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While liquid-immersed transformers have traditionally dominated the utility sector, dry-type transformers have carved out a significant and growing niche within the renewable energy landscape.
Here is how dry-type transformers are specifically integrated into solar, wind, and energy storage systems.
1. Solar PV Systems: Inverter Duty Integration
In large-scale solar farms, dry-type transformers are frequently used as Inverter Duty Transformers
Step-Up Function: Solar panels generate DC power, which inverters convert to low-voltage AC (typically 600V–800V). Dry-type transformers step this up to medium voltage (11kV–35kV) for collection.
Harmonic Resilience: Inverters produce high-frequency harmonics that can cause standard transformers to overheat.
Modern dry-type units are engineered with high K-factors (e.g., K-13) to handle these non-linear loads without insulation degradation. Safety in Rooftop Solar: For commercial and industrial (C&I) rooftop solar, dry-type units are mandatory in many jurisdictions because they eliminate the risk of flammable oil leaks on top of occupied buildings.
2. Wind Energy: Nacelle and Tower Installation
Wind turbines present a unique engineering challenge: space is limited and vibration is constant.
Nacelle-Mounted Units: In many modern turbine designs, the transformer is located inside the nacelle (the housing at the top of the tower). Dry-type transformers are preferred here because they are lighter than oil-filled units and present zero fire risk to the turbine's mechanical components.
Vibration Resistance: Cast resin dry transformers are structurally rigid.
The solid encapsulation of the windings makes them highly resistant to the mechanical stresses and vibrations generated by the turbine blades. Offshore Applications: For offshore wind, specialized dry-type units with C5-M corrosion-resistant enclosures are used inside the tower base to prevent saltwater air from corroding the core.
3. Battery Energy Storage Systems (BESS)
The global surge in energy storage has made dry-type transformers a "default" choice for BESS containers.
Containerized Solutions: BESS units are essentially shipping containers filled with lithium-ion batteries. Because these containers are compact and carry a high fire risk already, adding flammable mineral oil is often prohibited.
Bi-directional Flow: Dry-type transformers in BESS must handle bi-directional power flow—stepping down power to charge the batteries and stepping it up to discharge into the grid.
Compact Footprint: The high power density of cast resin technology allows these transformers to fit into the tight auxiliary compartments of a BESS container.
4. Key Advantages for Renewables
| Feature | Benefit to Renewable Projects |
| Environmental Safety | Zero risk of soil or water contamination (critical for wind farms in forests/coasts). |
| Fire Safety | Self-extinguishing materials allow for installation in towers or rooftops. |
| Low Maintenance | No oil testing or gasket replacements; ideal for remote, unmanned sites. |
| Space Efficiency |
Compact design allows for integration into prefab containers or turbine towers. |
5. Technical Challenges and 2026 Innovations
While dry-type units are highly effective, they do face specific challenges in the renewable sector:
Voltage Limitations: Dry-type units are generally limited to 35kV. For the main substation "gateway" to the high-voltage grid (110kV+), oil-immersed units are still required.
Cooling in Deserts: In high-heat solar environments, dry-type units require forced-air cooling (fans) to maintain efficiency.
Eco-Resins: A 2026 innovation involves the use of bio-based resins for encapsulation, further reducing the carbon footprint of the transformer itself to align with the "green" mission of the project.
Summary: When to Choose Dry-Type for Renewables
Dry-type transformers are the superior choice for decentralized renewable assets where safety, space, and environmental protection are the primary concerns. They are the "workhorses" inside wind towers, solar containers, and battery sheds, while oil-immersed units remain the "gatekeepers" at the utility substation.