittings, which makes plumbing more difficult.

    I really like the Taco and Grundfuss pumps. They have sturdy cast bodies, contactless magnetic drive, and flange fittings that are simple to change out in a hurry. I don't believe I paid a whole lot more than $62 for them, either.

  4. Hi Bytesmith,
    The Grundfos and Taco pumps are built like tanks and certain last a long time. But, they use a lot more power -- typically more than 50 watts compared to the 15 or so watts these small DC pumps use, and those nice heavy cast iron casings may actually have a shorter life than an high quality plastic case in open systems (like drain backs) that have some oxygen in the water. If you go up to a bronze case Taco the prices are more like $300.
    I think it will be interesting to see how this small DC pump does in service.

    For people who want a well proven, efficient, pump that is made to be driven direct from a PV panel, the Laing D5 series has a really solid reputation -- at around $200.


  5. The topsflo pump is a bit louder than TACO, Wilo and Grundfos. Just as Gary says, in an open system, like a recirculation freeze protected system, these compare to a bronze or stainless pump for 3X more $$. I measured 17 watts with my Kill-A-Watt at full load. No check valve to take apart for drainback.

    The supplier gives lots of warnings about not running them dry. They'll got too hot pretty quickly and melt.

    The cost is closer to $90 delivered.

  6. Thanks Kevin -- I'll add your comments to the pump description.


  7. Topsflo update:

    Now $60 delivered. My pump is still working great, I'm very excited about this new pricing from

    ATTENTION all users of pink pumps in open systems: they will fail after a few years, so get some of these to replace them.

  8. Topsflo update #2:

    Using a 500mA "wall wart" as the power supply, I'm measuring only 9W used by this pump at 1 gpm. Since that's only about 100mA, a smaller power supply might use even less power.

    This low power consumption means that a system with this pump will have a COP many times higher than systems with Grundfos or Taco pumps:

  9. Congress needs to get their heads out of both their constituents and their own asses. The earth is getting hotter. The economy is getting worse. Technology is advancing by incredible leaps every year, and we’ve got nearly 10% of our population unemployed. Why, again, aren’t we making bigger investments in solar power?


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