PHOTOVOLTAIC SOLAR ENERGY
Director: Ivan Arturo Ramírez S. TEMI-2
CDTI-SENA (VALLEY) 2008
What is energy?
Energy is a property of a body or material system under which it can transform, changing their status or position, and act on them causing other processes of transformation. The energy can have different origins and, depending on them is called one way or another:
1.Energía
kinetic Associate the motion of bodies
2.Energy
potential: Associated with the position within a force field. 3.Energía
light: Associated with solar radiation.
nuclear 4.Energía: Associated with the process of fusion (joining of nuclei) or fission (broken kernels) that occur within atoms.
• Energy has three basic properties:
1. The total energy of an isolated system conserva.Por both the Universe can not be created or loss of energy.
2. Energy can be transmitted (transferred) of bodies, systems or materials to others. 3. The energy can be transformed from one form to another.
• The Sun is a giant nuclear reactor. It is indeed a huge gaseous sphere (with a mass 330,000 times that of Earth), consists mainly of helium, hydrogen and carbon, within which there are continuing nuclear fusion reactions in the process releasing a great amount energy.
The energy emitted by the Sun reaches Earth not evenly.
Varies by time of day, depending on the seasonal inclination of the globe relative to the sun, according to different areas of the land area, etc., due to movements of the Earth.
It has been estimated that the energy per unit time that an area receives from the Sun located at sea level is about 1,353 watts per square meter.
• Thus, the absorption of solar energy by plants, the photosynthetic process, resulting in biomass. Wind power, tidal power, etc., Also have their origin in the effects of solar radiation on Earth.
• An energy from a free source (solar radiation) and inexhaustible human scale (is estimated that the Sun is about 6,000 million years of existence and that it will continue for as many millions of years).
UNIT
• For the electricity is used as a production unit kilowatt-hour (kWh), defined as work performed for an hour by a machine that has a power of 1 kW . 1 kW • h = 36 ° 105 J
PHOTOVOLTAIC POWER
• Photovoltaic solar energy comes from the interaction of photons from solar radiation with semiconductor elements that make up the solar panels. • The tension generated by the solar panels is continuous (such as batteries).
PHOTOVOLTAIC PANEL
• It is responsible for converting the sun's energy into electrical energy, their output voltages typically range between 12-24-48 volts. This is usually the highest cost elements of the installation. His life approx. ranges from 20-25 years. It requires minimal maintenance.
SOLAR CELLS
solar cells based on the photovoltaic effect in which light incident on a two-layer semiconductor device produces a difference of photo voltage or potential between the layers. This voltage is capable of driving a current through an external circuit so as to produce useful work.
• Photovoltaic cells are mainly composed of semiconductor materials silicon and germanium. • The most commonly used material is silicon, and within this there are three types of panels, "Monocrystalline: 12% efficiency.
-Polycrystalline
: efficiency somewhat lower (8-10%).
-Amorphous: efficiency between 5-7%.
The photovoltaic panels are divided into:
• Monocrystalline: made up of sections a single crystal silicon (recognizable by their round or hexagonal). Its efficiency in converting sunlight into electricity is more than 12%.
• Polycrystalline : when small particles are formed by crystallized. Its efficiency in converting sunlight into electricity is slightly lower than in monocrystalline silicon.
• Amorphous silicon when it has not been crystallized. Its efficiency in converting sunlight to electricity varies between 5% and 7%.
• Their effectiveness is greater the larger the crystals, but also its weight, thickness and cost. The first performance can reach 20% while the latter can not reach 1%, however its cost and weight is much lower.
Manufacture of photovoltaic modules
• The photovoltaic module is composed of individual cells connected in series. This type of connection allows you to add tension.
• The voltage of each cell (about 0.5 volts). Usually consist of modules are produced 30, 32, 33 and 36 cells in series, according to the required application.
• the module is claimed to stiffness in its structure, electrical insulation and resistance to weather.
• The series connected cells are encased in a resilient plastic (Etilvinilacelato) who also does the role of an electrical insulator.
• A tempered glass with low iron content in the side facing the sun and a multilayer plastic sheet (polyester) in the back.
• The module has a mold made of aluminum or polyurethane and junction boxes which house the positive and negative terminals of the series of cells.
• For terminal boxes connect the cables connecting the module to the system.
manufacturing process steps
module
• Essay Electrical and classification of cells
• Electrical interconnection
cell
• Putting It All Together. Placement cell layers of plastic welded casing and glass and plastic sheets
• Lamination Module. The set is processed in a semi-automatic high vacuum, by a process of heating and mechanical pressure, forming the laminate.
• Curagem. The laminate is processed in a temperature controlled oven in which polymerization is complete plastic wrap and reaches perfect adhesion of the different components. The whole after curagem, is a single plate. • moldings. Placed first elastic sealant around the perimeter of the laminate and then the aluminum forming the molding. Pneumatic machines are used to achieve the proper pressure. Polyurethane moldings are placed by means of injection molding machines.
