Understand the Zero Feed-In concept of electrical energy

The model found in Brazil for the generation and consumption of renewable energy, such as photovoltaic solar energy, is known as Net Metering (Electric Energy Compensation System), established by REN 482 (Normative Resolution No. 482/2012) of ANEEL (National Electric Energy Agency).

This system allows the consumer, whether an individual or legal entity, who has chosen to install a micro or mini energy generator, to use the value of the energy generated to offset their consumption with the local concessionaire.

When there is excess energy generated, it is returned to the consumer in the form of credits, which can be offset against future energy bills for up to 60 months.

Several countries use this system as a way of encouraging and adopting renewable energy, contributing greatly to the diversification of the local energy matrix. But there are other types of systems, such as Feed-in Tariff.

In this system, the consumer can sell the amount of energy injected into the grid according to the tariffs in force in each location, hence the term Feed-in tariff (feed-in tariff or injection tariff).

Stopping consuming energy from the grid?

In some places in the world where solar energy is already established and incentive policies are no longer necessary, such as Germany, the USA and Australia, the commercialization of this energy surplus no longer makes much sense.

This is due to the fact that solar energy has become a very accessible source of energy, with its cost being more advantageous than that of energy sold by energy concessionaires.

When the behavior observed in Figure 1 occurs, that is, when the price of energy from the photovoltaic system is more financially affordable than the energy made available by concessionaires and the electrical system in each region, the excess energy injected into the grid, received by the consumer in the form of credits or even sold, it is no longer advantageous.

And it is precisely by seeing this behavior that the energy storage market becomes extremely interesting and increasingly viable for the public.

Energy storage, whether electrical (batteries) or thermal (heating water in a boiler electricity), allocates the surplus energy to one of these applications, ensuring that its energy is optimized to the maximum and the waste becomes increasingly negligible.

In the electricity sector, there is also a type of energy trading in which the end consumer does not consume their energy directly from energy concessionaires, but directly from a company that sells it. This modality is known as ACL (Free Contracting Environment – Free Energy Market).

The rules, criteria and other information can be found directly in the ANEEL website. It is worth noting that to participate in the Free Energy Market, companies responsible for sales must have energy sources classified as incentivized, such as solar, wind and PCH (small hydroelectric plant).

In this situation, those responsible for generating energy cannot work with excess energy in their system, as they could be fined. Therefore, there is no credit compensation environment here, but rather a contract with pre-defined energy demand values in which the consumer must negotiate in advance with their potential suppliers.

To prevent energy from being returned to the grid in the energy trading environment as in the ACL and, so that maximum energy is reused by storage sources as seen previously, the concept is used Zero Feed-in.

What is Zero Feed-In?

As we saw at the beginning of this article, the term Feed-in Tariff refers to the injection tariff into the network, so the term Zero Feed-in gives us the idea that nothing will be injected into the network, that is, Zero Injection.

This is possible with the help of the Fronius bidirectional smart meter, illustrated below in Figure 2, called Smart Meter, with which the energy generated by the photovoltaic system, the energy consumed by the loads, the surplus energy and, finally, the energy consumed from the grid are all monitored and parameterized through the equipment. This data can be easily illustrated and understood on the Fronius online monitoring platform, Solar.web.

The function Zero Feed-In, carried out with the help of Smart Meter, allows only the energy necessary to power the loads to be drained from the photovoltaic system (Figure 3), as the meter does this work of dosing and understanding how much energy is needed at that moment.

When there is a lot of generation, but little consumption (Figure 4), this surplus is in no way injected into the grid. In the opposite situation, when there is a lot of consumption and little generation, all generation is destined for the loads and the remaining energy needed to make them work comes directly from the grid.

But what is the benefit?

In addition to the Free Energy Market, where this practice is mandatory, for other projects the system Zero Feed-In It can be understood as a very specific situation, as we do not necessarily have to prevent this injection into the network, which will largely depend on the characteristics and legislation of each country.

It is worth remembering that this injection limitation can still be parameterized. For example, you can inject only 10%, 20 or 30% of the energy generated, or you can have a fixed power value (such as 2 kW, for example). This power limitation reveals the following benefits:

• Surplus energy can be stored locally, meaning you don't get rid of it or even waste it (e.g. battery bank);
• Increase in the number of photovoltaic system connections to the grid. Since all the energy generated is already consumed directly, the number of connections does not interfere with the behavior of the local energy distributor's network;
• Postponement of investments in local network infrastructure. Since many photovoltaic systems connect to the grid, the local infrastructure can undergo changes and high investments such as changing cabling and transformers, but when there is no injection into the grid this investment can be postponed;
• Inhibits the increase in tension. This happens due to the fact that the photovoltaic system ends up not reaching high levels of energy surplus, which does not lead to an increase in grid voltage;
• Change-proof. Whatever changes in energy compensation that the national agency may opt for, power limitation allows your system to always be prepared for the most diverse scenarios;
• Independence, as energy tariffs continue to increase, increasingly using energy from photovoltaic systems is the most affordable option for everyone;
• Efficiency. By using energy according to its consumption, the provision of an energy efficiency project can not only improve the quality of the installation, but also provide smaller and more accessible systems.