In Ground water storage

[pgarch]

Hi, I am looking to install a 50Kw ETA log gasification boiler to heat a home here in New Zealand. There are some restrictive rules here that prevent gasification boilers being used here but if I go to a 50 KW unit which is bigger than I need it is not governed by the rules.

I like the idea of the storage being under ground so as to be out of site and does not occupy space, is it practical to provide the storage under ground?

The cheapest tank option seems to be a precast concrete tank that would have a fibreglass liner applied to the inside of it, is this likely to be viable, someone mentioned that concrete may not stand up to the high temperatures long term?
Here the installers recommend 25 L (6.6gal) per KW so recommend 1250l or 330 gal storage, from what I have read on here, most would indicate that is probably hardly sufficient, what would people recommend given the boiler is also likely to be a higher output than required?

Thanks for your help in advance.

Kind Regards Philip Gilchrist

 

[Nofossil]

Hi, I am looking to install a 50Kw ETA log gasification boiler to heat a home here in New Zealand. There are some restrictive rules here that prevent gasification boilers being used here but if I go to a 50 KW unit which is bigger than I need it is not governed by the rules.

I like the idea of the storage being under ground so as to be out of site and does not occupy space, is it practical to provide the storage under ground?

The cheapest tank option seems to be a precast concrete tank that would have a fibreglass liner applied to the inside of it, is this likely to be viable, someone mentioned that concrete may not stand up to the high temperatures long term?
Here the installers recommend 25 L (6.6gal) per KW so recommend 1250l or 330 gal storage, from what I have read on here, most would indicate that is probably hardly sufficient, what would people recommend given the boiler is also likely to be a higher output than required?

Thanks for your help in advance.

Kind Regards Philip Gilchrist

There is some concern about bothe concrete and fiberglass when exposed to prolonged high temps. I'm not an expert, but I'd want to talk to someone who is before putting that much time and money in the ground. Lots of people here are using large propane tanks. They can't be used for propane once they've accumulated enough surface rust and pitting, but they're quite adequate for heat storage. Because they can be pressurized, they don't require a heat exchanger and therefore provide better performance.

If you're burying a tank, give a lot of thought about how to keep the insulation dry. You'll want a LOT of insulation.

Best of luck.....

 

[jebatty]

I think 50kw translates to about 170,000 btu boiler. My guess is that the tank size info you rec'd is related to a buffer tank more than a storage tank. I use my Tarm primarily to heat storage, and then draw from storage until I need to refire the Tarm again: 1-5 days later depending on temp. If you are looking for storage, I think 1000 gal is about minimum, esp for your size of boiler.

Ditto on being careful about fiberglass. If I remember correctly, FRP fiberglass is needed for high heat. Check it out carefully.

 

[pgarch]

Thanks I will re-think that idea.

 

[DaveBP]

Philip, Don't forget when comparing costs (pressurized vs. non-pressurized) to add the price of a large heat exchanger and several more pumps and the electricity to drive them to the price of a non-pressurized storage tank. To get efficient transfer of heat as the tank gets hotter, the heat exchanger has to be bigger than most dealers recommend and they get expensive very quickly as the size increases.

You can't have too much storage. And if it's outside or underground, you can't have too much insulation. You also cannot have too much money to buy all this stuff.

Fiberglass tanks are made that can take the pressure and temperature but they are crazy expensive. They have to use epoxy resins instead of the usual polyester that is the most common. FRP was the original generic term for Fiber Reinforced Plastic or fiberglass as it became better known here in the states. I wouldn't trust it as a specific term now because it means different things in different places. Go by the test ratings.