Are You ready?
The awareness connected with RES constantly increases. Do You really know everything? You can actually check it. We prepared a glossary that should be known to all fans of clean energy. This is the first step to become the aware user of RES.
Welcome to RES world.
Quite often we come across the term RES (Polish OZE) and it stands for Renewable Energy Sources. They are called so as they include the sources which exploitation excludes long lasting loss. Their resources simply renew themselves in a very short period of time. These are, among others: wind, rain, tides, sea waves, sunlight and geothermal energy. Contradictory to RES are non-renewable energy sources such as coal, natural gas or uranium.
Solar collectors, photovoltaic cells. Is there any difference?
Many people confuse solar collectors with photovoltaic cells for one simple reason. Both are fixed mainly on the roofs and after installation they actually look alike. However they differ with one basic thing. Solar collectors generate heat. Whereas photovoltaic cells generate electricity that can be used to heat up the houses. Solar collectors come with several solutions, e.g. flat, vacuum tube, vacuum flat. They differ with capacity, way of gaining energy and installation cost.
Photovoltaic cells, alike solar collectors, base their operation on sunlight. However, in this case the result of gained energy is electricity, not the heat. In case of photovoltaic cells gathered power can be turned into energy to heat and power the electric devices. Solar collectors allow to receive only the thermal energy. That is one of the reasons for which the photovoltaic cells are more expensive.
Heat and electricity from wind instead the sun
Wind is also one of the Renewable Energy Sources. Wind turbines are responsible for collecting the energy and they characterise with various features. Before we discuss them, let us explain what exactly wind turbine is.
Wind turbine is a tool that processes the kinetic wind energy (airflow) for the mechanical movement of rotor work that is turned into electricity.
We differentiate two types of turbines in terms of axis rotation.
- Turbine of vertical axis.
- Turbine of horizontal axis.
Both types may also come with a diffuser version. The diffuser helps to better the efficiency.
Horizontal turbines are divided into two types due to direction of air inflow:
- up-wind.
- down-wind.
Turbines of horizontal axis rotation are also divided due to the number of blades:
- single blade,
- double blade,
- three blade,
- multi blade.
How is the electricity made out of wind?
- Wind faces the resistance in the form of a turbine blade,
- Airflow (kinetic energy) is processed into mechanical energy – rotor movement,
- Rotor axis is connected with a generator in a direct way or by a gear,
- Generator, motioned, turns mechanical energy into electricity that goes to on grid installation or is directly consumed by the user.
Ways of fixing wind turbines
There are two solutions of exploiting the clean generated energy. Installation working with electricity network is called on-grid solution. Such solution is applied when the turbine’s owner is a prosumer i.e. they equally consume generated energy and its excess is sold to the energy grid. Another way of electrical network is a solution called off-grid. It is an RES installation not connected to the network and its energy is exploited for own purposes, mainly in the form of additional heating up to the building or running water. Also, there are off-grid installations where energy is stored in cells in order to be exploited on demand (off-grid with storage).
There are several capacities but what is actually each of them?
In energy sector, capacity plays a crucial role. The same goes about RES. Aerodynamic capacity is exceptionally important in energy gain from the turbines. It is responsible for how well a given unit renews energy from wind. Maximum aerodynamic capacity possible to gain according to physics law is defined by Betz’s law and that is 59,3%. Turbine ALPHA 6 reaches 97% of Betz’s limit. More about Betz’s law You can read here.https://iwt-turbines.pl/step-3-aerodynamic-capacity/
Electrical capacity informs on what part of mechanical energy will be turned into electricity. Its remaining part is usually a loss in the form of heat coming from the turbine electrical system such as generator and inverter.
Total condition of the installation is received by multiplying aerodynamic capacity by electrical capacity. For example: 97% of aerodynamic capacity x 90% of electrical capacity = 87,3% total installation capacity (this part of energy was turned into electricity).
What is a difference between the power curve and capacity curve?
Power curve informs the relation of turbine power to wind speed, in other words with what power turbine will work with defined wind speeds.
Power curve is the most important information which the owner, interested in the turbine investment, should consider when making a decision as to its choice.
The curve of annual energy productivity depending on the average wind speed is not enough information and/or is basic information on which the owner should rely because it stems from the calculation based on power curve and so called Weibull distribution taking into account the values of distributors that are variable.
