Renewable Sources Of Energy

Dr. Vivek Kumar

Renewable Energy Sources

SolarWindHydropowerBiomassGeothermal

Solar Power

How Much Solar Energy

The surface receives about 47% of the total solar energy that reaches the Earth. Only this amount is usable.

Types of Solar Power

Active Passive

Active Solar Power

Energy from sun is stored in a “thermal mass”

When needed, heat from thermal mass is then pumped throughout structure

Active Solar Power

This also refers to electrical generation using solar power

Two ways to do this are photovoltaic cells and huge commercial electric facilities

This shows the diagram for the house seen in the previous slide. The PV panels are on the roof

Large-scale Solar Electric Site

Large-scale Solar Electric Site

These facilities use solar power to heat water to form steam. The steam goes to generate electricity just as in fossil fuel or nuclear electric plants.

No release of air pollutantsNo electricity generated at nightThey do work on cloudy days, though.

Passive Solar Power

Works on the principle that hot air rises and cool air sinks (convection)

Solar heats air and it moves through convection through the structure or to thermal mass

Passive Solar Power

Mass wall or “Trombe Wall

Using back wall as “mass”

To rest of house

Solar Power

Benefits– Abundant

– No greenhouse gases, few other pollutants

– Simple, minimal repair needed

– Cheap over the long term

Detriments– Retrofitting needed if

structure is not already designed as passive solar

– Has limitations, night, some locations better such as south rather than north facing slopes

– Initial capital outlay can be high

Wind Power

Wind Power

• Wind power is the conversion of wind of wind energy into a useful form of energy.

• Most modern electrical wind power is generated by converting the rotation of turbine blades into electrical currents by means of an electrical generator.

• Wind power is also used to propel ships using sails.

• Windmills provide mechanical power, and were originally developed for milling grain for food production.

Wind power

Can be used for mechanical tasks, e.g. pumping water

Areas where winds are stronger and more constant, such as offshore and high altitude sites, are preferred locations for wind farms.

Electrical Power Windmills

High speed, low torque machines

Will turn themselves off if wind speed exceeds their limits.

Used for generation of electricity for direct use or storage in batteries

Effects of windpower

No greenhouse gasesFew other pollutantsCheapAbundantSimple

Some noise pollutionMetal blades interfere

with TV & radio reception

Aesthetic pollutionNo evidence for bird

death, but can kill bats

Positive Negative

Where is wind power available?

Wind power not highly suited to these areas

Hydro Power

Hydropower

Electric Mechanical

How hydropower works

• The power of flowing water has been used for hundreds of years to operate machinery. This power can also be used to generate electricity.

• Large scale hydroelectric schemes involve building a dam across the end of a river valley to create a reservoir.

• This is done high up in a mountainous area.

• Once they are built, hydroelectric schemes provide a cheap and reliable source of electricity.

Hydro Power

Negative effects of Hydropower

Flooding the land

Displacement of local inhabitants

Local climatic changes

Tectonic activities (Earthquakes)

Loss of species (aquatic & terrestrial)

Loss of normal nutrient flow down river

Changes temperature of water, too

Positive Effects of Hydropower

Can generate electricityCan do mechanical work, e.g. grind grainNo greenhouse gasesInitial construction provides jobs

.

Biomass Energy

What Is Biomass Energy

• Biomass energy is the use of living and recently dead biological material as an energy source.

• Ultimately dependent on the capture of solar energy and conversion to a chemical (carbohydrate) fuel.

• Theoretically it is a carbon neutral and renewable source of energy.

How It Works

•Traditional: forest management, using wood as fuel•Use of biodegradable waste

Examples: manure, crop residue, sewage, municipal solid waste

•Recent interest in agricultural production of energy crops

Should be high yield and low maintenanceExamples: corn, sugarcane, switchgrass, hemp, willow, palm oil, rapeseed, and many othersDoes not have to be a food cropRecent interest in bioengineered (GM) plants as fuel sources

Production of a liquid or gaseous biofuelBiogas due to the breakdown of biomass in the absence of O2

Biomass Energy

Advantages• Versatile• Renewable• No net CO2 emissions

(ideally)• Emits less SO2 and NOx than

fossil fuels

Biomass Energy

Disadvantages• Low energy density/yield

In some cases (eg, corn-derived bioethanol) may yield no net energy

• Land conversionBiodiversity lossPossible decrease in agricultural food productivity

• Usual problems associated with intensive agricultureNutrient pollutionSoil depletionSoil erosionOther water pollution problems

Biomass Pros & Cons

Burning biomass gets rid of solid waste

Creates energyCreates new markets

for crops

Burning biomass releases CO2 and other gases associated with combustion

Creates solid waste from ash

May cause more grasslands to be planted to corn

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Geothermal Energy

Geothermal Energy

How It Works

– Geothermal power plants• Use earth’s heat to power steam turbines

– Geothermal direct use• Use hot springs (etc) as heat source

– Geothermal heat pumps

Advantages

• Renewable• Easy to exploit in some cases• CO2 production less than

with fossil fuels• High net energy yield

Disadvantages

DisadvantagesNot available everywhereH2S pollutionProduces some water pollution (somewhat similar to mining

Conclusions

Major difficulties in attaining target of 10% of electricity generated by renewables by 2010

Main contributors to this target will be :-

1)Offshore and Onshore windfarms/clusters

2)Biomass/wood, straw, etc

3)Photovoltaic

But policies like Climate Change Levy and the Renewables Obligation will help establish renewables.