Sizing a soalr water panels for heating purposes. - Help!

[eastwest523]

My name is Mike and I am currently trying to design a solar water heater into my old farmhouse.
The house is located in upstate NY and this is specifically a weekend home with alot of work that still needs to be done. With oil increasing I am trying to use the solar hot water panels to heat water that will be intended for heating potable water and most important for my baseboard and radiant heating.


The current system is as follows

Oil burning boiler which has 4 baseboard Zones - Copper

[peakbagger]

What you are trying to do requires some pretty extensive design. Have you done a heat load on the house yet? Trying to do space heating with solar hot water requires lots of panels as the performance of solar hor water panels drop significantly in the winter when you need to heat. Unless you have extensive energy retrofitting of the farmhouse, spend your money there. If you get to the point where you need an air to air heat exchanger as the house is "too tight" you might then justify solar hot water.

You will need evacuated tube collectors, lots of them. Plan on 15 to 20 thousand dollars of tubes. I would suggest spending money on a wood boiler with heat storage tank in place of solar hot water. You can equip a heat storage tank with multiple coils and if you still want to play with solar hot water heating.

Another then to consider is what do you do with the heat in the summer from the tubes? They are much more efficient in the summer and if you dont cover them, you will need a pretty extensive system to waste the heat.

Another reason to rethink SHW is that copper baseboard really doesnt work well at low temperatures, this also drops the efficiency of the collectors.

[eastwest523]

Sizing a solar water panels for heating purposes. - Help!

Thank you for your response.

Just to give additional information, the farmhouse has new windows and new insulation on the exterior walls. I have not done a heat load on the house and will in the next couple of weeks.

As for the Solar Hot water panels. I understand I would need many panels to heat the entire house. Maybe I need to be more clear. First Phase may be to bring the temperature in the water tank up to 80-100 degrees so during the winter the boiler would then take the tank from 80/100 to the required 180/200 degrees for baseboard.

I like your idea of the wood boiler and will do that in the future, but the problem is that this is only a weekend place. This means someone would need to be a the house to stoke the fire. I am trying to come up with a design that saves me money in the winter months when no one is as the house and the solar water during the day can help/assist in the baseboard heating. When no one is at the house we keep the temp around 52 degrees but with cold NY day/nights in the winter temperatures drop to 0 degrees at time.

The idea for three coils is to eventually purchase an insert and possibly take advantage of the insert heating water also in the future. Is there any basic diagram design you have come across that I could use as a base design.

Thank you again for your input.

[Naptown]

The problem with a preheat tank at 100 degrees is that the returns from the baseboards are probably 10-20 degrees less than the water leaving the boiler. If it was coming back at that low of a temperature the rooms at the end of the run would be very cold. So now you are driving the storage tank and solar with the boiler.
Can a home be heated with solar? Yes it can but will be a very expensive affair to do and will not work will at all with baseboard radiators. Convert to all floor radiant and you may have a chance if you install enough tubes to make it work.
Here is a link to Apricus tube collectors. In category C which would be usable for floor radiant heat 30 tubes will produce about 34000 BTU per day.
So once you figure your heat loss on the house on a daily basis for say the times you are not there on an average winter day You will know how many collectors you will need, how much storage you will need etc.
Without the Manual J on the house you are taking a stab in the dark as to how much you will need.
Keep in mind that the output numbers are based on a standard solar day which = about 4.7 sun hours a day. So during the winter months figure about 1/2 the output of the collectors.

[MikeSolar]

The problem with a preheat tank at 100 degrees is that the returns from the baseboards are probably 10-20 degrees less than the water leaving the boiler. If it was coming back at that low of a temperature the rooms at the end of the run would be very cold. So now you are driving the storage tank and solar with the boiler.
Can a home be heated with solar? Yes it can but will be a very expensive affair to do and will not work will at all with baseboard radiators. Convert to all floor radiant and you may have a chance if you install enough tubes to make it work.
Here is a link to Apricus tube collectors. In category C which would be usable for floor radiant heat 30 tubes will produce about 34000 BTU per day.
So once you figure your heat loss on the house on a daily basis for say the times you are not there on an average winter day You will know how many collectors you will need, how much storage you will need etc.
Without the Manual J on the house you are taking a stab in the dark as to how much you will need.
Keep in mind that the output numbers are based on a standard solar day which = about 4.7 sun hours a day. So during the winter months figure about 1/2 the output of the collectors.

