Wind Turbine Cellular Base Station

The Problem

Rural communities and areas often find mobile-phone service to be limited in options and availability.  One can look at coverage maps of the many cell-phone service providers to see that there are large areas of the United States, typically rural areas with little population, where cell-phone service is not available. For the service providers, placing towers in those rural areas is an expensive investment with low likelihood of a return

While mobile-phone service is sparse in rural communities, these same areas are being “populated” with wind farms to generate clean (i.e., no carbon emissions) energy.  Wind turbines are typically, though not exclusively, located on top of hills in rural and remote locations in open areas to maximize the capture of wind energy and around 90 meters in height

The Solution

An omni-directional radio frequency (RF) antenna for receiving and transmitting cell-phone communication data is on each blade of a wind turbine. Each RF antenna has a wired connection that passes from the antenna through the turbine blade to the connection with the main shaft. At turbine blade’s connection with the wind turbine’s main shaft, the wired connection from the antenna is attached to a slip ring which, in turn, is connected to a radio unit

The Primary RF antenna is integrated within the turbine blade. In some options, particularly large turbine blades where the turbine blades are large enough that a person is able to stand inside, the integration may include mounting an antenna in that space inside of the turbine blade. In alternatives, particularly with smaller turbine blades where it would not support mounting an antenna internally, the antenna may be integrated with the turbine blade material. In the latter instances, the antenna is not exposed at the surface; at least some of the turbine blade material will cover the antenna.  In either instance, the RF antenna is formed in dimensions to the available space and/or shape of the turbine blade into which it is integrated. Irrespective of the manner in which the antenna is integrated into the turbine blade, the design does not have any effect on the aerodynamics of the turbine blades or their operation as part of the wind turbine

While turbine blades vary between 18 and 100+ meters in length, the RF antenna is typically located between 3 and 8 meters from the connection to the wind turbine’s main axle and center of rotation for clearance plus diversity. Generally large wind turbines utilize three blades as the most efficient, though the design is not limited to having this. Each RF antenna may correspond to operating on distinct frequencies and cellular formats from the antennae of other turbine blades of the wind turbine (i.e., supporting distinct cellular providers). However typically a wind turbine will support only one cellular provider, i.e., having all turbine blade antennae configured to support the frequency(ies) and/or format(s) of a single cellular provider

The primary RF antennas use the lower of frequency bands available with highest power and reliability to enable the widest area of service. The same antennas can be used with higher frequency bands also where possible, or these bands could have more directional antennas mounted on the pole below the wind turbine head, either way using carrier aggregation to still provide wide area service but with much enhanced localized capacity and bandwidth/speeds.

Cellular frequencies of operation (in USA) – many pros and cons for all:

• Licensed low band (< 1GHz)

• Licensed mid band (2 to 3GHz)

• CBRS 3.5GHz shared band, variable service as governed by SAS

• New bands in 4/7/8GHz will probably have portions licensed and shared

By far the best is a combination of 2 or more bands with carrier aggregation for the widest range along with highest capacity and best user experience. A multi-band solution with higher band sectored antennas below the nacelle is the preferred solution. Having sectored mid band (2 to 7GHz) antennas will have higher gain than omni antennas on the blades but with higher propagation losses real coverage will be less. But these higher bands would be used with carrier aggregation to just supplement the overall omni service nearer the tower with better performance with higher bandwidth, but further out will revert to just the low band service.

In addition with the blades spinning they will give less consistent service for mid band frequencies, when a blade is in front of an antenna service in that band might be restricted so will then just rely on the blade low band service. In extremes when there is no wind and the blades are stationary if they happen to be in front of some antennas these might be effectively unavailable, services will be maintained but lower bandwidth in a certain direction for some time

The effective coverage area, or range, of a typical wind turbine cellular site can vary a lot, but is really down to these 4 key factors:

• Frequency band of operation, higher frequencies don’t go as far due to atmospheric limitations

• Height, both of the antenna above the ground but also where the tower is located

• Effective power of radio units, this is usually governed by regulatory requirement to allow coordinated sharing and coexistence of service providers, and I might also include the effective gain of antennas

• Quality of service (QoS) required, as simple measures the desired signal strength or data throughput criteria, the higher of either effectively gives a smaller range

In summary using a low-band frequency with full power available on a normal site can give very good QoS service for over 20 miles or 30 km

The cellular system of the wind turbine may be powered by batteries charged by the wind turbine in which the cellular system is incorporated for continual operation even when there is no wind

In various options the antenna radio unit is connected to a microwave radio of any applicable band that communicates with another cellular base station site and to its core network. The microwave antenna is located on or near the wind turbine’s tower below the lowest extent of turbine blades so they do not interfere with the communication between it and the next site when rotating

Alternatively the system may communicate with other cellular base stations and core network via physical instead of a microwave connection. For example, a system may include a controller that communicates data over a fiber optic or wired connection, or a combination, or even satellite

Summary       

Systems provide very wide area coverage as generally on high sites and tall towers to fill in coverage in hard-to-reach areas and roads that normally wouldn’t be possible either due to citing regulations or not being economical so no need for new sites and associated zoning, regulatory approvals and thus no environmental or visual impacts

Much improved customer experience with seamless service and no dependence on limitations and expense of fill-in roaming or satellite coverage alternatives

Multi-technology capable so can be used for 4G, 5G and 6G when available, and any combinations. Can operate in any frequency bands, low band (<1GHz) preferred for best coverage along with mid band (2-7GHz) for capacity, and ORAN, VRAN, multi-operator, private network and neutral host compatible

Equally applicable for new wind turbine builds but also when doing upgrades such as replacing the blades which fatigue and are usually replaced every 10 to 20 years to prevent consequences

Can be used both inland and offshore, individual sites or in windfarms with highly reliability, low maintenance and very stable power from local batteries charged by the wind turbine

Scaled down versions can be used for localized wind turbines for industrial, residential and other areas as Small Cells for added coverage, capacity and in building penetration, primarily in higher frequency bands

Flexible connectivity with other sites and core network via fiber, copper, microwave or even satellite. And totally transparent and complementary to wind turbine primary role of generating clean energy

Ultimate green cellular mobile coverage solution for rural and difficult to cover areas

Patent pending - 63/651,895

Based in Arizona USA, for more information contact via info@microcellularsystems.com