Direct marketing: connecting wind farms and single turbines to EMSYS

The contract with your new direct marketer is signed and the start date is set. Then the email with the data point list arrives: actual active power value, setpoint specification, feedback, status signals, all via a secure connection. Many operators only realise at this point that their turbine has been reliably generating electricity for years but has never received a setpoint from outside.

This technical bridge between wind turbine and marketing platform is the subject of this article. We build it for single turbines and wind farms, manufacturer-independent and often on controllers that are twenty years old or more. We have been operating our own wind turbines since 1998. Whatever we develop runs in our own fleet first.

You will learn what the German Renewable Energy Sources Act (EEG) specifically requires, how the connection to EMSYS works technically, which variants exist, where older controllers from Vestas, Enercon, Südwind or DeWind cause problems and how a connection project runs step by step. By the end, you will know which questions to ask your direct marketer, your grid operator and us.

What direct marketing requires technically

In direct marketing (Direktvermarktung), you no longer sell your turbine’s electricity to the grid operator at a fixed rate but on the electricity market through a direct marketing company. If your turbine is still within the EEG, you also receive the market premium: it makes up the difference between the value set by law or by tender and the market value of the electricity. The direct marketer pools many turbines, forecasts their generation and trades it.

For this to work, the direct marketer must be able to see and control your turbine. A trader who cannot curtail output when electricity prices are negative loses money. That is why the law makes remote controllability mandatory.

Remote controllability under Section 10b EEG

The central provision is Section 10b EEG 2023, headed “Requirements for direct marketing” (“Vorgaben zur Direktvermarktung”). It requires two things: a technical facility and an authorisation. The technology must allow the direct marketer to retrieve the actual feed-in value and to control the feed-in power remotely at any time. You grant the authorisation by contract.

The gradation is important. At a minimum, the turbine must be capable of full curtailment. If the controller can reduce output in stages or continuously, it must also do so. In practice, this means a simple off switch is only sufficient if the controller technically allows nothing else.

There is a simplification for wind farms. If several turbines are connected to the grid at the same grid connection point, a shared technical facility through which the direct marketer can control them as a whole is sufficient. This is typically a wind farm controller or a central telecontrol unit.

Who is affected: new turbines, switchers and post-EEG

The obligation applies to installations with an installed capacity of more than 25 kilowatts whose electricity is marketed directly. That covers practically every wind turbine. We encounter three groups particularly often:

1. Turbines within the EEG receiving the market premium whose remote control ran via the previous marketer and has to be set up again for the new marketer.
2. Turbines whose EEG support has expired (post-EEG), i.e. turbines after the end of the 20-year payment period under Section 25 EEG. They market their electricity directly without a market premium, for example via a supply contract with a buyer. Section 10b applies in this case too.
3. Older turbines with controllers that have no setpoint input and could previously only be reached via the manufacturer’s remote monitoring, or not from outside at all.

For turbines whose EEG support has expired, the EEG also provides an entitlement to a feed-in tariff, minus a value published by the transmission system operators. Under Section 25(2) EEG, this tariff is paid until 31 December 2032. Whether this route or direct marketing is economically better for your turbine is something to clarify with your grid operator and your adviser. As far as the technology is concerned: as soon as you market directly, you need remote controllability.

What a breach costs

If remote controllability is missing, it gets expensive. Under Section 52 EEG, installation operators must then pay the grid operator €10 per kW of installed capacity for each calendar month in which the breach exists in whole or in part. For a 2,000 kW turbine, that works out at €20,000 per month.

If the obligation is met later, the payment is retroactively reduced to €2 per kW per month. If the technology fails due to a defect, no payment is due for the month concerned and the following calendar month. However, you must be able to prove the defect. We will come back to this when we look at evidence.

EMSYS: the platform between turbine and market

Many direct marketers do not control their turbines with their own software but via a virtual power plant. This is a software-based control room that aggregates distributed generators, monitors them, controls them remotely and makes their combined output marketable. A widely used platform for this is the virtual power plant from emsys in Oldenburg. When we talk about connecting to EMSYS, we mean connecting your turbine to this platform.

