--- title: "Biomass conversion, IV curve, wind mapping" subject: "Energy Environment and Society" chapter: 3 key: "semester_7/energy_environment_and_society:biomass-iv-curve-wind-mapping" source: https://www.bctengineer.com/q/semester_7/energy_environment_and_society/biomass-iv-curve-wind-mapping site: BCT Engineering --- # Biomass conversion, IV curve, wind mapping Energy Environment and Society · Chapter 3: Renewable Energy Sources - Asked in: 2071 Chaitra, 8 marks - Video: [Types of Biofuels, Energy conversion routes from biomass](https://www.youtube.com/watch?v=2ZG2CyknGCg) — Vidya-mitra - Answer checked by Claude Opus 5.5 (high effort) on 2026-10-14 - Page: https://www.bctengineer.com/q/semester_7/energy_environment_and_society/biomass-iv-curve-wind-mapping - Whole chapter: https://www.bctengineer.com/md/semester_7/energy_environment_and_society/chapter-3 ## Question 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. ## 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. ## Answer #### 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. ```text 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. ## Check yourself The answer's key points as multiple-choice questions, with the correct option and why. 1. What distinguishes gasification from pyrolysis? A. Gasification heats biomass with no oxygen; pyrolysis uses partial combustion B. Gasification partially burns biomass at 800-1000 °C to give producer gas; pyrolysis heats without oxygen to give bio-oil, charcoal and gas C. Both need bacteria in the absence of air D. Gasification gives biodiesel; pyrolysis gives ethanol Answer: B. Gasification uses limited oxygen (partial combustion) to make CO, H2, CH4 producer gas, while pyrolysis uses no oxygen. (Key point: Gasification) 2. Which pair belongs to bio-chemical conversion of biomass? A. Anaerobic digestion and fermentation B. Gasification and pyrolysis C. Direct combustion and briquetting D. Transesterification and carbonisation Answer: A. Bacteria and yeast drive anaerobic digestion (biogas) and fermentation (ethanol). (Key point: Bio-chemical conversion) 3. As the temperature of a PV cell rises at constant irradiance, what happens to Voc and Isc? A. Voc rises sharply, Isc falls B. Both fall equally C. Both rise equally D. Voc falls noticeably, Isc rises slightly Answer: D. Voc drops (about -2.2 mV/°C per silicon cell) while Isc increases slightly (about +0.05%/°C) as the band gap narrows. (Key point: Effect of temperature on PV I-V curve) 4. How is wind mapping data for a candidate site obtained and made reliable? A. Only from solar irradiance records B. Only from satellite data without ground checks C. Measurement masts (30-80 m) for at least a year, met stations, remote sensing and models calibrated with ground measurements D. A single day of anemometer reading at 2 m height Answer: C. Mapping combines masts, stations, LIDAR/SODAR/satellite and models, calibrated against ground measurements. (Key point: Wind mapping data sources) ## Related in Energy Environment and Society - [Characteristics curve of solar cell](https://www.bctengineer.com/question.md?key=semester_7%2Fenergy_environment_and_society%3Asolar-cell-characteristics-curve) — Energy Environment and Society, chapter 3 - [Biomass and conversion routes](https://www.bctengineer.com/question.md?key=semester_7%2Fenergy_environment_and_society%3Abiomass-conversion-routes) — Energy Environment and Society, chapter 3, asked 3× - [Thermo-chemical conversion of biomass](https://www.bctengineer.com/question.md?key=semester_7%2Fenergy_environment_and_society%3Athermochemical-conversion-biomass) — Energy Environment and Society, chapter 3 - [Bio-chemical conversion of biomass](https://www.bctengineer.com/question.md?key=semester_7%2Fenergy_environment_and_society%3Abiochemical-conversion-biomass) — Energy Environment and Society, chapter 3 - [Solar radiation, solar cell and plant](https://www.bctengineer.com/question.md?key=semester_7%2Fenergy_environment_and_society%3Asolar-radiation-cell-plant) — Energy Environment and Society, chapter 3 - [Solar cell principle and applications](https://www.bctengineer.com/question.md?key=semester_7%2Fenergy_environment_and_society%3Asolar-cell-principle-applications) — Energy Environment and Society, chapter 3 ## Related in other subjects - [Biochemical conversion of biomass to fuels](https://www.bctengineer.com/question.md?key=semester_6%2Fenergy_resources%3Abiomass-biochemical-conversion) — Energy Resources, chapter 3 - [Wind energy conversion options and characteristics](https://www.bctengineer.com/question.md?key=semester_8%2Fpower_plant_design%3Awind-conversion-options) — Power Plant Design, chapter 1 - [Solar generation and wind power characteristics](https://www.bctengineer.com/question.md?key=semester_8%2Fpower_plant_design%3Asolar-generation-wind-characteristics) — Power Plant Design, chapter 1 - [Compatibility condition; portal frame temperature variation](https://www.bctengineer.com/question.md?key=semester_5%2Ftheory_of_structures_ii%3Acompatibility-condition-portal-temperature) — Theory of Structures II, chapter 2