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Information on future heating sources

Post in 'The Boiler Room - Wood Boilers and Furnaces' started by by_the_fireside, Sep 18, 2008.

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  1. BrownianHeatingTech

    BrownianHeatingTech Minister of Fire

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    Indeed. I'm done with this nonsense. Anyone who cares to do the models can see the results for themselves. Or they can trust the individual who says he hasn't modeled anything, but "just knows" that the model is wrong. Continuing a discussion with someone taking that position is pointless.

    Joe

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  2. BrownianHeatingTech

    BrownianHeatingTech Minister of Fire

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    On the subject of future heating sources, I figured some additional info on air-source and geothermal heat pumps might interest folks.

    We have a few basic ways to do heat pumps.

    The first is air-source. Very economical and works fine, except for the fact that falling air temperatures end up negating the ability of the heat pump to supply enough heat for the structure. As the temperature drops, the output of the heat pump drops, but the heat loss of the structure climbs. This can be partially mitigated by using multi-stage equipment, and even multiple systems in parallel. Very few systems can effectively/efficiently provide heat in below-zero weather, so we end up with a secondary heating system (resistive electric or fossil fuel, typically) that take over below a certain temperature. Some systems use an outdoor sensor to switch over at a certain temperature, while others use a multi-stage thermostat which "decides" when to switch over based upon the actual performance of the system. The latter technique is better, as it will automatically account for things like the difference in heat loss between a sunny day and a cloudy day.

    Aside from the thermal balance point (the point below which the heat pump simply cannot function effectively), there is also an economic balance point. That's the temperature below which the cost of running the heat pump crosses over the cost of running the backup system. When the backup is resistive heat, or at current oil prices, that's not likely to come into play, as it will almost always be below the thermal balance point. However, with a higher-efficiency backup system (eg, a condensing boiler tied to in-floor radiant heat), or if fuel prices are lower for the backup system then they are right now (eg, a wood boiler or waste-oil system, which uses low-cost or free fuel), then calculating that point can become important, because you may want to switch over at a temperature when the heatpump can still physically function, because of economic concerns. Calculating that point is a matter of the cost per kwh of electricity (heat pump) and the cost per kwh or btu of the backup system (including efficiency). Of course, there is always a bit of estimation involved, as fuel prices and electric prices are rarely stable. A professional heating company should provide that information at the yearly service, to help the customer know when to switch over for maximum savings.

    Because of their relative low cost, and lack of need for a chimney, air source heat pumps with resistive backup elements can be an excellent match for a wood boiler being tied into a forced-air system using a heat exchanger and air handler. The heat pump is operated for cooling in the summer, and to provide heat during the shoulder seasons (spring/fall). The electric resistive heater costs very little to purchase and provides backup during the winter if you leave home; as long as you do not leave for extended periods on a regular basis, the operating cost of the electric unit is negligible because it simply isn't used much. And the wood boiler is used during the winter to provide the primary heat source for the house. Adding A/C into the deal and having the option to heat efficiently in the spring and fall without firing the boiler can often improve the livability of the system, particularly in the case where one family member is more passionate about heating with wood than the other(s).
  3. Hansson

    Hansson Feeling the Heat

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    An air to Air heatpump can be good.
    I notice a test on swedish energy agency and they tested a Sanyo air heat pump in diffrent outside temps.
    This was the power output in the house and the outside temp
    7°C 5,5kW
    2°C 4,5kW
    -7°C 4,1kW
    -15°C 3,5kW
  4. BrownianHeatingTech

    BrownianHeatingTech Minister of Fire

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    Just as an air-source heat pump (be it a heat pump or an air conditioner or a refrigerator) pumps heat from the air against a temperature gradient using a refrigerant loop, a ground-source (geothermal) heat pump pumps heat from the ground using a similar principle. The obvious advantage is that once you get more than a few feet below the ground, the temperature becomes very stable, so you no longer have the issue of the air temperature dropping as the heat loss increases. The heat loss still increases as the temperature drops, but your heat pump is operating from a constant source temperature (50-55 degree soil), so the curves end up being much better. The method used to actually couple the heat pump to the ground source can vary. Some systems use refrigerant tubes buried directly into the soil; these are fairly rare, and I'm not really going to go into discussing that technology, as it really needs to prove itself more. More commonly, the heat pump passes refrigerant through one side of a coaxial or flat-plate heat exchanger, and water is passed through the other side. That water may be a closed system (often containing stabilizers and antifreeze) which runs through pipes buried in the ground, or it may be an open system, where water from a well or spring is used and then discarded.

