Use LEFT and RIGHT arrow keys to navigate between flashcards;
Use UP and DOWN arrow keys to flip the card;
H to show hint;
A reads text to speech;
55 Cards in this Set
- Front
- Back
|
How does the total amount of solar power incident on Earth compare with the consumption rate of our own society? |
World consumes: 15 TW & Incident on Earth: 174,000TW |
|
|
How long can solar power last? |
30 million years |
|
|
What is a solar constant? |
intensity of solar radiation incident |
|
|
What is solar insolation? |
intensity of solar radiation projected onto the Earth's surface |
|
|
How does the global average solar insolation compare with the solar constant? |
The solar constant stays the same while the solar insolation does not. |
|
|
what is direct insolation? Diffused insolation? |
Direct: solar energy comes directly from the sun Diffuse: solar energy that also comes through the sky |
|
|
What factors determine the solar insolation? |
could cover, atmosphere scattering, geography |
|
|
What factors affect the solar insolation at a given geographical location? |
could cover, atmosphere scattering, geography |
|
|
What is the solar insolation under ideal lighting conditions? |
1000 w/m^2 |
|
|
What is the electromagnetic composition of solar energy reaching upper atmosphere? |
Infared (47%), Visible (46%), UV(7%) |
|
|
What is the difference between active solar heating and passive solar heating? |
Active: use pumps or fans Passive: relies on certain things, Nothing mechanical |
|
|
What are the four essential elements in the passive solar heating systems? |
Collection of solar energy through large south-facing glass. High R-Value. Solar design must promote distribution of energy. |
|
|
What is concentration ratio? What kind of reflector has the best ratio? |
Concentration ratio: Ratio of concentrated sunlight to direct sunlight intensity Flat-pole collectors have the best concentration ratio |
|
|
What is a Stirling Engine? |
heat engine powered by compression of air or other gases |
|
|
What a power towers? Heliostats? |
Power tower: Solar thermal plant that uses a field of heliostats. Heliostats: flat sun tracking mirrors to focus sunlight on an object |
|
|
What are solar chimneys? |
Solar heat trapped inside a transparent cage which heats the air inside the cage |
|
|
What is a semiconductor? Give an example |
Class of materials properties between conductors and insulators. In metal, charge carriers are free electrons |
|
|
What are the dopants that give rise to N-type semiconductor in silicon? |
Silicon doped with pentavalent impurities. (Phosphorus or Arsen) |
|
|
What are the dopants that give rise to P-type semiconductor in silicon? |
Silicon doped with tri-valent impurities. (Born of Gallium) |
|
|
What is a P-Type semiconductor? N-type? |
P-type: Phosphorus or Arsenic N-Type: Boron or Gallium |
|
|
What is a PN junction diode?
|
Join P+N type semiconductors causes electrons to diffuse across the junction into P-type material and holes into N-type material |
|
|
What is band gap theory? |
Minimum energy required to eject an electron from the crystal |
|
|
What factors determine the efficiency of solar panels? |
Distribution at lengths in the solar radiation Difference between band gap energy and photon energy Reflection Recombination before junction |
|
|
What is photolysis? |
Use of solar radiation to break water into oxygen producing clean hydrogen fuel |
|
|
What is the energy payback time of solar panels |
2 years |
|
|
What fraction of indirect solar energy production in the US is in the form of hydropower and wind power? |
24% |
|
|
Which countries generate most their electric power requirements through hydroelectric power installations? |
Congo (100%) and Norway (97%) |
|
|
What is the hydrological cycle? |
Evaporation, precipitation, and return flow
|
|
|
What factors determine the total power in a hydropower system? |
Volume flow rate and pressure head determine the total power |
|
|
Is the energy in hydropower systems one of high quality or low quality? |
Hydropower systems produce the highest quality energy |
|
|
What are the environmental impacts of hydropower plants? |
Large reservoirs have limited lifetimes (50-200 years) Catastrophic failure of dams lead to massive life loss Green house gas emissions |
|
|
What is the main advantage of hydropower plants and why do the electric power grids depend on them? |
Energy can be generated instantaneously |
|
|
How does the wind power change with wind speed? |
As wind speed increases, so does wind power. |
|
|
Why is ind power not reliable? |
Wind is not a constant |
|
|
What are the two kinds of wind turbines? |
Horizontal and Verticle |
|
|
What is the Betz Power Coefficient? What is its value? |
59% is the max power for any wind turbine. (Horizontal 45% Vertical 30%) |
|
|
What are the environmental impacts of wind mills? |
Not very much besides land in its place |
|
|
What is electricity? |
A form of energy that results from the interaction of charges particles, such as electrons or protons |
|
|
What is primary energy source from which most of the electricity is generated in a: US, b: France |
a: Fossil b: Nuclear |
|
|
What are two types of electric power grids? What is the advantage of AC power grids? |
AC/DC Ac is better because you can rapidly change the voltage |
|
|
What is voltage? Ampere? Ohms? |
Voltage: Provides "push" electrons through wires Ampere: SI unit of current Ohms: SI unit of resistance |
|
|
What is Ohnm's Law? |
With a given voltage cross conductor you get greater resistance and lower currency. |
|
|
To minimize transmission loss, should the long distance transmission be of high voltage or high current? |
High Voltage |
|
|
What is a transformer? What principle does it employ? |
Household appliances that use 120V. Used to step up or down voltage |
|
|
What is a step-up transformer? Step-down transformer?
|
Step-up: 2x primary voltage Step-down: 1/2x primary voltage |
|
|
Why is chemical hydrogen not an energy source?
|
Chemical hydrogen is a carrier |
|
|
Why is there no hydrogen energy source on Earth? |
Earth doesn't have the necessary gravitational pull to keep it close |
|
|
What are the four methods for hydrogen production? |
Steam reforming Electrolysis Thermal splitting Photolysis |
|
|
What is the main application of hydrogen today? |
Steam reforming |
|
|
What is steam reforming? |
Steam reacts with natural gas. Most common. |
|
|
What is electrolysis? |
Electric current in water separates hydrogen and oxygen |
|
|
What is thermal splitting? |
Hydrogen and oxygen in water molecules are pulled apart at very high temperatures; can be made in high temperature nuclear reactors or solar towers |
|
|
What is photolysis? |
Solar photons create electron hole pairs in a semiconductor |
|
|
What is the theoretical maximum efficiency for hydrogen fuel cells? |
83% theoretical limit of efficiency |
|
|
What is the energy density when hydrogen is used as a chemical fuel? |
Liquefaction takes 40% of the energy |
