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Solar powered HRV theory... ?  RSS feed

 
Sean Rauch
Posts: 136
Location: Winnipeg, Manitoba
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So I'm thinking about how to make an HRV work efficiently in my super cold climate winters...
This would be in a super efficient passive solar building envelope.

One common problem is the temperature differential can be 50C between outside and inside air. Anyhow here is my theory and maybe someone who knows can give some feedback.

I'm thinking of using a solar air heater to preheat or postheat the incoming air of the HRV.

Theoretical option 1: I have a solar preheating panel that is used to bring up the temperature of the incoming air before it hits the HRV so that I"m not overburdening the HRV and helping to keep the incoming air as warm as possible. The main problem I'm seeing is that the solar preheater will be useless outside of peak sun hours, in other words its just pulling cold outside air directly into the HRV at night. So an efficient solution I'm envisioning is to have the HRV fan run off a solar panel so HRV is only drawing air based on sunlight and thus its pulling air from the solar air heater during a time when it is functioning. It costs zero electricity and should be efficient.

Theoretical option 2: same as above except air passes throught solar air heater after it goes through the HRV so I'm boosting the air temp of air that has already be prewarmed by the HRV (assuming I'm using a high efficiency HRV that is over 90% efficient) This would mean that I don't have to find another way of filtering incoming fresh air and maybe it would help with overall heating?

Think this could work?
Which option would be the best?
Would the lack of air changes during dark hours have a negative effect wrt mold etc? Does is matter that air really isn't moving while its dark?
 
Brian Knight
Posts: 554
Location: Asheville NC
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Sean, correct me if iam wrong but I think you asking if your pre-heated air should be added before or after the heat exchanger part of the HRV. I think the configuration of most HRVs will only allow you to add it before which I think is where you would want it for condensation/frost reasons.

As to your performance concerns, not running it all night would certainly result in poorer IAQ but perhaps you could set it up to run more during the day and less during the night. That's a big advantage to using mechanical ventilation with intelligent wall controls.

I think the best way to use solar will involve a 3rd option; solar thermal. Iam not very familiar with Zhenders but I think most in that price range have an option for a pre-heater loop (probably internal loop of copper or PE to run fluid through).

This loop is typically used for a geothermal setup which would be a much better way of using the ground temps as opposed to the earthtubes earlier mentioned. Iam skeptical of these in most climates but in your extreme location, the main concern, pump energy would probably be a net gain for the total energy use picture.

You would of course want to talk to a sales rep before running solar water through a loop intended for geo because it would typically be much hotter. I bet you could install a tempering valve to send the solar water to the unit at the upper end of the accepted range. Naturally, you would be storing the solar thermal for night time use. I think I would prefer this set up to radiant floors but you are still introducing much of the same technology and concerns that go with it.

Ive also heard rumors of people using this pre-heater loop with woodstoves which of course translates to RMH. You could have a storage tank that receives both solar and biomass input.
 
Sean Rauch
Posts: 136
Location: Winnipeg, Manitoba
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I guess I didn't explain it too well, what I'm thinking is that I would have the filter before or after the solar air heater?

I'm starting to shy away from solar thermal water systems because of the complexity and costs, I may build with a future system in mind so that adding it later is a simple task. I'm also putting the RMH aside as my place will be insured and inspected, I like the performance but it has some serious hurdles to get over.
 
money grubbing section goes here:
The $50 and Up Underground House Book by Mike Oehler - digital download
https://permies.com/wiki/23442/digital-market/digital-market/Underground-House-Book-Mike-Oehler
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