MSE Energy

Our nuclear fusion plant

medium-small star (yellow star) this is good because it means that it is very stable for the moment

it has already consumed approx 40 % of its fuel

mass 2*10'^20 kg, Made of H2 and He

Surface temperature 5780 K

direct conversion into electric current by photovoltaic modules

heat up a fluid for a concentrated solar thermal power plant => electricitty

heat up a fluid for solar thermal modules (hot water and heating)

distance earth sun = 1.5 * 10'11 m => distance influences a lot the energy input to earth outer atmosphere

1.3 kW/m^2 energy input from sun on our outer atmosphere limit

from UV to infrared, peak radiance in visible area.

At limit of atmosphere, solar irradiation is very close to a perfect black body irradiance at 5250°C (black body = perfect emitter)

at sea level, there is much less irraditation due to absorption of different molecules (e.g. O3 in UV region, H2O, O2 at infrared length)

DNI: direct normal irradiance in W/m2, on ground approx 1 kW/m^2

diffused radiation: solar radiation scattered by atmosphere

global or total radiation: DNI + diffused radiation

Europe: assume 50% DNI + 50% diffused => less energy yield than in sun belt (1000 kWh/(m^2 y) compared to 2000)

so on a cloudy day you will not have a shadow even though you can see something (visible light present), radiation is diffused and rays come from all sides

sun belt goes up to 37°N

with highest irradiation (irradiation = integral of irradiance over time)

highest energy harvest for solar power possible. however, no sun belt in china due to high cloud formation over the part of the continent

tested technology

south facing windows, good landscape in front

industrial, commercial and large residential buildings

low cost of operation and maintenence, no specialized personnel, passibe system

reduces building lossese by heat during winter

improves interior air quality

heavy insulation to top and north, stone floors and walls for heat storage

active system uses antifreeze

tested tech

applicable at all latitudes

for new and existing buildings

moderate cost of operation and maintenance

with pump, storage tank and heat exchanger

Total losses depend on global loss coefficient and difference between temperature on plate and ambient temperature

solar collectors should try to be perpendicular to rays to collect max heat (use inclined surfaces)

concentration of rays on a small receiver, higher temperature = higher efficiency in cycle, use some sort of parabolic shape that follows the sun (so called solar tracking)

solar towers, mirrors (heliostats) guide sunlight to tower in middle of plant (point concentration)

dishes that have a receiver mounted in the middle in front of the parabolic dish (point concentration), C 1000 - 1300, Power 7.5 -100 kWe, 2 axis tracking

parabolic throughs, with long tubes as receivers (line concentration), C 30 - 90, power 50-80. 1 axis tracking

(concentration factor of shape * solar intensity / stefan boltzmann constant) ^ 0.25

sun heats up liquid in receiver, this heats up a boiler. secondary cycle: steam goes through turbine and then condenser

collection of solar heat: oil or molten salts (T up to 400-550°C), more efficiency

(molten salts are usually NaNO3 +KNO3), very good heat transfer; but you need an overnight temperature control (should not go below 220°C, significant corrosion possible)

you can in theory use water as heat transfer fluid in primary cycle but it would be at very high pressure to reach 540°C

secondary cycle: Water/steam

cooling tower: water

from sun ray to current: approx 20%

difference is temperature (molten salt is higher), therefore molten salt is more efficient

store hot oil or hot molten salt, so you can run the plant during the night

= energy dispatchability (key for overcoming limitation of renewables)

increases capacity factor (real production per year vs theoretical)

in the morning, you will only feed the boiler for the Rankine cycle

later in the day, feed the storage tanks too

remember, if a cloud => no production at all (very rapidly) because only DNI is harvested. => usually you have a steam reservoir to run the Rankine cycle for a certain time

price drop in PV cells => rather invest in PV

CSP needs people on site (checks, maintenance, etc.) + fluids are needed => operation is more complex and costly

single advantage of CSP is storage

fiel size: if the field is too big, you cannot hit the receiver precisely anymore and atmosphere inbetween decreases efficiency

this is also an issue because the power density of a CSP is low (approx 30 W/m2) compared to a nuclear power plant (61000 W/m2)

Solar H2O / CO2 splitting

requires a lot of energy, CO2 neutral (capture burned CO2 from atmosphere)

use the normal engines

heat up "balloons" during the day with mirrors. Pump the hot air into a tank with rocks to heat up rocks. In the night, pump cold air into storage tank, get heat from rocks out to use as district heating.

updraft towers: no solar concentration. collector heats up air on ground in a channel. Induce natural convection. Air flows through channels to central tower to rise. air buoyancy drives turbines. Exhaust on top of tower.

solar pond: pond of salt water with black walls. so the bottom gets heated up more. but there is a salinity gradient (very salty at bottom, not very salty at top), so hot and cold water are separated and do not mix. Take out hot water from high salinity bottom, use it as boiler for an organic fluid in a Rankine cycle (at approx 60°C boiling T), drive a condenser to cool the upper low salinity part

Solar tower: efficiency 10 - 28  %; concentration factor up to 1000; successful demo plants

CSP dish: efficiency: 15 -25 %; concentration factor up to 1000; successful demo plant

CSP through: efficiency 10 - 23 %; CF 50 - 90; commercial

solar pond: efficiency 1 %; CF 1; successful demo

solar updraft: efficiency: 0.7-1.2 %; CF 1; successful demo

CSP produces electricity indirectly via heat

PV produces electricity directly via Photo-effect

1839: observed by Alexandre Edmond Becquerel

1954: Bell Labs announce invention of first silicon solar cell with 6% efficiency

light comes from top and hits n-layer. b-payer is at bottom.

n-layer and p-layer are connected by the consumer resistance to close the cycle

energy transfer from photons (=quantum of electromagnetic radiations) to electrons inside a material

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)