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Engineer's Desk: Geothermal Systems Installations expanding rapidly
Geothermal Heating and Cooling Systems are gaining wide acceptance across North America and the technology is taking its rightful place in both the HVAC and Hydronic markets. Significant increases in sales over the past few years estimated at over 20 percent per year are indicative of the widespread acceptance of this now proven technology.
There are several driving forces contributing to the significant growth of the technology. While energy savings and simple payback can be realized in a reasonable period of time due to rising energy costs, the green factor is fast becoming one of the primary reasons for the significant growth that the industry is experiencing. Consumers across the country have accepted global warming as a reality and are becoming more aware of available green technologies.
Savvy developers and builders are seeing the value in building more efficient and environmentally friendly buildings that will give them a market advantage and raise the profile of their companies as good corporate citizens.
Other driving forces include utility companies and developers financing and retaining the ownership of the ground heat exchangers and then leasing the heat exchangers to the end users. The reduction in capital cost to the builder, developer and ultimately the end user makes these systems more affordable and appealing.
How they work
Geothermal systems have the unique ability to transfer energy between the ground and a building in either direction through a network of plastic piping that can be buried vertically or horizontally. The pipe material used is high density polyethylene made of a specific resin and cellular classification and is heat fused using either socket fusion or butt fusion methods.
Typical vertical installations would be drilled to a depth of 200 to 300 while horizontal installations would see the pipe buried as shallow as five to six feet depending on the geographical region for the installation and soil conditions.
The ground heat exchanger is filled with water and mixed with an anti-freeze solution. A typical mixed ratio would be 20 to 25 percent antifreeze and 75 to 80 percent water. Typically methanol, ethanol or propylene glycol are used. The reason anti-freeze is required is that the heat pumps are capable of lowering the fluid temperatures below the freezing point for water. The ground temperatures are not low enough to freeze the water in the loop.
Ground temperatures are fairly constant on vertical loop systems. In the lower mainland, we expect to see an average ground temperature of approximately 52F (11C). In order for a heat pump to extract some of that energy, the heat pump must chill the fluid in the loop to create a difference in temperature. The greater the difference in temperature between the solution in the loop and the soil, the more energy that can be transferred.
A typical geothermal design could see a ground loop operating at 32F (0C) entering water temperature at the heat pump towards the end of the heating season. The entering water temperatures can be higher or lower depending on the design of the ground heat exchanger. The designer can design a ground loop to target a specific entering water temperature.
The big difference between a water source heat pump and a ground source heat pump is the operating range. Water source units typically operate with water temperatures of 60 to 90F (15-22C) and are coupled to a boiler and cooling tower; geothermal heat pumps operating ranges are typically from 25 to 100F (-3 to 38C). They are therefore called extended range heat pumps.
Innovations - What's new?
Geothermal heat pumps are relatively simple appliances that consist of an evaporator, a condenser, a compressor and a contactor. Typical safety devices would be low and high pressure switches on the refrigerant system. There are still manufacturers out there who use electro-mechanical controls in an effort to remain competitive in the multi-family and commercial markets. Some manufacturers have gone to circuit boards and LEDs to help technicians troubleshoot the equipment by letting them know that a safety device such as a pressure switch has opened. While geothermal manufacturers can build quality into their units, they have little or no control over the installation of the equipment and the conditions they may be subjected to.
Unfortunately for many manufactures, the safety devices used in their equipment offers "too little too late" protection. In other words, by the time the safety devices have tripped the damage is done. The biggest area for improvement is on the controls side of the equipment. One manufacturer, TILI Science Technic Co. has recognized this problem and developed a control system to improve the reliability and durability of its equipment. Their system uses an on-board micro-computer that has the ability to calculate and evaluate all of the operating parameters of the heat pump. It will monitor entering and leaving water temperatures and calculate the . The unit also looks at refrigerant temperature, coil frosting and entering air temperature. Because of its ability to calculate, the self diagnostics of the system can identify problems such as low water flow conditions, excessive water flow conditions, loss of refrigerant, laminar flow conditions in a ground loop, incorrect water connections to the unit and many other conditions. All of the diagnostics are displayed on the thermostat. The heat pump is designed to protect itself from both internal and external problems.
