Components

Components

Let's go over the major components of a solar and battery system installation.

Solar Panels

There are all kinds of solar panels and all kinds of ways they can be wired in series or parallel to make just about any kind of system. But generally there will be one of two constraints that will influence the approach the design of a system for your installation: 

1.  How much area is available on your roof or other surface, or 

2. What size standard system can you use and afford

Series and parallel

A solar panel installation is arranged by putting the individual panels in either a series or parallel configuration, or some combination of the two.

The watts that are produced is the voltage times the current of the the individual and is constant. But either the voltage is cumulative (series), or the amperage is (parallel), but the watts are the same W=V times A. In the diagram below the watts are a constant 54W, either 18vX3a or 6vX9a.

Sizing of the Installation

Solar panel installation are generally sold in terms of watts (or kilowatts -thousands of watts). 

An installation can be any number of watts depending on what the site will will fit, or the installer can put in a standard amount of one of several sizes, usually 5kw, 7.5kw, 10kw, 12 km, 15kw, or 20kw. The advantage of the standard sizes is it reduces both the amount of customization the installer has to do and therefore help with various supply chain and warehousing they have to maintain. It's all about providing the best services while trying to keep the cost as low as possible.

Combiner Boxes

A solar panel installation may consist of several "strings" of individual modules, with in series or parallel. These strings need to be "combined" into the ultimate DC output of the system.

Inverters, Inverter/Chargers, and Chargers

This where it starts to get a little tricky because the next piece of equipment will depend on the type of installation.

Inverters

In a typical home installation, an inverter will be used to convert the DC from the solar panels into AC that can be fed into a house's AC electrical panel and also fed back into the utility grid to sell electricity to the utility company if the solar makes more power than is used by the house. 

Chargers

In a typical marine installation where there is no grid, a charger is used to directly convert the DC from the panel into DC to charge the house and starter batteries of the boat,

Inverter/Chargers

Just like it says, these units combine both functions into one unit that can provide both an AC output and charge the batteries.

Matching Input/Output

The key thing with all of these things is that it must be selected to match the other equipment on both the input and the output. So, in the case of the inverter, it must match the output of the solar system panels. Similarly, any charger must support both the battery chemistry (eg. lead acid, AGM, Lithium etc.) and the voltage (12, 24, 48, 56 or whatever).

Batteries

There are all kinds of batteries, as described elsewhere in detail. For our purposes in terms of solar installation there are basically four different types: Powerwalls, Server Rack, COTS (marine, RV), and the ever popular DIY for any number of purposes.

The chemistries can vary as can the voltages. Batteries can also be connected in series and parallel to produce the different voltages. The advantage of higher voltages is that they generally require less current, which saves money on wire size. Again, the important thing to remember is that the batteries have to be matched to the other system components and consideration. 

In any event, as a store of a lot of energy, any battery system is not to be trifled with and you should proceed with the utmost caution.

Wiring

Notice that there is all kinds of different wiring in a system and it is very important to use the right kind of wiring in the right place. There are big differences between the wiring outside subject to UV exposure for the solar panels and the inside wiring for a circuit. Similarly there are differences in AC vs. DC wiring. As a general rule, the higher the voltage carried on a wire, the smaller the wire that can be used which is kind of importance when figuring out the cost of the system.

One of the lowest voltages is a system is typically in the DC going to and from the batteries, so these will require the biggest wires.

This is particularly true of marine applications that typically rely on 12V systems. For example, if we use a 2000 watt inverter with a 12v system you are looking at 166.67 amps (W/V=A). We also need to account for several losses in the system such as inverter inefficiency and the resistance and associated voltage losses due to the length of wire used. Then we need to round up to the next higher wire size. So in this example we're talking about 2.0 wire gauge.

Because of the particularly harsh environmental aspects of the marine environment, there are also additional requirements on the wiring.

Lugs

Fuses

Switches and Disconnects

Busbars

Shunts

Layout