Luku 6 Uusiutuva energia ELEC-C6001Sähköenergiatekniikka 29.2.2016 ja 2.3.2016 Prof. Jorma Kyyrä
Sisältö Aurinkoenergia Tuulivoima Hydrokineettiset järjestelmät Geoterminen energia Biomassa Polttokennot Epäsäännöllinen energian tuotto Energiavarastot
Aurinkoenergia Auringon säteily avaruudessa on jopa 1,366 kw/m2 Maan pinnalla säteily on vaimeampaa useasta syystä johtuen, ilmakehä absorboi säteilyä ja säteily myös heijastuu partikkeleista Avaruuden säteilystä maan pinnalle päätyy 5-70 % Riippuu vuoden ja vuorokauden ajasta Paikasta maapallolla Suomessa auringon vuosittainen säteilyn määrä on n. 1 000 kwh/m² Tunnin aikana maapallon pinnalle tulee auringon säteilyenergiaa enemmän kuin koko ihmiskunta kuluttaa energiaa vuodessa
Center of sun ξ Center of earth Figure 6.1 Zenith angle ξ. 006x001.eps
kwh/m 2 /day >9.0 8.5 9.0 8.0 8.5 7.5 8.0 7.0 7.5 6.5 7.0 6.0 6.5 5.5 6.0 5.0 5.5 4.5 5.0 4.0 4.5 3.5 4.0 3.0 3.5 2.5 3.0 2.0 2.5 <2.0 Figure 6.2 Average solar energy in August in the United States; resolution is 40 km. (Courtesy of the USA National Renewable Energy Laboratory.) 006x002.eps
7.5 7 6 5 4 3 Clear sky insolation incident, horizontal surface (kwh/m 2 /day) Figure 6.3 NASA.) Average annual solar energy worldwide. (Courtesy of the National Aeronautic and Space Administration 006x003.eps
100% Density ratio 80% 60% 40% 2σ 20% 0% 0 2 4 6 8 10 12 14 16 18 20 22 Time 24 Figure 6.4 A typical solar distribution function (solar power density in 24 h period). 006x004.eps
Figure 6.5 Passive thermosiphon hot water solar system. 006x005.tif
New supply of cold water Warm Warm water Lens T Sunrays Collector Figure 6.6 Thermosiphon hot water system. 006x006.eps
Receiver Collector mirror (a) Pipe Cold fluid Trough Sunrays Pipe Hot fluid (b) Trough Figure 6.7 Solar systems: (a) integrated solar combined cycle system and (b) concentrated trough. (Images are courtesy of the US Department of Energy, Washington, DC.) 006x007.eps
Empty space for extra electron Nucleus Electrons Figure 6.8 Silicon: atom and its crystal structures. 006x008.eps
Electron without bonding Si Si Si Extra space for electron Si Si Si Si Si Si P Si B Si Si Si Si Si Si n type p type Figure 6.9 Silicon (Si) doped with phosphorus (P) and boron (B). 006x009.eps
Lens I n-type p-type + Load Base Figure 6.10 Concentrating PV cell. 006x010.eps
Glass cover or lens Antireflective coating Contacts grid n-type material p-type Base Figure 6.11 Main parts of PV cell. 006x011.eps
Cathode (K) Cathode (K) n p V d I d Anode (A) Anode (A) Figure 6.12 Representation of a p n junction diode. 006x012.eps
V d I d + I d V l V s R Forwardbiased region I o Reverse-biased region V d Figure 6.13 Characteristic of p n junction diode. 006x013.eps
+ I V Load I Figure 6.14 Representation of solar cell connected to load. 006x014.eps
Solar cell I s Id V=V d I Load Figure 6.15 Modeling of ideal cell with current source. 006x015.eps
I d I s I o Vd V d I=I s I d Q II Q I V d Q III Q IV Figure 6.16 Current volt characteristics of the PV cell. 006x016.eps
I I sc I mp P max P V mp V oc V d Figure 6.17 Current voltage and power voltage characteristics of PV cell. 006x017.eps
