by Raghu Belur
When is the last time you removed the side panel of your computer and replaced a network add-in card? When is the last time you installed an inverter on a residential solar system? These are basically the same question, only separated in time. In 2002, the add-in card question would have gotten you an answer; it seems unlikely today. Similarly, in relatively short order, the inverter question fill face the same fate. It’s important to note that the computer add-in card example is not arbitrary; those kinds of devices disappeared for the same reasons that the inverter is about to disappear.
I am the co-founder of an inverter company. Is this view of the inverter heresy?
It really comes down to beliefs and decisions from ten years ago, at which point the fate of PC add-in cards was already clear. Those beliefs still are: distributed energy resources should be based on a distributed architecture concept, consisting of hardware, communications technology, and software. The key decisions were: to use a systems approach (where everything works together), and using microelectronics instead of old-school approaches to energy conversion (which are locked into perpetually higher fixed costs).
The PC industry experienced the transition from many discrete devices to monolithic, integrated, multi-function devices. Semiconductor IP from previously discrete components like network cards was integrated into the latter, making a rapid reduction in part count, system complexity, and cost possible. Microinverters use this same semiconductor technology. Also like PC components, microinverters can be updated via remote software updates, which allows the rapid integration and roll out of new features. Semiconductor-based microinverters also follow the steep cost reduction curve we know from the computing world. As new generations of chips are ‘spun’, the cost of those chips is reduced.
The next great leap forward is now under way, and it centers on further integration with that other bit of semiconductor technology on residential rooftops: the module.
What does this mean for inverter companies that made the decision to use traditional means? They cannot easily integrate with solar modules. Just as with Ethernet card vendors who could not or would not pursue the inevitable integration path, inverter manufacturers that have locked themselves into technologies that cannot follow Moore’s Law will soon be in trouble. In the case of AC modules, everyone from distributor to installer will benefit from: fewer SKUs, fewer carries onto the roof, less copper, no electrical labor on the roof, and significantly less cardboard and packaging waste at the installation site, thereby making clean energy even cleaner. The installer also saves up to 12 work steps during the installation process with integrated AC modules, which reduces one of the leading drivers of residential solar installation costs, labor. Even if everything else remains comparable, this list of advantages is too long for the industry to ignore.
Companies that are dependent on selling dedicated, standalone inverters are in trouble. Companies that have not have diligently invested in R&D, not uncommon in the inverter space, and that don’t have a path to further integration should be worried. A modern, future-proof home energy system includes generation, storage, and management, backed by intelligence at each end-point. This system must have software that can updated without rolling a truck, and supply performance metrics recognized by
industry standards bodies. Finally, the modern home energy system must provide rich data and apply big data analytics to drive insights about how solar must behave within the grids it occupies.
Taken together, the elements above point to a very complex system. The trick, however, is making sure that we do not burden the installer or the homeowner with that complexity. With the advent of AC modules, solar is becoming even more plug-and-play. That is another term borrowed from the computer industry, and its impact on solar will be no less profound than USB was on the PC industry.
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Thus argument laws clarity in the context of fully-integrated residential instalkations. Site-based storage battery technology is still DC. AC panels installations with external batteries will therefor still require both external rectification and inversion. With storage costs per kWh still much higher than panels yet poised to fall more rapidly than panels AC microinverters can easily become an economic handicap unless the battery is also integrated into the inverter.
CORRECTION: “argument lacks clarity”.
Damn you, autocorrect.
When was the last time you left your computer tower or your notebook computer on a 150 degree roof?. Stand alone or as they are known string inverters will always be the smart choice for for systems that will be reliable for 20 to 30 years.
(Coming from a veteran 20-year solar installer) I completely agree about the roof atmosphere conditions – talk about a physical reality!
This article is just a typical Enphase spin that we were hearing (5) years ago. (when their rooftop units were failing left and right). I got so tired of going out to my (30) different Enphase installations to swap out their “inevitable” switch from a string inverter” units that two years ago I swore that I’d never use them again.