• Placement of terminals, terminals, diodes and junction boxes.
• final test.
test the modules on the modules should be measured and observed: • Electrical
operational
• Electrical insulation (to 3000 Volts DC)
• Physical, finish defects, etc.
• Impact resistance.
• Tensile strength of the connections.
• Resistance to salt spray and humidity.
• Behaviour at high temperatures for prolonged periods (100 degrees Celsius for 20 days).
• Stability to thermal shock (-40 º C to +90 º C) in successive cycles.
How do solar cells?
• Solar cells consist of two types of material, usually silicon n-type p-type silicon The light of certain wavelengths can ionize atoms in the silicon and the internal field produced by the union that separates some of the positive charges ("holes") of the negative charges
• The holes move toward the positive layer or p-type layer to the negative electrons or n-type layer Although these opposite charges attract each other, most of them can only be re combine passing through an external circuit outside the material because of the internal potential energy barrier. s (electrons) within the photovoltaic device.
• The current is relatively stable at high temperatures, but the voltage is reduced, leading to a loss of power due to increased the temperature of the cell.
• A typical single crystal silicon solar cell of 100 cm2 will produce about 1.5 watts of power at 0.5 volts DC and 3 amps under sunlight in summer.
Main applications:
• Electrification of rural properties: light, TV, radio, communications, water pumps
• Electrification of fences
• Lighting • Signage
• Cathodic protection
System Components:
12V DC Current:
• Panels module
photovoltaic panels • Mounts
• battery charge regulator and battery bank current
110/220V AC:
• In addition to the above, between the batteries and consumption will need to install an inverter with adequate power. The inverter converts direct current (DC) batteries into alternating current (AC). Most appliances use alternating current.
INVERTER DC / AC
Effect of environmental factors on the output characteristic of the device.
Effect of solar radiation
• The result of a change in the intensity of radiation is a variation in output current for any voltage value.
• The current radiation varies in direct proportion. The tension is almost constant. Effect of temperature
• The main effect caused by the increase in temperature of the module is a reduction of tension in direct proportion.
• That's why for more very high ambient temperatures are suitable modules having greater number of cells in series so that they have enough output voltage to charge batteries. Maximum output power during the day
• The module IV characteristic varies with environmental conditions (radiation, temperature). This means that there will be a family of IV curves which will show the output characteristics of the module during the day at a time of year.
• The maximum power curve of a module based on the time of day is as shown in this diagram load:
• is measured in watt hours per day.
INTERACTION WITH A RESISTIVE LOAD
• the operating point of the module will be the intersection of the curve with a line graph the expression I = V / R, where R is the load resistance connected. Interaction with a battery
• A battery has a voltage dependent charge status, age, temperature, rate of loading and unloading, etc. This tension is imposed on all elements that are attached to it, including the PV module.
• Is the battery that determines the operating point of the module. The battery voltage varies its amplitude between 12 and 14 volts.
• Since the output of the photovoltaic module is influenced by variations in radiation and temperature during the day, this will result in a variable current entering the battery.
Interaction with a DC motor
• A DC motor also has an IV curve. The intersection of it with the IV curve of the module determines the operating point.
• When a motor is attached directly to a PV system without battery or intermediaries controls, reduce the components involved and therefore increases reliability. But do not take advantage the energy generated in the early morning and evening.
Directly attached to a load.
• It is the simplest of all.
The photovoltaic generator is attached directly to the load, usually a DC motor. It is primarily used in water pumps. For lack of storage batteries and electronic components improves system reliability, but it is difficult to maintain an efficient performance throughout the day.
System-accumulator battery module
• You can use a photovoltaic module to replace just the self-discharge of a battery is used for starting an engine, for example. For that you can use modules of amorphous or microcrystalline silicon.
photovoltaic systems, battery and controller
is the configuration used with modules of 33 or 36 cells in which the photovoltaic generator is attached to a battery through a regulator so that it is not overload. Storage batteries fed DC loads.
Battery Charge Regulators
•
regulator constantly monitors battery voltage batteries. When referred voltage reaches a value for which it is considered that the battery is charged (about 14.1 volts for lead acid battery 12 volt nominal) regulator interrupts the charging process.
• This can be achieved by opening the circuit between the photovoltaic modules and battery (serial-type control) or by shorting the PV modules (control shunt). When the consumer makes the battery starts to download and therefore lower your blood, the controller reconnects the generator to the battery and restart the cycle.
Accumulators
• Function priority of batteries in a photovoltaic generation system is to accumulate the energy produced during the hours of light in order to be used at night or during periods of bad weather.
