Friday, February 17, 2017

Solar on wheels

Here's a look at the small solar setup on our travel trailer.  It doesn't provide gobs of power, but it has made a huge difference in our ability to live without hookups for days at a time.  We are now usually water-limited, and with good water conservation (and showers somewhere else) we have dry camped for up to 2 weeks at a time.  That wasn't possible without the solar system.

It doesn't give us enough power to run the air conditioner, but it easily keeps the lights on, the fridge running, the phones charged, and the water pump available.  Slightly more power is required to run the heater (electric fan/propane heat) and to turn on the inverter for AC plug power for the laptops, printer, etc.  Depending on the amount of daily sunshine, we can also use the microwave.

We have a propane generator as a backup system, which we did resort to using during one week at Rainier National Park with mostly-shaded sites and several days of rain.  With our inverter/charger, we don't need to run the generator very long to recharge the batteries.

The solar panel seemed large when we bought it, but nowadays it might be considered old-fashioned.  It's 205 watts and fits nicely on the roof of the trailer:

Another view, with a shout-out to TREE (Texas Responsible Energy and Efficiency) in the background:

The two lead-acid batteries that ride on the front hitch - better than the batteries that came with the trailer originally, but still only 220 Ah capacity:

John did several modifications to the trailer in order to install and wire this system, and I will be forever grateful for his solar and carpentry skills.  The side compartment that John added for installing the electronics:

The largest component is the inverter/charger which is used to convert DC from the battery to AC electricity.  Or AC from the grid to DC to equalize and charge the batteries.  It's a MagnaSine with true sine wave inverting for the "cleanest" AC power that works best with electronics like computers.

We have learned a great deal about the various electrical systems within the trailer.  The biggest detail is where DC vs. AC power is being used.  A normal house runs almost strictly on AC power, but an RV or travel trailer has a combination system.

For example, things that run with DC power include:
The refrigerator (can choose DC + propane or AC power)
Lights (all LED now)
The motor that drops the bed down for sleeping and lifts it for storage
The water pump (when using tank water instead of a city water connection)
Controller for the water heater (for burning propane)
A DC power plug that John installed so we can USB-charge our cell phones and iPod
Water/sewer tank level monitor
Propane detection system

AC is used for:
Heating water (can choose to use AC electricity instead of burning propane)
AC outlets for anything you plug in, with the exception of the DC plug noted above
The refrigerator (when switched to AC power)
Air conditioner

When we're off-grid, the inverter takes DC power from the batteries and changes it to AC for the second set of items listed above.  The inverter itself uses power to run, so we generally leave it turned off unless we want to use the microwave or charge the laptops.  DC power is always available for the first set of items listed above, as long as the batteries have some charge remaining.

When we're plugged in, e.g. at an RV park, none of these details matter too much.  But we can still use the solar system to charge the batteries and supply DC power, depending on the sun situation.  Our current spot has a little too much shade.

With all that in mind, John designed a flexible system that we can configure depending on the situation.  The black box in the middle is the disconnect to the solar panel.  The white TriStar is the charge controller which regulates the flow of current from the solar panel to the batteries.  The red switch turns DC power on and off to the inverter.  And the gray box on the left allows us choose between using the inverter and bypassing it to use AC shore or generator power directly.

We started with a gasoline-powered generator, but found that it was hard to maintain.  If we didn't use it fairly often, it would gunk up and eventually require a rebuild.  Plus we had to keep gas in the tank.  The new generator is plumbed to the propane line, it doesn't need to be exercised, and it has been very reliable.  Our only question is whether we really need it at all, or if we should be using this space for a larger battery bank:

The displays inside the trailer aren't super high-tech but they do the job.  The "100" on the top left is the charge status of the batteries (100%) and this display will also show amps charging/being used along with the voltage at the batteries.  The middle buttons are for the ramp light and activating the bed lift.  The Magnum on the right is the controller for the inverter.

The fuel gauge on the lower left is no longer being used since we removed the gas tank.  The white switch on the lower right is for remote start of the generator:

We have some thoughts on potential upgrades.  Ideally eventually we could remove all propane completely.  This will require increasing our solar and battery capacity:

- More/higher wattage panels

- Lithium batteries with way more capacity (which will likely allow us to sell the generator)

- Switching from propane to using more electricity:
Heating water strictly with electricity, using AC power for the fridge, leaving the inverter on most of the time, changing from a propane stovetop to an induction cooker, adding a crock pot and toaster oven, and using small electric space heaters instead of the propane heater

The heating elements especially can really burn through (as it were) electricity.

- If we could accomplish all that, we could remove the generator and propane tanks, which would reduce weight to help balance out the additional battery and solar panel weight, and eliminate that source of fossil fuel use.

- Oh, and convert the truck to electric...!  We can dream  :)

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