Geoexchange heating and cooling will save you money, reduce your energy use and keep the environment cleaner for your family and your community.
It is the most cost-effective, energy efficient and environmentally friendly method of heating and cooling your home available today. It can reduce your utility bills by up to 70% today and for many years to come.
Geoexchange heating and cooling technology continues to gain momentum amid concerns over pollution, energy conservation and rising energy costs.
Our technology is proven, reliable and safe. It significantly reduces energy usage and utility bills for homeowners and business owners.
Below are some of the commonly asked questions about how Geoexchange systems work and how they can benefit you.
1. WHAT IS GEOEXCHANGE?
Firstly, geoexchange is not geothermal energy – at least it is not geothermal energy in terms of generating power from a volcano or ‘hot rocks’. Specialty geological conditions are not required as it is solar radiation that provides the constant and stable underground temperatures that form the basis of geoexchange systems. As such, geoexchange can be applied in most locations around the world, whereas geothermal energy is limited to specific locations.
How does a Geoexchange heating and cooling system work?
Outdoor temperatures fluctuate widely with the changing seasons but underground temperatures do not. Just 1.2 to 2.0 meters below the earth’s surface, temperatures remain relatively constant year-round. A geoexchange system, which typically consists of an indoor unit and a buried earth loop, capitalizes on these constant temperatures to provide “free” energy.
In winter, fluid circulating through the system’s earth loop absorbs stored heat and carries it to the indoor unit. The indoor unit compresses the heat to a higher temperature and distributes it throughout the building.
In summer, the system reverses, pulling heat from the building, carrying it through the earth loop and depositing it in the cooler earth.
What makes a Geoexchange system different from ordinary systems?
Unlike ordinary systems, geoexchange systems do not burn fossil fuel to generate heat; they simply transfer heat to and from the earth to provide a more efficient, affordable and environmentally friendly method of heating and cooling. Typically, electric power is used only to operate the unit’s fan, compressor and pump.
What are the components of a Geoexchange system?
The three main parts consist of the ground source or geothermal heat pump, the liquid heat-exchange medium (closed or open loop) and the heat delivery system (either air-delivery ductwork or water delivery such as a hydronic floor slab or radiators).
How efficient is a Geoexchange system?
A Geoexchange system is three to five times more efficient than the most efficient ordinary system. Geoexchange systems do not burn fossil fuels to make heat, they provide three to five units of energy for every one unit used to power the system.
Why do ground source heat pumps not have a “star” rating like air-to-air heat pumps?
The existing star scale is not extensive enough to include ground source heat pumps and in many instances, ground source heat pumps are beyond the existing scale for star rating of appliances.
What is a COP and what does it tell me about the efficiency?
The Coefficient of Performance (COP) is a ratio of the unit input (kW) over the unit output (kW) at specific operating conditions and hence is a measure of unit efficiency. It’s a scientific way of determining how much energy the system produces versus how much it uses.
For instance, a typical LPG furnace with an efficiency of 80 to 90 % will have a COP of 0.8 to 0.9. Most ground source heat pump systems have COPs of 4-11. That means for every one unit of energy used to power the system, up to 11 units are supplied as heat / cool.
Rated COPs for conventional systems are often different to that experienced in the home due to factors such as location of the unit in exposed areas, blocking of air filters, varying outdoor air temperature, defrost cycles etc.
One of the main benefits of a geoexchange system is that due to their internal and underground nature, they are less susceptible to these fluctuations and as such the annual average COP will only be slightly less than the certified COP.
Whereas, due to their reliance on outside temperatures, direct sun exposure etc, the COP of air-sourced systems can vary dramatically over the course of a year. The defrost cycle is one such example where an air sourced system is using energy to heat itself rather than your home.
Do Geoexchange systems require much maintenance?
Geoexchange systems are practically maintenance free. When installed properly, the buried loop will last for generations. And the other half of the operation – the unit’s fan, compressor and pump – is housed indoors, protected from the harsh weather conditions.