I s Id = I s V oc Figure 6.18 PV under open circuit condition. 006x018.eps
I s I d =0 I sc = I s Figure 6.19 PV under short circuit condition. 006x019.eps
I R 1 R 1 < R 2 < R 3 1 Load lines 2 R 2 3 R 3 V oc V Figure 6.20 Operating points of the solar cell connected to a resistive load. 006x020.eps
I ρ 3 ρ 1 < ρ 2 < ρ 3 ρ 2 2 3 Load line ρ 1 1 V Figure 6.21 Effect of irradiance on the operating point. 006x021.eps
P ρ 1 < ρ 2 < ρ 3 ρ 1 ρ 2 ρ 3 V Figure 6.22 Effect of irradiance on PV output power. 006x022.eps
I T 1 > T 2 > T 3 T 1 3 Load line 1 2 T 2 T 3 V oc V Figure 6.23 Effect of temperature on the operating point. 006x023.eps
P T 1 > T 2 > T 3 T 1 T 2 T 3 V Figure 6.24 Effect of temperature on PV output power. 006x024.eps
Module or panel Array System Figure 6.25 PV module, PV array, and PV system. (Images courtesy of the US Department of Energy, Washington, DC.) 006x025.eps
I s1 I d1 V d1 Load I d2 V d2 I s2 Figure 6.26 Solar cells in series. 006x026.eps
I s = I s1 = I s2 V = V d1 + V d2 Load Figure 6.27 Equivalent circuit for solar cells in series. 006x027.eps
I s1 I d1 V d1 V Load I s2 I d2 V d2 Figure 6.28 Solar cells in parallel. 006x028.eps
I s = I s1 + I s2 V = V d1 = V d2 Load Figure 6.29 Equivalent circuit of solar cells in parallel. 006x029.eps
Current and power 1.2 1 0.8 0.6 0.4 0.2 Current Power 0 0 0.1 0.2 0.3 0.4 0.5 Voltage Figure 6.30 I V and P V characteristics of a single cell (current in A, voltage in V, and power in W). 006x030.eps
Module current and power 20 15 10 5 0 Current Power 0 5 10 15 Module voltage 20 25 Figure 6.31 I V and P V characteristics of a single cell (current in A, voltage in V, and power in W). 006x031.eps
Solar cell R s I I s I d V d R p I p V Load I Figure 6.32 Model of real PV cell. 006x032.eps
Figure 6.33 Various photovoltaic systems. (Image courtesy of the US Department of Energy, Washington, DC.) 006x033.eps
Solar array House dc current Charger/ discharger Converter ac current Battery Local load Figure 6.34 Storage PV system. 006x034.eps
Solar array House dc current Converter ac current Meter To utility Local load Figure 6.35 Direct PV system. 006x035.eps
$6.0 $5.0 $5.0 $4.0 $/kwh $3.0 $2.0 $1.0 $1.5 $0.6 $0.4 $0.3 $0.0 1970 1980 1990 Year 2000 2010 Figure 6.36 Price of kwh from PV systems. 006x036.eps
Figure 6.37 High power PV systems. (Images are courtesy of the US Department of Energy, Washington, DC.) 006x037.eps
6.2 Tuulienergia Käytetty jo tuhansia vuosia mm. purjehduksessa, noin 5000 sitten Egyptissä Ensimmäiset tuulimyllyt noin 3000 BC Kiinassa ja sen jälkeen Babyloniassa Ensimmäinen tuuliturbiinin rakensi Charles F. Brush 1888 Suurimmat tuulivoimalat ovat nykyään jopa 8 MW, 6.2.1, 6.2.2, 6.2.7-6.2.13, muu oheislukemista
World Wind Energy Association http://www.wwindea.org/home/index.php
Suomen tuulivoimatilasto, VTT http://www.vtt.fi/proj/windenergystatistics/
Tuulivoimalat Suomessa Nykyisten voimaloiden sijaintipaikat Uudet suunnitelmat kartalla
Suomen tuuliatlas http://www.tuuliatlas.fi/fi/ index.html
