Welcome back. To remind you where we are, we're talking about the grid integration challenge. How do you run a reliable, low-cost electricity system when you have significant use of variable renewables, wind and solar PV, whose output fluctuates with the wind and with the sun. As we've talked about, there are lots of things you can do. Lots of tools available to help that. Everything from ramping coal plants, that is turning them up and down to meet demand, which historically has been seen as not possible, when in fact you can do as we saw some data, to recognizing that a large number of wind turbines over a large geographic area actually have a fairly smooth output. It doesn't jump up and down quickly. Now we're getting to perhaps one of the main or most important tools for grid integration, which is storage. As we've talked about, in most cases, generally you have to make as much electricity as you use, all the time, 24/7. But maybe not, just to confuse things a little bit, you can store electricity. It's not easy, but it's possible. That's what we're going to spend the next few videos talking about, storage of electricity. To illustrate the potential of storage before we talk in detail about the technologies and the markets and implementation, let's talk about a simplified example of an electricity system. Here we have the old diagram. We have the power plant, the transmission lines, the distribution lines, and the transformers, down to the house. We've talked about that overall structure. Let's imagine, again, a simplified example where we have a house or let's talk about a village, a town, a bunch of houses with a peak electricity demand of 100 megawatts. This is our simplified example. We have a power plant with a peak output of 100 megawatts. That's all good. In this simplified example, the power plant can generate as much electricity or power, peak power, as the town needs. Let's imagine a scenario where the village grows. Now you have a village, a town, with a peak demand of 120 megawatts. Well, clearly the power plant is not big enough. What do you do? Well, the obvious answer is we have to build a new power plant. But that's expensive, takes a long time. There's another way to think about this problem. What if we just put a 20-megawatt battery next to the power plant? Now, keep in mind the 100-megawatt old peak demand, and even the 120-megawatt new peak demand of the village is a peak demand. You can imagine, for example, if this village is in a hot climate, that peak demand is summer afternoons when all the air conditioner is running. It doesn't always need 120 megawatts, only at peak times. If we put a battery next to the power plant, at peak times, the power plant will generate 100 megawatts, the battery generates 20 megawatts. All of a sudden, we've met peak demand without expanding the power plant, and 20 megawatts of storage is a lot less expensive than 20 megawatts of a new power plant. You might think, well, how do we charge the battery? Well, at night when the village demand is down at, say, 80 megawatts, the power plant runs at 100 megawatts, but 20 of them goes to recharge the battery. You can see in this simplified example how a battery can really cause one to rethink power systems overall. In this simplified example, it was clear we had to build a new power plant, but all of a sudden, it was clear we didn't because storage can do that. Let's take another simplified example to further illustrate the potential of storage to transform electricity systems. Let's imagine the scenario where we have a 120-megawatt demand in the village, and a 100-megawatt power plant and a 120-megawatt battery. Now everything's okay, but let's slightly complicate the story and say what if the transmission line is too small? What if the transmission line has a peak capacity? Transmission lines do have peak capacity. It can only be so big until you have to make them bigger, and that's expensive. Let's imagine the transmission line can only carry 100 megawatts. Well, the obvious example is we need a new transmission line, we need a bigger transmission line, but that's expensive and time-consuming. Here's another idea. Let's put a 20-megawatt battery at the other end of the transmission line right at the transformers that serve the village. How would that work? Well, when the village needs 120 megawatts, it gets 100 megawatts from the transmission line and 20 megawatts from the battery. All of a sudden, we were able to essentially circumvent the transmission line capacity, or another way to think about this, we thought we had to build a new transmission line, but all of a sudden we don't, and it's going to be a lot less expensive to buy a 20-megawatt battery than to expand the transmission line. What this example illustrates is the potential of storage. It's a way to rethink electricity systems entirely, and it's particularly relevant to the grid integration challenge. In subsequent videos, we'll tease apart these examples in more detail, talk about the technologies of storage, and talk about how that storage market is developing.