Installation of solar panel on roof

Power Distribution for the Oakland EcoBlock: A Conversation with Sascha von Meier

Eunice Chung

Alexandra “Sascha” von Meier is the Principal Investigator and co-Energy team lead of the Oakland EcoBlock project. She is also the Director of Electric Grid research at the California Institute of Energy and Environment (CIEE), a public-interest energy research center based at the CITRIS and the Banatao Institute at UC Berkeley; an Adjunct Professor in the Department of Electrical Engineering and Computer Science at UC Berkeley; and a Faculty Scientist in the Grid Integration Group at the Lawrence Berkeley National Lab. Passionate about climate action, Sascha is interested in how the EcoBlock model can be used to quickly and equitably achieve decarbonization. In her interview, Sascha discusses the technical and regulatory complexities of designing the EcoBlock microgrid and shares insights about opportunities for a more climate-resilient future.  

This interview has been edited for length and clarity.

EC: How has the EcoBlock microgrid design process been going?

SvM: We’ve been looking into different options with Pacific Gas and Electric (PG&E) for disconnecting the microgrid when it islands, or separates, from the main utility grid. One could use a traditional recloser, which is a switch that automatically turns the power off whenever there’s an issue with the electric lines. Another option is a more modern device called an automatic transfer switch. We’ve also explored different kinds of inverters, and whether we’ll have just one or three electrical phases. A three-phase system is common for larger installations but is also more expensive. 

The great news is that all the important PG&E engineers who ultimately have to approve these things have been in the room and plugged into the conversation, along with our EcoBlock Energy team members. 

How is this related to EcoBlock’s decision to pursue an AC (Alternating Current) microgrid? Initially, there were two options—the AC versus the DC (Direct Current)—and allowing solar panels to form an island on PG&E’s regular power distribution network wasn’t previously allowed. What changed PG&E’s mind? 

I think PG&E’s thinking on microgrid islanding has really evolved after California’s experiences with wildfires and PSPS (Public Safety Power Shutoffs). Resilience is a big topic now—everywhere from the California Public Utilities Commission (CPUC) to the national level—and there’s a real interest in allowing for creative ways to improve energy resilience. PG&E wants to provide more reliable service, help advance solar integration goals, and keep everyone safe. The technology has also improved such that PG&E can have trust and confidence in the way microgrids will connect and disconnect from the main grid, more so than they might have had a few years ago.  

PG&E has revisited their traditional rules of not letting anything form a power island on their equipment. They now have a specific tariff called the Community Microgrid Enablement Tariff (CMET) that accounts for the possibility that a group of customers are operating on their own while the rest of the grid is out. 

Infographic showing community microgrid service area with generation and distribution
Image credit: PG&E
The CMET tariff is part of PG&E’s Community Microgrid Enablement Program (CMEP), which seeks to facilitate the technical, financial, legal, and regulatory development of front-of-the-meter, multi-customer microgrids. 

As for DC wiring, PG&E’s engineers aren’t particularly keen on it because it’s a different technology they don’t have established procedures for. The more we can use existing wires, the less the microgrid will cost, which means the design is more likely to be used in other places. We plan to work with the existing AC infrastructure to the greatest extent possible.

Where are the microgrid separation points?

A traditional recloser on the primary side of the utility pole would sit up on the pole and have an open/close switchon the primary wires, which have the higher voltage—in this case, 2,400 volts. Those are on top of the pole, but the pole may not be strong enough to handle that. If we needed to replace the pole, we’d have to get Comcast, AT&T, and all the telephone and cable guys to come and take their wires—which are typically the lowest ones that are closest to the ground—off the pole for the PG&E crew to come in, drill a hole, put in a new pole, and move everything over. 

It’s doable. PG&E does this kind of thing all the time, but it’s a bit cumbersome. It’s also possible to have these primary wires go down to the ground in a riser, which has that plastic sleeve that you see going along some poles. Sometimes, the power lines go from being overhead to being underground. In that case, the recloser could go on a concrete pad that could be put by the sidewalk. However, pad-mounted reclosers are larger and need a wide clearance around them, which requires a special permit because it encroaches upon the sidewalk and could also take away a parking space. 

We also looked into another possibility with PG&E: to put an isolation device on the secondary, lower voltage side, which are the 120/240 volts that go into your house. That would be a smaller piece of equipment that would fit pretty readily on the pole. But the technology that we considered for that isn’t quite ready for our project schedule. 

In any case, at least one transformer—and maybe several on the block—will have to be upgraded and replaced. As California moves forward on its all-electric policy, we want to future-proof the system for more electric vehicles (EVs) to be adopted in the coming years.

We will also need a three-phase transformer for the community battery and inverter instead of the single-phase service that goes to each individual house. All the existing transformers are single-phase. Our grid uses three phases, which are three different time steps for the alternating current. The three together make for more efficient transmission, generators, and motors. A larger commercial building would typically have three-phase power, and their big motors, like an air conditioning system or a grocery store refrigerator, would be three-phase. Our community battery will be about 150 kW—and for that size, it makes more sense to go three-phase.

