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Robinjw13

DIY (in 20 minutes) Refrigerated Van - Ideas ?

I've seen the DIY fridge topic but I'm looking for ways of keeping freshly-harvested vegetables cool for 2 to 3 hours in a large ply-lined panel van. Internal area is 6 cubic metres.

I could use old polystyrene fish containers but (a) they smell and (b) they would not be big enough for the plastic containers the produce will be in. I've thought about lining the van sides with polystyrene or foam wall insulation but neither of these products are very sound environmentally. Is there a plant that reduces temperature (hey, you never know!)? Would a couple of large wooden boxes do the trick, maybe double-skinned and insulated? Or should I just wrap everything in large sheets of polythene?

Looking for simplicity, economy and preferably re-cycled or naturally available materials. All suggestions gratefully received & I'll let everyone know what we do & what works - Thursday is the first delivery.
boisdevie1

I've heard that if you have a container and put a wet teatowel or something similar across the open top of the container then when the water evaporates this leads to a drop in temperature. Could this idea not be used. i.e. have big boxes with wet towels across the top?
sally_in_wales

I suspect wrapping everything in polythene or enclosing it will make it sweat and have the opposite to the desired efffect. A through flow of air would probably be a good idea, can you arrange some sort of ventilation for the van without compromising security?
wellington womble

Re: DIY (in 20 minutes) Refrigerated Van - Ideas ?

Can you get polystyrene meat containers? They are bigger than fish, the meat is generally wrapped, so they don't smell and are really, really efficient at keeping things cool. My box scheme gives everyone a really big one, to leave your stuff in if you're out. - I could ask them where they get them from, if you like.

It's so good, I have chucked the coolbox, and take it camping. And make ham in it!
MarkS

A van in the sun is more or less an oven. I think that insulation is required. But remember that the insulation just slows the temp change between the inside and outside, so you also want to think about getting the initial temp down.

I would look at insulation combined with suitable vents so you get air flow through when going to wherever you will collect the stuff.

You might also think of some way of shading the van from the sun (I'm being optimistic here aren't I? Sun what Sun?)

Or buy a refrigerated van ?
dougal

I hope its a *white* van... seriously, it'll be much cooler in the sun than a black one.

Insulate it. Especially the roof (sun), and don't forget the floor if you get any heat from the engine/exhaust.
Rigid foam roof insulation would likely give you the best insulation. Bubblewrap and double-sided sticky might be the easiest bodge!
The better the insulation, the less cooling you need! (So the more sustainable the operation becomes).

Evaporative cooling works by changing water into water vapour. Absent anything else, it needs a large airflow and a large surface area evaporator.
It isn't exactly ideal for a fairly enclosed space.

I'd suggest that you see if you can source large blocks of ice. (Abatoir?)
If you could mount a couple of gallons of ice high in the van (cool air sinks) then that should hold down the temperature for a few hours.
Problems to be dealt with would include dealing with meltwater, and securing the ice so that it doesn't slide about too much, as it gets smaller, as it melts...
How about putting the ice in a deep container (I'm thinking of something like a milkchurn, less than half full of ice) and hanging it from the van roof. Elastic bungee cord could be used to gently limit the swinging.
"Dry Ice" would be easier to work with, but I'd hesitate to use it in the same compartment as the driver. So OK for a big van with a separate load compartment - which incidentally would minimise chilling the driver!
The rate of cooling could be adjusted by adjusting the blanketing (bubblewrap?) of the cold container.

My suspicion would be that the financial and energy cost of a bit of ice would be pretty trivial compared to the transport fuel.
Shane

A van with no active cooling that's been sitting around outside will be at ambient temperature regardless of how well insulated it is. If a (black) van is sitting in the sun, you can expect the surface temperature to reach around 85C. As pointed out, insulation will slow down the rate at which the inside of the van heats up, but it won't prevent it happening.

When you put your (presumably) refrigerated vegetables into the van, they will exchange energy with the surroundings and will start to heat up if the van is warmer than them. They will take a little heat from the air in the van (happens quite quickly) and lots of heat from the van walls (happens quite slowly, as the heat has to go through the air and any container that the veg is in).

There's two ways of keeping the stuff cooler. Either you prevent the heat gain from the air in the van (i.e. put the stuff in insulated boxes), or you accept that you don't get a great deal of heat from the air and you prevent the air in the van from heating up once the veg has cooled it down (i.e. either insulate the van walls or provide some means of active cooling).

