Wind and Solar Hybrid Systems: Production at Night Too

A wind-solar hybrid system combines solar panels and a small wind turbine on the same battery bank, and aims to improve energy continuity especially in off-grid installations. The idea looks attractive: sun by day, wind at night and in winter. However, whether the wind will actually produce depends on the location and height, and a decision cannot be made without measurement. In this article we explain the physics, a theoretical calculation, the reality in Antalya and the situations in which a hybrid system makes sense.

How does a wind-solar hybrid system work?

In the system, the solar panels are connected to an MPPT charge controller and the wind turbine to its own charge controller; both feed the same battery bank. Energy drawn from the battery bank is delivered to the home's consumption through an inverter. When the wind blows very strongly, a dump load that burns off excess energy to protect the battery, and a mechanical or electrical brake, come into action.

In off-grid installations, this structure aims to reduce generator running time during hours when the sun is insufficient. Wind energy is also listed on Solar Nexo's service pages; even so, recommending a domestic turbine without an on-site measurement would not be right. For details of the service you can look at our wind energy page.

How much does a wind turbine produce? The cube rule

Power in the wind is proportional to the cube of speed: P = ½ × ρ × A × v³ × Cp. Here ρ is air density (about 1.225 kg/m³), A is the rotor swept area, v is wind speed and Cp is the power coefficient; under the Betz limit, Cp cannot theoretically exceed 59.3%, and in practice it is lower for small turbines. If wind speed doubles, power increases eightfold; conversely, when speed drops, production collapses quickly.

A theoretical example: for a turbine with a 3 m rotor diameter (area about 7.07 m²) and Cp = 0.30:

This table shows only the physical logic; a real turbine's power curve, wind speed distribution and height effect are given in the manufacturer's datasheet. In addition, every turbine has a cut-in speed, below which production is zero. The annual energy of a solar panel and a turbine of the same nominal power cannot be compared: a turbine reaches its nominal power only at its rated wind speed, whereas, according to PVGIS, 1 kWp of panels produces 1,656 kWh a year in Antalya city centre.

The wind reality in Antalya and the importance of measurement

For solar there is a verified and detailed dataset such as PVGIS; for wind, production potential varies very locally. In the same district, wind speed can differ many times over between a hilltop and a valley. Trees, buildings and uneven terrain create turbulence and reduce turbine efficiency. For this reason we cannot give a general "wind yield" figure for Antalya; a site measurement is essential.

In MGM (Turkish State Meteorological Service) records, the fastest wind measured in Antalya is 43.2 m/s (22.01.1998). This is not production data but strength data: the turbine and mast structure must be chosen for the region's storm conditions and the manufacturer's installation requirements must be followed. The height of the turbine tower may require zoning and permits; get written confirmation from the municipality and the relevant authorities.

For measurement, the ideal is to collect data for at least one year with an anemometer at turbine height. A short measurement misses the seasonal effect. The measurement results should show the hourly distribution as well as the average wind speed, because, owing to the cube rule, a small number of strong-wind hours bring most of the total energy.

Complementarity for night and winter

The real argument for a wind-solar hybrid system is that wind and sun produce at different times. According to PVGIS, 1 kWp of panels in Antalya produces 168 kWh in July and 99 kWh in December. Winter production is about 59% of summer production (calculation). In locations where wind will contribute in these months and at night, a hybrid system can reduce the battery and generator load.

However, this complementarity is not guaranteed everywhere. In Antalya there may be points where winter and night winds are strong, but measurement must show this. In a location where wind is weak, a turbine investment does not pay back; with the same budget, extra panels and battery can provide far more reliable energy. For detailed data on winter production you can read our winter solar panel performance article.

When does a domestic turbine make sense?

A small wind turbine can be considered under these conditions: open, unobstructed land, sufficient measured wind, an installation far from the grid (off-grid), the goal of reducing generator fuel cost and the ability to raise the tower to sufficient height. Mounting a turbine on a building roof in a city centre is mostly inefficient; both turbulence and structural vibration create problems.

• Siting: A mast that rises above obstacles reduces turbulence.
• Noise and vibration: Distance from the dwelling and connection details are design criteria.
• Maintenance: Because of moving parts, it requires far more maintenance than a solar panel.
• Safety: In extreme wind, a braking system and a solid mast anchor are mandatory.

For this reason, in most residential projects a solar system alone is sufficient and the solution that needs the least maintenance. For off-grid solutions you can look at our off-grid systems page, and for combined structures our hybrid systems page.

Cost items and maintenance

We do not give prices because tower, foundation and turbine choice vary greatly with the site; however, knowing the items is enough for a decision. The main items are the turbine, tower and anchorage, the turbine controller, the dump load, the battery bank, cables, earthing and installation labour. A solar panel has no moving parts; a wind turbine needs checking at least once a year for bearings, blades and connections. Blade imbalance creates vibration and noise. Maintenance burden is often overlooked in a wind-solar hybrid system decision.

For this reason it is safer to take the first step with the solar and battery design and to run the wind measurement as a separate feasibility study. If the measurement shows sufficient wind, adding a turbine later is possible; if the controller and battery bank are planned to suit this expansion, the additional investment becomes easier. For a business using a generator on a remote highland pasture, this approach can reduce fuel and maintenance burden step by step.

System sizing and control architecture

Wind-solar hybrid system design looks not at a single source but at the total energy and simultaneity of two sources. Because both sources can fill the battery bank at the same time, the charge current limit and battery capacity must be calculated together.

The most critical decision in a hybrid system is the compatibility of the battery bank and the charge controllers. A wind turbine produces variable-frequency AC; this is converted to DC with a rectifier. When the battery is full, the turbine controller diverts the turbine to the dump load; leaving the turbine on open circuit can send the rotor to over-speed and is dangerous. On the solar side, the MPPT controller curtails production when the battery is full.

The battery bank capacity should be chosen to cover windless and sunless days. LiFePO4 batteries are common in this application; for details you can look at our LiFePO4 battery guide. In regulatory terms, off-grid installations are exempt from the licence obligation as facilities with no connection to the transmission or distribution system; however, zoning, structural and other obligations are assessed separately.

Conclusion

A wind-solar hybrid system is a strong complement in the right place; in the wrong place it is an expensive add-on that brings a maintenance burden. Because of the cube rule of wind speed, no decision should be made without measurement. For most homes and businesses in Antalya, the solar and battery solution is designed first; wind is considered as an additional option on open and measured sites. For an assessment specific to your land, you can request a free site survey from Solar Nexo and, by evaluating wind and solar data together, make clear whether a hybrid system is really necessary for you. Avoiding an unnecessary turbine investment is as valuable as a turbine installed in the right place.

#Systems#Wind Solar Hybrid#Wind Turbine#Off Grid#Hybrid Energy#Antalya Wind