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Geothermal Systems: Renewable and Ready
Geothermal (Geoexchange) heating and cooling systems are the most energy-efficient, environmentally clean, and cost-effective space conditioning systems available. Geothermal systems can reduce energy consumption--and corresponding emissions--by over 40% compared to air source heat pumps and by over 70% compared to electric resistance heating with standard air-conditioning equipment. Combining Geothermal with other energy-efficiency measures (such as window or insulation upgrades) can increase these savings synergistically.
How Geothermal works: Geothermal systems use the Earth's energy storage capability to heat and cool buildings, and to provide hot water. The earth is a huge energy storage device that absorbs 47% of the sun's energy--more than 500 times more energy than mankind needs every year--in the form of clean, renewable energy. Geothermal takes this heat during the heating season at an efficiency approaching or exceeding 400%, and returns it during the cooling season. Geothermal heating and cooling systems use conventional vapor compression heat pumps to extract the low-grade solar energy from the earth. In summer, the process reverses and the earth becomes a heat sink.
Heat exchanger designs include closed loop systems which use horizontal or vertical heat exchangers made of heat-fused high density polyethylene pipe. These systems usually circulate water with a biodegradable antifreeze added. Open loop systems generally draw ground water through the heat pump, and return it to the ground unaltered except for a all temperature change.
Geothermal is renewable: Geothermal is a renewable resource. In the heating mode, an efficient Geothermal system will move at least three units of solar energy from the ground for each unit of electricity used by the heat pump and its accessories. In the cooling mode, the same heat exchanger rejects heat to the surrounding ground, which equilibrates with the atmosphere. The energy flux attributable to the heat pumps is orders of magnitude lower than the solar energy received at the ground.
Geothermal synergies with building efficiency: More efficient systems, better building envelopes, and art ventilation in commercial systems minimize the amount of geothermal heat exchanger required, giving Geothermal building designers strong incentives for more efficient building designs. In residential Geothermal applications, and improved shell efficiency also pay strong dividends in both first costs (by allowing equipment down-sizing), and operating costs, to a far greater extent than for conventional heating and cooling systems. Geothermal domestic hot water, through "desuperheaters," and through "full condensing" hot water systems, can save consumers several hundred dollars per year.
More: One potential source that we've barely tapped is right underneath our feet. Deep inside the Earth lies hot water and steam that can be used to heat our homes and businesses and generate electricity cleanly and efficiently. It's called geothermal energy -- from the Greek words geo, or "earth," and therme, meaning "heat." There is plenty of heat in the center of the Earth. The deeper you dig, the hotter it gets. The core, about 4,000 miles (6,437 kilometers) beneath the surface, can reach temperatures of 7,600 degrees Fahrenheit (4,204 degrees Celsius). Part of that heat is left over from the Earth's formation, about 4 billion years ago. The rest comes from the constant decay of radioactive isotopes inside the Earth.
How Can We Use Geothermal Energy?
--Heat is sitting under the Earth -- we just need to tap it. Geothermal energy can be used in three ways:
Historical Heat
People began harnessing geothermal energy thousands of years before they had the technology to dig down into geothermal reservoirs. The ancient Romans used hot springs to heat their homes, bathe and cook. In 1892, the first modern district heating system was developed in Boise, Idaho. It used water piped from hot springs to heat buildings. The first geothermal energy plant was built in Larderello, Italy, in 1904.
Today, geothermal energy is used mostly in France, Turkey, New Zealand, the United States and Japan, among others. Iceland is one of the biggest users of geothermal energy -- virtually the entire city of Reykjavik is heated with water pumped in from hot springs and geothermal wells. Some cities -- like Klamath Falls, Ore. -- even pump hot water underneath their roads and sidewalks in the winter to melt snow and ice.
¬Direct geothermal energy. In areas where hot springs or geothermal reservoirs are near the Earth's surface, hot water can be piped in directly to heat homes or office buildings. Geothermal water is pumped through a heat exchanger, which transfers the heat from the water into the building's heating system. The used water is injected back down a well into the reservoir to be reheated and used again.
Geothermal heat pump. A few feet under the ground, the soil or water remain a constant 50 to 60 degrees Fahrenheit (10-15 degrees Celsius) year-round. Just that little bit of warmth can be used to heat or cool homes and offices. Fluid circulates through a series of pipes (called a loop) under the ground or beneath the water of a pond or lake and into a building. An electric compressor and heat exchanger pull the heat from the pipes and send it via a duct system throughout the building. In the summer the process is reversed. The pipes draw heat away from the house and carry it to the ground or water outside, where it is absorbed.
Geothermal power plant. Hot water and steam from deep underground can be piped up through underground wells and used to generate electricity in a power plant. Three different types of geothermal power plants exist:
Dry steam plants. Hot steam is piped directly from geothermal reservoirs into generators in the power plant. The steam spins turbines, which generate electricity.
Flash steam plants. Water that's between 300 and 700 degrees Fahrenheit (148 and 371 degrees Celsius) is brought up through a well. Some of the water turns to steam, which drives the turbines. When the steam cools it condenses back into water and is returned to the ground.
