Emergency Power, Battery Backup Power System or Island Microgrids - What Are the Differences?

Whether emergency power, battery backup power system or Island Microgrids, the goal for all variants is to use one's own power from the PV system independently of the public grid. 

If you buy a PV system, you want to use as much of your generated electricity as possible yourself. But what about in the event of a power failure - can I still use the electricity from my PV system? Do I also need a battery storage system? First of all there are some questions. We will take a closer look and discuss the different technical solutions.

Power outages have always existed, but in recent years we have repeatedly experienced longer and more widespread outages - one of many reasons why it is becoming increasingly important for many that the PV system also provides power when none is available from the public grid. However, there are now different ways of doing this. While to some it is important that the most important consumers, such as the refrigerator and freezer, continue to run, there may also be a desire that all consumers can continue to run in the event of a grid failure. In the past, this job was usually done by diesel generators, but today PV systems are increasingly being used for this purpose. In addition to these private applications, there are also commercial applications. There may even be the requirement to supply entire companies with the PV system in the event of a power failure.

What then comes in addition are applications where houses without connection to the public net are supplied, like e.g. mountain huts.

Behind these variants, however, is also a lot of technology and therefore effort, which is why you should consider well in advance which solution you want to have for yourself. We take a closer look at the different variants.

Emergency Powers System Definition

An emergency power system is usually used when you want to supply the most important consumers despite a power failure. It is important to know that usually grid-connected inverters are used. This means that the inverter synchronizes with the connected grid and feeds into it. If there is no mains voltage at the inverter, it recognizes this and stops feeding. This means that in the event of a grid failure, nothing more is produced by the PV system. The reason for this is to prevent PV systems from feeding power back into the grid even though the grid does not actually carry any voltage. This would be fatal during maintenance work by the grid operator, for example, if electricity suddenly flowed through the lines again.

Now, however, there are emergency power systems, what is done differently?

With these systems, an automatic switchover ensures that in the event of a power failure, the house network is completely disconnected from the public network. This means that the electricity from the PV system cannot be fed back into the public grid.

In addition, however, the emergency power supply-capable inverter must also perform an important task. Usually, the excess power is simply fed into the grid, but this is no longer possible. The inverter must limit the power to the amount that can be used directly in the house. This means that even if 6kW could be generated, but only 2kW is consumed in the house, the inverter must reduce the power to the 2kW by selecting a different operating point.

With an emergency power supply, you can choose which consumers you want to use even in the event of a grid failure. These are then connected to a separate outlet, which is also supplied in the emergency power. Depending on the system, this can be 1-phase or 3-phase. Theoretically, you can also supply all consumers in the house, but that would already go in the direction of backup power. With the PV system, you can only supply your consumers with emergency power if sufficient power is generated. However, this would not be possible at night. For this case a emergency power battery serves. This can be charged with surplus during the day and provide the energy for the consumers again at night. This can of course also be used in the case of emergency power. On bad days in winter, for example, there is often no surplus that can be loaded into the storage. For this case there is nevertheless the possibility that one gives a minimum capacity to the memory, which reserves this for the emergency power case.

Battery Backup Power System

The battery backup power system is very similar to the emergency power system. These terms are often mixed together and in the vernacular emergency power is often used for both variants. Emergency power is often used in advertisements because it is usually more familiar than battery standby power. The main difference, however, is that in the event of a power failure, the emergency power system only supplies selected consumers, whereas the battery backup power system continues to supply all consumers and thus the entire house.

The challenge here is clever planning and design. If you want to continue to supply all your consumers in the event of a grid failure, a large amount of power is of course required, which can be drawn exclusively from the PV modules or from the battery backup power system.

Depending on the power and quantity of the consumers in the house, the size of the system and the storage capacity must also be selected. Especially consumers with high starting currents such as pumps and motors can place a very high demand on such a system. Therefore, it is always important to consider in advance what I want to supply in the event of a grid failure and how I have to dimension my system and my battery backup power system for this. The charging and discharging capacity of the storage unit also plays a major role here. Otherwise, you will quickly be left in the dark.

Island Microgrids System

By far the most technically demanding system is the Island Microgrids system. Here, it is basically assumed that there are no connections to the public grid. Applications are found for example in mountain huts and other buildings far away from any connection to the public grid.

Especially in eastern countries, there are many plants that are connected to the public grid, but have to deal with longer outages. At these times, the plants should then also be island-capable. In principle, one can say that it is an Island Microgrids system, if the plant is designed to work for a long period without connection to the public grid.

There are not many well-known manufacturers who offer inverters that can work permanently without connection to the public grid. You have to imagine that the inverter always tries to get the maximum power out of the modules by finding the optimal operating point. The power can be taken directly from the consumers in the house and the surplus is simply fed into the grid. This is exactly what is not possible with an off-grid system. The produced power may only be as high as the amount that can be taken directly. Especially with fast load changes, this is a major technical task. But here, too, there is a solution, which we will take a closer look at shortly.

We now know about the differences emergency power, battery backup power system or Island Microgrids, but we also want to know how to implement them. Contact BSLBATT ESS battery, we have the lithium battery solution for you!