The realities of physics are simply never going to allow all of those electronics to survive time. I don’t care if Enphase promises 25-year warranties, because I don’t trust that they will be in business that long. Check out their near bankruptcy a year or so ago, and how they are now just on “other people’s” loan money life support right now…
This company is losing money qtr after qtr for several years in a raw, I don’t trust their ability to read the market
All our home devices are DC nowadays. The EV is DC. Home energy storage is DC. The panel is DC. With the advent of distributed energy and P2P energy trading transfer prosumers will be rewarded for consumption at point of generation or minimal xfer and losses. I would argue AC inversion in general is more like dos when the GUI came along. So why do we need AC again? This guy is talking his very ill financial book.
Power that comes in from the power company is AC power. Even the electronic devices in a home that run on DC have a transformer that plugs into an AC socket. The only benefit to stay DC was if you were not attached to the grid and were backed up by a DC battery. Even then, the DC battery will have to convert to AC to feed power to the house, because much of the house is not DC power (lights and most major appliances). AC panels make the best sense in most cases.
Read above. Most light and power circuits should be low v DC. They are actually perfect for 48v or less. Your statement is not correct . AC transmission is for long range transport due to better loss factors for centralised gen. That is changing. Fast.
Many good points. As an electrical engineer of 50+ years, and recently into solar, including building my own ground mount system 6 years ago, I think the string inverter is the best overall choice, but would consider micros for ground mounts. ACDC’s comment has merit, but I would not change to dc branch circuits because of voltage drop issues. Increasing wire sizes only uses more copper.
I am with Philip. As an engineer with 35 years in disk drive and power electronics, I see 60 Hz AC is here to stay. People who say we should “standardize” on DC can never pick the voltage. Should it be 400 for low loss household distribution or 48 for safety, then most devices operate from 12, 9, 6, or 5 volts. In almost all cases conversions are required. There is distribution to consider; local distribution is from 12,000 to 36,000 volts. With low-cost DC to DC converters being nonisolated, you have huge ground reference problems.
Let’s separate the financial from the technology, if the technology is sound then somebody will keep it going.
I have replaced many String Inverters in the last few years that were under 10 years old, not a very good argument for String Inverters.
I have installed many systems in Northern California with Micro-Inverters in the last 8+ years, and so far have not had a single problem. Maybe I am lucky so far, but I think technology is sound and improving.
As a mechanical engineer with over 31 years of experience, I believe in emphasis on product development for today’s world. Sound engineering and testing will produce reliable and safe product. I think Enphase Energy has the right focus for these areas.
I agree that the cost for energy storage is too high and doesn’t compute for a good ROI with today’s prices. It has a long way to go.
I don’t doubt that integrated microinverters will be a standard option offered with solar panels in the future, but the question is whether it will be small percentage of all solar panels or the vast majority. I have no doubt that Integration of the microinverter in the solar module will happen to some degree. It makes sense because an integrated microinverter will cost less, because it will require less materials in the case and less material in the circuits because it has a narrower range in the voltage and amperage of the panel. It costs more to make a generic microinverter that fits everything from a 220 to 400 watt panel.
However, there will also be many solar installers who will refuse to use integrated panels/inverters because the inverter is more likely to fail than the panel and the inverter is worth less than the panel. If the integrated unit has a 25 year warranty, then maybe people will take the risk, but they need to be convinced that the company will still exist 25 years into the future. If the company making the inverter is ABB, people might be willing to take that risk, but if it is a small company like enphase which isn’t profitable, then many solar installers are going to be skeptical.
The second thing to keep in mind is that the price of battery technology is going to keep falling and home storage is going to become a more economical proposition in the future. If using a home battery, then you don’t want your panels to have integrated microinverters. A dramatic breakthrough in battery tech could destroy the market for microinverters. Looking a recent developments and the 7% annual improvement in Ah per dollar in lithium batteries, it looks inevitable that home storage is the wave of the future, but there are theoretical limits to the amount of energy that lithium ion can store. Lead/acid batteries simply degrade too fast and they aren’t going to get much cheaper. Lithium ion batteries are going to hit a price floor because of the price of lithium, cobalt, nickel, copper, and manganese will rise in the future as these metals become rarer. The real question is whether home batteries can be made out of common elements that are dirt cheap like sulfur, aluminum and iron. If so, then home batteries will dominate and there will be little market for the microinverter in the future. However, I think it is more likely that that home batteries will get cheap enough for 10%-20% of homes to install them, but not so cheap that they undercut the cost of grid electricity.