Energy Flashcards
Sustainable Energy
Sustainable energy can be defined as a form of energy that can be utilized again and again without putting a source in danger of getting depleted, expired, or vanished.
Sustainable energy is power which is able to be replenished within a human lifetime and so cause no long-term damage to the environment.
Solar Energy
Electromagnetic radiation from the sun, result of a thermo nuclear fusion reaction on the surface of the Sun, 92% lies in the range 315nm to 1400nm.
Advantages of Solar Energy
Renewable
eco friendly
available in large quantities
good for remote application
no distribution loss
creates independence
no thermal pollution of waterways
cells last ~ 30 years
no hidden cost.
Disadvantages of Solar Energy
Not available in all areas
economically costly to start maintain and convert solar energy to electrical
PV systems are difficult and time and energy consuming to manufacture.
requires engineering expertise to setup
large patch of panels required to meet our current energy needs
costlier than current non renewable sources
Energy storage challenges, as energy dependent on time of day, weather and place
Flat Plate Collector (Solar Heater)
Works on the black body principal and tendency of a black surface to trap heat is utilized.
Main Parts :
Black Surface : To absorb incident Solar radiation
Glazing Surface : Allows sunlight to pass through, but prevent heat loss through radiation and convection.
Tubes conducting heating fluid to transfer heat from collector.
Insulation on sides and bottom
Support structures
Application of Flat Plate Collectors
Low cost, low maintenance, easy to manufacture, permanently fixed.
Photo Voltic cell
At the core its a semiconductor material, usually silicon, doped with elements, P or B usually, to create two distinct layers, N type having excess electrons, and P type having excess protons, forming a P-N junction. A metallic grid is the electrical contact of the diode and allows light to fall on the semi conductor material, an anti reflective layer between the metallic grid increases amount of light going to semiconductor.
Working of A photo voltaic cell
Light falls on the P-N junction, photons are absorbed and electron hole pairs are formed, electrons are absorbed by n type end and holes by p type end, when these two ends connected by a conducting material current flows.
Current output depends on size, efficiency, intensity of sunlight, cells are connected in series or parallel to increase voltage, current and power levels. Multiple cells mounted and connected forms a module, multiple modules and panels form a photovoltaic array.
Properties of Fuels
High calorific value
Moderate Ignition temperature
Low volatile matter
Adequate viscosity
Low moisture content
Easy and safe to transport
Small to store
Harmless substances on combustion
Air requirement adequate,
Ash content should be absent
Calorific Value
Number of parts of water heated through 1 degree Celsius by complete combustion of unit volume of fuel, under the conditions
1) All heat evolved absorbed by water
2) Products formed leave the system at atmospheric temp and pressure.
Units of calorific value
BTU, KCU, CHU
1 BTU = 0.252KCal
1KCA = 3.968
High(Gross) and low(Net) calorific value
High is when you completely combust a unit volume of fuel and let it cool to 16 centigrade
Low is when you completely combust a unit volume of fuel and allow products to escape.
NCV = HCV - (0.09H%587)
Because 1 part by weight of hydrogen produces 9 parts (1+8) by mass of water.
Dulong Formula
Q = 1/100 [ 8080 x C + 34500 x (H – O/8) + 2240 x S]
Where, Q = Calorific value in KCU/Kg
C = % of carbon
H = % of hydrogen
O = % of oxygen
S = % of Sulphur
Experimentally calorific value of solid and liquid fuel is determined using Bomb Calorimeter. Dulong is theoretical
Hydrocarbons as Fuel
Organic compounds of Hydrogen and carbon, highly energy dense, available in various forms and easy to transport and store as they have high energy density per unit volume.
Impact of Hydrocarbons and fossil fuels.
Running out of it after using it for soo long.
Releases CO2 which is a greenhouse gas, incomplete combustion can release CO and Nitrogen oxides and particulates which further contribute to pollution and pose health hazards.
