MSE Energy

energy made available by flow of electric charges through conductor

energy carrier, not primary source

easily transported through power lines, easy conversion into other energies

give access to kinetic energy or heat at distance

E = Q * V (charge * voltage)   ; electric power P = I^2 * R = current^2 * resistance

energy stored within chemical bonds

exchanged in chemical reactions, when bonds are broken or formed

potential energy of a magnetic field

energy source that use a generator to make electricity, electric motors

e.g. medical devices, compass, superconducting magnetic energy storage systems

comes from vibration of matter

mechanical wave, consists physically in oscillatory elastic compression or oscillatory displacement of a fluid

e.g. noise, music, ultrasound

yell for 8 years at a cup of coffee to heat it up => very low energy density

released by reactions within atomic nuclei

fission: breaking of atomic nuclei => long term radioactivity products

fusion: "melting" of atomic nuclei, generation of bigger nuclei

radioactive decai: noclei spontanously decay into other nuclei and sub-atomic particles

energy release in a controlled way = electric energy in nuclear power plants

=> for all, total mass of nuclei at end will be less than in start => E = mc^2 , assumption of constant mass does not hold for nuclear physics

renewable = energy flows which are replenished at the same rate they are used

sustainable = not depleted by continuous use, no significant pollutant emissions or environmental problems, does not drive substatial health or social issues

water cycle is driven by the sun, so renewable. but that does not necessarily mean it is sustainable.

"three gorges" in china

production of 22500 MW = 20x bic nuclear power plant

> 600 plants with a power of at least 300 kW

alsmost 60% of domestic energy production

44% run-of-river powerplants, 52% storage power plants, 4 % pump storage

require a dam to store water in reservoir

large hydraulic head (= difference of height)

high pressure, high impulse

good electricity production even at low flow rates, pumping is feasible

mostly potential energy => pressure energy (kinetic is low because velocity is low)

storage: upper reservoir, level of water determines water head (how much pressure can be built up in penstock)

headrace tunnel: connects e.g. different reservoirs, not steep

upper surge chamber

butterfly valve (on/off)

penstock: pipes with fall of water, very steep, pressure buildup

pump/turbine

lower surge chamber

tailrace tunnel: to connect to discharge

lower reservoir = afterbay; or just discharge in river

for pressure waves that travel through penstock; the can come from valves openings or closings; they would travel up the penstock and down again and then hit the turbine and damage it. ="water hammer" effect

surge chamber discharge it sagely by oscillating water up and down.

do not require dam for storage, no uphill reservoir

only barrage dam (lower)

low hydraulic head, low pressure; reaction more than impulse

water flow cannot be stopped

biggest are mostly pure storage plants, no pumping

biggest number of plants are run-of-river plants

Biggestl: Bieudron, in Riddes VD; 2201 GWh per year

storage: good for fine tuning of current

run of river: highly seasonal, no fine tuning possible

pump storage: buying cheap energy and selling it when prices are high

below dam plants: no penstock, smaller head

turbine is connected through a tunnel directly bottom of dam

you can often directly use turbines as pumps (reverse them), depending on the system

swich to storage mode in case of low electricity demand or low prices

use electrical power to store mechanical energy

low water heads (less than 20 m), quite constant mass flow rates; you can switch off a turbine to down-regulate energy production

for high power, high mass flow rates are needed

mass flow rates are seasonal

compensation flow must be quaranteed, avoid negative influence on wild life in river, guarantee passage to upstream rivers

diversion power plants

divert a part of the river, can have a small reservoir, no dam

medium to low hydraulic head => medium to low pressure

water flow cannot be stopped

forebays are usually artificial basins, like stream valley resrvoirs or top hill reservoirs

arch dams, gravity dams, buttress dams, embarkment dams

afterbays are lakes or artificial basins; often plants directly discharge into rivers

either burried or outside (easy to maintain)

try to minimize the ratio of water conductor length to head (ideal = 1 = vertical)

inclinate = loss of hydraulical power

smaller tubes = more hydraulical losses, but if you have only one pipe (not burried) => very very big walls for stability!

hydraulic turbine turns a wheel and produces power by moving a shaft in a generator

Pelton, Turgo, Cross flow

suitable for high heads, one way machine, exploits speeds (high kinetic energy) for very high heads, because wheel works at atmospheric pressure, you do not neet to withstand 100 bar from 1 km penstock

nozzle transfers pressure into velocity (conservation of mass flow increases speed in nozzle)

pelton: for high heads and small volume flow rates (head approx 30 to1000 m, flow not more than 2 m3/s

kaplan: low heads (max 50 m), highest flow rates (up to 50 m3/s)

francis: head medium (9 m to 400 m) but flow rates must be higher than for pelton (0.5 - 25 m3/s

banki: small to medium heads, small to medium flow

flow pressure acts directly on turbine blades, runner is completely submerged in water

has to withstand water pressure => not for very high heads

Francis: mixed impulse/reaction turbine = exploit kinetic energy and pressure

Kaplan and Bulb: pure reaction turbines = exploit pressure, slow water flow, but high mass flow, e.g. run of river; angle of blade depends on mass flow rates

transfers mechanical energy into electrical

shafts of turbine runners are connected to rotors of electric generators

rotor turns inside a stator and generates high voltage electric current, can reach efficiency up to 98%

electric current is transformed and sent to switches to be injected into transmission lines

switch connects produced electricity to grid (after transformer)

switch stabilizes at the same frequency like the grid; then it stwitches on and starts energy input

if you would work without switch, you will destabilize grid

theoretical electrical power is decreased by energy losses

piping and hydraulic losses, turbomachinery losses, generator motor losses, electronic component losses

however, efficiencies are quite high, because we deal with mechanical energy

total efficiency = product of all efficiencies, can go from 75% to above 90% for hydro power plants

emission free, no CO2, NOx, SOx, particulates

renewable with high conversion energy to electricity

dispatchable with storage capability

usable for base load, peaks and pumped storage applications

scalable from 10 kW to 10000 MW

low operating and maintenance costs

long lifetime (50+ years)

frquently involves impoudnment of large amounts of water, loss of habitat due to land inundation

variable output depending on rain and snowfall

impact on river flows and aquatic ecology, fish migration, oxygen depletion

social impacts of displacing people

health impacts in developing countries

high initial capital costs

long lead time in construction of big projects

gravitational effects of sun and moon on earth water

for range power and current powers

kinetic energy by turbines directly (current) and potential energy with a dam (range)

tidal range tech = dam or barrier traps water

difference between tide hight inside and outside = discharge of water from one side to another => potential energy

flow through bulb turbines that are permanently submerged

largest: Sihwa in South Korea 254 MW

use flow of currents, like a wind turbine

more energy capture due to higher density of medium, smaller blades needed

either fixed to sea ground or floating

large source of energy

no waste or pollution generated

always available

could protect coast line against high storm tiedes, provide a bridge