Understand in practice how to size hybrid battery-powered systems.

with the participation of Yghor Corrêa – Commercial Director of Solextron Brazil

The Brazilian solar energy market is undergoing a silent and extremely lucrative revolution: the battery era. 

While until recently the cost made storage a less viable technology in a highly price-sensitive market, the current scenario presents significant changes. 

Prices have plummeted, and batteries are now being offered in Brazil at previously unimaginable prices.

When we combine this drastic cost reduction with our high solar irradiance and lower operating costs, we arrive at a surprising fact: the return on investment (ROI) of battery-powered systems in Brazil already surpasses that of developed European countries. We are facing a golden opportunity for integrators who know how to position themselves now.

A crucial problem in market development in Brazil today is a notorious lack of knowledge regarding the sizing of solar battery systems. 

Unfortunately, today integrators are frequently exposed to battery sizing courses based on inaccurate Excel spreadsheet simulations. 

Instead of following the example of developed countries and promoting the use of professional tools, the market is heading towards low quality.

The difficulties in sizing batteries are twofold:

1. It is necessary to have representative consumption profiles, electricity tariff profiles, highly accurate solar energy generation simulation profiles, as well as physical and electrical battery models capable of quickly performing hourly dynamic charge and discharge simulations for a period of 365 days. All this information is impossible to generate and simulate in an Excel spreadsheet with an acceptable level of accuracy.
2. There are different use cases for solar-powered batteries, with different operations (or dispatch) and business cases, such as limited export of surplus solar energy, limiting energy imports from the grid to maximize self-consumption or prevent exceeding contracted peak demand (peak shaving), covering consumption during peak tariff hours, backup/UPS power, and off-grid systems with or without a diesel generator. This requires dynamic control of the battery over different solar generation profiles, which is impossible in a spreadsheet.

Until now, those seeking high-level professional training have found few foreign tools (such as Homer or PVsol), which are extremely expensive, slow, and complicated to operate. But the good news is that it doesn't have to be that way.

To revolutionize this scenario, Solextron, developed in Switzerland, entered the market alongside Belenergy as the only design platform capable of performing precise, fast, and intelligent dimensioning. 

All this combined with an incredibly easy-to-use format, with simple inputs, a user-friendly interface, and processes fully adapted to the business rules and regulations of the Brazilian market. 

The platform uses artificial intelligence to perform highly complex calculations extremely quickly. In this article, we will demonstrate in practice how to design a hybrid system in Solextron.

The following example, run on the Solextron simulator, presents the sizing of an 8,3 kWp solar system installed in a commercial building in São Paulo. For the simulation, an annual consumption of 10.000 kWh was considered, using a typical Brazilian residential consumption profile. 

Note that the highest consumption occurs during the night, which is typical in Brazil. The tariff modality considered was the white tariff, with peak hours in the late afternoon.

Energy profiles without battery

Before analyzing battery sizing, it is important to understand the energy dynamics of a solar installation. In the figure below, you can see in orange the typical solar energy generation on a sunny day, in green the daily consumption profile, in red the surplus solar energy that was not consumed and is exported to the grid, and in brown the energy imported from the grid when there is no solar generation.

Next, we will analyze this same consumer unit with a battery in different application scenarios.

Maximizing Self-Consumption and Immunity to the Uncertainties of Law 14.300

With the current simultaneity factor and the possibility of revising the compensation system in 2029 (which could reduce the value of exported energy, as has happened in European countries), using the grid as a "virtual battery" may become less attractive in the future. 

Given these legal and tariff uncertainties, the use of batteries tends to be a strategic alternative to maximize self-consumption.

The energy dynamics are presented visually (as shown in Figure 3): The battery (pink curve) stores the surplus of unused solar generation and discharges it when consumption exceeds generation. 

But the golden question every integrator needs to answer at the negotiating table is: "Was this battery sized correctly, or is the customer wasting money?" 

To answer this question, the platform provides an instant comparison of the scenario. on e PULL The battery relies on three crucial indicators to close the deal: Payback or ROI, network independence, and utilization factor. 

ROI indicates how long it takes to recover the initial investment, grid independence shows the percentage of solar energy that will be consumed, indicating the degree of autonomy in relation to the utility company, and finally the utilization factor serves as an indicator of good sizing. 

It measures how effectively the battery is used, indicating how many charge and discharge cycles occur per day. A factor of 100% means a complete daily cycle. The rule of thumb is: results above 70% indicate efficient sizing, ensuring that the customer did not buy an expensive battery that is not being used frequently.

In the example analyzed, although the ROI shows a natural increase of about one year due to the inclusion of the battery, the system showed an 18% increase in energy independence, using storage efficiently throughout the year.

Tariff arbitrage – Choose the cost of your energy.