Who is behind EMSYS

The virtual power plant was developed at energy & meteo systems GmbH in Oldenburg, which is best known for wind and solar power forecasts. On 1 June 2021, the company spun off this business unit: since then, emsys VPP GmbH has operated the virtual power plant and emsys grid services GmbH the redispatch platform for grid operators. energy & meteo systems announced this itself. According to this announcement, numerous energy suppliers and direct marketers use the platform.

For you as an operator, this is mainly relevant in organisational terms. Your contractual partner remains the direct marketer. However, the technical specifications for data points, connection and commissioning test usually come from the platform.

What the platform needs from the turbine

The platform does not talk directly to the generator but to a target device at the turbine. This can be a data logger, a wind farm control system (SCADA) or a programmable logic controller (PLC). According to the emsys Box FAQ, this target device supplies measurement data and receives setpoints. Measurement data are usually retrieved every 30 seconds.

emsys names Modbus TCP and IEC 60870-5-104 as protocols. The emsys Box itself is a preconfigured router that establishes a VPN connection to the platform’s servers. So it does not replace the control technology at the turbine; it only provides the secure channel.

The technology at the turbine: from control cabinet to platform

There are three levels between the rotor and the trading platform. At the bottom is the turbine controller, which regulates power, speed and pitch. In the middle is a telecontrol unit that collects data, translates it and passes on setpoints. At the top is the communication path to the platform. Each level has to match the next.

Data points: actual value, setpoint, status

The data point list defines which values are exchanged and in which format. The exact list comes from the direct marketer or the platform. It typically contains these groups:

• Actual active power value at the feed-in point or per turbine, the basis for forecasting and billing.
• Active power setpoint, as a percentage of installed capacity or as a kilowatt value.
• Setpoint feedback, so that the platform can see that the specification has arrived.
• Availability and status, such as operation, fault, maintenance or shutdown by external systems.
• Meteorological values such as wind speed, where required, to improve the forecast.

For wind farms, there is also the question of whether the values are supplied at the grid connection point or per turbine. Both have consequences for the metering equipment and for how the setpoint is distributed across the individual machines.

Protocols: Modbus to the turbine, IEC 104 to the control room

Modbus is a simple industrial protocol that controllers use to read and write registers. Many turbine controllers and wind farm controllers speak Modbus TCP over Ethernet or Modbus RTU over a serial line. IEC 60870-5-104, IEC 104 for short, is the telecontrol standard in the energy industry. It transmits measured values and commands with time stamps and is designed for control rooms.

In practice, the telecontrol unit often translates between the two worlds: Modbus or a proprietary manufacturer protocol towards the turbine, IEC 104 or Modbus TCP towards the platform. With proprietary interfaces, this is where it is decided whether a project runs smoothly or whether a protocol description first has to be obtained from the manufacturer.

Communication path and security

The platform needs a stable, permanent internet connection to the site. Among other things, the emsys FAQ require that the router is allowed to establish VPN connections via UDP and that the target device is reachable at a private IP address. Many wind sites have no fixed-line connection. In that case, we set up a mobile link via 4G or 5G or lay fibre-optic cabling within the wind farm, depending on the site, data volume and required reliability.

For new installations, Section 10b(2) EEG requires transmission technology that reflects the state of the art at the time of commissioning and is economically reasonable. If you take into account the standards and recommendations of the Federal Office for Information Security (BSI), compliance with the state of the art is presumed. From 1 January 2028, the obligation must be met via the Smart-Meter-Gateway as soon as an intelligent metering system has been installed. If you are setting up a new connection today, factor this transition into your planning.

Connection variants compared

There is no single right solution. Which variant fits depends on the existing controller, the size of the wind farm and the question of who will look after remote control in future. The following overview summarises the variants we come across in our projects.

Single turbine or wind farm: what is different

With a single turbine, the telecontrol unit sits in the tower base or in the transfer station and talks directly to the controller. The setpoint applies to exactly one machine. That is manageable, but not automatically simple if the controller is old.

