Does a small wind turbine pay off on a farm or business?

A small wind turbine pays off on a farm or business when three things come together: an open, windy site, a large own use in winter and at night, and a battery that stores what the turbine and the solar panels make. Inside an off-grid system that saves a medium voltage connection, the whole installation paid for itself within 4 years on a dairy farm. On its own, at a sheltered spot, a small turbine rarely earns its money back.

Your solar panels do well from April to September. Then winter comes, the panels give almost nothing at 5 pm, and the milking robot, the fans and the pumps keep running. So you look at the empty field behind the shed and think: a windmill would turn right when I need it. Your neighbour says his never made any money. A seller promises a yield that sounds too good.

Both can be right, because a turbine is only as good as its wind and its job. The hidden cost is not the turbine itself. It is a mast that stands in the turbulence of your own sheds, a permit you only ask for after buying, or a turbine bought to cut a bill when the real problem was a connection that cannot grow.

A dairy farm in Lokeren had that real problem. Fluvius could only give more power with a switch to medium voltage. The farm put that budget into solar panels, a wind turbine and a battery system. It was paid back within 4 years, because the medium voltage connection was never needed.

When does a small wind turbine pay off on a farm or business?

A small wind turbine pays off when it produces a lot of power that you use yourself, at moments when solar cannot. The fastest paybacks come when the turbine is part of a system that avoids a large one-off cost.

Enerpedia, an energy knowledge site for Flemish agriculture, says a well-chosen and well-placed small turbine can be paid back in 7 to 10 years. Our own off-grid projects without an avoided cabin are usually paid back in 6 to 8 years, with solar doing most of the work. The avoided medium voltage connection is what brings the payback down to about 4 years.

How much power does a small wind turbine produce?

There is no fixed figure: the yield of a small wind turbine depends mostly on the average wind speed at hub height. The Flemish Department of Agriculture explains why: the power of a turbine rises with the cube of the wind speed.

So a small difference in wind has a big effect. According to the department, the average wind speed drops from 6 to 7 m/s at the coast to 2.5 to 3 m/s in large parts of Limburg. A turbine that works well in the polders can be a poor buy in a sheltered valley. Enerpedia adds that small height differences, large trees or dense buildings have a very big impact.

Obstacles matter as much as the region. The department advises at least 2 times the obstacle height between the turbine and a building on the side where the wind leaves the turbine. On the side where the wind comes from, it advises 20 times the height. For a shed of 10 m that means 200 m of open space towards the south-west, where most of our wind comes from.

For scale: Inagro placed a medium-sized turbine with a hub height of 36 m at its research centre in Rumbeke-Beitem. It expects 200,000 kWh a year, which according to Inagro covers the needs of an average dairy or pig farm. A small turbine under 15 m produces far less.

Why do wind and solar work well together on a farm?

Wind and solar complete each other on a farm because they produce at different moments. Solar panels give power mostly in summer and during the day. Wind gives power also at night and mostly in winter.

That is exactly when a farm or a business with night loads needs it. At the dairy farm in Londerzeel we call it the perfect marriage: the solar panels cover the summer days, the wind turbine the winter and the night, and the battery shifts the power to the moment it is used. The farm runs fans, manure scrapers, manure pumps and milking robots on that system.

The battery is what turns a gusty turbine into usable power. Without storage, a strong wind at 3 am is only useful if something happens to be running. With a battery, that night wind is still there for the morning milking.

What does the battery do between the wind turbine and your farm?

The battery stores what the wind turbine and the solar panels produce and delivers it when the farm needs it. In an off-grid system it is the heart of the installation. In a semi-off-grid system the grid connection stays, but only as a charger.

The battery also adds power. In a semi-off-grid project in Wingene, the battery alone delivers 3 x 400 V at 63 A. Whatever the solar panels, or a wind turbine, produce at that moment comes on top. That is why no medium voltage was needed. When the battery is full, a heating element warms a boiler, so surplus power is stored as hot water. Smart control can also switch pumps and boilers on when there is overproduction.

