Gandhinagar Institute Of Technology

Topic : Solar EnergyGuided By :

Branch : Batch :

MR. NIRAV SIR

Active Learning Assignment

Electrical

Physics (2110011)

F1

Name ENROLLMENT NO. Abhishek Chokshi 140120109005 Raj Shah Adnan Vohra

PREPARED BY:-

140120109054140120109063

Energy produced by the sun

Clean, renewable source of energy

Harnessed by solar collection methods such as solar cells

Converted into usable energy such as electricity

Photovoltaic (solar) panel

Set of solar panelsSun and electrical power lines

What is Solar Energy?

How much solar energy?

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

Solar Cooking

Eliminates work◦ No daily search for

firewood 2 Billion people rely on

wood for cooking fuel!◦ No risks to women

and children◦ Frees time for other

activities◦ No need to stir food◦ Helps to liberate

women

More Benefits of Solar Cooking

Cooks foods slowly and thoroughly

Preserves nutrients Foods will not burn Pots are easy to

clean; less clean water is needed

Use for canning vegetables

Use for dried fruit Kill insects in dry

grains

Solar Thermal

Water heating and cooking

Systems can be passive or active

Passive systems only found in warmer climates, as they are prone to freezing

Active: Roof-top collectors heat glycol which then passes through a heat exchanger in the storage tank to heat water

Electric pump can be run on solar PV

Solar Thermal Energy

Cooking Water Heating

Solar Thermal Energy

Using the sun to heat water

The simplest solar technology

Solar water heating (also called solar thermal energy) is the simplest of the technologies.

This includes heating water for use in our homes for cooking, bathing and cleaning, or for heating swimming pool water, or even providing space heating in winter. These systems have been refined and improved and widely used over the years to the point where they pay for themselves in energy savings while making people’s lives more comfortable and lowering their energy bills.

There are many commercial as well as residential uses of solar water heating.

The rooftop solar collectors on this office building provide hot water. Solar water heating is one of the oldest and most reliable renewable energy technologies.

Solar Electric (Photovoltaic)

Silicon-based solar cell

Dye-sensitized solar cell

Photovoltaic Solar Cells Generate electricity

directly from sunlight 2 Main types:

◦ Single-crystal silicon (traditional) Widespread Expensive to manufacture

◦ Dye-sensitized (“nano”) Newer, less proven Inexpensive to

manufacture Flexible

Solar Cells are Converters of Energy…

Solar cells are devices that take light energy as input and convert it into electrical energyLight energy

Solar cell - converts light energy to electricity

Electrical energy (carried through wires)

…But Not All Energy is Converted• Like chloroplasts in plants, solar cells can only

absorb specific wavelengths of light.• In both, light that isn’t absorbed is either

transmitted through or reflected back.• Whether a certain wavelength of lights gets

absorbed depends on its energy.

Chlorophyll molecules absorb blue and red light, but reflect green light

Absorption of Light by Atoms

Single electron transition in an isolated atom

• Absorption occurs only when the energy of the light equals the energy of transition of an electron

Light

Electrons can jump between “bands”

Incident light with energy ≥ than the “band gap” energy can be used to excite the electrons

Absorption of Light by Ionic Compounds

Photovoltaic Cells

Photovoltaic (PV) systems convert light energy directly into electricity.

Commonly known as “solar cells.” The simplest systems power the

small calculators we use every day. More complicated systems will provide a large portion of the electricity in the near future.

PV represents one of the most promising means of maintaining our energy intensive standard of living while not contributing to global warming and pollution.

Solar Electric Systems

How Does it Work? Sunlight is composed of photons, or bundles of

radiant energy. When photons strike a PV cell, they may be reflected or absorbed (transmitted through the cell). Only the absorbed photons generate electricity. When the photons are absorbed, the energy of the photons is transferred to electrons in the atoms of the solar cell.

How Does it Work?

How Does it Work?• Solar cells are usually made of two thin pieces of

silicon, the substance that makes up sand and the second most common substance on earth.

• One piece of silicon has a small amount of boron added to it, which gives it a tendency to attract electrons. It is called the p-layer because of its positive tendency.

• The other piece of silicon has a small amount of phosphorous added to it, giving it an excess of free electrons. This is called the n-layer because it has a tendency to give up negatively charged electrons.

Large companies like Google, Walmart, and Microsoft use solar energy to partially power some of their facilities

Solar panels on Microsoft building Solar panels being tested on Walmart store

Solar Panel Use Today

Solar Concentrators These 20-kW Solar

Systems dishes dwarf visitors in Alice Springs, Australia.

The concentrators use an array of mirrors to focus sunlight onto high-efficiency solar cells.

Four supports hold the cells in front of the mirrors

The supports also supply cooling water and electrical connections

Solar-Thermal Electricity:Power Towers General idea is to collect the light from many reflectors

spread over a large area at one central point to achieve high temperature.

Example is the 10-MW solar power plant in Barstow, CA. 1900 heliostats, each 20 ft by 20 ft a central 295 ft tower

An energy storage system allows it to generate 7 MW of electric power without sunlight.

Capital cost is greater than coal fired power plant, despite the no cost for fuel, ash disposal, and stack emissions.

Capital costs are expected to decline as more and more power towers are built with greater technological advances.

One way to reduce cost is to use the waste steam from the turbine for space heating or other industrial processes.

Power Towers

Power tower in Barstow, California.

Solar-Thermal Electricity:Parabolic Dishes and Troughs Focus sunlight on a smaller receiver for each device;

the heated liquid drives a steam engine to generate electricity.

The first of these Solar Electric Generating Stations (SEGS) was installed in CA by an Israeli company, Luz International.

Output was 13.8 MW; cost was $6,000/peak kW and overall efficiency was 25%.

Through federal and state tax credits, Luz was able to build more SEGS, and improved reduced costs to $3,000/peak kW and the cost of electricity from 25 cents to 8 cents per kWh, barely more than the cost of nuclear or coal-fired facilities.

The more recent facilities converted a remarkable 22% of sunlight into electricity.

Parabolic Dishes and Troughs

Because they work best under direct sunlight, parabolic dishes and troughs must be steered throughout the day in the direction of the sun.

Collectors in southern CA.

Direct Conversion into Electricity

Photovoltaic cells are capable of directly converting sunlight into electricity.

A simple wafer of silicon with wires attached to the layers. Current is produced based on types of silicon (n- and p-types) used for the layers. Each cell=0.5 volts.

Battery needed as storage No moving partsdo no wear

out, but because they are exposed to the weather, their lifespan is about 20 years.

Efficiency is far lass than the 77% of solar spectrum with usable wavelengths.

43% of photon energy is used to warm the crystal. Efficiency drops as temperature increases (from 24%

at 0°C to 14% at 100°C.) Light is reflected off the front face and internal

electrical resistance are other factors. Overall, the efficiency is about 10-14%.

Cost of electricity from coal-burning plants is anywhere b/w 8-20 cents/kWh, while photovoltaic power generation is anywhere b/w $0.50-1/kWh.

Does not reflect the true costs of burning coal and its emissions to the nonpolluting method of the latter.

Underlying problem is weighing efficiency against cost.◦ Crystalline silicon-more efficient, more expensive

to manufacture◦ Amorphous silicon-half as efficient, less expensive

to produce.

Efficiency and Disadvantages

Thank You