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Solar water heater for baseboards

 
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I have an idea and need some information on if anyone thinks this can work. I currently have a baseboard system running throughout my house, that’s runs off of a very inefficient cast iron boiler. I would like to replace the boiler with a DC hot water heater. Can this be done or what would you want for this.
 
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Hi Brandon, Welcome to Permies! An excellent first post :)
Does your baseboard run hot water, or steam? Either one would work with a water heater, steam might be more difficult, as water heaters are generally not made to actually boil water, and most common ones top out at 145-160 degrees, if even that hot. If it's running water though, that is a fine temp. If its running water, and you have to go down in temp from what it currently runs, increase the rate of circulation, to balance out the lower temperature, keeps the system running fairly evenly.

More information would be helpful, including your heating requirements, gardening zone would tell us a lot, but in general, you certainly can do it.

:D

 
pollinator
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Welcome!

First thing is to get some sort of scientific guesstimate of how much heat you are using.

Are we talking a wood fired boiler? Whatever the fuel, knowing how much you are using for a given period is the start.

Then see what you can find for an efficiency rating or a best guess at one.

Convert to kilowatt hours, and see what sort of power input you will need..

Are you looking at DC because you are off grid? The number you come up with may be quite challenging if so!

Lots more info like available resources, climate, insolation, etc will help with further advice!


 
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Rather than generate solar electricity, store it in batteries, then run a water heater with the electricity, why not heat water with solar collectors, store it in an insulated tank, and circulate it directly to the baseboards?
There would be little loss from conversion, and if the storage tank is within the heated envelope, even storage losses will help heat the house.

A "drainback" system would eliminate the need for antifreeze in the system.
Builditsolar has a simple DIY version.
 
pollinator
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I support your idea.

With a big enough buffer tank you can store the sunlight and use it during the night.
With a air/water to water heat pump and the same buffer tank you can use the sunlight to cool in the summer.

Here is a cool setup
http://electrodacus.com/DMPPT450/dmppt-presentation-v01.pdf
 
master pollinator
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It is possible...

This is not really a problem per se, that is I am not saying "the problem with base board heat is..." because I am not saying that at all here. Baseboard heat has its place, but a person has to understand that baseboard heaters are small, and that can be a very good thing in homes at times, but it also means because they are small in size, the water going through them has to be really hot.

Keep this in mind, it is going to take X amount of BTU's to heat your home, no matter what you have for radiators, or what you have for a heating method.

For your home, you have two options.

1) You can either change out your baseboard heating so that you have a bigger radiator, and thus can use lower temperature heat to heat your home (less intense heat over a bigger area)
2) You can design a alternative energy system to work with the small, but higher temperature heaters (a bigger sized

The better alternative is to go with a bigger radiators, which would probably be radiant floor heat. They can be added to a home, but it is a pretty big job, and expensive, but it is the best way because you will have a lot more options since the intensity of the heat would not need to be so high.

The former is not likely to be in the cards, so now you must decide on how involved you want to get. Heat and electric just are not that efficient, so trying to scale a solar array to make enough power to power a DC water heater, that heats your home, is going to be tough. You are really going to have to think of using solar water heating, if you are determined to use solar.

I am not sure if that will get you where you need to be, 180 degree water is pretty darn hot.

It depends on where you live, but if you are rural, compost heat might be a better answer. It will not get you the 180 degree water that you need, BUT it will get you close. If compost heat can get your water to 140 degrees, then your boiler will not have to work nearly as hard to get it to 180 degrees. That will save you a lot of money. It will not be 100% alternative heat, but it will vastly improve your situation.

But why I suggest compost heat is, it will get you 140 degree water 24/7 throughout the heating season. That makes a huge difference. With solar hot water, you only have a few hours where you are going to get the heat you need. If you can do compost heat where you live (rural area) it will be less costly, and work well with your baseboard heating system. It will reduce your heating costs by 2/3 to 3/4 and should be pretty simple to adapt to your heating system.

If you want a fun research project, check out compost heat, or Jean Paine and compost heat. Because of your system, you are just using compost heat to help preheat the water going to your boiler.
 
Travis Johnson
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Added to say: It is possible that compost heat could 100% heat your home, it just depends on the amount of radiator space that you have. If you have more than enough baseboard, then you could run 140 degree heat, more often, and heat your home since it is available 24/7. But if you barely have enough baseboard, then my first reply will be more likely, a 2/3-3/4 reduction in consumed oil or propane from the boiler.

You can tell by how often your boiler runs, and how often your zone valves cycle on and off.
 
