The benefits of Ground Source Heat Pumps (GSHP) systems far outweigh the costs associated with them.
September 22, 2017 by Pete Prydybasz
There are three general means to install the source, each should be evaluated for the most economical means fitting the property; each can be modified to fit the situation; and each is dependent on the heat loss and gain of the building.
These means include:
- Ground water – out of a well
- Horizontally piped
- Vertically piped in the ground
All the options can be modified for the property. If you have enough water available on the property, and it is of good quality — not full of minerals and debris — and you have a method to discharge the borrowed water, it is the most efficient and probably the lowest cost of installation. There are a few variations of this concept such as standing column wells, that can also be investigated.
If the well is not a desired way to go, and you have a fair area of land available to you, you can opt for a horizontal loop constructed of high density polyethylene pipe (HDPE), heat welded together and buried. HDPE pipe is a plastic material chosen for good heat transfer and maintains its strength with a warranty of 50 years or more.
Horizontal installations depend on land area and type of soil. This usually is next in cost of installation. This type of loop is excavated as opposed to drilled. If the land area is restricted for a horizontal loop, then the other alternative is a vertical loop. The vertical method is the more expensive but uses the least area of the property.
It is most important to obtain an accurate heat loss and gain of the building, type and condition of the water and soil. A loop must gather the required BTUs for the building that reside in the temperature of the ground, the source. A loop is a direct result of the heat loss and gain of the building. The collected BTUs just need to be carried to the GSHP by the loop.
The installation of all loops should be designed by an experienced designer. If you do not know one, you can contact the International Ground Source Heat Pump Association (IGSHPA). This organization has set many standards for the installation of ground source heat pumps. IGSHPA also offers training and certifications for designers and trainers. You could also contact your local utility. I am sure one of them would be able to direct you to people in the know.
The equipment must be properly sized for application, comfort, longevity and efficiency. There are many software programs available to demonstrate how the equipment will perform in different sets of circumstances.
Installation practices are of the utmost importance with GHPs; there are no “rule of thumbs,” a loop must be figured. There are no constants in the lengths of the loop; pumps must be sized. You can’t just “throw one in.” The correct type and size of the pump and the correct loop length, all contribute to efficiency and life cycle of this type of installation. Knowing when you can use a central pump and when to use fractional horsepower circulators are all decided by an analysis of the system. None of this figuring is very difficult, and there are plenty of people to help you with this. The methods used to determine pump sizing and heat loss and gain, have been employed for similar processes and used for centuries. Boilers use water, move water and distribute heat. Water systems in a building bring fluids in and move them around the building. The difference being the requirements of the equipment. The collection of BTUs needs to satisfy the requirements of the building. The requirements must be met and are less forgiving than a boiler that usually was oversized and had more capacity than required.
The manufacturers of the equipment, IGSHPA, utilities and people like myself, offer all kinds of training easily accessible for the contractor to be able to garner the skills needed to build and install a GSHP system. A properly installed system will offer a trouble-free, economical and comfortable life of 20 years and up.
Fluid-based heat pump applications
There is an application for fluid-based heat pumps, called water source heat pumps (WSHP), from which GSHPs were derived. A WSHP was developed when buildings grew so tall that the climate inside the buildings varied and needed to be individually controlled. Their use grew as cities grew up with skyscrapers. In this application, there is a water tower on the building that would reject the heat that was moved from cooled spaces, and a boiler to heat the water when different spaces needed heat. This could occur simultaneously.
With incrementally sized and controlled WSHPs, we had the ability to accurately operate the climate of the building. The equipment used in these buildings has changed over the years to adapt to indoor air quality and efficiency standards. Boilers, chillers are used to maintain fluid temperatures and the water tower method of rejecting heat is still widely used. A water tower has a few drawbacks, which includes the amount and the quality of the fluid used to reject the temperatures created by heating and cooling. Other drawbacks include the risk of health hazards such as Legionnaires virus and shortages of water. To reduce the water usage of a water tower, loops are now being used to reject some of the heat, thereby reducing the size of the water tower and greatly reducing the amount of water needed to operate the tower. A sealed loop system is not subject to a constantly replenished water supply or harsh weather conditions or violent storms. The use of loops to assist a water tower, controlling the use and quality of water is called a Hybrid loop. Here the installation of a GHP has improved the system it was derived from. A GHP absorbs and rejects heat into its loop.
Many new buildings such as collages and hospitals are exploring and installing the use of Hybrid systems because of the availability, quality and the expense of maintaining a water system.
Bottom line is GHP systems are the most efficient comfort system available today. They are not the most expensive systems — rebated or not. They can be installed in almost any situation. They benefit everyone who is involved with them, including:
- A homeowner or building owner with the lowest operating cost, clean non-scorched air, easily maintaining good levels of humidity, increasing indoor air quality.
- The utility by offering a steady predictable usage of electric
- The environment by not burning fossil fuel
- The installation of one system equates to planting 1 acre of trees or removing two vehicles off the road
As a contractor or an engineer, you would be remiss not to be ready to discuss geothermal systems with your customers. GHSPs have been used for more than 40 years, and we know they work. Change is good — difficult — but good. We should accept it and step up. For you in your trade to accept this technology and embrace it, would put you in the forefront of your competitors.
Original Arctle: High Performing Building Magazine: https://www.phcppros.com/articles/6072-lets-talk-geothermal
The TLJ Team