Solar Hot Water Panels VS. Stoker Boiler

 
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beatle78
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Post by beatle78 » Mon. Mar. 10, 2008 1:48 pm

Hi guys,

I have a chance to pick up 4 hot water solar panels for < $1,000 and I was wondering if they are worth getting if I have a stoker boiler?

I'm thinking more along the lines of summer use. Here's our draw on hot water: Family of 4, dishwasher, laundry. Random use throughout the day

If I put in the HW solar panels, would I be wasting coal in the summer and be better off using the oil as a backup to the panels for the HW?

I've always used oil to heat everything so I'm not sure what the best route to go is?

Thoughts? Experiences?


 
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Rob R.
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Post by Rob R. » Mon. Mar. 10, 2008 2:08 pm

What size/capacity are the solar panels?

 
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LsFarm
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Post by LsFarm » Mon. Mar. 10, 2008 2:10 pm

You need to know how much hot water you are using. The best way I can think of figuring this out would be to look at how much oil you were burning during the summer.. This oil consumption should be just for domestic hot water from roughly May through September.
Then using the BTU's the oil and in coal, you can calculate if burning coal makes sense.

Then you can see how long it will take to pay back the investment if you purchase the solar panels... And they may not provide enough hot water, so like you said you will still need to have the oil backup, or electric..

If maintaining the coal boiler and buying,transporting coal is not a big issue, I'm betting the coal boiler is the most economical..

Do you have any neighbors who solar heat their domestic hot water who you can compare notes/ use rates, recovery rates with???

Greg L

.

 
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Dallas
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Post by Dallas » Mon. Mar. 10, 2008 2:16 pm

I used to install DHW solar systems. Of the brands, which I sold/installed, they required 3 panels for the gov. grant, then in place. They all used a hot water heater/tank for storage and back-up. The power company had meters on my system. Their analysis, was that it did 65% of the DHW heating for our family of four, on an annual basis, in NE PA.

 
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Post by LsFarm » Mon. Mar. 10, 2008 2:21 pm

Hi Dallas, any chance you have a breakdown by month or season?? The % of DHW heated would be a lot less during the winter, cloud cover and short days and The coal boiler will be running during the winter anyway...

If you were getting 65% year-round, it must be close to 95%+ during the summer ??

Greg L

.

 
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Post by traderfjp » Mon. Mar. 10, 2008 2:30 pm

I heat a 30k gallon pool with 7 solar panels. If you have a southern exposure I would think that in the summer the panels (one or two) would do 90-95% of your hot water needs. Oil is only going up in the long haul so eventually the panels will pay for themselves and are a fantastic green selling point when you sell your home in the future. I'm thinking of doing something with the panels I have now. I may take one and hook it into my hot water system. If the system is left on all year then a antifreeze needs to be used with an inderect hot water heater. The initial costs can get expensive. If I only use the system in the summer months then I can run the water from the panels directly into my heater and then when it get cold again I can winterize the system. Coal doesn't heat my hotwater so I would still use some oil.

 
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Dallas
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Post by Dallas » Mon. Mar. 10, 2008 2:31 pm

LsFarm wrote:Hi Dallas, any chance you have a breakdown by month or season?? The % of DHW heated would be a lot less during the winter, cloud cover and short days and The coal boiler will be running during the winter anyway...
If you were getting 65% year-round, it must be close to 95%+ during the summer ??
No, that was a long time ago and I don't know whether it was broken down, in any case. Cloudy days weren't the end of the world, as there was heat to be had, even though not so much.

I do have parts of a new system, which I'm going to look over some day and make available.


 
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Post by Yanche » Mon. Mar. 10, 2008 3:03 pm

In the 70's I installed a high end three panel DHW system. Copper plate panels, anti-reflective selective coating, glass, proportional controller, etc. Part of a government grant program that evaluated various types. It was well instrumented. Strip chart recorders, power meters, etc. The system was engineered by a local Taco engineering sales team. Worked well for about 4-5 years. But prone to leaks and reliability issues. Now removed from service and everything junked but the solar panels. Knowing what I know now and my since acquired engineering and fabrication skills it could have been made to work longer. The engineering just was sub par with no long term reliability assessment. For example when power failed during a high sun condition the anti-freeze solution turned to acid and would eventually ruin the valve stem packing and seals in the air vents. It took me a few years to find out what was happening and the resources of a top notch research laboratory. I now heat DHW with coal.

