Hydroelectric And Geothermal Energy

Question 1

What is the historical development of hydropower?

Answer 1

Hydropower has been existence for decades. They began as water wheels used to mill and operate machinery . These water wheels have now evolved over time to the machines we have now . The turbines have evolved drastically and now have an efficiency of about 90%

Question 2

How does a hydroelectric system work ?

Answer 2

Flowing water is directed at turn phones turning and turning kinetic energy into mechanical energy. The turbine is connected to a generator which converts this mechanical energy into electrical energy.

Question 3

How much electricity can be generated by a hydropower plant?

Answer 3

Power = efficiency *height(m) mass flow rate (kg/s)acceleration (m/s2)
The greater the water flow and head the more electricity produced .
Power production is directly proportional to river flow rate and head
Efficiency 60-90%

Question 4

How to convert m3/s to kg/s

Answer 4

If you are asked to convert say 24000 m3/s to kg/s
Insincere it’s flow rate we know water has a density of 1000kg/m3
So then 24000m3/s x 1000kg/m3= 24000000kg/s

Hydropower = efficiency height(net head)m flow rate kg/s *acceleration due to gravity (9.81m/s2)

Solve the question hydropower on slidec7

Question 5

What is a low head hydropower plant?

Answer 5

This is a power plant where the height of the water fall is fairly low .

Question 6

What is a highhead hydropower plant?

Answer 6

This is a plant where the water fall height is high

Question 7

What does the low head hydropower have over the high head ?

Answer 7

The low head hydropower has lower emissions

Question 8

Types of hydroelectricity, what are they ?

Answer 8

Run of the river hydroelectricity and tidal power .

Question 9

What do you know about run of the river hydroelectricity?

Answer 9

This scheme uses the rivers natural flow and does not require any impoundment.
A part of the river may need to be directed to a separate canal
The turbine may have to be placed right in the stream

Question 10

What do you know about tidal power?

Answer 10

This is the only technology that relies on the gravitational pull between the moon and the earth . It relies on ocean tides that are influenced by gravitational pull of the moon.

It a low head hydropower
The costs will have to reduce to make it compatible to set goals.

Question 11

Environmental impact’s of high head hydropower

Answer 11

Although this plant produces high amount of energy and is essentially pollution free to operates . tHey also have negative impacts

The cause decline in fish populations
They cause upstream flooding
The threaten endangered species protection
Reduce the quality of upstream and downstream environmental conditions
They decrease water quality flow.

Question 12

Some considerations about hydropower

Answer 12

It is the largest renewable energy resource world wide
The pumping water up a hill to be pumped back down at a later time when need known as the “pumped storage hydropower” is considered as 90% of the worlds energy storage capacity.
Hydropower is being used more in developing countries than developed countries
Existing hydropower maybe affected by climate change and change in precipitation.

Question 13

What is geothermal energy ?

Answer 13

This is energy made from the earth itself . From pressure and heat over time .

Question 14

History of geothermal energy .

Answer 14

This has been used for thousands of years for heating and cooking but has a much shorter history compared to hydropower. Until 1958 Italy was the worlds only geothermal energy producer , then in the 1950!s and and 1960’s New Zealand, USA and the Philippines followed .

Question 15

What are Geothermal reservoirs?

Answer 15

These are places in the earth where hot water and steam are trapped in a rock.
These reservoirs are found in areas where we find volcanoes, seismic activity, hotsprings and boiling mud pots.

Question 16

How does geothermal electricity generation work ?

Answer 16

Holes are drilled into the hot underground reservoirs, the heat is then extracted to the surface where turns turbines producing mechanical energy , this energy is then converted into electrical energy by generators.

Question 17

What are the types of geothermal power plants

Answer 17

There are three types of geothermal power stations:
Dry steam plants
Flash steam plants
Binary cycle plans

Question 18

How do dry steam plants work ?

Answer 18

These plants extract steam directly from underground resources to be transferred up to turn turbines and generate electricity.

These are fairly easy to build but cannot be built anywhere because they are rare and are only available in Italy and California.

Question 19

How do flash steam plants work?

Answer 19

These plants draw steam from water heated by Heat from an underground reservoir . The steam is separated s transferred up and used to turn the turbines.

This is the most commonly used plant type.

Question 20

How do binary cycle plants work?

Answer 20

These stations transfer heat from geothermal hot water , this heats up another liquid producing steam , which is then transferred up to turbines”

Question 21

Geothermal thermal energy for residential heating and cooling ?

Answer 21

A hole is drilled underneath a house like is done for a well 150 - 200m deep.then a heat pump is installed, the heat pump has two parts :the heat pump unit that is installed in your home and then the buried ground loop that consists of pipes buried underneath your home . These pipes use some form of water source (usually a pond or a well) to draw heat from under ground into your home and for cooling they draw heat from your home into the ground.

Question 22

What is a geothermal heat pump ?

Answer 22

This is a heating/ cooling system installed in buildings that transfers heat to and from the ground, taking advantage of the relative constant temperature of the earth despite seasonal changes.

For a heat pump to work efficiently there must be hot and cold water . The temperatures must not be that high what matters is the temperature difference. The uses a compressor to ensure optimum temperature difference necessary to heat or cool the home.

Question 23

What are some Advantages ?

Answer 23

No fuel needed
Always available
V very little space needed to set up a power station
Once a power station is set up energy costs and environmental impacts are very low.
Heat pumps combined with geothermal energy are very viable options for residential cooling and heating in many buildings.

Question 24

What are some disadvantages?

Answer 24

Limited places where geothermal stations can be set up.
Some times a site may run out of steam

Question 25

Environmental impacts of geothermal sites

Answer 25

Manufacturing and installation requires a lot of resources.
May potential cause emissions of toxic substances like CO2,CH4,Hg,As etc to the surface when using steam directly.
May cause land instability and sometimes seismic activity increase

Question 26

Where is geothermal energy mostly found?

Answer 26

Heavily in USA, Russia,a minute part of Africa, New Zealand,some parts of Asia.