The article « On-demand generation: methods of injecting into the electricity grid » explores the various ways an energy generation facility, often photovoltaic, can be connected to the electricity grid. It addresses the technical, regulatory, and commercial aspects for those wishing to inject their output. It explains how to optimise this injection, whether it’s to sell all the energy produced, for self-consumption with the sale of surplus, or by integrating storage systems. The text aims to clarify the procedures and possible choices for efficient management of on-demand energy generation.

Key Takeaways

• Understand the basics of injecting energy into the electricity grid, including the components of an installation and the role of the inverter.
• Identify the different connection options based on the size of the installation (≤ 36 kVA or > 36 kVA) and the general conditions to be met.
• Explore strategies for selling generated electricity, such as total sale or self-consumption with sale of surplus.
• Evaluate the impact and benefits of battery storage systems in an on-demand generation approach.
• Familiarise yourself with connection and metering schemes, and injection methods for optimal generation management.

Fundamental principles of on-demand generation injected into the grid

On-demand generation, when connected to the electricity grid, represents a significant evolution in how we consume and produce energy. It’s no longer just about receiving electricity, but also actively participating in its supply. Understanding the basics of this interaction is therefore essential for anyone considering such an installation.

Understanding grid injection systems

Grid injection systems allow a local generation facility, such as solar photovoltaic panels, to send the electricity it generates back to the public distribution network. There are two main approaches: the total sale of electricity produced, where every watt generated is sold, and self-consumption, where one first consumes their own production and only the surplus is injected into the grid. This latter option is gaining popularity, particularly with the development of models such as collective self-consumption.

Essential components of a grid-connected photovoltaic installation

A typical photovoltaic installation intended for grid injection comprises several key elements:

• Solar panels: They capture sunlight and convert it into direct current.
• Mounting structure: This secures the panels, whether on a roof or on the ground.
• Inverter: This is the heart of the system, responsible for converting direct current into alternating current compatible with the grid.
• Protection boxes: These protect the installation against overvoltages and other electrical anomalies, on both the direct current (DC) and alternating current (AC) sides.

The role of the inverter in energy conversion and injection

The inverter plays a multifaceted role. Its primary function is to convert the electricity produced by the solar panels (direct current) into alternating current, which can be used by our appliances and is compatible with the electricity grid. But it does more than that. The inverter checks the quality of the grid (voltage and frequency) and only injects electricity when conditions comply with standards. It then synchronises its production with the grid, adjusting its voltage so that the electricity produced can actually be transmitted. In the event of a grid outage, a standard inverter stops its production for safety reasons. This is an important point to consider, especially if continuity of supply is a priority. The management of injected power can also be adjusted, for example, to limit injection and favour self-consumption, a strategy that optimises energy use while respecting grid capacities.

Connection to the public electricity grid implies an understanding of rules and contracts, particularly those related to network access tariffs, such as TURPE, which apply to installations injecting electricity.

Connection arrangements for on-demand generation

To inject the electricity you produce into the electricity grid, several options are available, depending mainly on the size of your installation. It is important to understand these arrangements to make the right choices.

For installations with a capacity of 36 kVA or less, connection is generally simplified. You have a choice of several injection modes:

• Total sale: All electricity produced is injected into the grid. You receive remuneration for this sold energy.
• Self-consumption with sale of surplus: You consume a portion of the electricity produced for your own needs, and the surplus is injected into the grid and sold.
• Self-consumption without sale: You consume all electricity produced, without injecting any into the grid. This option is less common for on-demand generation intended for sale.

The choice will depend on your consumption, your profitability objectives, and the configuration of your installation.

Above 36 kVA, the procedures and technical specificities of the connection become more significant. The process is often more complex and may require more in-depth technical studies.

The sales options (total or with surplus) remain similar, but contracts and tariffs may be negotiated differently. It is common for these installations to be intended for professional or industrial use, where energy management is more strategic.

Large-scale installations require rigorous planning and close coordination with the distribution network operator to ensure a safe and compliant connection.

Regardless of the size of your installation, certain general conditions apply for connection to the grid. These aim to ensure the stability and security of the electricity grid.

• Technical compliance: Your installation must comply with current technical standards to ensure quality current injection.
• Connection request: An official request must be submitted to the network operator (e.g., Enedis in France).
• Connection study: A study will be conducted to assess the impact of your installation on the grid and define the necessary works.
• Connection contract: A contract will be established, specifying the technical and financial terms of the connection.

Compliance with these conditions is essential to be able to inject your production into the grid.

Injection and sales strategies for generated electricity

Once your photovoltaic installation is connected to the grid, several options are available regarding how the generated electricity is managed and valued. The choice will depend on your objectives, whether they are economic, ecological, or related to your energy independence. It is important to understand these different strategies to optimise your project.