In a wind farm, a central device distributes the setpoint across several turbines. If the turbines come from different manufacturers or were built in different years, the telecontrol unit has to serve different interfaces. This is where a manufacturer-independent approach pays off. Another advantage: a shared system also provides a uniform data basis for remote monitoring of the entire wind farm.

Pitfalls with older controllers

The older the turbine, the greater the likelihood that remote controllability cannot be achieved with a router alone. That is no reason to worry, but it is a reason to start earlier. These are the points we check first on older turbines.

When the controller has no concept of a setpoint

Many controllers from the 1990s and early 2000s were built for feeding in according to grid demand, not for market signals. Some offer only a remote stop, others an input for power levels that the grid operator uses via a radio ripple control receiver. A continuous setpoint specification via a network protocol is often missing entirely.

There are then three options: share an existing step input, address a power limitation via the controller’s parameters or, if none of this is possible, implement full curtailment as the technically feasible minimum solution. Which route is permissible and sensible is something we clarify together with you and your service company.

Manufacturer interfaces and service access

With turbines from major manufacturers such as Vestas or Enercon, data and control commands often run via the manufacturer’s own wind farm control system or remote monitoring. Whether an interface for direct marketers can be activated there, and on what terms, is a question for the manufacturer or your service contract. We respect existing manufacturer solutions and integrate them wherever this is technically and contractually possible.

The situation is different for turbines whose original manufacturer no longer exists in its former form, for example some types from Südwind or DeWind. Here, current documentation, protocol descriptions or contacts are often lacking. In such cases, we work with the service company that looks after the turbine and open up the interface on the existing controller. Because we have been operating our own turbines since 1998, we know this situation first-hand.

Permit conditions and shutdown systems

Many turbines operate under conditions attached to their permit: bat shutdown, bird detection, ice detection or sector shutdown. These shutdowns take precedence over any market signal. The EEG explicitly takes this into account: the direct marketer’s authorisation only extends as far as it is not demonstrably excluded by permit requirements.

Technically, this means the telecontrol unit must know whether the turbine is at a standstill because of a permit condition and report this to the platform as a status. Otherwise, the direct marketer sees a turbine that is not feeding in despite being released and calculates with incorrect values. Where we integrate external systems into the controller anyway, this status message can be supplied directly as well.

Redispatch 2.0: two actors, one turbine

Besides the direct marketer, a second actor accesses your turbine: the grid operator. Redispatch 2.0 has applied since 1 October 2021. This refers to congestion management in the power grid, in which grid operators deliberately ramp generation up or down to avoid overloads. According to the Federal Network Agency (Bundesnetzagentur), Redispatch 2.0 covers all installations of 100 kilowatts and above, explicitly including renewable energy installations. The former feed-in management scheme (Einspeisemanagement) has been merged into it.

Roles: deployment manager and operator of the technical resource

Redispatch 2.0 works with roles. The deployment manager (EIV) provides the grid operator with planning data and implements calls. The operator of the technical resource (BTR) is responsible for the installation itself. The installation operator can take on both roles. In practice, the EIV role is often taken on by the direct marketer, because it already runs the necessary IT systems and data flows.

What matters for the technology is how calls reach the turbine. In the so-called toleration case (Duldungsfall), the grid operator controls the turbine directly. In the request case (Aufforderungsfall), it asks the EIV to adjust the output, and the EIV passes this on to the turbine as a setpoint. Which model applies to you is something you agree with the grid operator and the direct marketer.

Implementing grid operator priority properly

Section 10b(3) EEG makes it clear that remote control by the direct marketer must not restrict the grid operator’s measures. For the telecontrol unit, this means clear prioritisation. If a grid operator signal and a market signal arrive at the same time, the greater reduction always applies.

1. Safety and permit-related shutdowns such as ice, bat or sector shutdowns take precedence over everything else.
2. Grid operator specifications, whether via the grid operator’s own telecontrol equipment, a radio ripple control receiver or the EIV, come next.
3. Direct marketer setpoints only take effect within the scope left by the first two levels.

