How Does Solar Power Works - On-Grid, Off-Grid And Hybrid Systems 2023

How Solar Power Works - On-Grid, Off-Grid And Hybrid Systems 2023

All solar power systems operate on the same fundamental principles. Solar panels use the photovoltaic (PV) effect to convert solar energy or sunlight into direct current (DC) power. The DC power can then be stored in a battery or converted into AC power by a solar inverter, which can then be used to power home appliances. Excess solar energy can be fed into the electricity grid for credits or stored in a variety of different battery storage systems, depending on the type of system.

Solar power systems are classified into three types.

1. On-grid solar systems, also known as grid-tie or grid-feed solar systems

2. Off-grid - also referred to as a stand-alone power system (SAPS).

3. Hybrid - a solar system that is connected to the grid and has battery storage.

Main Components Of A Solar System

Solar Panels

The majority of modern solar panels are composed of many silicon-based photovoltaic cells (PV cells) that generate direct current (DC) electricity from sunlight. The PV cells are connected within the solar panel and to adjacent panels via cables. It is important to note that photovoltaic cells generate electricity from sunlight or irradiance rather than heat. Solar panels, also known as solar modules, are typically linked together in'strings' to form a solar array. The amount of solar energy generated is determined by a number of factors, including the orientation and tilt angle of the solar panels, the efficiency of the solar panels, as well as any losses due to shading, dirt, or even ambient temperature. Because there are numerous solar panel manufacturers on the market, so it worth knowing which are the best solar panels and why.

Solar panels can generate energy even when it is cloudy or overcast, but the amount of energy depends on the 'thickness' and height of the clouds, which determine how much light can pass through. Solar irradiation is the amount of light energy that is usually averaged over the course of a day and is denoted by the term Peak Sun Hours (PSH). The PSH, or average daily sunlight hours, is primarily determined by location and time of year.

Solar Inverter

Solar panels produce direct current (DC) electricity, which must be converted to alternating current (AC) electricity before it can be used in our homes and businesses. This is the primary function of the solar inverter. The solar panels in a'string' inverter system are connected in series, and the DC electricity is brought to the inverter, which converts the DC power to AC power. Each panel in a micro inverter system has its own micro-inverter attached to the back side of the panel. The panel continues to generate DC, but it is converted to AC on the roof and fed directly to the electrical switchboard.

String inverter systems that use small power optimisers attached to the back of each solar panel are also available. Power optimisers can monitor and control each panel individually, ensuring that each panel operates at maximum efficiency under all conditions.

Batteries

There are two types of batteries used for solar energy storage: lead-acid (AGM & Gel) and lithium-ion. There are several other types available, such as redox flow batteries and sodium-ion batteries, but we will concentrate on the two most common. Most modern energy storage systems use rechargeable lithium-ion batteries, which come in a variety of shapes and sizes and can be configured in a variety of ways.

Battery capacity is typically measured in amp hours (Ah) for lead-acid batteries or kilowatt hours (kWh) for lithium-ion batteries. However, not all of the available capacity is being used. To increase battery life, lithium-ion batteries can typically supply up to 90% of their available capacity per day, whereas lead-acid batteries only supply 30% to 40% of their total capacity per day. Lead-acid batteries can be fully discharged, but only in emergency backup situations.

Off-grid solar systems necessitate specialized off-grid inverters and battery systems capable of storing energy for two or more days. Hybrid grid-connected systems use less expensive hybrid (battery) inverters and only require a battery large enough to provide energy for 5 to 10 hours (overnight) depending on the application.

Power Distribution Board

AC electricity from the solar inverter is sent to the switchboard in a typical grid-tied solar system, where it is drawn into the various circuits and appliances in your home. This is known as net metering, and any excess electricity generated by the solar system is either sent to the power grid via an energy meter or stored in a battery storage system if you have a hybrid system. However, some countries use 'Gross metering,' in which all solar energy is exported to the electricity grid.

Excess electricity from hybrid systems can be exported and stored in a battery. Some hybrid inverters may also be linked to a dedicated backup switchboard, allowing some 'essential circuits' or critical loads to be powered during a power outage.

1. On-Grid System

By far the most common and widely used solar systems in homes and businesses are on-grid or grid-tie systems. These systems do not require batteries and are powered by solar inverters or micro-inverters that are linked to the public power grid. Any excess solar power generated is exported to the grid, and you are usually compensated with a feed-in-tariff (FiT) or credits for the energy you export.

On-grid solar systems, unlike hybrid systems, cannot function or generate electricity during a blackout for safety reasons. Because blackouts typically occur when the electricity grid is damaged, if the solar inverter continued to feed electricity into a damaged grid, it would jeopardize the safety of those repairing the network fault/s. Most hybrid solar systems with battery storage can automatically disconnect from the grid (a process known as islanding) and continue to supply some power during a power outage. Batteries can be added to on-grid systems at a later stage if necessary.

