Introduction to Geothermal Heating for Industrial & Residential Use

In the previous article, “Everything you Need to Know About Geothermal Energy” we answered frequently asked questions about geothermal power, discussed its advantages & disadvantages, and shared several applications of G.E. for industrial and residential use. However, we did not delve into the details of geothermal heating, an ever-developing phenomenon that is taking over the private and public sector.

Power plant of geothermal energy in Iceland

Because the Earth’s heat is available in virtually any area of the globe, from the remote deep wells of Indonesia to your annoying neighbor’s backyard, geothermal energy represents one of the most reliable renewable heating sources. Furthermore, heat is constantly produced in the Earth’s core. As a matter of fact, the amount of heat within 10km of the Earth’s surface contains 50,000 times more energy than any fossil fuel in the world.

This sustainable alternative to traditional heating systems has been around for centuries, but in recent years technology advancements have made its application on a larger scale possible. In the following article, we will find out how geothermal heating works and discuss its applications in the industrial & residential sectors.

What is Geothermal Heating?

Wikipedia defines geothermal heating as the direct use of geothermal power to heat applications. As of 2007, 28 gigawatts of geothermal heating capacity has been installed around the world, satisfying approximately 0.07% of worldwide energy consumption. This may not sound like much, but due to new tax incentives and sustainability debates, more and more efficiency-minded home owners have started to consider geothermal cooling & heating systems for their houses.

Architects and designers are also recognizing the wisdom of their predecessors, who have used this century-old renewable resource to heat and cool homes and bath houses. According to the U.S. Department of Energy, geothermal heating systems are installed in over 50 thousands American homes each year.

“Many people think geothermal is a new technology, which makes builders and homeowners reluctant to it. Actually, it’s an idea that’s more than 150 years old.” Source: Jim Bose, executive director of IGSHPA

Geothermal heating systems are among the most energy-efficient and sustainable systems in the world. However, relatively high upfront costs are discouraging commercial building & home owners from installing it. The good news is that due to minimal maintenance and operating costs, these renewable resource systems – which operate at 50-70% efficiency- can pay for themselves in less than a decade.

As the documented history and research of geothermal heating costs, its technology will continue to develop too. Since this technology uses energy from the Earth’s constant temperature of 45-75 Fahrenheit, specialized systems can provide constant heating and cooling.

Salt Wells geothermal heating power plant

Image courtesy of the U.S. Department of Energy

The Pros & Cons of Geothermal Heating

If you’re thinking about installing a geothermal heating system in your home or commercial building, there are a few things that you need to consider. Let’s quickly weigh the advantages and disadvantages of the technology:

Geothermal Heating Pros

  • Geothermal heating systems are durable. The underground loops of geothermal systems are made from high-quality materials that protect them from elements that cannot be controlled such as vandalism or weather. What’s more, these loops also rank high in safety, as they do not use any fuel storage tanks, flammable fuel, or open flame. In order to prevent leaks, pipes are fusion-welded and guarantee a life expectancy of five decades.
  • Geothermal heating systems are quiet because they do not use any outside compressors. Ever wondered how a home in which the temperature is always comfortable, but no heating or cooling systems are visible? Try installing a geothermal heating system.
  • Geothermal heating is inexpensive to maintain and operate. GHPs require little to no maintenance service and promise superior reliability rating. Furthermore, GHPs use few mechanical operating components. Once a system is installed, it can work 50+ years without breaking down.
  • Geothermal heating will help you save precious space. In a world where wasted space is becoming a primary concern for sustainable-living advocates, geothermal heating systems represent a perfect solution. GHP (geothermal heating pump) systems do not require a mechanical room and are installed underground.
  • GHs are energy-efficient and eco-friendly because they do not rely on fossil fuels. The Department of Energy & the Environmental Protection Agency have granted GHPs high sustainability ratings.
  • Tax Relief. If your system meets or exceeds energy star requirements, you will receive a one-time 30% tax credit on a complete GHP system (including installation), through the American Recovery & Reinvestment Act. This credit expires in December 2016.

Geothermal Energy Cons

As is the case with most sustainable solutions, geothermal energy also has several cons that you should be aware of:

  • GHPs are extremely difficult to repair. In the eventuality that your system breaks down, the costs & efforts associated with repairing them will be high. That’s because GHPs operate with a system of underground pipes. However, a properly installed unit should not create any problems.
  • You will require a back-up heating system. In rural areas and extreme climates, geothermal heating doesn’t work at full capacity. Therefore, you will have to install another system or set-up an emergency back-up system.
  • High upfront costs. This is one of the primary reasons why geothermal heating systems haven’t become mainstream yet. The installation costs of GHPs can be significantly higher than those of conventional systems.

Wairakei geothermal power station, New Zealand.

What is a Geothermal Heat Pump?

A geothermal heat pump, commonly referred to as ground source heat pump (GSHP), represents a central heating and cooling system that transfers heat to or from the ground. During cold winter days, the earth is used as a heat source, and during summer, the earth becomes a heat sink (passive heat exchanger).

This system is wildly successful because it takes advantage of moderate temperatures that already exist in the earth to reduce operational costs of heating/cooling and to increase energy-efficiency. Advocates of sustainable living recommend combining geothermal heating systems with solar heating in order to form a geosolar system.

