I just found a company that could revolutionize everything from Solar panels, home batteries and Electric vehicles. And no I’m not talking about batteries, which I talk about a lot. I’m talking about inverters. The magical devices that convert Direct current found in everything from solar panels, wind turbines and batteries, into Alternating current, which is used in electric motors and our homes. Current inverter efficiencies top out between 95-99%. But a publicly-traded company called Hillcrest Energy, ticker symbol HLRTF, says they just figured out the holy grail for inverters, a technology called Zero Voltage Switching, and say their inverters are 99.7% efficient. That difference might not sound that big, but it is an absolute game changer. So how does it work, and how impactful will this breakthrough be? Let’s figure this out together, I’m Ricky and this is Two Bit da Vinci!
Teaser
Huge thanks to Hillcrest Energy Technologies for partnering with us to help us make this episode.
I had the pleasure of chatting with Harald Hengstenberger, an electrical engineer and member of the Hillcrest Energy Technologies Team. obviously my first question for him was why is Zero Voltage Switching considered the holy grail for inverters and how was his team able to solve it.
[insert intervew (04:21.663)] “This is a question we are asked again and again and it’s very hard to answer actually. Zero voltage switching is known from DC -DC converters as well the principle of a ZVS inverter is not completely new. But you know sometimes you need the right chips that took a very long while, you need the right microcontrollers and maybe you as well need the right team and the right time to do that.
I believe a few things came together at the right time.”
A key element to this stock market opportunity is that the company has patented IP to protect this transformational technology and that it has spent $20M developing it, yet its market cap is only slightly over that amount! But before we talk about how big an impact this tech can have, let’s talk about how it works.
Background
If we measured the voltage of this solar panel on an oscilloscope, this is what we’d see. A constant value of around 35V, direct current.
But if we did the same thing on one of the legs in our home electrical panel, we’d see something very different. The voltage would be 120V, but you’ll notice that the voltage varies and forms a sine wave. This is alternating current. And it’s why the solar panels atop our roof need one of these, an inverter.
Inverters are needed in everything from home batteries like this one, or this one. Inverters are also needed to invert the DC from EV batteries into AC for AC motors.
Now if we take a battery and swap the positive and negative ends, back and forth, we get a square step wave that looks a bit like our AC sine wave.
But an inverter does this with a series of switches called IGBTs (Insulated-gate bipolar transistor) in a clever arrangement.
Instead of swapping the battery terminals, we can create a system with 4 switches and a controller to control them. If we close switches 1 and 2, the current flows in the forward direction through our AC Load. to switch the direction, we just open switches 1 and 2, and close switches 3 and 4. Now current flows through our AC load in the opposite direction.
Using a technology called pulse width modulation, we can create a smooth sine wave, without actually changing the voltage. By pulsing when and how long the switches are open and closed, we can break down one complete cycle into segments. Starting with a short duration pulse, followed by a series of increasing duration pulses, reaching a maximum, then shortening them back again.
Now if we look at the average value in each of these segments, we begin to see our sine wave. And the more segments we create the smoother it’ll be. This is referred to as the switching frequency and we’ll get back to that in a moment.
The two main sources of inverter energy losses, comes from conduction losses, and switching losses.
Conduction losses happen in all electronic components and is a function of materials like copper, a very good but not perfect conductor. To address conduction losses, technologies based on Si, such as super junction MOSFETs, are used in modern inverters.
The big breakthrough that Hillcrest Energy Technologies made addresses the second type of losses that come from switching.
Now switching doesn’t actually happen instantaneously; it takes a very small amount of time like 100 ns.
So the voltage graph during the switch actually looks like this.
If we look at the voltage over the switch as it opens, it rises over that switching duration. The current drops to zero as the switch is fully open. Since power is I*V (current x voltage) the power is zero when the voltage is zero here, and when the current is zero here. So then our switching losses happen in this transitory period in this area under the current and voltage curves.
This power is lost as heat during the switching process, and results in lower efficiency, and added heat that the inverter needs to dissipate. And remember that this switching loss happens each and every time the switches change state, so it scales up with higher switching frequency.
