j. non-conventional energy sources - lecture

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J. NON-CONVENTIONAL ENERGY SOURCES - LECTURE

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1. Non-conventional Energy SourcesNon-conventional Energy Sources also referred to as renewable energy sources, these are actually energy flow

which are replenished as they are used, hence, the use of the term renewable. These are characterized by a

maximum theoretical rate at which energy may be extracted in a renewable mode, that is, the rate at which new

energy is arriving or flowing into the reservoirs associated with many of the renewable energy flows. All forms o

energy sources with the exception of geothermal energy, salinity gradient and tidal energy are indirecmanifestations of solar energy.

2. Solar EnergyThere are many applications for the direct use of solar thermal energy, space heating and cooling, water heating,

crop drying and solar cooking.

Solar Constant = 1353 W/m2

Useful energy from the sun is between 10 AM 2 PM = 1000 W/m2

3. Solar Radiation Phenomenaa. Atmospheric scattering by air molecules, water vapor, dust.b. Atmospheric absorption by O3 (ozone), H2O, CO2.

4. Forms of Solar Radiationa. Beam or direct radiation without having beam scattered by the atmosphere.b. Diffuse radiation direction is changed by scattering.c. Total or global solar radiation the sum of beam and diffuse radiation.

5. PyranometerPyranometer is the instrument used to measure the total solar radiation.

6. Photovoltaic CellPhotovoltaic cell is a device which converts solar energy to electrical energy.

7. Solar CollectorsSolar Collectors whose ideal characteristics are high absorptivity and low emissivity.

7.1Flat Plate Collectors (FPC)a. Area absorbing solar radiation is the same as the area intercepting solar radiation.b. Uses both beam and diffuse radiation.c. Does not require orientation.d. Little maintenance.e. Working fluid is either air or water.f. Measure of performance is by means of collection efficiency.

Collection efficiency = useful gain / incident solar radiation.

7.2Focusing or concentrating collectorsa. Utilize optical systems, either reflectors or refractors.b. Uses beam radiation only.c. Needs tracking.

1. Total or full-tracking.2. Fixed-reflector, tracking-receiver.3. Fixed-reflector, tracking-reflector.


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d. Measure of performance is by means of concentration ratio.Concentration ratio = aperture area / receiver area

e. Classifications1. Plane receiver, plane reflectors2. Parabolic concentrators.3.

Fresnel reflectors or refractors4. Array or heliostat (reflectors)

f. Concentrator types.The purpose of concentrator is to increase the flux of radiation n receiver.

1. Cylindrical: focus on a line.2. Circular: photovoltaic cell.

8. Conversion and Applications of Solar Energy8.1Solar water heating systems (swsh).

a. Flat plate collector, storage tank, auxiliary heating equipment.b. Classifications:

1. Natural circulation system tank is located above collector, no circulation at night, auxiliary equipmentmay be needed.

2. Forced circulation system requires a pump to circulate water, tank may not be located above collector,employs check valve whose purpose is to prevent reverse circulation of water and to prevent nighttime

thermal losses from the collector.

8.2Solar space heating.a. Ho t air systemsb. Hot water systems

8.3Solar space cooling.a. Continuous

1. Closeda. Absorption systemb. Solar vapor-compression system.e.g. lithium bromide (LiBr) water.

2. Open

a. Liquid desiccant

b. Solid desiccant

b. Intermittent

1. Liquid absorbent

2. Solid absorbent

8.4 Solar power conversion

a. Photovoltaic (PV) devices or solar cells

1. Single crystal silicon most widely-used and technically-developed.

2. Cadmium-sulfide (CdS).

3. Gallium arsenide

4. Thermoelectric and thermionic

b. Solar thermal electric power (STEP).


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9. Wind PowerWinds are a result of air motion caused by uneven heating of the earths surface by the sun and rotation of the

earth.

10.Typical uses of wind power.a. To drive water pumps.b.

To drive rice and corn mills.c. To charge batteries.

d. To generate power.11.Types of windmills.

a. Turbine typeb. Rotor typec. Propeller typed. Dutch sail typee. Panemone type

12.Types of wind energy collectorsa. Horizontal-axis rotors axis of rotation is parallel to the direction of the wind; can be either lift or drag-type

yaw-active, meaning it changes position depending on wind direction.

b. Vertical-axis rotors do not have to be turned into the wind as wind stream direction changes, design is simplet.1. Savonius rotors employ S-shaped blades and are primarily drag devices.2. Darrieus rotors

c. Cross-wind horizontal-axis rotors13.Conversion and Applications of Wind Energy

a. Water pumping which could be used directly for irrigation.b. Used to compress air for use in a variety of applications including operating electricity during peak demand

periods of a public utility system.

c. Used in centralized utility applications to drive synchronous AC electrical generators.d. Used for direct heat applications.e. Used in the production of hydrogen by electrolysis of seawater (in the case of off-shore winds).

