All right, remember where we are, we're talking about storage as a tool for good integration. We first talked about pumped hydro, which is what the storage is actually installed worldwide, almost all of it is pumped hydro. But now we're going to talk about batteries which are type of storage which are returning tool for grid integration and where there's a lot of excitement and activity and research and potential. So we'll talk batteries, that terminology is not exactly consistent, but sometimes it's called electrochemical storage. because again, you can store energy or electricity lots of different ways. You can store it in the form of ice, you can store in the form of pumped hydro, water up a hill. We're going to talk about batteries because there's a lot going on a battery world and here's some schematics of how that might play out. We have a solar home system, you have, say, solar photovoltaics on the roof of your house. They could charge a battery which then connects to the grid, one possibility. Here's an actual photograph of a utility scale battery storage PV system where this case the batteries are relatively small located next the panels, it's a possibility. Here's yet another photo of a real system where in this case the batteries aren't physically next to the solar photovoltaic or wind turbine. They're located at the distribution transformer that gets back to the model we talked about a few videos ago where batteries can be used to postpone or avoid the need for transmission upgrades. So there's a lot of ways batteries can be deployed. What does the battery itself look like? Well, it's a system, it's not just the battery, the chemical thing itself, there's also two components. There's what's called here, the storage device we'll talk about that chemistry in just a minute. Monitors, controls the switches need to convert DC which is the type of electricity the battery store and provide into AC which is how electricity systems run. You have temperature control because any time you have batteries you're going to be dealing with heat issues because some of the energy that goes into charging the batteries are going to end up providing heat. That's just can't be devoided. That's a thermodynamic requirement. In essence you have to get that heat out or else it's going to cause damage and wear. So there's always an issue of temperature control. Probably a transformer can increase the voltage to what the system can use. Suddenly more detailed look at what the system looks at is that you start with the basic battery component called a cell. You have thermal management to keep the heat down. You have energy management figure out when you want to charge when you want to discharge, all sorts of other stuff going on, fire protection. So it's a fairly complicated system. But the heart of it, the storage itself occurs at this graph we call the cell level. Now, the battery essentially chemistry, how it's actually done is an evolving story, but 5, 10 years, I'd say 10 years ago, it wasn't clear what chemistry, what battery design was going to emerge. But that is becoming more clear. And one specific technology, usually called lithium-ion, which is actually a class or several technology you can fit under that. But it's how it's basically the fundamental chemistry is emerging. It's pretty much the same type of battery, at least at a conceptual level, is in your laptop or other portable electronics. And that is a lot of reason why it's emerging as a promising grid storage option because of the billions of dollars of R&D that've gotten into refining batteries for laptops. They've become low cost, they've become reliable, they've become long lasting, they've become efficient and essentially that's been leverage for utility scale storage. So what's often called lithium-ion battery is really emerging as the dominant technology. There're a lot of other ways you can design batteries from these get a bit more exotic vanadium redox, metal-air, sodium batteries. These may emerge in new technologies, it's rarely exactly clear what will emerge as dominating the market. But the way it looks now, as of late 2020, is lithium-ion batteries are starting to dominate. Now you can see your lead-acid batteries, that's the old fashioned battery that you have in your car to start it. They work, they're reliable, but they have their challenges. They don't have particularly long lives, they have lead in them and lead is a environmental contaminant, a nasty one. So there're concerns any technology of pros and cons will talk briefly about another technology which is I'd say second to lithium-ion right now but may see some growth. We'll find out. The apparent success of lithium-ion batteries it's the way they appear to be starting to dominate the market is fundamentally because the costs have come down so dramatically. So to summarize the cost curve this was a publication that came out in 2015 that showed historical costs for battery packs for electric vehicles, which is different application but the same fundamental technology. And then looked at the four casts for various experts, this was published in 2015. And interesting to see when the article came out, there was a lot of reaction saying, well, that's too optimistic, we'll never get cost down that low. These points are basically people being very optimistic, what's probably not going to happen. And the reality is shown by this thing that I added is we're way below that at 2018 actual was way below where any of the four cast could be. It's a similar pattern as we saw for solar photovoltaic where costs came down much more quickly than anybody expected. So lithium-ion batteries are emerging as a dominant we'll call it a contender in battery storage because of costs. And there's been quite a bit of work done this is some work done by International Renewable Energy Agency showing there is further cost reduction potential. So what we're seeing here's the actual cost of this specific type of battery lithium-ion phosphate, a system in 2016. And this study looked at potential for cost reduction in all the components of the battery. And I wouldn't say predicted, but said it be possible to get down to here more than a 50% reduction, maybe 60% cost reduction by 2030. Though, overall point being battery costs are going down and there is considerable potential remaining for significant further cost reduction for batteries. Now, that's the battery technologies all under the kind of lithium heading. There's another technology on a brief dimension called a flow battery. A very different way of thinking about batteries. And this is a vanadium redox flow battery one possibility. Essentially you have two large tanks of fluids that when you mix them in a certain way, actually you don't really mix them you have them across the membrane. They create a voltage, which can be simple that's what battery is. And if you think about, well, that seems kind of a neat idea because if you want more electricity, just run the pumps faster. If you want it to last a long time, you have bigger tanks. And that's all true. But it has its challenges that's something you have to handle very carefully. There's a lot of components getting in controls just right. [COUGH] Like any technology has pros and cons the flow system as I mentioned, the advantage conceptually is you can have a large range of power and energy. That is, you could run the pumps fast and have a lot of power, run them slow and have big tanks and have the battery lasts a long time. The efficiency looks pretty good. These things should last a long time. Disadvantages, you have some very strong liquid solutions you have to manage carefully. You have pumps, you have sensors, it's a mechanical system and mechanical systems just wear out and require careful maintenance. And some of the costs the membrane material it's not clear how they are going to be. So, any technology has its questions. Flow batteries, maybe we'll probably see over the next five or seven years if they start to emerge as commercially viable. Right now lithium-ion and it's kind of related technologies appear to be a promising technology.