Renewable energy systems

Design of renewable energy systems to increase energy efficiency

Savesystems - Salerno

Energy Production

It is important to understand why it is essential today to produce energy with renewable energy systems. Traditional energy sources, such as coal, oil, and natural gas, are not infinite and are rapidly depleting, in addition to polluting the planet.

For Savesystems, on the other hand, it is necessary to focus on sustainability, using sources that never run out, such as the sun and wind, to develop systems based on sustainability, innovation, and energy efficiency. Only in this way can clean energy be generated in respect of the environment, for a continuously evolving green choice.

Photovoltaic Systems

Solar energy is one of the most promising renewable energy sources, and photovoltaic systems are among the main technologies that harness this energy to produce electricity.

A photovoltaic system is a setup that converts solar energy into electricity using photovoltaic panels. These panels are composed of photovoltaic cells that transform sunlight into electric current through the photovoltaic effect. The electricity generated can be used to power appliances, lighting, and other electrical devices.

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The Installation of a Photovoltaic System Offers Numerous Benefits Both Economically and Environmentally:

Energy Savings: By generating electricity from solar energy, it is possible to reduce electricity costs from the grid. Self-consumption of the energy produced by the photovoltaic system during daylight hours helps reduce the purchase of electricity from the grid.
Reduction of Emissions: Using solar energy to generate electricity reduces greenhouse gas emissions and air pollution caused by fossil fuels used to produce electricity.
Incentive Tariffs: In many countries, there are incentive tariffs for energy produced by photovoltaic systems, allowing a financial return on the investment.
Energy Independence: With a photovoltaic system and a storage solution, it is possible to become partially or fully independent from the traditional power grid, decreasing reliance on non-renewable energy sources.
Durability and Reliability: Photovoltaic panels have a long lifespan and require minimal maintenance. Moreover, solar energy is an inexhaustible and reliable source, ensuring a stable supply of electricity over time.

Hydroelectric Plants

Hydroelectric power stations are also a source of renewable energy. They consist of a series of hydraulic engineering works, and their operation is based on the ability to convert kinetic energy, generated by harnessing the movement of water masses, into electrical energy, which is then collected and distributed.

Hydroelectric power plants can be used to produce energy for domestic and private use as well as for businesses and public entities.

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The power of hydroelectric plants can be classified based on the water head (the height the water falls) or flow rate (the amount of water flowing through the channels and turbines). A third classification is based on the amount of energy they can produce. The power plants are thus divided into:

Micro (Power < 100 kW)
Mini (Power < 1,000 kW)
Small (Power < 10,000 kW)
Large (Power > 10,000 kW)
Currently, hydroelectric plants are most commonly used on a small scale, with micro or mini systems being the predominant types.

How They Work
Typically, an artificial reservoir is constructed upstream, created by a dam that blocks the natural flow of a river, or natural basins (like lakes) may be used. The resulting reservoir is called a catchment basin, and the water level within it is generally maintained at a constant level. Through forced conduits, the water is directed downstream, where a facility containing hydroelectric turbines and an alternator is located.

As the water filters through the turbines, it causes them to move. At this stage, the kinetic energy generated by the rotation of these mechanical instruments is transformed into electrical energy through the alternator. The energy then passes through a transformer, which reduces its intensity while increasing its voltage, allowing the electricity to be distributed.

Sometimes, the water flowing downstream is collected in a special basin and pumped back to the upstream reservoir, refilling it quickly to allow for additional energy production.

Types of Hydroelectric Plants
There are three main types of hydroelectric power stations:

Run-of-River Plants: These plants use the natural flow of the river. The flowing water enters the turbine, which rotates to produce electricity.
Reservoir Plants: These involve the creation of a catchment basin blocked by a dam or the use of existing natural basins, like lakes. Through forced channels, the water flows towards the turbines to generate energy. This type is particularly useful as the water can be regulated according to demand, unlike run-of-river plants.
Pumped-Storage Plants: These plants have a catchment basin downstream as well. At night, when electricity demand is lower, water is pumped back to the upstream basin to generate more electricity the following day.

