Geothermal Application

8/3/2019 Geothermal Application

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The term Geothermal originates from two Geek words 'GEO' and'THERM'. The Greek word geo meant the earth whilst their word fortherm meant heat from the earth.


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Geothermal energy is energy derived from the heat of the earth. The

earths centre is a distance of approximately 4000 miles and is so hotthat it is molten. Temperatures are understood to be at least 5000degrees centigrade. Heat from the centre of the earth conductsoutwards and heats up the outer layers of rock called the mantle.

When this type of rock melts and becomes molten it is called magma.Magma can reach just below the earths surface.

Rain water sometimes seeps down through geological fault lines andcracks becoming super heated by the hot rocks below. Some of thissuper heated water rises back to the surface of the earth where itemerges as hot springs or even geysers. Sometimes the hot water

becomes trapped below the surface as a geothermal reservoir.


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One way of producing electricity from geothermal energy is bydrilling wells into the geothermal reservoirs. The hot water that risesemerges at the surface as steam. The steam is used to drive turbinesproducing electricity. If the water is not hot enough to produce steam,

it can still be used to heat homes and businesses, saving gas/electricity.


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DRY STEAM POWER PLANT

Dry Steam Plants produce electricity directly from the steam thatemerges at the earths surface. The steam drives turbines.


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BINARY CYCLE POWER PLANT

If the water that reaches the surface is not hot enough to produce

steam, it can still be used to produce electricity by feeding it into aBinary Power Plant. The hot water is fed into a heat exchanger. Theheat from the water is absorbed by a liquid such as isopentane whichboils at a lower temperature. The isopentane steam is used to driveturbines, producing electricity. The isopentane then condenses back toits liquid state and is used again.


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Flash Steam Power Plants are the most common form of geothermalpower plant. The hot water is pumped under great pressure to thesurface. When it reaches the surface the pressure is reduced and as aresult some of the water changes to steam. This produces a blast of steam. The cooled water is returned to the reservoir to be heated bygeothermal rocks again.

FLASH STEAM POWER PLANT


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Fundamentals - 1HP = machine causes heat to flow uphill

From lower to higher temperature Work done pump used to describe Refrigeration unit reversibleHeat absorbed = source Heat delivered = sink

Difference in temperature = lift The greater the lift greater power input


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Fundamentals - 2

Geothermal (ground-source) heat pumpsUses geothermal resource between 40 and 90 FEither removes heat from a low temperature resourceto a higher temperature reservoir (heating)Or removes heat from a high temperature resource toa lower temperature reservoir (cooling)

Geothermal use a constant temperatureresource

The ground or groundwater (below about 30 ft.)


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Fundamentals -3 Air-source heat pumps dependent on outside airtemperature, which is:

Lowest when heating demand is highest, andHighest when cooling demand is highestThus, supplemental energy (electric) source needed


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Advantages of GHP

(as compared to air-source)They consume less energy to operateThey tap a constant temperature resource

They do not require supplemental energy duringextreme outside air temperatureSimpler in design and maintenance

Does not require a unit outside exposed to the weatherLonger equipment life


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Disadvantages of GHP

(as compared to air-source)Higher initial cost due to excavation for piping ordrilling of a wellLack of trained and experienced designers andinstallersShallow horizontal heat exchangers are affected by surface (air and sun) temperature variations thus, requiring 30 to 50% more pipe in the ground


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Definitions - 1General terms:Ground-Source Heat Pumps (GSHP)

Used by engineers and technical types, andThe International Ground Source Heat Pump Association

Geothermal Heat Pumps (GHP)Used by individual in marketing and governmentOften confused with direct-use geothermal

GeoexchangeUsed by Geothermal Heat Pump Consortium

Geothermal Systems in many countries confusingBelow ground = geothermal


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Definitions 2Ground-coupled or earth-coupled (closed loop) tubing network directly buried in the ground -generally a thermally-fused plastic pipe (HDPE) with water or antifreeze (20% propylene glycol)

solution circulated through the tubingHorizontal VerticalSpiral coil in vertical holeSlinky in a horizontal trench

Encased in a foundation pileDirect expansion (no heat exchanger)One or more loops in a single hole or pile


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Definitions - 3

Groundwater or water-source (open loop)systems use well or lake water. Water quality may be a problem due to calcium carbonate (hardness)and/or iron bacteria causing scaling or fouling of the heat exchangers

Well waterLake waterMine waterTunnel waterStanding column


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Low-temperatureunderfloor heating

Heat pump

Hot watertank

Boreholeheat exchanger


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Trenching

Horizontal loopsSpiral slinky


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Benefits of Geothermal Heat Pump Systems

The biggest benefit of GHPs is that they use 25% 50% less electricitythan conventional heating or cooling systems. This translates into aGHP using one unit of electricity to move three units of heat from theearth. According to the EPA, geothermal heat pumps can reduce

energy consumption and corresponding emissions up to 44%compared to air-source heat pumps and up to 72% compared toelectric resistance heating with standard air-conditioning equipment.GHPs also improve humidity control by maintaining about 50%relative indoor humidity, making GHPs very effective in humid areas.Geothermal heat pump systems allow for design flexibility and can beinstalled in both new and retrofit situations. Because the hardwarerequires less space than that needed by conventional HVAC systems,the equipment rooms can be greatly scaled down in size, freeing space

for productive use.


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GHP systems also provide excellent "zone" space conditioning,allowing different parts of your home to be heated or cooled todifferent temperatures.

Because GHP systems have relatively few moving parts, and becausethose parts are sheltered inside a building, they are durable andhighly reliable. The underground piping often carries warranties of 25 50 years, and the heat pumps often last 20 years or more. Sincethey usually have no outdoor compressors, GHPs are not susceptibleto vandalism. On the other hand, the components in the living spaceare easily accessible, which increases the convenience factor and

helps ensure that the upkeep is done on a timely basis.

Because they have no outside condensing units like air conditioners,there's no concern about noise outside the home. A two-speed GHPsystem is so quiet inside a house that users do not know it isoperating: there are no tell-tale blasts of cold or hot air.


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ConclusionsGeothermal (ground-source) heat pumps arenot a new technology Lord Kelvin developedthe concept of heat pump in 1852.GHP popularity started in the 1960s and 70s

Growing at least 15%,yr; now 20%/yr Are economically competitive in areas of highalternate fuel costBest suited for large building loads, such as

schools, commercial buildings, etc.Best suited for new construction, as retrofits areexpensive

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Geothermal Application