Sustainable Energy Exam

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What are the renewable energy sources

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What are the renewable energy sources

Solar, wind, biomass, hydroelectricity, ocean energy, geothermal.

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What are Intermittent Renewables?

Wind, solar PV, wave energy

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What are the major types of fossil fuels?

coal, natural gas, oil

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What are the two phases of photosynthesis?

light dependent and light independent

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Light Dependent reaction

converts light energy into chemical energy; produces ATP molecules to be used to fuel light-independent reaction H2O splitting to produce O2 and H+ and subsequently ATP/NADPH)

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Light Independent Reactions (Calvin Cycle)

consumes CO2, uses ATP produced to make sugars, and regenerate ADP/NADP.

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The electromagnetic light spectrum

Gamma Rays, X Rays, UV, Visible light, Infrared/Microvwaves, Radiowaves

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Visible light (nm) is only a small part of the electromagnetic spectrum

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Light Harvesting Materials

Pigment/dye, chromophore, auxochrome

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Pigment

dye, a material that changes the color of reflected or transmitted light as a result of wavelength selective absorption

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Chromophore

an atom or group whose presence is responsible for the color of a compound

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auxochrome

the charged portion of the chromogen that allows it to act as a dye through ionic or covalent bonds between the chromogen and the cell.

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Beer-Lambert Law

Used to relate the concentration of colored solutions to the amount of visible light they absorb.

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bathochromic

shift to longer wavelength

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hypsochromic

shift to a shorter wavelength

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basic energy concept during photosynthesis

energy transfer: a pure physical process that only involves the excitation of molecules. Electron transfer: A pure chemical process

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Z Scheme of photosynthesis

PSI and PSII: The Z refers to changes in redox potential of electrons. Note that PSII comes before PSI because they're named in terms of discovery, not sequence.

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PSII

Functions first (the numbers reflect order of discovery) and is best at absorbing a wavelength of 680 nm (The reaction-center chlorophyll a of PS II is called P680)

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•Oxidized P680 (P680+) is the strongest biological oxidizing agent known. It has an estimated redox potential of ~1.3 V

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•This makes it possible to oxidize water during oxygenic photosynthesis

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PSI

is best at absorbing a wavelength of 700 nm

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The reaction-center chlorophyll a of PS I is called P700

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Conductors:

materials that allow electric charges to flow through them easily; no band gap

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Semiconductors

elements that conduct an electric current under certain conditions; medium sized band gap

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Insulators

materials that prevent electric charges from flowing through them easily; large band gap

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band gap

an energy gap that exists between the valence band and conduction band of semiconductors and insulators

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FRET energy transfer

The Forster Resonance Energy Transfer. The phenomenon that an excited donor transfers energy to an acceptor group through a non-radiative process. It is a special technique to gauge the distance between two chromophores. Fret only works when the separating distance between donor and acceptor is under 10 nm. FRET is distance-dependent and is a popular tool to measure dynamic activities of biological molecules within a nanoscale.

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Dexter Energy Transfer

•sometimes called short-range, collisional or exchange energy transfer which is a process with electron exchange.

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• similar to Förster energy transfer but differs greatly in length scale (<10 Å) and underlying mechanism.

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•two molecules (intermolecular) or two parts of a molecule (intramolecular) bilaterally exchange their electrons.

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•reaction rate constant of Dexter energy transfer exponentially decays as the distance between two parties increases.

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•On account of the exponential relationship to the distance, the exchange mechanism typically occurs within 10 Å.

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Silicon Photovoltaic efficiency limit

Silicon is transparent at wavelengths longer than 1.1 microns (1100nm) 23% of sunlight passes through with no effect. only 77% of the solar spectrum is absorbed by silicon, and of that 77% only 30% is used as electrical energy.

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Dye-sensitized solar cells

When light strikes the solar cell, dye sensitizers on the surface of a TiO2 film excite and inject electrons into the conduction band of TiO2 film. The electrons diffuse all the way through the mesoporous film to the anode.

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Theoretical capacity of Li

3860 mA h g−1

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Theoretical capacity of Na

1165 mAh g−1

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Theoretical Capacity of Zn

820 mAh/g

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Theoretical Capacity of S

1675 mAh g−1

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Redox flow battery

The power is defined by the size and design of the electrochemical cell. Energy depends on the size of the tank

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Standards of good catalysts

Activity, stability, selectivity

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Activity

describes the effective concentration of that substance in the reaction mixture

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Stability

How long the catalyst can work

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Selectivity

how selective the catalyst can facilitate the production of a certain product

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Water Splitting

chloroplast splits water into hydrogen and oxygen (H is used in sugars and O2 is released)

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Water Splitting Overpotential

Real water electrolyzers require higher voltages for the reaction to proceed. The part that exceeds 1.23 V is called overpotential or overvoltage, and represents any kind of loss and nonideality in the electrochemical process.

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What is electrical energy measured with?

Kilowatt-hours

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What is heat energy measured with?

British Thermal Units (BTU)

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Joule

SI unit of energy

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1 kilowatt-hour (kWh)

3.60 x 10^6 joules (J)

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1 calorie of heat

the heat needed to raise 1 gram of wwater 1 degree centigrade

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1 calorie

4.184 (J)

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1 BTU

the amount of heat necessary to raise one pound of water by 1 degree F

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1055 J

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252 cal

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1.055 kJ

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What is an intermittent renewable?

Generation Capacity Resource with output that can vary as a function of its energy source

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What is a fossil fuel?

a natural fuel such as coal or gas, formed in the geological past from the remains of living organisms.

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What are fossil fuels made of?

hydrocarbons, and they contain carbon hydrogens such as methane

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FRET and Dexter Comparison

The difference between Förster and Dexter mechanism include

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•Dexter mechanism involves the overlap of wavefunctions so that electrons can occupy the other's molecular orbitals.

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•The reaction rate constant of Dexter energy transfer sharply decreases while the distance between D and A increase and the distance is generally smaller than 10 angstroms.

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•The Dexter mechanism can be applied to produce the triplet state of some molecules of interest.

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•The special case of exchange-triplet-triplet annihilation-can "push" the electron to upper singlet states by exchanging the electrons of two triplet molecules.

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Different types of batteries

Small scale batteries are concerned with energy density, while flow batteries are concerned with energy on a larger scale

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Calculating Theoretical Capacity

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