If the calculation assumes wrong distributors, productivity curve will be wrongly topped giving untrue values of energy production. Not accessing the power curve is a signal informing about doubtful reliability of turbine parameters.
Whereas (aerodynamic) capacity curve illustrates what aerodynamic capacity a turbine can reach for the particular speeds of wind.
Essential parameters describing wind turbine
– Cut In – wind speed that moves the turbine.
– Electrical Cut In – wind speed initiating energy production.
– Cut out – wind speed causing the halt and switching off the turbine.
– Rated Wind Speed – wind speed at which the turbine reaches maximum power.
– Rated Rotational Speed – maximum rotation speed of the rotor.
– Rated Power – maximum turbine power.
– Intersection space of wind turbines – working space is the intersection of the whole turbine horizontal to airflow direction. The bigger working space, the more power a turbine can generate. It is worth noting that for the standard wind turbines of horizontal rotation rotor axis the space is equal to the space of circle marked by the blade ends (rotator diameter).
The working space of vertical wind turbines is marked by the rectangle space which height results from the length of the blades and the width from rotator diameter. If the vertical or horizontal wind turbine uses the diffuser that is bigger than the rotator then the working space is marked by the diffuser. The working space is always marked by the dimensions of the biggest turbine element. This is important as calculating the turbine capacity (particularly diffuser ones) should be done basing on the maximum working space calculated in the way as described above. In the situation where the capacity of diffuser turbine is calculated on the basis of mere rotator and not the space of the diffuser (bigger one) then there appears wrong over ration of wind turbine capacity, which in extreme cases can lead to the situation of going beyond the Betz’s limit breaking the laws of physics. In reality, it is not possible and it results only from wrong calculation of working space.
– Types of generators – in wind turbines there are different types of generators. Mainly, they are divided into PMG generators (Permanent Magnet Generator) and coil generators. PMG are the generators where the excitation field is based on the magnets that when rotating inside the generator generate electricity. Their advantage is high capacity and reliability. They do not need external supply to operate. The coil generators are generators in which the magnet role is taken by the coil being the magnet. The disadvantage of coil generators is the necessity of powering the electro magnets which requires the energy, and this results in lower capacity but at the same time it is a more faulty solution and requires frequent service.
– Types of drives – turbine rotor can be connected to the generator in two ways. Directly and by the shaft. Direct solution (so called Direct Drive) is less faulty however it requires a bigger generator which results from the fact that it operates at lower rotation speeds. The drive using the shaft allows to use smaller generator because it will operate at higher rotation speed. Unfortunately, the shaft is a mechanical component and is heavily exploited during its operation. This results in frequent service or examinations and eventually in exchange.
When deciding on shaft or/and coil generator we talk about the illusionary saving. It results from much lower purchase price however not including the costs of after-sales service and the halts of turbine operation. The best turbines in the world use PMG generators connected directly with the rotor shaft (Direct Drive).
– Blade pitch control – there are two ways of controlling the blade pitch – active and passive. Active system allows to any change in the blade pitch at any moment of turbine operation. However passive system changes the blade pitch depending on the rotation speed, usually acting as the protection against exceeding maximum rotation speed.
– Turbine yaw control – alike in case of blade angle change, there are two ways of adjusting the turbine to wind direction – active and passive. Standard wind turbines require active system of adjusting rotor at wind direction, which is usually done by the gear wheel that is moved by the engine in order to adjust the unit according to wind direction. Some small turbines of horizontal rotor axis have behind the rotor a flat wing (tail) that allows the unit to adjust in a passive way not using the gear that, in turn, requires power supply. It is important to note that the vertical turbines do not require any adjustment according to the wind due to their construction. In a diffuser turbine it can be the diffuser to take the role of the mentioned above wing (tail). Passive system guarantees reliable work and there is no need of power supply to feed the system that adjusts the unit according to wind.
Three steps to become an aware RES user
You have just taken the first and the most important step. You do know a lot now. A question is: do You want to go further in? Here are two following steps. Are You curious how You are going to perceive the world when You continue?
Step 2: Potential of Your location
Step 3: Aerodynamic capacity
We would like RES glossary to be constantly expanded. If You feel a term is missing or some terms are not clear, do feedback us on it in Your comment. We shall definitely explain them.
