Monthly Archives: July 2023

Making new friends: grid friendly wind turbines

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Renewable energy is revolutionizing the global power sector, with wind energy emerging as a key player in the transition towards a sustainable future.

Wind farms, harnessing the immense power of nature, are sprouting across landscapes, powering homes and industries while reducing carbon emissions.

In this website we explored the advancements in wind farm engineering and construction, discussing what is driving efficiency, reliability, and sustainability in the industry.

Through the years we have explored some of the clearest trends in the industry: larger turbines with increased efficiency (capacities exceeding 5 megawatts have become increasingly common, thanks to advancements in rotor design, materials, and control systems), higher towers, use of digitalization and algorithms to optimize operations, improve maintenance strategies, and enhance overall performance (today, in 2023, they would probably call it “Artificial Intelligence”, since the term seems to be very fashionable these days).

One more trend in the industry is the appearance of “grid friendly wind turbines”.

The term refers to turbines that have a number of desirable characteristics from the point of view of the electric grid to which they connect.

To enhance grid integration, wind turbines are being equipped with advanced control systems that enable them to actively support the stability of the power grid.

In practice, these grid-friendly turbines can interact with the grid and actively respond to grid signals or specific grid conditions to regulate their power output accordingly.

For example, they can provide frequency regulation services by ramping up or down their power output to help balance grid frequency.

By providing grid support services, wind turbines contribute to a more stable and reliable grid operation.

Grid-friendly turbines are typically equipped with communication interfaces that allow them to exchange information in real time with grid operators.

This communication facilitates coordination between the turbine's behaviour and the overall grid situation.

Grid-friendly turbines are designed to meet country specific "grid codes" and regulations established by grid operators or other local authorities.

These codes define the exact requirements and performance criteria for wind turbines.

Turbine manufacturers ensure that their grid-friendly models comply with these codes to support seamless integration with the grid.

Some key features and capabilities of grid-friendly turbines include:

Frequency Regulation

Frequency regulation is an important aspect of grid operation, ensuring the balance between electricity generation and demand to maintain a stable grid frequency.

Grid-friendly turbines can adjust their power output quickly in response to frequency fluctuations on the grid.

When there is an imbalance between electricity supply and demand, these turbines can ramp up or down their power generation to help stabilize the grid frequency.

By actively participating in frequency regulation, wind turbines contribute to maintaining the overall stability of the power system.

The first step is a continuous grid frequency monitoring: grid-friendly turbines continuously monitor the grid frequency.

The standard frequency for most power grids is 50 Hz (for instance in Europe) or 60 Hz (standard in the US).

Turbines measure the instantaneous frequency of the grid and compare it to the nominal frequency.

Frequency deviations can occur due to several reasons, such as changes in electricity demand, sudden power generation fluctuations, or other grid disturbances.

If the grid frequency deviates from the nominal frequency, grid-friendly turbines detect the problem.

If there is a frequency deviation, the control system of a grid-friendly turbine initiates a response. The response is typically based on pre-programmed control algorithms designed to stabilize the grid frequency.

To support frequency regulation, the grid-friendly turbine adjusts its power output.

In response to a frequency drop below the nominal value, the turbine increases its power generation. Conversely, if the frequency rises above the nominal value, the turbine reduces its power output.

By adjusting their power output in response to frequency deviations, grid-friendly turbines provide an important ancillary service to the grid.

By actively participating in frequency regulation, grid-friendly turbines help mitigate frequency deviations, which, if left unaddressed, can lead to instability and potential power outages. Their responsive power adjustment helps maintain the grid frequency within the acceptable operating range, ensuring the reliable operation of the power system.

Voltage Control

Turbines with voltage control capabilities can adjust their reactive power output to regulate voltage levels within acceptable limits.

This functionality ensures that wind farms can actively support grid voltage stability and maintain the quality of electricity supply.

Grid Fault Ride-Through:

Grid-friendly turbines are designed to ride through grid faults without disconnecting from the grid. During temporary faults or disturbances, the turbines continue to operate and provide power to the grid, minimizing the impact of grid events on the overall system stability.

"Fault ride-through capabilities" refer to the ability of a wind turbine to remain connected to the power grid and continue operating during temporary disturbances or faults in the grid. When a fault or disturbance occurs in the grid, such as a short circuit or voltage dip, the grid voltage and frequency may deviate from their normal levels. Wind turbines with fault ride-through capabilities are designed to withstand and ride through these grid faults without disconnecting from the grid.

During a fault, the fault ride-through capability allows the wind turbine to continue generating power and injecting it into the grid. This is crucial for maintaining grid stability and minimizing disruptions in the overall power system. By remaining connected and operational during fault conditions, wind turbines with fault ride-through capabilities contribute to the reliable operation of the grid and help prevent widespread power outages.

The exact behavior of a wind turbine with fault ride-through capabilities can vary depending on specific grid codes, standards, and turbine designs. Some common features or responses of turbines with fault ride-through capabilities include:

Low Voltage Ride-Through (LVRT): Wind turbines may be equipped with LVRT functionality, which enables them to continue operating even when the grid voltage drops below a certain threshold. The turbine adjusts its reactive power output to support grid voltage stability during low voltage events.

