ocean

Question 2

types of ocean energy

Answer 2

tides, waves, currents, thermal gradients, salinity gradients

Question 3

types of energy ocean

Answer 3

kinetic, thermal, chemical

Question 4

types of tidal systems

Answer 4

tidal barrage systems, tidal current systems

Question 5

what drives tidal ranges?

Answer 5

the gravity of the moon; basin shapes affect waves, so tidal height varies; bays that act as funnels have high tides

Question 6

tell me about the oldest barrage power plant in the world

Answer 6

sluice allows tidal basin to fill when tide comes in; electricity generated when water leaves; need strong tides; negative effects on habitat and estuaries

Question 7

turbines used in tidal generation

Answer 7

bulb turbine–older, all elec equip kept in bulb underwater (hard for maintenance); rim turbine–generator is above water; tubular turbine (newer)–generator and gearbox are abox water (maint advantages)

Question 8

tidal turbines

Answer 8

sensitive–only need 2-3m/s current; very experimental

Question 9

tidal fence power gen

Answer 9

electrical equip above the water; decreasing cross section of channel increases velocity through turbines

Question 10

tidal energy drivers

Answer 10

known technology; predictable supply; marketable; clean operations; minimized risk via shared research

Question 11

tidal energy barriers

Answer 11

some approaches unproven; limited dispatchability; site-specific; cost!; environmental (like dams)

Question 12

wave energy

Answer 12

harness the kinetic energy in waves–lots of potential

Question 13

three types of wave energy

Answer 13

wave surge/focusing: shore-mounted structures sens waves into a reservoir to gen elec, oscillating: rising/falling water column drives air past a turbine, floats or pitching devices: gen elec from bobbing/pitching of a floating object

Question 14

wave surge systems: tapered channel

Answer 14

tepered channel feeds reservoir; narrowing of channel makes waves bigger and spill into reservoir above sea level; stored and released to power turbine

Question 15

wave surge systems: floating wave power vessel

Answer 15

floating platform shifts to accommadate waves–waves spill into basin, power turbine; not yet commercial

Question 16

floats or pitching: semi submerged, articulated structures

Answer 16

cylindrical sections linked by hinges; wave-induced motion of each joint is resisted by pumps that power generators

Question 17

submerged oscillating devices

Answer 17

based on swaying motion of sea plants in presence of waves

Question 18

wave energy drivers

Answer 18

supply magnitude; modular; predictability; clean operations

Question 19

wave energy barriers

Answer 19

supply location; uncertain technology; intermittency; cost; environmental(habitat, visual, navigational)

Question 20

energy from ocean currents

Answer 20

preliminary research phase–nothing commercial

Question 21

ocean current technical challenges

Answer 21

cavitations, marine growth buildup, reliability, corrosion

Question 22

ocean current environmental considerations

Answer 22

species protection, shipping routes/recreational uses, risks of slowing current flow, changes to estuaries affecting species there

Question 23

OTEC

Answer 23

ocean thermal energy conversion: uses oceans natural thermal gradient (layers of water have diff temps) to produce power

Question 24

what temp differential do you need for otec?

Answer 24

temperature differential of 20 deg C (don’t need to convert to kelvin this time)

Question 25

closed cycle OTEC

Answer 25

rankine cycle; warm seawater vaporizes working fluid, vaporizes and powers turbine and is then cooled by cold seawater from deep below

Question 26

open cycle OTEC

Answer 26

uses warm surface water as working fluid--is vaporized in vacuum--drives turbine; the vapor also loses its salt and ends up FRESH; vapor is cooled by deep cold water

Question 27

pros/cons of open cycle

Answer 27

pros: desalinated water! Cons: losses in vacuum/condenser, less proven electricity prod

Question 28

pros/cons of closed cycle

Answer 28

pros: tested, more efficient. Cons: potential harm of ammonia on marine ecosystem

Question 29

Benefits of OTEC: mariculture and agriculture

Answer 29

OTEC brings nutrient rich water to surface, creating upwelling that_s good for organisms; fresh water for agriculture is good, cold water allows new crop development, etc

Question 30

OTEC vs conventional desalination

Answer 30

OTEC would produce less freshwater; OTEC would have credit for water, while conventional would cost; OTEC generates elec, conventional uses it; OTEC renewable, conventional is cheaper.

Question 31

OTEC drivers

Answer 31

abundant supply; baseload power; freshwater; food; cooling; clean operations

Question 32

OTEC barriers

Answer 32

site-specific; cost; materials requirements; biofouling; efficiency; environmental

Question 33

salinity gradient energy

Answer 33

aka osmotic power, uses energy retrieved from difference in salt conc between sea and river water

Question 34

types of salinity gradient energy

Answer 34

reverse electrodialysis: salt battery; pressure retarded osmosis: harness osmotic pressure w/semipermeable membrane; vapor compression: exploits diff in vapor pressure; hydrocratic generator exploits density differences

Question 35

future outlook for ocean energy

Answer 35

huge potential resource but very speculative and many regulatory hurdles.