Nat. Gas vs. Solar Thermal Water Heater

[Mikesolar]

Originally Posted by Exeric

There may be a third option, but it would depend on your future plans. It also has the disadvantage of there not being a fuel backup if your electric grid went down. Many people are trying to go as electric as possible because they can subsidize their electricity use with PV power. This would have the same effect as zeroing out the future expenses for water heating. That's if New Mexico is a grid tied state?

I personally plan on going that route. I've already bought an electric Marathon water heater which is a fiberglass design and is supposed to last a lifetime because it doesn't have the usual rusting out problem. They are about a thousand dollars. I think it is wise to think not only about the grid going down and causing cold showers. Cold showers can also be caused by mechanical failure. Solar hot water heaters have a very poor track record in this regard. Also regular metal water heaters last only about 10 years and then rust out. So a Marathon fed by PV is a very viable option compared to what you are considering. Of course, PV can be used for a thousand other things also which makes it more flexible even than cheap natural gas.

This is and issue. As solar PV gets less expensive, SDHW looks less viable especially with the mechanical issues of an improperly installed system. I have a number of 25 year old systems still working fine and some failing after 5-6 years. I won't install tube systems anymore because a higher percentage fail and they fail faster as well.

I have found that the best SDHW systems are ones that are PV powered (20w panel) and have no other controller to muck up (which is what has failed in 40% of the systems I see). They also are not SUPER efficient, generating high temps like a tube does. Doax made a system that I think could work well for many years.

[TimJFowler]

Originally Posted by Exeric

There may be a third option, but it would depend on your future plans. It also has the disadvantage of there not being a fuel backup if your electric grid went down. Many people are trying to go as electric as possible because they can subsidize their electricity use with PV power. This would have the same effect as zeroing out the future expenses for water heating. That's if New Mexico is a grid tied state?

NM is a grid-tie state.

I am considering Solar PV. Of course, we have a few issues there as well. Our roof ridgeline (simple pitched roof) runs North-South, so any solar panels would require racks for good solar alignment. We also have 3 mature trees on the west side of the house that provide good afternoon shading in the summer.

I'm crossing my fingers that our city is able to work out a community solar PV garden. That would allow individuals to own PV with optimal siting and hopefully at a price discount.

Tim

[TimJFowler]

Originally Posted by Mikesolar

If you move the cold water directly up to the attic to be warmed, what will you do with the condensate that is generated?

Other than that it is not a bad idea.

Our attic is well ventilated so it is warm in the summer, but much less so in the winter. Plus there is the condensation issue.

[TimJFowler]

Anyone have experience with Heliatos Solar and their Solar Hot Water kits?

The GH Kits are advertised as freeze rated to -17°F, which should be plenty of range for our climate. I like the overall simplicity of the system, expandability, retrofit to any standard water heater and the price.

This setup is appealing, but I assume there are drawbacks and issues I'm not familiar with.

Thanks,
Tim

[Exeric]

Originally Posted by TimJFowler

NM is a grid-tie state.

I am considering Solar PV. Of course, we have a few issues there as well. Our roof ridgeline (simple pitched roof) runs North-South, so any solar panels would require racks for good solar alignment. We also have 3 mature trees on the west side of the house that provide good afternoon shading in the summer.

I'm crossing my fingers that our city is able to work out a community solar PV garden. That would allow individuals to own PV with optimal siting and hopefully at a price discount.

Tim

Well, that definitely makes it hard to have PV. Good luck with the community solar PV. I hope it works out for you.

[Mikesolar]

That SDHW system you mentioned is kind of cobbled together. Not too professional.

[jeff5may]

I say use a pv-t panel array running a drainback loop. You could rig the loop to a mini heat pump if you wanted to. Buy a long lasting water heater of whatever heat source you want. The pv-t panel array would pay for the whole rig eventually.

[Mikesolar]

Here are the results of our PVT design, done last year.
It is, in my opinion, good for pool heating but not quite so good for DHW although still a valid technology.

The pic shows two identical panels, one with the grid PVT and the other just PV.

[jeff5may]

Originally Posted by Mikesolar

Here are the results of our PVT design, done last year.
It is, in my opinion, good for pool heating but not quite so good for DHW although still a valid technology.

The pic shows two identical panels, one with the grid PVT and the other just PV.

Being in New Mexico, I don't imagine pool heating would be necessary most of the year. It could turn into a big hot tub pretty quickly in the summer. However, a pool makes almost as good a heat dump as a cooling tower for less watts.

[Mikesolar]

We sometimes run the pool pump at night through the panels to cool it down when it gets too hot but that is with plastic panels. Not sure how the PVT would work.