Dynamic photovoltaic curtailment is an increasingly used method for managing solar energy production. It essentially involves controlling the amount of electricity your installation can feed back into the grid. Sometimes, this is necessary to comply with regulations or to optimise the use of your own production. We’ll look together at how it works and why it’s important to understand it all.
Key Takeaways
- Photovoltaic curtailment, often dynamic, adjusts the injected power to avoid exceeding set limits, directly impacting module efficiency.
- Several strategies exist to limit injection, ranging from dynamic curtailment linked to self-consumption to specific limitation devices.
- Inverter undersizing is a common approach to optimise curtailment, with recommendations varying according to geographical location and requirements such as reactive power absorption.
- Production losses due to curtailment are generally low, often less than 1% even for significant limitations, which is often offset by benefits to the grid.
- Tools like PVGis allow for simulating and estimating production losses related to curtailment, offering methods for precise evaluation even without specialised software.
Understanding the Phenomenon of Photovoltaic Curtailment
Photovoltaic curtailment, also known as clipping, is a practice that involves limiting the maximum power a solar installation can inject into the electricity grid. This occurs when the electricity production from solar panels exceeds a certain threshold, often defined by the inverter or by grid constraints. The objective is to manage the balance between electricity production and demand in real-time.
Definition of Curtailment and its Impact on Production
Curtailment manifests as a voluntary reduction in the production of a photovoltaic installation. Specifically, even if sunlight conditions are optimal and the panels have the potential to produce a certain amount of energy, the inverter will adjust its parameters to limit this production. This means that at a given level of sunlight, the installation will produce less electricity than it could theoretically supply. The direct impact is a decrease in the overall efficiency of the installation, as a portion of the potentially available energy is not utilised.
The Role of the Inverter in Optimisation and Curtailment
The inverter is the brain of the photovoltaic installation. Its primary function is to convert the direct current produced by the panels into alternating current usable by the grid or household appliances. To do this, it uses algorithms, such as MPPT (Maximum Power Point Tracker), to find the optimal operating point of the panels and thus maximise production. However, the inverter is also the tool that enables curtailment. By modifying the voltage of the modules, it can voluntarily move away from the maximum power point, leading to a controlled reduction in production.
Consequences of a Voluntary Decrease in Module Efficiency
When curtailment is implemented, a decrease in the efficiency of photovoltaic modules is accepted. This may seem counter-intuitive, but this strategy is often adopted for economic or technical reasons. For example, it can help comply with injection limits imposed by the grid operator, avoid penalties, or better adapt production to actual consumption needs or grid capacities. It is important to note that this production reduction is generally small, especially if the curtailment is well calibrated, and can be offset by other benefits, such as reduced connection costs or better grid integration.
Different Strategies for Limiting Injected Power
Given the constraints of the electricity grid, several approaches allow for managing the power injected by photovoltaic installations. These strategies aim to adapt production to the grid’s hosting capacity or to specific self-consumption needs, while minimising production losses.
Dynamic Injection Limitation for Self-Consumption
In the context of self-consumption, the injected power can be adjusted in real-time according to household consumption. The objective is to maximise the use of locally produced solar energy. If production exceeds instantaneous consumption, the surplus can be injected into the grid, but only up to the declared connection capacity. This dynamic management helps avoid overruns and optimises self-consumption. It is possible to limit injection by reducing the project’s peak power or by adjusting the inverter power, either statically or dynamically.
Injection Limitation Devices and Dynamic Curtailment
Dynamic curtailment, often implemented via injection limitation devices, adjusts the inverter’s output power to match consumption needs or grid-imposed limits. This can be done by configuring the inverter never to exceed a certain power, whether as a percentage of its nominal capacity or a fixed kilowatt value. For example, an 80% peak power limitation in the South of France results in only a minimal annual production loss, often less than 1%. This approach is common in some countries, such as Germany, where limiting injection to 70% of peak power is a widespread practice to preserve grid capacity.
Declared Connection Capacity and Installed Power
The declared connection capacity represents the maximum power limit that the installation is authorised to inject into the public grid. It may be lower than the installed peak power of the photovoltaic panels. In this case, the difference between the installed power and the connection capacity constitutes a margin that can be managed. It is possible to reduce this margin by decreasing the project’s peak power, by undersizing the inverters, or by using energy management systems for self-consumption. The choice of connection capacity has a direct impact on connection costs and the preservation of grid capacity, thus offering economic benefits for both the producer and the community. It is important to choose your connection capacity carefully to optimise your installation Test my connection online.