So there will be an on/off switch, probably at the top of the utility pole, which allows the microgrid to separate from the regular power distribution system in the case of a power outage. 

That’s right. PG&E will control the on/off switch. That’s part of the deal, especially while their engineers are still gathering experience with islanding microgrids on their system. They want to make sure there aren’t any surprises and keep their crews safe. It’s a concession we’re glad to make because it really won’t affect the EcoBlock. The understanding is that whenever there’s an outage on the main grid, PG&E’s system will automatically have the microgrid operate as an island—which is exactly what the EcoBlock would do if we controlled the switch ourselves. Except this way, EcoBlock is not responsible if something were to go wrong at the switch and someone got hurt. That’s a huge plus! We wouldn’t want to operate the microgrid as an island separate from PG&E normally, while the grid is up, because there isn’t any economic incentive to do so. We actually benefit from staying connected because the grid gives us backup. So on a normal day, we don’t have to be as strict about conserving energy and managing our battery. 

There’s been a lot of progress in the world of microgrid policy. Has PG&E’s decision-making process been affected by current development? 

I don’t think PG&E’s immediate decision-making process with EcoBlock is driven by state-level legislation or policy. I think it’s just consistent in spirit with the way everyone wants to go. We’re trying to come up with something that’s workable, practical, and possible for PG&E to replicate elsewhere in the future and can be done in time to start construction. That’s our goal. We really have two tracks of conversation with PG&E: one is about the technical design and the other is about the tariff design. 

In order to have a tariff agreement with the EcoBlock community, PG&E has to get approval from the California Public Utilities Commission (CPUC). PG&E filed an advice letter, which EcoBlock supported, to relax some formal requirements of their CMET tariff so that EcoBlock will be eligible. We hope the CPUC will approve this soon.

In the future, we’re trying to come up with an even better approach that would allow a microgrid to be compensated for the services it provides to the distribution system while acknowledging that it also benefits from being connected to the grid—even if it’s zero net energy. The value goes both ways. A new tariff won’t be ready on the EcoBlock project timeline, though. We are trailblazing here.  

EcoBlock is unique because the community owns the means of energy generation. In contrast, either a utility or third-party entity would own both the generation and distribution of energy for a traditional microgrid. Does this shift in dynamic affect how energy is distributed for the EcoBlock?  

The closest precedent to the EcoBlock microgrid would be the Redwood Coast Airport (RCA) microgrid, where our colleagues from Humboldt State have been working on this innovative model with PG&E. Almost all microgrids today are on the premises of a single entity, like a campus or office building. The big innovation is to let the microgrid extend across multiple property lines; there are different views about exactly how to interpret rules that say you can’t sell power over the fence.

Image showing aerial view of Redwood Coast Airport microgrid site
Image credit: Schatz Energy Research Center
The Redwood Coast Airport microgrid will use a 2 megawatt (MW) solar photovoltaic array and 8 megawatt-hour (MWh) battery to “island,” or disconnect from, the main utility grid and maintain electrical power for the airport and adjacent U.S. Coast Guard Air Station. 

Our argument is you can’t sell power over the fence unless you’re a utility, but you can share it with members of your neighborhood association or co-op. It’s not like you’re buying something wholesale and then re-selling it on eBay for a profit; it’s more like you and your friends chip in to buy a whole cheese wheel which you would then slice up and share. The EcoBlock legal team has made that case in a white paper about the “own use” clause in the Public Utilities Code, Section 218.

There haven’t been rules for this sort of arrangement historically because the technology wasn’t there to share electricity on a neighborhood basis. Now the regulatory world has to catch up with all the advances in solar and battery technology and power electronics that give us a lot more options for managing electricity locally. By working with PG&E’s wires and not putting in our own for the EcoBlock, we are still okay crossing property lines because it’s the regulated utility that’s responsible for the infrastructure.

What sparked your interest in renewable energy and climate change in the first place? Would a younger Sascha ever have imagined she’d be part of a project like EcoBlock?

Doing this project feels like realizing something that’s been on my mind for a long time. So why did it take so long? It’s a slow process, but I’ve cared about climate change since the 1980s, when we first became aware of this issue. Luckily, some of the things we’re doing today—like with EcoBlock—not only help the climate but have side benefits. This is about green jobs. This is about community, governance, and equity. 

Taking climate action requires money—but in the end, we save more than we spend. It also takes commitment at the government level. We certainly have that at the local, state, and now national levels; the next step is to make sure we have it globally.

Image credit: Collin Chapelle/NY Times

Update as of October 8, 2021: The California Public Utilities Commission (CPUC) has approved PG&E’s request for modification of the CMET tariff, which allows PG&E to establish a tariff agreement with the EcoBlock community.

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