As the market continues to develop, we are seeing manufacturers continually improving their products and finding innovative ways to capture energy for many applications. The technology is existing, fast growing and here to stay.
There are several driving forces contributing to the significant growth of the technology. While energy savings and simple payback can be realized in a reasonable period of time due to rising energy costs, the green factor is fast becoming one of the primary reasons for the significant growth that the industry is experiencing. Consumers across the country have accepted global warming as a reality and are becoming more aware of available green technologies.
Savvy developers and builders are seeing the value in building more efficient and environmentally friendly buildings that will give them a market advantage and raise the profile of their companies as good corporate citizens.
Other driving forces include utility companies and developers financing and retaining the ownership of the ground heat exchangers and then leasing the heat exchangers to the end users. The reduction in capital cost to the builder, developer and ultimately the end user makes these systems more affordable and appealing.
How they work
Geothermal systems have the unique ability to transfer energy between the ground and a building in either direction through a network of plastic piping that can be buried vertically or horizontally. The pipe material used is high density polyethylene made of a specific resin and cellular classification and is heat fused using either socket fusion or butt fusion methods.
Typical vertical installations would be drilled to a depth of 200 to 300 while horizontal installations would see the pipe buried as shallow as five to six feet depending on the geographical region for the installation and soil conditions.
The ground heat exchanger is filled with water and mixed with an anti-freeze solution. A typical mixed ratio would be 20 to 25 percent antifreeze and 75 to 80 percent water. Typically methanol, ethanol or propylene glycol are used. The reason anti-freeze is required is that the heat pumps are capable of lowering the fluid temperatures below the freezing point for water. The ground temperatures are not low enough to freeze the water in the loop.
Ground temperatures are fairly constant on vertical loop systems. In the lower mainland, we expect to see an average ground temperature of approximately 52F (11C). In order for a heat pump to extract some of that energy, the heat pump must chill the fluid in the loop to create a difference in temperature. The greater the difference in temperature between the solution in the loop and the soil, the more energy that can be transferred.
A typical geothermal design could see a ground loop operating at 32F (0C) entering water temperature at the heat pump towards the end of the heating season. The entering water temperatures can be higher or lower depending on the design of the ground heat exchanger. The designer can design a ground loop to target a specific entering water temperature.
The big difference between a water source heat pump and a ground source heat pump is the operating range. Water source units typically operate with water temperatures of 60 to 90F (15-22C) and are coupled to a boiler and cooling tower; geothermal heat pumps operating ranges are typically from 25 to 100F (-3 to 38C). They are therefore called extended range heat pumps.
Innovations - What's new?
Geothermal heat pumps are relatively simple appliances that consist of an evaporator, a condenser, a compressor and a contactor. Typical safety devices would be low and high pressure switches on the refrigerant system. There are still manufacturers out there who use electro-mechanical controls in an effort to remain competitive in the multi-family and commercial markets. Some manufacturers have gone to circuit boards and LEDs to help technicians troubleshoot the equipment by letting them know that a safety device such as a pressure switch has opened. While geothermal manufacturers can build quality into their units, they have little or no control over the installation of the equipment and the conditions they may be subjected to.
Unfortunately for many manufactures, the safety devices used in their equipment offers "too little too late" protection. In other words, by the time the safety devices have tripped the damage is done. The biggest area for improvement is on the controls side of the equipment. One manufacturer, TILI Science Technic Co. has recognized this problem and developed a control system to improve the reliability and durability of its equipment. Their system uses an on-board micro-computer that has the ability to calculate and evaluate all of the operating parameters of the heat pump. It will monitor entering and leaving water temperatures and calculate the . The unit also looks at refrigerant temperature, coil frosting and entering air temperature. Because of its ability to calculate, the self diagnostics of the system can identify problems such as low water flow conditions, excessive water flow conditions, loss of refrigerant, laminar flow conditions in a ground loop, incorrect water connections to the unit and many other conditions. All of the diagnostics are displayed on the thermostat. The heat pump is designed to protect itself from both internal and external problems.
As the market continues to develop, we are seeing manufacturers continually improving their products and finding innovative ways to capture energy for many applications. The technology is existing, fast growing and here to stay.
Point One Media inc.