Please note, this article is a work in progress as of 07/17. I am routinely adding to it and working through organization. Please check back soon as updates roll in …or feel free to ask a specific question if you have one!
Overview:
There are many aspects to consider for solar design and installation. Broadly (very), there are two basic steps, sizing and implementation. We’re going to explore both topics in significant depth to help provide general information as well as much of the practical knowledge needed to design a system.
Solar panels are rated in watts (W). When comparing solar panels, the most important parameters (other than physical dimensions) are the watt rating and the voltage rating. For a given installation, the voltage needs to be compatible with the batteries and charging system on the boat (typically 12V, but sometimes 24V or more). For most of the writings here we will assume a 12V system, but there will also be information that digs a bit deeper into the benefits (and drawbacks) of higher voltage panels and/or battery banks.
Sizing:
What do you want to do with the solar energy you collect? For many, keeping a main/house battery topped off might be the only need. If a boat is only used a few times a week or month, and a few lights/instruments and a VHF are the only power needs, a small panel (~15W-30W) is probably adequate. If a boat is used more frequently, or you have greater power requirements, you will need to collect and store more energy. For those of us moving towards living aboard a boat, this is certainly the case.
So, more precisely, how do we figure out what is needed? It would be great if we could simply collect data over a period of time and monitor our real charging capability and real usage. This is certainly an option for a system that is already in place, but from the perspective of a new design, we need to focus on what we know and several assumptions. The electrical devices we have (or plan to) have specifications that should include power requirements. These we know. What we must assume is how much energy we can actually collect relative to our panel ratings, and how frequently we turn on various lights and electrical devices on our boat (actual power consumption).
As a side note, if you would like to get a real world picture of power consumption prior to installation of a new/upgraded system there are affordable power meters. These have the benefit of good accuracy and cumulative monitoring. They can be used over a period of time to monitor either solar charge power or power usage over time. If this sounds like a good option, there is more information in this article.
Implementation:
Parts of the system.
Physical panel install, wiring, storage, charge controllers….