This is the engineering trade off inverters have to make, to increase performance with higher switching frequency, while minimizing losses and waste heat. Modern inverters switch around 10kHz or 10,000 times per second, which has historically been a sweet spot.
We can reduce switching losses by either reducing the voltage or current during switching. This is called Zero Voltage Switching, and Zero Current Switching respectively.
While this is a concept that has been pursued for some time, Hillcrest Energy Technologies says they’ve done it, using novel control software algorithms.
[interview Harald Hengstenberger (03:15.359)]
“Okay, a hard switching is an inverter which switches a chip hard. That means it turns it on no matter what happens and it turns it off the same way. We use a ZVS technology that means zero voltage switching. We turn on or turn off the switches when the voltage across the switch is zero or the current is zero. Therefore, knowing that the electrical power is the product of current times voltage. If one of both is zero, the power is zero in that moment.”
Here are some of the benefits that this provides
- Material elimination of diode reverse recovery current spikes.
- Reduction of Overshoot – Protects devices, reduces ringing significantly and therefore EMI.
- Material elimination of risk associated with the Miller Effect.
Harald Hengstenberger (09:00.255)
“Yes, due to the fact that we have a soft switching behavior, we have a very smooth transition, a very slow, I call it slow even if it happens below 100 nanoseconds. OK, but it’s extremely smooth. It has no ringing, no overshoots. These overshoots and this ringing during the switching processes causes EMI. And that’s a disturbance that you can measure everywhere in the lines that’s the conducted.
EMI more or less, which every other device in the vehicle or connected to the inverter is seeing. And the inverter usually is the main producer of EMI. At the same time, the EMC is just how you react, how immune you are to external EMI, more or less. Therefore, the inverter usually doesn’t have an issue with the EMC.
because the other devices do not produce the EMI.”
Electric Vehicles
Accordingly to Hillcrest Energy Technologies, based on a battery pack size of 75 kWh, weighing 2,000 lbs. at a cost of $132/kWh
Their inverter could result in up to a 15% reduction in size of a battery pack! And result in efficiency gaines of up to 13% at the motor, during partial loads. Remember that most inverter ratings are at peak outputs, and when you’re cruising around the city at 40 MPH, you’re only using a very small portion of the available power.
Interestingly, car OEMs have been more interesting in what this technology means for EMI, because it results in up to a 50% reduction in the size of DC-link capacitors, and in EMI shielding and filters in the system.
This could lead to up to 300 lbs in weight savings from the battery pack, up to $1500 in battery costs savings, and an over a $2200 reduction in the cost of an EV, just by switching to the ZVS inverter.
What’s really amazing is that they achieve this not with super expensive rare materials, but with control algorithms and software. They believe their inverters can be at price parity with today’s inverters, leading to a no compromise solution.
Here’s a look at some internal testing performed by Hillcrest Energy on traditional hard switching inverters vs. their ZVS inverter.
As the switching frequency increases, you’ll see the hard switching power losses increase pretty dramatically. But the ZVS inverters can ramp up switching frequency with minimal effects.
But it’s not just electric vehicles! This next part is important for fans of the company and potential investors to truly understand…
On a 250MW solar farm, if we increased inverter efficiency by 2%, that would result in an additional $13.2M in revenue over the lifetime of the plant.
As the world moves to more renewables like wind and solar, batteries and EVs the global inverter market is going to increase in a big way.
Hillcrest projects that the global inverter market will be $117B by 2029.
Now these are early days, and there will be further testing and development required. But a key next step is joint partnerships, like the recent one they signed with Ocean Batteries to deploy ZVS inverters in grid connected energy storage solutions.
This is a really exciting breakthrough and one I’m going to be watching closely. I’m going to try to reach out to the team to get some access to tour their facilities, and get some hands-on experience with their ZVS inverters. So definitely subscribe, and like this video, because you won’t want to miss that.
If you’re curious about Hillcrest Energy Technologies, which trades in the U.S., with the ticker symbol HLRTF, and want to learn more about the company, or their stock, read their reports or white papers, we’ll put links to all of that in the video description. You could also reach out to the co-founder of the company, who serves as CEO, Mr. Don Currie, and actually speak directly to him, like many shareholders do.
And until next week, check out this video next, I’m ricky with Two bit da vinci thank you so much for watching!