Solar energy basics
- Basic knowledge of solar power generation
Current, voltage and watts
Current, voltage, and watts are all related to electricity. Electric current is measured in amperes. You can think of electric current as a number of electrons. Measure voltage and volts. You can think of voltage as the pressure pushing these electrons. More electrons or more pressure pushing electrons means more energy, just like more mass or faster speed of an object means more energy.
Just like you need mass and speed to calculate an object’s power or energy, the same goes for current and voltage. Simply owning one is not enough. Wattage is a measure of power in an electrical system, consisting of amps x volts. Watt-hour is a measure of energy in an electrical system, consisting of Amps x Volts x Time.
AC and DC
By default, electricity will travel in one direction, called direct current, or DC. In a DC circuit, electrons flow continuously in one direction from the power source through the conductor to the load and back to the power source. Initially, electricity traveled through these means. The problem is, DC power is unsustainable because due to the low voltage levels it is difficult to transmit power over large differences without power loss.
Eventually alternating current, or AC, was discovered. An alternator causes electrons to flow first in one direction and then in the other. In fact, the alternator reverses the polarity of its terminals many times per second, and each reversal causes the current to change direction. Alternating current can produce higher voltage levels, depending on how you use it. This gives utilities the advantage of being able to transmit electricity hundreds of miles with little loss by sometimes using more than a million volts because voltage travels more easily than current. Ultimately, when the power returns to your house, it outputs to 100-120VAC and sometimes even 200-240VAC. So most home appliances are AC and when you read a spec sheet you will see voltages in these ranges.
Now that you know the general differences, it’s important to understand the difference in power in direct current (DC) and alternating current (AC). Ignoring efficiency losses in either, the power of both should remain relatively constant. For example, we can take a 200W TV and measure it in terms of DC (12V) or AC (110V). In terms of DC, the TV produces 200W/12V u003d 16.6 amps. In terms of AC power, the TV will produce 200W/110V u003d 1.8 amps. Although the amplifier and voltage values are different, the total power is the same, so the energy consumption rate (excluding efficiency losses) will be the same.
- What are solar modules?
Solar panels in a basic sense work by converting available sunlight into usable electricity. The way we define this power is in watts. Watts are composed of amps and volts. Different panels have different amp and volt ratings, and it’s helpful to know what these numbers mean when looking at a system. You can think of amperes as the number of electrons and voltage as the pressure pushing those electrons.
Equation: Watts u003d Volts x Amps
Element
Solar panels are made up of different components as shown in the picture below. Not all panels have these specific components in specific locations, but generally our panels do.
Solar cells: Solar cells can be seen on the front of the solar panel. Their color and appearance vary depending on the cell type. The type of battery usually defines what type of panel it is, such as monocrystalline, polycrystalline, amorphous, etc.
Frame: Most panels have an aluminum frame, but the frame type may vary depending on the type of panel.
Junction box: The junction box is usually located on the back of the panel. It contains bypass diodes to help reduce power loss due to shadowing. It also serves as a connection and bracket for panel wires.
Photovoltaic Cables: Solar panels come with standard PV wire, which is weatherproof and insulated (as long as there are no exposed copper cables).
MC4 Connector: The PV line ends with an MC4 connector. This MC4 connector is the photovoltaic industry standard connector, is weatherproof and can be used as a connection point for our other MC4 cables such as adapter kits.
Single crystal and polycrystalline
Monocrystalline solar panels are slightly more efficient than polycrystalline solar panels because each type of solar panel uses a different manufacturing technology. Monocrystalline cells are made up of a single crystal ingot, while polycrystalline cells are made up of growths containing multiple crystal structures. Both types of cells are made from silicon ingots, but have higher purity requirements for single-crystal silicon. Therefore, monocrystalline panels are more efficient and therefore more expensive. By using single cells, the monocrystalline silicon base allows greater freedom of movement of electrons, so less energy is lost and efficiency is higher. Most monocrystalline cells have a peak efficiency of 22%, while most polycrystalline cells have a peak efficiency of 18%. Monocrystalline cells are dark blue, almost black, and polycrystalline cells are blue.
Peak solar hours and irradiance
It is important to use peak hours and the wattage of the system to calculate how many watt hours the system produces in a day. You can think of peak sunlight hours as average because there are not enough hours of sunlight during the day. This is so because morning and evening sunlight does not produce as much radiation as midday sunlight. To calculate peak times for each state, radiation is averaged based on high and low points and other factors, such as what is mixed into the atmosphere.
From the data collected it can be seen that below meters in the model, the irradiance level or W/m2 changes throughout the day. Panel output is directly related to W/m2 at a given time. Most solar panels are rated at 1000 W/m2. If the irradiance level is say 500 W/m2, like in the picture at 8am, then you should expect half the output (50%). Due to the fact that your state’s peak solar time is not the time when the sun is out, but rather an average of the low and high points, it can be a reliable number for calculating energy production.
