Tag Archives: Lasers

Power Transmission Through Lasers

Wireless power transfer has considerable advantages. The absence of transmission towers, overhead cables, and underground cables is the foremost among them, not to exclude the expenses saved in their installation, upkeep, and maintenance. However, one of the major hurdles to wireless power transmission is the range it can cover. But now, Ericsson and PowerLight Technologies have provided a new proof of concept project that uses a laser beam to transmit power optically to a portable 5G base station.

Wireless power transmission is not a new subject to many. People use wireless power for charging many devices like earbuds, watches, and phones. But the range in these chargers is short, as the user must place the device on the pad of the charger. This limits the usefulness of the wireless charging station for transmitting power. Although labs have been experimenting with larger setups that can charge devices placed anywhere within a room, reports of beaming electricity outdoors and for long distances have been rather scarce.

PowerLight has been experimenting with wireless power transfer for quite some time now, and they have partnered with Ericsson, a telecommunications company, for a proof of concept demonstration. Their system consists of two components, a laser transmitter, and a receiver. The distance between the transmitter and receiver can vary from a few hundred meters to a few thousand meters.

However, unlike a Tesla coil, the PowerLight device does not transmit electricity directly. Instead, at the transmitter end, electricity powers a powerful laser beam, sending it directly to the receiver. In turn, the receiver uses specialized photocell arrays to convert the incoming laser back into electricity for powering connected devices.

Such a powerful laser-blasting through the open air can be a dangerous thing. Therefore, PowerLight has added many safeguards. They surround the beam with wide cylinders of sensors that can detect anything approaching. The sensors can shut off the beam within a millisecond, if necessary. In fact, the safety system is so fast that a flock of birds is not affected when flying through the laser beam, but there is an interruption at the receiver.  To overcome such fleeting interruptions, and cover longer-term disruptions as well, the PowerLight system has a battery back-up at the receiver end.

PowerLight is using their system to power a 5G radio base station from Ericsson, that has no other power source connected to it. The base station received 480 watts from the transmitter placed at a distance of 300 m. However, according to the PowerLight team, the technology can send 1000 watts over a distance of over 1 km. They also claim there is room for future expansions.

Wirelessly powering these 5G units could make them more versatile, as they will then become portable, and capable of operating in temporary locations. This will also allow them to operate in disaster areas, where there has been a disruption of infrastructure.

According to PowerLight, their optical power beaming technology may be useful in several other applications also, such as for charging electric vehicles, in future space missions, and in adjusting the power grid operations on the fly.

How Are Industrial Lasers Cooled?

There are several varieties of industrial lasers. Some lasers, such as fiber lasers, have specific arrangements that enable spreading the heat they generate over a larger surface area. This arrangement gives fiber lasers better cooling characteristics over other media. Other lasers need extra cooling arrangements to remove the heat they generate. For example, ion lasers generate extreme heat when active and need elaborate cooling methods. Other lasers, emitting energy in the microwave and far-infrared region of the spectrum such as carbon dioxide lasers are immensely powerful, and cut hard material such as steel. The laser essentially melts through the material it focuses on. The problem is these industrial lasers have a limited surface area from where to exchange heat.

Although people traditionally use thermoelectric modules as heat exchangers, their efficiency has always limited their application. Now, thermoelectric modules are available which exhibit high heat flux density and are able to achieve higher heat pumping capacity compared to standard thermoelectric modules.

For instance, the UltraTEC series of thermoelectric modules from Laird has heat-pumping capacity of up to 340 Watts, which is fully adequate to cool applications such as industrial lasers that offer only a limited surface for heat exchange.

Industrial laser applications are numerous, including drilling, additive manufacturing, micro machining, welding, and cutting. Irrespective of the application, industrial lasers generate tremendous amounts of heat, which needs to be quickly and effectively removed to allow the laser to perform long-term and properly. Cooling lasers efficiently has always been a significant challenge for the industry.

Typical methods of cooling include transferring the excess heat by conduction or convection. Air may be used to remove the heat directly, or the heat could be transferred to a coolant, usually circulating water. The water carrying the heat is then circulated through a chiller or any heat transfer system. However, these arrangements depend on the system size and configuration, and can be expensive, complex, and noisy.

The UltraTEC series of thermoelectric modules offers excellent heat pump density, and allows precise temperature control. In fact, under steady state conditions, temperatures can remain within ±0.01°C. As these thermoelectric modules offer solid-state operation, these cooling solutions do not produce noise or vibrations. Moreover, they are available in multiple configurations, making them simple to implement.

Any laser system needs to be accurate and repeatable. Stability of the laser system is highly dependent on balanced, controlled cooling. The advantage of using UltraTEC thermoelectric modules for cooling is they can deliver highly reliable cooling solutions under conditions where the laser is in continuous use and even when cycling at high powers.

Laird assembles UltraTEC thermoelectric modules from Bismuth Telluride semiconductor materials. They use aluminum oxide ceramics, which are thermally conductive. This makes the UltraTEC thermoelectric modules capable of carrying high currents that are necessary for large heat-pumping applications. For instance, with Qmax rating of 340.6 W at 25°C, these thermoelectric modules can operate continuously up to 80°. This adequately ensures that the laser system will never overheat when being cooled by the high heat pump density UltraTEC series of thermoelectric modules. These modules are RoHS compliant and DC operated.