A geek’s quest for a (very big) solar fridge

Like many solar installers, I’m always on the lookout for energy-efficient products and recently, I started looking at portable cool rooms and learned a few things along the way.

With a family re-union coming up fast the logistics of feeding 30 people in a remote location was on the agenda and along with that, refrigeration. Pretty quickly, it was decided that a mobile cool room would make sense, because the bush retreat we were heading too only had a very small domestic fridge.

But it quickly got interesting because firstly, the place we are heading to turned out to be run by solar. With multiple guest accommodation,  a potters studio and so forth, it’s very well set up having a 30kW solar array, a big battery bank and  a 30kw back up generator. And it just happened that I knew the suppliers. A quick phone call revealed a bit more about the system including that there had recently been some minor problems with the generator auto start. Given that we are heading there in a low solar part of the year, I figured I better do some homework, lest we break their solar system!.

I rang a bunch of cool room hire places and predictably, absolutely no one had any idea at all about the power consumption  of their cool rooms. Promised phone calls weren’t returned and everyone seem perplexed at why I wouldn’t just “take a 5kVa gennie and be done with it”. The thought of spending 8 days and nights in a quiet, pristine bush setting while listening to a generator just freaked me out. I couldn’t do it.

So i started my solar geek quest for energy-efficient cool rooms and to understand the energy consumption of standard ones.

By my best calculation, a cool room is going to need around  20-30kWh/day; about the same as an average house. Now I may be wrong on this, but going by the specs and conversations I had, that seems to be it, which is pretty bloody lousy. I also discovered that a lot of mobile cool room hire places won’t actually let you tow these things, and especially not 600 or 800kms away. They want to deliver it for you so it just isn’t practical.

When I started googling, I discovered that fishermen and some camp groups have grappled with this issue too. Most resort to ice or the lucky few use 12V camping fridges with solar but the capacity (around 60L) wasn’t going to cut it after we visited cousin Troy’s farm and got a few freshly slaughtered beasts on the way up bush. We needed more like 800-1000L of capacity. The other issue is that my learned better half knows food health, having been in catering and hospitality most of her life and temperature regulation is crucial for good hygiene.

Then I got a great suggestion from a local hire place, who were the first mobile refrigeration company I found who seemed to understand the issue. Chill Logistics were incredibly helpful and understood what I was trying to achieve and offered a solution I hadn’t seen before. The EuroEngel is a 330L portable cube which I could fit on my ute and most importantly was built around the awesomely efficient Danfoss 12/24V compressor. I could run it on 12V from the car on the way up and then plug into 240V when we arrived and instead of using 20-30kWh day I would only use around 2-3kWh/day (based on around 100W continuous, average). Now having said that I would need two to three units to get the same fridge capacity, so lets just settle on 3 times less energy per day.

Then today, blow me down If I don’t see a van parked across the road unloading bunch of food with one of these units in the back. In a truly solar geek fest inspired moment, I was nearly cleaned up by a car in my haste to bail the driver up for valuable insights.Turned out (the driver was really helpful) that this was a different unit, made by Dometic (Waeco). The CF850 is almost 3 times bigger at 850L and to my surprise even has an inbuilt battery “good for about 8 hours”.  With some help from Dometic, I learned that this unit uses a maximum of 150W and thus around 3-4kWh/day max. Now we are talking.

I reckon 3 of LG Solar’s new 290W panels would just about keep up although storage still needs to be better sorted for a long trip like I have in mind, without the benefit of a big solar hybrid system.

The lessons here are:

1. Cool rooms are crap and no-one seems to understand their energy consumption
2. There is a clearly an opportunity for someone to specialise in energy-efficient portable refrigeration products
3. The new breed by EuroEngel and  Dometic/Waeco look awesome but are very new to Australia
4. Someone needs to do some more advanced testing and data logging on these new products

Between fishing expeditions, camp groups, big family get together’s, school groups, festivals, film crews and mobile food transporters, I reckon there has to be an opportunity to avoid a lot of generator use and save a bit of energy here, just by being smarter.

Gotta love an opportunity.

This article was first published at Solar Business Services. Reproduced with permission.