pv solar into

Photovoltaics and Solar Energy

• Analogy to Photosynthesis:

  • Solar energy collection is similar to how a tree performs photosynthesis.

  • Solar panels have cells that individually do work, connected like leaves on a tree.

  • Leaves capture sunlight, similar to cells in solar panels.

  • Leaves connect to twigs, twigs to branches, and branches to the tree, mirroring the cell to the solar site architecture.

Conductors - Copper and Aluminum

• Electron Movement:

  • Copper is used due to its easily released electron, facilitating current flow.

  • Copper and aluminum:

    • are good conductors

    • are easily obtainable from the earth's crust

    • are workable, machinable, and moldable.

• Aluminum vs. Copper:

  • Aluminum needs 60% more material than copper for the same conductivity.

  • Aluminum is cheaper and lighter than copper.

Semiconductors

• Use in Electronics:

  • Semiconductors are used in cell phones, computers, iPads, and most electronic devices.

• Definition:

  • Semiconductors are materials that have some conductivity and some insulation properties.

  • Conductivity can be controlled during manufacturing for specific jobs.

• Basic Structure:

  • Semiconductors have two sides: one with excess electrons and one with a lack of electrons.

• Diode Effect:

  • Electrons can only move in one direction due to the diode effect.

  • A basic diode utilizes a semiconductor with one side having many electrons and the other side, none.

  • Electrons flow to the side lacking electrons, then through a conductor to do work in a circuit.

Electricity Generation in Solar Cells

• Cell Structure:

  • Cells are connected with junctions between silicon layers.

• Function:

  • Solar cells generate electricity when exposed to sunlight.

Panel Design Considerations

• Anti-Reflective Coating:

  • Glass on bifacial panels still needs an anti-reflective coating to allow light to pass through to the silicon cells.

• Magnifying Glass Concept:

  • Intensifying sunlight generates heat, reducing efficiency.

  • Materials that can handle more heat would be more costly.

Materials

• Silicon:

  • Silicon cells are efficient and long-lasting but expensive.

• Cadmium Telluride (CdTe):

  • CdTe is used in thin-film solar cells.

  • CdTe cells appear dark and uniform in color.

  • small scale applications: calculators, solar-powered watches, camping phone chargers

  • flexible and can be used on curved surfaces such as camper roofs

• Emerging Technologies:

  • ABX3 is very efficient but degrades quickly in sunlight.

Panel Degradation

• Material Breakdown:

  • Semiconductor materials degrade over time, reducing their ability to generate voltage.

• UV Light Impact:

  • Ultraviolet (UV) light breaks down materials.

  • UV coatings are used but have limited lifespan.

Environmental Factors

• Altitude:

  • Altitude affects air mass, which changes solar panel performance.

How Solar Panels Are Made

• Material:

  • Solar panels use silicon, derived from sand (superabundant material).

  • Silicon needs to be purified to 99.999% purity.

• Silicon Structure:

  • Atoms are bound together, restricting electron movement unless enough energy strikes.

• Semiconductor Function:

  • Sunlight causes random particle movement without a driving force for current.

• Boron Infusion:

  • Boron is added to create holes for electrons to move towards.

  • This makes some electrons migrate to the positively charged region, creating an electric field.

• Electric Field Formation:

  • An electric field forms between charges, moving electrons in a particular direction.

• Panel Construction:

  • Top layer is thin and electron-rich.

  • The bottom layer is thicker.

Manufacturing Process

• Layer Assembly:

  • Solar panels use cells connected in series with copper strips.

  • EVA (ethylene vinyl acetate) sheets protect cells from environmental factors like dirt, humidity, vibrations, and shocks.

• Silicone Purification:

  • Sand mixed with carbon is heated to 2,000 degrees Celsius to obtain gaseous silicon compound.

  • The gaseous compound is mixed with hydrogen to get highly purified polycrystalline silicon.

