class13_w08

class13_w08 - Global primary energy use 1 EJ = 1018 J (per...

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Global primary energy use 80% of energy from fossil fuels Three-quarters of “Renewables” are from developing countries: biomass Solar + wind together account for less than 1% It is most likely that developing countries will switch from biomass to fossil fuels as economies develop 1 EJ = 10 18 J 1 W = 1J/sec ~ 14 TW (1 TW = 10 12 watts) (per year )
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Passive vs. active solar heating Passive : relies on building design: greenhouses, thick masonry, dark color Active : some other source of energy besides solar is also required water circulation to pick up solar energy for heat and hot water efficiency improvements for water and energy savings Active system
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Solar thermal electricity Various designs are used for concentrating solar energy into a receiver. Mirrors provide up to 5000-fold concentration of photons High temperatures are produced: eg, oil flowing in a closed receiver pipeline is heated heat transfer to steam electrical generator Can be coupled to insulated storage systems to deal with intermittency Dish-engine system is most efficient; T up to 800°C Still more expensive than fossil fuels
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photosynthetic reaction centers electron transfer reactions oxygen generated Light reactions Light reactions C-assimilation reactions C-assimilation reactions CO 2 IN NET FIXED CARBON OUT Photosynthesis uses light photons to fix carbon and generate oxygen
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Charge separation in photosynthesis is analogous to the process that occurs in photovoltaic cells (PV cells)
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class13_w08 - Global primary energy use 1 EJ = 1018 J (per...

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