Solar energy

Currently, the most common method of exploiting solar energy is photovoltaic installations.

In just a few years, the photovoltaics market in Poland has seen remarkable growth. This market, which involves solar panel installations for both individuals and businesses, is advancing quickly and is currently the most developed among all renewable energy sectors in the country. By the end of 2020, the total solar panel capacity had surged by 259% to reach 3.96 GWp. Projections suggest that by 2025, the combined solar panel capacity could reach a substantial 7.8 GW. Recently, a new electricity production record from solar energy was achieved in Poland.

One key reason for the popularity of these systems is their low operating costs, which make them highly competitive when compared to other renewable energy sources. Consumers are drawn to their ease of use, attractive design, silent operation, and the fact that they do not release pollutants while generating electricity.

How do we use the sun?

It’s widely understood that our planet’s existence relies on the sun. Electricity has become an indispensable part of our lives, and as our consumption grows, we seek increasingly efficient and eco-friendly methods of generating it. Harnessing the power of the sun has become the go-to choice for many. Throughout history, humans have utilized solar energy, initially for activities like plant growth and heat production, and now, in modern times, for generating and storing electricity.

There are three basic mechanisms for converting solar radiation into other forms of energy:

Photobiochemical conversion involves the transformation of energy within chemical bonds. It takes place in solid fuel sources like fossil coals, crude oil, and biomass.

Photothermal conversion, on the other hand, focuses on converting solar energy into heat. This process finds application in various technologies, including solar collectors, thermal diodes, solar ponds, and heliopower plants. Heliopower plants employ heliostats, mirrors that track the sun’s apparent movement, reflecting and redirecting solar radiation to a specific receiver. The receiver’s role is to convert solar radiation into heat.

Photovoltaic conversion, currently the most widely used and advanced method, centers on converting solar radiation into electricity. The science and technology field dedicated to generating electricity from sunlight is known as photovoltaics, often abbreviated as PV.

Using solar energy, electricity can be generated in several ways

The heliothermal method, a derivative of photothermal conversion, employs mirrors (heliostats) or tubular solar collectors to harness solar radiation’s heat. This heat is then directed to a turbine, where it raises the temperature of contained steam. Consequently, this process drives a generator, producing electricity.

In contrast, the helioelectric method relies on the photovoltaic phenomenon, which generates an electromotive force within a semiconductor, typically a photovoltaic cell. This approach encompasses photovoltaic (PV) installations and farms, where sunlight is directly converted into electricity using these photovoltaic cells.

Heliothermal method – Andalsol heliothermal power plant. photo: IEO report? Photovoltaics market in Poland 2020

Inverter – heart and panel – power? what does a PV installation consist of?

A photovoltaic installation is a set of devices that convert solar radiation into electricity that we have in the socket. Its most important elements are:

• Photovoltaic panels, commonly referred to as solar panels, capture sunlight and generate direct current (DC) electricity.
• An inverter, also known as a power inverter, plays a crucial role in the system. It’s responsible for converting the DC electricity produced by the panels into alternating current (AC) electricity that matches the parameters of the standard electrical grid.
• Protection systems are essential components, positioned both on the DC side before the inverter and on the AC side after the inverter. These systems typically include overcurrent circuit breakers and surge arresters to safeguard the entire setup.
• Connecting all these components are cables. These cables link individual panels to each other, connect a group of panels to the inverter, and establish a connection between the inverter and the main switchboard.
• A sturdy and well-designed construction framework is essential to support the panels, ensuring they are securely mounted and properly positioned for optimal sunlight exposure.

How does the installation produce electricity? Photovoltaic phenomenon

A PV installation harnesses the photovoltaic phenomenon to generate electricity. This process occurs when solar radiation interacts with photovoltaic cells.

These connected cells come together to create a PV module. The key components of a solar cell are layers with distinct p and n conductivity, where electrons are set free, resulting in the generation of electric current.

A PV panel isn’t made of pure silicon because pure silicon lacks a sufficient number of valence electrons, resulting in low conductivity. To enhance its conductivity, a process called doping is employed, where atoms of other elements are introduced into the silicon crystal. This creates doped semiconductors with improved conductivity.

In the case of an n-type semiconductor, it is doped with elements like phosphorus (P), which introduces an additional electron, creating an unpaired electron.

Conversely, a p-type semiconductor is achieved through doping with elements like boron (B), which has three valence electrons, one less than silicon. This deficiency creates a “hole” in the crystal structure.

How is electricity produced in a solar panel?

