MSE Energy

n-layer: silicate is dosed with atoms that have 1 electron more than silicate (e.g. antimony), n-layer shares electrons in the grid and have thus free electrons

p-layer: silicate dosed with atoms that have 1 electron less than silicate (e.g. Boron), p-layer has an electron hole

so if you hit a valence electron in the p-layer, it becomes a band electron and will move from p-layer to n-layer

photoelectric effect: energy transfer from photons to electrons inside a material, energy of photon is converted into potential and kinetic energy of electron

photovoltaic effect: photons penetrate a semiconductor and transfer their energy on a valence electron in depletion (p)-layer,  electron goes towards n-region

very short installation time

direct conversion of sunlight into electricity

efficiency approx 20 % (comparable to good CSP)

no moving parts (leass war, but exposure to weather)

lifespan of solar panel: produce approx 10x more energy than needed for production of panels :)

battery needed as storage (peak at high sun irradiation)

cells in series: so voltage of each cell is summed up

then take those series and put them in parallel to increase current (more power), current is sum of all series

a few pre-photovoltaic losses (e.g. shade and reflection)

majority of losses in module by not catching photons with too high or too low energy

some output losses when transforming enery to grid

losses due to not catching photons with either too high or too low energy

=> stack PV cells of different types (so called junction cells) where another layer catches the evading photons

multi junction cells are very costly (e.g. for space applications)

if you concentrate, then the PV cells heat up and this is bad for the cells (e.g. semiconductors), so you cool down the panels

voltage stays the same (cells in series), but less current when radiation decreases

fixed angle => peak efficiency during the day and during the year

investment for tracking would be very high (usually higher than profit from increased efficiency)

+ no emissions in electricity production

+ free *fuel*

+ safe in electricity production

+ provides a secure global energy source

+ can also produce with diffuse light, not only DNI

- efficiency drops if T increases (from 24% at 0°C to 14% at 100%)

- => leads to overall reduced efficiency

- only a small portion of the sun energy can be captured and utilized

- difficult for large area energy provision (because large solar field needed)

- high costs for semi conductors and maintenance

plant derived organic matter that is available on a renewable basis

bio mass recycles the CO2 from release

burn to get steam for Rankine cycle (often very dirty (NOx and other pollutants)

convert to liquid fuel

capture methane for powering gas turbines

convert methane to heat

+ reduces waste and odor (often partly Methane) from manure, => reduces CH4, a GHG

+ provides new markets for farmers and jobs in rural communities

+ for large and small scale possible

- higher costs than for fossil fuels

- negative environmental impacts (eg NOx)

- photosynthesis to biomass has a very low efficiency (1 % of solar energy can be extraced by combustion of bio mass), even though this is usually not an issue, it will not solve our energy problems

- some regions are more fertile than others

Radiant, electrical, chemical, sound, thermal, nuclear, mechanical, magnetic

burning a match releases 2700 J

h_potatoes = 611 m

But the problem is, we have to transform energy from chemical to mecahnical, so there are losses

Oil barrel = 127 kg

Content of energy 6.1 GJ (HHV) = barrel of oil equivalent

HHV: in combustion: including water vapour condensation which gives more energy out of it

Combustion of 1 t of crude oil

1 ton of oil equivalent = 1 toe = 42 GJ

energy is the ability of making work, [J]

power is the energy (produced or used) per unit time, [J/s]=[W]

sounds like a power but is an energy

E = P * time

1 kWh = 3600 J

1 toe = 11.63 MWh

energy source = resource for energy production to obtain work or heat

primary source. natural resources that can be directly used without transformation (coal, oil, gas, uranium, biomass, hydropower, sun, wind, geothermal)

secondary source = energy carrier, not available in nature, must be generated from primary source through chemical or physical process, transport of energy (electricity, gasoline, diesel oil, LPG, hydrogen)

renewable = forms of primary energy that are inexhaustible in terms of human time dimensions

solar:

- photosynthesis

- limnic (gravitational, salination, evaporation)

- oceanic: waves, currents, thermal difference, osmotiv

- wind

- direct conversion

geothermal

gravitational

primary energy => conversion / distribution losses, other loesses => secondary energy (gasoline, wood logs, ...) =>consumer losses => useful energy (heat, power, light)

Each step has a certain efficiency

Resources = total amount of primary energy available on planet

Reserves = total amount of exploitable resources

R/P = ratio between reserves remaining at the end of the year and the production of that year

= how long those resources would lasat if production continues at this rate

70/interes = doubling time

e.g. 2% increase each year => doubled energy consumption in 35 years

primary energy consumption is exponential ...

absolute domination by fossil fuels (80%)

increase in reneweables but no big contribution in absolutes

World energy consumption of 556.6 * 10^18 J

38 % for electric energy, 62 % other uses (heating, transportation, industry, ...)

World 556.6 * 10^18 J

CH 1.03 * 10^18 J (0.19%)

but we are below world average in other renewables! (big contribution through hydroelectric and nuclear)

almost 50% are fossil energy