DIY: Help me choose

Discussion in 'Geothermal Loops' started by DavTN, Dec 3, 2011.

  1. DavTN

    DavTN New Member

    New to this forum and wow, tons of great information. Thanks to all of you for the free education.

    Basic question is pond vs. ground?

    Based on previous posts I will include some details, but please let me know if I have left anything out.

    I recently purchased ~150 acre tract that I will be transforming into a mini-farm/ranch. I am only in learning and design phase and will be doing most of the work myself (have access to an excavator and dozier).

    I will be digging a large pond about 150-200' from the main house. The pond will be multi-use, including fishing.

    The house will be powered mostly by micro-hydro from a small stream and supplemented with PV as it would cost too much to hook up to the electric co. Obviously need to make electric and dollar wise decisions.

    I'm sure I can figure some protection from hooks if I go the pond route.

    Lastly, hydro-power cannot be turned off like PV (not as easy anyways) so it utilizes a dump load which in my case will be an water heater in a 550 gallon tank. Any ideas how take advantage of that energy?

    Thanks in advance,
  2. Blake Clark

    Blake Clark Member

    Hmm, I wonder why no one wanted to respond :eek:

    I'd say you've got some bigger fish to fry with this situation than pond vs ground. Designing and paying for an off-grid electrical system that can power a geo-thermal unit is pretty daunting.

    My first instinct is that if you think you've got enough power to run geo and are still anticipating needing a sizable dump load, make life easy on yourself and heat with the dump load. Super insulate and you could easily get by with 2 to 3 kW continuous heat input. If the electric is free and you've got enough of it, why go through the expense and hassle of of geo and the up-sized inverters/batteries you're going to need to run it?

    Keep in mind that provided you're using electric in the home (as opposed to your shop, etc) that lighting and appliance loads also contribute to heating the house. So, if your microhydro unit produces 3kW (which I'm assuming it must if you're considering geo) I'd say you're in pretty good shape with a well insulated house.
    Last edited: Dec 5, 2011
  3. DavTN

    DavTN New Member

    Thanks for the reply. I will look into heating with the dump load although I doubt it would get warm enough in the winter. The load basically acts as a governor to maintain consistent power/frequency with fluctuating water pressure.

    The site and design should generate around 6KWh in the spring and fall, but less in the summer and winter. The hydro is designed and contracted, but I will be running the house, shop, various pumps (when too far for ram pumps), tools, etc. So I will still need to be frugal.

    Property has an old house, but plan to demo and build a one story with an oversized basement. ~3,500 sq ft but only 1,000 upstairs. And I will insulate very well.

    Anyways, I like to research all possibilities and may not decide to do geo, but in my situation which would be more efficient/effective especially with regards to cooling the house? It gets pretty hot and humid in TN.

    Thanks again,
  4. Blake Clark

    Blake Clark Member

    So, just to make sure you don't mean 6kWh, you mean 6kW continuous, which would make for 144 kWh per day?

    Trust me, you can heat your house with electric resistance on 144 kWh per day using the dump load. If you bank your hot water with some big solar storage tanks you can easily draw off that thermal storage during the coldest nights. Or, alternatively, just run some heating cable in your slab. The thermal flywheel will average out the loads. As far as reduction in flow during the winter, you'll need to consult with your contractor to try to nail those numbers down - you'd need to know this if you were running geo as well.

    From your post, it's not clear to me if you're running a regulated AC hydro or a hybrid AC with DC battery/inverter setup. If you're running a regulated AC hydro and trying to integrate solar, that could get interesting. With a regulated AC hydro, only a portion of the dump load needs to be variable (maybe 500W) to maintain frequency. The other 4500 watts can be switched loads, like pumps. If you need to pump water, get yourself a big tank at the top of the hill and a good load management system to pump when you got extra power and your house is warm (or cool).

    If you're banking energy with a battery/inverter system, you're going to have more power than you know what to do. Granted, I've never metered a ranch before, but with conservation you can easily run a household and shop with around 750 watt hydro output. (Albeit without much too much heat to dump).

    As for air conditioning, geo for a well insulated house with 1000 square feet above grade is probably overkill. The smallest units are around 2 tons cooling. You'd have to do a heat gain analysis, but my guess is you could get by with less. My vote would be for a high efficiency wall mount splits. You can tailor your cooling needs room by room, with the ability to really reduce your running watts if you had to by only cooling the bedroom at night. Not quite as efficient as geo (the good ones come close), but more flexible.

    And since you could use a load management system to switch them on and off, they could operate as room-by-room heat pumps as well. Add a small would stove for when the system goes down at 2 am during a blizzard and you're all set :)
    Last edited: Dec 6, 2011
  5. DavTN

    DavTN New Member

    Yes, sorry continuous. Thank you this is what I was looking for and had planned on a wood stove but did not think the splits would be nearly efficient as geo, I will look into that and the solar storage tanks. A farm consumes a lot of fuel (usually PTO driven pumps and generator) so I am trying to run as much as I can from hydro and solar instead of diesel.

    Thanks again and if anyone has any ideas, geo, energy storage, etc. I'm making the switch from cubicle to farm so I'm all ears.

  6. Blake Clark

    Blake Clark Member

    I just edited my last post while you were typing with a few more details / questions.
  7. Mark Custis

    Mark Custis Not soon. Industry Professional Forum Leader


    Solar thermal.

    If you need help doing that let me know.


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