GEOTHERMAL -Let your back yard heat your home!
Okay, it's a little more complicated than that, but our company wants to take a little of your time to educate you about utilizing ground source heat working with an exchange unit to heat your home or building.
We want you to feel that you can make an educated decision about whether this environmentally preferred option is the way for you to go or not.
This technology is not going to work for everyone, in fact, if your existing home has base board hot water as the heating distribution, this is not a viable replacement source for you unless you choose to retro-fit your project with either forced air or hydronic (radiant) as your dispersion choice. Base board water and under floor radiant require 160° to 180° F water/liquid running through them to create convection or heat the sub-floor layers to heat the room.
The two forms of heat dispersion that are excellent sources of heating with this technology each have their benefits. Forced Air is going to allow easy and relatively quick heat increases; during the summer months, the system is already outfitted to offer you Air Conditioning without needing any further equipment.
Hydronic (Radiant) floor heating with in-slab, thin pour vermiculite or over floor tubing is a phenomenal way to heat your project. The beauty of this form is that it is a steady heat source which when the power goes out, can take several days to cool down. The down sides are that if there is power (heat)loss, it takes a few days to come back up to temperature and that you cannot enjoy air conditioned cooling with the same ease of 1 system as with the Forced Air systems. With this option, for cooling you would need to install air handlers to obtain the same result.
More importantly, let's get you educated as to how we harvest this "heat fuel" at very little cost to you compared with conventional fossil fuels:
These systems absorb the warmth of the earth starting at 6 ft below ground that is heated by the sun's rays day in-day out every year. A system is designed using an "Open Loop" or "Closed Loop" design to transfer that temperature to either your drinking water or a food grade anti-freeze mixture, which is then pumped into your basement and run through a heat exchange unit. This unit utilizes a very low boiling temperature refrigerant which only requires a 4° F change to make it boil (becomes a gas). A compressor then forces the gas back to a liquid, and in the compression action, a reaction occurrs that creates 160° F.
With the heat exchange of this event, you will never be able to utilize the full 160 degrees; however, when the temperature is converted to Forced Air we have a maximum of 140° F working temp and with Hydronic we have a maximum 125° F working temp. Most radiant floor heat systems run the fluid at 80°-110° F.
The engineers that we work with design the systems to have a target thermostat setting of 72°, so it is very important to consider if you like your setting warmer or cooler than that as well as the temperature information of your site.
The following are examples of how we harvest the ground temperature:
Closed Loop Field -Horizontal
This design calls for burying a series of pipes filled with glycol in a series of individual or one large open trench (depending upon opportunity or soil structure).
Closed Loop Field -Vertical
This design calls for drilling a series of vertical wells which hold the loop field pipe and are filled with a thermally enhanced grout. This application is excellent when the lot is space or soil challenged; however, it is the most expensive option due to the cost to drill and grout.
Closed Loop Field -Pond
This design is the least common option as most homeowners do not have a pond in their landscape design. If you are planning on creating a pond and utilizing this option, the number of loop field coils will need to sit 12 ft below the water table level of the pond. This option is not available for Waters of the State (Public Water Domains).
Open Loop Field -Drilled Well, Other Discharge
This design has a lot of potential for projects with domestic well yield sufficient for potable use and heat pump use, however, due to the design "dump" to another site for discharge, you are required by the State of Vermont to apply for a UIC 318 Underground Injection Well Permit before you start your project. This permit has a fee and a waiting process, and will ascertain the erosion and influence properties of the design. Basically, it is considered that you are introducing (some amount) of water (of varying qualities) into a location where it was not naturally.
Open Loop Field -Standing Column
Standing-column wells are feasible in areas with fractured bedrock aquifers near the surface, which is the case throughout much of the New England region, where depth to bedrock typically ranges from 2 to 50 feet, and where the underlying rock formations are deeply fractured. Standing column wells are installed by drilling uncased boreholes, typically 6 inches in diameter, to depths in the range of 500 to 1,500 feet. The uncased borehole is in direct contact with the surrounding aquifer, creating a standing column of water from the top of the groundwater table down to the bottom of the well.
As shown above, water for the GHP system is drawn from the bottom part of the well and returned at the top, with no net withdrawal of groundwater. During periods of peak heating and cooling demand, however, the system can "bleed" or discharge a portion of the return water at the surface (to a river, lake, pond, or drainage field) rather than returning it all to the standing column. Such surface bleeding causes net groundwater inflow to the column from the surrounding rock formation. This chills the standing column during periods of peak heat rejection (when building demand for cooling is greatest) and/or warms it during peak heat extraction (when heating demand is greatest), thus reducing the required bore depth.
Properly sited and designed, standing-column wells can be significantly less expensive to install than closed-loop GHP systems. They also require the least amount of ground area of any GHP system and should be considered for urban settings where land availability is limited, provided that proper geologic conditions exist.
Advantages: Simpler design; lower drilling costs than for vertical closed-loop systems; more efficient performance by avoiding thermal degradation associated with heat transfer across pipe wall from ground or water body to antifreeze solution in closed-loop; lower installation cost if a supply well already exists for domestic water or grounds irrigation, with sufficient surplus production capacity to supply heat pump system.
Disadvantages: Subject to local, state, and Federal groundwater and surface water withdrawal and discharge permitting; large water flow requirements may exceed local water availability; supply-side of heat exchangers subject to corrosive and abrasive agents, chemical scaling, and microbial fouling; main circulating pumps typically require more power in open loops than in closed loops; water discharge regulations may preclude single-well systems or constrain the design of standing-column systems; higher installation cost if a separate injection well is required for loop water discharge.
Any new construction would be remiss in not considering this option to heat and cool with.