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Realising the Potential of Solar Power

Realising the Potential of Solar Power. Peter Weightman Physics Department, University of Liverpool, Oxford Street, Liverpool. Liverpool Energy Institute. The Problem: Climate Change Current 2050 Estimates Global power need 13 TW 26 TW

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Realising the Potential of Solar Power

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  1. Realising the Potential of Solar Power Peter Weightman Physics Department, University of Liverpool, Oxford Street, Liverpool

  2. Liverpool Energy Institute The Problem: Climate Change Current 2050 Estimates Global power need 13 TW 26 TW Fossil Fuels ~ 11 TW 0 ??? Nuclear Fission 1 TW 5 TW (optimistic) Fusion 0 TW ? Other renewables < 1 TW 4 TW (optimistic) Photovoltaics 3 GW Great potential Artificial Photosynthesis 0 TW Great potential Potential: Power reaching the earth from the sun 100,000 TW (0.3 % of the sunlight reaching the Sarah Desert meets Europe’s power needs)

  3. ALICE: A New Tool “Scientific advance is more often driven by the development of a new tool than a new concept” Freeman Dyson In a review of a biography of the mathematician George Green

  4. Accelerator Sources of Terahertz Radiation 100 III-V's 10 Impatt Courtesy: J. Allen. M. Chamberlain 1 QC Laser HG 100m Gunn Output Power ( Watts ) 10m SLED 1m Average power ~ 24 mW Peak power ~ 70 kW 100µ RTD Lead salts RTD array 10µ 1µ 1000 .01 .1 1 100 10 Frequency (Terahertz ) Power of laboratory instruments At 1 THz ~ 100  watts Short electron bunches When bunch length < wavelength Coherent emission ---> massive output power Daresbury ERLP/ALICE

  5. Energy Recovery Linear Accelerator / ALICE Daresbury Liverpool THz beamline NW Science Fund: Liverpool The most intense broad band source of THz in Europe and only the 3rd in the world. 5 years under construction now commissioning

  6. . . Liverpool THz Beamline 1st Floor Tissue Culture Facility Lower level hutch for THz energy experiments Beamline funded and built by physics dept.

  7. Liverpool Energy Institute Nanocrystals: PbS (Klimov et al 2004) For h> Egcan create many excitons (MEG) To get electron and hole out attach functional organic groups h creates an electron-hole pair (exciton) Bulk semiconductors 1 hi Shockly-Queiser limit Photovolatic energy collection < 32% Due to phonon emission Improving Solar Cells Problem: Solar spectrum is broad, absorbing structures, band gaps, are narrow h, Eg, wasted h>, Eg, wasted Controversy(Science 322 1784 December 2008) Reproducibility. Exciton lifetime. Do organic groups quench MEG production? Key is to understand dynamics. Exciton energy levels are in the THz Need a high intensity THz source with good time structure: ALICE

  8. Artificial Photosynthesis Key elements: A photo receptor, often a metal complex Function: adsorb photons and release excited electrons A transducer, often organic ligands Function: transport electrons from the photo receptor to the catalytic reactor A catalytic reactor, also often a metal complex Function: reduce CO2 to CO, split H2 from H2O, or convert CO2 and H2O to formic acid HCOOH The goal is to use sunlight to create high-energy molecules which can then be recombined with other molecules to release the stored chemical energy. The principle is applied in living organisms (bacteria, plants). Harnessing it for technological applications has the potential to create cycles of energy production and consumption, which have no negative impact on the environment. So why hasn’t this been done already? Short answer: it turns out to be rather difficult. But the good news is: we know that it works. Courtesy Werner Hofer

  9. Scheme of a cell for artificial photosynthesis Antenna hn H+ H+ e- ½ H2O e- e- e- ½ H2 ½ H2O Surface Surface C CRED CRED CRED COX A D COX H+ +½ O2 C chromophore A electron acceptor D electron donor Photoelectrochemical Synthesis Cell (PES Cell) ½ H2 H+ +½ O2 Courtesy Werner Hofer

  10. Liverpool Energy Institute Concept Light induced S-S bond e transfer via Pt from S-S to N N Structural reorganisation in excited state traps the energy and prevents back electron transfer \ Recent advances in artificial photosynthesis (Julia Weinstein, University of Sheffield) Generation of very stable charge separated state in d8 organometallic system Combination of transient bond formation with long distance charge separation Key issues Chemical synthesis (electrodes?) Fast light sources to monitor transient changes in electronic and geometrical structure in real time ALICE and NLS J.A. Weinstein, M.T. Tierney, E.S. Davies, K. Base, A.A. Robeiro and M.W. Grinstaff Inorg. Chem. 45 4544 (2006)

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