This logic should be documented and tested before the turbine goes to market. Otherwise, errors only come to light when a bill is wrong or the grid operator starts asking questions.

How a connection project runs

Connecting to EMSYS is not a major project, but it is one with many parties involved. Most delays arise at the interfaces between them, not in the technology. The following table shows who is typically involved at which step.

Preparation: which documents help

The more you have ready at the start, the faster the initial assessment. The following are helpful:

• Turbine type, year of construction and controller version, for each turbine in the case of wind farms.
• Your direct marketer’s data point list and technical requirements.
• Details of the existing grid operator equipment, such as a radio ripple control receiver or telecontrol system.
• Permit conditions with shutdown times and the documentation for existing shutdown systems.
• Information on the data connection at the site: fixed line, mobile reception, existing fibre-optic routes.
• Contact details for the service company and, if applicable, the manufacturer’s service.

On your side, you provide the supply cables, connections and power supply for the equipment. We clarify this during the technical coordination so that nothing is missing on installation day.

Testing and acceptance: the curtailment test

After installation, the platform first checks whether the connection and measurement data retrieval work. This is followed by a curtailment test: the platform sends setpoints and all parties check whether the turbine implements them and reports back correctly. According to emsys, this requires sufficient feed-in. If there is no wind, the appointment is postponed.

Our advice from practice: test internally beforehand, before the official appointment is fixed. Otherwise, a setpoint that arrives at the turbine with the wrong scaling will cost you a second appointment and, in the worst case, the Section 10b deadline.

A realistic view of costs and benefits

We do not quote flat-rate prices because they depend on the controller, site and variant. However, the cost structure can be described clearly, and the benefits are clearer than many people think.

What the costs are made up of

Where the connection pays off

The most important benefit is simply access to the market. Without remote controllability, no direct marketer will sign a contract with you, and every month without working technology can trigger a payment under Section 52 EEG of €10 per kW. Compared with this sum, a properly implemented connection is usually justified quickly.

There are also benefits that go beyond the obligation. A turbine that reliably supplies actual values and implements setpoints precisely is easier for the marketer to plan. And if you are modernising the telecontrol unit anyway, you can bring remote monitoring, camera or remote switching up to a common standard at the same time.

Proof instead of assumptions: database servers and live displays

Remote control works and the test has been passed. This is where the part that is often underestimated begins: operation over many years. The question here is whether, if in doubt, you can prove what your turbine did and when.

What should be recorded

A fully automatic database server continuously records the operating data: power, wind, operating states and messages. For direct marketing, the received setpoints and how they were implemented are also of interest. This makes it possible to trace later whether reduced feed-in was caused by the market, the grid operator, a permit condition or a fault.

This is more than tidiness. In the event of a defect in a technical facility, Section 52 EEG requires the installation operator to set out and prove the defect. A complete record of connection status and setpoints is the best basis for this. Your own data, held independently of the platform and the grid operator, also help with queries about the settlement of redispatch measures.

Detecting faults quickly

Live displays show the current status at a glance, in the office or on site. If a setpoint is active that does not match the weather conditions, or if the connection to the platform drops, you see it immediately and not only at the next billing. With online monitoring, you detect faults around the clock. Remote administration of the system is handled by our office during normal business hours.

Our approach: the data belong to you and are stored in your system. If you later switch direct marketer, the history is retained and the telecontrol unit only needs to be adapted to the new data point list.

Frequently asked questions

Conclusion

Connecting to EMSYS is not a formality, but it is not rocket science either. The EEG requires the actual value and remote control, the platform requires a target device with Modbus TCP or IEC 104 and a secure connection, and the grid operator requires priority for its specifications. With newer turbines, this can often be solved via existing interfaces. With older controllers, a careful initial assessment decides whether the Section 10b deadline can be met.

If you are moving into direct marketing, switching marketer or want to continue operating a turbine whose EEG support has expired (post-EEG), start with the technology, not after signing the contract. We connect single turbines and wind farms manufacturer-independently, implement schedules and curtailments at the turbine and use database servers and live displays to ensure that you can prove at any time what your turbine has done. Get in touch with us.