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Science Vale UK energy event renewable energy technology - solar
Science Vale UK energy event renewable energy technology - solar
Science Vale UK energy event renewable energy technology - solar
Science Vale UK energy event renewable energy technology - solar
Science Vale UK energy event renewable energy technology - solar
Science Vale UK energy event renewable energy technology - solar
Science Vale UK energy event renewable energy technology - solar
Science Vale UK energy event renewable energy technology - solar
Science Vale UK energy event renewable energy technology - solar
Science Vale UK energy event renewable energy technology - solar
Science Vale UK energy event renewable energy technology - solar
Science Vale UK energy event renewable energy technology - solar
Science Vale UK energy event renewable energy technology - solar
Science Vale UK energy event renewable energy technology - solar
Science Vale UK energy event renewable energy technology - solar
Science Vale UK energy event renewable energy technology - solar
Science Vale UK energy event renewable energy technology - solar
Science Vale UK energy event renewable energy technology - solar
Science Vale UK energy event renewable energy technology - solar
Science Vale UK energy event renewable energy technology - solar
Science Vale UK energy event renewable energy technology - solar
Science Vale UK energy event renewable energy technology - solar
Science Vale UK energy event renewable energy technology - solar
Science Vale UK energy event renewable energy technology - solar
Science Vale UK energy event renewable energy technology - solar
Science Vale UK energy event renewable energy technology - solar
Science Vale UK energy event renewable energy technology - solar
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Science Vale UK energy event renewable energy technology - solar

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The Energy of Science Vale UK - 26 May 2011. Solar Renewable Energy Technology presentation by Nicholas Harrison (Imperial College, London). More details at www.sciencevale.com …

The Energy of Science Vale UK - 26 May 2011. Solar Renewable Energy Technology presentation by Nicholas Harrison (Imperial College, London). More details at www.sciencevale.com

