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Renewable Energy
Mohamed A. El-SharkawiDepartment of Electrical Engineering
University of WashingtonSeattle, WA 98195
Renewable Energy• Solar• Wind• Fuel Cell• Small Hydro• Geothermal• Tidal• Biomass
Solar Energy
Solar Energy (Whr/m2/day)
0%
20%
40%
60%
80%
100%
0 2 4 6 8 10 12 14 16 18 20 22 24
Time
Density ratio
Daily Solar Power Density
2 σ
Types of Solar Systems
– Passive Solar System
– Active Solar System (Photovoltaic or PV)
2
Passive Solar System
Lens
Sun rays
Warm water
New supply of cold water Warm water to the house
Cold water back
to solar collector
Tank
Collector
Passive Solar
Active Solar Cell (PV)Active Solar Cell (PV)• PV cell is built like a diode out of semiconductor
material.
• Sunlight is composed of photons, or particles of solar energy. Photons are the energy byproducts of the nuclear reaction in the sun.
• When photons strike a PV cell, some of the protons energy is absorbed by the semiconductor material of the PV cell.
Active Solar Cell (PV)Active Solar Cell (PV)
• With this extra energy, the electron in the semiconductor material become excited and break off its atom, and eventually begin an electric current.
• Because PV cells are built like diodes, free electrons are forced to flow in only one direction
P-Type
Base
N-Type
Lens
-
-
I
Load
3
Structure of Solar SystemStructure of Solar System•• PV cell:PV cell: 4X4 inches. The cell can produce
about 1 watt which is enough to run a calculator.
•• Panel or Module:Panel or Module: To increase its energy rating, the PV cells are connect together in parallel and series.
• Parallel cells increase the current rating
• Series cells increase the voltage rating.
Structure of Solar SystemStructure of Solar System
•• Array:Array: PV panels connect together in parallel and series to form a high power system.
Structure of Solar SystemStructure of Solar System
4
Stand Alone PV System
ChargerDischarger
Con
verte
r
Local loadBattery
Solar array
House
dc current
ac current
PV System without battery
Con
verte
r Meter To utility
Local load
Solar array
House
dc c
urre
nt
ac current
Solar Power and the Environment
• 6kW from a photovoltaic system instead of a thermal power plant can reduce annual pollution by – 3 lbs. of NOx (Nitrogen Oxides),
– 10 lbs. of SO2 (Sulfur Dioxide), and
– 10530 lbs. of CO2 (Carbon Dioxide).
Solar Power and the Environment
• Solar system uses large areas of land.• PV systems are costly. • The efficiency of the solar panel is low.• Toxic chemicals are used to manufacture
solar cells.– Arsenic and Silicon.
– Since water is used in the process, the runoff causes pollution into local streams.
Wind Energy
5
Kinetic Energy of Air
2
21 vmKE =
δδ tvA*volumem ==
• m: mass of air
• v: speed of wind
• A: sweep area
• δ: air density (kg/m3)
• t: time
Generator
High speed shaft
Low speed shaft
Rotating blades Gear box
Tower
Housing
Wind TurbineTehachapi System
Off-Shore Wind System
6
Horizontal Axis Wind Turbine (HAWT) Vertical Axis Wind Turbine (VAWT)
Wind Energy and the EnvironmentWind Energy and the Environment
• Wind turbines don’t emit any pollution gas.
• Concerns include noise pollution, aesthetics, and bird collision.
• Wind is normally strongest at night when the power demand is the lowest.
Fuel CellFuel Cell
7
Generation of Hydrogen
H2
CO2
CO
CO
conv
ersi
on
H2O CO2
H2
Fuel Cell
Water(H2O)
Ref
orm
er
CH2
O2
Hydrocarbon fuel
Cat
hode
Ano
de
Electrolyte
Fuel Cell (Electrochemical Process)
Load
----
Hydrogen
2H2
Ions4H+
Oxygen (Air)
O2
Water2 H2O
I
- ---
- - --
Fuel Cell
• Produces power without combustion or rotating machinery.
• Makes electricity by combining hydrogen ions, drawn from a hydrogen-containing fuel, with oxygen atoms.
• The current is proportional to the size (area) of the electrodes.
• The voltage is limited electrochemically to about 1.23 volts per electrode pair, or cell.
• Cells can be “stacked” until the desired power level is reached.
Issues• Pure hydrogen is a volatile gas, and requires
special storage and transportation. • Hydrogen cannot be found free in nature, it is
often extracted by reformers• Efficiency of fuel cells including the reformer
process is 26 to 40%• Efficiency of internal combustion engines is
15 to 22%
8
Fuel Cell System for Water Treatment
9
Small Hydro
Types of small hydro systems
• Reservoir-Type• Diversion-Type
Reservoir-Type Small Hydro System
Generator
Turbine
Reservoir
Penstock
Discharge
Head
Diversion-Type Small Hydro System
Generator
Turbine
Discharge
10
Geothermal Energy
Heat Pump
Hot water Tank
Pumpand Heat
Exchangers
Ground Geo-exchanger
Warm air to house
Return cool air
Geothermal Power Plant G
Mist eliminator
CoolingTower
Steam
HeatMagma
Reservoir
Turbine
11
Geothermal Energy• Geothermal site must have the magma close enough to
the surface to heat reservoirs accessible by current drilling technology..
• Underground reservoirs are often surrounded by very hard rock.
• The geothermal fluid can cause water pollution due to the presence of some gases and metals in the reservoirs.
• Geothermal fields could also produce carbon dioxide, but at much lower level (1/6) than what a natural gas power plant produces.
• Processing the reservoir fluid can produce objectionable odors.
Tidal Energy
High Tide
Water Flow
Dam
Turbine
Shore
Lagoon Side
Sea Side
Low Tide
Water Flow
12
Issues
• Dams can slow the flow of water, thus potentially stimulate the growth of the red tide organism.
• Tidal energy is expensive method. • Energy can only be generated when
the current is strong around peak or the slack of the tied.
Biomass Energy
Landfills• Housings are being expanded closer to landfills• Landfills and the trucks are considered sight
pollution and safety hazards.• Landfills produce unpleasant odors.• Leachate, which is the fluid resulting from water
mixed with garbage contaminates underground water.
• Ethanol (alcohol) and Methanol can be generated in landfills increasing the fire hazards
G
Filter Storage
StackWater pipes
Steam
Furnace
Condenser
Heavy ashto landfills
Light ashTo landfills
Turbine
Biomass Burning
• Biomass incineration produce heavy metal and Dioxins
• Heavy metal is mixed with ash posing serious pollution to water.
• Dioxin is the most dangerous element. It is highly carcinogenic and can cause cancer and genetic defects.