Sale of all electricity produced

This approach is the simplest to implement. All the electricity your solar panels generate is injected into the public distribution network. In return, you benefit from a guaranteed purchase tariff through a contract, often for a long duration. This offers clear financial visibility and a regular income, but you do not directly use the energy you produce. This is a solution that prioritises immediate financial profitability.

Self-consumption: consumption and sale of surplus

Self-consumption involves directly consuming part or all of the electricity you produce. Any energy not consumed instantly is then injected into the grid and sold. This strategy allows you to reduce your electricity bill by using your own production, while also valuing the surplus. It is part of an approach to achieve energy independence.

• Advantages: Reduced electricity bill, valorisation of surplus, contribution to the energy transition.
• Disadvantages: Requires a good match between your consumption profile and your production, may require a storage system to maximise self-consumption.

Combination of injection and sales modes

It is entirely possible to combine different strategies. For example, you can choose to consume part of your production (self-consumption) and sell the surplus. Another configuration might involve the total sale of your production while having another source of supply for your needs. Connection and metering schemes allow for the management of these complex configurations.

Here is an overview of possible configurations:

Injection type	Sales mode	Injection metering	Remote production metering
Total injection	Total sale	1	0
Surplus injection	Sale of surplus	1	1
No injection	No sale	0	0

The choice of injection and sales strategy has a direct impact on the profitability of your installation and your level of energy independence. It is advisable to carefully analyse your needs and objectives before making a decision.

Storage systems in on-demand generation systems

Advantages and disadvantages of battery storage systems

Integrating a battery storage system into an on-demand generation installation might seem an attractive solution for maximising the use of solar energy. These systems allow electricity produced during daylight hours to be stored for later use, for example, when the sun isn’t shining or demand is high. This can reduce reliance on the electricity grid and potentially lower electricity bills. However, less positive aspects must be considered. The initial investment for quality batteries is often substantial. Furthermore, batteries have a limited lifespan and eventually need to be replaced, which represents an additional cost and an environmental issue related to their recycling. It is important to weigh these elements before deciding.

• High acquisition cost
• Limited lifespan and replacement cost
• Environmental impact related to production and recycling
• Variable storage efficiency depending on technology

The hybrid inverter and its functionalities

The hybrid inverter is a central component in installations equipped with storage. It doesn’t just convert the direct current from solar panels into alternating current usable by household appliances. It also intelligently manages the flow of energy between the panels, batteries, the electricity grid, and domestic consumption. It can prioritise self-consumption, charge batteries with excess production, or inject this surplus into the grid if necessary. Some models even allow for load shedding in case of need. It’s somewhat the brain of the installation, optimising in real-time how energy is used or stored. Information on Battery Energy Storage Systems can be found to better understand their role in energy management.

Impact of storage on securing supply

One of the major benefits of a battery storage system is securing the electricity supply. In the event of a public grid outage, batteries can take over and continue to power essential household appliances. This avoids the inconvenience associated with power interruptions, such as refrigerators, heating systems, or computer equipment shutting down. For installations where continuity of supply is critical, storage provides significant peace of mind. It allows for a certain level of autonomy to be maintained, even when the main grid is unavailable. There are also virtual photovoltaic storage solutions that can offer an interesting alternative without requiring physical battery installation.

Connection and metering schemes for on-demand generation

To inject the electricity produced into the grid, several connection and metering schemes are possible. The choice will depend on the size of your installation, your sales and consumption objectives, as well as the technical specificities of your site. It is important to understand these configurations to optimise your production and profitability.

Injection, metering, and connection modes

Connection schemes are primarily defined by three aspects: the injection mode, the metering device, and the connection characteristics. These elements directly influence connection costs, in accordance with current tariffs. Generally, three injection options are distinguished:

• Total injection: All electricity produced is injected into the grid.
• Surplus injection: A portion of the electricity is consumed locally (self-consumption) and the rest is injected into the grid.
• Total self-consumption (no injection): All electricity produced is consumed on-site, nothing is injected into the grid.

Regarding metering, the deployment of the Linky meter has simplified certain configurations. For installations with surplus injection, the existing consumption meter is replaced by a Linky meter during connection. In the case of total injection, the consumption meter is only replaced during general deployment in the area. Access to daily metering data and load curves is possible via the Customer Area, provided the meter is configured in « producer mode ».

Connection schemes for small and large installations

Configurations vary depending on the power of the installation. For small installations (up to 36 kVA), schemes are often simpler. For example, if the installation is on a consuming building, consumption is measured by the existing meter, and a second meter can record the total production sold. For self-consumption with sale of surplus, the Linky meter allows both consumption and injection to be monitored.

