Span Electric Panel with Arch Rao

Span Electric Panel with Arch Rao


With the upcoming wildfire season in California and Covid-19 stay-at-home requirements, many people are looking into ways to power their home when utility power goes out. Battery backup systems coupled with rooftop solar are an ideal solution to keeping the lights on during these blackouts. Although these battery backup systems are affordable, quiet and clean — there are limits to the amount of power they can provide.

We all have had experiences with the limited energy capacity of batteries — neither our phones nor EVs seem to run as long as we would like. Moreover, we know that battery-powered devices cannot provide as much power (sometimes referred to as in more technical terms as “oomph”) as devices that have cords plugged into the wall. These limitations are based on both the energy capacity in the battery (measured in kwh), as well as the power delivery capacity of the battery (measured in watts).

Large appliances in homes presents the biggest challenge to powering a whole house with battery power. Power requirements for a central AC, electric oven/stove, pool pumps or EV chargers can be over 5,000 watts each. If these appliances were to be powered by a battery backup system with a 10 kwh or 13.5 kwh battery, that battery would be discharged completely within a few hours — leaving no more energy for more essential items such as refrigerators, lighting and computers. Of course, a determined DIY homeowner could turn off the circuit breakers to these appliances when the power goes out. But this approach does not work if the blackout occurs at night or when no one is home.

To solve this problem, Span has developed a “smart” electrical panel that provides detailed control and monitoring over every single electric circuit in your house. Arch Rao, CEO of Span, is our guest on this week’s Energy Show. Prior to founding Span, Arch was head of products at Tesla Energy, working on their PowerWall, and previously he was at the Westly Group and Stanford University. Please join me as Arch explains how Span makes home energy connected and intuitive with a smart electrical panel.

Wholesale Distributed Generation – Clean Coalition

Wholesale Distributed Generation – Clean Coalition

With the Stay At Home orders in place throughout a large part of the U.S., many of us are now 100% dependent on our home’s electric grid for work — as well as lights, refrigeration, HVAC and entertainment.

Unfortunately, our old fashioned electric grid is not up to the challenges of wildfires and storms, not to mention ever-increasing maintenance costs. Transmitting power long distances over high voltage transmission lines is particularly vulnerable to disruptions. Although this old grid was good for over a hundred years, new technologies — particularly battery storage, solar and smart appliances — are more reliable and less expensive.

These new technologies move the generation and storage of electricity much closer to the buildings that need this power — a design that is called Distributed Generation. In suburban areas there is often enough available roof space for solar panels; power for these systems is generated Behind the Meter (on the customer’s side of the meter). But in urban areas there is rarely enough roof space; instead, large solar power systems can be installed over parking lots, on brownfields, or on warehouse rooftops. With this design the power is generated on the utility’s side of the meter — a concept called Wholesale Distributed Generation.

Wholesale distributed generation makes terrific environmental and economic sense. The Clean Coalition was established in 2009 to accelerate the deployment of wholesale distributed generation. They advocate for a modern, efficient power system that takes advantage of these new solar and storage technologies to provide clean, reliable and more affordable energy.

My guest on this week’s show is Craig Lewis, the Executive Director of the Clean Coalition. I’ve known Craig for almost 15 years — going back to his work at GreenVolts, one of the pioneering solar concentrator companies. Please Listen Up to this week’s Energy Show as Craig shares how the Clean Coalition is working to create fair, transparent, and effective policies and programs to help power the United States with renewable energy from local sources.

Solar System Upgrade

Solar System Upgrade

With the gradual improvements in solar technology over the past 15 years, many early solar customers are considering a solar system upgrade. Some people want to add more panels because their electrical demand has increased. Some people have inverters that are past their warranty. Some people want better system monitoring. And some people are doing a home renovation and want to re-use their existing panels.

Not surprisingly, the most common reason for an upgrade is to add battery backup capabilities to keep their lights on and their fridge cold. Systems based on older string inverter technology (and some microinverters), need an inverter upgrade to be compatible with the latest lithium ion battery technology.

Thinking back on the equipment we installed 20 years ago to today, a lot has changed. Solar panel efficiency has gone from 14% to over 22%. Inverter efficiency has gone from 93% to 99%. Monitoring (while still somewhat complicated) is now standard. And, perhaps most importantly, battery storage systems are automatic, more reliable and have 10-year warranties.

Remember, the 26% tax credit applies to solar and battery upgrades. So if you are thinking about a solar system upgrade, are about to re-roof or do a home renovation, or want to add battery storage, please listen to this week’s Energy Show. We will review the latest solar technology, detail what’s involved in upgrading, and provide useful tips to ask your solar installer so that you get the best solution for your home.

