New Zealand's wireless power transmission: Your questions answered

Yesterday we covered the news that New Zealand's second-largest electricity distributor has signed a deal with startup Emrod to trial long-range wireless power transmission. Today we follow up with an interview with Emrod's founder, Greg Kushnir, to talk about the deal, the technology, safety and redundancy concerns, the efficiency of the system and whether it can be used to transmit power back to Earth from a space-based solar array.

What follows is an edited transcript.

New Atlas: Congrats on this deal you've signed with Powerco. It sounds pretty significant.

Greg Kushnir: Any market traction with a new technology is significant. I think it's been a huge leap of faith on behalf of Powerco.

So Microwave energy transmission has been possible for some time. What are the advances you guys have made?

You're absolutely right. Transferring energy with microwaves has been around for decades. In the 70s, NASA showed it could support a helicopter drone in the air, charging it with microwaves from the ground. It's been around for a while.

What's changed in the last few years is mostly metamaterials technology. New materials that allowed us to convert the energy back into electricity very, very efficiently. That was what made it viable for commercial use. Before that, it's been around, but mostly used for military purposes.

So materials that are synthetic, man-made, and when you have waves, either acoustic or electromagnetic, hit them, they react like a new type of material. And you can design them to do all sorts of things. Acoustic metamaterials can be very handy for sound absorption in audio studios.

Electromagnetic metamaterials do a few things; you can incorporate small designs in them so they can absorb electromagnetic radiation and turn it into heat, or electricity, or make it go away. It's essentially stealth technology, that's what it's been used for in the military.

The stuff that makes things invisible to radar?

It's the same category. We're using somewhat different technology, but it's the same category of materials.

Is it the structure, or the component metals? What has enabled this?

I think what enabled the really quick dash we've seen in the last few years is better computer modeling. When you can model those things properly without needing to build and test all the time, that's what provided the big boost. More computing power, better software, more universities involved in that research.

So the prototype you're building for Powerco, it'll transmit 2 kW, is that right?

Somewhat more than that. A few kilowatts, but that's really only limited because of our test facility. We can technically deliver quite a lot more.

What are your current prototypes transmitting?

Just a few watts. Our current prototype is relatively small. It transmits about 40 meters (130 ft).

How big will a final antenna unit be?

I don't have a simple answer for that. The size is dictated by the amount of energy you want to transfer; larger energy, larger surface. Also the distance; the longer the distance you want to traverse, the larger the surface you'll need.

Mind you, you don't need to do a huge hop in one go. That's probably more limited to islands and offshore wind farms where you have pretty long distances to deal with. For regular terrestrial use we can use our relays, so you only need line of sight between each element.

The relays are essentially lossless. The loss there is almost zero. They don't require any power, you can think of them almost like lenses; they refocus the beam. So you need line of sight between each component but you don't have to be able to see from the transmitter to the rectenna.

But to give you an example, a one-square-meter (10.7-sq-ft) transmitter could send about 10 kW for about 10 meters (33 ft), but a 40-square-meter (430.5-sq-ft) transmitter could give you about a 30-km (18.6-mi) range, which is much more than we'd need for the vast majority of applications.

So the relays are lossless, what's the efficiency of the whole system like?

The efficiency of all the components we've developed are pretty good, close to 100 percent. Most of the loss is on the transmitting side. We're using solid state for the transmitting side, and that's essentially the same electronic elements you can find in any radar system, or even your microwave at home. Those are at the moment limited to around 70-percent efficiency. But there's a lot of development going into it, mainly driven by communications, 5G and so on.

So that's the main limit on our efficiency. The rest of the system going through the air, relays, rectification, is pretty efficient.

So the total system is sitting around that 70-percent mark then?

Pretty much, it depends. You can go a bit higher or lower depending on which frequency you use, and we use a range of different frequencies depending on the exact scenario; sometimes you're happy with larger, cheaper antennas, sometimes you're happy with a smaller, less efficient antenna, but yes, that's about the level we're at.

How does that compare to the efficiency of copper wire?

There's always some loss in copper wires. Traditionally, the distributors mitigate that by increasing the voltage, so you get the high voltage lines that traverse longer distances. The loss there is not terrible. The numbers coming out of the States tend to report losses around 10-15 percent, generally speaking.

Obviously in some scenarios it's far lower than that. I think we stack up fairly well. And when you think about solar panels, and where they started four decades ago, they had an efficiency in the single digits. It took decades before they became economically viable without government subsidies.

We're there from the get go. There are quite a few scenarios where it's already an economically viable way to transfer power. I mentioned bodies of water, but it's also through difficult terrain, mountains, valleys, forests. Especially if it's a national reserve, you don't want to cut out big chunks, put in pylons and keep coming back to cut the trees back.

