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Lennart Bengtsson ESSC, University Reading ISSI, Bern

Renewable energies are unlikely to satisfy expected global demands with risks for irreversible changes of the Earth ’ s climate. Lennart Bengtsson ESSC, University Reading ISSI, Bern. Heinrich Hertz 1885. Hertz was one of the first that tried to estimate renewable energies.

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Lennart Bengtsson ESSC, University Reading ISSI, Bern

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  1. Renewable energies are unlikely to satisfy expected global demands with risks for irreversible changes of the Earth’s climate. Lennart Bengtsson ESSC, University Reading ISSI, Bern Lennart Bengtsson Global Energy and Climate

  2. Heinrich Hertz 1885 Hertz was one of the first that tried to estimate renewable energies. This was done in his installation lecture in 1885 when Hertz was appointed professor in Physics at the University of Karlsruhe Hertz’s estimate included the amount of energy that was potentially available from the sun, wind and hydro power on a global scale In connection to a lecture I gave in Karlsruhe in 1999 I recalculated this based on global observations Lennart Bengtsson Global Energy and Climate

  3. Global effects in comparisonPresent production = 1.61x1013 W Lennart Bengtsson Global Energy and Climate

  4. Total 71 PWh Fossil 86.6% Nuclear 0.9% Hydro 1.8% Combustion, waste 10.6% Others, wind solar etc.) 0.1% Total 141 PWh Fossil 80.9% Nuclear 5.8% Hydro 2.3% Combustion, waste 10.2% Others 0.8% Energy production in 1973 (left) and 2009(right) Lennart Bengtsson Global Energy and Climate

  5. The following is required to produce 1 PWh2009:(Sweden produced 0.53 PWh)(US 25.15 PWh and China 26.25 PWh) • 90 Mton oil • 140 Mton coal • 95 Gm3 natural gas • 9000 km2 solar panels ( rad. cond. typical of US) • 150 000 wind generators ( 3MW capacity, 25% efficiency) • 330 Mton biomass ( ca 40% water content) (0.5-1.5K/m2, larger figure requires supply of reactive N) will require 800,000km2 land area. • 6 Kton natural uranium (0.7% enrichment) Lennart Bengtsson Global Energy and Climate

  6. Energy production per capita for some selected countries in 2009. Unit: MWh/year(Global average 20 MWh/year)Global total 141 PWh Lennart Bengtsson Global Energy and Climate

  7. Annual CO2 emission in Mton(Global emission: 29000 Mton in 2009) Lennart Bengtsson Global Energy and Climate

  8. Maximum physically possible energies,Wm-2Present use and future potential increase Lennart Bengtsson Global Energy and Climate

  9. Maximum physically possible energies,Wm-2Present use and future potential increase Lennart Bengtsson Global Energy and Climate

  10. What are the consequences? • Renewable energies are insufficient with the exception of a massive use of solar energy in regions like Sahara etc. • Nuclear energy can in principle do it but requires a very long lead time due to both political and technical problems • The consequence is that fossil energy will continue to be used at least well beyond 2050. Lennart Bengtsson Global Energy and Climate

  11. The facts and the questions • To provide decent living conditions for all similar to in the industrial world, we would require at least 40 MWh/year/person. • Most societies are expected to give priority to this. • In 2050 with some 9 billion people this would mean an annual energy production of 360 PWh or more than twice the present. • How can this be produced? • What are the consequences if we fail to deliver? • What are the environmental consequences? Lennart Bengtsson Global Energy and Climate

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  14. What needs to be done • I believe serious efforts must be invested to explore new more efficient and safer ways to use fission energy for energy production. • This must include a major effort to inform and educate the public and to increase scientific knowledge on all levels in society. • To enhance research on fusion energy. • Here we need a Manhattan type project. Lennart Bengtsson Global Energy and Climate

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  17. Renewable energy sourcesSolar energy • Direct solar energy ( electricity generation using photovoltaic solar cells) have generally conversion efficiency 10-20% (Weisz, 2004). ( present record, 2011 is ca 43%) • Considering energy losses in transformers, power-equalization over time and efficiency losses for conversion or transmission would require and area of 9000 km2 to generate 1 PWh/year using radiation conditions typical of US. Lennart Bengtsson Global Energy and Climate

  18. Renewable energy sourcesWind energy • The atmosphere is a very inefficient “engine” and only some 1% is converted to work (wind). Average energy density is 3 W/m2. • Modern wind turbines can produce about 800 KWh/m2/year in good locations (Hill, 2002). • Scaling this up means that we need 150 000 wind generators of 3 MW capacity to generate 1 PWh/year electric energy • Transition of energy into hydrogen gas or transmission losses might well double this figure. • Special problems are related to the large variability in production due to the weather. • Present projections indicate a contribution of some 6-10 PWh by 2030. Main limitations are the low energy density and high time variability. Lennart Bengtsson Global Energy and Climate

  19. Renewable energy sourcesBiomass-energy • 60 Gton carbon is produced annually of which some 25% may be in a form suitable for energy production. • Modern agriculture can generate 1-1.5 Kton/km2 but will require supply of reactive nitrogen. More realistic figure is 0.5 Kton/km2. • 1 PWh will thus require 7-800 000 km2 • Assuming that 25-40 % of the vegetated land area of 80 Mkm2 can be used then a primary production of 25-40 PWh/year could be achieved • Present global use together with waste (fossil fuel derivatives) amounts to some 14 PWh Lennart Bengtsson Global Energy and Climate

  20. Renewable energy sourcesHydro energy • Hydro-electricity provides presently 2.7 PWh/year or some 2% of the total energy ( but some 16% of the electricity). • Hydro electricity is totally limited and even the use of every drop of rain falling on land is actually less that the present energy production! ( first calculated by H Hertz in 1885) • Feasible extraction is probably at most 5-7 PWh/year Lennart Bengtsson Global Energy and Climate

  21. Renewable energy sourcesAdditional sources • Tidal energy • It is estimate that 3000 GW is available but only some 2% ( 60 GW or 0.125 PWh/year) can potentially be recovered from the tides. • Total contribution is likely to be less than 1 PWh/year • Geothermal energy • Here there are huge potential possibilities but large practical problems as very high investments are needed to explore the heat at great depth. • Present projections until 2030 will hardly come above 1 PWh/year Lennart Bengtsson Global Energy and Climate

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