From residential solar panels to large-scale battery energy storage systems (BESS) that help stabilize the power grid
Batteries aren’t just important for electric vehicles. They’re also playing an increasingly significant role in the energy sector, where they allow electricity to be stored when it’s in surplus and used later when needed. From a few kilowatt-hour storage system at a single-family home to megawatt-scale containerized systems, the basic principle remains the same: to separate the time of electricity generation from the time of its consumption.
The topic of the practical use of battery systems was addressed by Ing. Daniel Hrčka from Viessmann Climate Solutions in his presentation “Battery Energy Storage Systems in Practice” as part of the “Battery Value Chain” webinar, which SEVA organized for the Young Designers’ Cup as part of the SEVA Academy educational platform.
The goal of the webinar was to introduce students and young engineers to the entire battery value chain—from research and production through electric vehicles and the energy sector to collection, safe transport, recycling, and returning raw materials to the cycle.
Why store electricity at all?
Electricity generation and consumption naturally do not always occur at the same time. This is most easily seen in photovoltaics. On a sunny day, a power plant may generate more energy than a building currently needs, but in the evening or at night, it generates none at all.
Battery storage helps bridge this time gap. Excess electricity is stored in the battery and used later—for example, in the evening, during peak demand, or during a power outage.
However, the importance of the battery lies not only in energy storage itself. A well-designed system can coordinate solar panels, a heat pump, electric vehicle charging, and other building consumption so that as much of the generated electricity as possible is used on-site.
This can result in lower electricity consumption from the grid, lower operating costs, greater use of renewable energy sources, and greater energy security.
A home battery maximizes the use of solar power
Hybrid energy systems—which combine a photovoltaic system, battery storage, and smart consumption management—are increasingly common in single-family homes.
Daniel Hrčka presented the Viessmann Vitocharge VX3 system as an example. Its role is not merely to store excess electricity. The system monitors production and consumption, decides whether to charge or discharge the battery, and can integrate with other technologies in the home.
The principle is simple. If the photovoltaic system generates more electricity during the day than the household consumes, the surplus is stored in the battery. In the evening or at night, when generation drops to zero, the household uses the stored electricity instead of drawing power from the grid.
The greater the proportion of its own electricity a household can consume on-site, the more efficiently it uses its photovoltaic system.
From 5 to 30 kWh, depending on the household’s needs
Residential battery systems have a modular design. Therefore, the capacity does not have to be the same for a small single-family home as for a household that uses electricity for heating, cooling, and charging an electric vehicle.
In the presented solution, a 5 kWh battery module serves as the base. Two modules create a storage system with a capacity of 10 kWh, three modules provide 15 kWh, and the maximum cascaded configuration allows for up to 30 kWh.
This principle is also important from the perspective of energy system design. The storage system does not need to be sized for the maximum possible capacity. Its capacity can be adapted to the household’s actual consumption, the size of the photovoltaic system, and the way electricity is used.
A home with standard electrical appliances will have different needs than a household with a heat pump, air conditioning, and an electric vehicle.
LFP Batteries: Safety and Thousands of Charge Cycles
The presented solution utilizes LFP (lithium-iron-phosphate) technology. This is one of the most widely used lithium-ion chemical technologies for stationary battery storage systems.
Its main characteristics include chemical and thermal stability, resistance to overheating, and a high cycle life. The presentation cites more than 6,000 charge and discharge cycles while maintaining capacity.
Cycle life is particularly important for stationary storage systems. Over the course of years of operation, a battery can be charged and discharged thousands of times; therefore, its value is determined not only by its nominal capacity but also by its ability to maintain that capacity over the long term.
A hybrid system does not automatically mean a backup power source
One of the practical topics covered in the lecture was the difference between a battery system and a true backup power source.
Not every system with a battery can continue to power a home during a power grid outage. In a full-fledged backup solution, the system must automatically detect a grid outage, safely disconnect from the grid, and switch the building to off-grid mode.
The battery then powers selected or all appliances, depending on the system’s capacity and configuration. Once grid power is restored, the system automatically returns to normal operation.
Battery storage can thus fulfill two distinct roles: optimizing daily electricity consumption while also serving as an energy backup during outages.
HEMS manages the entire home energy system
The battery itself is only one part of the solution. Software plays an increasingly important role in deciding when to generate, store, consume, or draw energy from the grid.
