Wind turbine + BESS — how to turn grid connection into a flexible revenue platform

Wind turbines are no longer just production facilities. With a BESS installation, load bank, and intelligent control, an existing wind turbine can be developed into a flexibility asset that both produces green power, provides system services, and utilizes grid capacity that otherwise stands unused for large parts of the year.

This is particularly relevant for wind turbine owners, as the grid connection is often one of the most valuable assets in the project.

The wind turbine's hidden value: the grid connection

A 1-2 MW wind turbine only produces full output for a limited part of the year's hours. The rest of the time, there is spare capacity in the grid connection — an unutilized potential for flexibility.

Where the classic model is: Wind turbine produces power → power is sold on the spot market, the modern model can be: Wind turbine + BESS + load bank + EMS → system services, regulation, spot optimization, and better grid utilization. This changes the entire business model.

From arbitrage to system services

Many associate batteries with arbitrage — that the battery is charged when power is cheap and discharged when power is expensive. Arbitrage can still be relevant, but it should not be the main business case.

In modern BESS projects, the primary value typically lies in system services — the services used to keep the electricity grid in balance. Batteries are well-suited for this because they can react quickly and precisely, absorb and deliver power, and be controlled automatically via EMS and SCADA.

A concrete calculation: 2 MW wind turbine + 9 MWh battery

In a concrete analysis of a 2 MW wind turbine installation combined with a 9 MWh battery, the calculations showed the following gross revenues:

Operating scenario	Annual gross revenue
Wind turbine alone	DKK 2.70 million
Wind + negative price arbitrage	DKK 3.51 million
Wind + extended spot optimization	DKK 4.18 million

If one instead looks at system services on top of wind production, the difference becomes even clearer:

Product	Total gross revenue incl. wind turbine
FCR	DKK 4.69 million
aFRR up	DKK 7.25 million
Best up-product strategy	DKK 8.11 million

The result clearly shows that in many situations, system services can create greater value than traditional arbitrage alone.

Why BESS complements wind turbines

A BESS installation makes the wind turbine more flexible in three ways: the battery can be charged with local wind production and reduce dependence on purchases from the grid; it can provide upward regulation when the electricity grid lacks power; and together with a load bank, it can provide downward regulation when the electricity grid has too much production. The wind turbine thus becomes not just a passive producer, but an active flexibility resource.

Load bank: the overlooked key to downward regulation

A load bank is controllable electricity consumption — the facility can use power on command when the electricity grid needs downward regulation. In combination with a wind turbine, this provides great value because the opportunity arises to absorb surplus production locally, during negative electricity prices, for testing and pre-qualification, balancing, and local utilization of wind production.

In one of our concrete projects for an existing wind turbine owner, a 2 MW load bank is included together with a 2 MW BESS and an existing 2 MW wind turbine. The analysis assesses that the load bank is a central technical asset because it increases flexibility and the possibility for downward regulation.

System services require energy — not just power

It is not enough to say that a battery has 1 MW or 2 MW of power — one must also look at the energy capacity. If a facility, for example, needs to deliver 1 MW for 8 hours, it requires at least 8 MWh of usable energy. This is particularly important in relation to mFRR and LER status: batteries can be considered a Limited Energy Reservoir if they do not have sufficient energy storage to deliver the sold service in the required time.

In this project, the battery pack is dimensioned as approx. 4 MW / 9.26 MWh physical capacity, but software-limited to 2 MW active power at the grid connection point. The usable capacity at Beginning of Life is approx. 8.69 MWh — which provides a significant technical advantage: the facility can in principle cover 1 MW for 8 hours at start.

Why over-dimension the battery?

In this project, the solution consists of four battery containers of 1 MW / approx. 2.315 MWh each. The total physical pack is approx. 4 MW / 9.26 MWh, but the facility is controlled as a 2 MW flexibility installation at the grid connection point. This provides a better energy buffer, stronger SOC control, better opportunity for system services, lower risk of failure to deliver, better handling of battery degradation, and the possibility of mFRR 1 MW for 8 hours at BOL.

The decisive factor is therefore not just the “size” of the battery, but the relationship between power, energy capacity, grid limit, and market product.

EMS: the brain of the facility

When wind turbine, BESS, load bank, and charging stations are combined, control becomes crucial. The EMS system must ensure that the facility does not exceed the grid limit — if the wind turbine produces at the same time as the battery discharges, the export may become too high; if the battery charges at the same time as the load bank and charging stations use power, the import may become too high. Therefore, the entire energy point must be controlled as a whole, with SOC limits, bidding strategy, LER status, grid limits, measurement, alarms, automatic bid stops, and DataHub/SCADA integration.

This is where a BESS project goes from being hardware to becoming a controllable energy facility.