Here is a table illustrating the impact of a limitation on annual production loss:
| Geographical Location | Peak Power Limitation | Estimated Annual Production Loss |
|---|---|---|
| South of France | 80% | < 1% |
| South of France | 70% | < 3% |
| North of Lyon | 80% | Almost zero |
| North of Lyon | 70% | ~ 1% |
Limiting injected power, although it potentially reduces instantaneous production, is a key strategy for adapting to grid constraints and optimising the use of existing infrastructure. Associated production losses are often small compared to the overall benefits in terms of grid stability and connection costs.
Optimising Inverter Sizing
Choosing the right size for your inverter is a key step to maximise the profitability of your solar installation. It’s not simply about taking the maximum power your panels can produce. In fact, a slight undersizing of the inverter relative to the peak power of the modules can prove beneficial.
Benefits of Inverter Undersizing
The sun in France is not always at its zenith, and panels therefore rarely produce their theoretical maximum power. By adjusting the inverter’s power to be slightly lower than the total peak power of the panels (often between 90% and 95%), several advantages can be gained. This prevents the inverter from constantly operating at its capacity limit during peak sunlight, which can improve its longevity and overall efficiency. Furthermore, this can impact connection costs and grid capacity management. It is important to understand how to size your installation to optimise profitability [c75d].
Recommended Sizing Based on Geographical Location
Sunlight varies considerably by region. In the South of France, where sunlight is more generous, inverter undersizing can lead to minimal annual production losses, often less than 1% even with curtailment at 80% of peak power. In more northern regions, these losses are even lower, or even negligible for such a setting. It is therefore necessary to adapt the sizing to your location to find the right balance between maximum production and potential constraints.
Impact of Reactive Power Absorption on Sizing
Since early 2023, new regulations impose a reactive power absorption setpoint (tan(phi) = 0.35) for new connection requests. This measure aims to improve the hosting capacity of the low-voltage grid. While it potentially allows for connecting more power for a given cost, it can also influence inverter sizing. Significant inverter undersizing (for example, at 50% of peak power) could lead to production losses of up to 2% due to this setpoint. It is therefore necessary to consider this aspect for optimal sizing, ensuring that the inverter is configured to correctly manage this reactive power absorption [a69e].
It is possible to limit the injected power by adjusting the inverter power, either permanently or dynamically. This limitation, often called curtailment, can reduce connection costs and help preserve the capacity of the public grid. However, it is necessary to precisely evaluate the production losses caused by these limitations to ensure that the economic gain is real.
Here is a table illustrating the potential impact of production losses according to the level of undersizing and location:
| Location | Undersizing | Estimated Annual Losses |
|---|---|---|
| South of France | 80% of peak power | < 1% |
| South of France | 70% of peak power | < 3% |
| North of Lyon | 80% of peak power | Almost zero |
| North of Lyon | 70% of peak power | ~ 1% |
Evaluating Production Losses Related to Curtailment
Photovoltaic production curtailment, while useful for adapting to grid constraints, inevitably leads to a reduction in energy produced. It is therefore relevant to precisely evaluate these losses to understand the real impact on the profitability of an installation. These losses depend on several factors, including the level of limitation applied and the geographical location of the installation. A detailed analysis makes it possible to find the right balance between grid constraints and optimal production.
Estimating Annual Losses for Different Curtailment Levels
The annual production loss due to curtailment is generally low, especially when the limitation remains reasonable. For example, an 80% peak power limitation often results in a loss of less than 1% over the year, particularly in the sunniest regions of the South of France. In the North, this loss can be almost zero for 80% curtailment and around 1% for 70% curtailment. These figures show that the impact on overall production is limited compared to the potential benefits for electricity grid stability, as demonstrated by the German example where a 70% limitation is common to preserve grid hosting capacity.