Määritelmiä (1/2) Tuotanto roottorin pyyhkäisypinta-alaa kohti (kwh/m2): Tuotanto roottorin pyyhkäisypinta-alaa kohden kertoo, kuinka paljon energiaa on tuotettu roottorin pinta-alaan nähden. Nyrkkisääntönä on, että voimala on tuottanut hyvin, mikäli vuosituotannosta laskettu luku on yli 1000k Wh/m2. Huipunkäyttöaika th (h): Tuulivoimaloiden energiantuotanto vaihtelee välillä 0 % - 100 % nimellistehosta. Th kuvaa sen ajan pituutta, joka kuluisi vuodessa tuotetun energian tuottamiseen, mikäli tuulivoimala toimisi koko ajan nimellistehollaan Esimerkiksi 2500 tunnin huipunkäyttöaika sitä että laitos on tuottanut vuoden aikana energiamäärän, jonka laitos tuottaisi toimiessaan nimellistehollaan 2500 tuntia Mikäli tuulivoimalan vuotuinen huipunkäyttöaika on yli 2400 tuntia, on laitos tuottanut hyvin. Kapasiteettikerroin CF: Kapasiteettikerroin CF kertoo huipunkäyttöajan suhteessa vuoden tunteihin ja se kuvaa siten oleellisesti samaa asiaa kuin huipunkäyttöaika Kapasiteettikerroin on käytössä erityisesti englanninkielisessä kirjallisuudessa
Määritelmiä (2/2) Tuotantoindeksi IL (%) Tuotantoindeksi on sääasemilla mitattujen tuulennopeushavaintojen perusteella laskettu tuotanto suhteessa pitkän aikavälin havainnoista laskettuun keskimääräiseen tuotantoon Suomen tuulivoimatilastoissa keskimääräinen tuotanto on tällä hetkellä laskettu vuosien 1987-2001 tuulennopeushavainnoista. Tuulennopeushavainnot muutetaan keskitehoksi käyttäen 1500 kw tuulivoimalaitoksen tehokäyrää ja huomioiden ilman tiheyden vaikutus tehontuotantoon Tuotantoindeksiä tarvitaan kun halutaan selvittää, kuinka tuulinen jokin tietty ajanjakso oli suhteessa pitkän aikavälin keskimääräiseen tuulisuuteen. Asia on erityisen tärkeä tuulivoimainvestointien yhteydessä, jolloin on selvitettävä mikä on tuotantoennuste voimalahankkeen eliniän ylitse.
Wind power class Resource potential Wind power classification Wind power density at 50 m W/m2 Wind speed a at 50 m m/s 3 Fair 300 400 6.4 7.0 14.3 15.7 4 Good 400 500 7.0 7.5 15.7 16.8 5 Excellent 500 600 7.5 8.0 16.8 17.9 6 Outstanding 600 800 8.0 8.8 17.9 19.7 7 Superb 800 1600 8.8 11.1 19.7 24.8 a Wind speeds are based on a welbul k value of 2.0 Wind speed a at 50 m mph Figure 6.38 US average wind power density map at 50 m above sea level. (Courtesy of the USA National Renewable Energy Laboratory.) 006x038.eps
Rotating blades Low-speed shaft High-speed shaft Housing Hub (Nacelle) generator Gear box Yaw Tower (a) Figure 6.39 (b) Basic components of a wind-generating system: (a) horizontal design and (b) main parts. 006x039.eps
(a) Figure 6.40 (a) Housing and (b) blade of a 1.8 MW wind generating system. (b) 006x040.eps
Upper camber Leading edge Airfoil Lower camber Trailing edge Figure 6.41 Airfoil. 006x041.eps
Center of gravity Mean camber line Cord line Figure 6.42 Mean camber line, center of gravity of airfoil, and cord line. 006x042.eps
w 1 w Airfoil w 2 Figure 6.43 Flow of air around airfoil. 006x043.eps
Pr 1 Airfoil Pr 2 Figure 6.44 Bernoulli s principle. 006x044.eps
Aerodynamic force Wind direction Airfoil Figure 6.45 Aerodynamic force. 006x045.eps
