Solar Power

What is solar power?

Solar power uses Photovoltaic technology.

Photovoltaic technology converts sunlight into electricity

It is emerging as a major power source due to its numerous environmental and economic benefits and proven reliability.

Benefits of solar power?

Environmental Benefits: As PV generates electricity from light, PV produces no air pollution or

hazardous waste.

Economic and Social Benefits: ➢ Sunlight is free and abundant. ➢ Photovoltaic systems allows us to generate electricity and store it for use when needed. ➢ It creates jobs and strengthens the economy. ➢ It frees us from uncertainties and foreign oil dependence.

This energy source is free, clean and highly reliable.

Photovoltaic (PV) systems

PHOTOVOLTAIC SYSTEM

A complete system includes different components

that should be selected taking into consideration

your individual needs, site location, climate and

expectations.

TYPES OF SYSTEM

Stand Alone – Off grid Modules, charge controller, batteries, and may or may not have an inverter which converts DC power to A/c power

Grid Tie – Grid connected Modules, and inverter connected to the power grid

Hybrid – Grid connected with batteries Modules, grid-tie inverter, and batteries for storage when the

grid is unavailable

Stand Alone – Off Grid Systems

Stand-alone PV systems are designed to operate independent of the electric utility grid, and are generally designed and sized to supply certain DC and/or AC electrical loads.

For systems with no battery the energy is used immediately; only works when it's sunny

Grid Tie – Grid Connected Systems

Grid Tie System is the simplest and most cost effective way to connect PV modules to regular utility power. Grid-Connected systems can supply solar power to your home and use utility power as a backup.

Hybrid– Grid Connected with Batteries

If utility power is reliable and well maintained in your area, and energy storage is not a priority, you don't necessarily need a battery. But if the utility power goes down, even if there is solar, the PV system will be off for the safety of the utility workers. .

MAJOR SYSTEM COMPONENTS

PV Modules or Panels or Array

Charge controller

Battery charger

Inverter

Load

Available Cell Technologies

Single-crystal or Mono-crystalline Silicon

Polycrystalline or Multi-crystalline Silicon Thin film

Ex. Amorphous silicon or Cadmium Telluride

Monocrystalline Silicon Modules

Most efficient commercially available module (11% - 14%) Most expensive to produce Circular (square-round) cell creates wasted space on module

Polycrystalline Silicon Modules

Less expensive to make than single crystalline modules Cells slightly less efficient than a single crystalline (10% - 12%)Square shape cells fit into module efficiently using the entire space

Amorphous Thin Film

Most inexpensive technology to produce Metal grid replaced with transparent oxidesEfficiency = 6 – 8 %Can be deposited on flexible substrates Less susceptible to shading problems Better performance in low light conditions that with crystalline modules

PV CELLS

PV CELLS

❑ The layers have been doped with boron on one side and phosphorous on the other side, producing surplus of electrons on one side and a deficit of electrons on the other side. When the wafer is bombarded by sunlight, photons in the sunlight knock off some of excess electrons, this makes a voltage difference between the two sides as the excess electrons try to move to the deficit side. In silicon this voltage is .5 volt

PV CELLS

Metallic contacts are made to both sides of the semiconductor. With an external circuit attached to the contacts, the electrons can get back to where they came from and a current flows through the circuit. This PV cell has no storage capacity, it simply acts as an electron pump. The amount of current is determined by the number of electrons that the solar photons knock off.

LIMITATION WITH SINGLE PV CELL

Solar cell has a limitation that it can not produce much electricity.

In order to generate useful power, it is necessary to connect a number of cells together in series or in parallel.

INTERNAL CONNECTION OF PV CELLS

PV MODULE

A PV module consists of many PV cells wired in parallel to increase current and in series to produce a higher voltage. 36 cell modules are the industry standard for large power production.

PV PANELS

PV panels include one or more PV modules assembled as a pre-wired, field-installable unit.

PV ARRAY

A PV Array consists of a number of individual PV modules or panels that have been wired together in a series and/or parallel to deliver the voltage and amperage a particular system requires. An array can be as small as a single pair of modules, or large enough to cover acres.

DESIGN OF PV ARRAY

SOLAR PANEL DIMENSIONS

HOW TO WIRE A SOLAR PANEL

There are three types of wiring configurations to Solar Panel: 

Series wiring 

Parallel wiring

And a combination of the two known simply as series/parallel wiring.

SERIES WIRING

To wire any device in series you must connect the positive terminal of one device to the negative terminal of the next device

  Voltage in a series circuit is additive

Current stays the same. 

SERIES CONNECTION

12volts 350 AH

PARALLEL WIRING

To wire any device in parallel you must connect the positive terminal of the first device to the positive terminal of the next device and negative terminal of the first device to the negative terminal of the next device.Voltage in a parallel circuit stays the same. Current is additive.

PARALLEL CONNECTION

Series/Parallel Circuits

A Series/parallel circuit is simply two or more series circuits that are wired together in parallel.

SERIES /PARALLEL CONNECTION

SOLAR CHARGE CONTROLLER

  The most basic function of a controller is to prevent battery over charching.

If batteries are allowed to routinely overcharge, their life expectancy will be dramatically reduced.

  A controller will sense the battery voltage, and reduce or stop the charging current when the voltage gets high enough

SOLAR CHARGE CONTROLLER

BATTERY CHARGER

Batteries accumulate excess energy created by your PV system and store it to be used at night or when there is no other energy input.

