What is solar energy?
Solar energy is the energy of solar radiation that can be used in a building in several ways. The two most popular solutions are: photovoltaics, which produces electricity, and solar collectorsthat heat water.
In practice, when a homeowner talks about "solar energy", they most often mean PV photovoltaic panels mounted on the roof or on the ground. Such a system produces DC electricity, which the inverter converts into AC electricity used in the home.
PV panels convert sunlight into electricity.
Solar collectors are mainly used for domestic hot water.
The battery allows you to use more of your own energy in the evening or during a breakdown.
How does photovoltaics work at home?
The photovoltaic installation consists of PV panels, solar cables, DC protection, inverter, AC protection and connection to the building's electrical installation. If the system has energy storage, there is a battery and an energy management system.
sun → PV panels → inverter → home / grid / energy storage.What happens to the energy from the panels?
- some of the energy is used immediately at home;
- the surplus can go to the network;
- in a system with a battery, the surplus can charge the energy storage;
- in the evening, the house draws energy from the grid or from batteries, if one is installed.
Advantages of solar energy and photovoltaics
Main advantages
- lower electricity bills;
- producing your own electricity on site;
- greater predictability of energy costs;
- possibility of cooperation with a heat pump, air conditioning and an electric car;
- possibility of expansion with energy storage;
- low emissions during installation operation;
- long operating time of PV panels;
- possibility of using unused roof space.
Practical advantages
- the installation can run automatically without daily operation;
- monitoring shows energy production and consumption;
- good design increases self-consumption;
- power supply of selected emergency circuits is possible in systems with backup;
- PV panels can increase the energy attractiveness of a building.
Disadvantages and limitations of solar energy
The most important disadvantages
- production depends on the weather, time of day and season;
- in winter production is much lower than in summer;
- the system requires space on the roof or ground;
- shading can significantly reduce yield;
- investment requires an initial cost;
- the inverter and protections must be well selected;
- surplus energy is not always of high value;
- in some locations, inverter shutdowns may occur due to grid parameters.
Project risks
- incorrectly selected installation power for the house's consumption;
- too little space on the roof;
- incorrect division of PV strings;
- lack of space for future energy storage;
- no analysis of roof loads;
- incorrectly selected SPD, DC/AC protection or grounding;
- confusing the LOAD output with full power for the entire house.
Solar energy – balance of pros and cons
| Area | Plus | Minus/limitation | What to do? |
|---|---|---|---|
| Energy costs | Less energy purchased from the grid. | Profitability depends on the consumption profile and energy prices. | Count auto-consumption, not just annual production. |
| Roof | You can use an empty surface. | The limitations are size, direction, shade and load-bearing capacity. | Perform panel selection and slope analysis. |
| Production | Most energy in summer and during the day. | Low energy at night and in winter. | Adjust consumption, consider energy storage. |
| Technique | The system can operate unattended. | Errors in strings, inverter and protection can reduce safety. | Make an electrical design and acceptance measurements. |
| Independence | More of your own energy at home. | A standard on-grid installation usually shuts down when the network fails. | For backup, you need an inverter with an emergency function and a correct LOAD system. |
When does photovoltaics make the most sense?
Photovoltaics makes especially sense when your home uses a lot of energy during the day or can shift some of its consumption to production hours. This includes, among others: working from home, air conditioning, heat pump, boiler, charging an electric car or controlling devices via automation.
The more energy you use during PV production, the greater your self-consumption.
A south, south-east, south-west roof or an east-west layout can work well.
Higher electricity consumption can improve the use of your own energy.
The battery can increase its own energy consumption and power selected circuits in the event of a failure.
When should you be careful with your investment?
Not every roof and not every energy consumption profile will produce the same effect. Before installation, you need to check whether the installation will not be oversized, shaded or ill-suited to the needs of the house.
- the house uses very little electricity;
- most energy is used at night, with no energy storage;
- the roof is heavily shaded;
- there is not enough space for a reasonable number of panels;
- the roof structure is in poor condition;
- there are frequent problems with network voltage in the area;
- the offer does not include a clear design, security or warranty.
What does a home photovoltaic installation consist of?
| Element | Function | Why is it important? |
|---|---|---|
| PV panels | They produce DC electricity from sunlight. | Their power, efficiency and temperature coefficient influence production. |
| Mounting structure | Attaches panels to the roof or ground. | It must be matched to the cover, wind, snow and load-bearing capacity. |
| The PV of the string | They connect modules in electrical series. | They must match the MPPT range of the inverter. |
| DC protection | They protect the side of the panels: gPV, SPD DC, DC switch. | On the DC side, you need equipment designed for PV. |
| Inverter | Converts DC power into AC power for use in your home. | It determines the operation of the installation, monitoring and possible backup. |
| AC protection | They protect the connection of the inverter to the building installation. | They must be matched to the power, cables and network layout. |
| Smart meter | Measures energy flow. | Needed for export control, auto-consumption and hybrid work. |
| Energy storage | Stores surplus energy. | It increases self-consumption and can power backup circuits. |
Solar energy and energy storage
Energy storage is not necessary for photovoltaics to operate, but it changes the way electricity is used. Without batteries, excess energy goes to the grid. With a battery, some of this energy can be used later, e.g. in the evening.
More guides on this topic
This page is the home page of the solar energy cluster. Subsequent articles should answer specific user questions.
FAQ
Is solar energy always profitable?
Not always. Profitability depends on the installation price, energy consumption, auto consumption, roof, electricity prices, billing method and possible energy storage.
Do PV panels work when it's cloudy?
Yes, but they produce less energy. The panels use diffused light, but the highest production occurs with good sunlight.
Does photovoltaics work during a grid failure?
A standard on-grid installation usually turns off during a grid outage. For emergency operation, you need an inverter with a backup function, a correct LOAD system and often an energy storage facility.
Do you need to have energy storage?
NO. A PV installation can operate without batteries. Energy storage is an addition that can increase auto consumption and provide power to selected circuits in the event of a failure.
What is more important: the power of the panels or auto consumption?
Both elements are important, but from the point of view of bills, autoconsumption, i.e. consumption of one's own energy on site, is becoming more and more important.
Is it possible to expand the existing photovoltaics?
Often yes, but you need to check the inverter, strings, MPPT, protections, connection power, operator requirements and the possibility of adding energy storage.