The white tariff allows you to pay less during off-peak periods and more during peak periods. This also occurs in other tariff modalities, such as those for consumers in group A, for example. The problem is that solar energy is generated during the day, but the highest consumption, where the peak tariff is higher, is typically at night. Furthermore, the credit for energy generated during off-peak hours is lower than that for peak hours, and the battery can compensate for this difference. In this case, the battery charges with solar energy during the day and discharges at night during peak hours, generating the following profiles (Figure 4):

In this case, the battery prioritized storing energy only to cover peak tariffs, and thus was used less, i.e., with a lower utilization factor (73%) and consequently less independence from the grid (43%). This is a simple example using the system we are adopting as the standard for the tests presented here, but the Solextron tool can also perform this type of analysis for Group A consumers, considering tariffs (which are already automatically loaded by the platform based on the installation location) and enabling C&I projects with accurate calculations and an attractive return depending on the tariff difference between peak and off-peak periods.

1 - Business expansion, without demand penalties with "Peak Shaving"

Installations with high-power equipment need to pay for a maximum contracted power demand in order to have the necessary infrastructure from the grid. The problem is that when the power imported from the grid exceeds the contracted demand, the consumer unit receives a fine from the utility company. Situations such as holding a large event in a shopping center at night, or the unscheduled restarting of machines on a production line, or even the expansion of some customer process can greatly exceed their typical consumption.

In the example, peak demand was limited to 2kW to illustrate the consumption limit mentioned above. Figure 5 shows the battery discharge when demand exceeds the 2kW limit, demonstrating exactly how the behavior would be in any case that falls under this "Peak shaving" scenario. Solve your client's network limitation or constant penalty problems with the correct approach. The table below shows the indicators already explained for this case, again with the correct sizing based on the utilization factor.

2- Batteries as an ally against reverse flow

In 2024 the ANEEL The Brazilian government approved Ordinance REN No. 1.098/2024, which mandates reverse flow studies for consumer units with more than 7,5 kWp installed. These projects may be rejected if they do not meet the permitted limits for injection into the grid, which in many cases can be zero. Rejections already occur daily in several Brazilian states, and in this case, the objective of the battery is to maximize self-consumption in order to try to reduce energy export to the grid, as shown in Figure 6 for the consumer unit with one and two batteries. 

In this strategy, the inverter's "zero export" or "grid zero" mode acts as an ally, preventing 100% of the energy exported to the grid, while the battery fulfills its role of providing more energy at a lower cost, since it increases the self-consumption of solar energy. The "grid zero" mode must be selected on the inverter because, due to variations in solar generation between winter and summer, it is impossible to avoid 100% export to the grid using only the battery. While the battery significantly reduces export, the system becomes more expensive, increasing the return on investment (ROI) time, as well as grid independence, while the utilization factor decreases, indicating that the second battery begins to oversize the system.

3- Secure your customer's power supply with backup and UPS systems.

Several regions of Brazil suffer from power grid instability, in some cases daily. Battery-powered systems can be used as protection against power outages, increasing consumer comfort and resilience in relation to the grid. This is fundamental for commercial and industrial establishments, which suffer financial losses and may even be unable to operate or lose valuable supplies when without power. The following simulation assumes a power outage period between 16 PM and 20 PM, generally provided by the utility company based on statistical frequency. 

For backup purposes, a new indicator is important, the priority hours service This corresponds to the percentage of hours covered by the battery in relation to the power outage period. The results shown below indicate that only two batteries can cover practically all critical hours, which is the recommended battery sizing for this case. Note that the ROI increases due to the additional cost of the batteries, but costs associated with production downtime, lost customers, and lost raw materials can easily be added to this equation during commercial negotiations to sell value and security to your client, making the increased costs a minor detail compared to the benefits.

4- Battery for Off-grid systems with diesel generator

In isolated installations, usually rural and without access to the electrical grid, solar energy combined with batteries can be a valuable asset, providing power for daily activities. As with backup power, it's necessary to specify the periods when the owner needs power—in other words, the priority hours—but in this case, the "charge from grid" option should be disabled. While we already know from the previous example that two batteries can meet almost all priority hours, two new indicators become relevant: energy deficit which must be covered by the diesel generator, and the total solar loss This refers to solar energy that will not be used for consumption and ends up being suppressed by the solar inverter. 

It is now observed that the owner saves approximately 37% on diesel that would be needed without the use of batteries to cover critical hours, and less solar energy is lost. This does not necessarily mean that it is possible to reduce the installed solar capacity, as there are hourly and seasonal variations in generation and consumption that can lead to power shortages for consumption and/or battery drain, but it demonstrates that the battery can help even in more extreme cases and reduce the customer's operating costs.

Real-world calculations for battery storage systems require highly complex physical, electrical, and financial models. Designing equipment costing thousands of dollars using amateur simulation courses or Excel spreadsheets is like blindly gambling with your client's money.

Brazilian integrators can (and should) access the best technologies on the market. Solextron, in strategic partnership with Belenergy, brings the world's number one design solution — robust in its calculations, yet incredibly intuitive and fast in project execution.

Take the ultimate technological leap for your company. Present unquestionable proposals, guarantee impeccable installations, and sell much more, conveying authority and precision. Discover the Solextron platform today and get ready to lead the battery revolution in Brazil with us! 

The opinions and information expressed are the sole responsibility of the author and do not necessarily represent the official position of the author. Canal Solar.