The battery's capacity for holding energy is rated in amp-hours: 1 amp delivered for 1 hour = 1-amp hour

TYPES OF BATTERY

➢Lead Acid Batteries

➢Deep-Cycle battery

➢VRLA battery (valve-regulated lead–acid

battery)

➢ Absorbed glass mat (AGM) battery

➢ Gel battery

INVERTER

The batteries in your PV systems store direct current (DC) power which can be used for certain applications but most of the conventional household appliances use alternative current (AC) power. The Inverter converts low voltage DC into higher voltage AC.

INVERTER SIZING

The input rating of the inverter should never be lower than the total watt of appliances.

The inverter must have the same nominal voltage as your battery.

The inverter size should be 25-30% bigger than total Watts of appliances.

INVERTER SIZING

In case of appliance type is motor or compressor then inverter size should be minimum 3 times the capacity of those appliances and must be added to the inverter capacity to handle surge current during starting.

TYPES OF INVERTERS

• Square Wave Inverters

• Modified Sine Wave Inverters

• True Sine Wave Inverters

Solar Inverters

• Grid tie inverters

INVERTER

INVERTER

LOAD

Load – is electrical appliances that connected to solar PV system such as lights, radio, TV, computer,refrigerator, etc.

How does solar power work?

How does solar power work?

PV Module or Array convert the sunlight into

electricity.

PV modules generate DC electricity.

Controller regulate the DC power.

Battery stores the DC signal.

The inverter transforms DC power into AC

electricity.

Solar system (PV) calculation anddesign

Each panel is rated by its DC output power. Currently the best commercial solar panel

(PV) efficiency is around 17.4%.

Solar panels are normally 12V DC output. In large solar panel 24V or 48V DC output also seen.

SOLAR PV SYSTEM SIZING

To figure out what size solar panel, batteries, charge controller and inverter you need, follow the simple steps below.

1. Determine power consumption demands Determine the Watts required by each of the

appliances

➢ Let's assume you have a 100 watt device that you want to power with free solar energy.

SOLAR PV SYSTEM SIZING

2. Calculate total Watt-hours per day for each appliance used

➢ Estimate the hours per day that each appliance will be used.

Let's assume that you want to power for 10 hours

each night. 100 Watts x 10 hours = 1,000 Watt hours. That is the total energy you will need.

ENERGY LOST IN THE SYSTEM

Wiring and connection losses about 10%

Losses in the battery about 20%

Total losses around 30% so the panel will need to produce enough Wh/day for the load plus enough to cover the losses. So it will have to produce about 130% of the energy required by the load

To calculate the Wh/d needed from the panel, multiply the load Wh/d times 1.3

SOLAR PV SYSTEM SIZING

Multiply the total appliances Watt-hours per day times 1.3 (the energy lost in the system) to get the total Watt-hours per day which must be provided by the panels.

Total load= 1,000 Watt hours*1.3 =1300Watt hours So the 1300Watt-hours per day which must be

provided by the panels.

HOW TO CALCULATE THE SIZE OF SOLAR PANELS

2. Now calculate what size solar panel you will need. Based

on a ten hour day of light, the calculation is simple:

If Sunlight is for 10 hrs in a day

1,300 Watt hours / 10 hours sunlight = 130 Watt solar panel.

HOW TO CALCULATE THE SIZE OF BATTERY

3. Calculate what size batteries you need. 1,300 Watt hours divided by 12 Volts =108 Amp Hours of reserve battery power.

1,000 / 12 = 108

An average marine deep cycle battery will work well here. Select a larger size battery to be sure, say 120 Amp hours capacity.

HOW TO CALCULATE THE SIZE OF CHARGE CONTROLLER

4. To figure what size solar charge controller is

needed, take your solar panel wattage, which is 130 watts divided by 12 Volts. 130 / 12 = 10.8 Amps.

Always go larger, in this case use a 12 Amp solar charge controller.

HOW TO CALCULATE THE SIZE OF INVERTER

5. Calculate what size inverter is needed. That's the easy part. You need to power a 130 Watt load, so select an inverter that has at least 130 Watts continuous power rating.

Best Place For Solar Panels?

South Facing roof, adequate spaceNo shading (time of year, future tree growth)Roof structure, condition

DISADVANTAGES OF SOLAR PANEL

Less efficient and costly equipment.Reliability depends upon location. Environment Impact on PV cells.Part Time

Bibliography

http://www.solarhome.org/infowhatissolarpower.htmlhttp://www.wisegeek.org/what-is-solar-power.htm#http://www.scientificamerican.com/article.cfm?id=how-does-solar-power-workhttp://www.solartechnologies.com/cm/About-Solar-Power/how-does-solar-power-work.htmlhttp://science.howstuffworks.com/environmental/energy/solar-cell.htmhttp://cleantechnica.com/2011/10/07/how-does-solar-energy-work-how-solar-power-works/http://www.ehow.com/facts_7298775_do-need-solar-energy_.htmlhttp://ezinearticles.com/?Why-Should-We-Use-Solar-Energy?&id=1911019http://www.motherearthnews.com/Renewable-Energy/Solar-Power-Potential.aspshttp://www.nationalatlas.gov/articles/people/a_energy.html