For larger installations (above 36 kVA), schemes can be more complex. It is possible to combine different injection and sales modes. For example, one can choose to inject all production while only selling the surplus. In these cases, a meter can be placed closer to the installation for more precise measurement, as detailed in the dedicated Enedis note (Enedis-NOI-RES_46E). If you are a successful bidder in a « self-consumption » call for tenders, an additional meter will be installed to count the self-consumed portion and the associated premium. It is also possible to add a new installation to an existing production connection, with a meter dedicated to this new source. These configurations are governed by the connection conditions.

Metering of injection at the point of delivery

The point of delivery is where your installation is connected to the public distribution network. Metering of injection at this point is essential to precisely measure the electricity you send back to the grid. Depending on the chosen scheme, this metering can be carried out by a Linky meter or a dedicated production meter. For example, in a total injection scheme, a specific meter records all injected production. For surplus injection schemes, the Linky meter can manage both consumption and injection. The implementation of these devices is governed by contracts, notably the Connection Contract, which formalises the commitments between the parties.

Optimising capacity for on-demand generation

Differentiating peak power and connection capacity

When discussing capacity for a photovoltaic installation, it’s important to distinguish between two concepts: peak power and connection capacity. Peak power is the maximum power your panels can produce under ideal conditions (perfect sun, optimal temperature). It’s somewhat the theoretical potential of your installation. Connection capacity, on the other hand, is the power you declare and which is validated by the network operator. This capacity determines your contract and any connection fees. Choosing the right connection capacity is therefore a balancing act.

Identifying technical and regulatory thresholds

There are limits not to be exceeded. From a technical standpoint, the electricity grid has a reception capacity that can be limited, especially in certain areas. Regulations also set thresholds, particularly for small installations (up to 36 kVA) which often benefit from simplified procedures. Exceeding certain thresholds can imply additional constraints, such as more in-depth connection studies or limitations on injected power. One must also consider grid stability; for example, too rapid a variation in demand can affect the grid frequency, a parameter closely monitored by operators to maintain stability at 50 Hz [a940].

Strategies for optimising connection capacity

The goal is to find the right balance so as not to pay too much for an oversized connection, while making the most of your production. A common strategy is to limit the injected power. For example, one can choose not to inject 100% of the installation’s peak power, but rather 70% or 80%. This can reduce connection costs and simplify procedures, while minimising production losses, which often remain low (1 to 3%). This limitation can be dynamically managed by the inverter to adapt to grid constraints or local consumption [fbd6]. It is also possible to declare a connection capacity lower than the installation’s peak power for economic or regulatory reasons. It is important to carefully assess your needs and objectives to make the right choice. Sometimes, a capacity increase on an existing connection can be an option to consider if needs evolve.

Indirect connection and its implications

Understanding the general principle of indirect connection

Indirect connection, also known as grouped connection, is a technical solution that allows several electricity generation installations, often small-scale, to connect to the electricity grid via a single connection point. Instead of each installation having its own connection, they are all linked to the same injection point. This approach can simplify certain procedures and potentially reduce initial costs, particularly for projects that do not require a very high connection capacity. This connection mode is particularly relevant when installations are geographically close to each other. It involves centralised management of injection and metering at this common point.

Administrative procedures and associated costs

The procedures for an indirect connection can vary depending on the network operator and the specific configuration. Generally, a single request must be submitted for the common connection point, specifying the characteristics of each installation to be connected to it. Costs are distributed among the different users of the connection point. It is important to carefully study the distribution of costs, as it can influence the profitability of each individual project. The calculation of the reduction rate can also play a role in reducing connection costs for certain installations, according to current rules.

Specific cases of generation installations over 36 kVA

For installations with a capacity exceeding 36 kVA, indirect connection can become more complex. Although technically possible, it is often more common for these installations to have their own direct connection point to the grid. If an indirect connection is considered for an installation of this size, it must be ensured that the capacity of the common connection point is sufficient to accommodate the requested power, as well as that of other potentially connected installations. Regulatory and technical requirements may be stricter, requiring an in-depth study by the network operator. It is advisable to consult the specific conditions applicable to high-capacity installations for this type of connection.

Here is an overview of the elements to consider:

• Capacity of the common connection point: Must be sufficient for all installations.
• Safety study: A more in-depth analysis may be required to guarantee grid stability.
• Cost distribution: A clear agreement between parties is necessary.
• Regulatory compliance: Adherence to current standards for high-capacity installations.

Indirect connection requires precise coordination between the different stakeholders to ensure that the single connection point can support the total load and that administrative and financial aspects are clearly defined for each participant. Good planning is key to avoiding future complications.