The Myth of Whole House Battery Backup

The Myth of Whole House Battery Backup

Will batteries keep your AC cranking and electric vehicle charged up during an extended blackout? Probably not.

We like to believe the myth of whole house battery backup or the notion that our 21st century lifestyle will continue unabated despite fire hell or high water. The reality is different: Typical battery backup systems work best when they are designed to ration battery capacity and minimize the use of major appliances. These systems must also be integrated with rooftop solar so that the battery can be recharged as soon as the sun comes up.

There are two fundamental engineering limits that make it impractical to run a whole house on battery power alone. First, the energy capacity of typical lithium-ion battery systems is insufficient to power an entire house through a nighttime blackout. Second, battery backup inverters are not powerful enough to start and run many large appliances. Adding multiple batteries and inverters can overcome these engineering limits – but at a very high cost.

Nevertheless, a well-designed solar and whole house battery backup system can provide limited power almost indefinitely. To learn more about the reality of backup power in the event of a blackout or Public Safety Power Shutoff, please listen to this week’s Energy Show.

SolarEdge-Perspective for a Distributed Grid

SolarEdge-Perspective for a Distributed Grid


People talk about solar panels and batteries a lot (at least the people I talk to). The reasons are that solar panels are conspicuous on rooftops — and batteries are what keep the lights on during increasingly frequent blackouts. But the real brains of a solar and battery storage system is the inverter.

With increased global production, solar panels and battery cells have become commodities — differentiated mainly by price and efficiency. For a variety of reasons, inverters are still quite specialized. Initially, inverters simply converted DC current to household AC current. Modern inverters also provide a variety of safety features (rapid shutdown and arc fault protection), monitoring, and grid support services. The next generation of inverters extends beyond solar, providing backup power, EV charging and home energy management capabilities.

Through a combination of great technology, disciplined execution and industry vision, SolarEdge has become the leading inverter company. Based on my experience in the field (and roof), they have the best combination of efficiency, safety, installation ease and overall value. Most importantly, SolarEdge continues to push the technology envelope as they expand into backup power and distributed grid services.

Our guest on this week’s Energy Show is Peter Mathews, General Manager of North America for SolarEdge. He has done a terrific job growing SolarEdge to over a 60% market share in the U.S. Please listen to this week’s Energy Show as Peter shares insights around SolarEdge’s business, how SolarEdge is addressing the power crisis in California, their new commercial products, and the company’s ongoing product vision for a distributed grid.

Solar Tracker Systems with Alex Au

Solar Tracker Systems with Alex Au

Whether it’s a residential, commercial or utility solar project, contractors strive to install systems that generate the most energy at the lowest lifecycle cost. Solar panels operate at their peak output when the sun is perpendicular to the panel. So for maximum energy collection, tilting the solar panels at the local latitude (37 degrees here in San Jose) facing south is generally best.

Because of existing building structures, compromises are necessary when installing solar panels. Residential systems are generally installed flush to the roof because tilting the panels is unsightly, and the efficiency benefit of tilting the panels is not worth the additional mounting system costs. Commercial systems on flat roofs are generally installed on racking at a relatively low tilt so that more panels can be installed — but almost never horizontal since flat surfaces collect dirt and debris.

But large-scale solar installations do not need to compromise when it comes to tilt angle and orientation. Systems can be more easily oriented due south and tilted at the angle of the local latitude. Taking things one step further, since the sun moves throughout the day, an additional 10-25% efficiency can be achieved if the panels track the sun.

Single axis solar tracker systems generally towards the east in the morning and west in the afternoon. More complicated dual axis solar tracker systems tilt east-west daily and adjust north-south seasonally. Because of the increase in efficiency, trackers have become a standard feature on large solar farms. Essentially, the added complexity of moving parts is worth the big increase in energy output.

NEXTracker was recently ranked the number one tracker company globally. They provide tracking systems and engineering for large utility scale projects all over the world. My guest on this week’s Energy Show is Alex Au, CTO and co-founder of NEXTracker. Alex was one of the pioneers in the solar industry as a key member of the team that developed the first integrated racking AC solar module, and then developed NEXTracker’s core tracking technology.

Please listen up to this week’s Energy Show as Alex shares his insights on NEXTracker, their technology and their recent work in incorporating flow battery technology to help eliminate the imbalance between peak demand and renewable energy production for utility scale applications.