Re: Re: Heating systems | <– Date –> <– Thread –> |
From: Roger Diggle (digglemacline.com) | |
Date: Thu, 13 Oct 94 23:42 CDT |
Ground-source heat pumps are not really new technology, but young enough technology that only in the last 5 years or so have they become reliable enough to be a viable choice. The typical Ground-source heat pump contains a compressor, a refrigerant/air heat exchange coil, a refrigerant/water heat exchange coil, and a "reversing valve," which makes the refrigerant flow one direction to move heat from the water to the air (heating mode), and the other direction to move heat from the air to the water (cooling mode). There are also some other types of equipment that may be appropriate, but I'll take that up later. The typical installation includes a heat exchanger made of plastic pipe and buried underground to extract heat from the soil or to put it back there. If a large enough pond or river is available, the heat exchanger can also be submerged in the water. A pump moves water through the ground-souce heat exchanger, then through the water/refrigerant heat exchanger where heat is added or removed, finally back to the ground-source heat exchanger where the water is brought back to ground temperature. The size and geology of your site can make a big difference in the feasibility of an installation because of varying ground-source heat exchanger costs. Sometimes a large enough heat exchanger can be installed on a small site by boring holes and installing long U-tubes in the holes. (Older installations sometimes used lake, river, or ground water directly, without using a heat exchanger, pumping water out of a well, for instance, and returning it to the ground elsewhere with an injection well. I work regularly in a 28 unit apartment building that's set up this way. Many states now prohibit such installations, and there are other problems even where they are allowed. I would recommend against such an installation, even if it is available to you.) > Nancy Wight wight [at] world.std.com > New View Neighborhood Development Acton, MA > 1) If we install electric geothermal heat pumps, we will not be > having gas piped to our site, which means we have to use > electricity (where solar is not feasible) for heating water. Given > that gas is much cheaper than electricity, I'm wondering if we will > *really* see an overall energy savings. Although they are not common, water-to-water heat pumps are also available. Such a heat pump can be set up for heating a floor slab, for perimiter baseboard heating, and/or for heating domestic water. I don't believe you indicated whether you'd be air conditioning or not, but in NC it seems likely. Water-to-water units would preclude air conditioning in most cases, but consider it for domestic water heating. Therma-Stor Products of Madison, WI, also makes a line of heat pumped domestic water heaters in residential and commercial sizes. The typical unit extracts heat from the air and pumps it into the water, a particularly good system for restaurant (or co-housing?) kitchens which have a lot of waste heat in the air. McDonalds (gasp) was trying them out in their Madison restaurants, and was seriously thinking of using them nation-wide. They basically heat water for free if you have an air conditioning load. They have standard resistance electric elements for back-up. I see no reason why one of these units could not be operated as a water-source heat pump, but I can't tell you if that configuration is available ready-made. Therma-stor might be interested in a guinea pig, though. If you are in a position to experiment, there is a lot that could be done with heat pumps in conjuction with solar panels. A solar-assisted water-source heat pump (gad) could greatly increase the efficiency of your solar panels, and allow them to be used in lousier weather than with a standard installation. This technology has been talked about in engineering circles, and perhaps actually used somewhere, though I've never seen an actual installation. Modern computerized electronic controls make it more feasible, but that's starting to get pretty high-tech. It would be an expensive, custom installation. > 2) I'm worried about the "extreme weather", which we have a lot of. > Would we also have to have a furnace (and air-conditioning system) > for backup? If your installation is not troublesome, you will seldom need backup heat in NC, but I'd install it anyway, or be prepared with some portable electric heaters. The amount of backup heat use in a standard ground-source installation makes the choice of a gas furnace prohibitively expensive. In the apartment building I care for, the backup system is baseboard heaters with inexpensive integral thermostats. First cost is very low and it's very reliable. Most of the apartments only have one exposed cold wall, and we generally don't need back-up heat intil its 10f or lower outside, and then only on the north side of the building. However, the equipment does bust occasionally, and that's when the backup is a real blessing. If, as I suspect, you are going the forced air route and air conditioning with your heat pumps, there's one more product you might want to check into. Therma-stor makes a product that's a combination of heat recovery ventilator, water heater, and heat pump. It would replace kitchen and bath fans, the standard water heater, dehumidifier, and a small air conditioner. In heating mode, Therma-stor says that the unit recovers heat from the "stale" air stream and that the recovered heat can be used to heat the water and provide part of the space heat. It appears to be a well thought out product, but I have not seen one in operation. Roger Diggle diggle [at] macline.com Porchlight CoHousing, Madison, WI - via BulkRate 2.0 *********************************************************************** Mac Line BBS: (608) 233-9487 - A FirstClass System in Madison, WI USA **********************************************************************
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Heating systems Stephen Hawthorne, October 12 1994
- Re: Heating systems David Hungerford, October 12 1994
- Re: Heating systems Nancy E Wight, October 13 1994
- Re: Heating systems Daryl Anderson, October 13 1994
- Re: Re: Heating systems Roger Diggle, October 13 1994
- Re: Heating systems David Hungerford, October 14 1994
- Re: Heating systems David Hungerford, October 14 1994
- Re: Re: Heating systems Roger Diggle, October 14 1994
- Re: Heating systems Catherine McCarthy, October 16 1994
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