by Jeff St. John
May 11, 2018

Greentech Media’s annual Solar Summit conference is increasingly becoming a “solar-plus” conference, as befits an event covering a subject so central to a much broader shift in energy technology, economics and policy. 

We’ve already added the day-before Solar Software Summit to the event’s agenda to highlight the critical subset of the broader industry. And, of course, energy storage has become an integral part of the solar equation, meriting its own dedicated tracks at last week’s two-day event. 

But solar power is also central to the grid edge, both as the spearhead technology to a much wider array of distributed energy resources, and as the biggest disruptor to utilities, grid operators and energy regulators. 

Energy storage is often the primary grid edge technology under consideration, along with electric vehicles, home energy controls, advanced building energy management, and, for customers in storm-threatened areas, emergency backup power. 

This month’s Solar Summit featured a lot of discussion on these topics, along with a healthy list of audience questions compiled and ranked by our online Q&A system. Since our moderators and panelists weren’t able to fully answer all of them all on stage, we’ve compiled some of the more grid edge themed questions, and provided some answers, both from panelists and our own observations on the topics at hand. 

Solar as a platform: Fitting solar with EVs, IOT, HEMS and other fun acronyms

On this panel, Greentech Media’s Julian Spector explored the intersection of solar PV with a panoply of emerging behind-the-meter technologies, along with executives from solar design software firm Aurora Solar, home energy storage and management startup ElectrIQ Power, and microinverter and optimizer giant SolarEdge. Here are some of the audience’s top questions, answered. 

Q: What will be the most critical layer of software platform to integrate the current and emerging technologies we are talking about?

The phrasing of this question allows for some variation in responses, based on the emerging technologies under discussion — and each of the three panelists had his own thoughts, based on each company’s particular expertise. 

Samuel Adeyemo, chief operating officer at Aurora Solar, noted that his company’s raison d’être is to “know everything there is to know” about a prospective solar customer without getting up from one’s desk. That requires lots of data, ranging from the standard energy-related metrics to satellite and lidar data to determine rooftop shading at individual addresses. 

Making sense of all of this data will require artificial intelligence to “detect things faster and more automatically than we have in the past,” he said. But the capabilities of AI and machine learning will need to be tied with the know-how to present solar parties with output that’s directly applicable to solving their most expensive problems, he said. One example he cited was a recent survey his company conducted, which found that about 85 percent of solar installations end up having “some sort of change order” applied to them — a source of extra cost that could be an early target for AI enhancement. 

Michael Rogerson, North America marketing director for SolarEdge, highlighted his company’s new cloud-based virtual power plant management platform as a critical new software layer. “SolarEdge is becoming a smart energy company,” he said. While the company has its own inverter-integrated energy storage and EV charging offerings, it’s increasingly looking to its module-level power optimizers as data and computing assets for distribution utilities, energy retailers, and other parties. 

Chadwick Manning, co-founder and CEO of ElectrIQ, noted the potential for home solar-plus-storage systems to make use of non-intrusive load monitoring — also known as energy disaggregation — at scale. Energy disaggregation can turn whole-building electrical load data into discrete information down to the individual appliance and plug level, an invaluable resource for data crunching by utilities, energy services providers and others.

Q: In what regions of the U.S. is solar+storage currently savings-positive for residential systems?

We'll answer this question with a data dump from GTM Research, which has been tracking the quarter-by-quarter trends in U.S. residential energy storage markets. According to the 2017 Year in Review edition of the GTM Research-Energy Storage Association report U.S. Energy Storage Monitor, the number of residential energy storage system installations tripled from 2016 to last year, with the fourth quarter of 2017 alone outpacing all of the prior year. 

But almost all of this rapid growth was confined to two states. The first is Hawaii, driven by the country’s highest electricity prices and the state’s Customer Self-Supply Program, a replacement for net metering. The second is California, where the state’s Self-Generation Incentive Program, with its carve-out for residential storage systems, has helped drive growth. 

But other states and utilities are trying out models that spread the costs of batteries and power electronics over time. Sunrun, which has taken the first-place U.S. solar installer crown from Tesla-SolarCity, is expanding its BrightBox storage product to Arizona, Nevada, New York and Massachusetts. In Vermont, utility Green Mountain Power is offering Tesla Powerwall batteries (and SolarEdge inverters) to customers to be paid for in monthly installments through their utility bills, in exchange for being able to use them to manage system needs. 

