Advanced Technology in Electric Power Generation

Solar Energy To Electrical energy

WASIM AL-GHAFIR© 2012

INDEX

•Introduction•Applications•Parameters•Energy Sources in Palestine •References

Solar Energy:• Radiant light and heat from the sun.• It has been harnessed by humans since

ancient times using a range of ever-evolving technologies.

• One of the Solar Energy Technologies is solar photovoltaic

INTRODUCTION(1/4)

INTRODUCTION(2/4)• Solar power is the conversion of

sunlight into electricity, either directly using photovoltaics (PV), or indirectly using concentrated solar power (CSP).

Photovoltaic systems (PV system).Concentrated solar power (also called concentrating solar power, concentrated solar thermal, and CSP

INTRODUCTION(3/4)Photovoltaic systems (PV system)• Photovoltaic systems (PV system): uses

solar panels to convert sunlight into electricity.• A system is made up of : One or more solar photovoltaic (PV) panel. A DC/AC power converter (also known as an

inverter). A racking system that holds the solar panels. Electrical interconnections, and mounting for

other components

Typical Photovoltaic System

INTRODUCTION(4/4)

How Does It Work ?!(1/2)• The solar cell works in three steps:1.Photons in sunlight hit the solar panel and are

absorbed by semiconducting materials, such as silicon.

2.Electrons (negatively charged) are knocked loose from their atoms, causing an electric potential difference. Current starts flowing through the material to cancel the potential and this electricity is captured. Due to the special composition of solar cells, the electrons are only allowed to move in a single direction.(Photovoltaic Effect)

How Does It Work ?!(2/2)3. An array of solar cells converts solar

energy into a usable amount of direct current (DC) electricity.

• The photovoltaic effect is the creation of voltage or electric current in a material upon exposure to light.

• When the sunlight or any other light is incident upon a material surface, the electrons present in the valance band of the metallic atom absorbs energy and, being excited, jump to conduction band and become free.

APPLICATIONS(1/3)•There are many applications on photovoltaic cells, one that my presentation is focused on, is converting the solar energy from the sun to electrical energy by means of Photovoltaic Effect and DC/AC converter.

A solar cell made from a monocrystalline silicon wafer Solar Car- Australia

APPLICATIONS(2/3)

Nellis Solar Power Plant, 14 MW power plant installed 2007 in Nevada, USA

APPLICATIONS(3/3)

Aerial view of one of the SEGS plantsThe largest solar power plant in the world, located in the Mojave Desert of California.

•Capacity :354 MW•Capacity factor:21%

Also Called Concentrating Solar Power, concentrated solar thermal, and CSP) systems use mirrors or lenses to concentrate a large area of sunlight, or solar thermal energy, onto a small area. It is a way to help increase the incident light on the cells .

Concentrated solar power

PARAMETERSMaterials

• Various materials display varying efficiencies and have varying costs. Materials for efficient solar cells must have characteristics matched to the spectrum of available light.

• Some cells are designed to efficiently convert wavelengths of solar light that reach the Earth surface. However, some solar cells are optimized for light absorption beyond Earth's atmosphere as well. Light absorbing materials can often be used in multiple physical configurations to take advantage of different light absorption and charge separation mechanisms.

• Materials presently used for photovoltaic solar cells include monocrystalline silicon, polycrystalline silicon, amorphous silicon, cadmium telluride, and copper indium selenide/sulfide.

Efficiency• The efficiency of a solar cell may be broken down

into reflectance efficiency, thermodynamic efficiency, charge carrier separation efficiency and conductive efficiency. The overall efficiency is the product of each of these individual efficiencies.

• Calvin Fuller and Daryl Chapin created the silicon solar cell in 1954.These early solar cells cost 286 USD/watt and reached efficiencies of 4.5–6%.

• Using amorphous and monocristalline silicon together, EPFL team achieved an astounding 22.4 percent efficiency.

• Researches are in progress to use black silicon to increase the efficiency.

COST(1/2)• The cost of a solar cell is given per unit of peak electrical

power. Solar-specific feed-in tariffs vary worldwide, and even state by state within various countries. Such feed-in tariffs can be highly effective in encouraging the development of solar power projects.

• High-efficiency solar cells are of interest to decrease the cost of solar energy. Many of the costs of a solar power plant are proportional to the panel area or land area of the plant.

• The price of solar panels fell steadily for 40 years, until 2004 when high subsidies in Germany drastically increased demand there and greatly increased the price of purified silicon (which is used in computer chips as well as solar panels).