When sunlight hits a PV cell, it provides energy to the panel, causing an extra electron to become excited and break free from the valence orbit of the phosphorus atom. These surplus electrons in the “n” region then flow through the “pn” junction to the “p” region. In the “p” region, these electrons fill the holes present. Simultaneously, as an electron escapes from the “n” region, new holes are created. This process is known as hole current.

If we connect electrodes to the “n” and “p” regions, the electrode connected to the “p” region becomes negatively charged, while the one linked to the “n” region becomes positively charged. When we close the circuit, such as by connecting a light bulb, electric current starts to flow, causing the light bulb to emit light.

Photovoltaic cells are most often produced from silicon using the following technologies:

• monocrystalline silicon,
• polycrystalline silicon,
• Amorphous silicon.

Monocrystalline panels currently lead the way in the PV (photovoltaic) market. They boast the highest efficiency compared to other available options, and their cost has been steadily decreasing over the years, contributing to their growing popularity.

Off-grid or on-grid?

Based on the consumer’s preferences, different types of solar installations can be distinguished. One such type is the “off-grid” installation, which operates independently and is not connected to the power grid. These systems incorporate energy storage and are typically used in situations where connecting to the power grid is not feasible or is prohibitively expensive and time-consuming. An example of this application is in remote locations like summer houses.

Benefits of using an off-grid installation:

• ensures complete independence from future energy price increases,
• no impact of the power grid on installations, no interruptions in energy supply and production,
• modular structure, which allows for any expansion of the installation at any time,
• the ability to obtain electricity in the most inaccessible places,
• possibility of storing electricity.

Disadvantages of off-grid installation:

• much more expensive than a grid-connected installation, mainly due to the cost of energy storage,
• additional capital expenditure approximately every 5 years? batteries should be replaced periodically depending on their correct use,
• variable costs of energy storage, the price may increase over the years,
• To ensure good operation of the installation, the life and efficiency of energy storage facilities must be monitored,
• energy storage devices should be installed in places with appropriate operating conditions and separated from residential premises.

On-grid

When working with the power grid, a crucial component is the inverter, which converts the direct current (DC) generated by the solar panels into the alternating current (AC) used in households. This grid-connected setup, often utilizing a net metering system, is the most popular choice for both individual and business consumers.

Here’s how net metering typically works: Any surplus energy produced by the installation is sent back to the grid, where it is stored. Depending on the capacity of our installation, we can retrieve a significant portion of this surplus energy from the energy company within a year, typically around 80% or 70% of it. However, there is a commission charged on the surplus energy based on the installation’s power:

• For installations up to 10 kWp, the energy company charges 20%.
• For installations with a power of more than 10 kWp and less than 50 kWp, it’s 30%.

To maximize cost savings, it’s advisable to consume as much energy as possible in real time. This can be achieved by optimizing the use of electricity for purposes like heating water, running home heating systems, air conditioning, charging electric vehicles or scooters, and doing laundry during daylight hours when solar power generation is at its peak.

Advantages of network-connected installations:

• the Act on Renewable Energy Sources specifies how the prosumer  settles  accounts  with the energy company for on-grid installations,
• can theoretically be performed in any place where there is an option to connect to the power grid,
• diversification of energy sources and reducing dependence on electricity supplies from the power grid,
• increasing the value of the property in the area where the installation is located.

Disadvantages of on-grid installations:

• in the event of a failure in the distribution network and lack of voltage, the renewable energy generator will be disconnected, so the facility, despite having its own electricity producing installation, will remain without power,
• high variability and uncertainty of the constant occurrence of renewable fuel (weather changes) and power supply dependent on the distribution network,
• possibility of introducing limitations by the generator of the power generated into the distribution network,
• In the future, the operator may be able to charge additional fees for transmitting energy generated in the RES installation through the distribution network.

Hybrid

An effective solution in situations where a modest amount of energy is needed, such as for summer houses or standalone devices like traffic lights, involves combining photovoltaic (PV) panels with a wind turbine. In these scenarios, hybrid energy generation systems that incorporate a small wind turbine along with PV panels, coupled with energy storage solutions, have gained popularity. This approach ensures a reliable and sustainable power supply for these specific applications.

The PV market continues to experience growth, particularly in the prosumer (producer-consumer) and farm developer sectors. Notably, installation prices have been on a significant decline, and the adoption of newer, more efficient technologies is on the rise. With increasing electricity consumption, homeowners are actively seeking innovative solutions to meet their energy needs. This trend reflects a growing interest in sustainable and cost-effective energy solutions in the residential and agricultural sectors.