The problem with geothermal is the ground is about 50 degrees (varies though) consequently it is a lot more efficient to cool with geothermal then it is to heat with geothermal, this makes geothermal more ideal for warmer areas where heating isn't as critical as in NH. In order to get a (traditional) geothermal system you would have to drastically oversize the system to meet your heating needs.
There is no "oversizing." The system is sized to the heating/cooling load.
Often, we will actually undersize geothermal, by sizing it to the cooling load (typically about half the heating load), and using fossil fuel to cover the very coldest part of the year.
I'm not sure about the south facing wall with radiant floor heating/geothermal with floor cooling... cooling through the floor is a poor may to do it, it may sorta work in NH but in most places would just result in a hot, humid house with a constantly damp floor from condensation.
Properly-designed radiant cooling systems incorporate humidity control, which does not allow the floor to get below the dew point.
I don't understand why it has to be a forced air system. Seems like a heat pump could be used to heat or cool liquid for radiators or baseboard systems, or whatever.
The limitation is temperature. Peak outlet temperature on a water-water geothermal system is 125 degrees, and efficient operation really needs the water temp to be 110 or lower (just using the higher temp for domestic hot water, not space heating). That's not hot enough for baseboard, which really needs 140-degree water. Large radiators can be used (sized for 110-degree water, rather than 212-degree steam or 180-degree water, as are typical), but that can cost a lot. Forced-air uses lower temperatures, so it's often the most cost-effective way to use geothermal.
In-floor radiant can often run with lower water temps (90-110, depending upon the floor construction), so it can be used for heating, at least. When the humidity is low enough, it can also be used for cooling. Alternately, wall-mounted blower units can be used - they look sort of like a space heater, but are operated by hot or cold water - that eliminates the need for ductwork, and gives room-by-room control.
I don't see how people come up with idea that geothermal is about the same price as a traditional system... basically you have pretty much all the same expenses PLUS the real big expense of digging around in your yard installing ground loops and don't forget... a backup heating system is pretty much essential.
Unless you are intentionally doing a hybrid system, there's no need for a fossil fuel backup.
Regarding the costs, when folks say that it's similar, it's probably because they had a high-producing well, allowing them to run an open system, eliminating the cost of a second well. You need about 2 to 3 gallons per minute for every ton of geothermal capacity. Most houses use three to six tons of geothermal, so a well that can produce somewhere in the 6-18gpm range can be used without needing to drill any additional wells. Of course, you also need to have a place to discharge the used water, so not all sites are suitable for open systems (if you have downhill neighbors, they probably won't like you dumping the water on the ground, to run down and flood their basement).
Geothermal is, in most cases, more expensive that traditional. Almost anything "alternative" is going to be. If it were not more expensive, it would not likely be "alternative" at all. Fossil fuels are the norm because the equipment is cheap, and the fuel has been cheap for a long time.
Realistically, installed geothermal in NH costs somewhere between $6k and $10k per ton, for most cases, depending upon the specifics of the project. Given typical residential sizing, that yields a $18k to $60k range. Operating costs are very low, so the price difference can be paid off pretty quickly, in most cases. Most geothermal installations will see operating costs in the hundreds of dollars, rather than in the thousands (like is the case with most fossil fuel systems). There are also rebates from PSNH and other power companies, since they want you to buy their power rather than someone else's oil.
Of course, there is the disadvantage that geothermal is strictly a grid-tied system. You would need a ridiculously-large generator to power a geothermal system in an emergency. Most installations get a separate electric service with their own meter, due to the power demands, and because PSNH will often charge a lower rate for the geothermal power. So, if your goal is to be off-grid, geothermal may be a bad choice.
What it all boils down to is that there is a huge range of options in heating, both in the conventional and alternative markets, and there's no one right answer for all applications. Some folks will be best off with oil. Others will be very pleased with wood-fired heating. Some will love their geothermal. And still others will beg used fry oil from the local restaurants, and heat their houses using that.
Joe
Author
Topic: Costs for Geothermal? (Read 3392 times)