Prioritization: system services first, arbitrage as an optimization layer

In a modern flexibility project, the prioritization should be: system services first, SOC reserve for bid services, local wind charging, charging during low or negative price hours, load bank for downward regulation, and arbitrage when it does not weaken system services. The analysis concludes precisely that the base scenario should be sold as a system service project with strong energy reserves — not as a pure arbitrage case.

The financials: flexibility can surpass the wind turbine's base operation

An existing wind turbine can already be a healthy asset. The accounting figures for the existing wind turbine in this example show a result before depreciation of approx. DKK 2.20 million in 2025 and approx. DKK 2.13 million in 2024.

The new flexibility case is assessed to have an expected annual net earnings of approx. DKK 6.05-7.95 million after aggregator fees, fixed operating costs, and a moderate charging station contribution. This shows the difference: the wind turbine creates value through production, BESS and load bank create value through flexibility — and the combination can increase the value of the existing asset significantly.

The investment

In this project, the total investment for 2 MW BESS, 2 MW load bank, and 600 kW charging stations is estimated at approx. DKK 16.0-18.25 million excl. major grid contributions, land, financing, and potential ampere purchases. After an assumed 40% subsidy, the net investment is reduced to approx. DKK 9.6-10.95 million.

This gives an estimated simple payback period of approx. 1.2-1.8 years in the expected scenario after subsidy. The figures must of course be verified in each individual project, but they show the potential in utilizing an existing wind turbine as a platform for flexibility.

A smaller illustrative example: 1 MW battery + load bank + charging stations

In addition to the case above, a smaller, purely illustrative calculation example on a 1 MW scale can give a concrete impression of the figures behind a complete flexibility setup. Note: this is a separate, generic example — not the same facility as described above.

• Battery (BESS) — 1 MW / 4.63 MWh: LFP battery with response time under 30 ms. Can both regulate up and down and participate in FCR, aFRR, mFRR, and FFR.
• Load bank — 1 MW: Controllable electricity consumption that absorbs surplus power at low and negative electricity prices. Covers FCR-D down and mFRR down.
• DC charging stations — 300 kW: Prerequisite for the state project subsidy. Can itself provide downward regulation (FCR-D down, aFRR down) via OCPP 2.0.

Investment item	Amount
Battery (BESS) 1000 kW	DKK 5,195,000
Load bank 1000 kW	DKK 600,000
Charging station 150 kW	DKK 300,000
Container	DKK 150,000
Electrical cabinet	DKK 300,000
Project management & installation	DKK 350,000
Total investment	DKK 6,630,000
State subsidy (40%)	−DKK 2,652,000
Net investment	DKK 3,978,000

Expected annual net earnings	Amount
Gross system services	DKK 4,217,647
Aggregator fee (15%)	−DKK 632,647
Service agreement	−DKK 25,000
Insurance	−DKK 40,000
Net cash flow per year	DKK 3,520,000
Depreciation per year (15 years)	−DKK 331,500
Result before tax per year	DKK 3,188,500

This gives a payback period of approx. 22.6 months before subsidy and approx. 13.7 months after subsidy, with an estimated ROI of 603% over 15 years and a total 15-year net earnings of approx. DKK 27.95 million.

Period	Net cash flow	Accumulated
Year 0	—	−DKK 3,978,000
Year 1	DKK 3,520,000	−DKK 458,000
Year 2	DKK 3,168,000	+DKK 2,710,000
Year 5	DKK 2,309,472	+DKK 10,436,752
Year 10	DKK 1,363,720	+DKK 18,948,519
Year 15	DKK 805,263	+DKK 22,980,132

Note: an annual reduction of 10% in net earnings has been included as a conservative sensitivity calculation in this example. All figures are preliminary decision-making figures subject to pre-qualification, market prices, grid constraints, subsidy approval, and supplier quotes — not a guarantee of future return.

Grid connection is the critical factor

The most important clarification is not just the battery price — it is the grid connection. The following must be clarified: export rights, import rights, metering structure, upward and downward regulation rights, transformer limits, need for ampere purchases, charging station capacity requirements, LER status, pre-qualification, EMS requirements as well as balance responsible party and electricity supplier. In this project, grid limit, LER, EMS, subsidy terms, and charging station grid are highlighted as the critical clarifications.

Conclusion

BESS installations complement wind turbines because they utilize the existing grid connection better, create access to system service markets, and make the wind turbine an active flexibility facility. Arbitrage can still contribute, but should not be the main argument. The strong business case arises when wind turbine, battery, load bank, EMS, measurement, and market access are thought of as one single energy point.

At Meganet, we help wind turbine owners analyze, dimension, and realize BESS solutions where the existing grid connection is used more efficiently — and where value is shifted from pure power production to active flexibility.