Fault Clearing and Resynchronization: After a fault is cleared, wind turbines with fault ride-through capabilities synchronize their operation with the grid by resuming normal grid voltage and frequency conditions. This allows the turbine to smoothly reconnect and continue its power generation.

Fault Detection and Monitoring: Turbines with fault ride-through capabilities are equipped with monitoring and detection systems that identify grid faults and assess their severity. These systems enable the turbine to respond appropriately and take necessary actions to ride through the fault safely.

By maintaining operation during fault conditions, wind turbines with fault ride-through capabilities contribute to the reliability and stability of the power grid. They help ensure a smooth integration of wind power into the grid and minimize disturbances that could otherwise impact the overall power system.

It's important to note that the specific fault ride-through capabilities of a wind turbine can vary depending on turbine technology, grid requirements, and regional regulations. Turbine manufacturers typically provide detailed specifications and compliance information regarding fault ride-through capabilities for their turbine models.

Power Smoothing

Some turbines feature advanced power control mechanisms that smooth out fluctuations in power output caused by wind speed variations.

This helps reduce the rapid changes in generation, known as "ramp rates," and makes wind power more predictable and easier to integrate into the grid.

By incorporating these grid-friendly features, wind turbines can actively contribute to the stability and reliability of the power grid. They enable smoother integration of wind power and enhance the ability of grid operators to manage grid conditions and maintain a balanced electricity supply-demand relationship.

Grid-friendly turbines can contribute to the efficient integration of wind power into the grid, ensuring grid stability, and maximizing the utilization of renewable energy resources

Pandemic, war, inflation & Balance of Plant

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What were the consequences of the pandemic and the war in Ukraine on balance of plant (BoP) prices?

If you are reading this article, you probably know that the Balance of Plant (BoP) refers to all civil and electrical works necessary for the operation of a wind farm, excluding the turbines.

The BoP will therefore include elements such as roads, foundations, electrical cables, fibre optics, etc.

It is impossible to underestimate the effects of pandemic and war in Europe on wind farm infrastructure costs.

The cost structure of BoP varies depending on project characteristics.

For example, some wind farms connect to existing substations (or even in medium voltage), while others have to build a dedicated substation to evacuate the energy produced.

In some states, the electricity grid operator may oblige the project developer to also build an additional substation, that will be integrated into the existing grid. This is obviously a very onerous obligation, which may make the project economically unfeasible.

In terms of civil works, the scope of the project may also be very different: a 10-turbine wind farm built on top of a mountain (where the rock normally emerges after a few metres of excavation) will have significantly cheaper foundations than a wind farm in a valley near a river, where clay and other soft soil accumulated through the years and it will be necessary to use deep pile foundations.

The same wind farm in the lowlands, however, will perhaps be realised with cheaper roads (since it is a flat area), while its counterpart in the mountains may need massive earthworks.

Projects often also include the construction of one or more buildings for the control of the substation, the wind farm and the maintenance of the turbines.

These three activities can be carried out in a single building, although it is more common for the buildings to be physically separated. The reason for the separation is that the activities are carried out by personnel from different companies (the grid operator, the company that owns the wind farm, and the company that maintains the turbines, respectively).

Finally, as far as the medium voltage network is concerned, cables are normally underground, although in some cases overhead lines (which are normally cheaper) can be used.

To sum up, it is impossible to generalise and define a standard cost structure.

However, it is possible to identify the most frequent cost drivers and to discuss their evolution in recent years.

For civil works, these are usually concrete, iron, earthworks and buildings.

For electrical works, the main costs are generated by medium voltage cables, the transformer and other substation equipment.

How have prices evolved in recent years?

Steel prices rose rapidly in the post-Covid phase.

Steel and copper price evolution (https://tradingeconomics.com/commodity/steel)

The Russian invasion of Ukraine exacerbated the situation: a significant amount of the steel used in Europe was in fact produced in Ukraine (the name Azovstal probably rings a bell).

In the first half of 2022 it was very difficult to find construction steel. Now the situation seems to be slowly improving, but I suspect it will be difficult to return to pre-Covid prices (if only because high inflation has developed in the meantime.

Copper, used in cables and for grounding turbines, has also followed a similar trend as steel.

Cement, a key component of concrete, has followed a similar evolution. An important part of the price increase is concentrated in the last two years, after a period of relative stability between 208 and 2014 and a slow increase between 2015 and 2021.

As a result, the cost of concrete has continued to rise - in mid-2023, as I am writing this article, it does not appear to have started to fall as the price of steel has.

Cement index - last 20 years (St. Louis Fed)

Even a material with as little appeal as ordinary building bricks has risen by around 20 per cent in the last two years, and the price - despite rumours of a recession - does not seem to be stabilising.

Finally, the substation transformer(s). These elements, in addition to having experienced a comparable price increase with the other BoP elements, also have significantly longer manufacturing times than they used to have a few years ago. In some cases, they can go so far as to make the realisation of the project in a reasonable time extremely problematic.