Types of Turbines
Various types of turbines are employed, with the most commonly used being:

Francis Turbine: Mainly used for plants with medium water head.
Kaplan Turbine: Similar to the Francis turbine, it is used for medium water head.
Pelton Turbine: Employed in plants with high water head.
Crossflow Turbine: Primarily used in small-capacity plants.

Wind Turbines

Wind turbines enable the harnessing of wind energy to convert it into electricity.

Wind generators primarily consist of three fundamental components:

The rotor or wind turbine: This includes the blades, usually made of fibreglass, which are connected to a hub.
The nacelle or gondola, Positioned at the top of the tower, it houses the transformation systems (gearbox and electric generator) and the control systems of the machine.
The tower, This supports the rotor and nacelle while withstanding all the stresses placed upon it.

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How a Wind Generator Works
The operation of a wind generator is relatively straightforward:
The blades begin to rotate under the force of the wind once it reaches the minimum start-up speed. This parameter varies depending on the size of the plant, ranging from a minimum of 2-3 m/s for smaller systems to 5-6 m/s for larger ones. The rotation is then transmitted, via a mechanical gearbox, to an electric generator that converts the mechanical energy produced by the wind into electrical energy. Finally, the generated energy is adjusted to a higher, suitable voltage level using a transformer and fed into the national electricity grid.

All wind generators have a maximum wind speed threshold, beyond which the generator halts production and enters a safety mode to prevent damage to its mechanical components.

Since wind is an inconsistent and unpredictable energy source, the feasibility and design phases of a wind plant require careful analysis. To evaluate the investment's potential and estimate the return on the expense, a feasibility study must be conducted, which includes analysing the wind conditions at the installation site.

Wind Assessment Studies
For medium/large wind power plants, wind campaigns are typically conducted: an anemometer is installed at the site to record wind strength and directions over a period ranging from six months to 1.5 years.

For small/medium wind power plants, long and costly wind campaigns can often be replaced by consulting the Interactive Wind Atlas, a detailed wind map of the Italian territory. This tool allows a thorough analysis of wind characteristics and helps optimise the placement of new wind installations.

With this software, users can focus on individual municipalities and calculate both the annual average wind speed at various heights and the potential energy generation capacity. The atlas also includes a map of specific production, indicating the number of hours per year a plant operates at maximum power.

Classification and Types of Wind Turbines
Wind turbines are classified based on the installation site, technology used, and power capacity.

By installation site, wind plants are divided into:

Onshore: The most common and widespread turbines, installed on land.
Offshore: These are installed in open seas. Although less common due to higher costs compared to onshore turbines, they can produce up to 30% more energy thanks to strong and consistent winds in marine environments.

Cogeneration

Cogeneration refers to the combined production of electricity and heat. These two forms of energy are generated sequentially in a single plant.

Cogeneration systems are also known as CHP systems, derived from the English acronym Combined Heat and Power. If a user simultaneously requires both electricity and thermal energy, instead of installing a boiler and purchasing electricity from the grid, it is possible to consider implementing a system—a cogeneration plant—that produces both electricity and thermal energy.

It is evident how this system can achieve energy savings by reducing fuel consumption.

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Simplified, a cogeneration plant operates using:

A prime mover, which can be powered in various ways;
An electric generator, driven by the engine system, that converts mechanical energy into electricity;
Heat exchangers, which recover heat.
The fundamental types of cogeneration plants differ based on the type of "prime mover" used. The most commonly utilised and established ones include:

Internal combustion engines
Gas turbines
Steam turbines
Combined cycle plants with gas turbines/steam turbines.
The last two types are used for high-power plants and are therefore almost exclusively applied in industrial contexts, while internal combustion engines and gas turbines are suitable for both high-power systems and mini or micro-cogeneration setups.

More modern but still evolving prime mover types include:

ORC turbo-generators
Microturbines
Fuel cell (fuel-cell) systems
Stirling engine systems.