Appropriate Technology

• Characteristics, seven points. Requires fewer resources; meets the actual needs of the people; lower cost; uses renewable energy; less environmental impact; labour intensive; light capital.
• Six criteria to judge it. Ask questions under each heading:
  • Technical: is the technology mature, suited to local geography and climate, built on locally known technology, using local materials and energy?
  • Economic: are investment and maintenance costs low, is hard-currency investment minimised, are benefits enjoyed locally?
  • Social: are local people in the decision making, are existing skills used, is local labour used, is the impact gradual rather than sudden?
  • Cultural: is the technology culturally sensitive, is there ongoing dialogue with the community, is plurality of cultures considered?
  • Environmental: is local and global damage minimised, can renewable energy be used, is it environmentally sustainable?
  • Political: does it avoid reliance on non-local support, does it strengthen the local area, are the poor the beneficiaries?
• Development goals it serves. Maximise output and availability of consumption goods, maximise rate of economic growth, reduce unemployment, regional development, reduce balance-of-payment deficit, greater equity in income distribution, promote political development, improve quality of life.
• Role in transforming society, give sector examples.
  • Building: natural ventilation, fans instead of air conditioning, green building materials.
  • Agriculture: compost manure, human and animal power.
  • Water supply: SODIS solar disinfection, ceramic filters, rainwater harvesting, fog-water collection.
  • Sanitation: composting toilets, constructed wetlands, sand filters.
  • Energy: micro and pico hydro, solar thermal collectors, low-cost PV, biogas.
  • Transport: human-powered bicycles and tricycles, animal carts.
  • Health / finance / ICT, herbal medicine and birth control; micro-finance and cooperatives; low-cost computers and fibre optics.
• Appropriate vs indigenous technology (asked 2075 Chaitra). Indigenous technology is traditional knowledge developed locally over generations and passed down: water mill (ghatta), thatched roofing, mud stove. Appropriate technology is deliberately selected or designed to fit local conditions and may borrow modern science: improved water mill, improved cookstove, solar dryer. All indigenous technology is local, but not all of it is appropriate; appropriate technology may improve or replace it.

Technology Transfer

• Driven by push and pull. Supply pushes and demand pulls, both forces initiate transfer.
• Three critical events. Idea → Prototype → Product. Transformation of technology into product is the whole point.
• Ways technology is transferred. Consulting; graduating students and faculty moving on (“moving heads”); collaborative research; patenting and licensing; service and outreach or extension; spin-off companies.
• It is a process, not an event. It has stages and phases; it works at different levels from national technology policy down to individual scientists; it involves different stakeholder perspectives (developers and users), therefore it is fundamentally a communication process.
• Importance, five headings.
  • Economic development, modest development in developing countries needs appropriate technology to sustain the economy and minimise poverty.
  • Economic diversification, why invent when we can borrow; the donor also gains benefits it would not otherwise receive.
  • Future markets: the donor's home market is saturated, so transfer opens business expansion.
  • Reverse engineering: cheaper and easier to test and research in developing countries, and feedback returns to the donor.
  • Psychological well-being, world order and peace, transfer keeps developing countries occupied with infrastructure and welfare instead of conflict.

Impact of Technology on Society

• If the question says “on environment” (2078 Bhadra) split it the same way. Positive: cleaner production processes, renewable energy technologies, remote sensing and monitoring of pollution, efficient use of resources, waste treatment and recycling. Negative: air and water pollution, greenhouse gas emission, e-waste, deforestation, resource depletion, habitat and biodiversity loss.
• Close with the balance argument. Technology itself is neutral; the impact depends on which technology is chosen and how it is used, which is exactly why appropriate technology matters.

Energy and Maslow's Hierarchy of Needs

• Maslow (1943) wanted to understand what motivates people. He held that people are motivated to achieve certain needs, and when one need is fulfilled a person seeks to fulfil the next.
• The five levels, bottom to top, with the energy behind each:
  • 1. Biological and physiological: air, food, drink, shelter, warmth, sleep. Energy for cooking, water pumping, space heating.
  • 2. Safety: protection from the elements, security, order, law, stability, freedom from fear. Street lighting, refrigerated medicine, secure buildings, early-warning systems.
  • 3. Love and belongingness: friendship, intimacy, affection, family and work group. Telecommunication, transport, lighting for social gathering, internet.
  • 4. Esteem: achievement, mastery, independence, status, prestige, self-respect. Electricity for education and computers, productive appliances, income generation.
  • 5. Self-actualisation: realising personal potential, self-fulfilment, personal growth, peak experience. Research, ICT, mobility, creative work.
• The sentence that earns the mark. Energy is the essential input to fulfil the basic needs of food, shelter and warmth, which form the base of the pyramid. Without fulfilling the basic needs one cannot go beyond them, therefore energy is an important input in achieving Maslow's hierarchy of needs.

Human Development Index and Energy Consumption

• Four tiers. Very high, high, medium and low human development.
• Three dimensions. Life expectancy, a long and healthy life. Education index, mean and expected years of schooling. Income index: a decent standard of living, measured by GNI per capita.

• The relation with energy is positive but saturating. HDI rises steeply with per-capita energy use at low consumption, then flattens. Beyond roughly 2,400 kgoe per person (about 4,000 kWh per capita of electricity) extra energy buys almost no extra HDI.
• What that means for a developing country. Nepal sits on the steep part of the curve, so a small increase in per-capita energy produces a large gain in health, education and income. Developed countries on the flat part gain nothing from more energy, they should pursue efficiency instead.
• Factors affecting HDI (asked 2076 Ashwin). Health and life expectancy, education access and quality, income and GNI per capita, plus underlying drivers: energy access, inequality, gender equity, governance and environmental quality.