This is what happens after electricity reaches the switchboard in an on-grid system:

• It's the meter. Excess solar energy is channeled through the meter, which determines how much power you are exporting or importing (purchasing).
• Metering systems differ in different states and countries around the world. In this description, I'm assuming that the meter only measures the amount of electricity exported to the grid, as is common in most of Australia. Meters in some states measure all solar electricity produced by your system, so your electricity will pass through your meter before reaching the switchboard, rather than after.
• The grid of electricity. Electricity sent to the grid by your solar system can then be used by other grid consumers (your neighbors). When your solar system fails or you use more electricity than your system generates, you will begin importing or consuming electricity from the grid.

2. Off-Grid Power System

Because an off-grid system is not connected to the power grid, battery storage is required. Off-grid solar systems must be properly designed in order to generate enough power throughout the year and have enough battery capacity to meet the needs of the home, even in the dead of winter when there is generally much less sunlight.

Off-grid systems are much more expensive than on-grid systems due to the high cost of batteries and off-grid inverters and are therefore usually only required in more remote areas that are far from the electricity grid. However, as battery prices continue to fall, there is now a growing market for off-grid solar battery systems, even in cities and towns.

There are various types of off-grid systems, which we will discuss further later, but for now I will keep it simple. The diagram above is for a larger AC coupled system. A solar charge controller is used to manage battery charging in smaller scale DC coupled systems, and the DC power is converted to AC using an off-grid inverter and sent to your home appliances.

• The bank of batteries: There is no public electricity grid in an off-grid system. When your property's appliances use solar power, any excess power is sent to your battery bank. When the battery is fully charged, it will no longer receive power from the solar system. When your solar system is not operating (due to inclement weather or at night), your appliances will draw power from the batteries.
• Generator backup: When the batteries are low on charge and the weather is overcast, you will generally require a backup power source, such as a backup generator or gen-set. The size of the generator (measured in kVA) should be sufficient to power your home and charge the batteries at the same time.

3. Hybrid System

Modern hybrid systems combine solar and battery storage into one unit and are now available in a variety of shapes and sizes. Because the cost of battery storage is decreasing, systems that are already connected to the power grid can begin to benefit from battery storage as well. This entails storing solar energy generated during the day and using it at night. When the stored energy runs out, the grid serves as a backup, giving consumers the best of both worlds. Hybrid systems can also charge the batteries using low-cost off-peak electricity (typically after midnight to 6 a.m.).

There are several approaches to designing hybrid systems, but we'll keep it simple for now.

• The bank of batteries. Once the solar power is used by the appliances on your property, any excess power is sent to the battery bank in a hybrid system. When the battery bank has been fully charged, it will no longer receive power from the solar system. The energy from the battery can then be discharged and used to power your home, typically during peak evening hours when electricity costs the most.
• The meter and the power grid. Depending on how your hybrid system is configured and whether your utility allows it, excess solar power not required by your appliances can be exported to the grid via your meter once your batteries are fully charged. When your solar system is not in use, or if the usable power in your batteries has been depleted, your appliances will begin drawing power from the grid.

Conclusion

In conclusion, solar power is a rapidly growing industry, and its popularity is increasing due to the rising costs of traditional energy sources and growing environmental concerns. The three main types of solar power systems are on-grid, off-grid, and hybrid, each with its unique features and benefits.

On-grid systems are the most common, and they are connected to the electricity grid, allowing excess energy to be sold back to the utility company. Off-grid systems are entirely self-sufficient, providing power to a home or business without any connection to the grid. Hybrid systems combine the best of both worlds, using a battery bank to store excess energy while also allowing for a grid connection when needed.

Regardless of the type of system used, solar power provides a clean, renewable energy source that can help reduce our dependence on fossil fuels and decrease our carbon footprint. While there are initial costs associated with installing solar panels, the long-term savings and environmental benefits make it a worthwhile investment.

Frequently Asked Questions –

Q: What is a solar power system?

A: A solar power system is a technology that uses sunlight to generate electricity.

Q: What are the different types of solar power systems?

A: The three main types are on-grid, off-grid, and hybrid systems.

Q: What is an on-grid solar power system?

A: An on-grid solar power system is connected to the electricity grid, and excess energy can be sold back to the utility company.

Q: What is an off-grid solar power system?

A: An off-grid solar power system is entirely self-sufficient and provides power to a home or business without any connection to the grid.

Q: What is a hybrid solar power system?

A: A hybrid solar power system combines the features of both on-grid and off-grid systems, allowing for a grid connection when needed while using a battery bank to store excess energy.

Q: What are the benefits of using solar power?

A: Solar power is a clean, renewable energy source that reduces dependence on fossil fuels and decreases carbon footprint. It is also cost-effective in the long run.