Farm Common Field System

Discussion in 'Vertical and Horizontal Loops' started by Honeydealer, Feb 6, 2011.

  1. Honeydealer

    Honeydealer New Member

    I am a Beekeeper and the owner of a Century farm in Saskatchewan. The existing house is heated by wood stove and plumbing is nonexistent. There is no well on site as all water was collected in a large cistern. In other words I am starting from scratch. What I do appreciate about the 100 year old farm is being self-sufficient and "off the grid".
    First I am building a 25'x50' heated shop with the potential to expand to another 25'x50'. I would like to use radiant floor heat.
    Next I intend to build a 2000-2500sq foot home and again use radiant floor heat with a wood stove or masonry heater as back up. All buildings will be slab on grade.
    Of course I would like to use the geothermal source to provide hot water both in the shop and in my home. I don't intend to install air conditioning or ducting of any sort.
    I envision a common loop horizontal field installation to service all three potential buildings. I have 720 acres at my disposal so long horizontal loops are not a problem. As I have my own excavating equipment, I intend to do the trenching and pipe installation myself, and then have a contractor install the heat pumps, tanks and controls.
    Most installations I have researched have had the pipe laid between 6 and 8 feet in depth. Is there any advantage to going to 10+ feet in depth? How many feet of pipe am I likely to use? How many/what size pumps will I use?
    Does anyone currently source or install geothermal systems that use solar power with battery backup for power?
    I'm sure I'll have many more questions and I appreciate all help in advance.
  2. Palace GeoThermal

    Palace GeoThermal Well-Known Member Industry Professional Forum Leader

    Yes, the deeper you go the less pipe you will need

    This will be determined by the Manual J heat load that you will calculate

    This will be determined by the Manual J heat load that you will calculate
  3. engineer

    engineer Well-Known Member Industry Professional Forum Leader

    As to the question of solar power for heat pumps...yes it can be done, but it takes a very robust PV system - big inverters and batteries. PV panels have come down a bit in price but you are still looking at $6-8 per installed Watt and thousands of Watts required
  4. urthbuoy

    urthbuoy Well-Known Member Industry Professional Forum Leader

    Pumps on a common loop field

    This is fairly common practice. We just did a design for an equivalent system to be installed in the spring.

    How much to put in does depend on your design as was mentioned. Have someone do this for you. It is not a shortcut you want to avoid as guessing sometimes works but never optimizes.

    Combining with solar PV, to be honest, can be done but is very rare. Load matching is very expensive and most of us have budgets.

    Also, you said all radiant but you do need to be aware of fresh air requirements for a house.
  5. Mark Custis

    Mark Custis Not soon. Industry Professional Forum Leader

    OK I am In also.

    The more pipe in the slab the lower the temperatures needed for in coming water to the radiant.

    Water does not care how it gets warm, so your inputs can be designed to your cash flow. I might take a hard look at solar thermal, as there are a lot of well engineered products available at fire sale prices.

    I would give up my cell phone to be able to KEEP Bees. I like to eat.

    I will deffer to the more northern of my freinds on the geo stuff, I live in a very warm near Lake Erie climate.

  6. Designer_Mike

    Designer_Mike Member

    I believe you have lots of math to do :D

    Solar PV panels are not terribly efficient> somewhere around 19% I believe.
    Solar water heating panels are much more efficient> something like 85-90% depending on temperature differentials.
    Just a straight comparison would say you need system COP above 4.5 to make the PV panels more efficient than the water heating panels.
    BUT that is just comparing the heating potential. You will still need electricity to run the rest of the place and during the low heating months, the water heating panels will do nothing for you while the PV panels would give you free cooling.

    Seasonally, water heating panels production will be worst in the winter. PV panels actually do better in the cold and all the reflection off the snow improves their yield... less daylight and lower sun angle are the enemy. My 10.12kW PV array had a peak power of 11.0 kW today.

    As Mark said, water doesn't care how it gets warm. An outdoor wood boiler can put an amazing amount of BTU into a tank of water in no-time with almost zero electric requirements.

    Careful design and backup system It gets chilly up there :D

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