The awareness connected with RES constantly increases. Do You really know everything? You can actually check it. We prepared a glossary that should be known to all fans of clean energy. This is the first step to become the aware user of RES.
Welcome to RES world.
Quite often we come across the term RES (Polish OZE) and it stands for Renewable Energy Sources. They are called so as they include the sources which exploitation excludes long lasting loss. Their resources simply renew themselves in a very short period of time. These are, among others: wind, rain, tides, sea waves, sunlight and geothermal energy. Contradictory to RES are non-renewable energy sources such as coal, natural gas or uranium.
Solar collectors, photovoltaic cells. Is there any difference?
Many people confuse solar collectors with photovoltaic cells for one simple reason. Both are fixed mainly on the roofs and after installation they actually look alike. However they differ with one basic thing. Solar collectors generate heat. Whereas photovoltaic cells generate electricity that can be used to heat up the houses. Solar collectors come with several solutions, e.g. flat, vacuum tube, vacuum flat. They differ with capacity, way of gaining energy and installation cost.
Photovoltaic cells, alike solar collectors, base their operation on sunlight. However, in this case the result of gained energy is electricity, not the heat. In case of photovoltaic cells gathered power can be turned into energy to heat and power the electric devices. Solar collectors allow to receive only the thermal energy. That is one of the reasons for which the photovoltaic cells are more expensive.
Heat and electricity from wind instead the sun
Wind is also one of the Renewable Energy Sources. Wind turbines are responsible for collecting the energy and they characterise with various features. Before we discuss them, let us explain what exactly wind turbine is.
Wind turbine is a tool that processes the kinetic wind energy (airflow) for the mechanical movement of rotor work that is turned into electricity.
We differentiate two types of turbines in terms of axis rotation.
- Turbine of vertical axis.
- Turbine of horizontal axis.
Both types may also come with a diffuser version. The diffuser helps to better the efficiency.
Horizontal turbines are divided into two types due to direction of air inflow:
- up-wind.
- down-wind.
Turbines of horizontal axis rotation are also divided due to the number of blades:
- single blade,
- double blade,
- three blade,
- multi blade.
How is the electricity made out of wind?
- Wind faces the resistance in the form of a turbine blade,
- Airflow (kinetic energy) is processed into mechanical energy – rotor movement,
- Rotor axis is connected with a generator in a direct way or by a gear,
- Generator, motioned, turns mechanical energy into electricity that goes to on grid installation or is directly consumed by the user.
Ways of fixing wind turbines
There are two solutions of exploiting the clean generated energy. Installation working with electricity network is called on-grid solution. Such solution is applied when the turbine’s owner is a prosumer i.e. they equally consume generated energy and its excess is sold to the energy grid. Another way of electrical network is a solution called off-grid. It is an RES installation not connected to the network and its energy is exploited for own purposes, mainly in the form of additional heating up to the building or running water. Also, there are off-grid installations where energy is stored in cells in order to be exploited on demand (off-grid with storage).
There are several capacities but what is actually each of them?
In energy sector, capacity plays a crucial role. The same goes about RES. Aerodynamic capacity is exceptionally important in energy gain from the turbines. It is responsible for how well a given unit renews energy from wind. Maximum aerodynamic capacity possible to gain according to physics law is defined by Betz’s law and that is 59,3%. Turbine ALPHA 6 reaches 97% of Betz’s limit. More about Betz’s law You can read here.https://iwt-turbines.pl/step-3-aerodynamic-capacity/
Electrical capacity informs on what part of mechanical energy will be turned into electricity. Its remaining part is usually a loss in the form of heat coming from the turbine electrical system such as generator and inverter.
Total condition of the installation is received by multiplying aerodynamic capacity by electrical capacity. For example: 97% of aerodynamic capacity x 90% of electrical capacity = 87,3% total installation capacity (this part of energy was turned into electricity).
What is a difference between the power curve and capacity curve?
Power curve informs the relation of turbine power to wind speed, in other words with what power turbine will work with defined wind speeds.
Power curve is the most important information which the owner, interested in the turbine investment, should consider when making a decision as to its choice.
The curve of annual energy productivity depending on the average wind speed is not enough information and/or is basic information on which the owner should rely because it stems from the calculation based on power curve and so called Weibull distribution taking into account the values of distributors that are variable.
