Energy And Electricity Flashcards
Where does wind come from?
It’s solar.
The earth continuously released into the atmosphere the heat received by the sun but unevenly
Types of renewable sources of energy
Nuclear Hydroelectric Waves Geothermal Biomass Wind Solar
How wind turbines work
- When the blades start moving, they spin a shaft that leads to s generator
- The generator consists of a conductor (ex. A coiled wire surrounded by magnets)
- The rotating shaft turns the magnets around the conductor and generates an electrical current
- Sensors cause the top of the turbine to rotate to face the wind and the blades change their angle to best catch the wind ️n the blades are flexible and stop spinning if there is too much wind
Wind miss application
- Wind turns the turbine blades
- Spinning the shaft
- Generating electricity
- An inverter converts electricity from DC to AC
- Electricity is connected directly to the mains power
- Or connected to a battery bank
- Or connected to the electrical grid
Advantages of wind energy
- Available and free
- Renewable
- Costs are decreasing
- No pollution
- Works all day/night
Disadvantages of wind energy
- Still uses land
- Wind fluctuates
- Mostly in rural areas
- Electricity storage?
Windmill packing density
As a windmill extracts energy from the wind, the turbine leaves behind it a wake characterized by reduced wind speeds and increased levels of turbulence
A turbine operating in the wake of a turbine will produce less energy and suffer greater structural loading
Rule of thumb: windmills cannot be spaced closer that ___times their diameter without losing significant power
5
Kinetic energy of a windmill
KE= 1/2ρAtv^3
Wind power density (per unit area and per second)
P= 1/2ρv^3
Power output from a wind turbine
P= 1/2(Cp)ρAv^3
Cp= the power coefficient= the fraction of the power in the wind that may be converted by the turbine into mechanical work
Where does solar energy come from?
Sun (a star)
Thermonuclear fusion
Entire EM spectrum
The amount of solar energy that reaches the surface of the earth every hour is greater than…
Humankind’s total demand for energy in one year
Non electric solar energy
Water heating Heating living spaces Day lighting Drying Agriculture
Solar energy generating electricity
Photovoltaics
Power tower
Concentrated and remote (ex. Asteroid rover)
About how much of the sun’s energy makes it to the surface of the earth?
47%
___% of solar energy comes from the middle 6 months
70%
Basics of solar powered water heaters
- Collector absorbs energy
- Heats water
- Water circulates (passive or active)
- Tank stores water
Color absorption
Dark colors absorb a lot and reflect a little
Light colors absorb little and reflect a lot
Power tower basics
- Collect light/energy from many reflectors
- Heat water
- Parabolic (parallel rays converge)
- Track the sun
Disadvantages of solar power
Inefficient and costly equipment
Part time
Reliability depends on location
Environment impact of PV cell production
A mill uses…
Mechanical rotational energy for work and processing
From water or wind
Breast shot wheel
One type of traditional water wheel
Overshot wheel
More efficient than breast shot wheel
What are dams for?
Recreation Drinking water Flooding Irrigation Energy
Hydroelectric power system
Flowing water is directed at a turbine (advanced water wheel)
The flowing water causes the turbine to rotate, converting the water’s KE to ME
The amount of electricity that can be generated by a hydropower plant depends on:
- Flow rate: the quantity of water flowing at a given time
- Head: the height from which the water falls
The greater the flow and the head, the more electricity produced
Standard equation for calculating energy production hydraulically
P= (head)(flow)(efficiency)*11.8
11.8= index that converts units of feet and seconds to kW kW= ft*ft^3/s*%
How useful is dam energy?
Moderate to high net useful energy yield
Fairly low operating and maintenance costs
Low pollution
Rarely shut down
Help control flooding
Supply a regulated flow of irrigation water to lowlands below the dam
