Deutschlandfunk Journal am Vormittag – Länderzeit vor Ort Geht der Windkraft die Puste aus ?

The economics of wind energy within the generation mix

Energiewirtschaftliche Bedeutung der Windenergie im Stromerzeugungsmix

Hz Black out in Italien am 28.9.2003 um 3.29 Uhr 50,3 Kölner Dom 50,2 157 m 50,1

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49,8 0:00 0:22 0:44 1:06 1:28 1:50 2:12 2:34 2:56 3:18 3:40 4:02 4:24 4:46 5:08 5:30 5:52 Zeit Prof. Dr.-Ing. Helmut Alt RWE Rhein-Ruhr AG, Geschäftskunden Düren Fachhochschule Aachen

Am 5. November 2003, 10.10 – 11.30 Uhr Pariser Platz 6a, Berlin, Café Tucher Moderation DLF : Michael Roehl

Y:\Windkraft\Podiumsdiskussion DLF Berlin Windenergie engl.doc Erstelldatum 12.01.04 09:53 - 2 - The economics of wind energy within the generation mix 1. Some energy basics For thousands of years, man has been using wind energy to facilitate his work both on land and at sea. On land, wind energy was used to operate grinding mills or pumping stations, at sea to sail boats with- out rowing. While in former times the emphasis was on purely mechanical work, such as the milling of grain and water pumping for irrigation, the focus today is on converting wind energy to angular mo- mentum to turn a generator and thus produce electrical energy in a most environmentally compatible, resource-saving and cost-efficient way.

Let us start with some energy basics to explore the worldwide potential of , this source which is fed by the sun. Inside the sun, due to a nuclear fusion reaction, approx. 4.5 million tons of mass are converted into energy every second which reaches our earth at a power den- sity of approx. 1.4 kW/m2 (solar constant). As the earth follows an elliptical path around the sun, the value of the "solar constants" is not constant during the earth’s orbit. The maximum solar radiation in- cident on the earth, S Earth of 1,417 W/m², is reached on January 3 at perihelion, while its minimum of 1,327 W/m² is reached on July 4 at aphelion. With a vertically inclined surface, around 1 kW/m² is available at the earth’s surface: !  1  o  n 3 S Earth S mean "1 0.033 cos(360 )2 # 365 3 where n is the Julian day (i.e. day of the year, from n = 1  January 1, n = 3  January 3 etc.), 2 Smean = 1,372 W/m . Thus, our sun too has a finite life as it consumes resources although it will take around 14 billion years before its loss of mass will add up to 0.1 % of its total mass, provided our Lord will not off the sun’s light beforehand because of his love for mankind. Around 2% of the radiant solar energy of 1.5 · 1018 kWh/a falling onto the earth’s surface are converted into air flow energy in the atmosphere due to climatic processes. This corresponds to an energy poten- tial of 3 · 1016 kWh/a and/or a mean power of 3.4 · 1012 kW. It is estimated that approx. 0.5% of the annual flow energy could be exploited by wind turbines worldwide. This would result in a technically usable energy potential of about 150 · 1012 kWh/a, or 18 billion tce (= Mrd. t SKE). Thus, the usable wind energy potential is of the same order of magnitude as the world‘s energy demand in the year 2000 which totaled about 14 billion tce, or 114 · 1012 kWh.

27 Mass of the Sun: 2 ·10 t 1,400,000 km diameter Age approx. 4.6 G.a. Solar radiation energy received on the earth Life estimation: surface (Albedo A = 0,3): approx. 10 G.a. Sun Mass defect about Total reaction:      2 1 4 P S (1 A) π r Energy radiation: 4 H = He + ∆E e (area of a circle) E = m • c2 = 4.5 M. t/s ∆E = 26.7 MeV Radiation energy reflected by the earth: = 4.3 · 10-12 Ws P = 40 · 10 25 W ( Stefan-Boltzmann-constant ) T = 107 K 2 4 Pa     4  π  r T (surface of a sphere) with emissivity : 0 ?  ?1 (black body), Surface temperature T = 5 714 K  W   5,6710 8 , S = 1,36 kW/m2, A = 0,3 1 1 2 + 2( H + H  H + e + + 1,44 MeV ) 2 4 2 1 3 m