Unit 6 Geothermal

8/9/2019 Unit 6 Geothermal

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Introduction to AlternativeIntroduction to AlternativeEnergiesEnergies

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After completing this unit you will

Be able to explain what geothermal energy is

and where it comes from

Know ways to use geothermal energy and

Be able to determine the energy savings and

other benefits of using geothermal heat

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What is

geothermal energyand where does it

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Geothermal

The word geothermalcomes from the Greek

words

Geo which means earth

erme w c means eat

Geothermal is heat from the Earth

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Geothermal energy is generated in the earth'score, about 4000 miles below the surface

Temperatures hotter than the

sun's surface are

continuously produced inside

of radioactive particles,

A process that happens in all rocks

The earth has a number ofdifferent layers

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Solar Radiation As we have previously learned, there is also a

tremendous amount of energy received from

the sun

The following slide shows Earths Energy

Bu get , t e amount o so ar ra iationabsorbed and reflected by Earth

You will note half of the solar radiation is

absorbed by Earths surface and stored in theground

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Solar Radiation

http://asd-www.larc.nasa.gov/SCOOL/energy_budget.html 9


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Between the energy fromthe core and stored solar

radiation, the ground stays

at a relatively constanttemperature (50 to 55 F)

renewable energy source

because the heat is

continuously producedboth inside the earth and

solar radiation

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How can we use

geothermal energyand what are

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Geothermal Energy ApplicationsThere are two main ways that geothermal

energy can be used1. The energy from the earths core creates

e sers steam which can be used to run

electricity generators, geothermal powerplants

2. The stored energy in the earths crust can be

used as a heat source (winter) and a heatsink (summer), geothermal units or groundsource heat pumps

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Geothermal Power Plants Wells, over one mile deep, are drilled into

underground reservoirs tapping hot water andsteam sources

The hot water and steam are used to run

various electricity generatorsThere are three main types of power plants

Dry steam plants

Flash steam plants

Binary-cycle plants

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Dry Steam Plants Use hydrothermal fluids that are primarily

steam

The steam goes

directly to a

,drives a

generator that

produceselectricity

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The steam eliminates the need to burnfossil fuels to run the turbine

Also eliminating the need to transport

and store fuels

This is the oldest type of geothermal

power p ant. It was irst use atLardarello in Italy in 1904, and is still

very effective

These plants emit only excess steam andvery minor amounts of gases

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The Geysers Geothermal area, north of SanFrancisco, California, is the world's largest dry-steam geothermal steam field

Powerproduction atthe Geysersreached eak

production in1987, at thattime serving1.8 millionpeople

From US Department of Energy, Energy Efficiency and Renewable Energy

http://www1.eere.energy.gov/geothermal/geysers.html

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Flash Steam Plants Hydrothermal fluids above 360F (182C) can

be used in flash plants to make electricity

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Fluid is sprayed into a tank held at a muchlower pressure than the fluid, causing some of

the fluid to rapidly vaporize, or "flash

The vapor then drives a turbine, which drives

a generator

I any iqui remainsin the tank, it can be

flashed again in a

second tank toextract even more

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Binary-cycle Plants Most geothermal areas contain moderate-

temperature water (below 400F)

Energy is extracted from these fluids in binary-

cycle power plants

Hot geot erma ui an a secon ary ence,"binary") fluid with a much lower boiling point

than water pass through a heat exchanger

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Because this is a closed-loop system, virtuallynothing is emitted to the atmosphere

Moderate-temperature water is by far the

more common geothermal resource, and

most geothermal

power p an s n

the future will be

binary-cycle

plants

http://www.americansforamericanenergy.org/geothermal.aspx 21


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Geothermal Units Geothermal Units are ground

source heat pumps (GSHP) They take advantage of the

consistent (50 to 55 F) groundtemperature using a fluid to

exchange heat back and forthbetween a residence and theground

These heat pumps can coolduring the summer and heatduring the winter

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The following diagram shows GeothermalCooling in the Summer

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The following diagram shows GeothermalHeating in the Winter

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Geothermal units use a fluid flowing throughan underground coil system

The coil system uses the constant 50 to 55

degree ground temperature to either absorbor rejectheat

T e specia eat-exc anging coiis a tube-within-a-tube that

allows the fluid to exchange

heat with the ground withoutphysically coming into contact

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Unlike conventional systems, which requireseveral components, the Geothermal Unitsconsists of a single indoor cabinet