Usually, periodic checks and filter changes are the only required maintenance.
2. HOW DOES GEOEXCHANGE WORK?
Are all Ground Source Heat Pumps alike?
No. There are different kinds of ground source heat pumps designed for specific applications.
A ‘water to air’ ground source heat pump transfers heat from the water in the ground loop into the air in your home via a ducted delivery system.
A ‘water to water’ ground source heat pump transfers heat from the water in the ground loop into water in your home via a hydronic heating system. This unit can also be used for heating swimming pools.
How does a Ground Source Heat Pump work?
Heat pumps simply move heat from a low temperature source to a high temperature space for heating. Anyone with a refrigerator has witnessed the operation of a heat pump. Your refrigerator is a heat pump that removes heat from room temperature items you place in your fridge and rejects that heat to the outside. On older refrigerators, it was the black mesh or coil on the back of the fridge.
Now, pick up that black mesh and bury it in the ground. This is essentially how a ground source heat pump and ground loop operate. In cooling mode, a ground source heat pump extracts heat from your home and rejects it to the ground. In heating mode, a ground source heat pump extracts heat the ground and transfers it into your home.
An air source heat pump, for example, extracts heat from outdoor air and pumps it indoors.
A ground source heat pump works the same way, except that its heat source is the warmth of the earth. The process of elevating low temperature heat to over 38ºC and transferring it indoors involves a cycle of evaporation, compression, condensation and expansion. A refrigerant is used as the heat transfer medium which circulates within the heat pump. The cycle starts as the cold, liquid refrigerant passes through a heat exchanger (evaporator) and absorbs heat from the low-temperature source (fluid from the ground loop). The refrigerant evaporates into a gas as heat is absorbed.
The gaseous refrigerant then passes through a compressor where the refrigerant is pressurized, raising its temperature to more than 82 ºC. The hot gas then circulates through a refrigerant-to-air heat exchanger where heat is removed and pumped into the building at about 38 ºC. When it loses heat, the refrigerant changes back to a liquid which is then cooled as it passes through an expansion valve and begins the process again. To work as an air conditioner, the system’s flow is reversed.
For further explanation and details on ground source heat pumps, click here.
Does a Geoexchange system heat and cool?
Yes. A simple flick of a switch on your indoor thermostat will change from one mode to another. In the cooling mode, a ground source heat pump takes heat from indoors and transfers it to the cooler earth. In the heating mode, the process is reversed.
Can a Geoexchange system also heat my domestic water?
Yes. Ground source heat pumps can provide free preheating of your domestic hot water using an option called a desuperheater. This consists of a refrigerant to water heat exchanger installed at the discharge of the compressor. The hot gas at this point is in a ‘superheated’ condition and some of this heat can be transferred into the cooler water through the copper wall of the desuperheater heat exchanger. A small circulator then transfers this heated water into the storage tank of your domestic hot water service.
For a more detailed description of the use of geoexchange in producing domestic hot water, click here.
3. CHOOSING YOUR GEOEXCHANGE SYSTEM
Do I need separate earth loops for heating and cooling?
No. The same loop works for both. To switch heating to cooling, or vice versa, the flow of heat is simply reversed.
Does the underground pipe system really work?
The buried pipe, or earth loop, was an important technical advancement in heat pump technology. The idea of burying pipe in the ground to gather heat energy originated in the 1940s. New heat pump designs and more durable pipe materials have been combined to make Geoexchange systems the most efficient heating and cooling systems available.
What types of loops are available?
There are two main types: closed and open.
What is a closed loop system?
A closed loop system uses a continuous loop of buried polyethylene pipe. The pipe is connected to the indoor heat pump to form a sealed, underground loop through which water or an environmentally friendly antifreeze-and-water solution is circulated. A closed loop system constantly re-circulates its heat-transferring solution in pressurized pipe, unlike an open loop system that consumes water from a well.
