The Five Configurations for Solar Power
If you want to create a solar power electricity installation, it is important to choose a configuration. In this article we want to illustrate to you the five different configurations you can choose from:
- Stand-alone (also known as off-grid) without grid power charge function
- Stand-alone (off-grid) with grid power charge function
- Grid-tie that feeds all the solar-powered electricity to the grid
- Grid-tie that only feeds the surplus solar-powered electricity to the grid
- Grid-tie with battery backup
Stand-alone/off-grid without grid power charge
Stand-alone is the most popular type of solar installation worldwide: it provides power to locations where no other source is easily available. And this is exactly solar photovoltaics’ main purpose.
The solar panel generates power, the energy is stored in a battery and then used as required.
In general, stand-alone systems are comparatively small systems, typically with a peak power generation of under one kilowatt. It is often a good idea to start with a very small and simple stand-alone system first; this configuration is ideal for all kinds of projects.
Stand-alone/off-grid with grid power charge
This grid power charge function is ideal when solar power is not enough for your home application because the system with this function can automatically charge the battery by grid AC power.
Grid-tie: feed all the solar-powered electricity to the grid
All the electricity produced by your solar system is fed into the grid so you buy the electricity you need from the electricity companies.
Feed-in tariff schemes vary around the world and are not available everywhere. Where they exist, your local electricity company buys electricity from solar producers at an agreed rate per kilowatt-hour. In some countries, this price has been set at an inflated rate by the government in order to encourage people to install solar. In other countries and regions, the price is agreed by the electricity companies themselves.
Grid-tie: only feed the surplus solar-powered electricity to the grid
With this kind of system installed, your home runs on solar power during the day; any surplus energy that you produce is then fed into the grid. In the evenings and at night, when your solar energy system is not producing electricity, you then have to buy your power from the electricity companies in the usual way.
The benefit of grid-tie solar installations is that they reduce your reliance on the big electricity companies and ensure that more of your electricity is produced in an environmentally efficient way.
One disadvantage of most grid-tie systems is that if there is a power cut, also the power from your solar array is cut. Grid-tie can work especially well in hot, sunny climates, where the peak demand for electricity from the grid often coincides with the sun shining, thanks to the high power demand of air conditioning units. This type of system also works well where the owners use most of the power themselves.
Grid-tie with power backup-also known as
a grid-interactive system
This system combines a grid-tie installation with a bank of batteries.
You set up ‘protected circuits’ within your building that will continue to receive power during a power outage; this ensures that a sufficient quantity of power remains available for running lights, refrigeration and heating controllers.
If there is a chance for the main power to be lost for several days, it is also possible to design a system to incorporate other power generators into a grid-interactive system, such as a generator. This would allow a grid-interactive system to work as a highly efficient uninterrupted power supply (UPS) for extended periods of time.
The cost of a grid-tie system with power backup is higher than a standard grid-tie system, because of the additional cost of batteries and battery controllers. Typically, having power backup will add 12–20% of additional costs over a standard grid-tie system. As with normal grid-tie systems, it is possible to sell surplus power back to the utility companies in some countries, allowing you to earn an income from your solar energy system.