14.Wind Energy Storage Systemsa. Batteries in the form of chemical energy.b. Pumped-hydro storage energy.c. Compressed air storage systems.d. Hydrogen gas produced from pyrolysis of water.e. Thermal energy storage systems.f. Flywheel

15.Site selectionWind power is proportional to the cube of the wind velocity.

Factors to be considered

a. Windshear.b. Turbulence, or rapid change in speed and/or direction.c. Acceleration or retardation.


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16.Wind Power PerformanceBetzs law is a theory about the maximum possible energy to be derived from a wind turbine. The ideal o

maximum theoretical efficiency, also called power coefficient, of a wind turbine is the ratio of maximum power from

the wind to the total power available in the wind. The factor 0.593 is known as Betzs coefficient. It is the maximum

fraction of the power in a wind stream that can be extracted.

Total power available from the wind

3

2

1AVP

total=

Maximum available power from the windmill

cAVP

3

2

1=max

where:

= wind density

A = swept area =2

4D

V = wind velocityD = blade diameter

17.Bio-Energy or Bio-massBiogas is a good fuel. Have you thought how this is formed? Biomass like animal excreta, vegetable wastes and

weeds undergo decomposition in the absence of oxygen in a biogas plant and form a mixture of gases. This mixture

is the biogas. Its main constituent is methane. This is used as a fuel for cooking and Lighting.

18.Aerobic and anaerobic bio-conversion processa. Bioproducts: Converting biomass into chemicals for making products that typically are made from petroleum.b. Biofuels: Converting biomass into liquid fuels for transportation.c. Biopower: Burning biomass directly, or converting it into a gaseous fuel or oil, to generate electricity.

19.Bio-mass sourcea. Manureb. Crop residuesc. Fuel woodd. Sugar cropse. Urban refuse: paper, yard and food wastesf. Municipal sewage-sewage sludge: 0.02 0.03% solids, above 99% waterg. Aquatic plants: water hyacinthh. Energy farming: denthrothermal or energy crops

1. Fast-growing trees: ipil-ipil2. Sugar and starch crops: cassava in ethanol production3. Oil and hydrocarbon crops: coconut oil4. Herbaceous crops


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20.Bio-mass Conversion Processesa. Biochemical: introduction of microorganisms

1. Ethanol fermentation2. Anaerobic digestion

b. Thermochemical1. Pyrolysis an irreversible chemical change caused by the action of heat in the absence of oxygen.2. Combustion/gasificiation

Gasification is the conversion of a solid fuel to a combustible gas as a means of thermochemical reaction

Complete combustion takes place with excess oxygen or at least 100% theoretical oxygen, wherea

gasification takes pace with an oxygen deficit.

21.Advantagesa. Inexpensiveb. Low sulfur contentc. Reduces environmental hazardd. Convertible to gaseous/liquid fuelse. Less CO2 build-upf. Generates additional employmentg. Simple to store

22.Disadvantagesa. Low thermal content, only about 20 MJ/kgb. High moisture content, approximately 50%c. Low bulk densityd. Transpo uneconomicale. Rarely homogeneousf. Low concentration

23.Tidal PowerTidal power is basically hydro-electric power utilizing the difference in elevation between high and low tide to

produce energy. A basin is required to catch the sea water during high tide while the water drives the turbine.

In the Philippines, commercialization is not full-scale since it is found that the average difference is only about 6

meters.

24.Ocean Thermal Energy Conversion (OTEC)This is otherwise known as low thermal head plant, it utilizes the temperature difference between the ocean surface

water and the water at the sea bottom. Surface water which is at relatively high temperature is pumped to an

evaporator where the water evaporates into saturated steam. This steam drives a single stage turbine thereby

producing electricity, and exhaust to a jet condenser maintained at the saturation pressure of the subsurface wate

temperature pumped from the sea bottom.


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In the Philippines, full-scale commercialization is also not economically-viable because of the small temperature

difference out waters have.

25.Magneto Hydrodynamic PlantMagneto hydrodynamic generator where combustion gases produced in a combustion chamber at high pressure

and temperature and seeded with metal vapor to increase its electrical conductivity, is passed through an expansion

tube lined with a strong magnetic field. This induces an electric voltage in the gas conductor and effect the flow o

electrons through the electrodes along the magnetic field, thereby generating electricity.

26.Thermionic ConverterThermionic converter is a device which converts heat energy directly to electrical energy. All metals and some

oxides have free electrons which are released on heating. These electrons can travel through a space and collecte

on a cooled metal. These electrons can return to hot metal through an external load thereby producing electrica

power.

27.Fuel CellFuel cell is a device which converts chemical energy to electrical energy. Fuel cells produce electricity from a

electrochemical reaction between hydrogen and oxygen. Fuel cells are efficient, environmentally benign and reliable

for power production. The use of fuel cells has been demonstrated for stationary/portable power generation and

other applications.

- End -

j. non-conventional energy sources - lecture

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