What Is a Solar Inverter?
The sun’s rays strike the photovoltaic cells in your solar panels, producing a flow of direct current electricity. Solar inverters convert this DC energy to alternating current to power your home and the grid.
Inverters ensure that solar power isn’t sent through the external power lines, avoiding potential electric shocks to line workers. They can also send excess solar electricity back to the grid to earn net energy credits.
Inexpensive Inverters
An inverter for solar panels converts the DC electricity from your solar array into AC to power appliances and tools. It can also be used to charge batteries, but most battery systems will have their own inverters. An inverter should be properly sized to the size of your solar array and the amount of energy your home consumes throughout the day. Incorrectly sized inverters can cause premature failure and increase operating costs.
Choosing the right inverter can save money and help you reach your financial goal faster. You’ll want to consider its warranty and what is included with it. Most microinverters offer warranties covering anti-islanding; short circuit; reverse polarity; low voltage and over-temperature protection.
Some inverters are designed to be paired with a power optimizer, which maximizes the output of individual panels. This allows them to perform as efficiently as possible, even if one panel is shaded or not facing the sun. It can also improve the performance of a system with partial shading and different roof configurations. Power optimizers are more expensive than simple string inverters and require additional components to be installed on the roof.
When comparing inverters, look for CEC (California Energy Commission) efficiency ratings. These indicate how efficient an inverter is at various power levels. You’ll also want to look at the inverter manufacturer’s graph of efficiency versus load, which will tell you how efficient it is under varying conditions.
Power Optimizers
Power optimizers can be paired with compatible string inverters to help extract the maximum amount of energy from each solar panel. They do not require any complicated wiring and are simple to install. Power optimizers help maximize efficiency in all weather conditions and ensure a smooth system performance. However, they do require some specialized settings and monitoring.
Power optimizers work by regulating the Solar lnverter DC sunlight voltage of each panel in your solar array before sending it to your inverter. They also negate the effects of shading by boosting the voltage of each panel that is being shaded.
However, the bucking and boosting of the power by the power optimizers can also reduce your system yield. This is especially true early in the morning and late in the afternoon when there are longer shadows. In addition, the internal power consumption of the power optimizers can outweigh the additional energy yield of the extra 4% to 5% that they may deliver in these low-irradiation times of day.
While the European weighted efficiency that is often listed on the datasheets of a power outdoor battery power supply optimizer may be as high as 99%, there are no standardized testing procedures for this figure. As a result, PVsyst does not use this parameter in the system sizing dialog. Instead, the specialized optimizer parameters dialog is used.
Maximum Power Point Tracking
Many solar PV system owners don’t understand the power benefits of maximum power point tracking (MPPT). In simple terms this funky sounding feature squeezes more electricity out of your panels than a standard charge controller.
In any PV panel, as the temperature and solar irradiance conditions change throughout the day, the power-voltage characteristics will vary in a bump-shaped curve, with one particular point – referred to as the maximum power point – being higher than all other points. This is where the current multiplied by voltage reaches its highest value, and is located on the red line in the graph above.
The job of an MPPT is to make sure the inverter operates at this point, maximizing the power being delivered to your home. The MPPT control algorithm does this by regularly sweeping the entire PV panel output-current curve and finding the operating point where it produces the most energy.
Most MPPT controllers are digital – they use power electronics to continuously monitor the panel current and voltage variations, and compare them with your battery’s voltage to find the best match. There are some non-digital MPPT charge controllers around as well, but these tend to have less efficiency than their digital counterparts and can be unstable under certain circumstances – such as when a cloud moves overhead.
Battery Storage
Using battery storage in conjunction with a solar inverter can add significant value to a PV system. It can help offset grid electricity usage during peak times, and it can allow homeowners to take advantage of time-of-use tariffs or net metering programs.
There are several different types of battery systems, including lead-acid batteries (similar to the ones used in automobiles) and lithium-ion batteries. The choice depends on the homeowner’s energy needs and budget. Lead-acid batteries are the most common and are usually inexpensive, but their lifespan is only about 10 years. Lithium-ion batteries are more expensive but offer a longer lifespan, ranging from 15 to 20 years.
When sizing battery storage capacity, it’s important to know how much energy the household consumes on a daily basis and how often appliances are used. For example, a small battery system may be able to power a refrigerator, a few lights, and a Wi-Fi router, but it will deplete quickly with larger loads.
Most battery systems today charge the battery using Direct Current (DC) and provide your home with power via Alternating Current (AC). Some battery solutions also include a microinverter to prevent the battery from overcharging and shortening its life. It’s important to check with your local Authority Having Jurisdiction (AHJ) to understand any permitting requirements or requirements for updating your interconnection agreement before installing a battery solution.