Russ, it is worse that that: (my response from his other post)

Honestly, don't bother with trying to heat the house with solar. Concentrate on Solar water heating for showers.

Simple reason....when do we have the most sun? Summer, 14 hrs of it.
When do we have the least sun? winter, 4-5 hrs if we are lucky.

How much energy is there in the sun in the summer? 1000W+ per m2 of area for maybe 10-12 hrs
How much in the winter? If you are lucky you can get 400-500W per m2 for maybe 4-6 hrs

Even with vacuum tubes, there is not enough energy in the sun to heat your house, especially with baseboard rads.

Concentrate on lowering the heat loss of the building,, then, if there is not natural gas available, look at a heat pump. The fireplace insert is a good idea. I am getting one from the UK that has a "back boiler" in it. I haven't been able to find one over here so i will ship it over.

Add in an oversized tube system and he will have the most troublesome solar system around, and we will get a lot of bad press.

[LucMan]

What you are proposing can be done. But at what cost? The baseboard radiation will have to be replaced with properly sized cast iron or steel radiators rated at around 90 F. Then install about 250 sq ft of flat plate panels (not a fan of evacuated tubes ) and a 200-500 gallon storage tank. This would get you through Sept, Oct, 1/2 of November, March & April.
That leaves Dec, Jan & Feb. when you will get practically nothing from your system ( except maybe enough for domestic HW).
Now you can have this for about 50-80K$ you can figure out your payback from there.

[Mike90250]

if you get even just a couple hours of sun in winter, you can heat with it:

SW Montana at 46 degrees north latitude. Winters are chilly -- 8000 degree-days and down to -30F once in a great while

Home built collectors, storage tank. PEX & Slab heat. Home Quality.

http://www.builditsolar.com/Projects/SpaceHeating/SolarShed/solarshed.htm

workshop quality:

http://www.arttec.net/Solar/BarnHeat.html

don't be so quick to write off solar heating...

[MikeSolar]

if you get even just a couple hours of sun in winter, you can heat with it:



Home built collectors, storage tank. PEX & Slab heat. Home Quality.

http://www.builditsolar.com/Projects/SpaceHeating/SolarShed/solarshed.htm

workshop quality:

http://www.arttec.net/Solar/BarnHeat.html

don't be so quick to write off solar heating...

I don't write it off so easily but I do like to warn people what they may be in for. You are right that a couple of hours will provide some heat but the method the OP would use will be wasted money.

IF the system was retrofitted for floor heat in a cement mass AND there is enough storage for the "warm" water AND there is a way to protect the panels from summer overheat, THEN, I would say go for it, have fun and enjoy the solar. Don't expect huge dividends but it will be fun.

[LucMan]

I don't write it off so easily but I do like to warn people what they may be in for. You are right that a couple of hours will provide some heat but the method the OP would use will be wasted money.

IF the system was retrofitted for floor heat in a cement mass AND there is enough storage for the "warm" water AND there is a way to protect the panels from summer overheat, THEN, I would say go for it, have fun and enjoy the solar. Don't expect huge dividends but it will be fun.

If you have your radiant tubing in the concrete you don't need as much water storage as the concrete acts as your thermal storage, you can then cut back on your solar HW storage. Retrofitted staple up radiant requires higher water temps & more water storage.

Montana though colder has more sunny days than NY and much higher WH/sqft of collector, NY really bites it for winter solar insolation, between the overcast skies snow and ice, space heating just doesn't make sense.

Check out the attached simulation, this was for a proposed 224 sq ft array for a 2 story 2500 sq ft building.

[MikeSolar]

If you have your radiant tubing in the concrete you don't need as much water storage as the concrete acts as your thermal storage, you can then cut back on your solar HW storage. Retrofitted staple up radiant requires higher water temps & more water storage.

Montana though colder has more sunny days than NY and much higher WH/sqft of collector, NY really bites it for winter solar insolation, between the overcast skies snow and ice, space heating just doesn't make sense.

Check out the attached simulation, this was for a proposed 224 sq ft array for a 2 story 2500 sq ft building.

I see you use T-sol. The system could supply some heat in the winter time but look at the temps. Either use some heat rejection method or have a huge tank to do a semi-annual storage or change the glycol often, maybe every 2 or 3 years. If you can store the heat, you could use it but the hard part is matching the two.