Energy Trends, Demand and Supply, Nepal and the World

• Nepal's defining feature: traditional biomass dominates. Fuelwood, agricultural residue and animal dung supply the bulk of primary energy. Commercial energy is a minority share and all petroleum is imported, mostly from India.
• Consumption is overwhelmingly residential. Residential 80.36 %, industrial 7.89 %, transport 7.12 %, commercial 3.43 %, agriculture 1.17 %, others 0.03 %, total 376.3 million GJ (WECS).
• Hydropower numbers worth quoting. Theoretical potential 83,290 MW; technically feasible 45,610 MW; installed small, medium and large hydro 762 MW, mini-hydro 15.95 MW, micro-hydro 18.65 MW, pico 3.18 MW.
• World picture. Fossil fuels met 81 % of world energy needs in 2005. Nuclear fission supplied about 5.7 % of world energy and 13 % of world electricity in 2011.
• Current global trends: five bullets. Oil price fluctuation; growth in the solar industry; reduction of coal in developed countries; renewed research in nuclear power; rapid development of energy storage (battery, fuel cell).
• Nepal's trend today. Load shedding has ended and generation now exceeds wet-season demand, so the problems have shifted to transmission capacity, dry-season deficit and export markets, and to electrifying cooking and transport to cut the petroleum import bill.

Global Warming and the Greenhouse Effect

• Natural vs human-enhanced greenhouse effect. Naturally, some re-radiated heat escapes to space and the earth stays habitable. With extra GHGs, less heat escapes and more is re-radiated back to the surface, that difference is the human-enhanced greenhouse effect.
• The greenhouse gases. Carbon dioxide, methane, nitrous oxide, chlorofluorocarbons, water vapour and tropospheric ozone.
• Causes. Fossil fuel combustion for power and transport, deforestation, livestock and paddy agriculture, industrial processes, landfill emissions, and refrigerant release.
• The agreed target. Parties to the UNFCCC agreed that deep cuts are required and warming should be limited to well below 2.0 °C above pre-industrial levels, with efforts to limit it to 1.5 °C.
• How Nepal is affected. Glacier retreat and glacial lake outburst floods (GLOF), erratic and intense monsoon, drought and drying springs, landslides and floods, upward shift of agro-climatic zones, loss of biodiversity, and black carbon deposition on snow.
• How Nepal is planning to tackle it. Nationally Determined Contribution with a net-zero target for 2045; NAPA and local adaptation plans (LAPA); Climate Change Policy; community forestry and REDD+; promotion of renewables through AEPC; electric vehicle policy and hydro-based electrification of cooking.
• “How can you slow global warming: three examples.” Replace fossil generation with hydro and solar; improve efficiency (LED lighting, improved cookstoves, efficient motors); afforestation and REDD+; shift transport to electric vehicles and mass transit; replace fuelwood with biogas.

Clean Development Mechanism and the Kyoto Protocol

• How it works between two groups. It supports greenhouse gas emission reduction through co-operation between developed countries (Annex I parties), which are committed to emission reduction targets, and developing countries (non-Annex I parties), which carry no commitment.
• Two objectives, state both. To assist non-Annex I parties in achieving sustainable development and contributing to the UNFCCC objective of preventing dangerous climate change; and to assist Annex I parties in achieving compliance with their quantified emission limitation and reduction commitments.
• Kyoto Protocol facts to quote. An international treaty extending the 1992 UNFCCC. Adopted at Kyoto, Japan on 11 December 1997, entered into force 16 February 2005, 192 parties. It sets binding targets for 37 industrialised countries and the European Community, averaging 5 % below 1990 levels over the 2008 to 2012 commitment period. Its premise: global warming exists, and human-made CO₂ emissions have caused it.
• The flexibility mechanisms. Clean Development Mechanism, Joint Implementation, Emission Trading, alongside domestic actions and assigned amounts.
• Potential CDM areas in Nepal. Household biogas plants (Nepal's Biogas Support Programme is a real registered CDM project), improved cooking stoves, micro-hydro, solar home systems, community forestry and REDD+, municipal waste management, and electric transport.
• Link to the SDGs (asked 2075 Chaitra). CDM projects deliver SDG 7 affordable clean energy, SDG 13 climate action, SDG 3 health through cleaner indoor air, SDG 8 decent work, and SDG 15 life on land.

Solar Radiation: the Five Definitions

• Solar radiation. The total frequency spectrum of electromagnetic radiation produced by the sun, covering visible light and near-visible radiation such as X-rays, ultraviolet, infrared and radio waves.
• Irradiance, I. The intensity of solar radiation per unit time on a unit surface area of the earth. Unit W/m².
• Insolation. The total energy received from the sun in a day on a unit surface area on earth. Unit Wh/m²/day. For Nepal the yearly average is about 4,500 to 5,500 Wh/m²/day.
• Solar constant. A measure of flux density, the measured solar electromagnetic radiation per unit area incident on a plane perpendicular to the rays at a distance of one astronomical unit from the sun. Value about 1,367 W/m².
• Peak sun. The hypothetical equivalent number of hours which, at full intensity, delivers the same energy as the whole day. A site with 5 kWh/m²/day insolation has 5 peak sun hours. PV designers size arrays with this number.
• Global radiation. The total short-wave radiation from the sky falling on a horizontal surface. It includes direct (beam) radiation plus the diffuse radiation resulting from reflected or scattered sunlight.