Key trends in solar inverters and power electronics

This panel, moderated by GTM Research senior solar analyst Scott Moskowitz, largely centered on bread-and-butter issues like price competition, performance improvements, and the shift from central to string inverters for utility-scale solar projects. 

But it also covered the growing number of applications for inverters on the modern grid, from managing the interplay of batteries and building loads behind the meter, to interfacing with beyond-the-meter grid control or energy trading platforms. 

“There’s a single point of connection to the grid,” said panelist Levent Gun, CEO of solar optimization startup Ampt. “That control interface across that connection is getting more and more complicated, more and more interactive. And with storage, it’s going to become even more complicated.” 

Mahesh Morjaria, vice president of PV systems development at First Solar, noted that more advanced solar inverters are capable of providing a number of grid services on their own, as First Solar has demonstrated with NREL and California grid operator CAISO. 

While First Solar is “mainly driven by cost today” in terms of choosing inverter partners, it’s also demanding these kinds of functionalities, he said — a point that led Moskowitz to joke that inverter makers are being asked to charge less and less for increasingly capable machines. 

Q: When will the benefits of wide bandgap materials outweigh the costs? Or are efficiency and reliability already good enough? 

This audience question delves into another key area for improvement in inverter and power conversion technology. Silicon carbide (SiC) and gallium nitride (GaN) each offer distinct advantages over traditional silicon, with SiC largely better suited to heavy power applications such as inverters for solar PV, batteries or EV chargers, and GaN for more high-value, mid-voltage applications such as radio frequency, radar or military scanners and jammers. 

In The Global PV Inverter and MLPE Landscape, a GTM Research report published late last year, Moskowitz noted that SiC and GaN will help provide cost-competitive alternatives in lower-voltage, high-performance applications over the next several years. Cree’s recent €345 million ($425 million) acquisition of Infineon Technologies’ Radio Frequency Power business gives the company leading position in SiC next-generation inverters, as well as EV charging and, potentially, EV drivetrains. 

But the primary mention of wide-bandgap materials during the panel came in response to Moskowitz’s question about First Solar’s decision to postpone plans to use medium-voltage DC architecture in its future utility-scale solar projects. According to First Solar’s Morjaria, rapidly falling inverter and power electronics costs drove the company to rethink an approach aimed largely at cutting those costs. But, as silicon carbide devices become available at reasonable costs to manage the higher voltages involved in MVDC, the architecture is “more likely not only to be more cost-effective, but more capable,” he said. 

Q: How hard should the industry be working on developing a DC grid to reduce losses and simplify the grid further?

This was the most popular question for the panel, according to our Q&A system’s tally of audience votes. It's also one that proposes a technology solution to solar power that more or less does away with the inverter altogether, at least at the behind-the-meter scale. As such, it didn’t get picked up in the on-stage discussion. 

The world’s power grids and building wiring are built on alternating current, leaving an enormous investment in infrastructure that’s unlikely to be replaced by a direct current alternative in any but the most distant future. 

But DC-only systems do make sense in certain circumstances. Data centers are an obvious target, given that the costs of going all-DC may be balanced against the efficiency losses and waste heat involved in AC-to-DC conversion. Another potential, though more speculative, target is homes that are designed to generate most of their electricity with rooftop solar PV and battery storage, and use most of it to charge DC-powered electronics. 

As for the grid, high-voltage direct current is an integral part of many systems, transmitting power across long distances, underwater, or through corridors too narrow for AC transmission systems. Large-scale HVDC projects are announced with some regularity — in February, Korea Electric Power Corporation picked GE Power to build a $320 million, 4-gigawatt high-voltage DC transmission link from the east of the country to the capital, Seoul. 

The increasing share of wind and solar power on the grid has prompted some studies into the relative value of DC versus AC transmission infrastructure. Projects like building a network of HVDC “highways” across the U.S. could offer massive efficiency benefits — but would also require trillions of dollars of new investment on top of the existing transmission network. 

Want to binge watch all of our panels from the Solar Summit? We've got you covered here.