The ugly truth behind grid-tie solar systems. Part 1, FarmCraft101 solar. Watch before you buy!

Welcome to FarmCraft. We recently had a solar system installed and in this video I'm going to go through how it works and explain some of the ways different solar systems are designed. There are many different ways to put together a solar system. Not that kind of solar system. And the main subject of this video is going to be a grid-tied solar system. I've also retrofitted my system with a battery backup and I will go through that in a later video. This is a 9100 watt solar array or 9.1 kilowatts. There are 30 panels that each produce 305 watts of power at maximum. A grid-tied system is definitely the cheapest way to get into producing your own solar power and it has some pros and cons that I will go through. Here's the basic setup of a grid-tied system. You've got your solar panels producing electricity. Goes to an inverter. Your inverter converts the DC power from the panels to AC power that your house can use. The inverter output is hooked to the power grid. If your house is using a lot of power, there's going to be a voltage drop. Then the power would be sent to the house. Actually, the proper way to say it is the electricity will flow to the path of least resistance. If there's a voltage drop at the house, then that's where it's going to go. If the house is not using as much power as the inverter is producing, then the electricity will go back up the grid, which will run your meter backwards and save you money. Obviously, if the sun is not shining, you're not producing any power and you just get your power from the grid like you normally would. Grid-tied systems are by far the cheapest systems out there. For example, our system costs $23,000. Wait, wait, wait, there's a tax credit. And then with the 30% tax credit, it comes to around $17,000. All right, now relax. Let's do the math. I use about $200 worth of electricity every month, and this system will generate most of that. So $200 a month times 12 months is $2,400 per year. So $17,000 divided by $2,400 a year comes out to just over seven years. Now this is a little overly optimistic, so we actually calculated an eight and a half year breakeven, and everything that we generate beyond that is going to be free power. So even though we're talking about big numbers here, this can make good financial sense. But there's a catch. If the grid goes down, everything shuts off. That's right. Even though you have solar panels, if the power grid goes down, you cannot produce any power. These inverters are designed to not backfeed the grid, which provides a safety factor for linemen that are working on the grid when it's down. That also makes the installation of them much cheaper because they don't have to worry about transfer switches and automatic changeovers that happen when the grid goes down. So what are the advantages to a grid-tied system? They work at a much higher voltage, and that has several advantages. One is you need a lot less wire. When you can go all the way up to 360 volts, your amperage for the same amount of power is much lower, and therefore you don't need as big a wire or as many wires to transmit the power to the next step of your operation. For those that aren't as familiar with electricity, it's useful to think of it as water flowing through a hose. The amount of water flowing through the hose is the amperage, and the pressure that the water is under is the voltage. The bigger the hose, the more water you can get through. Also, the greater the pressure, the more water you can get through. Power is a function of both the pressure and the volume of water delivered. In electricity, power is expressed in watts, and it equals volts times amps. This means if you have a lot of pressure, you don't need to deliver as much water to produce the same amount of power. Put in electrical terms, if you have high voltage, you don't need as many amps to deliver the same amount of power and can use a smaller wire. What I have here is 30 36-volt panels. They are arranged in groups of 10 to make a 360-volt output. Each group of 10 panels is wired in series, and then those three groups of 10 are wired in parallel, and that is all hooked to one single wire to transmit up to the shop. And it's important, how many wires you go to will really increase your expense. I have one wire in the ground here. If I remember right, it's an 8-gauge copper wire. It goes down right there and goes through a ditch up to the building, and I'll show you that next. So this is the other end of that wire, again looking back down at the array, and you can see I've got a solar disconnect right as it enters the building. In my area, and I think most areas, code is going to require a disconnect, and they are going to want to disconnect on each wire that you have in the ditch. So the older technologies, you weren't allowed to go, or you weren't able to go up to as high a voltage. So say you were transmitting at 96 volts. Well, to do the same amount of power, I'd have to have four wires in the ground, or I'd have to buy much bigger wire, which gets expensive really quickly. And I would also lose more in the transmission. When you have high voltage, you don't need as big of a wire, and you have a lot less amperage, so you're able to transmit power with