• Projection effect, the cosine law. Insolation is largest when the surface faces normal (perpendicular) to the sun. As the angle moves away from normal, insolation is reduced in proportion to the cosine of the angle. A one-mile-wide beam striking at 30° spreads its energy over two miles of ground, so intensity halves.
• Factors affecting solar intensity at a site. Latitude; season and solar declination; time of day; tilt and orientation of the surface; atmospheric condition: cloud, dust, humidity, pollution; altitude; air mass; and shading.

Solar PV Cell: Working Principle

• Three basic attributes required for operation: the examiner wants these three verbatim:
  • The absorption of light, generating either electron-hole pairs or excitons.
  • The separation of charge carriers.
  • The separate extraction of those carriers to an external circuit.
• Step-by-step working. Photons in sunlight strike the panel and are absorbed by the semiconducting material, usually silicon. Electrons are excited out of their molecular atomic orbital. Once excited, an electron either dissipates the energy as heat and returns to its orbital, or travels through the cell until it reaches an electrode. Current then flows through the material to cancel the potential, and this electricity is captured.
• Why two doped layers. Silicon is used in two layers, one doped with boron (p-type) and the other with phosphorus (n-type). The layers carry different chemical electric charges, and this difference both drives and directs the current of electrons.
• Output. An array of solar cells converts solar energy into a usable amount of direct current (DC). An inverter converts it to alternating current where AC loads are used.
• Cell, module, panel, array. One crystalline silicon cell gives only 0.5 to 0.6 V independent of cell area at 25 °C, while its current depends on cell area and irradiance. Cells are wired in series to form a module; modules are wired into panels and arrays in series or parallel to reach the required voltage and current. A modern 15 cm × 15 cm cell gives up to 4 W and 8 A in full sunlight, and 86 % of modules are crystalline silicon.
• Series and parallel rules. In series the voltages add but current is limited by the weakest device. In parallel the currents add and voltage is the average. This is why partial shading of one module cripples a whole string.

• IV characteristics: label five things. Short-circuit current I_SC, open-circuit voltage V_OC, the maximum power point (V_m, I_m), maximum power P_max, and the knee of the curve.

• Effect of temperature (asked 2071 Chaitra). As cell temperature rises, V_OC falls appreciably while I_SC rises very slightly, so the net output power falls, roughly 0.4 % per °C for crystalline silicon. Higher irradiance mainly raises I_SC in proportion.

Solar Thermal Energy and Heating Systems

• Rooftop solar water heater, two arrangements.
  • Pumped. The absorber is a steel plate bonded to copper or steel tubing through which water circulates. The plate is sprayed with special black paint or a selective surface to maximise absorption, covered with a single sheet of glass or plastic, and insulated at the back to cut heat loss. A pump drives circulation, so the tank can sit anywhere.
  • Thermosyphon. Relies on the natural convection of water rising from the collector panel to carry heat up to the storage tank, which must be installed above the collector. No heat exchanger is needed because the domestic hot water circulates directly through the panel. No pump, no electricity, hence the common Nepali rooftop type.
• Varieties of solar heating system, name all four. Swimming pool heating; conservatory or sunspace; Trombe wall; direct gain.
• Solar dryer. A glazed insulated chamber where solar-heated air passes over the crop, removing moisture faster and more hygienically than open sun drying, with less spoilage and no dust or insects.
• Solar water pumping. PV array → controller or variable-frequency drive → DC or AC motor pump → overhead tank for storage. Limitations: output follows the sun so pumping stops at night and falls on cloudy days; storage is by water tank, not battery; high initial cost; needs a reliable water source; risk of theft and low local maintenance capacity; fixed output cannot follow a sudden demand peak.
• Solar thermal power plants. Concentrating collectors: parabolic trough, central receiver power tower, dish-Stirling, raise steam for a conventional turbine. Suited to high direct-beam desert sites, not to Nepal's hazy hill climate.

Hydropower: Principle, Classification and Layout

• Classification by capacity, memorise the six bands.
  • Pico hydro, under 5 kW
  • Micro hydro, 5 kW to 100 kW
  • Mini hydro, 100 kW to 1 MW
  • Small hydro, 1 MW to 25 MW
  • Medium hydro, 25 MW to 100 MW
  • Large hydro, greater than 100 MW
• Classification by scheme. Run-of-river (no storage, output follows river flow: most of Nepal's plants), peaking run-of-river (small pondage for evening peak), storage or reservoir type, and pumped storage.
• Gross head vs net head. Gross head is the vertical distance between the forebay water level and the turbine centreline. Net head = gross head − head losses in the intake, headrace, forebay and penstock (friction, bends, valves, trash rack). Only net head produces power.
• Minimum constructional requirements (asked 2070 Chaitra): adequate head and dependable flow proven by hydrology; diversion weir and intake; desilting or settling basin; headrace canal or tunnel; forebay tank with spillway; penstock with anchor blocks and support piers; powerhouse with turbine, generator and control panel; tailrace back to the river; transmission line and substation; access road and land acquisition.
• Why micro-hydro is sustainable in a rural area (asked 2074 Ashwin): renewable and non-depleting resource; no fuel cost and no emissions; built with local materials and local labour; owned and maintained by a community cooperative; small civil works so little inundation or resettlement; enables local end-uses: mills, lighting, ICT; replaces kerosene and fuelwood; and life of 20 to 25 years with modest maintenance.

