Solar Window - Electricity generated from a clear exterior window.

Solar Windows and How They Can Make Buildings Net Zero – Greenbuild 2019


At Greenbuild 2019 last week we learned about many new products that will help buildings to be completely independent of the energy grid. Most solutions included solar panels and battery systems. Of course you have to start with a very well designed building with particular attention to the details of insulation and air tight sealing. The following are interviews of the first clear window solar panel we have seen and snippets of the “Strategic Synergy: Resilient, Passive and Smart Grid-friendly” presentation.

Solar Window – Electricity generated from a clear exterior window

“My name is Veeral Hardev From Ubiquitous Energy and we’ve developed a transparent solar window. So it’s essentially a transparent solar panel that functions as a window. So what we got here is about a square meter of total window area. And what we are demonstrating here is we’ve connected all the windows to this multimeter. So I turn that on. You’ll see that we’re producing some voltage from even just the ambient light in the room.

But to kind of mimic what you get from sunlight, which is much more energy in the infrared. We’ve attached some infrared LEDs down here at the bottom, and when I turn those on, you’ll see that the output voltage dramatically jumps up. And if we were to actually see sunlight, this wouldn’t even be even higher, about 150 volts. So it’s just demonstrating a way that you have windows that look aesthetically pleasing. It’s about 65% transparency, which is right in the middle of what architectural class windows are. Has the same level of thermal performance as standard low heat windows do. And it’s also generating power.”

The Duck Curve – California’s Energy Use Curve

“It looks like the mode of grid in California specifically and you can see that as time marches on, there is this increasingly fat belly of the duck and that is the addition of renewables to the California grid. Then when the sunsets and people go home and they turn all their appliances on, that’s what the ramping, which is called the neck of the duck. So we’re trying to look at how we can have buildings, which use 70% to 75% of the electricity on the grid, use to flatten this curve and that’s what this is about. What we’re learning is, is it’s not only how much energy you use, but when you use that energy, right? Because the profile of the grid, this is the marginal carbon emissions of the grid in California in 2019 and then looking out even the 2030, where increasing levels of renewable energy on the grid still being that at certain times of day, it’s fairly grid carbon intensive. So we need to be thinking about; can we have buildings use energy when it’s most appropriate?”

Strategic Synergy: Resilient, Passive and Smart Grid-friendly

“And so we’re going to go down to these two sort of specific building types and look at synergy between ones who have… If you have say a net zero size PV array, some batteries, and what kind of resilience does that buy you? And what are maybe also the CO2 impacts.

Before that I’m going to get into just a little bit on load shifting and talk about micro groups. So when we want to create the resilient net zero energy building, what are the first steps that we do? And Ralph and Mark both kind of talked about these. It’s like, we’re going to start with good design. We’re going to start with the high performance envelope. We’re going to start with really good windows. We’re going to start trying to reduce those loads down as low as we can get them.

So there are systems, get really small, and then those small systems tend to be more energy efficient than say a really big system, if we had higher loads. We’re going to move people towards the perimeter probably. So that we can take advantage of daylight. We can take an advantage of natural ventilation. We’ll put some thermal mass in the building and maybe shift the loads back a little bit. And all that’s going to help us make our buildings easier to get to net zero. And I think we’re going to see it’s going to also help them get easier, easier to get to a resilient point.

So on the thermal mass has been kind of an energy storage that we’ve typically seen and active energy storage is kind of the next thing that we’ve been talking about. I think thermal storage has been something that’s been around for a while, but batteries are the thing that’s coming into the vernacular of design a lot more now. And it’s just because the technology is changing over the last few years, I think with electric vehicles coming onboard, and it’s just becoming more and more available for us as designers.”

Micro Grid

“A grid can be disconnected from the grid or connected to the front of the grid or connected to the grid to allow it to operate, really, in a resilient state.

This is a sort of a diagram of a microgrid, and you can see … Let me see, I want to get the whole point because there’s two screens. You can see at the top on the right-hand side, that’s some of the energy resources. So onsite that might be solar. It might be a gas generator. It could be wind turbines. It could be any sort of energy resource that you might have in your building.

Next down from that are battery storage. So you can integrate battery storage with that and give yourself a level of resilience. Give yourself a level of ability to support the grid.
And then there’s the loads and the microgrid can actually control those loads, so that if you go into an I islanded state where you lose power, say. You can curtail, you can start to turn some things off to make better use of the limited resources that you have.

Here’s the brain of the microgrid as the microgrid controller that watches both the loads and energy resources in your building. And then watches it waveform. That’s kind of what the radiator-looking squiggle represents of the grid. And the grid’s usually at about 60 Hertz.

As the grid gets taxed, if there was some kind of a outage, that frequency will start to decline. Now, you get to 59 Hertz, and there’s red lights going off everywhere. And they’re freaking out at the utility, and trying to bring on more power. What happens in that case then at the microgrid is a controller sees that, and says, “Whoa, the frequency is declining. I can turn this off.” You know, in one cycle, kind of instantaneously and move to the batteries. And the controller might then start to curtail loads and turn things off in the building. Maybe it’s turning off some lights. And it’s using the solar to charge your batteries, hopefully, at the same time. So that you could, potentially, also operate at night. Without the microgrid controller, you might be able to island your PV, but you usually can’t charge the PV and the batteries and kind of operating everything and all at once.”

Learn more about Greenbuild at