Analysis of the Impact of Curtailment on Hourly Production
To visualise the effect of curtailment on production, monotonic power curves can be used. These graphs rank the hourly production of the installation in descending order. The area under this curve represents the total production. If curtailment is applied, a portion of this area is cut off. For example, 70% peak power curtailment will reduce the area corresponding to hours when production exceeds this threshold. Analysis of these curves shows that production rarely exceeds 80% of peak power, making losses related to moderate curtailment relatively low. The area corresponding to losses (in red in a typical simulation) is often minimal compared to the total area.
Comparison of Losses with Grid Capacity Gains
It is essential to put the production losses caused by curtailment into perspective with the benefits it provides to the electricity grid. By limiting the injected power, we contribute to the overall stability of the electrical system, thus avoiding potential overloads. For example, the European grid’s capacity is designed to withstand the loss of its two largest generation units, an effort in which France participates. Curtailment allows for better management of renewable energy intermittency and optimises the use of existing infrastructure. Production losses, often less than a few percent, are therefore an acceptable compromise to guarantee the reliability of electricity supply for all. This can also positively influence the connection cost.
| Curtailment Level | Estimated Annual Loss (South France) | Estimated Annual Loss (North France) |
|---|---|---|
| 80% | < 1% | Almost zero |
| 70% | < 3% | ~ 1% |
| 50% | ~ 2% (with tan(phi)=0.35) | ~ 2% (with tan(phi)=0.35) |
Methodologies for Estimating Production Losses
To precisely evaluate the impact of curtailment on your photovoltaic production, several methodological approaches exist. These methods aim to quantify the reduction in energy injected into the grid following a voluntary power limitation.
Using the PVGis Tool for Modelling
The PVGis tool, developed by the European Commission, is a free and powerful resource for simulating the production of a solar installation. It allows for obtaining hourly time-step production data, which is essential for analysing the effects of curtailment. Here are the key steps to use it for this purpose:
- Location and Parameterisation: Precisely identify your installation site on the map and enter your system’s characteristics: peak power, panel tilt, and orientation.
- Hourly Data: Select the option to obtain hourly production data and choose the simulation period (e.g., several years for a representative analysis).
- Data Download: Download the generated CSV file. This file contains the simulated hourly production of your installation without any limitation.
It is important to note that PVGis data is based on past weather conditions, thus offering a realistic estimate of potential production. For a more detailed analysis, it is often necessary to process this CSV file in a spreadsheet, adapting the number format if your software uses a comma as a decimal separator.
Hourly Time-Step Production Simulation
Once you have the hourly production data without curtailment, the next step is to simulate the impact of the limitation. This is done by adding a new column to your CSV file, representing the average hourly power with clipping.
The calculation for this new column is simple: for each hour, if the power produced without clipping is less than the defined curtailment power, the clipped power is equal to the power produced. Otherwise, it is limited to the curtailment value.
The formula can be expressed as: Clipped_Power = MIN(Power_without_Clipping, Curtailment_Power).
By summing the values in this new column over the entire simulated period, you obtain the total energy produced with curtailment. The ratio between this energy and the energy produced without curtailment will give you the annual percentage loss related to the limitation. A production loss of less than 1% is often observed for curtailment at 80% of peak power.
Alternative Method in the Absence of Professional Software
If you do not have specialised software for loss estimation, using PVGis combined with a spreadsheet remains the most accessible and reliable method. The hourly data provided by PVGis is sufficiently detailed to allow for precise simulation. Analysis of the monotonic power curve, which ranks hourly productions in descending order, can also offer a clear visualisation of the impact of curtailment. For example, it can be observed that the installation rarely produces beyond a certain threshold, making curtailment at this level not very penalising in terms of annual energy loss. To estimate your solar panel needs, you can use the basic formula: Pc = (Daily Consumption × 1) / (Minimum Sunlight × System Efficiency) [6aa2].
Setting Active Power Injection Limitations
Managing the power injected into the electricity grid is a key step for many photovoltaic installations. Setting these limitations allows for adapting to regulatory requirements and grid capacities, while optimising self-consumption. There are several ways to define these thresholds, either by a percentage of the nominal power or by a fixed value in kilowatts (kW).
Limitation Options by Percentage or Fixed Value
To configure the limitation of active power injected, several options are available. You can choose to limit injection to a certain percentage of your installation’s nominal power. For example, if your local grid requires a limit of 80% of the installed power, you can select this option and enter the corresponding value. Alternatively, a fixed kW value limitation can be applied, which is useful if a specific maximum power is required. In some cases, a 0% or 0 kW limitation, corresponding to ‘zero injection’, may be necessary. It is important to consult your grid operator’s specific requirements to choose the most appropriate setting. Once configured, this limitation usually appears as a dotted line on production graphs, facilitating visual monitoring.
