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7.5 renewable energy- alternative energy sources - Coggle Diagram
7.5 renewable energy- alternative energy sources
solar energy
a building that has enough access to sunlight can get all or most of its heat through a passive solar heating system. this system absorbs and stores heat from the sun directly within a wll insulated airtight structure.
an active solar heatin system captures energy from the sun by pumping a heat absorbing fluid such as water or an antifreeze solution thorugh special collectors.
some of th ecollected heat can be used directly and the rest can be stored in large insulated container filled with gravel, waterm clay or a heat absorbing chemical
we cna use indirect solar energy to help cool buildings.
open windows to take advantage of breezes and fans to keep air moving
when no breeze, superinsulation and high efficiency windows keep hot air outside
a light colored roof can reflect up to 90% of the suns heat
solar thermal systems also known as concentrated solar power (CSP) use different methods to collect and concentrate solar energy to boil water and produce steam for generating electricity
inexpensive solar cookiers to focus and concentrate sunlight for boiling and sterilizing water and cook food.
decreases need for firewood
solar cells for electricity
photovoltaic cells
we can convert solar energy directly into electrical energy using photovoltaic (PV) cells, also known as solar cells
when sunlight strikes solar cells, they produce electricity
pros: solar cells emit no greenhouse gases or poullutants
contain no toxic material
easy to use, low maintenance
cons: low energy efficiency
cant produce electricity at night and storing energy is expensive
researchers have developed a solar cell panle with a built in battery that is 25% less expensive and 20% more efficient than conventional batteries
wind power
wind is air in motion. wind is an indirect form of solar energy
wind turbines can be 60 stories tall and have 70 mt long blades. height makes them stronger and more constant winds are found at higher altitudes. blades spin, turn an electric generator and produce energy
groups of wind turbines are called wind farms and transmit electrical energy to electrical grids
wind power has the potential to produce 40x the world's current
pros: wind is abundant, widely distributed and inexhaustible
carbon free and pollution free
fast and relatively cheap
the turbines themselves only occupy a small portion of land
increasing energy efficiency and reducing costs
smart grid connecting various farms can allow some areas to compensate for other when wind dies down
cons: collisions with turbines kill 234k birds and 600k bats each year
geothermal
geothermal energy is heat stored in soild, underground rocks and fluids in the earths mantle
a geothermal heat pump systems can heat and cool a house almost anywhere in the world. it is the most energy efficient reliable, environmentally clean, and cost effective way to heat or cool a space
hydrothermal reservoirs are deeper, more concentrated sources of geothermal energy
pros: medium net energy
low co2 emissions
cons: drilling geothermal wells is expensive and risky
not many hydrothermal sites with concentrations of heat high enough to make it affordable
can be non renewable if heat is extracted faster than it can be restored
biomass
energy can be produced by burning the solid biomass of organic matter found in plants or plant related material or by converting it to gaseous or liquid biofuels
biomass fuels include wood, wood wastes, agricultural wastes such as sugarcane stalks, rice husks and corncobs
common liquid biofuels are ethanol and biodiesel
the biggest producers of liquid biofuels are US, Brazil, European Union, China
pros: can be grown throughout much of the world, no net increase in co2 emissions, and easy to store and transport
some biofuels produce 20% more greenhouse gases to atmosphere per unit of energy than gasoline
they requiere huge amounts of water and ethanol distilleries produce large volumes of wastewater
tropical ranforest, grasslands and wetlands are being destroyed
alternative biofuels: algae
pros: can grow year round in various aquatic environments
can produce 10x more energy per area of land than plants used to produce ethanol
cons: extracting and refining the oil from algae is too costly
biodigesters- biogas
a biodigester is fed with organic material which is broken down by bacteria in an oxygen free environment to produce biogas and other solids that are mainly used as fertilizer.
methane can be burned to produce heat which can be used directly or used to create steam and generate electricity in aturbine
pros: reduces amount of waste going to landfills
helps get rid of and make use of food and plant waste
reduces amount of lifestock and human waste entering water ecosystems
creates less co2 than fossil fuels
home versions are cheap to make
creates jobs- waste collection
cons: too low net energy for mass scale
impurities can damage is used in combustion engines
hydropower
hydropower is any technology that uses kinetic energy of flowing and falling water to produce electricity
dams store up water and allow it to flow through a turbine to generate electricity
pros: least expensive renewable energy resource. source of energy is free and anually renewed by snow and ranifall
cons: they fill with silt and become useless
flood and destroy terrestrial habitats upstream
flooded vegetation dies and produces methane
reduce flow of water and sediments into river deltas and estuaries
tidal energy: in some coastal and bay estuaries, water levels can rise or fall by 6 meters or more between daily high and low tides. dams can be built across bay/estuary to capture the energy in these flows for hydropower but sites with large tidal flows are rare
wave energy: floating turbing can produce electricity through movement. but lack of suitable sites citizen opposition at some sites, high costs, and equipment damage from saltwater corrosion and storms
hydrogen
hydrogen gas could be the fuel of the future using fuel cells to generate electricity for buildings and powering cars
pros: no co2 emissions or air pollutants
fuel cells are more efficient
requires little maintenance
hydrogen has negative net energy, there is very little hydrogen gas in the atmosphere, its expensive and its dangerous to store and transport