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  • 1. Renewable Energy (Solar) Nicholas M Harrison Imperial College London Daresbury Laboratory The Rutherford Appleton Laboratory
  • 2. Scale of the Problem: Supply
  • 3. Renewables and Climate Change COP-15 is widely considered a failure, as it did not result in binding CO2 - reduction targets. Nevertheless, COP-15 lead to global acceptance of the 2oC target as maximum permissible warming; more will definitely result in climate- disaster. This means, the world cannot emit more than 750 Gt of CO2 during this century; it currently emits about 35 Gt of CO2 per year (9.5 Gt C/a) !
  • 4. Hydroelectric Geothermal BiomassSolar Ocean Wind Renewable Capacity
  • 5. Hydroelectric Gross: 4.6 TW Technically Feasible: 1.6 TW Economic: 0.9 TW Installed Capacity: 0.6 TW Renewable Capacity
  • 6. Geothermal Mean flux at surface: 0.057 W/m2 Continental Total Potential: 11.6 TW
  • 7. Biomass 50% of all cultivatable land: 7-10 TW (gross) 1-2 TW (net)
  • 8. Solar potential 120,000 TW; practical > 600 TW ?
  • 9. 6 Boxes at 3.3 TW Each (graphic courtesy of Nate Lewis) Solar Land Area Requirements
  • 10. Electricity Production Costs
  • 11. CO2 - free sources of energy Nuclear energy - non-renewable feedstock, final storage ?, risks ? Clean coal technologies - requires carbon sequestration, unproven technology and energy inefficient Wind - fluctuating production, limited number of suitable sites – offshore ? Hydro - can be switched on instantaneously, suitable for storage, good sites limited, production should be maximized Biofuels – interesting liquid fuel for transport, production energy intensive Geothermal - excellent where easily accessible Solar energy (Photovoltaics, Solarthermal) - unlimited energy source PV: continuous price reduction through savings of scale
  • 12. Price learn-curve of crystalline Si PV- modules Slide courtesy of G Willeke
  • 13. DESRTEC-EUMENA
  • 14. Research Landscape Large international investment in research and development Strong focus on optimisation of existing systems => The opportunity is for step change in cost and / or efficiency
  • 15. STFC Current collaborative international projects: – High efficiency photovoltaics (inorganic) – Fundamentals of solar hydrogen production – Dye sensitised nano-oxides – Rectenna arrays
  • 16. Light Fuel Electricity Photosynthesis Fuels Electricity Photovoltaics SC e SC CO Sugar H O O 2 2 2 Semiconductor/Liquid Junctions H2O O H 22 SC Energy Conversion
  • 17. Performance of photovoltaic and photochemical solar cells Type of cell Efficiency (%)* Cell Module Research and technology needs Crystalline silicon 24 10-15 Higher production yields, lowering of cost and energy content Multicrystalline silicon 18 9-12 Lower manufacturing cost and complexity Amorphous silicon 13 7 Lower production costs, increase production volume and stability CuInSe2 19 12 Replace indium (too expensive and limited supply), replace CdS window layer, scale up production Dye-sensitized nanostructure materials 10-11 7 Improve efficiency and high-temperature stability, scale up production Bipolar AlGaAs/Si photochemical cells 19-20 - Reduce material cost, scale up Organic solar cells 2-3 - Improve stability and efficiency M. Grätzel, Nature 415, 338 (2001) Status
  • 18. Ultimate Efficiency Limits Thermodynamic limit of Carnot engine: η = 1 – T0/Ts ~ 95% (100% absorption) Shockley-Queisser efficiency limit for single band semiconductor based on detail balance eq.: ~31% (1 sun: Planck low) and ~41 (max conc.) Origin of the solar cell losses: a) Light with energy below Eg will not be absorbed b) The photons with excess energy above Eg is lost in the form of heath c) Single crystal GaAs solar cell ~ 25%(AM1.5)
  • 19. Multijunction or tandem cells: • First approach to exceed single junction efficiency • To achieve >50% efficiency need 3 or more tandems with different Eg’s • Significant technological problem to relax strain • 75% efficiency achieved with 36 tandems Tandem solar cells No of junctions 1 sun Max conc. 1 30.8% 40.8% 2 42.9% 55.7% 3 49.3% 63.8%  68.2% 86.8%
  • 20. High-efficiency ISE triple-junction solar cells Ga0.65In0.35P tunnel diode Ga0.83In0.17As tunnel diode Ge substrate
  • 21. Intermediate band solar cells Multi-junction solar cell • Each junction  single gap • N- junctions  N- absorptions Multi-band solar cell Single junction (no lattice mismatch) N- bands  N(N-1)/2 (gaps) Add 1 band  Add N- absorptions
  • 22. Intermediate band solar cells Intermediate band vs multi-junction solar cell • Max. efficiency for 3 band cell ~66% (vs 55%) • Max. efficiency for 4 band cell ~72% (vs 60%) • Better performance than any other structure of similar complexity A. Luque & A. Marti, Phys. Rev. Lett 78, 5014 (1997)
  • 23. Requirements & Possible Realization Designing a materials system: Finite width IB to allow excitations VB-IB, IB-CB Narrow IB to reduce carrier transport Predictive simulations yield QD arrays as an excellent candidate QD arrays produce an IB with zero density of states between VB & IB & CB, which increases the radiative lifetime relative to the relaxation time within bands.
  • 24. Current technology Vertical ordering is provided by strain driven alignment Horizontal regularity of QD’s is observed on high Miller index surfaces Q. Xie, et al., Phys. Rev. Lett. 75, 2542 (1995) S. Tomic, NMH et al., J. Appl. Phys. 99, 093522 (2006) Y. Okada, private communication
  • 25. Solar Hydrogen Detailed understanding of: – Excitation – Transport – Surface dynamics – Reduction reaction EPSRC EP/G060940/1 Nanostructured Functional Materials for Energy Efficient Refrigeration, Energy Harvesting and Production of Hydrogen from Water. Programme grant Oct 2009.
  • 26. Rectenna Arrays An array of nanostructured antennas for supported on metal-insulator-insulator-metal diodes
  • 27. Conclusions Solar energy will be a significant component of the energy mix by 2050 Significant scientific / technological breakthroughs required to ease the transition Very large international research and development effort – the current opportunity is in step change

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