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Questions in this quiz (69)
1What is a photvolatic system
- AA system that converts sound energy into electrical power
- BA system that converts light energy into electrical power
2Advantages / disadvantages of single and polycrystalline silicone
- Ahigh efficiency (14-22%)
- Bestablished leading technology
- Cchemically stable
- Dhigh absorption requiring less material
- Eeasily deployed
- Fmore sustainable
- Gexpensive production
- Hlow absoprtion coefficient
- Irequires a large amount of feed stock
- Jmoderate (stabilised) efficiency; 7-10%
3Advantages and disadvantages of amorphous silicon
- Ahigher absorption requires less material
- Bestablished technology
- Ceasily developed
- Dchemically stable
- Ehigh efficiency (14-22%)
- Flow absorption coefficient
- Genvironemntaly more sustainable
- Hlow cost
- Imoderate (stablisied) efficiency; 7-10%
- Jdegradable when illumintaed
4P-Type silicone is doped with
- ABoron
- BPhosphorous
5N-type is doped with
- Aphosphourous
- Bboron
6The new energy state for a phosphouous doped n-type semi conductor is
- Aa donor state just below the CB
- Ba donor state just above the VB
- Can acceptor state just below CB
- Dan acceptor state just above VB
7The new energy state for a boron doped p-type semi conductor is
- Aa donor state just below CB
- BA donor state just above VB
- CAn acceptor state just above VB
- DAn acceptor state just below CB
8what determines the band structure
- APeriodic array of atoms in a crystal
- Bjoining method of the PN junction
9what is a more complex absorption procedure, why and its effects
- ADirect gap
- BIndirect gap
- CPhonon involved with process to ensure momentum conservation
- Dno phonon interaction
- Edecreasees absorption efficiency of light by semi conductor
10What is the process of generating an electron hole pair
- Aphonon enters, is absorbed, and excites electron from CB to VB if E>Eg
- Bphoton enters, is absorbed, and excites electron from VB to CB if E>eg
- Cthis leaves two holes behind in the CB
- DThis leaves a hole behind in the VB
- Edue to the energy needing to be E>Eg all of the solar spectrum can be absorbed
- Fdue to the energy needing to be E>Eg only part of the solar spectrum can be converted
11what are the three recombination methods with a brief description
- AShockley-Read-Hall: Occurs in perfectly formed silicone. A electron, can recombine with a hole in the CB from the VB by emitting a photon of simliar energy to the band gap so it can escape
- BRadiate: a photon is emitted, enabling an electron to recombine with a hole in the VB. This is prevelant in direct band gap semi conductors
- CAuger: this is a four carrier process. Three carriers drop from the CB to the Vb by passing energy to a single electron that is excited up to higher energy levels in the CB where it stays permanently.
- DShockley-Read-Hall: this occurs in defective silicone. Another energy level exists in the 'forbidden region' in the band gap. The electron looses energy, drops to the band gap in the forbindden region. If a hole then moves to the same energy state before the electron is thermally re-emitted into the CB it can recombine
- ERadiate:electron can recombine throuhg the emission of a phonon
- FAuger: this is a three carrier process. An electron can recombine with a hole in the Vb by trasnfering energy to a second electron. This electron raises up in the cb, then thermalises back down to the edge of the CB
12what are the loss process of pv
- Athe three recombination processes
- Bthe 5 recombination processes
- CSeries resistances
- Dparallel resistances
- Ecurrent losses - collection efficiency of carries at junction
- Ftemp dependance; T = up V=up
- Gtemp dependance; T=up, Voltage = down
- Hlight relfection from surface
- Ishadding of cell by top contacts
- Jincomplete abosprtion of light
13light induced electrons which pass across the band gap constitue an electon current. Which generates a voltage. Electron power is generted by separting the electons and holes at device terminanls. The max voltage is the bandgap of the semiconductor which is why wide gap semiconudctors produce higher voltages
- ATrue
- BFalse
14light induced electrons which pass across the band gap reverse the electon current. Which generates a voltage drop. Electron power is generted by recombining the electons and holes at device terminanls. The max voltage is the bandgap of the semiconductor which is why wide gap semiconudctors produce higher voltages
- ATrue
- BFalse
15What are the four main PN junctions and which is the corresponding image
- APN
- BPIN
- CSchottky Barrier
- DHeterojunction
- EPN
- FPIN
- GSchottky Barrier
- HHeterojunction
- APN
16How does a semiconductor junction work
- AJunction generate a weak electric field
- BJunction generate a strong electric field
- CAn electric field drives electrons and holes in the same direction
- DBetween two semiconductors, n-type electrons near interface cross to p-type side, leaving a positively charged area
- Ethis creates an interfacial potential barrier with multiple mobile charges, creating flow of more electrons and holes through the barrier / depletion zone