Management of External Specifications and Priorities
It is also possible to configure the system to limit active power injection only when external specifications require it. These specifications can come from grid management systems, often via Ethernet communication. In this scenario, the system will take into account the most restrictive of the values provided by these external sources. This approach offers increased flexibility, as the limitation is only applied when strictly necessary, thus allowing production to be maximised when grid conditions permit. It is essential to ensure that the system is correctly configured to interpret these external signals in order to comply with the connection terms and conditions.
Consideration of Hybrid Inverters and Storage
For installations equipped with hybrid inverters or battery storage systems, additional configuration options are available. If the nominal power of the installation is set to a low level, it becomes possible to use surplus photovoltaic energy to charge the battery. This functionality optimises self-consumption and reduces surpluses injected into the grid. Virtual photovoltaic storage, for example, offers a flexible alternative to physical batteries for managing these surpluses, transforming injected electricity into energy credit usable later. This can contribute to greater energy independence and savings on energy bills.
The precise setting of injection limitations is the responsibility of the installation owner. It is advisable to verify the compliance of the parameters with the grid operator’s requirements and to ensure that the declared nominal power corresponds to the actual capacity of the installation. Incorrect configuration could lead to non-compliance or sub-optimal production.
The Role of Grid Operators in Dynamic Curtailment
Grid operators play a central role in the implementation and supervision of dynamic curtailment of photovoltaic production. Their main objective is to guarantee the stability and security of the electricity grid, by ensuring that the amount of electricity injected by solar installations remains within acceptable limits. This helps to avoid overloads and preserve existing infrastructure, while facilitating the integration of new renewable energy sources. They define the rules and thresholds to be respected by producers.
Grid Operator Requirements for Injection Limitation
Grid operators, such as Enedis in France, issue precise directives concerning the limitation of injected power. These requirements aim to maintain the balance between electricity supply and demand in real-time. They can vary depending on the installation’s capacity, its geographical location, and the state of the local grid. It is therefore imperative for photovoltaic installation owners to comply with these specifications to ensure compliant connection and operation.
- Definition of maximum power injection thresholds.
- Specification of accepted limitation methods (dynamic or static).
- Requirements for curtailment certificates for equipment.
Monitoring and Compliance with Prescribed Limits
Monitoring production and injection is an essential component of dynamic curtailment. Grid operators implement systems to continuously control the power injected by photovoltaic installations. Compliance with the set limits is verified, and penalties may be applied in case of non-compliance. This can include financial penalties or even the suspension of injection. Clear communication between the producer and the grid operator is necessary to adjust parameters if needed, for example by using tools like the Sunny Home Manager.
Adapting Production to Grid Needs
Dynamic curtailment provides valuable flexibility to adapt photovoltaic production to the fluctuating needs of the grid. When electricity demand is low or production from other sources is high, the grid operator may request a reduction in solar injection. Conversely, when demand is high, limitations can be eased as much as possible. This adjustment capability contributes to better overall energy management and optimisation of renewable resource utilisation.
The hosting capacity of the public electricity distribution network can be a limiting factor for connection. Limiting the connection capacity can reduce costs for the producer and preserve grid capacity for other projects.
Technical Considerations for Static Curtailment
Static curtailment of injected power represents a method where the production of a photovoltaic installation is voluntarily limited to a predefined level, regardless of sunlight conditions or grid demand. This technical approach is often implemented to comply with grid operator requirements or to optimise connection costs. It is important to fully understand the implications and prerequisites of this method for effective management of your installation.
Certificates Required for Static Curtailment
When a permanent limitation of injection is chosen, particularly through static inverter curtailment, supporting documents are generally requested by the connection authorities. If the nominal power of the inverter exceeds the declared connection capacity, a certificate from the inverter manufacturer is required. This document must confirm that the device is configured not to exceed the set limit. In cases where this certificate does not explicitly mention the curtailed power values, a sworn statement from the installer may be required. The latter attests to the installer’s commitment to respect the agreed injection limit, thus ensuring the installation’s compliance with grid specifications. It is advisable to consult the Enedis user manual for precise details on the forms to submit.