Do you want to keep the grid as a safety net? Then read how our semi-off-grid systems use the connection only to charge the battery. A farm in Tielt is built that way, with room for a wind turbine later.

What does a small wind turbine cost, and how do you judge a payback claim?

A small wind turbine costs much more per kW than a large one. Renouvelle puts a small turbine at 4,000 to 9,000 euro per installed kW, against about 1,320 euro for a large turbine. A 4 kW turbine then costs 16,000 to 36,000 euro.

Renouvelle also warns that small turbines often produce up to 4 times less than announced. So ask these questions before you sign:

Do you need a permit for a small wind turbine in Flanders or Wallonia?

Yes, in both regions. In Flanders a small wind turbine is never exempt from the omgevingsvergunning (the Flemish environmental and planning permit). In Wallonia you need a permis d'urbanisme (planning permit).

Flanders. The Flemish government's permit guide is clear: small wind turbines are not exempt in agricultural zone, and need a permit in every zone. Even a mini turbine on a house roof needs one, because it is not seen as a usual technical construction. The same guide sets two conditions for small turbines:

• The turbine must serve an existing, permitted building, installation or business close to the turbine.
• At least 50% of the energy it produces must be used locally. The permit authority checks this.

A small turbine here means a hub height of up to 15 m. Fluvius describes a turbine for own use as at most 15 m high and under 25 kW. Your municipality decides on the permit; Flanders itself only handles turbines above 1,500 kW. The municipality also weighs the impact on neighbours, and the Vlarem noise standards play an important role.

Wallonia. The CoDT (the Walloon planning code) allows in agricultural zone the production of electricity or heat that directly supplies buildings on the same property. For wind this means one turbine per property, with a mast of at most 24 m. Larger turbines in agricultural zone must stand within 1,500 m of a main road or an economic activity zone. For a turbine that feeds your own farm, the municipality (collège communal) issues the permit; for turbines that only inject into the grid, the regional official (fonctionnaire délégué) does.

Which farms and businesses already combine wind, solar and a battery?

Our projects with wind are mainly dairy farms that had to grow without a medium voltage connection. Here is what each one shows.

Take a look at the projects: the dairy farm in Lokeren, the dairy farm in Londerzeel, the project in Wingene and the site in Beveren-Melsele. The Londerzeel farm is also presented in our video on off-grid for the agricultural sector (in Dutch).

Beveren-Melsele shows the other side too. The site uses about 350,000 kWh a year. It uses as much of its own solar power as possible, a medium-sized turbine is planned, and the remaining peak current still comes from a high voltage cabin. Wind and a battery do not always replace the grid; sometimes they only shrink what you take from it.

When is a wind turbine not worth it?

A wind turbine is not worth it when the wind at your site is weak or turbulent, when you use little power in winter, or when the only goal is a slightly lower bill.

• Your site is sheltered. Between trees, sheds or houses, the wind is turbulent. It may feel windy, but a small turbine gets little energy out of it.
• You want to put it on a roof. Roof wind is turbulent, and the permit is still needed.
• Your use is mainly in summer and by day. Then more solar panels and a battery do the job more simply.
• Your connection is fine. Without an avoided cabin or connection, a turbine competes only with the price of grid power, and the payback gets long.

In those cases, start with the simpler steps. Our article on solar panels and a battery on a farm shows what to do first.

What happens when you ask us about wind on your farm?

We size, design and install the full installation, and we calculate the savings clearly. Every off-grid installation is made to measure and can be extended later, for example with an extra energy source such as a wind turbine.

1. Step 1: Pre-study. We look at your consumption over the year, your roof and your land, and at what the grid operator offered. During the pre-study we also set the battery capacity you need.
2. Step 2: Design. We decide whether wind adds enough next to solar at your site, and how the battery, the grid or a generator fit in.
3. Step 3: Installation. We install and commission the system.
4. Step 4: Follow-up. You follow in real time, 24/7, what you use, what you produce and how full the battery is, in the app or on the website.

Everything about our off-grid systems for farms and businesses is on the product page. Is your farm running into the limits of its connection? Then also read whether a medium voltage cabin or a battery is the better answer.