less loss. That's why the power lines overhead, like these up here, those are operating on, I think this is a 6800 volts, I'm not sure, but they operate on high voltage until they get to your house, and then it's transformed down to go into the house. They don't send voltage around at 240 volts, because they would lose so much. The amperage would be so high, and these wires would be prohibitively large. So the high voltage helps you in your transmission. It decreases the size of the wire, the number of wires, and every wire you'd have in the ground, I'd need a different disconnect. So if I had two or three wires, I'd have three disconnects here. This is also an AC disconnect, which was required by my power company. So now let's go inside and see what this is hooked to. So here we are at my inverter, and in this metal clad armor cabled wire is my 360 volts DC. Code in my area requires that the DC line is in metal cladding. And then this is my inverter. Now this is a grid-tied inverter, so what this what this inverter does is it senses the grid, so it sees a sine wave doing its thing, and it says okay I've got power in my DC line. So it inverts that power from 360 volts to two legs of 120 to make a 240 volt single phase like like the standard power is around here. It synchronizes that power with the sine wave that it senses in the grid, and then it puts it back into the panel box. It puts it in this line and goes directly into my my grid power. The advantages of this inverter, the 360 volt input allows the inverter to be much smaller and to generate more power in a more compact and much cheaper package. A simple way to think about it is you're taking 360 volts down a little bit to make two legs of 120, you're not doing a huge jump up. I think that's where inverters have the most struggle. So when you get a battery backup, you're going down to the voltage of your battery bank, which oftentimes is 48 volts for a decent sized system. And taking power from 48 volts up to a 240 volt AC system is more difficult, requires a lot more engineering and hardware in your inverter in order to accomplish and makes everything more expensive. Now just to show you, I'm going to go into the battery backup side of things later, but right here I've got my battery backup inverter. And I don't know if you can see how much bigger it is, but this thing probably weighs more than twice as much. And it's much deeper, it's wider, and it's taller. I mean everything about it is bigger. And that's because this is capable of taking 48 volts DC and making it into 240 volt single phase power. Let's go look at where this service panel is hooked into the grid. The other end of this line is that panel we were looking at beside the inverter. So when the grid-tied inverter is making power, it is coming back up this line. It's coming into this box. Now if I've got a voltage drop to the house, because there's loads at the house that need to be met, the current's going to pick the path of least resistance. It'll go here and it'll get used. It'll never go through the meter, it'll just go straight to the house. If the house doesn't have a voltage drop, in other words there's not a big load there sucking up a bunch of power, then it will go back into the the meter and run backwards down into the ground, up the power pole, backwards through that transformer, and back into the line, and back down to someone else's house. So how does this inverter send power back into this, into the grid? Well basically it's just upping the voltage a tiny bit, maybe a tenth of a volt. I'm not sure exactly how much, but it doesn't take much. The resistance of the grid, or the impedance of the grid, is very low. It allows current to flow readily. So even just a tiny voltage difference here will readily flow into the grid and go either backwards through my system and back up the power lines, or it will go to my house which is on a different panel but it's connected through the same input as this. Here you can see the power output. It's cloudy right now, it's getting ready to rain, and i'm getting 2,000 watts at 378 volts and it's putting out 251 volts ac. You see it's constantly adjusting those numbers to keep the flow going the way it needs to go. So here we are on a sunny day, midday, and we're getting just under 8100 watts. So i've got 305 watts per panel at 36.4 volts. Now this is a solar edge system and that's a relatively new technology and it has optimizers. What an optimizer! It's this device right here and each panel has its own optimizer. If you look down each one, each one has one. And that basically communicates through the power line with the inverter so that the inverter is able to handle each panel separately. And that makes the system more efficient. It used to be when you had series, these 10 panels are wired in series, when you had things wired in series, if one panel didn't perform as well as the rest, then the entire series was cut down to that lowest common denominator. In this system, at least what i'm told is that this this prevents that. So you can actually knock out a panel and the rest of them will continue to produce. So that's the basics of a grid-tied system. In the next video i'm going to show you how to retrofit a system like this with a battery backup inverter so that you can use it when the grid's down.