Closed loops can be either horizontal or vertical or located within a water body (closed water loop). Land area, soil conditions and availability of a suitable water body will determine the most suitable and cost effective closed loop for your site.
What is the difference between horizontal and vertical closed loops?
Horizontal closed loops are installed when there is sufficient land area available and that soil depth permits excavation to an approximate depth of 1.5m. There can be multiple pipes within the trench and the total length of the trench is a function of the heating / cooling load.
Vertical closed loops are installed when land area or shallow rock does not permit the installation of a horizontal loop. The boreholes are drilled to depths from 50 to 120 m. The depth of the boreholes, the number of boreholes and their spacing is a function of the heating / cooling load.
How long will the loop pipe last?
Closed loop systems should be installed using only high-density polyethylene or polybutylene pipe. They have a chemical half life of ~250 years, are inert to chemicals normally found in soil and properly installed would be expected to last well beyond the life expectancy of your home. PVC or copper pipe should not be used.
How are the pipe sections of the loop joined?
Pipe sections are joined by thermal fusion. Thermal fusion involves heating the pipe connections and then fusing them together to form a join that’s stronger than the original pipe. This technique creates a secure connection to protect from leakage and contamination.
Will an earth loop affect my lawn or landscape?
No. Research has proven that loops have no adverse effect on grass, trees, or shrubs. There will initially be temporary bare areas, but they can easily be restored with grass seed or sod. Vertical loops require little space and result in minimal lawn damage.
I have a pond nearby. Can I put a loop in it?
Yes, if it’s deep enough and large enough. A minimum of 1.8 meters in depth at its lowest level during the year is needed for a pond to be considered as suitable. The surface area required depends on the heating and cooling load of the structure.
What is an open loop system?
An open loop system uses groundwater from an ordinary well as a heat source. The groundwater is pumped into the heat pump unit where heat is extracted and the water is disposed of in an environmentally safe manner. Because groundwater is a relatively constant temperature year-round, wells are an excellent heat source.
How much groundwater does an open loop system require?
The water requirement of a specific model is usually expressed in litres per second (l/s) and is listed in the unit’s specifications. Generally, the average system will use 0.07 l/s per kilowatt of capacity while operating. However, the exact volume of water required depends on the size of the unit and the manufacturer’s specifications. Your contractor should be able to provide this information.
Your well and pump combination should be large enough to supply the water needed by the heat pump in addition to your domestic water requirements. You probably will need to enlarge your pressure tank or modify your plumbing to supply adequate water to the heat pump.
What do I do with the discharge water?
There are a number of ways to dispose of water after it has passed through the heat pump.
The open discharge method is the easiest and least expensive. Open discharge simply involves releasing the water into a stream, river, lake, pond, ditch or drainage tile (if permitted in your local area). Obviously, one of these alternatives must be readily available and have the capacity to accept the amount of water used by the heat pump before open discharge is feasible.
A second means of water discharge is the return well. A return well is a second well that returns the water to the aquifer. A return well must have enough capacity to dispose of the water passed through the heat pump. A new return well should be installed by a qualified well driller. Likewise, a professional should test the capacity of an existing well before it is used as a return.
Are there any laws that apply to open loop installations?
All or part of the installation may be subject to local codes and licensing requirements. Check with local authorities to determine if any restrictions apply in your area.
Does an open loop system cause environmental damage?
No. They are pollution free. The heat pump merely removes or adds heat to the water. No pollutants are added. The only change in the water returned to the environment is a slight increase or decrease in temperature. Systems are designed to ensure this does not result in heating or cooling of the aquifer.
Can I reclaim heat from my septic system disposal field?
No. An earth loop may reach temperatures below freezing during extreme conditions and this may freeze your septic system. Such usage is banned in many areas.
What problems can be caused by poor water quality?