F w F L α F L F D F α F L F F D (a) (b) (c) w α F F D α F D F L F (d) (e) Figure 6.46 Aerodynamic forces and angle-of-attack: (a) horizontal position all aerodynamic force is lift; (b) positive angle-of attack aerodynamic force has lift and drag; (c) increasing positive angle-of attack, less lift, and more drag; (d) increasing positive angle-of attack until aerodynamic force is all drag; and (e) negative angle-of attack lift is reversed. 006x046.eps
Lift Maximum lift Stall Angle for zero lift α 0 α max α Figure 6.47 Lift force as a function of angle-of-attack. 006x047.eps
w α β Vertical motion of the center of gravity Cord line Figure 6.48 Relative wind speed, angle of attack and pitch angle. 006x048.eps
Captured power from wind P blade Input to gearbox P gear Input to generator P g Output power P out Losses in rotating blades and rotor mechanism Losses in gearbox Losses in generator Figure 6.49 Power flow of a wind turbine. 006x049.eps
P out P rated B C D A w min w B w max w Figure 6.50 Output power of wind turbine. 006x050.eps
v tip Blade ω r Figure 6.51 Tip velocity. 006x051.eps
C p C p max TSR ideal TSR Figure 6.52 Coefficient of performance as a function of TSR. 006x052.eps
C p C p max TSR ideal Stronger wind Weaker wind TSR Figure 6.53 Tracking maximum C p by adjusting the speed of the blade. 006x053.eps
C p β 1 > β 2 > β 3 β3 β 2 β 1 TSR Figure 6.54 Coefficient of performance as a function of pitch angle. 006x054.eps
C p β 1 > β 2 A C β 2 B β 1 TSR A TSR B TSR Figure 6.55 Tracking the maximum C p by changing the pitch angle. 006x055.eps
C p C px β 1 > β 2 X B β 2 C pc C β 1 TSR X TSR B TSR Figure 6.56 Spilling wind by adjusting pitch angle. 006x056.eps
Figure 6.57 Horizontal axis wind turbines. 006x057.tif
Figure 6.58 Lifting of gearbox and brakes of HAWT. (Courtesy of Paul Anderson through Wikipedia.) 006x058.tif
Figure 6.59 Vertical axis wind turbine. (Courtesy of US National Renewable Energy Lab.) 006x059.tif
Farm collection point Grid connection point HV-GSU point Trunk line G Gear box Grid GSU xfm Figure 6.60 Type 1 wind turbine system. 006x060.eps
Farm collection point G Gear box Rotor converter Figure 6.61 Type 2 wind turbine system. 006x061.eps
Farm collection point G Gear box ac/dc dc/ac dc link ac/dc dc/ac Link converter Rotor converter Figure 6.62 Type 3 wind turbine system. 006x062.eps
Farm collection point AC/AC G Full converter Figure 6.63 Type 4 wind turbine system. 006x063.eps
Figure 6.64 Type 4 6 MW wind turbine made by Enercon. 006x064.tif
Figure 6.65 DC.) Wind farm located in California. (Images are courtesy of the U.S. Department of Energy, Washington, 006x065.eps
Figure 6.66 Two megawatt offshore wind turbine farm in Denmark. (Image courtesy of LM Glasfiber Group.) 006x066.tif
Reactive power Generation range Q min n s Speed Figure 6.67 Reactive power of induction machine. 006x067.eps
n Time Q Time V V r Time Figure 6.68 Wind speed, reactive power, and terminal voltage. 006x068.eps
6.3 Hydrokineettiset järjestelmät Pienet vesivoimalat Vuorovesivoimalat Aaltoenergia Eri ratkaisujen periaateet, mutta mekaaniikan yhtälöt yms ovat oheislukemista.
