All right. Warren batteries. We talked about utility scale, big batteries and how they can for lots of advantage to electricity systems and easing grid integration of variable renewables. Let's talk about another way batteries can be used were called sometimes referred to or behind the meter. BTM batteries. The meter in this case refers to the way the electricity consumption of a building and industry a house is measured. So these are household level or industry level or commercial building level batteries. This might be a battery. For example, in your home you would have along with your solar system. What could that do for you? Well, lots of things here is in several ways to think about it. Let's imagine you have a rooftop PV system. And sometimes the sun is shining brightly and you're making too much electricity. That is, it's more than you can use in the house. Well, depending on the rules where your house is located, you may be able to sell it back into the grid or maybe not. The batteries give you the flexibility to just store it and use it later. You could also do some arbitrage here. Let's imagine you're in an environment where electricity is worth a lot at certain times of the day. So you could generate electricity, let's say midday and let's say electricity has a large value per kilowatt hour between four and six p.m. You generate from 12 to 4, 12 noon to four PM and store that in your batteries and sell it back into the system from 4 to 6 p.m. And come out ahead that way. Let's imagine another example. Many large commercial industrial buildings pay not just for how much electricity they use, but how much they use anyone times called the demand charge. And if you have a large building, not a residential house, but a larger building, an industry, a commercial building, a school hospital and so on. Typically maybe half of your electricity bill will be what's called the demand charge. How much used any one time. Well, a few batteries, you can control that if you're building needs as an example, a megawatt, well, your demand charge would be a megawatt that could be big. But if you've got a 500 KW battery, you can cut that in half by buying 500 KW from the utility and providing the other 500 KW with your battery system. So these are examples of how batteries can be of great economic value to end users and ease grid integration of renewables. Here's a graphic of how that what's called peak shaving would work. So again, the scenario here is you have a large commercial building and probably not arrest central building because there often not build this way and you want to cut your peak demand. Well [COUGH] The blue shows the demand curve over the course of the day of what it would be without a battery. [COUGH] But what you do is you charge up your battery at certain times over here and then you discharge a peak times. You meet the peak in part with your battery. So the yellow line is the net load. Notice excuse me in the sample how your peak went down and that will save a lot of money because you get charged for the peak in many commercial industrial buildings. So that's just an illustrative example of how battery can reduce peak demand from the consumers perspective. Now let's mix this that example in with a photovoltaic system. So this is over the course of the day and this is how this might work at night. You have a solar system doesn't generate at night. So you buy your so called grid purchase during the day, the electricity, I'm sorry, the solar generation would show this characteristic curve. This is a kind of a household level. So what you do is you run the battery and solar PV system in a certain way. Here, you're charging the battery up with your solar system. So the blue shows what the house itself is using to run itself and the black are what you're charging the battery in. And at the end of the day, you use the battery to meet your peak late day demand battery discharging here. And why would you do that? Well, if you're in, say California on what's called a real time or time of day price pattern that you pay a lot for electricity when everybody else is using it, which is many more utilities are going that way. Because economically logical to charge the most when it's scarce. And you could buy electricity at 21:00, but it's expensive this way. You're essentially needing your peak 20 100. Our electricity demand with electricity. You made yourself on your solar system, but you made it earlier in the day and you start it in your battery for this, Call it 9, 9 hour period. And it seems a little complicated, but it's all, it's all in the software. You don't have to make these decisions. You install the battery, you install the solar system and you install software that figures all this out. And the net result can be significant reductions in peak shifting demand as seen by the utility from peak to off peak times. Now, whether or not that economics workout, that's only you need to figure out. It's not self evident that that would be the case. That depends on how much solar system costs and almost the battery costs. But the concept of using so called behind the meter batteries to essentially shift the demand is fairly clear and transparent economics more complex question. But because of this sort of thinking and the possibilities that having batteries behind the meter, suggest this kind of system is increasingly common. And here shows a number of household batteries sword systems installed in Germany from 2013 to 2018. You can see it grew pretty rapidly. There's a lot going on here. There were aggressive policies to support this kind of system in Germany in this time period, but it shows that, well, technically it's feasible. It's doable and batteries plus PV at the household level can significantly shift demand and ease grid integration of those solar PV systems.
