Grid Tied Systems

WHAT IS A

GRID-TIED SOLAR ENERGY SYSTEM?

Understanding Grid Tied Solar Systems.

In order to understand what a grid-tied solar system is, you need a basic understanding of what an electrical grid is. In simple terms, an electrical grid is a network of power lines that connect the people who use electrical energy and those who produce electrical energy for them.

Grid-tied PV Solar System

Having a grid-tied solar power system means your home’s solar panel system is linked to your local power utility company’s electrical grid. This is the most common type of solar energy system in Southern Africa, since the setup does not require batteries. Other names for this type of solar power system are grid-direct, grid-intertied, on-grid and utility-interactive.

Why is a grid-tied solar power system attractive for most people?

There are a few main factors that make this solar energy system attractive for your residential or business power needs.

Excess power generated by your solar panels can be send back into the Grid, with Analogue meters running in reverse, providing credits on units used. Whatever credited units running in reverse, can go toward reducing your power bill.

 

You need to sign a net metering agreement with the utility company. This agreement varies from utility to utility.
On cloudy days when your solar panel is not up to supplying all your power needs, you can rely on your electrical grid to supply what you need. This is what really sets it apart from systems not linked to the electrical grid.
Batteries are generally not part of this type of solar system setup. This eliminates battery maintenance costs and the need to buy new batteries every five to ten years, depending on how good the batteries are. These costs can increase your power expenses by a considerable margin.

One disadvantage of this type of system is that when the power goes out, so does your system. This is for safety reasons because utility line men working on the power lines need to know there is no source feeding the grid. Grid-tied inverters have to automatically disconnect when they don’t sense the grid. This means that you cannot provide power during an outage or an emergency You also can’t control when you use the power from your system, such as during peak demand time.

But if a customer has a basic grid-tied system, they are not out of luck if they want to add storage later. The solution is doing an AC-coupled system where the original grid tied inverter is coupled with a battery back-up inverter. This is a great solution for customers who want to install solar now to take advantage of incentives, but aren’t ready to invest in the batteries just yet.

A customer can benefit from net-metering because when the solar is producing more than they are using, they can send power back to the grid. But in times when the loads are higher than what the solar is producing they can buy power from the utility. The customer is not reliant on the solar to power all of his or her load. The main take away is that when the grid goes down, the solar is down as well and there’s no battery back-up in the system.

Grid-tied system with battery back-up

The next type of system is a grid tied system with battery back-up, otherwise known as a grid-hybrid system. This type of system is ideal for customers who are already on the grid who know that they want to have battery back-up. Good candidates for this type of system are customers who are prone to power outages in their area, or generally just want to be prepared for outages.

With this type of system, you get the best of both worlds because you’re still connected to the grid, while also lowering your utility bill. At the same time, if there’s a power outage you have back up. Battery based grid-tied systems provide power during an outage and you can store energy for use in an emergency. You are able to back up essential loads such as lighting and appliances when the power is out. You can also use energy during peak demand times because you can store the energy in your battery bank for later use.

Cons of this system are that they cost more than basic grid-tied systems and are less efficient. There are also more components. The addition of the batteries also requires a charge controller to protect them. There must also be a sub panel that contains the important loads that you want to be backed up.

Not all the loads that the house uses on the grid are backed up with the system. Important loads that are needed when the grid power is down are isolated into a back-up sub panel.