Variable Speed Solar Thermal – Reverse Return Evacuated Tube

Variable Speed Solar Thermal – Reverse Return Evacuated Tube

What sets this solar thermal installation apart from many others is the variable speed pump control and the reverse return collector. In periods of lower solar radiation (late/early day, winter and overcast/cloudy) and when there is a higher storage tank temperature, traditional fixed flowrate circulating pumps will shut the pump off to avoid cooling the storage tank. Even though there is energy available.  By slowing the loop flowrate down, more energy per unit volume of loop fluid is collected, driving the return temperature back up above the storage temperature. Simple and effective.

Variable Speed Solar Pump

By varying the speed of the pump, up to 20% more annual energy can be collected, with the rest of the system unchanged.

Evacuated Tube Solar Thermal Collector

This collector has excellent performance in low solar conditions such as when it is overcast and raining. The evacuated tube permits very little convected and conducted heat transfer which makes it tolerant to low ambient outdoor temperatures and windy conditions. Unlike heat pipe type evacuated tube collectors, each tube in this collector has a copper loop in the absorber plate, with them all manifolded, reverse return, in the header. This means superior performance at a significantly lower cost.

All of these benefits add up to a system that performs very well, year round, in our coastal climate.

With this system we can expect to displace nearly10 GJ/year of natural gas, and with an expected life of 20+years, that’s a lot of carbon!

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2 Comments

  1. We are a non-profit environmental initiative working to promote clean energy. We are wondering if we could reuse one of the images from this blog post for inclusion in a non-commercial online resource guide that we are putting together and making available as a downloadable PDF document. It will provide examples of many different types of renewable energy. It is an extension of an online educational section of our website, which can be seen at http://landartgenerator.org/outreach.html.

    Thanks for your consideration.

    Best,
    Robert

  2. Absolutely Robert, keep up the good work!
    Jason

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