Poor water quality can cause serious problems in open loop systems. Your water should be tested for hardness, acidity and iron content before a heat pump is installed. Your contractor or equipment manufacturer can tell you what level of water is acceptable. Mineral deposits can build up inside the heat pump’s heat exchanger. Sometimes a periodic cleaning with a mild acid solution is all that’s needed to remove the build-up.
Impurities, particularly iron, can eventually clog a return well. If your water has high iron content, make sure that the discharge water is not aerated before it’s injected into a return well.
4. WHAT EVERY OWNER SHOULD KNOW
How do I know if the dealer and loop installers are qualified?
GeoExchange Australia staff and their certified Dealers are members of GAIN. They are qualified with both the International Ground Source Heat Pump Association (IGSHPA) and relevant manufacturers. Always check that your dealer is appropriately qualified.
Is a ground source heat pump difficult to install?
Most units are straight forward to install, particularly when they replace another forced-air or hydronics system. They can be installed in areas unsuitable for fossil fuel furnaces because there is no combustion, thus no need to vent exhaust gases. Ductwork must be installed in homes that don’t have an existing air distribution system. The difficulty of installing ductwork will vary and should be assessed by a contractor.
Another popular way to use ground source technology is with in-floor radiant heating, in which hot water circulating through pipes under the floor heats the room.
I have ductwork, but will it work with this system?
In all probability, yes. Your installing contractor should be able to determine ductwork requirements and any minor modifications, if needed. ducting associated with evaporative air conditioners is not suitable.
Do I need to increase the size of my electric service?
Ground source heat pumps don’t use large amounts of resistance heat and will use less than any other electrical system so your existing service is likely to be adequate. Generally, a 50-amp service will have enough capacity and smaller amp services may be large enough in some cases. This is dependent on the capacity of the ground source heat pump(s) being installed. Your electric utility or contractor can determine your service needs.
Is a Geoexchange system suitable for an off-grid home?
The answer to this question is a large maybe? Most off-grid homes will be highly energy efficient and as such should require only minimal heating and cooling. However, although highly efficient, the ground source heat pump is still powered by electricity and as such will increase your energy usage. A careful analysis should be made of the electrical requirements prior to committing to a Geoexchange system on an off grid home.
What is the Kilowatt size of the ground source heat pump that’s being proposed?
All heating systems are designed to provide specific amounts of heat energy per hour. The term “Kilowatt (kw)” refers to how much heat can be produced by the unit in an hour.
Before you can determine what size system you’ll need, you must have a heat loss/heat gain calculation done on the structure. From that, an accurate determination can be made of the size of the system you’ll need.
Most conventional systems are substantially oversized for heating requirements, resulting in increased operating cost and unpleasant temperature swings.
How long is the payback period for a Geoexchange system?
Payback periods are a function of the type of ground loop installed, the operating conditions and hours of the system and the alternative or conventional heating and cooling system. To figure this accurately, you must know how much you’ll save each year in energy costs with a ground source system as well as the price difference between it and an ordinary heating system and central air conditioner.
As an example: If you’ll save $2000 per year with a ground source system and the price difference is $10,000, your payback will be five years. If you install a ground source system in a new home, the monthly savings in operating costs generally will offset the additional monthly cost in the mortgage, resulting in an immediate positive cash flow.
“The system has been a hassle free and cost effective alternative. We carefully investigated all the alternatives before selecting this system and have been delighted with the efficiency and performance.”
Steve, Adelaide Hills
If you have further questions:
Contact us to discuss the potential for a Geoexchange system in your home. Our dealers are members of GAIN and are certified with both the International Ground Source Heat Pump Association (IGSHPA) and relevant manufacturers for both system design and installation.
A preliminary assessment of your building will require a copy of your building plans and a site plan, as well as information on construction materials, insulation and local soil and geological conditions.
We can provide you with a cost comparison using industry-leading software so that you can quickly see the benefits of installing a Geoexchange system.
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