future of energy supplies- renewable energy

Question 1

outline the problematic properties of solar power

Answer 1

1) intermittent= availability and intensity varies daily and seasonally
2) reliability- daily and seasonable cycles can be predicted but changes in intensity caused by cloud cover cant be
3) energy density is low and requires large areas of solar collectors to harness significant energy
4) locational constraints- can be used anywhere in the world but most viable in areas of high light intensity such as dry desserts

Question 2

how is solar power currently harnessed

Answer 2

1) photothermal solar power- absorb sunlight to produce heat usually to heat water for space heating or domestic purposes. Heat harnessed is retained in a thermal store for later use such as a well insulated tank
2) photovoltaic solar power- pv cells absorb photons of light and electrons become dislodged on the upper surface so it is more negative, they move towards the more positive secondary layer and the movement generates electricity

Question 3

what are the environmental impacts of solar power

Answer 3

1) the manufacture- making solar panels requires extraction and processing such as metals and plastic which produces toxic wastes which may harm the enviornment
2) impacts during use don’t require much maintenance but they occupy large areas of land which could be used for other purposes

Question 4

outline what HEP is

Answer 4

1) hydro-electric power

- the gravitational potential energy of rainwater landing on uplands is harnessed as kinetic energy as it flows downhull

Question 5

outline some new solar power technologies

Answer 5

1) multi-junction photovoltaic cells- absorb different wavelengths of light so a greater amount of available light can be converted into electricity
2) heliostats- alters the angle of solar panels so that it is always at the optimum angle for absorbing sunlight
3) self-cleaning panels- allow maximum light absorption
4) transparent PV cells- can be incorporated into windows

Question 6

what are the locational constraints of HEP

Answer 6

1) large water catchment area
2) high total rainfall
3) suitable topography- narrow exit large basan
4) no serious land-use conflicts

Question 7

what are the environmental impacts of HEP

Answer 7

1) reservoir creation- material extraction, habitat change, loss of wildlife, wildlife barrier
2) impacts on the river- sedimentation reduces turbidity downstream, changes in river flow, increased turbidity

Question 8

outline some new HEP technologies

Answer 8

1) water wheels- less efficient than turbines but don’t suffer screen blockages
2) helical turbines- turned by water flowing down the screw to generate electricity, can use water with high turbidity without being damaged
3) low head turbines- when water drops a shorter distance allowing to be used in new locations

Question 9

how is wind power currently harnessed

Answer 9

1) HAWTS- horizontal axis wind turbines

2 )VWATS- vertical axis wind turbines

Question 10

what are the advantages and disadvantages of HAWTS

Answer 10

+
tech is more advanced and established, higher efficiency than VAWTS

-
stress cracking can occur at the base of blades
taller towers need blade above gorund

Question 11

what are the advantages and disadvantages of VWATS

Answer 11

\+ 
can be driven by wind in any direction 
no need for a motor
quite than HWATS
operate at lower wind velocity 

-
no large VWATS have been built
lower efficiency blades

Question 12

what are the locational constraints of wind power

Answer 12

1) wind velocity- reliability and strength is affected by latitude and topography such as costal or upland areas
2) takes up lot of land so land-use conflicts arise
3) public opposition

Question 13

what are the environmental impacts of wind power

Answer 13

1) manufacture and installation
2) noise
3) habitat damage
4) bird deaths
5) bat deaths

Question 14

give some examples of new technology for wind power

Answer 14

1) blade-tip fins= reduce turbulence and wind resistance increasing efficiency
2) Helical VWAT blades- increases the smoothness of rotation which increases efficiency as it prevents stress fractures
3) wind-assisted ships- use wind power to reduce energy provided by the engine
4) nacelle brushes- reduce air escaping between base of blads and central hub increasing kinetic energy absorbed

Question 15

what are the locational constraints of wind power

Answer 15

1) mean velocity of winds need to be high and consistent to increase wave height
2) a long fetch distance allowing waves to build up

Question 16

give some examples of how wave power is harnessed now

Answer 16

1) point absorber= floating structures that rise and fall as waves pass which is attached to a non-moving base on the sea bed, the movement turns a generator
2) surface attenuator wave power- a hinged device which, as waves pass push and pull pistons which force fluid over a turbine generating electricity
3) oscillating water column wave power- rise and fall of water as waves pass forces water up and down in a submerged chamber which causes air to be pushed in and out over turbines

Question 17

what are some design issues with wave power

Answer 17

1) needs to be able to withstand storms and corrosion
2) hard to anchor
3) may be expensive to transport electricity from isolated areas where the energy is harnessed to where it is needed with the consumers

Question 18

what are the environmental impacts of wave power

Answer 18

1) manufacture of equipment and installation

Question 19

what is geothermal power and how is it currently harnessed

Answer 19

1) the radioactive decay of isotopes of thorium, uranium, and potassium releases eat which moves towards the earth’s surface, the heat can be exploited
- low temp scheme such as geothermal springs- groundwater heated by hot springs or geothermal aquifers- hot underground water is pumped to the surface from underground aquifers

• high temp schemes= steam systems where ground water at high temps is brought to the surface using boreholes producing steam to produce electricity
  hot dry rock system- hot rocks near the surface but the absence of hot water, water pumped down borehole to produce steam which is collected and used

Question 20

what are the locational constraints of geothermal power

Answer 20

• a heat source of over 150 degrees is needed
• requires recent volcanic activity
• hot rocks may be too deep to exploit viably

Question 21

what are the environmental impacts of geothermal power

Answer 21

1) infrastructure= can provide obstacles to the movement of large animals
2) gas emissions- hot water extracted from ground can release small amounts of co2 and hydrogen sulfide
3) waste water- water wastes can contain salts and heavy metals

Question 22

outline some new geothermal technologies

Answer 22

low temperature fluids= new turbine technology which can be used to boil and turn turbines at lower temps with water as cool as 60 degrees
this allows lower temp rocks to be used increasing areas which couldnt orginally be used.

Question 23

how is tidal power currently harnessed

Answer 23

1) tidal barrages- a tidal barrage is a dam across from an estuary or bay in which turbines are located so water flowing in or out flows over the turbines making use of maximum tidal flow
2) tidal lagoons- if electricity is being generated but demand is low water can be pumped into a lagoon producing water level higher than sea level. Electricity can then be generated later when demand is higher but there is less tidal flow
3) in stream turbines- fixed to the sea bed and absorb kinetic energy of thr natural tidal flow, has less environmental impacts than tidal barrages or lagoons

Question 24

what are the locational constraints of tidal power

Answer 24

gravitational forces affect all water bodies- if tidal range is large and the mass of moving water is large then it will be viable to use

Question 25

what are the environmental impacts of tidal power

Answer 25

1) materials- large size of barrages needs large amounts of material for construction
2) tidal range change- reduces ease with which water can flow in or out of the lagoons so ow tide level is never as low or high tide quite as high
3) sedimentation= water flow in and out the lagoon is only possible thorugh turbine channels so areas have increased flow which erodes sediments and carries them away where they can be deposited