Permanent Inverter Curtailment
Permanent inverter curtailment involves configuring the equipment to limit its output power to a defined threshold, even if sunlight conditions would allow for higher production. This can be achieved in two main ways: either by selecting an inverter whose nominal power is lower than the peak power of the photovoltaic modules (undersizing), or by setting up a more powerful inverter so that it never exceeds a certain injected power value. This latter method is what is known as static curtailment. It ensures that the injected power remains within the limits accepted by the grid, thereby preserving hosting capacities and potentially reducing connection costs.
Connection Capacity Lower Than Inverter Power
It is entirely possible, and sometimes advantageous, to declare a connection capacity lower than the nominal power of the installed inverter. In this situation, the inverter must be configured to respect this injected power limit. For example, if you have a 10 kWp installation and choose to limit your connection capacity to 8 kW, your inverter will need to be set up never to inject more than 8 kW, even if the sun is shining brightly. This approach is often used to optimise connection costs, as tariffs can be indexed to the injected power. A simulation using tools like PVGis can help estimate the production losses associated with such curtailment, which are generally low, often less than 1% for 80% peak power curtailment in the South of France.
Impact of Curtailment on Connection Costs and Grid Utilisation
Reduction of Connection Costs by Power Limitation
Connection to the public electricity grid can represent a significant cost for photovoltaic installations. The grid’s hosting capacities are not infinite, and the higher the power you wish to inject, the more extensive, and therefore costly, the necessary connection work may be. By choosing to limit the declared connection capacity, it is often possible to significantly reduce these initial costs. This approach allows for adapting to local grid constraints while managing your investment budget. It is even possible to consult online tools to estimate the maximum injection power without encountering particular constraints, which can guide this decision Test my connection online.
Preservation of Public Grid Hosting Capacities
Beyond the direct economic benefits for the producer, limiting injected power has a positive impact on the entire electrical system. By reducing the maximum power your installation can feed back into the grid, you contribute to preserving available hosting capacities for other producers, whether residential or industrial. This is a form of sharing grid resources, particularly relevant in a context of increasing development of renewable energies. This approach helps maintain grid stability and reliability, by avoiding saturation during solar production peaks. Dynamic injection limitation, for example, allows for better management of these flows better grid management.
Economic Advantages of Curtailment for the Producer
The choice to limit connection capacity, whether statically or dynamically, can result in tangible financial benefits for the producer. In addition to the aforementioned reduction in connection costs, this strategy can also influence other economic aspects. For example, in some cases, an installation optimised for self-consumption without selling surplus can avoid complex administrative procedures and costs associated with electricity resale self-consumption without resale. Although this implies a reduction in potentially exportable production, the savings on initial costs and the simplification of management can make this option economically attractive, especially if on-site consumption is high.
Smart Energy Management with Sunny Home Manager
The Sunny Home Manager is a tool that helps you make better use of the electricity produced by your solar panels. It doesn’t just monitor what your installation produces, but it also tries to match this production with what your home consumes. The idea is to maximise self-consumption and reduce what is injected into the grid, especially if limitations are in place.
Monitoring Active Power Injection
The Sunny Home Manager continuously monitors the amount of electricity your photovoltaic installation sends to the public grid. If this amount exceeds a limit set by your grid operator, the system intervenes. It can ask the inverters to reduce their production to stay within the limits. This is a way to comply with regulations while producing as much as possible within the authorised limits. For example, if the limit is 70% of your installed power and your installation produces 90% thanks to good sunshine, but your home only consumes 20% of it, the Sunny Home Manager will reduce production to 80% so as not to exceed the 70% injection limit. This is fine-tuned management to avoid penalties or disconnections.
Optimising Household Load Consumption
What’s interesting is that the Sunny Home Manager doesn’t just reduce production. It can also control your electrical appliances. When there’s a lot of sunshine and your home consumes little, it can decide to start appliances like the washing machine or charge your electric car. The goal is to use this surplus solar energy for your household needs rather than injecting it into the grid. This allows you to increase your self-consumption rate and save money on your electricity bill. It tries to start these appliances when solar energy is abundant, so that panel production is not unnecessarily reduced.