• January 2008 prices for solar modules in Germany dropped from €3 to €1 per peak watt

COST(2/2)

LIFESPAN/STORAGE• Most commercially available solar panels are capable of

producing electricity for at least twenty years. The typical warranty given by panel manufacturers is over 90% of rated output for the first 10 years, and over 80% for the second 10 years. Panels are expected to function for a period of 30 to 35 years.

• Solar energy is not available at night, making energy storage an important issue in order to provide the continuous availability of energy. Both wind power and solar power are intermittent energy sources, meaning that all available output must be taken when it is available and either stored for when it can be used, or transported, over transmission lines, to where it can be used. Wind power and solar power tend to be somewhat complementary, as there tends to be more wind in the winter and more sun in the summer, but on days with no sun and no wind the difference needs to be made up in some manner.

STORAGE• Solar energy can be stored at high temperatures using

molten salts. Salts are an effective storage medium because they are low-cost, have a high specific heat capacity and can deliver heat at temperatures compatible with conventional power systems. The Solar Two used this method of energy storage, allowing it to store 1.44 TJ in its 68 m³ storage tank, enough to provide full output for close to 39 hours, with an efficiency of about 99%.

• Off-grid PV systems have traditionally used rechargeable batteries to store excess electricity. With grid-tied systems, excess electricity can be sent to the transmission grid.

• As we all know that the sun is moving the sky and the incident will not be the same if the sun is perpendicular to the cells or if it has a different angle. So to solve this problem, scientists created “focal tracker”, which allow the photovoltaic panel to rotate and find best angle to give us the highest exposure of the light.

PRESENT ISSUES

• Advantages:• Renewable /Clean/totally silent • provide cost effective solutions to energy

problems in places where there is no mains electricity.

• they require little maintenance and have a long lifetime.

• they don't need large scale installations.• No green gases.

ADVANTAGES/ DISADVANTAGES

• The main disadvantage of solar energy is the initial cost.

• Most types of solar cell require large areas of land to achieve average efficiency.

• low efficiency 22% : Air pollution and weather can also have a large effect on the efficiency of the cells.

• Solar panels are bulky: his is particularly true of the higher-efficiency, traditional silicon crystalline wafer solar modules. These are the large solar panels that are covered in glass.

DISADVANTAGES

ENERGY SOURCES IN PALESTINE

• More than 90% percent of our power needs, are relying on foreign sources.

• There are no known fossil fuel reserves• In general Palestine is counted as one of the poorest countries in the Middle East in Terms of energy sources

• 10% of the power is from Indigenous energy resources, which is limited to solar energy for photovoltaic and thermal applications(mainly for water heating), and biomass(wood and agricultural waste)for cooking and heating in rural areas.•The Potential of wind energy is relatively small but not yet utilized

• In my city GAZA:• Electricity generators with a capacity of 140MW at the

first phase. Following extensive damage from an “Israeli” bombing raid in July 2006, now after more than 6 years this station is only producing 50MW-100MW, taking in considering growth of population which should be 320MW. Also nowadays we buy 22MW from Egypt and 125MW from “Israel”, which sums to 98 MW shortage, only 10 hours per day electricity !!

• The main source of fuel for this station was supposed to be natural gas, but due to political obstacles which caused the halting of the project got production of natural gas from The Mediterranean sea, the station uses diesel for energy, which

ENERGY IN MY CITY

• A chemistry teacher has developed a PV panel on his house roof that generates all of the electricity for his 3-store house and for some of the street lights.

• ‘A Solar Water & Power Source for Recovery of Gaza’ Concept developed by TREC and presented to Forum2000 in Prague, 9/10 October 2005. Not approval because of ‘political reasons !’.

• A solar-powered heart unit for the hospital in GAZA, which was constructed by ITALY. (destroyed after only 2 months of its work) I guess they did not consider that the panel should withstand bombing the roof of a hospital!

EXAMPLES

THANK YOU FOR YOUR ATTENTION

Questions & Answers

• http://en.wikipedia.org/wiki/Solar_energy• http://en.wikipedia.org/wiki/Solar_cell• http://www.eurekalert.org/pub_releases/2012-09/epfd-

ner092712.php• http://www.chm.bris.ac.uk/webprojects2003/ledlie/

advantages_of_solar_energy.htm• Renewable Energy in the Middle East: A Review of

Modern Technologies

REFERENCES