 
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Post by beatle78 » Mon. Mar. 10, 2008 3:54 pm

LsFarm wrote:You need to know how much hot water you are using. The best way I can think of figuring this out would be to look at how much oil you were burning during the summer.. This oil consumption should be just for domestic hot water from roughly May through September.
Then using the BTU's the oil and in coal, you can calculate if burning coal makes sense.

Then you can see how long it will take to pay back the investment if you purchase the solar panels... And they may not provide enough hot water, so like you said you will still need to have the oil backup, or electric..

If maintaining the coal boiler and buying,transporting coal is not a big issue, I'm betting the coal boiler is the most economical..

Do you have any neighbors who solar heat their domestic hot water who you can compare notes/ use rates, recovery rates with???

Greg L

.
Te be honest I never watched it that closely. I guess I can watch it this summer since I will be running on OIL :(

Our usage went up now that we have a second child too.

I can't stand to pass up what seems to be a bargain (4 - 4'x8' panels <$1,000), BUT only if it will be worth it in the long run.

 
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Post by beatle78 » Mon. Mar. 10, 2008 3:55 pm

markviii wrote:What size/capacity are the solar panels?
They are 4 - 4'x8' panels. I'm not sure about the capacity. They were made by U.S. Solar corporation. They were stored inside a house some guy bought and he wants to sell them.

 
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Post by sandman » Mon. Mar. 10, 2008 5:24 pm

if it's just for the panels it seem like too much to me. I bought a whole system (used) with 2 4 or 5 x8 panels for 750

iv'e seen the panels for $100 each in the want ad

as too "are they worth it" I think so. I plan on pre heating my water (before the boiler or oil fired hot water heater) with them this summer and in the winter taking the panels out of the "pre heater loop" and tieing it into a coil on the wood stove.

at my camp I want to rig them up to a cast iron radiator for the in between month's when we need some heat but don't really need to have the stove running.

 
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Post by beatle78 » Mon. Mar. 10, 2008 9:34 pm

sandman wrote:if it's just for the panels it seem like too much to me. I bought a whole system (used) with 2 4 or 5 x8 panels for 750

iv'e seen the panels for $100 each in the want ad

as too "are they worth it" I think so. I plan on pre heating my water (before the boiler or oil fired hot water heater) with them this summer and in the winter taking the panels out of the "pre heater loop" and tieing it into a coil on the wood stove.

at my camp I want to rig them up to a cast iron radiator for the in between month's when we need some heat but don't really need to have the stove running.
ok, thanks. I thought it was a good deal. How expensive is the rest of the system?

I envision some pex supply return to the panels, a pump, and a heat exchanger. They come with mounting hardware for the roof.

 
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Post by traderfjp » Tue. Mar. 11, 2008 1:07 am

Yanche: Was your panels made from copper tubing? If so was it one big loop? Do you think a DIY solar panel is doable? I currently have plastic and they work well but I've been replacing one every two years.

 
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Post by sandman » Tue. Mar. 11, 2008 5:07 am

beatle78 wrote:
sandman wrote:if it's just for the panels it seem like too much to me. I bought a whole system (used) with 2 4 or 5 x8 panels for 750

iv'e seen the panels for $100 each in the want ad

as too "are they worth it" I think so. I plan on pre heating my water (before the boiler or oil fired hot water heater) with them this summer and in the winter taking the panels out of the "pre heater loop" and tieing it into a coil on the wood stove.

at my camp I want to rig them up to a cast iron radiator for the in between month's when we need some heat but don't really need to have the stove running.
ok, thanks. I thought it was a good deal. How expensive is the rest of the system?

I envision some pex supply return to the panels, a pump, and a heat exchanger. They come with mounting hardware for the roof.
i'm not sure, mine came with a 80gal water tank with two coils (one for water the other for the panels) and a contoler ( a big board with seveal pumps and a ubnch of other stuff). what kind of panels were they and how old are they? if there new and evacuated tubes they might be worth it. if there 20 year old flat panels i'd pass

 
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Post by beatle78 » Tue. Mar. 11, 2008 8:26 am

sandman wrote: i'm not sure, mine came with a 80gal water tank with two coils (one for water the other for the panels) and a contoler ( a big board with seveal pumps and a ubnch of other stuff). what kind of panels were they and how old are they? if there new and evacuated tubes they might be worth it. if there 20 year old flat panels i'd pass
WOW, you got quite a setup for $750. good score!! :D
They look like panels from the 80s... I guess I'll let these go.

What are evacuated tubes?


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