Water Turbines: Impulse vs Reaction

• Impulse turbine. A turbine in which the expansion of the fluid is completed in a static nozzle, the torque being produced by the change in momentum of the fluid impinging on the curved rotor blades. Examples: Pelton, Cross-flow, Turgo.
• Reaction turbine. A turbine in which the working fluid is accelerated by expansion in both the static nozzles and the rotor blades. Torque is produced by momentum changes in the rotor and by reaction from fluid accelerating out of the rotor. Examples: Francis, Propeller, Kaplan.

• Kaplan detail worth a mark. A propeller-type turbine with adjustable blades, combining automatically adjusted propeller blades with automatically adjusted wicket gates to hold efficiency over a wide range of flow and water level.
• How turbine choice relates to plant capacity (asked 2080 Bhadra). Capacity follows head and flow. High-head, low-flow Himalayan sites give large power from small flow and use Pelton; medium-head mid-hill sites use Francis; low-head, high-flow Terai and river-bed sites need Kaplan or propeller. Micro-hydro below 100 kW commonly uses cross-flow because it is cheap and locally manufacturable.

Wind Turbines, Wind Parks and Power Control

• Definition. Wind power is the use of air flow through wind turbines to mechanically power generators for electric power. Wind machines use blades to collect the wind's kinetic energy; windmills work because they slow down the speed of the wind. The blades connect to a drive shaft that turns an electric generator.
• Also called. Wind energy conversion systems (WECS), wind generators, or aero-generators.
• Two types of wind machine by shaft direction.
  • Horizontal axis (HAWT): the common three-blade machine; higher efficiency, must be yawed into the wind, gearbox and generator sit in the nacelle on a tall tower.
  • Vertical axis (VAWT): Darrieus and Savonius types; accepts wind from any direction so needs no yaw, gearbox and generator at ground level for easy maintenance, but lower efficiency and often not self-starting.
• Main components to label. Rotor blades, hub, nacelle, low-speed shaft, gearbox, high-speed shaft, generator, brake, yaw drive and motor, anemometer and wind vane, controller, tower, transformer.
• Wind parks. A group of wind turbines in the same location used to produce electricity. A large wind park may consist of several hundred individual turbines covering hundreds of square miles, but the land between the turbines may still be used for agriculture or other purposes.
• Power control methods. Pitch control, blades rotate about their axis to shed power above rated wind speed. Stall control, blade profile is designed to stall passively at high wind. Yaw control, turns the rotor into or out of the wind. Plus mechanical and electrical braking, and the three speeds: cut-in (about 3 to 4 m/s), rated (12 to 15 m/s) and cut-out (about 25 m/s).
• Advantages. Plentiful, renewable, widely distributed, clean, produces no greenhouse gases during operation, consumes no water, and uses little land.
• Disadvantages and environmental impacts. Intermittent and site-specific; noise; bird and bat strike; visual impact on landscape; shadow flicker; electromagnetic interference with communication; land use during construction; high capital cost and difficult transport of blades in hill terrain.
• Applications in Nepal. Measured potential of the order of 3,000 MW in windy corridors: Mustang and the Kali Gandaki valley, Kagbeni, Chisapani, Ramechhap and some Terai belts. Practical uses so far are solar: wind hybrid systems for telecom towers, small battery-charging turbines, and wind pumps for irrigation. Limitations: seasonal and localised wind, rugged terrain, transport of large components, and lack of a fine-resolution wind atlas.

Geothermal Energy: Sources, Harnessing and Uses

• Where the resource sits. Resources range from the shallow ground, to hot water and hot rock a few kilometres beneath the surface, down to the extremely high temperatures of molten rock called magma.
• Three ways it is harnessed, the standard three-part answer.
  • Generating electricity from the earth's heat, geothermal power production.
  • Geothermal direct use, producing heat directly from hot water within the earth.
  • Geothermal heat pumps, using the shallow ground to heat and cool buildings.
• Classification of resources. Hydrothermal → dry steam, wet steam, hot water fields. Petrothermal → porous rock and hot dry rock. Magma resources → volcanoes. Geopressure.
• Three power plant designs. All pull hot water and steam from the ground, use it, and return it as warm water to prolong the life of the heat source.
  • Dry steam, steam from the reservoir drives the turbine directly.
  • Flash steam, high-pressure hot water is flashed to steam by a pressure drop.
  • Binary cycle: moderate-temperature water heats a secondary working fluid of low boiling point, which drives the turbine. Best for low-enthalpy resources.
• Hot dry rock technology, six steps. Wells drilled 3 to 6 km into the crust; hot crystalline rock formations located; water pumped into the formations; water flows through natural fissures picking up heat; hot water or steam returns to the surface; steam used to generate power.
• Applications, five. Generation of electric power; industrial process heat; food processing; space heating for buildings; bathing facilities.
• Environmental impacts: four groups. Land: vegetation loss, soil erosion, landslides. Water: watershed impact, damming streams, hydrothermal eruptions, lowered water table. Air: slight air heating, local fogging. Ground: reservoir cooling, induced seismicity.
• Positive attributes. Available 24 hours a day regardless of weather so it gives high capacity factor and base load; small land footprint; no fuel cost; very low emissions compared with fossil plants; the resource is effectively inexhaustible if reinjection is practised.
• Nepal context. Around 32 hot springs are recorded along the Main Central Thrust: Tatopani in Myagdi and Sindhupalchowk, Jomsom, Singha. These are low-enthalpy resources, so the realistic use is direct heating, greenhouse and drying, and bathing, rather than power generation.

