Those familiar with solar power will have no problem differentiating between an off-grid photovoltaic system and a grid-connected system. However, for those who have not yet explored this household alternative to getting electricity from a clean source, the differences may be less marked. For the avoidance of doubt, we’ll tell you what each of these options is, in addition to its main components and, key, its pros and cons.
On-grid vs. off-grid solar system: differences.
The very name of each of these options clearly marks the main difference between them: the connection to the general electrical network or the independence of it.
However, it takes a bit more scratching to fully understand what the two alternatives offer. The first, photovoltaic with grid connection, is the most common in homes and, in a sense, the most reliable, as well as the most economical. However, off-grid systems offer full and absolute independence, even if they require a higher initial investment, due to the need for energy storage batteries to guarantee power in the event of the sun.
Off-grid systems: components.
With or without a connection, the truth is that solar energy collector panels do just that, collect it, but do not store it or convert it into AC power suitable for powering various household appliances.
For this reason, all solar home systems will require the corresponding installation of panels, which, in turn, will need to be accompanied by several components. In the specific case of off-grid systems, they will be as follows:
- Batteries for energy storage: This is the key element of this modality (and the one that drives up costs) since, without a good battery, the power supply would be compromised at night or in cloudy weather, to give a few examples. In this type of system, the energy captured by the panels goes to the batteries which, in turn, will provide the energy necessary for the various equipment in the house.
- Investor: For the above to be possible, it is necessary that the home solar system includes an inverter. Its function is none other than to transform the direct current coming from the solar panels into alternating current.
- Battery charge control system: This is another essential item, as it ensures that the battery is not overcharged. So, fundamentally, it optimizes the management of energy entering and exiting equipment for home storage.
Photovoltaic system with connection.
Compared to the previous scheme, homeowners who choose to incorporate solar power, but want to stay connected to the grid, can activate their systems with fewer components. Thus, in this case, it would only be possible to take advantage of the energy captured from the sun with the installation of the panels and the incorporation of an inverter.
In these alternatives, the grid itself would operate in a manner comparable to batteries: when more energy is produced than needed, the excess would be diverted to the grid. The scheme would work backwards in times when there was a deficit of energy picked up by the sun, such as after sunset.
Points of confluence: hybrid systems.
As each of the previous systems has its advantages and disadvantages, there are also hybrid alternatives for grid-connected photovoltaic installations, with the incorporation of domestic storage batteries. These are basically the following:
- Hybrid system for power. In it, the batteries form the central core. So the panels transfer the energy to these equipments and from there it would go to the inverter. This would be connected to the network and, also, to a secondary system for the energy supply of the basic equipment of the house, independently and therefore protected from any blackout.
- Hybrid support system. In this case, the interactive inverters are the part on which the system rotates. According to this scheme, which would be the one followed by Tesla’s Powerwalls, the panels are connected to the inverter, which converts the energy and feeds it into the electricity grid. The inverter would also be directly connected to the storage system and, generally, to the battery charge and discharge management system.
Which option to choose?
It depends on a lot of things, including the area you want to mount the installation in, the budget you have or your energy needs, among others.
The only case in which the recommendation is clear is when the solar system is to be installed in an area where there is no connection to the grid, for example in the case of a detached house. From now on, for this, the initial investment will be more important since a good pinch of domestic systems is taken by batteries for energy storage.
Therefore, if you live in an area with a supply, starting with a connected system and, from there, continuing to explore, can be a good formula to reduce the consumption of energy produced by polluting sources and at the same time , give your electricity bills a boost. However, with the current state of the energy storage market, it is expected that the costs of such equipment will decrease to open up the possibility for many more people to be energy self-sufficient.