Using Solar in Heavy-Duty Trucking

For a detailed discussion on using solar in heavy-duty trucking, watch the recording of our Solar Myth Busters webinar. For a summary of the discussion, check out the outline below:

Why solar?

Solar allows batteries to charge without an alternator. Benefits can include:

• saving on fuel by using a green energy source
• adding hours to your APU run time
• keeping liftgate batteries charged, increasing charging opportunities
• ensuring reefer battery life without using extra diesel fuel

Key questions you should ask before equipping your fleet with solar

Before purchasing solar for your fleet, start off with these three questions:

1. How much power do I need?
   Power needs vary by application, but the general idea is:

• • Calculate the average load used
  • Use equation Watts = Amps * Voltage to determine need
  • Add 10% to account for efficiency loss
  • If you are running liftgates, check out our solar calculator

2. What type of controller does the system have?
   There are two types of controllers:

• • Pulse width modulation (PWM)
    • More cost effective
    • Less energy efficient
  • Maximum Power Point Tracking (MPPT)
    • Up to 30% more efficient
    • Higher price point

3. What type of panel does the system use?

• • Monocrystalline
    • Uses a single piece of silicon to form a cell
    • More efficient (15-20%), smaller footprint
    • Higher cost
  • Polycrystalline
    • Uses many smaller pieces of silicon to form a single cell
    • Less efficient (13-16%), larger footprint
    • Lower cost

Common myths about solar

Myth 1: the warmer the weather, the better solar works.

• Truth: solar energy is not generated by heat. In fact, a sunny, but cooler day, will produce solar energy more efficiently than a blistering hot day.

Myth 2:  the heat and light from fluorescent bulbs will turn on solar panels.

• Truth: technically speaking, fluorescent bulbs do turn on the solar panels; just not in a practical, usable way. Light bulbs emit a lower level of radiance than the sun, and it is the radiation that the panels use to charge batteries. Most solar controllers won’t even turn on with the low level of power that fluorescent bulbs produce.

Myth 3: the sunlight reflected off the moon can power the solar panels.

• Truth: again, technically speaking, the moon could turn on a panel; just not in a practical, usable way. The power ratio from the sun to the moon is 345:1. This once again results in the solar controller not even turning on due to low power output. Some companies do have moon panels in the works, but these are completely separate from solar panels.

Myth 4: solar works just as well on cloudy days OR solar doesn’t work at all on cloudy days

• Truth: solar panels do work on cloudy days, but output will diminish by between 50-75% due to a reduction in certain sets of wavelengths.

 

Resources

Our sister company Xantrex has two videos on solar that are particularly relevant to the discussion. The first one discusses the question, “How much solar do you need?” while the second discusses the differences between MPPT and PWM solar controllers.

For those running liftgates, try this handy solar calculator to determine the number of solar panels you will need based on your power use and location.

Finally, for those interested in outfitting their fleets with solar power, check out our solar offerings!