• Wafer Creation:

  • Silicon ingots are shaped into thin slices called wafers, which are the core of the photovoltaic cell.

• Panel Types:

  • Thin film

  • Crystalline silicon panels: common; black or blue rectangular grids with smaller square cells.

    • Monocrystalline: High electrical conductivity, uniform blue color, no grain marks, costly, highest efficiency, best purity.

    • Polycrystalline: More impurities, cheaper.

Thermal Solar (Concentrated Solar Power)

• Mirror Array:

  • Mirrors on a two-axis tracking system focus sunlight on a central tower.

  • The concentrated heat melts salt.

  • Molten salt heats water to generate steam, which spins a turbine to produce electricity.

• Location:

  • Google Maps: Vegas (southwest).

• Cost:

  • Thermal solar is costly to operate and maintain.

Parabolic Thermal Solar

• Design:

  • Parabolic mirrors focus sunlight on a black pipe filled with oil.

  • The heated oil transfers heat to water, generating steam.

• Genesis Site:

  • Located west of Blythe in Desert Center.

Solar Cell Manufacturing Steps

• Anti-Reflective Coating:

  • Applied to reduce sunlight reflection.

• Metal Conductors:

  • Added to each surface of the wafers.

  • This creates a grid-like matrix for energy conversion.

• Phosphorus Diffusion:

  • A thin layer of phosphorus is diffused over the wafer surface, giving it a negative electrical orientation.

• Solar Glass Application:

  • Tempered glass coated with ethylene vinyl acetate (EVA) is applied to protect cells from external elements.

• Quality Control:

  • Thorough visual inspection: Checks for faults or errors to ensure quality, especially important given automation.

• Cell Interconnection:

  • Taping and Connection: Solar cells are joined into a matrix alignment by taping.

  • Connections are soldered, excess material is removed to minimize area.

• Module Insulation:

  • Insulation: Connections are insulated using VAC sheets and EVA encapsulation.

  • The module is checked for dust, color mismatch, and other issues.

  • EL Testing: Electroluminescence testing is performed to check for defects.

• Finishing Steps:

  • Back Sheet Trimming: Excess material is cut and discarded.

  • Frame Cutting: Frames of various sizes are cut to border the panels.

  • Holes are made for mounting and grounding the panel.

  • Sealer Application: Sealant is applied to help the module firmly attach to the frame.

  • Junction Box Installation: The junction box is firmly attached.

  • Connections are soldered and left to cure for 10-12 hours to ensure dryness.

• Final Testing:

  • The panel is wiped clean and tested for output current, voltage, etc.

  • An information label with all details is pasted on.

  • A quality control lab tests insulation resistance.

  • A mechanical load test is performed.

Benefits of Solar Panels

• Environmentally Friendly:

  • Solar panels address climate change and global warming.

• Cost Savings:

  • After initial investment, solar panels run maintenance-free for many years and save on energy bills.

Recycling

• Process:

  • Starts with pure sand being purified and melted into silicon ingots.

  • Ingots are sliced into wafers, doped with special materials, and connected via copper traces.

  • The assembly is sandwiched between protective layers, sealed, and framed, with positive and negative leads attached.

Solar Panel Types

• Monocrystalline:

  • Most efficient (22.5% efficiency).

  • Most costly to make.

  • Longest lifespan.

  • Space-efficient, generating more watts per square meter.

• Polycrystalline:

  • Look blue and sparkly.

  • Cost-effective to make.

  • Less efficient (14-16% efficiency).

  • Perform better in low light conditions and at higher incident angles.

  • Suitable for fixed sites and residential use.

• Thin Film:

  • Uniform black appearance.

  • Efficiency: 7-18%.

  • Easy to manufacture.

  • Difficult to dispose of; requires hazardous waste management due to the chemicals they are made of.

Bifacial Panels

• Efficiency:

  • Higher efficiency due to collecting sunlight from both sides.