Because I'm a bit nerdy, and it would be interesting to see the result, I'd be tempted to build a internal wooden skin in the van. I'd channel air flow from vents at the front to go between the van wall and the internal wall, which would reduce the amount of heat transmitted across the gap when the van is in motion. I would then insulate the inside of the inner wall with a "green" insulated material (the stuff made out of sheep wool or old paper or something) to further prevent heat ingress.
Shane

Dougal's reply would of course be easier, but less interesting Laughing Laughing
wellington womble

Dry ice is incredibly useful stuff for cooling - we used to take coolboxes of it camping, and it would keep things frozen for a week, if you were careful. And of course there is no melt water to cope with. You need to make sure there is ventialtion, but other than that it should be a problem. Don't know where you would get it though - himself used to get it from his company - he was a salesman for a firm supplying commercial cryogenic gases. I also think they are rather energy intesive to make.
Rob R

Is this a one off or a regular thing?

If it's a one off, you could try the rather Heath Robinson suggestions, but if it's regular then it'll be worth investing a bit more resources (possibly not as 'environmentally friendly', but in the long term the net loss will make it worth it).
RichardW

Shane wrote:
Because I'm a bit nerdy, and it would be interesting to see the result, I'd be tempted to build a internal wooden skin in the van. I'd channel air flow from vents at the front to go between the van wall and the internal wall, which would reduce the amount of heat transmitted across the gap when the van is in motion. I would then insulate the inside of the inner wall with a "green" insulated material (the stuff made out of sheep wool or old paper or something) to further prevent heat ingress.


Thats how the safari roof works on old landrovers. They have a fake roof that heats up but the air space under it is vented so the cars movement causes the air to rapidly change preventing the real roof from getting hot so keeping the cabin cooler.


How long will the goods be in the van?
How hot will it be at delivery time (IE could you deliver early morning or late at night)


Most dry / veg deliveries are not done on refigerated vans.

Justme

PS I have a van for sale but its more for display / market selling.
Robinjw13

Wow, thank you for some pretty serious suggestions! My brain only works well in the mornings so I'll read this again and give it detailed thought tomorrow.
Shane

Dammit - somebody thought of it before me! Laughing
Robinjw13

This is not a one-off, it's for weekly (later twice-weekly) deliveries of fresh produce - vegetables and salad leaves. I decided against a refrigerated vehicle to ensure greater versatility (we are selling the family car) and lower running costs. Journey time is expected to be 2 to 3 hours after which the van (colour = 'furnace red') can get as hot as it likes.

The wet towel idea sounds the best emergency quick & simple fall-back solution. One of our customers had already suggested meat containers so I will follow that up now that it has been suggested again.

Giant ice cubes? Hmm, what about the fuel costs with all that extra weight? I've seen something called Nanocool & other ice packs/gels but can't find a price yet. Also thermal blankets - again no price yet but see http://www.controlla.co.uk/controlla.htm and http://www.polartherm.co.uk/products.aspx.

The van will be ply-lined so I may be able to insulate behind the timber. We have mullein (Verbascum thapsus) self-seeding here and apparently the leaves (thick and furry) are good insulators - see http://www.pfaf.org/database/search_use.php?K[]=Insulation.
Problem - after a few weeks using plant material as insulation I will end up with a mobile compost heap generating heat!

Hope some of the above links will be useful to others. Any further ideas welcome and again thank you for the previous very useful advice.
dougal

Robinjw13 wrote:
...
The wet towel idea sounds the best emergency quick & simple fall-back solution. One of our customers had already suggested meat containers so I will follow that up now that it has been suggested again.

Giant ice cubes? Hmm, what about the fuel costs with all that extra weight? ...

The van will be ply-lined so I may be able to insulate behind the timber.

1/ Weight for weight, you will get *much* more cooling with ice rather than a "wet towel".
2/ Using evaporation is limited by the amount of airflow you can generate.
3/ Depending on the veg in question, I'd almost be more worried about the effects of high humidity than high temperature...
4/ If you Google for
"dry ice" sussex
you'll get plenty of ideas for potential suppliers.
5/ If you are taking off the ply lining and want to insulate with a 'renewable', then look to wool-based insulation, not compostable veg material (though there are some treated paper insulations you might want to check). Personally, I'd go for high performance insulation.
The energy costs of the insulation are a truly miniscule amount compared to the energy cost of building the vehicle. More like the energy costs of making a single delivery run, I'd think.

Good luck!
RichardW

Ensure what ever you choose to do is given the OK by your EHO BEFORE you do it.


Justme
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