Brandon Gutierrez
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Wow. The feed back is amazing and there are some great ideas. Let give a little more info: I am not working off grid just looking to add supplemental heat to my home. Currently the baseboard heater is a cast iron propane unit. I quit using it because it became to expensive and replaced the heat source with 2 5-ton heating and cooling units (all electric). I live in New Mexico and where my house is the elevation is 6,900 ft.
I like the idea of using direct heating of the water but would like to have the use of the energy storage (batteries) for other uses during non winter months. I am a complete virgin to solar use and thought this would be a good way to start without to large of an upfront cost.
 
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I’ve posted this video of Kaspar Moth-Poulsen of Chalmers University discussing his liquid solar fuel in other threads. The molecule norbornadiene into its heat-trapping isomer, quadricyclane after being exposed to sunlight (currently UV & blue spectrum) can be stored for up to 18 years and reused many times. The temp increase of the liquid carrying the molecule is currently 63 degrees Celsius (113 degrees Fahrenheit). They believe they will be able to achieve at least 110 °C (230 °F) or more increases. So using the more optimistic numbers if the liquid carrying the molecule is 10 °C (50 °F), then the resulting temp after passing the catalyst will be in the order of at least 120 °C (270 °F). Steam is created at 100 °C (212 °F) at standard pressure, so retrofitting a steam or hot water heating systems seems doable w/o major changes. I see potential uses in distilling water, heating greenhouses and perhaps even generating electricity.



Photo credit: (Chalmers University of Technology)
ECB7B965-2B9F-447B-921B-F4F03AA3E726.png
[Thumbnail for ECB7B965-2B9F-447B-921B-F4F03AA3E726.png]
 
D Nikolls
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Brandon Gutierrez wrote:Wow. The feed back is amazing and there are some great ideas. Let give a little more info: I am not working off grid just looking to add supplemental heat to my home. Currently the baseboard heater is a cast iron propane unit. I quit using it because it became to expensive and replaced the heat source with 2 5-ton heating and cooling units (all electric). I live in New Mexico and where my house is the elevation is 6,900 ft.
I like the idea of using direct heating of the water but would like to have the use of the energy storage (batteries) for other uses during non winter months. I am a complete virgin to solar use and thought this would be a good way to start without to large of an upfront cost.



Great, so easy to play around as you have not one but two other ways to heat!

Batteries are expensive, heating with electricity stored in batteries is thus also rather expensive. Hence, the many ways people have thought up to store the heat some other way.

Insulated tanks are neat, and could be a nice fit with the plumbing you have, depending on all that stuff Travis shared.

You could also heat any other sort of mass when the sun shines. 'Electrodacus' designed and uses a PV system relying on the mass in his cement floor for thermal storage; it's a particularly neat system because it dynamically allocates arrays of solar panels to battery charging and sends surplus power to the thermal application; once the batteries are full everything goes to thermal.



I find it useful to think about the units in play..

My $6,000+ LiFePO4 battery bank has a nominal capacity of about 8 kilowatt-hours. In practice more like 6KWh usable.

To raise one kg(basically 1 litre) of water by 1C, takes 4,184 joules, aka 1.16 watt-hours.

So, if I use my 6KWh of juice to heat 100L of water, I would have raised the temperature by 6kwh/(1.16wh*100L)=51.7 degrees celcius. If this water was room temp at the start, it is now about 71c. Of course if it was fresh from my above ground tank it's more like 53C..

Enough for a couple showers, but it's not going to heat even my tinyhouse for long, and I will be flat out of power until the next somewhat sunny day. No fridge, lights, power tool battery recharging..
 
pollinator
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Brandon Gutierrez wrote:Wow. The feed back is amazing and there are some great ideas. Let give a little more info: I am not working off grid just looking to add supplemental heat to my home. Currently the baseboard heater is a cast iron propane unit. I quit using it because it became to expensive and replaced the heat source with 2 5-ton heating and cooling units (all electric). I live in New Mexico and where my house is the elevation is 6,900 ft.
I like the idea of using direct heating of the water but would like to have the use of the energy storage (batteries) for other uses during non winter months. I am a complete virgin to solar use and thought this would be a good way to start without to large of an upfront cost.

so the least expensive solar option since you have the heat pumps is to use them more and add a net metered solar array. Heated solar hot water produces about 3 times the HEAT kWs as the same area of solar electric panels but the heat pumps give you about a 3 to 1 advantage over using electricity to heat things directly. All that to say there would be no advantage to using solar hot water. If you did not have any of that infrastructure already solar hot water would make sense.
 
Whatever you say buddy! And I believe this tiny ad too:
Building a Better World in your Backyard by Paul Wheaton and Shawn Klassen-Koop
https://permies.com/w/better-world
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