I'm in the process of purchasing a multi-family house, and am toying with the idea of solar-thermal and/or geo-thermal and/or arbitrary heat sources to assist with space heating and domestic hot water.
The current owners are removing an oil tank prior to the sale, as this is standard procedure, and likely highly regulated. As such, I have no idea if it would be allowed, but would it make sense to offer to replace the tank with a water/glycol tank? In a rational world it would lower his price to back fill the void.
This would essentially function as a thermal battery. Unfortunately, there isn't much room to do it in the building. With geothermal I could get it to around 160 F/71 C, but being as the system was designed for steam, even replacing the radiators might not leave me enough surface area to match the current performance (which isn't bad, just expensive). If I wanted water temperatures closer to 90 C, I could use solar thermal, or something else (e.g. a water jacket on a source of heat, as is seen on some fireplace inserts) to get it closer to 200 F/96 C.
There may be a smarter way to lay it out, that's just an example, but one limitation is that I may have room for just one more normal-sized tank/boiler inside. A detached garage with a second level would be probably the next best option. I'm presuming it would not be practical to get the same level of insulation with an above ground tank in the garage, though I could be wrong about that.
I realize I could tune up the current steam system, and save a little money, while spending little out of pocket. I'm also interested in a greater ROI while saving the planet, so I'm hoping to approach something like a 75% reduction in NG usage.
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