Biomass: Definition, Types and the Four Conversion Routes

• Three types by origin.
  • Forest waste: saw dust, leaves, twigs, shrubs, residues of herbs and herbal products.
  • Agricultural residues: rice husk, rice straw, rice bran, wheat husk, wheat straw, wheat bran, maize cobs, maize stalks, sugarcane leaves.
  • Industrial waste and residues: sugarcane bagasse, coffee husk, tobacco waste, tea waste, herbal residue.
• The four major conversion routes, this exact list is asked repeatedly.
  • Thermo-chemical conversion: direct combustion, pyrolysis, gasification, liquefaction.
  • Bio-chemical conversion: alcoholic fermentation, anaerobic digestion.
  • Physical conversion: size reduction, drying, screening, densification and briquetting.
  • Agro-chemical conversion, extraction of exudates from living or freshly cut plants.
• Synthetic fuel (synfuel). A liquid or gaseous fuel obtained from syngas, a mixture of carbon monoxide and hydrogen: where the syngas is derived from gasification of solid feedstock such as coal or biomass, or by reforming natural gas.
• Common sources of biomass in Nepal (asked 2078 Bhadra). Fuelwood from forest and private land; cattle and buffalo dung; crop residue: rice straw and husk, maize stalks, wheat straw; sugarcane bagasse from mills; municipal organic waste; and invasive species such as banmara.

Hydrogen as a Fuel: Safety, Production and Storage

• Safety aspects: the four slide points. Hydrogen is lighter than air and vanishes rapidly upwards; it has a high diffusion coefficient, four times that of methane, so it dilutes rapidly in air; it burns with an invisible flame with very little heat radiated from the flame; it is colourless and odourless.
• The safety trade-off, say both sides. Rapid dispersal and low radiant heat make a leak less dangerous than petrol in the open. But the invisible flame is hard to detect, the flammability range is very wide (4 to 75 %), the ignition energy is very low, there is no odour to warn of leaks, and it causes hydrogen embrittlement of metals. Storage at 350 to 700 bar or at −253 °C adds its own hazard, so detectors, ventilation at high level and careful material selection are mandatory.
• Five production methods. Steam reforming of natural gas; coal gasification; biomass gasification; electrolysis of water; thermolysis and thermo-chemical cycles.
• Four storage methods. Compressed hydrogen storage; liquid hydrogen storage; hydride storage (metal hydrides absorb and release hydrogen); carbon nanotubes.
• Advantages. The only emission when burned is water vapour, so no carbon dioxide is produced. Hydrogen has the potential to run a fuel cell engine with greater efficiency than an internal combustion engine. The same amount of hydrogen will take a fuel cell car at least twice as far as a car running on gasoline. It has the highest energy per unit mass of any fuel and can be produced from water using surplus renewable electricity.
• Disadvantages. It is an energy carrier, not a source: energy must be spent to make it; most hydrogen today comes from natural gas, so it is only clean if made by electrolysis with renewable power; very low energy per unit volume makes storage bulky and expensive; liquefaction consumes about a third of the energy content; no distribution infrastructure; fuel cells need costly platinum catalyst.
• Compared with solar energy (asked 2080 Bhadra and 2073 Shrawan). Solar is a primary source that is free but intermittent and needs storage; hydrogen is a storable carrier that can be transported and used on demand, but must first be made using energy. They are complements, not competitors: solar or hydro electricity makes hydrogen, and hydrogen solves the storage problem that solar creates.
• Advantages specifically for Nepal (asked 2079 Bhadra). Nepal has surplus hydro-electricity in the wet season that is currently spilled; electrolysis converts that spill into green hydrogen. Hydrogen can then displace imported LPG and petrol, cutting the trade deficit; it can feed a domestic urea fertiliser plant, another large import; and it can fuel long-range transport where batteries are impractical. Kathmandu University's green hydrogen laboratory has already demonstrated the chain.

Fuel Cells: General, PEM and SOFC

• The one difference from a battery that must be stated. Fuel cells require a continuous supply of fuel and oxygen to sustain the reaction, whereas in a battery the chemicals present react with each other to generate EMF. A fuel cell therefore produces electricity continuously for as long as the inputs are supplied; a battery is exhausted and must be recharged.
• Basics of electrochemistry. A redox reaction split into two half-cells. Oxidation (loss of electrons) occurs at the anode; reduction (gain of electrons) occurs at the cathode; the electrolyte conducts ions but blocks electrons, forcing the electrons through the external circuit where they do work. The potential difference between the two half-reactions is the EMF.

Polymer Electrolyte Membrane (PEM) fuel cell

• Also called the proton exchange membrane fuel cell. Developed for transport applications as well as stationary and portable applications. Distinguishing features: lower temperature and pressure operation and a special polymer electrolyte membrane.
• The three reactions, write all three.

• Main parts to label on the diagram. Fuel (H₂) inlet, anode, catalyst layer, polymer electrolyte membrane, cathode, air (O₂) inlet, gas diffusion layers, bipolar plates, external circuit, and the outlets for excess fuel and for unused air, water and heat.
• How it works in words. Hydrogen enters at the anode, the catalyst splits it into protons and electrons. The membrane passes only protons, so electrons must travel the external circuit, that is the electric current. At the cathode, protons, electrons and oxygen recombine into water, which is the only exhaust.
• Applications. Transportation is primary; distributed or stationary and portable power generation is secondary.

