The Design Process

Questions for the design process

To be sure your system will match your current and future needs, there are a few questions that help this process:

1. What vehicle do you own (or plan to own) and what electrical system does it have currently?

2. What are your daily energy needs?

3. Where and when do you like to travel? 

4. How long do you want to be off-grid at a time?

With this information we can plan the needs for solar panels, alternator charging, generators and/or shore power.

1) Describe your vehicle and any current electrical components. 

Is your current or planned vehicle a skoolie, a conversion van, an RV, a trailer or something else?  What does the vehicle have currently to power the living area? This information helps define the size of the roof, the amount of  space in the vehicle and what equipment we should be incorporating into the design. 

2) Define your daily energy needs.

Doing an "Energy Audit" is a key step in the design process and can actually take a bit of time to be complete. The goal is to generate a list of all the components in the vehicle that will use power and then estimate 2 things for each component: A) the watts it uses when operating and B) the number of hours per day you would like to use it. You then multiply the watts and hours to get "Watt-hours" needed for that component. Adding up all the components gives you the total energy needs for a day, which is a useful number when designing the system.  

A spreadsheet can be very helpful for this list and allows you to create different versions. For example, if you want to conserve power, maybe you don't run the electric tea kettle at all, but when power is plentiful, 30 minutes a day would be great. 

Some components like LED lights are easy to estimate as they may list their wattage in the description. Some component list amps (A), and you must multiply by volts (V) to get watts. (See "Electricity Basics" Page for more information.) For example a 12V water pump that uses 5A when running, uses 60W (12V x 5A). Other items like a refrigerator are trickier as it might use 150 watts when the compressor is cooling it down, but that is not on all the time so the number of "duty hours" per day might be only 8-12. Using a "Kill-o-watt" meter or similar brands by plugging it into the actual fridge while it is working can be a good way estimate Wh/day.  Also, add about 10% to the Wh for all AC components because the DC->AC inverter is generally only 90% efficient. 

3) Predict your travel patterns.

Do you stay in campgrounds most nights with shore power available or go off-grid for weeks at a time? Where in the country do you tend to go and in what seasons? How long do you stay in the same spot before moving? Answers to these questions can help define the relative value of charging the batteries using solar power, using an engine's alternator or plugging into shore power or a generator.

4) Decide how long do you want to stay off grid .

The number of days you want to be off grid will put a focus on your solar panels and the total size of your battery bank. Using the energy audit we can figure out how much battery you will need to roam free for as long as you want.