3 types of energy
1. direct solar energy 2. indirect solar 3. non-solar renewables
direct solar energy
1. solar heating (water and space) 2. Sunlight to electricity (photo-voltaic cells through collectors)
indirect solar
biomass, biofuels, windpower,hydropower
non-solar renewables
geothermal, tidal & wave power, and nuclear fussion
steps for photo cells to get energy
1. photons that hit a solar cell are absorbed by semiconducting material (silicon) 2. negative electrons are knocked loose from atoms allowing them to flow through material to produce electricity
in photo cells due to special composition of solar cells, the electrons are only allowed to move
in one direction from one layer to the other
in photo cells a charge imbalance builds forms that can be restored
as a current (DC) electricity
an array of solar cells convert solar energy into
a usable amount of direct current(DC) energy
current maximum efficiency of photo cells
wind and hydropower
directional wind motion converted into rotational motion, and thence into electrical energy
in hydropower water power drives what?
a turbine
wind and hydropower currently provides ____% of us electricity
there is potential growth in wind energy but not in
geothermal source
steam drives conventional turbogenerator
tides as a non-solar source of energy
tidal motion drives turbines
nuclear fusion
het of elemental fusion converted to electricity by a steam turbogenerator
there ____ (is/isn’t) promise in nuclear fusion
5 disadvantages of renewable energy
1. limited availability 2. not a predictable source 3. more expensive than FF energy 4. has negative environmental effects 5. experimental requires more research
2 advantages of renewable energy
1. clean, sustainable source of heat, electricity 2. can help reduce demand for fossil fuels
all renewables combined supply ___% of energy world wide
electricity from solar/wind is _____ expensive than electricity from Fossil fuels
recent growth in use of renewables is due to
government interest
the government does these three things to encourage renewable energy
give subsidies, mandates and tax incentives
who are the biggest promoters of renewable energy?
older industrial economies (Europe, Japan, and US)
one reason the gov. is trying to look into renewable energy is because
they are trying to reduce carbon foot print because global warming perceived as larger threat that FF depletion
many conclude that renewables ________ be able to fully replace FF’s
will not