Solid Oxide Fuel Cell (SOFC)

• Definition. An electrochemical conversion device that produces electricity directly from oxidising a fuel. Fuel cells are characterised by their electrolyte material, and the SOFC has a solid oxide or ceramic electrolyte.
• Construction. Made of four layers, three of which are ceramic. A single cell of these four layers is typically a few millimetres thick; hundreds of cells are connected in series to form an SOFC stack.
• Why it runs hot. The ceramics do not become electrically and ionically active until they reach very high temperature, so stacks run at 500 to 1000 °C.
• Working. Reduction of oxygen into oxygen ions occurs at the cathode. These O²⁻ ions diffuse through the solid oxide electrolyte to the anode, where they electrochemically oxidise the fuel. Water is given off as a by-product along with two electrons, which flow through the external circuit doing work before re-entering the cathode.
• Advantages. High efficiency, long-term stability, fuel flexibility (can run on hydrogen, methane, syngas), low emission, relatively low cost.
• Largest disadvantage. The high operating temperature, which gives long start-up times and mechanical and chemical compatibility problems between layers.

• IGFC systems. An integrated gasifier fuel cell plant is analogous to an integrated gasification combined cycle plant, but with the gas turbine power generation unit replaced by a fuel cell power generation unit. Coal or biomass is gasified to syngas, cleaned, then fed to a high-temperature fuel cell, giving higher efficiency than combustion.

Potential, Challenges and Policy for Nepal

• The potential, with numbers.
  • Hydropower: theoretical 83,290 MW, technically feasible 45,610 MW, economically feasible about 42,000 MW.
  • Solar: about 300 sunny days a year, insolation 3.6 to 6.2 kWh/m²/day, commercially viable grid-connected potential of the order of 2,100 MW.
  • Wind: roughly 3,000 MW in identified windy corridors, chiefly Mustang and the Kali Gandaki valley.
  • Biomass and biogas, potential for over a million household biogas plants; biomass still the largest primary energy source in use.
  • Geothermal: around 32 hot springs, low-enthalpy, suited to direct use.
• Challenges to harvesting it. Rugged terrain and difficult transport of equipment; seasonality, hydro output collapses in the dry season while monsoon cloud cuts solar; high upfront capital cost with weak project financing; a weak transmission and distribution grid that cannot absorb or evacuate variable generation; land acquisition and forest clearance; shortage of skilled operation and maintenance manpower; dependence on subsidy; policy and regulatory instability; quality control of imported equipment; and grid integration of variable sources without storage.
• How integration improves energy security and sustainability (asked 2082 Bhadra). A mixed portfolio of hydro, solar, wind and biomass is complementary: solar peaks in the dry season when river flow is lowest, and wind in Mustang blows strongest in the afternoon. That diversity reduces dependence on any single source and on imported fossil fuel, flattens seasonal deficits, cuts import bills and foreign-exchange exposure, and lowers emissions. Adding storage and pumped hydro plus a smart grid turns the mix into firm, dispatchable supply.
• Which technologies suit local-level application, and how to adapt them (asked 2082 Bhadra Q9). Micro and pico hydro for hill villages with perennial streams; solar PV mini-grids and solar home systems where no stream exists; biogas for households with livestock; improved cookstoves and briquette; small solar irrigation pumps in the Terai; solar, wind hybrids in Mustang. Adapt them by designing for local load profiles, using locally manufacturable components such as cross-flow turbines, training local technicians for O&M, and vesting ownership in a community cooperative with a tariff that funds a repair fund. Where the national grid arrives later, design mini-grids to be grid-interconnectable rather than stranded.
• Policy and strategy to recommend. Renewable Energy Subsidy Policy delivered through AEPC; net metering and a clear feed-in tariff or PPA regime from NEA; grid code for variable renewables; concessional finance and a green bond; mandatory solar water heating in building codes; tax rebate on electric vehicles and induction cooking; investment in transmission and pumped storage; cross-border power trade with India and Bangladesh; and local-government-led rural electrification plans.

Emission Hazard

• The nine major pollutants and where they come from.
  • Carbon monoxide, from incomplete combustion of fuels.
  • Sulphur dioxide and nitrogen oxides, from industrial and vehicular exhaust.
  • Chlorofluorocarbons, refrigerant discharge.
  • Mercury: industries, fluorescent lamps and burning of coal.
  • Carbon dioxide, fossil fuel burning; a greenhouse gas.
  • Methane: cow farming, landfill emissions, natural sources; a greenhouse gas.
  • Volatile organic compounds: fuel vapour, solvent, paint.
  • Particulate matter, PM 2.5 and PM 10.
  • Ozone, bad at low altitude and does not survive to replenish the high-altitude ozone layer that protects us from UV.
• Health impacts of common pollutants, pair each pollutant with its effect. Carbon monoxide especially affects persons with heart disease. Unburned hydrocarbons cause serious problems for those with lung disease, asthma or emphysema. Nitrogen oxides are linked to a wide range of respiratory problems: cough, runny nose, sore throat. Ozone causes chest pain, coughing and shortness of breath. Lead exposure leads to decreased intelligence. Particulate matter causes respiratory and cardiovascular disease.
• Automotive pollution splits into three scales.
  • Local: direct exposure to evaporated fuel and tailpipe pollution with direct toxic effect on people: CO, NO_x, ozone, benzene, toluene.
  • Regional: many cars in one region build up pollution until air-chemistry reactions produce new pollutants: smog, haze, ozone, nitric acid.
  • Global: ozone layer depletion and global warming and cooling, from CO₂, CH₄, sulphates and CFCs. To reduce it, make processes more efficient and use less carbon in the fuel.
• Internal combustion engine chemistry. Complete combustion gives HC + (O₂+N₂) → CO₂ + H₂O + unaffected N₂. Incomplete combustion gives unburnt HC + NO_x + CO + SO_x.
• Causes of motor vehicle pollution: five. Improper maintenance (low-quality parts, no preventive maintenance culture, lack of skills and equipment); poor transport infrastructure and road condition; fraud and corruption; driving habits; tampering with emission systems.
• Vehicular emission control strategies, five. Appropriate emission standards for new and in-use vehicles; stringent standards for registration of new vehicles; require use of cleaner fuel; require mandatory periodic inspection; take stringent enforcement action.
• Status of emission hazard in Nepal (asked 2082 Bhadra). Kathmandu ranks among the world's most polluted cities, third on the pollution index list used in the course. Causes: old and poorly maintained diesel vehicles, brick kilns in the valley, road dust and construction, open waste burning, and winter inversion trapping pollution in the bowl-shaped valley. Consequences: high PM 2.5, respiratory illness, school closures. Responses: Euro/Bharat stage norms, the green sticker inspection scheme, ban on very old vehicles, electric public transport, improved brick kiln technology, and air quality monitoring stations.