- Fp-type holes transfer over to n-type side leaving a negatively charged area
- GBetween two semiconductors, p-type electrons near interface cross to n-type side, leaving a positively charged area
- Hthis creates an interfacial potential barrier with no mobile charges, prevent the flow of more electrons and holes through the barrier / depletion zone
- IBetween two semiconductors, n-type electrons near interface cross to p-type side, leaving a negatively charged area
- JAn electric field drives electrons and holes in opposite directions
17Biasing junctions
- Athere is a current at equilibreum
- Bthere is no current at equilibreum
- Creduced barrier height occurs under reverse bias (V= applied to p-side) increases current through diode
- Dreduced barrier height occurs under forward bias (v+ is applied to the p-side) increases the current through diode
- Ereverse bias increases barrier height and current becomes negligible
- Freverse bias reduces barrier height and current becomes negligible
18Tick the correct circuit descriptions
- AThe short-circuit current ISC through the solar cell occurs when
the voltage across the cell is zero. ISC is due to the generation and collection
of light-generated carriers - BThe short-circuit votage VSC through the solar cell occurs when
the voltage across the cell is zero. ISC is due to the generation and collection
of light-generated carriers - CThe closed-circuit voltage, VCC is the maximum voltage available
from the cell, occurring at zero current. Corresponds to the amount of forward
bias on the solar cell due to the bias of the solar cell junction with the lightgenerated
current. - DThe open-circuit voltage, VOC is the maximum voltage available
from the cell, occurring at zero current. Corresponds to the amount of forward
bias on the solar cell due to the bias of the solar cell junction with the lightgenerated
current. - EThe "fill factor", ("FF”) is a function of Voc and Isc, which determines the
minimum power. FF is the ratio of the maximum power to the product of Voc and
Isc. Graphically, the FF is the area of the largest rectangle which will fit in the IV
curve. - FThe "fill factor", ("FF”) is a function of Voc and Isc, which determines the
maximum power. FF is the ratio of the maximum power to the product of Voc and
Isc. Graphically, the FF is the area of the largest rectangle which will fit in the IV
curve. - GIncreasing T reduces the Eg, which can be viewed as increasing the energy of
the electrons in the semiconductor. Less energy is needed to break the
bonding - reduction in the bond energy also reduces the band gap. VOC is most
affected by an increase in temperature - Hreducing T reduces the Eg, which can be viewed as increasing the energy of
the electrons in the semiconductor. Less energy is needed to break the
bonding - reduction in the bond energy also reduces the band gap. VOC is most
affected by an increase in temperature
- AThe short-circuit current ISC through the solar cell occurs when
19What are the three types of solar cells
- ADiffusion: n-type and p-type are aligned by the Fermilevel. photon absorption provides the energy to create an e-h pair. the junction allows the pair to be separated and
diffused to the external
circuit - BReffusion: n-type and p-type are aligned by the Fermilevel. photon absorption provides the energy to create an e-h pair
- CLift: there is an intrinsic gap where the photon is absorped in and casusest eh electonr hole pair to form. The elctron rises up to the top and drift downards to teh n-type
- DDrift:there is an intrinsic gap where the photon is absorped in and casusest eh electonr hole pair to form. The elctron rises up to the top and drift downards to teh n-type
- EExothermic: electron hole pair splits because photon is absored by the dye molecule. The electron passes into the TiO2 and flows around the circtuin.
- FExcitonic: electron hole pair splits because photon is absored by the dye molecule. The electron passes into the TiO2 and flows around the circtuin.
- ADiffusion: n-type and p-type are aligned by the Fermilevel. photon absorption provides the energy to create an e-h pair. the junction allows the pair to be separated and
20Conustrction of a tendem cell
- Atop cell has a small bandgap
- Bmiddle cell has a mid eV bandgap
- Ctop has a large bandgap
- Dbottom has a large band gap
- Ebottom has a small bandgap
21Components of a PV system
- Acell
- Bmodule
- Carray
- Dcell, moudule, array
- Elead acid rechargable battery
- Fcapacitor
- Ginverter
- Hac - dc converter
- Ipower monitoring system
- JGalo
22what does a charge controller is/does
- Achrarge controllers damage batteries ensuring they overcharge and undercharger
- Bcharge controllers protect batteries from overgcharge and or excessive discharge
- Ckeeps the pv system array connected even when the batteries fully charged
- Ddisconnects teh PV array when the battery is fully charged
- Edesigned for lead acid batters
23Inverters
- Achange AC to DC
- Bchanges DC to AC,
- Cswitching the polarity of the
DC with the frequency needed for AC (50 Hz or 60 Hz), using devices called rectangular
inverters. State-of-the-art technology at inverters is PWM (pulse width modulation).
