What Are Grid-tied Solar Systems?
Discover the essentials of grid-tied solar systems: cost-effective, eco-friendly energy solutions for the modern homeowner.
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Understanding grid-tied solar

Solar panels provide clean energy, but storing the energy generated for later use can be challenging. 

Batteries are often the go-to solution for solar energy storage. But, they are expensive, short-lived and made from non-renewable materials. 

Even the best battery available today, lithium-ion batteries, have a lifespan of 10 years maximum, while solar panels can last over 25 years.

A grid-tied solar system is a creative solution that benefits both the grid operators and the consumers. 

This system generates electricity during the day using solar panels, which are then stored in the grid. 

At night, the stored energy is released back into the system, providing power to the consumer.

What is a grid-tied solar system?

A grid-tied solar system captures solar energy and converts it into electricity for immediate use. 

Excess energy is fed back into the grid. When solar generation is insufficient, the system seamlessly switches to drawing power from the grid. 

It promotes self-sufficiency, reduces reliance on fossil fuels, and contributes to a more sustainable energy ecosystem.

model of grid-tied solar systems
Figure 1: Grid-tied solar system (Source: Grape Solar)

Advantages of grid-tied solar systems

  1. The average consumer can now install solar panels on their house rooftop to generate enough power to fulfill their electricity needs throughout the day and night. 
  2. Any excess electricity generated during the day will be returned to the power grid and retrieved at night, which eliminates the need for expensive and short-lived batteries
  3. Moreover, the consumer can benefit from the state’s encouragement of clean energy and its provision of a rewarding tariff when they enter additional energy into the grid. 
  4. Additionally, consumers located in countries that support P2P energy markets can earn additional income by investing in the house’s rooftop solar panels. 
  5. By installing more solar energy on the roof of the house than they need, the consumer can contribute to reducing carbon emissions from their consumption and others.
  6. Grid-tied solar systems come with benefits for the grid operator. They are considered an additional station to the grid without adding to the cost of establishment, as the consumer fully finances the process of building, operating, and maintaining the station.
  7. Excess energy is sent to nearby stations to reduce losses during long-distance transmission. Transmission lines lose about 10% of energy, especially in countries with large distances between stations and homes.
  8. Grid-tied solar systems enhance the growth and spread of solar energy. They represent 95% of the currently existing energy systems. Therefore, grid-tied solar systems accelerate the grid’s transition towards a more sustainable and environment-friendly grid.

Disadvantages of grid-tied solar systems

The disadvantages of a grid-tied solar system for the consumer are the high initial cost and the need for the grid operator to find a mechanism to guarantee the quality of the devices connected to the network so as not to cause stability and safety issues on the grid.

Components of the grid-tied solar system

Grid-tied system components
Figure 2: Grid-tied system components

The grid-tied solar system consists of solar panels, an inverter, a two-way metre, and some energy-combining and protection devices.

Some grid-tied systems may contain batteries to use the largest amount of self-produced electricity.

Grid-tied inverters

The grid-tied inverter is a crucial component of the solar system that is connected to the network. Its main function is not only to convert the direct current generated by the solar panels into alternating current used by the devices but to also act as a smart device. 

The inverter senses the electricity from the grid, reads its current characteristics, ensures that it meets the requirements of the national electricity code, and then converts the direct current from the solar panels into an alternating current with similar characteristics.

The grid-tied inverter also does the synchronisation task; it performs phase synchronisation to inject the produced current into the grid and function as a power generator.

The grid-tied inverter contains monitoring and communication systems that record the electricity produced by the inverter and send it via Wi-Fi (or other communication means) to a local network or even via the Internet. This data can also be saved locally and displayed on the inverter’s screen.

The grid-tied inverter has more precise and quality specifications than the standalone inverters. This is because the quality of electricity produced by the grid-tied inverter affects the general grid quality, while the standalone inverters only affect the devices connected to them. Grid operators create laws and specifications for devices that can be connected to the electricity grid.

Two-way meter

Another component of the grid-tied solar system is the two-way meter. It is the component that measures the amount of electricity produced by the solar system and injected into the grid, as well as the amount of electricity received from the grid and consumed in the house. 

As a result of this measurement, accounting is carried out between the grid operator and the owner of the grid-tied solar system, either through net metering or through the feed-in tariff, according to the system in force in the country.

How do grid-tied solar systems work?

The solar panels absorb the photons coming from the sun’s rays and turn them into electrons in the form of direct current. 

The grid-tied inverter takes this direct current as input and turns it into an alternating current with the same specifications as the grid.

This current feeds the house appliances, and the surplus electricity is exported to the grid via a two-way metre that calculates the amount of electricity exported. 

When the sun sets, the house is fed by electricity from the grid, and the electricity entering the shed is calculated using the meter in the reverse direction. 

If the regulatory body adopts a net metering system

In that case, the system’s size should be designed to enter an amount of energy during the day that is sufficient for the house for the day and night. The energy surplus during the day should equal the house’s consumption during the day and night.

If the existing system is a feed-in tariff

In that case, the property owner may want to produce more electricity than he needs day and night, so he can sell the surplus to the network operator and obtain profits, and thus invest in the roof of his house, especially if the feed-in tariff is encouraging or there is the possibility of P2P energy trading.

The economics of grid-tied solar systems

If you have a house with a solar system that has a maximum capacity of 5 kilowatts and is connected to the grid, you can expect an average of 4 hours of full irradiation during the summer months. This means that the system will produce 20 kilowatt-hours during the day. 

If your household’s day and night consumption is 15 kilowatt-hours, the excess 5 kilowatt-hours will be exported to the network. Assuming a feed-in tariff of 20 cents per kilowatt-hour, you will earn $1 per day.

However, if the law in force is net metering, any surplus electricity generated during the day will be credited to your account and can be used on days when your electricity production is lower than your consumption due to factors such as clouds. 

This is settled annually between you, the owner of the solar system, and the grid operator.

Summing up grid-tied systems

A grid-tied system has the potential to contribute to our transition towards a greener future significantly. 

It offers numerous benefits, and with some facilitation from governments and organisations to address the initial high capital costs, it can create a real win-win-win situation for consumers, grid operators, and the environment.

Frequently asked questions

The answer is no; it does not work. This is one of the disadvantages of grid-connected systems. It requires a network with a stable electrical supply and is not suitable for areas where outages occur. 

Grid-tied systems are not an alternative to the grid but rather a way to save on the electricity bill or perhaps obtain some additional income, and they are also a way to move towards a green lifestyle for activists in this direction.

The answer is that you can increase your self-consumption in two ways

  1. Shifting loads and trying to use heavy-consuming loads during the day.
  2. Installing batteries to save the excess energy for the night. 
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Author

Dr Samah Hashim
Dr Samah Hashim is a solar energy teacher and researcher. She shares her knowledge by writing articles and producing YouTube videos.

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