Connected to the indoor cabinet is theunderground line system

The main t es of line s stems are one of

three different closed loop systems1. Horizontal

2. Vertical

3. Pond/lake

Or an open loop system that uses waterdirectly from wells or pond/lakes

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Horizontal More commonly used and cost effective in

residential, using trenches that are four to six

feet deep with two pipes placed side by sideor one above the other

no er me o s

looping the pipe

allowing a greater

length of pipe in ashorter trench reducing

installation cost

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Vertical Approximately 4 inch diameter holes are

drilled 100 to 400 feet deep approximately 20

feet apart

In the holes go two pipes

connecte at t e ottom wita U-bend to form a loop

The vertical loops are

connected with horizontalpipe

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Vertical loops

Vertical loop systems are commonly usedmore for industrial and commercial type

buildings where lack of excess of land is

prohibitive for horizontal trenches

where existinglandscape may

prohibit the

installation of

trenches

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Pond/Lake If the site has an adequate water body, this

may be the lowest cost option

A supply line pipe is run underground from

the building to the water and coiled into

circ es at east eig t eet un er t e sur ace toprevent freezing

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Open Loop System Uses wells or lake/pond water as the heat

exchange fluid, directly circulating it through

the geothermal unit

After the water is circulated through the unit;

it is retune to t e groun to rec arge t ewells or lake/pond

Must have an adequate

supply of relatively cleanwater and comply with all

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How would you

determine the

energy savings

of usingGeothermal heat

pumps

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Energy Savings with Heat Pumps Geothermal Heat Pumps use 25% to 50% less

electricity than conventional heating andcooling systems

,

energy consumption, and corresponding

emissions

Up to 44% compared to air-source heat pumps And up to 72% compared to electric resistance

heating with standard air-conditioning

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Efficiency of Geothermal Heat Pumps The heating efficiency of heat pumps is

indicated by their coefficient of

performance (COP)

The cooling efficiency is indicated by the

Energy E iciency Ratio EER

Recommended minimums for systems

are a COP of 2.8 and an EER of 13

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Coefficient of Performance COPThe ratio between useful energy acquired and

energy applied can be expressed as:

COP = Eu/ Ea

Where:COP= coefficient of performance

Eu = useful energy acquired (Btu)

Ea = energy applied (Btu)

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COPcan be used to define both coolingefficiency or heating efficiency

Cooling is the ratio of the rate ofheat removalto

the rate of energy input to the compressor Heating is the ratio of rate ofheat deliveredto the

rate of ener in ut to the com ressor

For purposes of comparison, the higher the

COPthe more efficient the system

COP can be treated as an efficiency where

COP of 2.00 = 200% efficient

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Energy Efficiency Ratio EER Generally used to define the cooling

efficiency of air-conditioning and heat

pump systems

The ratio of heat removed in Btu/h to

t e tota input rate o e ectric energyapplied in watt hour, and determined by

the following:

EER = COP x 3.412

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Compared to other heating/cooling sources Residences in our area use 45,000 to 85,000

BTUs per hour on a very cold day

On the low side (45,000 BTU), this is just over

a million BTUs per day

In order to compare costs of various systemsyou must look at

1. The units of the energy sources required

2. The cost per unit

3. The efficiency or COP of the system

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Comparing the common heating/coolingsystems

Heating/Cooling System

Cost/unit of

Energy Source

Cost/million

Btu of Heat

Natural gas furnace (95% efficient)

1000 ft3 (1 MCF) = 1,020,000 Btu$13.65/MCF $14.09

one gallon = 91,333 Btu

$2.42/gal $27.89

Electric Heat

1 kWh = 3412 Btu$0.108/kWh $31.65

2.8 COP Geothermal Heat Pump

1 kWh = 9554 Btu$0.108/kWh $11.30

4.2 COP Geothermal Heat Pump

1 kWh = 14,330 Btu$0.108/kWh $ 7.54

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Economics of Geothermal Heat Pumps Geothermal systems typically have a higher

initial cost compared to conventional

heating/cooling systems

On average, a geothermal heat pump system

costs roug y 7,500 or a 3-ton unit a typicaresidential size)

In comparison, other conventional systems

cost about $4,000

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Although initially more expensive to installthan conventional systems, geothermal

systems deliver more energy per unit

consumed than the conventional systems Because of higher efficiencies, they are less

saving 30% to 60% in energy costs

Depending on the climate and ground

characteristics, the initial investment can berecouped in two to ten years

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Other Benefits of Heat Pumps Give great design flexibility

The systems are smaller than conventionalHVAC systems, stored inside, and of simple

Unlike conventional heating systems,

geothermal systems do not have any

combustion, reducing pollution and globalwarming

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No outdoor compressors Not susceptible to the elements or vandalism

Components are easily accessible increasing

the convenience of routine maintenance

Because they have no outside condensing

units like air conditioners, there's no concernabout noise outside the home

There iszerozero noise pollution from geothermal

systems

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Relatively few moving parts There are very few moving parts

and because the unit is housed

inside, away from the elements,these units are very reliable and

The underground piping often

carries warranties of 2550

years, and the heat pumps oftenlast 20 years or more

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No pollution or addition to Global Warming Because geothermal systems do not burn

fossil fuels to generate heat, there arezerozero

emissions from the unit itself

Today there are over one million geothermal

units insta e in t e U.S. w ic equa s

The reduction of nearly 40 trillion

BTUs of fossil fuels

The elimination of 5.8 millionmetric tons of CO2

Taking 1.3 million cars off the road

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Work Citedhttp://www.eia.doe.gov/kids/energyfacts/sources/renewable/geothermal.html#InEarth

http://www1.eere.energy.gov/geothermal/

http://www.americansforamericanenergy.org/geothermal.aspx

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Unit 6 Geothermal

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Transcript of Unit 6 Geothermal