Here DC is switched on and off for a short period of time (a pulse) in such a manner that
the integral of the pulse is equivalent to the actual level at the sinusoidal profile
required
24Standalone Pv systems consict of
- APV arracy = cells- module - array
- BDC disconnect
- Ccharge controlelrs
- DBattery bank
- EDC load
- FDual function inverter
- GBattery
- HBackup AC circuit
- IInvertor
- JAC load
25Grid-tied PV systems consist of:
- APV output
- BDC disconnect
- Ccharge controller
- Dbattery bankg
- Edual function inverter
- FAC disconnect
- GBack up AC circuits
- HAC disonnect
- IBackup loads
- Jexisting ac distribusion centre to electricity utility
26Name three assumptions from the Betz limit momentum theory
- AAssumes there is a variation in tangential velocity along blade length
- BAxial incompressible flow
- Caccounts for a tangential indiuced flow
- DInfinite number of blades
- Eaccounts for the components of lift and drag due to cross scection area of blade
- Fsteady undistrubed flow down stream of turbines
27Pick three environmental impacts and mitigation techniques
- ANoise issues: keep the turbine distance from the residential area 2) improve design of the turbine blade, including the shape, add-ons and low noise control method
- BElectromagnetic interference: Keep the distance from the electronic source 2) design different shape/height of the tower, 3) use different material to reduce the reflection
- CAviration related issues: keep the farm away from the flight route, airport and terminals 2) use Surveillance Radar monitoring the farm 3) keep air traffic controller informed 4) re-route the flight or limit the air
traffic volume.
28differential solar heating of the Earths surfaces causes variations in atmosphere pressure, and leads to the movement of air masses as the principle of Earths wind systems
- ATrue
- BFalse
29air flow is driven from high pressure to low pressure areas
- ATrue
- BFalse
30wind is influenced by terrain and shapes the terrain in turn
- ATrue
- BFalse
31The wind is:
- Avery unpredictable in magnitude and direction
- Bwhich is very stable in magnitude and direction
- Cwind decreases with height
- Dwind shear: increase of wind speed with height
- Ewind speed and direction affected by heat
- FTerrain causes turbulence
32Advanteges of wind turbines
- Afree and renewbale
- Bnot been used for many centuries therefore an unreliable technology
- Chas been used over many centuries therefore is a proven technology
- Dwind technology is good as the wind is intermittenet
33disadvantages of wind energy
- Awind is intermittent and unsteady in speed and direction
- Bit has a very low energy density and uses a large surface area
- Cnoise and vibration from wind turbines
- Dvisual intrusion by wind turbines
- Einitial construction and subsequent maintenance cost
34Advatages/disadvantages off onshore turbines
- Aeasy to access for construction and maintenance
- Bcorrosive environment
- Ceasy to connect to the grid
- Dwind quality is poor
- Eland use and corresponding envionrmental issues
- Fintrusion of shipping lanes
35VAWT is at present more economically viable than HAWTS. However they undergo greater cyclic loading than HAWTS
- ATrue
- BFalse
36Solidity is used to describe the fraction of the swept area that is solid (blade)
- ATrue
- BFalse
37Multi-blade turbines have high solidity rotors
- ATrue
- BFalse
38modern electricity generating wind turbines have low solidity rotors
- ATrue
- BFalse
39Turbine knowledge
- ATo extract energy efficiently, the blades need to interact with wind as much as possible through the rotor’s swept area.
- BHigh-solidity multi-blade wind turbines interact with all wind at very low tip speed ratio.
- CLow-solidity turbine have to travel fast to ‘virtually fill up’ the swept area to interact with wind passing through.
- DOptimum tip speed ratios for modern low-solidity turbines range between 6-20.
- EHowever, large number of blades can interfere with air flow and cause much stronger turbulence, hence reduce the efficiency of the turbine.
40Air streams flow faster above the airfoil than air stream underneath. Therefore there is a higher pressure underneath than the above and a higher pressure at the front than the rar. This creates a upward and downstream force. The anlge between the chord line and wind direction is the angle of attack
- ATrue
- BFalse
41Relative wind velocity is the resultant of the wind velocity at the rotor and the tangential velocity vector of the blade.
