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Biomass conversion, IV curve, wind mapping

Short answer

Biomass conversion includes combustion, gasification, pyrolysis, anaerobic digestion to biogas, fermentation, and transesterification. Solar cell I-V: temperature rise drops Voc ~2.2 mV/°C, power decreases ~0.4%/°C. Wind mapping uses met stations, masts, remote sensing and models to create wind speed maps; Nepal's SWERA mapped potential, e.g. Mustang.

What are the various biomass conversion processes? Explain the IV curve for solar photovoltaic cell with temperature variation. How can you have the wind mapping data? Explain in brief.

1. Biomass conversion processes

Biomass is organic matter (wood, crop residue, dung, waste) used as an energy source.

  1. Direct combustion: burning for heat, steam and power; includes briquettes and pellets.
  2. Thermo-chemical conversion:
    • Gasification: partial combustion at 800–1000 °C gives producer gas (CO, H₂, CH₄) for engines and heat.
    • Pyrolysis: heating without oxygen gives bio-oil, charcoal and gas.
    • Carbonisation to charcoal.
  3. Bio-chemical conversion:
    • Anaerobic digestion: bacteria produce biogas (CH₄ 55–65%, the rest mostly CO₂) and slurry manure.
    • Fermentation: yeast converts sugars to ethanol.
  4. Chemical conversion: transesterification of oils into biodiesel.

2. I-V curve of a solar PV cell with temperature variation

The I-V curve shows current against voltage at a given irradiance. Key points: Isc, Voc and the maximum power point.

 I |==.        25 C
   |   '.==.   50 C
   |       ' '.  75 C
   +---------------- V
   (curves shift left as T rises)
  • With rising temperature, the open-circuit voltage falls (about −2.2 mV/°C per silicon cell, or −0.3 to −0.4% per °C for a module).
  • The short-circuit current rises slightly (about +0.05% per °C) as the band gap narrows.
  • Net effect: the maximum power and fill factor decrease (about 0.4–0.5% per °C above 25 °C). Cells therefore work better in cool, clear conditions (the cold, sunny Himalayan climate is good for PV).

3. Wind mapping data

Wind mapping gives wind speed and power density across a region to find good sites. Data come from:

  • Meteorological stations (anemometers at 10 m height), with long-term records from the Department of Hydrology and Meteorology.
  • Measurement masts (30–80 m, with anemometers, wind vanes and data loggers) at candidate sites for at least one year.
  • Remote sensing: LIDAR and SODAR, and satellite data.
  • Numerical models and reanalysis data (wind atlas models such as WAsP, mesoscale models), calibrated with ground measurements.
  • Results are shown as wind speed and wind power density maps (W/m²), using a Weibull distribution. Nepal's wind resource was mapped by AEPC with international support in the Solar and Wind Energy Resource Assessment (SWERA, 2008). The usable potential is small, commonly quoted as about 3,000 MW at best, mainly in Mustang (for example the Kagbeni area) and some hill ridges and Tarai/Siwalik areas.

✓ Answer checked by Claude Opus 5.5 (high effort)

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