Reservoir Penstock Generator Head Turbine Discharge Figure 6.69 Small hydroelectric system with reservoir. 006x069.eps
Power at the entrance of penstock P p-in Power at the end of penstock P p-out Blade power P blade Input power to generator P m Output electric power P g Penstock losses Hydro losses Turbine losses Generator losses Figure 6.70 Power flow in small hydroelectric system. 006x070.eps
Sea side Barrage Shore Lagoon side Turbine Lagoon side Sea side Water flow Water flow H high H low (a) Figure 6.71 Barrage tidal energy system: (a) high tide and (b) low tide. (b) 006x071.eps
Tidal height 24 h Datum H ebb1 Hebb2 H flow2 H flow1 Tidal period Time Figure 6.72 Semidiurnal tide. 006x072.eps
Generator Turbine Water flow Figure 6.73 Diversion-type small hydroelectric system. 006x073.eps
(a) (b) Figure 6.74 WS energy system: (a) turbine and (b) conceptual design of a farm. (Images courtesy of Marine Current Turbines Limited.) 006x074.eps
Crest Trough Amplitude (α) Height (h) Seawater level Wavelength (λ) Figure 6.75 Wave parameters. 006x075.eps
Float Wave Coil (mounted on enclose) V Magnets (anchored) Enclosure (mounted on float) Linear generator Anchor line Figure 6.76 Buoyant moored system. 006x076.eps
Figure 6.77 Buoyant actuator during the installation. (Courtesy of Carnegie Wave Energy through Wikipedia.) 006x077.tif
Float Wave Line Linear generator Figure 6.78 Buoyant moored system anchored on ocean floor. 006x078.eps
Float Hydroelectric power plant Seawater piston High pressure flow line Figure 6.79 Oyster system. 006x079.eps
Generator Wave G M Hydraulic motor Pistons Hinges G M Piston Hydraulic motor Figure 6.80 Main components of hinged contour system. 006x080.eps
Figure 6.81 HC system. (Courtesy of Pelamis Wave Energy through Wikipedia.) 006x081.tif
Figure 6.82 The front pontoon. (Courtesy of Pelamis Wave Energy through Wikipedia.) 006x082.tif
Linear generator Chamber Wave Figure 6.83 Oscillating column system. 006x083.eps
6.4 Geoenergia Lämpöpumput Sähkön tuotanto maalämmöllä Maalampövoimalat
2900 km Mantle Earth s crust 6370 km Outer core Inner core Center of earth Figure 6.84 Cross section of Earth. 006x084.eps
5 20 500 600 1400 Temperature 40 km Depth Mantle 100 200 km Figure 6.85 Geothermal gradient of Earth. 006x085.eps
Favorability of deep EGS Most favorable Least favorable N/A* No data** Identified hydrothermal site ( 90 C) Figure 6.86 Geothermal map of the United States. (Courtesy of the United States National Renewable Energy Laboratory.) EGS stands for enhanced geothermal system. 006x086.eps
Warm air to house Hot water tank Pump and heat exchangers Return cool air Ground Geo-exchanger Figure 6.87 Heat pump system. 006x087.eps
Figure 6.88 Steam generated from rain even in cold environment. 006x088.tif
Steam Rain water Rain water Steam reservoir Melton rock Figure 6.89 Geothermal reservoir. 006x089.eps
Hot water extraction Cold water injection Stimulated fractures Low-temperature sediment Hot rocks (Granite) 3 15 km Figure 6.90 Hot dry rock site. 006x090.eps
Steam Turbine G Cooling tower Mist eliminator Reservoir Heat Magma Figure 6.91 Reservoir type geothermal power plant. 006x091.eps
Thermal turbine Generator G Cooling tower Heat exchanger Stimulated fractures Low-temperature sediment Hot rocks (Granite) 3 15 km Figure 6.92 Hot dry rock geothermal power plant. 006x092.eps
Figure 6.93 The Geyser s in northern California the first geothermal power plant in the United States. 006x093.tif
Figure 6.94 Geothermal power plants in the United States in 2010 (numbers in MW; white numbers for existing installations; yellow for planned installation). (Courtesy of the USA National Renewable Energy Laboratory.) 006x094.tif
Turbine G Condenser Steam Stack Water pipes Furnace Filter Storage Light ash to landfills Heavy ash to landfills Figure 6.95 Biomass incineration power plant. 006x095.eps
6.6 Polttokennot Ensimmäiset polttokennot on kehitetty jo 1839 Francis Bacon 1939 ja sen jälkeen käytetty NASAn avaruuslennoilla Useimmat polttokennot käyttävät vetyä ja happea sähkön tuottamiseen. Sivutuotteena syntyy vettä. Osa polttokennoista voi käyttää polttoaineen suoraan metanolia eikä silloin tarvita erillistä reformointiprosessia vedyn tuottamiseen Luvussa 6.6 olevat kemian liittyvät asiat ovat oheislukemista.