If the calculation assumes wrong distributors, productivity curve will be wrongly topped giving untrue values of energy production. Not accessing the power curve is a signal informing about doubtful reliability of turbine parameters.
Whereas (aerodynamic) capacity curve illustrates what aerodynamic capacity a turbine can reach for the particular speeds of wind.
Essential parameters describing wind turbine
– Cut In – wind speed that moves the turbine.
– Electrical Cut In – wind speed initiating energy production.
– Cut out – wind speed causing the halt and switching off the turbine.
– Rated Wind Speed – wind speed at which the turbine reaches maximum power.
– Rated Rotational Speed – maximum rotation speed of the rotor.
– Rated Power – maximum turbine power.
– Intersection space of wind turbines – working space is the intersection of the whole turbine horizontal to airflow direction. The bigger working space, the more power a turbine can generate. It is worth noting that for the standard wind turbines of horizontal rotation rotor axis the space is equal to the space of circle marked by the blade ends (rotator diameter).
The working space of vertical wind turbines is marked by the rectangle space which height results from the length of the blades and the width from rotator diameter. If the vertical or horizontal wind turbine uses the diffuser that is bigger than the rotator then the working space is marked by the diffuser. The working space is always marked by the dimensions of the biggest turbine element. This is important as calculating the turbine capacity (particularly diffuser ones) should be done basing on the maximum working space calculated in the way as described above. In the situation where the capacity of diffuser turbine is calculated on the basis of mere rotator and not the space of the diffuser (bigger one) then there appears wrong over ration of wind turbine capacity, which in extreme cases can lead to the situation of going beyond the Betz’s limit breaking the laws of physics. In reality, it is not possible and it results only from wrong calculation of working space.
– Types of generators – in wind turbines there are different types of generators. Mainly, they are divided into PMG generators (Permanent Magnet Generator) and coil generators. PMG are the generators where the excitation field is based on the magnets that when rotating inside the generator generate electricity. Their advantage is high capacity and reliability. They do not need external supply to operate. The coil generators are generators in which the magnet role is taken by the coil being the magnet. The disadvantage of coil generators is the necessity of powering the electro magnets which requires the energy, and this results in lower capacity but at the same time it is a more faulty solution and requires frequent service.
– Types of drives – turbine rotor can be connected to the generator in two ways. Directly and by the shaft. Direct solution (so called Direct Drive) is less faulty however it requires a bigger generator which results from the fact that it operates at lower rotation speeds. The drive using the shaft allows to use smaller generator because it will operate at higher rotation speed. Unfortunately, the shaft is a mechanical component and is heavily exploited during its operation. This results in frequent service or examinations and eventually in exchange.
When deciding on shaft or/and coil generator we talk about the illusionary saving. It results from much lower purchase price however not including the costs of after-sales service and the halts of turbine operation. The best turbines in the world use PMG generators connected directly with the rotor shaft (Direct Drive).
– Blade pitch control – there are two ways of controlling the blade pitch – active and passive. Active system allows to any change in the blade pitch at any moment of turbine operation. However passive system changes the blade pitch depending on the rotation speed, usually acting as the protection against exceeding maximum rotation speed.
– Turbine yaw control – alike in case of blade angle change, there are two ways of adjusting the turbine to wind direction – active and passive. Standard wind turbines require active system of adjusting rotor at wind direction, which is usually done by the gear wheel that is moved by the engine in order to adjust the unit according to wind direction. Some small turbines of horizontal rotor axis have behind the rotor a flat wing (tail) that allows the unit to adjust in a passive way not using the gear that, in turn, requires power supply. It is important to note that the vertical turbines do not require any adjustment according to the wind due to their construction. In a diffuser turbine it can be the diffuser to take the role of the mentioned above wing (tail). Passive system guarantees reliable work and there is no need of power supply to feed the system that adjusts the unit according to wind.
Three steps to become an aware RES user
You have just taken the first and the most important step. You do know a lot now. A question is: do You want to go further in? Here are two following steps. Are You curious how You are going to perceive the world when You continue?
Step 2: Potential of Your location
Step 3: Aerodynamic capacity
We would like RES glossary to be constantly expanded. If You feel a term is missing or some terms are not clear, do feedback us on it in Your comment. We shall definitely explain them.