• Another important function of the batteries is to provide a current greater than that which the photovoltaic device can deliver. This is the case of an engine in the boot time may require a current of 4 to 6 times its rated current for a few seconds. Interaction
photovoltaic modules and batteries
• Normally the bank of storage batteries and photovoltaic modules work together to power the loads.
data necessary to size a system
• Rated voltage system. It refers to the typical operating voltage loads connected.
• Required power load for each load power demands is an essential fact.
• Hours of use of the load along with the power required by the load, shall specify the hours of use of that power. Multiplying power for hours of use, you will get the watt hours required by the load at the end of a day.
• Geographical location
system (latitude, longitude and height above sea level of the installation site) These data are needed to determine the proper angle for the PV module and the level of radiation (monthly average) of the place.
• Autonomy planned This is the number of days that is expected to decline or no generation, and that should be taken into account in the design of the storage batteries. • For domestic rural systems are taken from 3 to 5 days and remote communication systems 7 to 10 days autonomy.
calculation to determine the watt-hours per day (Wh / day)
1) Identify each dc load, its consumption in watts and the number of hours per day that should work.
2) Multiply (A) The time of using the equipment (B) consumption of it to get the watt hours per day of consumption of each unit (column [AxB]).
3) Add the watt-hours per day for each appliance to get the watt hours per day total current loads (Subtotal 1).
4) Proceed similarly with AC loads with an increase of 15% additional power to take into account the performance of the inverter (Subtotal 2). To choose the right investor, it should be clear what the voltage levels to be managed both in flasks and AC DC.
5) to obtain the total energy demand. Subtotal 1 + Subtotal 2.
installation and maintenance
Location and orientation of the modules
For proper installation is important to select the best possible location for photovoltaic modules. The location must meet two conditions:
• Be as close as possible to the batteries (to minimize the section of cable).
• Have optimal conditions for the receipt of solar radiation.
• The modules should be well away from anything that casts a shadow over them in the best period of radiation (usually from 9 to 17 hours) on the shortest day of the year.
• To increase the use of solar radiation, the modules should be tilted in relation to the horizontal plane at an angle that will vary with the latitude of the installation. BP Solar recommends the adoption of the following angles.
• Batteries must be installed in a compartment separate from the rest of the room and with adequate ventilation, because of lead-acid batteries release explosive gases.
• In rural facilities is advisable to have a switchboard with an entry for the battery bank and one or two outputs (with their respective safeguards) will be distributed consumption rooms. In that box may also be a indicator of battery charge.
Maintenance
photovoltaic module
One of the great advantages production of photovoltaic systems is that they need maintenance. That is why they are the ideal sites that need operational autonomy.
• The front of the modules consists of a tempered glass with 3 to 3.5 mm thick, which makes them resistant to hail.
• They are self-cleaning due to the inclination itself must have the form, so that dirt can drain.
• However, in places where possible, be convenient to clean the front of the modules with water mixed with detergent.
• You should periodically verify the angle of inclination corresponding to that specified.
• You must confirm there is no projection of shadows of nearby objects in any sector of the modules between 9 and 17 hours, at the least.
• You should periodically verify if the electrical connections are tight and not corroded.
Batteries • Watch the water level periodically in each of the compartments of all batteries. If the level is low, complete with demineralized water.
• Inspect the terminals in order to verify is properly adjusted and free of corrosion.
• See if there sulfation, as this could indicate gas in the battery and therefore a control system failure.
CALCULATION OF ENERGY DELIVERED in watt-hours (Wh) FOR PHOTOVOLTAIC CADAPANEL
• To determine the energy (E) that can deliver each photovoltaic panel Watt-hour, we must consider the following:
-latitude of the place (L).
-power panels (P) that we will use in watts (w).
-Finally, the following equation: E =
(5-L/15) * (1 + L/100) * P
- Hence, continuing with our example
obtain the following information:
Sevilla-Latitude 37.4 degrees.
-power panels using 50 watts peak (Wp).
E = (5-37,4 / 15) * (1 +37.4 / 100) * 50 E = 172.4 Wh
In the example of the weather in Seville, these are
favorable so we assume that increases by 20%, which would
as follows:
20% = 34.48 Wh Wh 172.4 172.4
Wh = Wh + 34.48 Wh 206.88> 206.9 Wh.
a result of this calculation, since we know the number of panels needed for our facility, taking into account the following expression:
Number of panels = Daily consumption / energy provided by panel
Number of panels = 1500 Wh / 206.9 Wh
Number of panels = 7.3 (8 panels of 50 Wp)
ESTIMATED COST OF THE INSTALLATION
• More or less we can estimate that the price of peak watt of installed power is about to be 12 euros, which is why from our facility we can calculate:
8 Panels * 50 Wp = 400 Wp * 12 euros / Wp = 4800 euros.