  • Transparent substrate allows sunlight to pass through and be collected off reflections.

• Material:

  • Usually monocrystalline.

• Performance:

  • Work best with reflective surfaces like grass or snow.

• Applications:

  • Common at newer sites due to larger output in a smaller area.

Bypass Diodes

• Purpose:

  • Allow current to flow around broken or shaded panels.

  • Act as a check valve, opening when resistance builds up due to a fault.

• Connection and Function:

  • Panels are connected in series to increase voltage.

  • If one cell is shaded, the photovoltaic effect stops, and electrons back up, opening the circuit.

  • The bypass diode activates, allowing current to flow past the shaded cell.

  • Modules in a panel may be wired in series, with multiple modules in parallel.

Module Configurations

• Series:

  • Voltage increases.

• Parallel:

  • Current increases.

  • Bussed together.

Solar Panel Construction

• Components:

  • Cell, module, panel, string, with protective layers and a frame.

  • Seals and aluminum frames are important.

• Issues:

  • Aluminum frames can cause ground faults if moisture gets in.

  • Microfractures in the glass can lead to ground faults due to dew.

• Voltage:

  • The cell produces about half a volt.

  • String: 20-40 panels in series, increasing voltage.

• Maintenance:

  • It is self regulating current because it can't produce more current than rated for.

  • Connections and Ground Faults are top issues.

Series vs. Parallel Wiring

• Series:

  • Panels are wired in series to increase voltage.

• Parallel:

  • Parallel to increase current output.

Scale of Solar Sites

• One cell > module > panel > string > combiner box > inverter.

• Several sites:

  • Millions of panels and billions of cells generate gigawatts.

• High Efficiency Production:

  • Inverters turn DC to AC.

  • Inverters feed a medium-voltage transformer that feeds a feeder breaker at the substation.

Important Reminder

• High Voltage Reminder:

  • Wear appropriate PPE when doing experiments in the shop due to live voltage.
    *Panels have voltage even at night.

Panel Replacement

• Always use the same ratings when replacing a panel.

Tracking Systems

• Benefits:

  • Tracking systems keep optimal sunlight, increasing power output.

  • Components: Table, torque tube, actuator, and support post.

• Three-Phase Tracking System:

  • Uses a large three-phase motor to turn a drive via a quarter gear attached to the torque tube.

  • Several strings are connected to one drive, tracking together.

• DC Tracking Systems:

  • Actuated by a DC motor.

  • Independent, off-grid, powered by a battery and small pony panel.

• Solar Sites:

  • Worm Drive Actuator with Square Torque Tube.

  • Linear Actuator: Uses a DC motor to extend the actuator.

  • Pneumatic Site: Tracked by airbags that is very troublesome.

• Two-Axis System: Less space efficient but tracks in two axes.

Common Output Problems

• Problems with Solar Sites
  *High Wind
  *Broken Batteries due to weather

Factors Affecting Site Output

• Heat:

  • Solar panels warm up and become less efficient during the day.

  • Wind can help cool panels.

• Reflection:

  • Shiny glass surfaces are inherently reflective but have an anti-reflective coating.

• Physical Damage:

  • Hail, dirt, dust, debris, humidity and moisture reduce output.

• Soiling

• Physical damage like hail

Solar Panel Degradation

• Technology Improvements:

  • Power generation technologies are advancing.

• Rated Lifespan:

  • Manufacturers guarantee at least 80% output for 10-20 years.

• Maintenance.

  • Infrared and thermography scanning to catch problems.

Sunlight to End User Losses

• Losses to consider: *Location - Needs a good sunny area *Shading and Soiling - causes less output *Temperature - Hotter means less output *The Module will degrade over time

  • Losses at the inverter are the big loss.

The Power Curve (IV Curve)

• Engineers are concerned with all aspects of power.

• You will have a multi-meter and amp clamp.
  *Understanding what is going on behind is cool