Polttokennotyypit
H 2 O CO 2 CH 2 H 2 Water (H 2 O) O 2 Reformer CO 2 CO CO conversion H 2 Fuel cell Figure 6.96 Generation of hydrogen. 006x096.eps
Shell Electron Proton H H 2 Figure 6.97 Hydrogen atom and hydrogen gas. 006x097.eps
Load I Hydrogen (2H 2 ) + Hydrogen ions (4H + ) Oxygen (O 2 ) Anode Electrolyte Cathode Water (2H 2 O) Figure 6.98 PEM FC. 006x098.eps
Figure 6.99 PEM fuel cell. 006x099.tif
Load I Hydrogen (2H 2 ) + Hydroxyl ions (4OH ) Oxygen (O 2 ) Water (2H 2 O) Water (2H 2 O) Anode Electrolyte Cathode Water (2H 2 O) Figure 6.100 Alkaline FC. 006x100.eps
Load I Hydrogen (2H 2 ) + Hydrogen ions (4H + ) Oxygen (O 2 ) Anode Electrolyte Cathode Water (2H 2 O) Figure 6.101 Phosphoric acid FC. 006x101.eps
Load I Hydrogen (2H 2 ) + Oxygen ions (2O 2 ) Oxygen (O 2 ) Water (2H 2 O) Anode Electrolyte Cathode Figure 6.102 Solid oxide FC. 006x102.eps
Load I Hydrogen (2H 2 ) Carbonate ions (2CO 3 2 ) Oxygen (O 2 ) Water (2H 2 O) Carbon dioxide (2CO 2 ) Anode Electrolyte Cathode Figure 6.103 MCFC. 006x103.eps
Load I Methanol (CH 3 OH) + Hydrogen ions (6H + ) Oxygen (1.5O 2 ) Carbon dioxide (CO 3 ) Water (H 2 O) Anode Electrolyte Cathode Water (H 2 O) Figure 6.104 DMFC. 006x104.eps
Renewable energy system Electricity Hydrogen generation Hydrogen Distribution infrastructure Co-Gen industrial use air conditioning, etc. Steam Oxygen Hydrogen Oxygen Steam Co-Gen industrial use air conditioning, etc. FC system FC system Water for drinking, agriculture, etc. Water Electricity Electricity Electricity Electric load Electric load Water Water for drinking, agriculture, etc. Utility grid Figure 6.105 Hydrogen-based energy system. 006x105.eps
Gibbs free energy G Electric load Anode Cathode Enthalpy energy H Hydrogen Fuel cell Enthropy energy Q H 2 O Figure 6.106 Gibbs free energy. 006x106.eps
Activation Ohmic Mass transport Power Voltage and power Voltage Current Figure 6.107 Polarization and power curves of FC. 006x107.eps
1.6 Voltage (V) and power (W) 1.4 1.2 1 0.8 0.6 0.4 Voltage Power 0.2 0 0 0.5 1 1.5 Current (A) 2 2.5 3 Figure 6.108 Polarization and power curves of FC in Example 6.35. 006x108.eps
6.8 Energiavarastot Uusiutuvan energian tuotanto on hyvin vaihtelevaa ja usein myös vaikea ennustaa etukäteen Tuotannon vaihdellessa tarvitaan Reservituotantoa Varastoja, joihin aiemmin yli tuotannon varastoitu energia varastoidaan Kulutuksen säännöstelyä Alessandro Volta kehitti akuston jo 1800, mutta energian laajamittainen ja taloudellinen varastointi on edelleen yksi tärkeimmistä avoimista kysymyksistä
Generated energy Consumed energy Figure 6.109 Balance of electric energy. 006x109.eps
Figure 6.110 PHS system. (Courtesy of the United States Army Corps of Engineers.) 006x110.tif
Energy from grid Exhaust Fuel Energy to grid Recuperator M Compressor Turbine G Motor Generator Cavern Figure 6.111 Main components of compressed air energy storage system. 006x111.eps
Magnetic bearing Stator winding High-inertia rotor Stator winding Magnetic bearing Figure 6.112 Main components of flywheel. 006x112.eps