Battery Hazard

• The four main hazards, the exact slide list. Battery acid; flammable gases; electrical shock; weight.
• Protection: five measures. Goggles; face shield; rubber gloves; rubber apron; recharge in a safe, ventilated location.
• Why each hazard exists. Sulphuric acid causes chemical burns and destroys clothing and eyes. Charging a lead-acid cell releases hydrogen, which is explosive in a confined space. A car battery can deliver hundreds of amps, so a dropped spanner across the terminals gives arcing and burns. A large battery is heavy enough to cause back and crush injury.
• Environmental impact: the part most questions actually want.
  • Toxic heavy metals. Lead, cadmium, mercury and nickel leach from dumped batteries into soil and groundwater, entering the food chain. Lead causes neurological damage and lowers intelligence in children.
  • Acid spillage lowers soil pH and kills soil organisms and vegetation.
  • Informal recycling. Backyard lead smelting releases lead fumes and poisons the workers and neighbourhood, a real problem around Kathmandu.
  • Lithium batteries add fire and explosion risk in waste streams through thermal runaway, plus mining impacts for lithium and cobalt.
  • Volume. The spread of solar home systems, inverters and electric vehicles has multiplied the number of batteries reaching end of life.
• How to manage the issue (asked 2082 Baishakh). Extended producer responsibility, the seller must take the old battery back; deposit-refund schemes; licensed collection and formal recycling with fume control; a ban on open dumping and informal smelting; segregation of batteries from municipal waste; second-life use of retired EV packs as stationary storage; labelling and public awareness; and design for recyclability.

Nuclear Hazard

• Fusion vs fission, define both. Nuclear fusion is a reaction in which atomic nuclei of low atomic number fuse to form a heavier nucleus with release of energy. Nuclear fission is a reaction in which a heavy nucleus splits, spontaneously or on impact with another particle, with release of energy.
• Sources of nuclear radiation: two groups. Natural: cosmic rays from outer space, radioactive materials in soil, rocks, air and water. Anthropogenic: nuclear power plants, nuclear accidents, X-rays, diagnostic kits, test laboratories.
• Physiological effects, graded by dose, the examiner wants the ladder.
  • First sign, decrease in the count of white blood cells.
  • Mild radiation sickness: nausea and vomiting, headache, fatigue, weakness.
  • Moderate: fever, hair loss, vomiting blood, bloody stool, poor wound healing.
  • Severe: diarrhoea, high fever, 50 % fatality.
  • Very severe: dizziness, disorientation, low blood pressure, over 50 % fatality.
• Somatic vs genetic effects (asked 2071 Shrawan). Somatic effects appear in the exposed individual: radiation burns, radiation sickness, cataract, leukaemia and cancer. Genetic effects appear in the descendants because radiation damages DNA in reproductive cells, mutations and birth defects in later generations.
• Short-term vs long-term (asked 2075 Ashwin). Short term: acute radiation syndrome, burns, immediate fatality near the source, evacuation and contamination of food and water. Long term or chronic: genetic mutations, tumours, cancer, birth defects, cataracts, contaminated land uninhabitable for decades, and the unsolved problem of waste.
• Potential hazards of nuclear waste (asked 2080 Baishakh). Waste stays radioactive for thousands of years; heat generation requires cooling for decades; leakage into groundwater; no permanent geological repository is in operation anywhere; transport accidents; and the risk of diversion of fissile material for weapons or a dirty bomb.
• Control of radioactive pollution, the three classical principles plus practice. Distance from the source; time of exposure kept minimum; shielding with lead or concrete. In practice also: use of lab hoods and air filters, eliminating dry sweeping, use of respirators, dosimeter monitoring, and safe waste storage.

Energy Storage: Need, Forms and Characteristics

• Two defining characteristics, know these by name.
  • Energy density: the amount of energy that can be supplied per unit volume or mass, measured in Wh/kg. High energy density means large energy stored in small volume.
  • Discharge time, the period over which the technology releases its stored energy.
• Desirable properties, eight. Portable and mobile; lighter in weight; maintainable; economic; long life; fast recharge; high energy density; less self-discharge.
• Forms of energy storage, group them under six headings.
  • Chemical: hydrogen, bio-fuels, hydrogen peroxide, liquid nitrogen.
  • Biological: starch, glycogen.
  • Electrochemical, batteries and flow batteries.
  • Electrical: capacitor, super-capacitor, superconducting magnetic energy storage (SMES).
  • Thermal: ice storage, solar pond, fireless locomotive, molten salt.
  • Mechanical: flywheel, compressed air energy storage, pumped hydroelectric storage, gravitational potential energy.
• Why storage became the challenge of the 21st century, the answer they want.
  • Renewables are intermittent. Solar stops at night, wind is erratic, and Nepali hydro collapses in the dry season, so generation no longer follows demand.
  • Generation and demand must match instantly on an AC grid, and electricity itself cannot be stored: it must be converted to another form first, and every conversion loses energy.
  • Peak demand is short and sharp. Building generation for a two-hour evening peak is far costlier than storing energy for it.
  • Transport electrification demands very high energy density in small mass, which no chemistry yet delivers at petrol's level.
  • Remaining barriers: cost per kWh, limited cycle life and degradation, safety and thermal runaway, scarce raw materials (lithium, cobalt), recycling and disposal, and slow charging.