As the name suggests, a GHP system uses a heat pump to force transfer heat from the ground – by going against the natural direction of flow or by enhancing a natural flow of heat. Heat is moved through the core of the heat pump with the help of a loop of refrigerant that is pumped through a vapor-compression refrigeration cycle.

GHPs are much more efficient at heating than pure electric heaters because underground temperatures are more stable than air temperatures. The coefficient of performance of GHP system is high (3 to 6), in comparison to air-source heat pumps (1.75 to 2.5).

How Geothermal Heating Works

Thermal efficiency for geothermal heating systems is quite high because no energy conversion is required. Nevertheless, capacity factors are low (approximately 20 percent), because heat is generally used during winter.

Geothermal heat can be used in different ways, from complex power stations that provide energy to entire communities, to small and relatively simple heat pumping systems. But geothermal power isn’t only used for heating. As a matter of fact, by using an emerging technology known as EGS (enhanced geothermal systems), we are now able to also capture heat for electricity production on a large scale.

If the full economic potential of geothermal heating will be realized, scientists estimate enormous production of heat and electricity on a global scale. It is estimated that 125 projects, now under development around the U.S., will provide over 2,500 megawatts of capacity in the future.

Recommended Read: How Geothermal Energy Works (Union of Concerned Scientists)

How Geothermal Energy is Captured

At present, the most common method for capturing heat from geothermal sources is through ‘hydrothermal convection’ systems – cooler water seeps into the Earth’s crust, where it heats up, and then rises to the surface. Once the heated water rises it transforms into steam that is captured to heat buildings or drive electric generators.

Direct use of geothermal heat. Geothermal energy that is used to heat or cool buildings, de-ice roads, dry-out crops and fish, raise plants, or improve oil recovery, is referred to as direct use geothermal heat. In Iceland, virtually every building is heated through direct use of geothermal heat.

Geothermal Heating & Geothermal Cooling Technologies

As of 2005, early production of geothermal energy exceeds 273 PJ/year. The top countries using geothermal heating solutions are China (bathing), Sweden & USA (heat pumps), Turkey & Iceland (district heating), Japan, Hungary, Italy, and New Zealand.

Geothermal heating has a wide array of applications. More than half of direct geothermal heat is used for heating, while a third is used for baths and spas. Other uses of geothermal heat include desalination, domestic hot water, and agricultural applications.

Since geothermal heating systems are relatively difficult to implement on a smaller scale, systems are generally designed for multiple buildings or entire communities (district heating). The practice of distributing heat has been successfully implemented globally in locations such as Reykjavik, Klamath Falls, Oregon, and Idaho.

Industrial & Residential Applications of Geothermal Energy

Ground-source heat pumps represent a conventional method of taping into the vast resources of the Earth to heat or cool buildings (both residential and industrial). Also referred to as ground-source heat pumps, these systems take advantage of the constant year-round temperature of the ground. Antifreeze liquid or air is pumped through underground pipes to re-circulate heat through buildings.

The simplest use of ground-source heating and cooling involves a tube that runs from the outside, into the ground, and then into the buildings ventilation system. A more complicate & more effective system uses pumps and compressors to maximize heat transfer. For regions that have oscillating temperatures, ground-source heat pumps represent the most reliable, clean, and energy-efficient heating/cooling systems (far more efficient than conventional heating systems).

Geothermal heating scheme

Image source: Bach Heating & Air

Open or closed-loop systems are particularly effective for residential applications. In a closed-loop system water or refrigerant is pushed through underground pipes. These pipes can be laid in a vertical system, or they can twist over a wider, shallower area. An open-loop system works with a nearby water source (e.g. lake, river) with which it exchanges heat. This heat is returned to its source or released to a discharge site.

Hot water pre-heaters can be used to produce virtually free hot water. This sustainable system can provide approximately 50% of a home’s average water needs.

Lastly, deep and enhanced geothermal systems are installed deep below the Earth’s surface, where temperatures exceed several hundred degrees Fahrenheit. These systems inject water into the ground through a well. Hot water then rises to the surface and is captured in the form of dry steam. As opposed to ground source heat pumps or direct use geothermal systems, which scratch the surface of the Earth, deep and enhanced geothermal systems drill more than a mile in the Earth’s surface.

Geothermal heating scheme

Image courtesy of Clean Energy World News

The deep geothermal cycle follows this pattern: pumping -> delivery -> recirculation -> dispersal. This system provides efficient and clean heat for large-scale industrial and commercial processes (e.g. agricultural uses). Furthermore, dry steam can be captured by turbines to generate electricity. Despite the fact that the potential of deep and enhanced geothermal systems are limitless, the initial costs of

The Future of Geothermal Heating

Geothermal heating systems have the potential to propel the world towards a cleaner, more sustainable future. Very few renewable energy technologies can supply continuous, baseload power throughout the year. Geothermal power is one of them.

However, the road ahead will be bumpy. Two emerging technologies require further development in order to help geothermal heat reach its full potential: co-production of geothermal electricity in oil and gas wells and enhanced geothermal systems. Geothermal heating systems are already developed enough to provide a comfortable temperatures for small and large buildings alike.

What are your thoughts on geothermal energy? Are you thinking of implementing it in your home? We’d love to hear your thoughts.

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