How Does Geothermal Energy Help The Environment – Illustration of a geothermal heating and cooling system that handles multiple loads for a community. Illustration by Sarah Cheney.

Imagine a home where the temperature is always comfortable, but the heating and cooling system is out of sight. That system works efficiently but does not require extensive maintenance or knowledge on the part of the owners.

How Does Geothermal Energy Help The Environment

The air smells fresh; You can hear the birds singing and the wind rustling lazily through the trees. The home shares energy with the earth similar to the way tree roots exchange the essential elements of life with their leaves and branches. Sounds comfortable, right?

Geothermal Energy Information And Facts

Geothermal heating and cooling makes that vision a reality. Geothermal heating (heating, ventilation and air conditioning) brings a building into harmony with the earth below, taking advantage of underground temperatures to provide heating in the winter and cooling in the summer.

Outdoor temperatures fluctuate with the change of seasons, but underground temperatures do not change as drastically thanks to the insulating properties of the earth. Four to six feet underground, temperatures remain relatively constant year-round. A geothermal system, which typically consists of an indoor drive unit and a buried system of piping, called a ground loop, and/or a pump for the reinjection well, takes advantage of these constant temperatures to provide “free” energy.

(Note that geothermal cooling should not be confused with “geothermal energy,” the process by which electricity is generated directly from the heat inside the earth. This is carried out on a utility scale and uses different processes, usually by heating water until it boils. )

The pipes that make up a ground loop are usually made of polyethylene and can be buried underground horizontally or vertically, depending on the characteristics of the site. If an aquifer is available, engineers may prefer to design an “open loop” system, in which a well is drilled into the groundwater. The water is pumped, passes through a heat exchanger, and then returned to the same aquifer through “reinjection.”

Why Geothermal Energy Is Being Viewed As A Viable Alternative To Fossil Fuels

In winter, fluid circulating through the system’s ground loop or well absorbs stored heat from the ground and transports it indoors. The indoor unit compresses the heat to a higher temperature and distributes it throughout the building, like an air conditioner running in reverse. In the summer, the geothermal HVAC system extracts heat from the building and transports it through the ground/pump loop to the reinjection well, where it deposits the heat into the cooler ground/aquifer.

Unlike ordinary heating and cooling systems, geothermal HVAC systems do not burn fossil fuels to generate heat; They simply transfer heat to and from the earth. Typically, electrical power is used only to run the unit’s fan, compressor, and pump.

A geothermal heating and cooling system has three main components: the heat pump unit, the liquid heat exchange medium (open or closed loop), and the air supply system (ducts) and/or radiant heating (in the ground or elsewhere).

Geothermal heat pumps, as well as all other types of heat pumps, have efficiencies rated by their coefficient of performance or COP. It is a scientific way of determining how much energy the system moves versus how much it uses. Most geothermal heat pump systems have COPs of 3.0 to 5.0. This means that for every unit of energy used to power the system, three to five units are supplied as heat.

Geothermal Energy: Promising, Massive, And Vastly Underutilized

Geothermal systems require little maintenance. When installed correctly, which is essential, the buried circuit can last for generations. The unit’s fan, compressor and pump are housed inside, protected from harsh weather conditions, so they tend to last for many years, often decades. Typically, the only maintenance required is periodic filter checks and changes and annual coil cleaning.

They work with nature, not against it, and do not emit greenhouse gases. (As mentioned above, they use a smaller amount of electricity to operate, because they are coupled with the Earth’s average temperature.)

Geothermal HVAC systems are becoming common features of green homes as part of the growing green building movement. Green projects accounted for 20 percent of all new construction homes in the United States last year. By 2016, a Wall Street Journal article predicted that green housing will grow from $36 billion a year to $114 billion. This is close to 30 or 40 percent of the entire real estate market.

But much of the information out there about geothermal heating and cooling is based on outdated information or outright myths. In our new book Modern Geothermal HVAC Engineering and Control Applications (Egg/Cunniff/Orio -McGraw-Hill 2013), co-authors Greg Cunniff, Carl Orio, and I debunk many of these myths.

Unlocking The Deep Geothermal Energy Potential Of The Carboniferous Limestone Supergroup

Fact: Geothermal HVAC systems use just one unit of electricity to move up to five cooling or heating units from the ground to a building.

Fact: Geothermal HVAC systems remove four times more kilowatt-hours of consumption from the electric grid per dollar spent than photovoltaics and wind energy add to the electric grid. Those other technologies can certainly play an important role, but geothermal HVAC is often the most cost-effective way to reduce the environmental impact of conditioned spaces.

3. Geothermal HVAC requires a lot of garden or land to place the polyethylene pipe ground loops.

Fact: Depending on site characteristics, the ground loop may be buried vertically, meaning little above-ground surface area is needed. Or, if there is an aquifer available that can be tapped, only a few square feet of land is needed. Remember, the water returns to the aquifer from which it came after passing through a heat exchanger, so it is not “used” or negatively affected.

Geothermal Can Provide Half Our Energy

Fact: Ground loops can last for generations. Heat exchange equipment typically lasts for decades as it is protected indoors. When replacement is necessary, the expense is much less than installing a completely new geothermal system, since the loop or well is the most expensive to install. The new technical guidelines eliminate the problem of thermal retention in the soil, so heat can be exchanged with it indefinitely. In the past, some improperly sized systems overheated or overcooled the soil over time, to the point that the system no longer had enough temperature gradient to function.

Fact: They operate just as efficiently in cooling and can be designed to not require an additional backup heat source if desired, although some customers decide it is more cost effective to have a small backup system just for the coldest days if that means that your circuit can work. be smaller.

7. Geothermal HVAC systems cannot heat water, a pool, and a home at the same time. Fact: Systems can be designed to handle multiple loads simultaneously.

Fact: Geothermal systems don’t actually consume water. If an aquifer is used to exchange heat with the earth, all the water returns to that same aquifer. In the past, there were some “pump and dump” operations that wasted water after passing through the heat exchanger, but these are now extremely rare. When applied commercially, geothermal HVAC systems actually remove millions of gallons of water that would otherwise have evaporated in the cooling towers of traditional systems.

Geothermal Heating Pros And Cons: Is It Right For Your Home?

Fact: Federal and local incentives typically amount to between 30 and 60 percent of the total cost of the geothermal system, which can often make the initial price of a system competitive with that of conventional equipment. Standard air-source HVAC systems cost about $3,000 per ton of heating or cooling capacity during new construction (homes typically use between one and five tons). Geothermal HVAC systems cost around $5,000 per ton and can go up to $8,000 or $9,000 per ton. However, new installation practices are reducing costs, to the point that the price is approaching conventional systems under the right conditions.

Factors helping to reduce costs include economies of scale for community, commercial or even large residential applications and increasing competition for geothermal equipment (especially from major brands such as Bosch, Carrier and Trane). Open circuits, which use a pump and a reinjection well, are cheaper to install than closed circuits.

Thank you for the thousands of likes and hundreds of comments! National Geographic has closed comments for this blog. Continue the conversation and get the answers you need for geothermal heating and cooling on Jay Egg’s blog, “Geothermal Heating and Cooling Questions and Answers.”

Jay Egg is co-author of the new book Modern Geothermal HVAC Engineering and Control Applications (McGraw-Hill 2013), with Greg Cunniff and Carl Orio. He co-wrote the book Geothermal HVAC, Green Heating and Cooling in 2010 with Brian Clark Howard of National Geographic. Jay consults with the geothermal HVAC industry. He previously served as a technology installer through his company EggGeothermal.

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Geothermal Energy Benefits

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