    A closed system is less efficient, since the plastic pipe used for the loop(s) impedes heat transfer, and water which has been cooled by the removal of its heat is being returned to the source (albeit inside a pipe). Equipment must be de-rated to account for that (ie, a system rated for 60kbtuh output would only supply 48-54kbtuh), and the operating costs will tend to be a bit higher. However, such installations avoid issues of freezing the water (since anti-freeze can be added), and are not impacted by water quality.

    An open system is more efficient, since the heat is extracted from the water, and the cooled water is then discharged into a drain, allowing fresh, 50-55-degree water to be used for the incoming water. The quality of the water (hardness, mineral content, acidity, salinity) can be an issue in these systems, and (even if it checks out initially) should be checked on a yearly basis to protect the system from any detrimental changes over time. The ability of a well or spring to produce the necessary amount of water can also be a major hurdle. Many residential wells only produce 5gpm on a continuous basis. Geothermal systems need approximately 3gpm per ton, and most houses in this area would need a 5-10 ton system. That is an awful lot of water to be extracting from the ground, both in terms of the risk of running the well dry, and in terms of having to dispose of the water (your neighbors probably don't want it dumped on their lawn). A "dry well" or even a second drilled well in proximity to the first well can allow the water to be re-introduced into the local aquifer, but give it time to be re-heated by the earth. A well which does not produce enough can still be used, by discharging some or all of the water back into the well. This reduces efficiency to some extent (since already-cooled water is being re-introduced into the well), but generally not as much as with a closed system. Being able to supply domestic water at the same time as geothermal water may require the use of a cistern for the domestic water. The well pump fills the domestic cistern when the geothermal system is not operating, and a second pump draws water from the cistern and pressurizes it for use in the house.

    The well pump itself may not flow enough for geothermal, and may need to be upgraded. Variable-speed pumps are often a good idea in that case, as they will cycle less under the varying demands of the system, improving both efficiency and pump life. Standard pumps may require large pressure tanks to reduce short-cycling. Two-stage geothermal equipment can maximize efficiency by matching output more closely to the demands of the house, and reduce cycling issues as a result. A clean, reliable spring or pressure-producing well is obviously the best match for geothermal.

    As with an air-source heat pump, geothermal can be supplemented by resistive, fossil fuel, or other heat sources. This can be useful if the well cannot produce enough water to supply the full load, and space or cost constraints prevent the installation of a closed-loop system. In areas like the Northeast, where cooling loads are generally much smaller than heating loads, the geothermal system may be sized for the cooling load, allowing it to supplement the heating load, but not provide full heating of the structure. Similarly, older homes which are being upgraded may have a system sized for the future (ie, after the windows are replaced and the walls insulated better), and temporarily use backup heat to make up the difference until such time as those structure upgrades can be performed; that eliminated the initial cost and future maintenance issues of an oversized system.

    Thermodynamic efficiencies are obviously never more than 100%, but since you don't pay to heat the ground (the sun does that for you), the cost efficiency (electricity used versus energy delivered to the house) can be in excess of 500%. Factoring in the conversion from kwh to btu, and you can get performance factors in the 20-30 btu/kwh range. Of course, all that comes at a price. The equipment itself is expensive, and installation is often very expensive (particularly if a well needs to be drilled or upgraded). Some utility companies have loans, grants, or rebates for switching to heat pump systems, and may offer separate metering for the heating system (at a lower price per kwh), and those factors can offset the costs to a substantial extent. Only a full analysis of the system on a case-by-case basis can make the determination as to what geothermal will cost to install and to operate for a given structure.

    Obviously, if more homes switch to geothermal, open systems with open discharge may become a thing of the past, as the water table will not tolerate everyone drawing off many gallons per minute at the same time, and neither will the convenient places to discharge that water. The electric grid will also run into issues if too many homes are switched to electric-based heating systems. But these systems do offer an attractive alternative for many applications.

    Joe
  5. pybyr

    pybyr Minister of Fire

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    it would be really interesting if someone could develop a compressor, for both refrigeration and heat pump applications, that used the "linear motor" electronically commutated compressor--

    with no crank, bearings, or rotating parts-- like the Baxi Ecogen's magnetized piston surrounded by coils -- except in reverse as a motor in a compressor.

    I have to thnk you could take a pretty huge leap in compressor efficiency with a design like that, compared to rotating induction motors

    which would then make heat pumps, refrigerators, freezers, dehumidifiers, etc., all more electrically efficient- and probably quieter and more reliable.

    development costs would not be insignificant- but seems like the potential range and depth of applications could be huge
  6. BrownianHeatingTech

    BrownianHeatingTech Minister of Fire

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    I know a few tinkerers who've experimented with such things. There are a number of issues to be overcome. I think the biggest is seals that will survive the piston speed. Hard to compete with scroll compressors.

