Sustainable Energy Exam

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What are the renewable energy sources
Solar, wind, biomass, hydroelectricity, ocean energy, geothermal.
What are Intermittent Renewables?
Wind, solar PV, wave energy
What are the major types of fossil fuels?
coal, natural gas, oil
What are the two phases of photosynthesis?
light dependent and light independent
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)
Light Independent Reactions (Calvin Cycle)
consumes CO2, uses ATP produced to make sugars, and regenerate ADP/NADP.
The electromagnetic light spectrum
Gamma Rays, X Rays, UV, Visible light, Infrared/Microvwaves, Radiowaves
Visible light (nm) is only a small part of the electromagnetic spectrum
Light Harvesting Materials
Pigment/dye, chromophore, auxochrome
dye, a material that changes the color of reflected or transmitted light as a result of wavelength selective absorption
an atom or group whose presence is responsible for the color of a compound
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.
Beer-Lambert Law
Used to relate the concentration of colored solutions to the amount of visible light they absorb.
shift to longer wavelength
shift to a shorter wavelength
basic energy concept during photosynthesis
energy transfer: a pure physical process that only involves the excitation of molecules. Electron transfer: A pure chemical process
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.
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)
•Oxidized P680 (P680+) is the strongest biological oxidizing agent known. It has an estimated redox potential of ~1.3 V
•This makes it possible to oxidize water during oxygenic photosynthesis
is best at absorbing a wavelength of 700 nm
The reaction-center chlorophyll a of PS I is called P700
materials that allow electric charges to flow through them easily; no band gap
elements that conduct an electric current under certain conditions; medium sized band gap
materials that prevent electric charges from flowing through them easily; large band gap
band gap
an energy gap that exists between the valence band and conduction band of semiconductors and insulators
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.
Dexter Energy Transfer
•sometimes called short-range, collisional or exchange energy transfer which is a process with electron exchange.
• similar to Förster energy transfer but differs greatly in length scale (<10 Å) and underlying mechanism.
•two molecules (intermolecular) or two parts of a molecule (intramolecular) bilaterally exchange their electrons.
•reaction rate constant of Dexter energy transfer exponentially decays as the distance between two parties increases.
•On account of the exponential relationship to the distance, the exchange mechanism typically occurs within 10 Å.
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.
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.
Theoretical capacity of Li
3860 mA h g−1
Theoretical capacity of Na
1165 mAh g−1
Theoretical Capacity of Zn
820 mAh/g
Theoretical Capacity of S
1675 mAh g−1
Redox flow battery
The power is defined by the size and design of the electrochemical cell. Energy depends on the size of the tank
Standards of good catalysts
Activity, stability, selectivity
describes the effective concentration of that substance in the reaction mixture
How long the catalyst can work
how selective the catalyst can facilitate the production of a certain product
Water Splitting
chloroplast splits water into hydrogen and oxygen (H is used in sugars and O2 is released)
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.
What is electrical energy measured with?
What is heat energy measured with?
British Thermal Units (BTU)
SI unit of energy
1 kilowatt-hour (kWh)
3.60 x 10^6 joules (J)
1 calorie of heat
the heat needed to raise 1 gram of wwater 1 degree centigrade
1 calorie
4.184 (J)
the amount of heat necessary to raise one pound of water by 1 degree F
1055 J
252 cal
1.055 kJ
What is an intermittent renewable?
Generation Capacity Resource with output that can vary as a function of its energy source
What is a fossil fuel?
a natural fuel such as coal or gas, formed in the geological past from the remains of living organisms.
What are fossil fuels made of?
hydrocarbons, and they contain carbon hydrogens such as methane
FRET and Dexter Comparison
The difference between Förster and Dexter mechanism include
•Dexter mechanism involves the overlap of wavefunctions so that electrons can occupy the other's molecular orbitals.
•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.
•The Dexter mechanism can be applied to produce the triplet state of some molecules of interest.
•The special case of exchange-triplet-triplet annihilation-can "push" the electron to upper singlet states by exchanging the electrons of two triplet molecules.
Different types of batteries
Small scale batteries are concerned with energy density, while flow batteries are concerned with energy on a larger scale
Calculating Theoretical Capacity