- ATrue
- BFalse
42The assumptions for a turbine flow are:
-infinte number of blades
-axial incompressible flow
-massless rotor
-undisturbed, steady flow down stream- ATrue
- BFalse
43-The relative wind angle progressively increases towards the hub
-The tangential speed decreases towards the hub#
-HAWT blade for optimum performance will have a tapered blade
-To have a constant angle of attack, the blade will have to have built in twist- ATrue
- BFalse
44Blade stall occurs:
- due to the wind speed increases
- causing the tip speed ratio to decrease
-Relative wind angle increases, casuing an increase in angle of attack
-results in a loss of lift and torque on blade regions in stall
-stall regulation is used on HAWT rotors to regulate the turbine during high wind- ATrue
- BFalse
45Structure and components:
-blades are made from composite materials i.e. carbon of glass fibre
-they are twisted, tapered and hollow for large turbines
-they can be solid, untwisted for small turbines
-turning the blade along its length increases turbine efficiency- ATrue
- BFalse
46Picking the rated potential of the turbine is important as:
- AIf the rated speed is too low, at a very energetic site too much energy will be lost in high winds.
- Bif the rating is too high, performance at a less energetic site will suffer.
- CPicking a rated speed is as much an art as a science, because gearboxes and generators are not manufactured in continuous increments. There are only discrete sizes available
47Causes of mechanical nosie
- Ainflow turbulence
- Btip noise
- Ccaused by gearbox
- Dgear less turbines are quieter
48How to reduce wind tubrine noise
- Achange blade shape
- Bblade add-ons
49fission is the action of splitting or being split into two or more components. Can occur naturally or be neutron induced.
- ATrue
- BFalse
50Nuclear fusion is the process of fusing to smaller nuclei to form a heavier nucleous. Requires high temperature and pressure
- ATrue
- BFalse
51Fissile means that an element can undergo fission
- ATrue
- BFalse
52not all elements of fissile. Some are fertile but can trans-mutate into a element that is fissile.
- ATrue
- BFalse
53Select reactors that exist
- AWPR
- BPWR
- CGBK
- DRBMK
- EBWR
- FNOXMAG
- GMAGNOX
- HAGR
54What are the main decay methods
- AAlpha: ejection of a He nucleus
- BBeta: ejection of an electron from a neutron and conversion to a proton
- CGamma - electromagnetic wave from nucleus
- DBeta+/positron - ejection of anti-electron (positron) conversion of a proton to a neutron
- Eelectron capture - capture of an electron from orbitals
55There are 358mg of potassium in a 100 gram banana
- ATrue
- BFalse
56What is binding energy
- AEach atomic nucleus contains energy (binding energy) which can be thought of as the energy pushing the nucleus apart
- BEach atomic nucleus contains energy (binding energy) which can be thought of as the energy keeping the nucleus together
571 amu = 931.5 MeV
- ATrue
- BFalse
58mass of a proton is 1.008665
- ATrue
- BFalse
59fission takes advantage of instability within the atom nucleus.
- ATrue
- BFalse
60what is needed for a fission reactor to work?
- Aair
- Bdiesel
- CTransparency of neutrons
- Dmoderation of neutrons (ideal - not required)
- EEnrichment - desirable, but not required if other conditions met
61Where was the first terrestrial reactor
- AOkla / Bangombe
- BWales
- CUranium mine - Gabon, central afirca
- D1972
62First technical reactor , what did it consist of
- AWales Pile 1
- BChicago Pile 1
- Cgraphite core
- Dencased in a ballon of C02
63Advantages and disadvantges of Thorium Fuel Cycle
- ACan use Pu/U/MA as initiators
- BHigh efficiency and more economical extraction
- CNo enrichment needed
- Dproposed higher burn of fuel
- Erequires an initiator
64What should be considered when building reactors
- Ageology - must be able to support reactor complex
- BGeography - supply of cooling water, space to build, isolated location
- CTransport - need to be able to handle transport flows of material and people
- DEconomic - must have the ability to support materials and people required for the operation
- EElectricity - needs to be able to connect to the grid
65Three mile island and The windscale fire were two major disasters
- ATrue
- BFalse
66What is the cladding, fuel, cooling, moderation and core temperature of an AGR
- ACladding : stainless steel
- BCladding: zirconium
- CFuel: enriched
- DFuel: not enriched
- ECooling: H20
- Fcooling: C02
- Gmoderation: graphtie
- Hcore temperature: 640 degrees C
67PWR properties
- ACladding : zircaloys
- BFuel: enriched
- CCooling: H20
- DModeration: light water
- ECore temperature: 310-320 degrees c
- Fcore pressure: 150-160 atm
- Gtwo cooling circuits: primary = water, secondary = water.steam
68BWR
- ACladding: zircalloys
- BFuel- enriched
- CCooling: H20
- Dmoderation: light water
- Ecore temp: 280-290 degrees C
- FCore pressure: 75 atm
- Gone cooling circuit: primary - water/steam
69Pick the correct reactor
- APWR
- BBWR
- CRBMK
- DMAGNOX
- EAGR
- FPWR
- GBWR
- HRBMK
- IMAGNOX
- JAGR
- APWR
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- Quiz on EE quiz, created by Tom Piggott on 29/05/2017.
- Author
- Tom Piggott
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