Ask a Caltech Expert: Steven Low and Adam Wierman on Smart Grid





The questions and answers below have been edited for clarity and length.

What is the grid?

Steven Low: It’s a giant piece of infrastructure that transports energy from where it’s generated to where it needs to be. So in addition to the hundreds of thousands of power lines that we could see, the grid also contains tens of thousands of large generators, and on the order of a billion loads. These loads are buildings, computers, machines, lighting, and so on. The grid topped the National Academy of Sciences’ list of the greatest engineering achievements of the past century.

The main challenge of the grid is that we must balance supply and demand at all times, at all points of the grid. Hidden in this infrastructure is a very complex web of control mechanisms that help maintain that balance. But also integral to the control mechanism is a comprehensive market structure that brings suppliers and users together to encourage optimal resource allocation.

By market do you mean literally buying and selling electricity?

Adam Wierman: One of the surprising things for many people is that the net is not just wires. It is both the engineering of the physical infrastructure and this economic infrastructure that ensures that you have generation when you need it. It’s amazing to think that we are able to balance usage and generation at any time, at any time, in any location, anytime. If you don’t, we’ll have power cuts. It’s really a great achievement. Not just a technical achievement, an economic achievement that this stuff works for us every day.

What is it not doing well and what improvements does it need?

Wierman: Reliability is really what it does well, but what we’re facing today as we try to make the grid more sustainable is that the integration of things like wind and solar is a direct attack on grid reliability. The standard operation is to predict what the demand will be and turn the generation on and off to ensure that supply and demand are in balance.

But with wind and sun forecasting is difficult. These are unreliable, variable, uncontrollable resources that are sustainable, but present enormous challenges.

What is a smart grid? In our last episode of this conversation series, Harry Atwater, who talked about photovoltaics, mentioned the smart grid. He described it as the Internet, but for power or electricity. Is that a striking analogy?

Wierman: It reminds me of the right thing. There are some parallels. But the smart grid is a much more challenging and ambitious task than the Internet, because it’s not just the wires that you control; it is also the devices at the ends of the wires. And you have economic market design and physical laws in that grid architecture. There are many things that make it much harder to manage. But at the end of the day, the goal is somewhat similar, because you want to enable communication and global operation of large-scale distributed resources in the same way that the Internet does for our communication.

Steven, you have developed a smart charging system for electric cars here on the Caltech campus. Can you tell us about that project? How does that research fit in with efforts to make the grid smarter and more sustainable?

Low: Electricity generation and transportation generate nearly 60 percent of the U.S. greenhouse gases, according to the EPA. Therefore, to drastically reduce greenhouse gas emissions, we need to electrify transportation and then generate electricity from renewable sources. This is both a great challenge and an opportunity. It is a big challenge because electric vehicles [EVs] consume a lot of electricity and with extremely high power, at extremely high rates. If we electrify transport, it will cause a lot of stress on the grid. But EVs are also an extremely valuable resource because they are extremely flexible. This flexibility will help us integrate uncertain and volatile renewables.

If you look at how EVs are charged these days, normally anyone can hook up an EV at any time. If you have five or ten chargers in a garage, it works well. But if you have hundreds or even thousands of chargers in a garage, such as at LAX Airport, for example, this cannot be done efficiently or economically. But it is also unnecessary. For example, if we look at Caltech, an EV normally remains [on campus] an average of six hours. They will finish charging in two hours. Therefore, it is the right choice not to charge each individual EV when they are first connected, but to use software to optimally plan the charging process of the EV.

So if everyone shows up at the office at 9:00 AM to start their workday, and they plug in their electric vehicle at the same time, that’s too much of a load on the system. What you’ve done is develop a system where the cars take turns charging. Is that correct?

Low: Precisely. When the drivers plug in, we simply ask them two questions: “When do you expect to leave? How many kilometers do you need?” With that information you can then optimally plan the charging process.

Wierman: I want to emphasize the importance of what Steven has been able to achieve here. Within a garage, the bottleneck really is the electrical line coming in and how much power it can hold. So if you can spread that out and charge 50 cars instead of five, you reduce a huge barrier to EV adoption.

Once you have this adaptability to charge anywhere in multiple garages in the city, you can now provide feedback signals from the power grid that say, “We’re stressed right now. Can you call the charge back?” Or: “We now have a lot of solar energy. Do a bulk charge now.” Those kinds of opportunities are huge in terms of enabling the smart grid, enabling the integration of renewable energy sources.

Are there any lessons in adaptability that you can apply to types of loads on the system other than EVs, such as homes or factories?

Wierman: Much of the work we do at Caltech is about finding this adaptability in major high-volume consumers of electricity. Smart buildings, smart data centers, EVs, they all give us opportunities for this kind of flexibility on the demand side, the consumer side.

What is the timeline for the development of a smart grid that can make good use of sustainable energy sources?

Low: There are more than a dozen states that have already committed to 100 percent clean energy or electricity by mid-century. So where are we? We still generate about 60 percent of our electricity from fossil fuels. That’s so much better than ten years ago, but we still have a long way to go.

Wierman: In a sense, much of the infrastructure has already reached a place where it can be integrated and implemented. There are smart devices for detection and communication that are being deployed. Solar and wind are cost-competitive. That means there will be progress in the short term.

The question is when will we reach this wall where the current architecture is no longer sufficient – where power outages become more likely, when costs start to rise. Our research is focused on getting through that wall, breaking down that wall, so that when you’re there, you can still make progress.

Are there countries leading the way in this?

Low: Germany has a lot of wind. The UK has a lot of wind. China is investing heavily in both solar and wind. An interesting case is Australia: they have the largest battery energy storage in operation.

Few countries are really lucky. In terms of using low-carbon technology to generate energy, Iceland topped the list. They generate 79 percent of all their energy from low-carbon sources. For Iceland it is hydro and geothermal energy. Norway is also very lucky. They generate more than 90 percent of the electricity from hydropower.

You mentioned Iceland with 79 percent of its electricity from low-carbon sources. How does that compare to the United States?

Low: The global average of low-carbon energy generation is actually very low, slightly higher than 16 percent. The US is also around 16 percent.

The smart grid will be very different from what we have now, but will the average person notice a change if they flip a light switch?

Wierman: One vision for the smart grid is that you should have all the smarts there to take care of the operations, but that it should remain simple for the homeowners.

Hopefully we will get to a situation where appliances like air conditioner or the refrigerator can pre-cool based on the availability of renewable energy and signals they get from the grid, where you have energy storage devices that can charge when it’s sunny and discharge when it’s no, at night.

If we can do that, our whole society will be more sustainable, our air will be cleaner, and hopefully we’ll have mitigated climate change somewhat as we go along.

It seems that a smart grid would have more security problems than the current grid. Can you indicate how this should be addressed?

Wierman: When you have the kind of communication needed for the smart grid, it can potentially create vulnerabilities. There is a huge research focus and the industry focus on trying to enable security for this.

Low: One thing we’ve learned from the internet is that security really needs to be built in.

Wierman: This is not a situation where you take internet security and put it on the network and all of a sudden you are safe. That is not a valid approach. It will introduce more problems than it solves. It has to be something built in in a different way.




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