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Types of solar power systems

Mpfana Manu is a mechatronic engineer who's working in green energy electronics products.

Howdy there..in this article you going to explore the different types of solar power systems. Mind that there are types of solar panels and also types of solar power systems, these are two different things.

The panel is just part of a system while a solar power system is an integration of many parts(the panel included of course).

Alright, here's a list of the solar power systems.

  • Grid-tie system
  • Off-grid or Stand-alone system
  • Grid-fallback system
  • Grid-failover system
  • Grid-interactive system

Now lets go through this list and unfold each system to see which means what.

Grid-tie system

This is when you attach your solar power generating system to the grid(the grid is just the public electricity supply you get from electricity-generating companies in your country).

A simplified model of a Grid-tie system, the arrows show the direction of current.

A simplified model of a Grid-tie system, the arrows show the direction of current.

The grid-tie system works like this...
You use electricity generated from your solar panels during the day and if there is any surplus electrical energy left, it's fed into the grid and you're paid for the electrical energy you export.

Yeah, you read that right...
You get paid by the electricity company for the electrical energy units you export into the grid. How much they pay per unit differs from one country to another.

This is not available in lots of countries though, especially in developing countries where the grids are still using old technologies.

But when it gets dark when your solar panels can't cope with the demand of the appliances in your home, the grid then supplies you with electricity.

This is where it gets tricky.

This solar power system makes you money if you use less electricity from the grid than the electricity you export. If you use more than you export, you can only expect your electricity bill to be lower than normal.

Usually, this system makes money if you live in a place that's normally very hot. Places where electricity usage is high during the day(people cooling off) but the usage drops when it gets dark.

In this case, you export more electrical energy when there is a huge demand for electricity and you import from the grid very less during the night.

Off-grid or Stand-alone system

This solar power system is popular with modern RVs and is the simplest of all. Here a solar panel generates electricity and it's then stored in a battery.

The battery then discharges according to your appliances demand. Pretty simple right...

Model of an off-grid solar power system

Model of an off-grid solar power system

However, off-grid solar power systems are generally small and they can only give relatively small electrical units per hour. It's fair to say all stand-alone systems have a peak output of at most 1kWh.

The off-grid systems that can produce more than this are systems with manually fitted extensions of the standard stand-alone system.

A stand-alone system can be used to power up low-voltage appliances directly. Lighting, refrigeration, laptops, tvs, radios. But you certainly cannot expect to use solar electrical power to support your cooking and heating.

Those are too demanding electrical appliances and it's wiser not to even consider using power from your solar panels to lift the demand of such appliances.

Unless you are willing to throw a tonne of money installing a huge solar power system to incorporate the heating and cooking. It's not worth it. Instead, use gas or solar heating systems for your heating and cooking.

Grid-fallback system

This one is a little bit more smarter in design and functionality. And it's the most efficient way in the solar power you generate. Here's how it works...

Simplified model of a Grid-fallback solar power system

Simplified model of a Grid-fallback solar power system

Your solar panels generate electricity and it's then stored in a battery. Then the battery is discharged to meet the demand of your electrical appliances.

When your battery banks(Whoa banks...? Battery banks are just multiple batteries connected together to work like one big battery) go flat, the system switches to the grid power supply.

The solar panels charge the batteries again and when they're charged, you start using the power from your banks again. The process keeps repeating over and over again.

If you use the grid-fallback system, there are no generous payouts from your electricity service provider because you don't export even a trickle of current into the grid.

You only use the grid as a backup plan when your solar power needs a reboot before getting reused again. The grand benefit of a grid-fallback system is that your electricity bill will be a very humble figure. It'll be way less than the normal bill.

Moreover, this solar power system can be extended over time to increase it's capacity. You can scale up the system to a point when the grid doesn't supply a significant amount of power.

This is awesome, feels more like getting rid of the bill forever. Maintenance costs for solar power systems are very small and it wouldn't be a huge drag compared to paying big money for the grid every single month.

Grid-failover system

This type is losing popularity as more and more countries are developing. It's more common in developing countries where frequent power cuts are the norm. A grid-failover system is the direct opposite of a grid-fallback system.

The solar power is the backup of the grid

The solar power is the backup of the grid

With a grid-failover, the solar power is the backup of the grid power supply. The solar panels charge the battery banks and they're only discharged when there is a power cut from the grid.

A system like this is called a UPS (means uninterrupted power supply). Your appliances never go through the "cut".

The reason behind lots of folks ditching this system is that the grid is becoming more and more efficient in supplying electricity as countries develop more.

So folks are upgrading their grid-failover systems into grid-fallback systems in attempt to reduce the monthly bill for the grid.

Grid-interactive system

This one is an upgrade of the grid-tie. It's more like a grid-tie system with a backup plan for power cuts. And because of that it is also a UPS(yeah, I did tell what this means...uninterrupted power supply).

Simplified model of a Grid-interactive solar power system

Simplified model of a Grid-interactive solar power system

It works almost like a grid-tie. You get power from your solar panels and export the surplus power into the grid. The grid supplies you with power when your panels can't cope with the demand.

But with a grid-interactive you still have power when there is a power cut. The solar panels are used to also charge battery banks that would still supply power when there's a power cut from the grid.

Conclusion

Solar power systems are only going to get more and more popular. Solar energy is pretty clean compared to the traditional energy sources and it's free energy.

The installation costs might slap your wallets aggressively but the maintenance is not a big deal. The type of solar system that is best for you depends on your needs, your budget and your location.

I hope you get the best experience with your solar systems. If you got anything to add or questions, just throw them in the comments section. Cheers.

Comments

Jackie on September 30, 2020:

Thank you for an extremely informative article. I look forward to learning more.

Mpfana Manu (author) from Harare on February 22, 2020:

Thanks for the compliment Chitrangada, will keep sharing

Chitrangada Sharan from New Delhi, India on February 20, 2020:

Great informative article, well presented and illustrated.

This is highly technical and I appreciate your efforts in spreading the knowledge to the readers.

In India, the Solar energy is being used at many places, for various purposes.

Thank you for sharing.