Smart Grid

• A smart grid must be: six adjectives, worth easy marks. More reliable, more secure, more economic, more efficient, more environmentally friendly, and safer.
• Four milestones. Consumer enablement; Advanced Distribution Operations (ADO); Advanced Transmission Operations (ATO); Advanced Asset Management (AAM).
• Five principal characteristics. Increase active participation by consumers; increase new products, services and markets; accommodate all generation and storage options; provide power quality for the digital economy; anticipate and respond to system disturbances (self-healing).
• Impact on Nepal's socio-economic development (asked 2080 Baishakh). Cuts technical and non-technical losses, which are a large share of NEA's distribution losses, so more of the generated energy is sold. Enables time-of-day tariffs and demand-side management so the evening peak flattens and new plants are deferred. Allows net metering so rooftop solar owners can sell surplus. Improves reliability for industry and digital services. Detects faults automatically, cutting outage duration in remote hill feeders. Supports cross-border power trade with accurate metering and scheduling, and supports EV charging management.
• Can it be applied in Nepal? (asked 2079 Bhadra). Yes, but in stages: smart meters and AMI first (already rolling out), then SCADA and automated distribution, then demand response and net metering, then full self-healing networks. Constraints are capital cost, telecom coverage in hills, skilled manpower and data security.

Super-Capacitors, and Battery vs Super-Capacitor

• Properties. Stores energy in the electric field between a pair of charged plates; capable of fast charging and discharging; able to go through many cycles without degradation; energy efficiency 85 to 98 %.
• Advantages. Higher power density; ease of maintenance; higher energy efficiency; rapid discharge.
• Disadvantage. Low energy density: it cannot hold much total energy, and voltage falls steadily as it discharges.

• Why super-capacitors are important (asked 2078 Bhadra). They fill the gap between the capacitor and the battery: they absorb and release large power in seconds, so they protect the battery from high-current stress, capture regenerative braking energy in EVs and trams, ride through voltage dips, start engines in cold weather, and last the life of the vehicle without replacement.

Hybrid Vehicles, Electric Vehicles, G2V and V2G

• Advantages of a hybrid. Very low emission; greater range; better acceleration. Add: regenerative braking recovers energy, the engine runs at its efficient point, and no charging infrastructure is needed.
• Working principle. At low speed the electric motor alone drives the wheels; at cruising speed the engine takes over and may also charge the battery; under hard acceleration both deliver torque together; while braking the motor acts as a generator and recovers kinetic energy into the battery; at rest the engine shuts off (start-stop).
• Electric vehicle. An EV uses one or more electric motors or traction motors for propulsion. It may be powered through a collector system by electricity from off-vehicle sources, or be self-contained with a battery, solar panels or a generator.
  • Advantage: no tailpipe emission.
  • Disadvantages: substantial electrical energy cost; high initial cost; batteries are heavy and occupy a lot of room; poor acceleration in the older designs described in the course.
• Fuel cell vehicle. A type of electric vehicle using a fuel cell instead of, or with, a battery to power its onboard motor. Advantage: no vehicle emission. Disadvantage: very expensive.
• Dual fuel engine. Natural gas is burned in a diesel engine by mixing it with the intake air; the injected diesel ignites the natural gas. About 30 to 40 % of the energy comes from diesel and the rest from gas. Advantage: NO_x and particulate matter are reduced. Disadvantage: high cost.
• G2V, grid to vehicle. The normal one-way charging direction: grid AC → on-board or off-board charger → rectified DC → battery. Smart G2V schedules charging to off-peak hours so the evening peak is not worsened.
• V2G, vehicle to grid. The reverse flow: a parked EV's battery discharges back into the grid through a bidirectional charger under aggregator control. Because a car is parked about 95 % of the time, a fleet becomes a large distributed battery that can provide peak shaving, frequency regulation and spinning reserve, and can absorb surplus midday solar. Costs: extra battery cycling and degradation, the need for bidirectional hardware, metering and settlement rules, and owner consent over state of charge.
• Why EVs suit Nepal (asked 2076 Chaitra). Electricity is generated domestically from hydro while all petroleum is imported, so every EV directly cuts the trade deficit and foreign exchange outflow; it removes tailpipe emission from the polluted Kathmandu valley; running cost per kilometre is far lower; and EV charging can absorb surplus wet-season generation that is otherwise spilled. With V2G, the same fleet can then deliver energy back to the grid at the evening peak.

Hydropower Output and Annual Energy, 2082 Bhadra

Watch the wording. The question gives gross head. If it also gives penstock losses, subtract them first and use net head. If it says the plant runs only a certain number of hours per day, use that instead of 24.

Wind Turbine Power Output, 2082 Baishakh

The version worked in the lecture slides uses blade length 52 m, wind speed 12 m/s, density 1.23 kg/m³ and C_P = 0.4, giving A = 8495 m² and P = 3.61 MW. Same method, smaller numbers.

Solar System for a Computer Lab, 2081 Baishakh

Marks come from the method, not the numbers. Write your assumptions at the top, then follow load → array → battery → inverter → controller in that order. Any sensible assumption is accepted.