So in those situations we're already economically viable. Having said that, we don't foresee in the near future a situation where we could say all copper wire can be replaced by wireless. Inherently, it'll have lower efficiency levels. It's not about replacing the whole infrastructure but augmenting it in places where it makes sense.

Obviously, these days any kind of wireless technology seems to be a bit of a hot button topic with, shall we say, a vocal minority of people. Do you expect a lot of pushback?

Yeah, you're right. We do expect some pushback. But luckily, it's pretty easy for us to demonstrate that our environmental footprint is far, far lower than that of regular lines. The energy is beamed between two points, point to point. There's absolutely nothing around it. No waves, no radiation, no impact.

It's quite easy to demonstrate that. And more than that, we have a laser matrix, so we make sure that the beam always touches nothing but clean air. And even if we didn't use that laser matrix, you'd have to linger quite a while in that beam to get a little bit of heating effect, say one degree hotter.

Unlike 5G for example, 5G spreads everywhere. It inevitably immerses and hits people. Our beams don't hit anything but clear air. So I think we have a pretty easy job in terms of explaining why our technology is safe and environmentally friendly. But we'll have to address it, you're absolutely right. There's always going to be some pushback.

The science doesn't necessarily carry a whole lot of weight in these arguments.

You can't please everybody, and I don't think that's our job.

So even if you didn't have the laser shutoff, you could stick your hand right in the middle of a high power transmission and leave it there for several seconds before you'd feel anything?

Yeah. It really has to do with the frequency we're using. It's not laser, it can't punch a hole through your body. The waves are relatively long, it's in the Industrial, Scientific and Medical (ISM) band, and there's a good body of research about the effects of these kinds of beams on human tissue.

The second thing has a lot to do with the power density. It's not just how much power you deliver, it's how much power you deliver per square meter. The levels of density we're using are relatively low. At the moment it's about the equivalent of standing outside at noon in the sun, about 1 kW per square meter.

Obviously we'll increase that, but the levels of power density will still be quite low. I think that's one of the advantages we have in terms of health and safety.

And also the laser cutoff system, which is pretty cool.

I have to admit the laser cutoff system is pretty standard, nothing too sophisticated there.

OK. What happens when that cuts off, total blackout at the other end?

No. Depending on the size of the antenna, we can cut off specific parts. There's a whole lot of transmitting elements. We can cut off just the ones that are blocked by an object. So unless you have a helicopter hovering exactly in the path of the beam, any transient object will not have a significant effect on the power levels that are received on the other side.

Having said that, it does make sense to incorporate a battery on the other side if you have mission-critical applications like we're looking at with hospitals and things like that.

So you've got some traction with Powerco, any other deals in the pipeline?

We do, but I don't think it's right for me to discuss them before they're signed. But there are quite a few in the pipeline.

Right. So how did you guys get out onto this first?

Good question, I don't have a good answer. I've been looking at this for about a decade now, as part of a search for high-impact technologies that would yield the most good for the most number of people. One of the main focuses of my search was energy, obviously.

If you look at energy, there's a lot of good work being done in generating energy in a sustainable manner. We've achieved wonderful things, I didn't see any contribution I could make there with my limited resources. The same goes for batteries, a lot of battery progress has been generated by EVs over the last decade or so. I can't compete with Sir Dyson when it comes to R&D!

So I had a look at transmission, and it didn't take me long to realize that very few have looked at transmission. We tend to think about it as that thing that comes from the socket in the wall. But that's the same way we used to think about phones, they were connected to wires as well. So I had a little thought experiment about what could be achieved if power was wireless.

Obviously I'm not the first to think about that; Tesla himself looked into it more than 100 years ago. So I don't know why we're the first, but that's how the process started for me. I'd be more modest and say we're not the first to think about it, there have been attempts made around the world, by the Japanese space agency, NASA has had an active program for decades now. But their goals are different, they haven't looked at efficiency so much because they're not looking at commercial use.

We're not the first, but we're the first ones to have a commercially viable solution. Let's put it that way.

You mentioned the space agencies. Spitballing way into the future, is this the sort of thing that could conceivably get power down to the ground from a space solar array if you were able to aim it precisely?

It's more doable than people would think. The only major obstacle at the moment I can see is actually putting a rigid enough structure in space. It has to be quite large to beam all the way from a geosynchronous position 36,000 kilometers up. Any movement in an antenna that would probably be over a kilometer (0.62 mi) wide would destroy the efficiency.

So you'd gain, say a factor of five by harvesting that energy in space, but then the amount of money and effort you'd need to put something like that in space ... It's just easier and cheaper to build more solar arrays on the ground. But yeah, when we have cheaper space payloads, it's not that hard to achieve that.

Read more about Emrod's wireless long-distance power transmission technology.

Source: Emrod