Now we're going to work a little bit on the designing of the photovoltaic system. So the whole idea is to take all the parts that we have a study in class. All the concepts in terms of how the parts relate one to another, and put it together in a complete system so we can start charging our batteries. So we have to remember the panels. Remember that a group of panels construe at an array, and that the materials are silicon because it's the cheapest. Remember, it's the most common material in the crust of the Earth besides oxygen of course. What is the power that we need? See the dimensions of the panel are important because very often has a limited amount of area that you can cover that is exposed to the sun. So we have to know the dimensions well. The voltage, because the voltage it's what relates the panel through your battery. So there must be somehow some communications between the panel and the battery. Of course, the panel what it's doing is charging the battery, so we must have the voltage of the battery, and the open circuit voltage off your panel. Then, of course, we do not want to overcharge or undercharge our battery because the batteries are so expensive. So we need that charge controller. You remember that there are three types of charge controllers. There is the on-off, what we call this shunt controller. There is the pulse width modulated, and there is the maximum power point tracker, which is the most expensive but is the one that charges the batteries the fastest. Because as you remember it, it talks to the battery, find out what is the voltage of the battery. If the voltage of the panel it's usually much larger than the voltage of the battery, convert the difference between the two, convert it into current and charge your battery much quicker. Of course, we also would like to remember the batteries. The most common batteries is the lead acid. The lead acid is a car battery. Is the big fellow that it's very heavy, but nowadays the lithium ion and the lithium ecology are many. There's a gama of possibilities for the lithium ion, but that lithium ion it's expensive. So that is one of the liabilities. Of course, what it does is that charge your battery. So everything that we have included on these costs charge a battery, now most of our loads are alternating current. So we have to change from DC to AC, and we need the inverters. What the inverters do is of course, change the current from direct current into alternating current, and they come in different flavors, there's one that it's produced on a square wave. The square wave, it has all those corners, and all those corners induced harmonics. Harmonics are really not very good because anything that it's digital, any of your loads like a computer, a TV set, all those digital things have difficulties playing with the square waves. Or you can use an H-bridge that is somewhere in between the square wave and the fully synthesized, pure sine wave, and the pure synthesized sine wave, which is the most expensive of the inverter but he's the best class of the inverter. It's the one that gives you the least amount of trouble when you're doing the applications. Then to what we call the balance of the systems, which are everything that is not really the panels, but that includes the cables, the gauges, the breakers, the fuses, the connections, all those things that are really important for us when we're going to put the system together. So you're going to see in this diagram, an aschematic of the solar panel, and that's the fellow with all the literal squares, and it is connected to a charge controller. You know exactly what is the mission of the charge controller. Its mission in life, it's to avoid undercharging or overcharging your battery. In the right-hand side of the charge controller, it's usually a light load from the battery since the battery produced Direct Current, and most of the loads at home or in business are alternating current or AC loads, you have to go through an inverter. The inverter what it does, of course, is change from DC to AC, pure sign AC. Hopefully, if you can master, if you can afford it, then you will have as much power as you can produce from the panel, you will have available to your load. It's really important for us to review a few concepts from physics, engineering. So one of them it's the Ohm's law. What it says is that when you have a source of electrical power, the current in the source of electrical power, it's proportional to the voltage. As you increase the current, you have to increase the voltage. As you increase the voltage, you increase the power. The proportionality constant in that relation, it's the voltage. It's equal to the current times the resistance, is the resistance. That is the proportionality constant. It is sort of a law of nature that all of the devices that we have access to are fundamentally ohmic. Ohmic means they obey Ohm's Law. It is really important because we are going to use electrical wires. Electrical wires are good electrical conductors, all the electrical conductors have resistance. We have to be able to assess what is the amount of resistance, that it's reasonable, and of course, since we want to conduct as much electricity from the panels to the battery, most of our conductors we would like to be good conductors. Good conductors means low resistance. So we would like them to have low resistance. Of course, what we will connect to the battery or we'll connect to the inverter, it's our load. So load, it's also fairly technical, parallel lands. But really what it means is analogous to a physical load in the gravitational field. So you're taking something that it's very heavy, and you lift it. So you have to do work in order to lift the load. So here the electrical system has to do work in order to satisfy the demands of the load for its operation. So we know everything that we have in our system. We have discussed it from the panels. So now, we would like to define in general what we mean by the balance of system. So the balance of system is everything that it is not in the panels, or, of course, on aggregation of panels that we call an array. The balance of systems will include all the charge controllers, and the batteries, and inverters, and the cables, and the switches, and the fuses, and the ground fall detectors, and everything. So it's important for us to have a list of all our balance of systems parts, in order to be able to have the proper application at the proper place in our system, and also to have a clear round in case that one of them fail, and we'll have to do maintenance, or replace it, that we have the correct spare part. Because of course, if you have a fuse that it's for 5 amps, you cannot use it for anything except below 5 amps. So you must have the correct art for your balance of system. It's really important for us
