Renewable Energy

What is RE• Renewable energy is energy obtained

from the continuing or repetitive current of energy occurring in the natural environment such as solar energy. The energy is passing through the environment as a flow, irrespective of these being a man made device to intercept and harness this power.

What is None-RE

• None renewable (finite) energy is energy obtained from static store of energy that remains bound unless released by human interaction such as fossil fuel. External action is required to initiate the supply of energy for practical purpose.

environment

Finite source of energy potential

Device

UseF

E

DDevice

UseF

E

D

environment

A

B

C

Environment

Current Source of continuous energy flow

Figure (1) Contrast between renewable and finite energy supplies, environment energy

flow ABC, harnessed energy flow DEF.

Energy sources

• Renewable energy is derived from the following sources:

• The Sun• The motion and gravitational potential of the sun, moon

and earth.• Geothermal energy from cooling, chemical reaction, and

radiation decay in the earth.• While the finite energy is derived from • The sun• Nuclear reaction on the earth• Chemical reaction from mineral sources.

Sensible energy (Solar radiation, heating device, ocean thermal energy 80 000)

Latent heat energy (Hydro power 40 000)

Kinetic energy (Wind and wave energy 300)

Photosynthesis (Biofule 30)

Solar radiation

Reflected to the space 50 000

From Sun

From earth

Heat (Geothermal 30)

Absorbed on earth 120 000

Orbital motion

Tides (Tides power 3)

Geothermal

From plantary motion

Figure (2) Natural energy currents on earth

Table (1) : Regions that related the opportunity of RE

Regions Poor opportunity of Vast opportunity of Sample of countries

Flat regions hydro power plant wind power Denmark

High mountain region wind power hydro potential Norway

Tropical rain forest

Solar energy sources

biomass energy sources Malaysia

Deserts biomass energy solar energy sources Middle east

RE Chart

Energy planning• Complete energy system must be analyzed, and supply must not be

separated from end-use. Energy supply must be match with the precise needs. In steam power plant, utilizing the emission heat from the boiler as a source of energy to generate warm water is a precise needs. However generating hot water form direct fossil fuel combustion is not a precise need. A variation of this principle is a combined heat and electricity production.

• System efficiency calculation can be most revealing and can be principle unnecessary losses. Efficiency can be defined as a desire output from a process to the total energy input to that process. By improving the equipment cost as an input, total efficiency can be increased. The quality of the equipment can reduce the fuel consumption rate and ultimately improve the efficiency

• Energy management is a very significant factor as it improves the overall efficiency and reduces the economic losses. Renewable supplies are always more expensive in practical than might be assumed.

Energy currents

It is significant that sufficient renewable current is already

present in the local environment. For example, producing

methane form animals dung is considered as a byproduct of an

animal industry but not vice versa. The practical implication of

this principle is that the local environment has to be monitored

and analyzed over a long period to establish what energy flows

are present. In figure 1, the direct current ABC must be

assessed before the diverted flow through DEF is established.

Dynamics Characteristics

The need of energy always varies with time. For example electricity demand on a power network often peak in the morning and evening, and reach a minimum through the night. If the power provided came from finite sources, the input can be adjusted with the demand, so there is no wasted energy but remains with the source fuel. However, with renewable energy system, not only dose end-use vary uncontrollably with time but so too does the natural supply in the environment. The device must be matched dynamically at both D and E as illustrated in figure 1.

Quality of supply

We can define quality as the proportion of an energy source that can be converted to mechanical work. For instance, the power generated from electrical motor has high quality as the mechanical efficiency is about 95%. However the quality of thermal power from burning fuel in a conventional power station is relatively low.

Renewable energy supply systems can be divided into three divisions by quality:

• Mechanical supplier, such as hydro, wind, wave, and tidal power. In general the quality of the supply is high and mechanical work is usually extracted for electricity at quite high efficiency. The proportions are commonly, wind 30%, 60% hydro, wave 75% and tidal 75%.

• Heat supplies, such as biomass combustion, and solar collector. In practical maximum mechanical power production in a dynamic process is about half that predicted by the second law. For thermal boiler heat engine, maximum quality is about 35%, also the thermal efficiency of an IC engine is in the ranges of 30-40%.

• Photon processes, such as photosynthesis and photochemistry. A solar photons of a single frequency may be transferred into mechanical work with high efficiency using matched solar cell.

Dispread versus centralized energy

One of the main differences between renewable energy and infinite energy supply is the energy flux density at initial transformation. Renewable energy commonly arrive at about 1 kW/m2 (e.g. solar beam irradiation, energy in the wind at 10 m/s), whereas finite centralized sources have energy flux densities that are orders of magnitude greater. For example boiler in gas furnace easily transfers 100 kW/m2 and in nuclear reactor the first wall heat exchange must transmit several MW/m2. Finite energy is most easily harnessed centrally and is expensive to distribute, while renewable energy is most easily harnessed in dispersed location and is expensive to concentrate.

Complex systems

Renewable energy supplies are linked to the natural environment which is not the preserve of any one academic discipline such as electrical engineering. An outstanding example is the energy planning of integrated farming as in the Philippine islands .animal and plant wastes may be used to generate methane, liquid and solid fuels ,and the whole system integrated with fertilizer production and nutrient cycling for optimum agricultural yields.