Solar basics

Solar is power that is being harnessed by the rays of the sun. The solar technologies that are used are categorized in two different ways:^[1]

Type 1: Photovoltaic technology- which employs cell arrays to convert sunlight to electricity

Type 2: Thermal technology- which uses sunlight to heat up water, even air, for the use inside^[2]

This project will be using photovoltaic technology or solar panels^[3] so we will expand on this concept. This technology requires a number of other tools^[4]to ensure that the electricity is captured efficiently for many years to come. With the proper care of a solar panel system, the lifespan can be up to 25-30 years^[5]. PV (photovoltaic) technologies should be considered an investment that will pay off eventually over many years, and the type of solar panels widely rely on the individual's needs. The excerpt below helps determine what we should expect in our project based on our location:

"As a general rule for the Pacific Northwest, every 1,000 watts of PV modules requires 100 square feet of collector area for modules using crystalline silicon (currently the most common PV cell type). Each 1,000 watts of PV modules can generate about 1,000 kilowatt-hours (kWh) per year in locations west of the Cascades and about 1,250 kWh per year east of the Cascades. When using less efficient modules, such as amorphous silicon or other thin-film types, the area will need to be approximately doubled. If your location limits the physical size of your system, you may want to install a system that uses more-efficient PV modules. Keep in mind that access space around the modules can add up to 20 percent to the required area.^[6]"

The information provided by Washington State University explores our averages for cloudy Pacific Northwest conditions, and exploration into budget can allow a closer determination into how efficient our annual electricity collection can be.

Types of Solar Panels

The explanation below of the basic types of panels are accredited to Vince Lombardi in Solar Power 101^[7] (p. 11-12). His interpretation was too good to change!

"Monocrystalline solar panels: The most efficient (15 – 20%) and expensive solar panels are made with Monocrystalline cells. These solar cells use very pure silicon and involve a complicated crystal growth process. Long silicon rods are produced which are cut into slices of .2 to .4 mm thick discs or wafers which are then processed into individual cells that are wired together in the solar panel.

Polycrystalline solar panels: Often called Multi-crystalline, solar panels made with Polycrystalline cells are a little less expensive & slightly less efficient than Monocrystalline cells because the cells are not grown in single crystals but in a large block of many crystals. This is what gives them that striking shattered glass appearance. Like Monocrystalline cells, they are also then sliced into wafers to produce 12 the individual cells that make up the solar panel.

Amorphous solar panels: These are not really crystals, but a thin layer of silicon deposited on a base material such as metal or glass to create the solar panel. These Amorphous solar panels are much cheaper, but their energy efficiency is also much less so more square footage is required to produce the same amount of power as the Monocrystalline or Polycrystalline type of solar panel. Amorphous solar panels can even be made into long sheets of roofing material to cover large areas of a south facing roof surface.^[7]"

Tools needed for solar installation:^[9]

1. Hammer Drill: Used for drilling pilot holes for lag screws, drilling holes for mounting the inverter and for driving self tapping screws.
2. Impact Driver: Used for driving lag screws into the rafters, bolting the rails to the L-feet and clamping the modules to the rails.
3. Reciprocating Saw (Sawzall): Used for cutting EMT pipe.
4. Deburring Tool: Used for softening the edges of the EMT cut pipe.
5. Circular Saw with Miter Box: Used for cutting rail.

Safety tips for tools:^[10]

Hammer Drill:

1. Always leave unlocked when not in use
2. Use two hands
3. Never touch hot bit after use with bare hands (wear gloves)
4. Tie back long hair, no dangling jewelry & tuck in loose clothing
5. Wear safety googles when close to where drilling
6. Hearing Protection

Impact Driver:

1. Tie back long hair, no dangling jewelry & tuck in loose clothing
2. Use two hands when possiible
3. Always leave locked when not in use

Reciprocating Saw (Sawzall):

1. Safety glasses here are very important, glasses/sunglasses are not adequate
2. Hearing Protection
3. Gloves
4. Use two hands
5. Always use lock-switch after using

Circular Saw with Miter Box:

1. Safety glasses here are very important, glasses/sunglasses are not adequate
2. Hearing Protection
3. Make sure the saw is securely fastened to the box
4. Hold rail with your left hand
5. The blade must be spinning at full speed before cutting

Power inverter basics

To convert solar energy into electrical energy a power inverter is required to change the power output from the photovoltaic array into conventional electrical power as supplied by the local utility. The inverter acts as a link to the outside world with three important functions:

1: Power tracking function of the inverter- The operation of a photovoltaic array is controlled by the inverter. As the sun rises in the morning the inverter connects the photovoltaic array to the utility system. As light and temperature change through the day, the inverter adjusts the array current and voltage to maximize efficiency of the system by tracking the maximum power point. As the sun sets, the inverter disconnects from the system.

2: The Inverter Function- the inverter changes the direct current from the photovoltaic array to an alternating current with a frequency and voltage matching the supply from the local utility.^[11]

3:The Safety Component- Inverter's must meet specific safety and power quality requirements. The inverter will monitor voltage and frequency and will shut down if they deviate from a specific range.

The inverter is considered an electrical component that will require periodic inspection and maintenance. The inverter has a screen that indicates power production so it's important that it is installed in an accessible location and should be located in a dry and temperate environment, unless it is designed specifically for outdoor use.

Types of electrical configurations

Photovoltaic systems can be configured in many ways. The PV panels and their rated peak power of about 50 W to 300 W can be configured to maximize output efficiency.^[12]

Central Inverter Design: Modules connected in series to form a string. The strings are connected in a parallel to form an array. One central inverter transforms the DC electricity to AC current to be fed into the grid.^[13]

String oriented Inverter Concept: Each single string of modules connected by one single inverter.

Multi String Inverter Design: Single inverter's allow for optimal power tracking for a single string of PV modules.

Concerns with solar power inverters

If the PV system is connected to a grid it cannot be connected during a power outage.

References

1. Luo, Fang Lin, and Hong Ye. Advanced DC/AC Inverters: Applications in Renewable Energy. Boca Raton, Florida: CRC Press, 2017.
2. Prasad, Deo, and Mark Snow. Designing with Solar Power: a Source Book for Building Integrated Photovoltaics (BiPV). South Wales, Australia: Images Publ, 2005.
3. Fang Peng. "A Novel Method to Estimate the Maximum Power for a Photovoltaic Inverter System." 2004 IEEE 35th Annual Power Electronics Specialists Conference (IEEE Cat. No.04CH37551), 2004. https://doi.org/10.1109/pesc.2004.1355436.

Background of project

This photovoltaic system will be mounted on a flat roof, as the structure in which power will be provided is a storage container.

Types of photovoltaic mounting systems (for flat roofs)^[14]

Ballasted Mounting System: A ballasted mounting system uses weights, usually concrete, to hold the PV system in place rather than attaching the system to roof rafters. A weighted mounting system such as this provides a way to install solar systems without making incisions in the rooftop. Making incisions on flat or low slanted rooftops has a greater chance of leading to leaks. This is an economical option and the most common mounting system for flat roofs.

Rail Based Mounting System: A rail based mounting system can also be used on a flat roof, this is the most common system used on common household roofs. These systems attach rails to the roof and the panels are attached to the rails. This may be the superior choice depending on the weight capacity of the roof of the container.

References