ME 500 Test 2

1) solar thermal energy

2) solar photovoltaics

• reliability
• low operating costs
• modularity
• low construction costs

• high initial cost
• variability
• lack of infrastructure
• increased storage costs

solid-state

• silicon
• gallium arsenite crystals
• polycrystalline copper

material with electrical conductivity

• performance increase (electrical behavior)
• impurities

• doped with boron
• deficit of electrons (holes)

• doped with phosphorus
• surplus of electrons

• undoped
• i-type

doped

-energy difference between the top of valence band to bottom of conduction band

-energy required to promote electrons into conduction band

• Short circuit current
• open current voltage

photodetector capable of converting light into current or voltage

dark current and light current

highest occupied molecular orbit in valence band

A 2 terminal electrical component

measure of recombination in a device

-measure of sharpness of knee in I_V curve

-Indicates 1) how well junction was made in the cell 2) how low the series resistance is

P_max=I_max*V_max

η=P_max/P_in

A=P_req/P_max

Angular distance north or south of earth's equator

allows solar radiation to enter the collector but not reflect out

• -bottom has high optical absorption
• -absorbs solar energy
• -vertical salinity gradient

uses solar energy to heat a fluid, then transfer the heat directly to the space

-walls, windows, and floors are made to collect store and distribute solar energy

-no mechanical or electrical devices

energy store is the building itself (sunspace)

solar radiation warms the store and is radiated into the house

if the building is massive enough, and the heating system is responsible, the gains are useful

the kinetic energy of the air in motion

named on the basis of the way the wind flows over airfoils and their geometrical configuration

the fraction of the swept area that is solid

• -rotation speed [rpm], N
• -angular velocity [rad/s], ω

tangental velocity of the rotor at the tip of blades, U [m/s]

• T_max = F_maxR
• T = C_TT_max

• -blades too close together 
• -blades rotating too fast
•     -> blades in turbulent air
• vice-verse
•     -> air passes without interfering with a blade

maximum fraction of the power in the wind that can be extracted

=16/27=59.3%

equal to the relative wind angle minus the angle of attack (β)

the setting angle of the blade causes the chord to be in line with a tangent to the circular path of rotation

• -renewable
• -ubiguitous

• -variable
• -low density source
•    -> high initial cost
• -distance from area to land center

• -flow of gases on a large scale
• -caused by pressure difference

• -isobars -> equal P
• -high P -> fine weather, little wind
• -low P -> changeable windy weather, precipitation

• sea breeze:
•     -daytime
•     -land heats up quickly

• land breeze:
•     -night
•     -land cools off quickly

stationary lens shaped clouds, perpendicular to wind direction

-hills and valleys distort airflow by increasing friction (between atmosphere and land)

-wind deflection occurs (barrier jet)

• -ball of plasma
• -fusion reactor
• -92% hydrogen, 8% helium

range of EM radiation from short λ to long λ

solar radiation at the surface of the earth

• direct:
•   -amount of radiation on a surface perpendicular to the sun

diffuse:

  -indirect radiation from sky & from other surface objects

-Pyronometer (solarimeter)

-voltage proportional to total incident light energy is produced

• 1. Pumped
•    -needs heat exchanger

2. Thermosyphon

uses heat transfer to transfer heat from fluid on one side of a barrier to a fluid on the other side

1. Heat pipe evacuated tube

2. Line-focus collectors

3. Parabolic dish collectors

reduces a solid or coarse substance into minute grains by grinding

The dissimilar semiconductors at the junction. The electrons move in one direction and the protons in another.

An external voltage applied to a P-N junction

-black painted steel plate bonded with copper tubing

-glass

-insulation

• -domestic water heating
• -domestic space heating

-the vacuum enables the liquid to boil at a much lower temperature 

-when the solar radiation hits the surface of the absorber, the liquid turns to hot vapor and rises to the top

-a parabolic trough focuses to a higher energy focal line rather that a focal point 

-water flows through center

-generates steam for electricity generation

• -focus the suns energy on a small (focal) point
• -dish has mirror like absorbers at the focal point

• -sunlight is concentrated from the mirrors 
• -molten salt is pumped through the receiver and heated
• -pumped through the steam generator and creates steam

• -passive solar energy
• -sun heats chamber and warm air rises at high velocity through turbines

a loss of lift and torque and the stalled regions of the blades

the factor that takes into account the wind being slowed down as a result of power extraction

lift to drag ratio

low pressure is created on the upper surface and high pressure on the lower surface. The pressure differences causes aerodynamic lift

• using tip speed ratio
• λ=U/V=wr/V
• λ changes between 6 to 20

• -VAWT have greater solidity
• -VAWT have heavier and more expensive rotor
• -HAWT have shorter lifetime
• -VAWT don't experience gravitational loads

• -coastal areas
• -tops of rounded hills
• -open plains and gaps in mountains
• -average wind speed of 25 km/h

• Bernoulli equation:
• 

• Assume ρ=constant, z=constant
• 

• Static pressure difference
• 

• Max value of ΔP occurs as V_d approaches to zero
•