MSE Energy

+: simple assembly, high power density; low specific investment cost; short construction time; low O&M cost; low lubrication costs; short startup time (switch on to full power); multi fuel (natural gas or oil); pollution performance better than internal combustion engine; no need of water preparation and low water consumption

low efficiency, noise frequencies; fuel needs high quality (else damage and dirt of turbine blades); CO2 emissions

simple: multi application

enhanced: (staged compressor, regenerator, reheater, staged turbine): complicated design, specific application

Gas turbine: direct injection of burned fuel into turbine

steam: closed cycle, no  burning

primary energy source

coal, nuclear, incineration plants, solar (oil or salt cycle to collect heat for a boiler)

energy input by sun, soll by reflection, heat up boiler, steam is generated, but not all heat is transferred to steam, turbine, some energy losses when transferring to grid, some energy is lost in cooling tower; overall 20% efficiency from sun to grid

phase: state of a substance with distinct molecular arrangement; homogenouse and with a boundary surface

pure substance: fixed chemical composition no matter what phase

solid liquid gas

molecular interaction goes down, molecular motion and temperature go up

each phase has its own distinctive structure

solid, liquid, gas, supercritical fluid

vaporization point curve: liquid and gas

melting point curve: solid + liquid

sublimation curve: solid + gas

steep increase of T in compressed liquid

saturated mixture with increasing volume at constant T

steep increase of T with superheated vapour

coexistance of vapour and liquid, T stays constant, v increases

you can put in a lot of energy without increasing temperature => more energy to exploit = latent heat

energy for phase change, latent because not visible by temperature increase

dependent on specific substance and mass

water has very high specific latent heat

lower border: only saturated liquid, upper border only saturated steam

pressure and temperature are not independent, so if you know the evaporation temperature, you know the pressure

high altitude = low pressure, water boils at lower T, takes longer to boil;

at high pressure, less latent heat, less energy storage

= mass fraction of saturated vapour to total mass in mixture (0 to 100%), increases from left to right and is proportional to distances on line

also valid for specific volumes and enthalpies and specific entropy

always use tables, not ideal gas equation

always take the corresponding values of saturated liquid water at the same temperature

but pressure is not the same as in the table, because you are not in the saturated region

best approximation of Carnot cycle in real time

1 2: compression of liquid condensate, ideal would be isentropical compression in pump, a little work in

2 3: saturation and evaporation in the boiler, q in

3 4: vapor expansion in the turbine, some liquid in the turbine, to go outside the bell you would have to heat up even more but T max might be a material constraint, lot of work out

4 1: mixture condensation in the ocndenser, constant pressure line, Q out

Q:in from sun or fuel etc; energy is what you get out, 1 - ((h4-h1)/(h3-h2))

pumping liqud is is less costly than pumping a gas
the efficiency of this cycle is not too bad compared to a corresponding Bryton cycle.
And remember that a Carnot cycle is the most efficient, and here the regions where heat is inserted or taken out, the processes there are isothermal, and that is most efficient

ideal: no losses

real: pump: go at the same pressure but T is slightly higher than ideal, because irreversibiilty will transfer work to heat

expansion: irreversible, not vertical, so you need some pressure difference left to pass through condensor

usually, we will neglect boiler and condenser pressure loss and work only with irreversiblilty in turbine and pump

area within curves is the work we get out

lower condenser pressure, lowers T_low_av

superheat steam to high temperature (increase T_high av)

increase boiler water pressure (increases T_high av)

colder water after pump, so lower line is lower, you increase area within curve

colder water after the pump, so you need to pre-heat more in the boiler

more liquid mixture in the turbine, so technically not nice

increase T further so right limit is pushed further

T av might be a material limit you cannot overcome, so you increase horizontal line in the curve and end up at same T max, by increasing boiler T, you will endu up with more water in the turbine,

there is an increase and a decrease of net work

by reheat (high pressure turbine, go to boiler to reheat, low pressure turbine before the condenser)

so we have two peaks and avoid issues with the liquid turbine

for efficiency, you have two heating steps and two steps where you gain work

often like a farfalle, two turbines so the steam gets divided and goes out on both sides

low temperature heat addition is reducing the cycle thermal efficiency, so increase this and increase teh average temperature of the external heat injection by pre-heating the liquid water by steam from the turbine

so called feedwater heaters (open and closed systems possible)

basically another cycle ist staged on top, in Ts diagram, so area within cycle is increased

vapor extracted from turbine and liquid water are physically mixed

no contact between steam from turbine and feedwater, just a heat exchanger

pre-heating (at low T) by vapor from turbine, no fuel burned

power extraction from turbine is lowered because not all steam goes through turbine

but overall cycle thermal efficiency is raised

combined heat and power generation CHP
 

electric power and heat are generated together, thus exploiting resources better (from 50% to 80% efficiency) from the same energy source

so use the waste heat (instead of putting it e.g. in a cooling tower)