Binary cycle plants. Moderately hot geothermal water is passed through a heat exchanger, where its heat is transferred to a liquid (such as isobutene) that boils at a lower temperature than water. When that fluid is heated it turns to steam, which spins the turbines.
Geothermal Energy- A Greener Energy
This process accessing the heat below the Earth's surface. Experts say geothermal energy is cleaner, more efficient, and more cost-effective than burning fossil fuels
Geothermal energy is clean because it can be generated without burning fossil fuels. And reduce our dependence on fossil fuels for energy generations.
Because the energy is generated right near the plant, it saves on processing and transportation costs compared to other types of fuel. Geothermal plants are also considered to be more reliable than coal or nuclear plants because they can run consistently, 24 hours a day, 365 days a year.
The initial costs of geothermal energy are high -- However, a home geothermal energy pump can cut energy bills by 30 to 40 percent and will pay for itself within 5 to 10 years
Geothermal energy is considered renewable because the heat is continually replaced. The water that is removed is put right back into the ground after its heat is used.
The world uses about 7,000 megawatts of geothermal energy, about 2,700 megawatts of which is produced in the United States (the equivalent of burning 60 million barrels of oil each year. Still, we're not using nearly as much geothermal energy as is available. That has to do with the limited geographic availability of geothermal energy, and the difficulty and expense of drilling down far enough to reach that energy. More advanced techniques being developed could allow for deeper drilling, potentially bringing geothermal energy to more people in more places.
¬For right now, geothermal heat pumps are the most viable option. They can be used just about anywhere in the world because the temperature beneath the ground always remains constant.
Facts about Geothermal Systems (Heating and Cooling).
• Geothermal heat pumps is identified as a technology that significantly reduces greenhouse gas and other air emissions associated with heating, cooling and water heating residential buildings, while saving consumers money, compared to conventional technologies. For every 100,000 units of typically sized residential geothermal heat pumps installed, more than 37.5 trillion Btu's of energy used for space conditioning and water heating can be saved, corresponding to an emissions reduction of about 2.18 million metric tons of carbon equivalents, and cost savings to consumers of about $750 million over the 20-year-life of the equipment.
• Geoexchange heat pump systems, also known as "Geothermal," are the most energy efficient, environmentally clean, and cost-effective space conditioning systems available.
• Every 100,000 homes with geothermal heat pump systems reduce oil consumption by 2.15 million barrels annually and reduce electricity consumption by 799 million kilowatt hours annually.
• Geothermal heat pumps are efficient. The use of Geothermal lowers electricity demand by approximately 1 kW per ton of capacity.
• Geothermal heat pumps are environmental. They generate no on site emissions and have the lowest emissions among all heating and cooling technologies.
• Geothermal heat pumps save money. Schools now using geothermal heat pump systems
• save more than $25 million in energy costs (in US) – meaning more money for books, equipment and teachers.
• Homeowners can save 25 to 50 percent on home electric bills compared to conventional heating and cooling systems. Electric bills for a 2,000 sq. ft. home can be reduced to as low as $1 a day, using a Geothermal system.
• Geothermal systems represent a savings to homeowners of 30 to 70% in the heating mode and 20 to 50% in the cooling mode, compared to conventional systems.
• It is found that Geothermal heating and cooling systems can reduce energy consumption — and corresponding emissions—by more than 40% compared to air source heat pumps and by over 70% compared to electric resistance heating with standard air-conditioning equipment.
• Geothermal systems use the Earth's energy storage capability to heat and cool buildings, and to provide hot water. The earth is a huge energy storage device that absorbs 47% of the sun's energy – more than 500 times more energy than mankind needs every year – in the form of clean, renewable energy. Geothermal systems take this heat during the heating season at an efficiency approaching or exceeding 400%, and return it during the cooling season.
• It is found that, even on a source fuel basis – accounting for ALL losses in the fuel cycle including electricity generation at power plants – Geothermal systems are much more efficient than competing fuel technologies. They are an average of 48% more efficient than the best gas furnaces on a source fuel basis, and over 75% more efficient than oil furnaces.
• In fact, today's best Geothermal systems outperform the best gas technology, gas heat pumps, by an average of 36% in heating mode and 43% in cooling mode!
• Surveys by utilities indicate a higher level of consumer satisfaction for Geothermal systems than for conventional systems. Polls consistently show that more than 95% of all Geothermal customers would recommend Geothermal to a family member or friend.
• Today there are now more than 1,000,000 Geothermal installations in the United States. The current use of geothermal heat pump technology has resulted in the following emissions reductions:
• Elimination of more than 5.8 million metric tons of CO2 annually
• Elimination of more than 1.6 million metric tons of carbon equivalent annually These 1,000,000 installations have also resulted in the following energy consumption reductions:
• Annual savings of nearly 8 billion kWh
• Annual savings of nearly 40 trillion Btus of fossil fuels
• Reduced electricity demand by more than 2.6 million kW
The monumental impact of the current use of Geothermal is equivalent to:
• Taking close to 1,295,000 cars off the road
• Planting more than 385 million trees
• Reducing U.S. reliance on imported fuels by 21.5 million barrels of crude oil per year.
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