Management of auxiliary consumption and simultaneous demands

Auxiliary consumption outside production periods

On-demand generation installations, particularly photovoltaic ones, do not produce electricity continuously. During periods when production is zero, such as at night or in low sunlight, the installation itself consumes energy for its own needs. This ‘auxiliary’ consumption concerns, for example, monitoring systems, inverter cooling fans, or management and communication systems. It is important to identify and quantify these for optimised overall energy balance management. This consumption can be covered by the public grid or by a stored energy source, depending on the system configuration. A good estimate allows for adjusting the connection capacity and avoiding unnecessary additional costs related to oversized production or storage capacity compared to actual needs. For a clear overview, it is sometimes necessary to install a dedicated meter for these auxiliaries, especially for larger installations. This allows for a precise distinction between the installation’s own consumption and that of connected buildings or equipment.

Simultaneous demand for production and consumption

Managing simultaneous demand is a key aspect of self-consumption. This refers to the situation where the installation produces electricity at the same time as connected buildings or equipment consume it. The objective is to maximise self-consumption by directly using electricity produced on-site. This reduces the amount of electricity to be purchased from the grid and allows for better valorisation of solar energy. In the context of collective self-consumption, several consumers can benefit from this shared local production. Coordination between production and consumption is therefore paramount. Intelligent management systems can help optimise this simultaneity by controlling certain appliances to operate when production is maximal. It is also possible to combine this strategy with a storage device to smooth out consumption peaks and production variations.

Capacity increase on an existing connection

Electricity needs sometimes evolve, requiring an increase in the capacity of the on-demand generation installation or the connection capacity. Whether it’s to add solar panels, install new consuming equipment, or simply to better manage demand peaks, a request for a capacity increase can be submitted to the network operator. The procedures and associated costs depend on the initial capacity and the desired capacity, as well as the technical specificities of the existing connection. It is often necessary to review the electrical installation, or even the point of delivery, to adapt to this new configuration. An in-depth study is generally required to assess feasibility and necessary modifications. A capacity increase can also impact electricity transmission tariffs. It is therefore advisable to anticipate these developments and inquire with the competent authorities about the exact procedures and any regulatory constraints. For example, in the context of collective self-consumption, the capacity increase must respect regulatory limits to continue benefiting from this organisational model.

Managing energy use for your secondary appliances and when multiple people demand energy simultaneously is important. This ensures everything runs smoothly without interruption. Want to know more about how to optimise your consumption? Visit our website to discover our solutions!

Highlight: Self-consumption and Storage

Conclusion

In summary, injecting electricity generation into the grid offers several options, each with its specific features. Whether for total sale, self-consumption with or without surplus, or even more complex systems integrating batteries for security, the choice will depend on individual needs and priorities. It is important to understand the different configurations and connection procedures, which have evolved over time. These systems, although sometimes complex to implement, pave the way for more autonomous energy management and active participation in the energy transition. It remains essential to stay informed about regulatory and technological developments to make the best choices.

Frequently Asked Questions

What is on-demand generation for the electricity grid?

It’s like having your own small electricity factory at home, for example with solar panels. When you produce more than you need, you can send the surplus to the general electricity grid for others to use. It’s a way of contributing to everyone’s electricity supply.

How does my solar electricity get onto the grid?

Your solar panels generate a special type of current, different from what comes into your home. A device called an ‘inverter’ converts this current so it’s compatible with the grid. Then, it’s sent directly into the public electricity lines.

Can I sell all the electricity I produce?

Yes, that’s an option! You can choose to sell everything your panels produce. It’s like being a small electricity supplier. Sometimes, it’s more financially beneficial than consuming your own electricity.

What is self-consumption?

Self-consumption is when you use the electricity you produce yourself. If you produce more than you consume at that moment, the surplus is sold to the grid. It’s a good way to be a bit more energy independent.

What are batteries for in a solar installation?

Batteries are like an energy reserve. They store electricity produced during the day so you can use it later, for example in the evening when there’s no sun. It can also help if the electricity grid has a temporary problem.

What’s the difference between a small and a large installation for connecting to the grid?

For small installations (up to 36 kVA, a measure of power), the procedures are often simpler. For larger ones, there are slightly stricter rules to follow to ensure grid safety and stability.

What do ‘peak power’ and ‘connection capacity’ mean?

‘Peak power’ is the maximum power your panels can produce under ideal conditions. ‘Connection capacity’ is the maximum power you are authorised to send to the grid. It’s important to choose them carefully for everything to work well.

Can you have a solar installation if you’re not directly connected to the public grid?

Yes, this is called ‘indirect connection’. It can apply to somewhat specific situations, for example, if you’re in a housing estate or an area where a direct connection is complicated. There are specific procedures to follow, and it can incur costs.