Lec 7 Flashcards
Define active solar techniques
it involes use of PV systems, concentrated solar power and solar water heating
(PV, solar power, solar heating)
passive solar techniques are
orientation of a building towards sun, materials favorable with favorable thermal mass and light-dispersing properties, spaces with ability to naturally circulate air
How much energy is reflected by the Atmosphere?
174 petawatts is thrown at earth, 30% is reflected, and the remaining is absorbed by oceans and clouds and land masses
3 source of absorbing light
ocean, clouds, land masses
what is Photovoltaics?
conversion of light into electricity using semiconductors like crystalline silicon
Before silicon can be cut into thin … it has to be …
wafer - purified
Three different solar configurations
Grid-tied, off-grid, hybrid
off-grid only
relis on battery
grid-tied systems are
connectd to the utility grids
hybrid systems
can store power when needed and have access to the grid when there aren’t enough sunlight or poor weather or peak power usage
two names for hybrid pv systems
utility backup power or grid-tied solar with extra battrey storage
what is power inverter?
current generated by PVs are DC (direct current) and low voltage. to convert them to alternating current AC (110-220v) we use inverters.
design decisions for a hybrid system
size of system, battery capacity
Design procedure for PVs
- system size based on demand
- cost-benefit analysis
- optimize system to achieve high ROI
whats the capacity of small-scale wind power?
upto 50kWh
Geothermal is the energy
generated and stored in earth. with an temperature upto 4000 celcius (7200 F)
What is the supply per deep geothermal well?
3.5kW
Shallow ground temperature is between … and …
50F and 60F (10 - 16 C)
Geothermal pumps can be used to
- cool buildings
2. heat bldgs
a geothermal heat pump consists of
- heat pump
- air delivery (ductwork)
- heat exchanger system
geothermal can be used for electricity generation
- steam used to turn turbines/generators
2. boil and vaporize working fluid to turn a turbin
how biogass is generated?
decomposition (breakdown of organic) material when there is no oxygen
some materials used to generate biogas
manure, municipal waste, sewage, green waste or food waste, agricultural waste, plant material
why not use refrigerant?
reduce ozone depletion and comply with the montreal protocol