This is where HEMS—the Home Energy Management System—comes in.
Such a system can display the flow of electricity between the photovoltaic system, the battery, the household, and the distribution grid in real time. It can also set charging and discharging times, manage electricity rates, and allow the user remote access via a mobile app.
In a household with an electric vehicle and a heat pump, it’s no longer simply a matter of “should I or shouldn’t I have a battery?” What’s important is coordinating multiple large appliances so that electricity is used at the most economically and energetically optimal times.
The Same Principle, a Completely Different Scale: BESS
What might be a 5- or 10-kWh battery in a single-family home exists on a scale thousands of times larger in the industrial energy sector.
Such systems are referred to by the acronym BESS—Battery Energy Storage System.
Commercial BESS systems can help businesses optimize consumption and manage peak demand, but their significance extends far beyond that. Large battery storage systems can provide regulatory and ancillary services to the power grid, help stabilize frequency and voltage, and create space for the integration of a greater number of renewable energy sources.
It is precisely this ability to draw and supply energy very quickly that makes batteries an attractive tool for the modern energy sector.
Považská Bystrica: 16.7 MWh of energy in six containers
The presentation also highlighted a specific Slovak BESS project implemented for the Považská Bystrica Heating Plant.
According to the presentation, the system has a power output of 10.350 MW and a capacity of 16.732 MWh at a 95% depth of discharge. It consists of six 20-foot battery containers with a voltage of 1,500 V DC. Each container holds ten battery racks with a capacity of 278.8 kWh. The solution includes an EMS energy management system, liquid cooling, and power inverters.
The project clearly illustrates the difference between a residential storage system and a large-scale BESS. While residential systems operate on the order of kilowatt-hours, large-scale energy systems involve megawatts of power and megawatt-hours of stored energy.
According to Daniel Hrčka, the system in Považská Bystrica was commissioned at the end of 2025 and has also been providing ancillary services since 2026.
A battery container is a small power plant packed with technology
From the outside, a BESS may resemble an ordinary shipping container. Inside, however, it is a complex electrical system.
At its core are battery modules and racks, complemented by a BMS—Battery Management System. The BMS monitors the condition of the batteries and ensures their safe operation.
Another key component consists of bidirectional AC/DC inverters. The power grid operates on alternating current, while the battery stores energy in direct current form. The converters therefore ensure the flow of energy in both directions—when charging from the grid to the battery and when discharging back to the grid.
The container also includes comprehensive fire protection, temperature and smoke detection, alarm systems, and fire suppression equipment.
Liquid cooling monitors the temperature of the batteries
One of the technically important aspects of a modern BESS is thermal management.
The presented system uses a dual-loop liquid cooling system. The primary cooling loop dissipates heat from the container to the outside environment, while the secondary loop, containing water and glycol, distributes coolant directly to the battery modules.
Maintaining the batteries within the proper temperature range affects their performance, lifespan, and safety. At the same time, it allows for an ever-increasing energy capacity to be housed within the same physical space.
A single approximately 20-foot container presented by Daniel Hrčko represents approximately 2.8 MWh of stored energy and has an IP55 protection rating.
Batteries are helping to transform the energy sector
Residential and large-scale commercial storage systems differ in size and economics, but they share the same fundamental characteristic—they allow users to decide when the electricity they generate is consumed.
For households, the goal may be to maximize self-consumption of solar power, reduce electricity bills, and provide a backup power supply.
For large BESS systems, the goal may be to stabilize the power grid, shift consumption across different times of the day, utilize excess generation, or provide regulatory services.
As electricity generation from weather-dependent sources grows, the ability to store energy is becoming an increasingly important part of the energy system.
New technologies also require new experts
Daniel Hrčka concluded his presentation with the topic of education. Viessmann, in collaboration with the State Institute of Vocational Education, has participated in equipping energy-related vocational labs at seven secondary vocational schools in Slovakia.
There, students can work with technologies in the fields of photovoltaics, battery storage, heat pumps, hydrogen, and smart energy solutions.
This is an important part of the energy transition. New technologies not only create new equipment but also a need for people who can design, install, program, operate, and service them.
A battery, therefore, is not just a component of an electric vehicle. It is becoming one of the fundamental elements of a modern energy system—from a single-family home to a large power grid.