Reducing Photovoltaic Production in Case of Exceedance
If, despite everything, solar production exceeds the authorised injection limit, the Sunny Home Manager will act on the inverters to reduce their power. It can even be configured for zero injection, meaning it blocks all injection into the public grid. It should be noted that certain inverters are necessary for this zero-reduction function to be possible, particularly those that support the automatic curtailment function. It is important to check the compatibility of your equipment and follow the manufacturer’s recommendations for optimal management. The system can be configured for a fixed limitation in kilowatts (kW) or as a percentage of your installation’s nominal power. In the event of external specifications, such as those from a grid operator, the system will take the most restrictive of the values to limit injection. It is essential to correctly declare the nominal power of your installation and to request authorisation from your grid operator before installing this type of injection management system. For more information on selling surplus electricity, you can consult the sale terms.
The Sunny Home Manager 2.0 is an example of a solution for smarter management of your solar energy, optimising both your production and consumption. It is a key element for maximising the use of solar energy produced at home, taking into account grid constraints and household needs. It’s a bit like having an orchestra conductor for your solar installation, ensuring everything works at its best. You can find out more about the Sunny Home Manager 2.0 and its features.
Discover how the Sunny Home Manager makes your home smarter by managing your energy. It’s like having a superhero for your electricity! Learn more about this technology and how it can help you save. Visit our website to find out how to make your home more energy-efficient today!
Conclusion
In summary, dynamic photovoltaic curtailment, although it may seem restrictive, offers notable advantages. It allows for optimising power injection in real-time, adapting to grid constraints and consumption needs. Simulations show that production losses related to these adjustments generally remain low, often less than 1% annually, especially when curtailment is set at 80% of peak power. This approach is a smart strategy for better managing electricity grid capacities and, potentially, reducing connection costs. It is therefore advisable to carefully study sizing and curtailment options to find the right balance between maximising production and respecting technical and economic constraints.
Frequently Asked Questions
What is photovoltaic curtailment and how does it work?
Curtailment is when your solar installation is asked to produce a little less than it could. Imagine your solar panels are like apples growing on a tree. Curtailment is like telling the tree not to ripen all the apples to their maximum, so there’s enough for everyone and the electricity grid isn’t overloaded. The inverter, which converts the current from the panels, helps to do this by adjusting the panels’ operation slightly.
Why is the power sent to the grid limited?
Sometimes, the electricity grid is like a road. If too many cars (electricity from the panels) arrive at the same time, it creates traffic jams. Limiting the power sent helps to avoid these traffic jams and ensures that the grid can manage all the electricity properly. It also helps to ensure that connecting your installation doesn’t cost too much.
Does curtailment cause a significant loss of electricity?
Generally, no. When power is limited to 80% of what the panels can produce, you lose barely 1% of all the electricity produced over the year. It’s like having 100 sweets and giving 1 to a friend; you still have 99 for yourself. The loss is really minimal compared to the help provided to the grid.
Can you choose to limit the power sent?
Yes, it’s possible! You can tell your installation not to send more than a certain number of kilowatts (kW) to the grid. You can choose a fixed limit, like ‘no more than 5 kW’, or say ‘no more than 80% of what I can produce’. It’s up to you, depending on what’s best for the grid and for you.
What is inverter undersizing?
This is when you choose an inverter that is slightly less powerful than the total power of your solar panels. For example, if your panels can produce 10 kW, you could choose an 8 kW inverter. This helps to avoid curtailment when there’s a lot of sunshine, as the inverter will naturally limit the power to 8 kW. It’s a way to manage the power sent.
How do I know how much power I can send to the grid?
To find this out, you can use online tools, such as PVGis, which is a free simulator. It tells you how much your installation will produce based on its location and the weather. You can also check the rules of your electricity supplier or grid operator for the limits.
Does curtailment affect self-consumption?
Curtailment limits the amount of electricity you can send to the grid. If you consume some of the electricity produced yourself (self-consumption), curtailment does not prevent you from doing so. It just ensures that you don’t send too much electricity to the grid, even if you produce a lot and don’t use it all.
Who decides the power limits to send to the grid?
It is the electricity grid operators, such as Enedis in France, who define these limits. They do this to ensure that the grid functions well and can accommodate electricity from all solar installations. They may request curtailment to avoid overloads.