    Joe
  7. Redox

    Redox Minister of Fire

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    There was some research a few years back on a "sonic" compressor. It was supposed to use sound to achieve compression, with no moving parts other than the valves. This is an old document from Los Alamos that discusses it a little. Scroll down to page 9.

    http://www.fas.org/sgp/othergov/doe/lanl/pubs/00285648.pdf

    I do not recall seeing any more about it and I have no idea how efficient it was.

    If efficiency were really a concern, the US would allow use of hydrocarbon refrigerants. They are supposed to be significantly more efficient than current HFCs and the dangers can be minimized.

    Chris
  8. Hansson

    Hansson Feeling the Heat

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  9. pybyr

    pybyr Minister of Fire

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    I've always been told that some of the earliest refrigerators like the "monitor top" GEs used sulfur dioxide gas as a refrigerant. since a number of those are still functional, and I have never heard of anyone getting socrched by acid fumes from one that let go, I have to assume that it wasn't a catastrophic problem. I don't know whether SO2 is more or less efficient than HCFCs or hydrocarbons, but I have to think that they used it for a reason.

    Anyone know what Crosley used as refrigerant in the "Icy Ball" fridge if you know what that was (if you don't, google around some) ?

    speaking of refrigeration options, I was told by someone once that back in the days when electricity was not universal, and propane refrigerators were more widespread, that there were some that used water on the cooling side of the propane cooling equation. Anyone know if there is any validity to that? Anyone have any ideas on whether/ how it might be feasible to retrofit a water heat sink for a modern domestic fridge or upright freezer? I have a spring that runs all the time whether I am drawing from it or not, and is a lot cooler than household air...
  10. BrownianHeatingTech

    BrownianHeatingTech Minister of Fire

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    Ammonia, I believe.

    I think I have plans to build one around here, somewhere...

    Yes, it's possible. You can use a properly-sized plate heat exchanger to do it. Many are designed for refrigerant applications.

    Joe
  11. pybyr

    pybyr Minister of Fire

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    those of you want a MiniNuke, apparently someone is supposedly bringing it to market

    I have no idea of whether I think this is a good idea or a bad one- I would need to learn more. I do know that it would take the intervention of a deity to get a permit to install one in VT...

    begin quote from Electronix Express December 2008 newsletter (look them up at elexp.com- you need to subscribe to get their newsletter):

    1. A Micro Nuclear Reactor in Your Garden?
    Hyperion Power Generation, a U.S. company based in New Mexico, has designed mini nuclear plants to power 20,000 homes. The company has already received firm orders and expects to deliver about 4,000 individual plants between 2013 and 2023. It also said that it has a six-year waiting list. So if one wants such a micro nuclear reactor, don't expect to receive it by 2014. The HPM will have multiple applications. Some of them include industrial ones, such as oil shale and sands drilling and processing or powering U.S. Military facilities. But the one that would offer the most basic and direct positive impact on populations in need, is that of providing a power source to remote communities, both for electricity and to pump and process water.

    How much will such micro nuclear reactors cost? John Deal, the Hyperion CEO, says that such micro nuclear reactors should cost about $25 million each. In the U.S., where people spent more energy than in other parts of the world, such a reactor should be able to deliver power to only 10,000 households, for a cost of $2,500 per home. But in developing nations, one HPM could provide enough power for 60,000 homes or more, for a cost of less than $400. This is quite reasonable if you agree with Hyperion, which states that the energy from its HPMs will cost about 10 cents/watt. Hyperion power modules are about the size of a hot tub - approximately 1.5 meters wide. That means they are small enough to be transported on a ship, truck or train. Hyperion power modules are buried far underground and guarded by a security detail. Like a power battery, Hyperion modules have no moving parts to wear down, and are delivered factory sealed. Further, due to the unique, yet proven science upon which this new technology is based, it is impossible for the module to go supercritical, melt down or create any type of emergency situation. The waste produced after five years of operation is approximately the size of a softball and is a good candidate for fuel recycling."

    So, what do you think of a micro nuclear reactor buried inside your neighbor's lawn? Would you feel safe?
  12. BrownianHeatingTech

    BrownianHeatingTech Minister of Fire

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    I lived that close to a nuke for years. Was in the same building with it, countless times. Never bothered me.

    Joe
  13. Hydronics

    Hydronics Feeling the Heat

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    Regarding a previous post: correct, wood burning is carbon neutral, the issue with fossil fuels is that when used they release carbon that was stored many, many years ago, thus a net increase.
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