Fruit & Veg dehydrator

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Fruit & Veg dehydrator
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dougal

Joined: 15 Jan 2005
Posts: 7184
Location: South Kent

Posted: Fri Oct 19, 07 6:10 pm Post subject: Re: Fruit & Veg dehydrator

keithatbeaugut wrote:

Does anyone have plans for constructing a good solar dehydrator either for outside or in the greenhouse, please?

For one suggestion, take a look...
https://forum.downsizer.net/viewtopic.php?p=85144#85144

keithatbeaugut

Joined: 14 Oct 2007
Posts: 16
Location: Puy-De-Dôme, Auvergne, France

Posted: Sat Oct 20, 07 7:29 am Post subject:

Thanks for that. I want to make something that looks good in addition to performing well.

The book being pushed looks as though it will help me to do that and, as I can get it from Amazon UK delivered to France for less than £8 I have ordered it.

If interested, here's the link.

It will go on the project list, ready for next year's bounty, and I shall try to remember to report on how it goes.

Keith

dougal

Joined: 15 Jan 2005
Posts: 7184
Location: South Kent

Posted: Sat Oct 20, 07 10:05 am Post subject:

keithatbeaugut wrote:

Do let us know what sort of refinements they might suggest.

My expectation is that the basic elements are pretty immutable.
- a box to contain the goods to be dried, with appropriate grid shelving, warm air inlet and some exhaust vent arrangement - oast house design does of course show what works (their purpose was hop drying!)
- a solar collector, with an outlet to the drying chamber and an inlet that prevents wind from blasting the air out of the heat collector. To be most effective the collector needs to be tallish, shallowish, and angled at 90º to the sun (so the optimum angle depends on the latitude, the time of year, and the time of day that you get the best solar exposure). Angle adjustment would seem a useful refinement.
Naturally, the collector is going to have a black energy collecting surface and a glazed (ideally heat retaining) top surface. Insulation, as always, would be good.

Do let us know how your solar dying progresses!

Dee J

Joined: 22 May 2005
Posts: 342
Location: West Devon

Posted: Sat Oct 20, 07 10:25 am Post subject:

Built a solar drier this year... according to the general designs available. Metal collector painted black, glass glazing... about 1m high by 0.5m wide. Plastic bug-proof box with fly screens on airways and 3 layers of fridge shelves for produce. Tried drying pear halves (dipped in lemon juice to limit browning). But , overcast /cloudy for a week (Devon, about a month ago) - and everything just went mouldy. Much more sun needed - and maybe only try lower moisture content fruit only. Back to the drawing board.

Dee

dougal

Joined: 15 Jan 2005
Posts: 7184
Location: South Kent

Posted: Sat Oct 20, 07 11:01 am Post subject:

I feel that solar drying is going to be perfectly viable in Italy, central France, much of the southern USA, etc...

In the UK, one is going to require rather a large collector, and have a smallish "payload" capacity...

The size (and insulation) of the collector (and the incident solar radiation) is going to determine the amount of 'power' available, and the amount of airflow is then going to determine the temperature reached.
Unfortunately, round here, its usually not many minutes before clouds change things, so the temperature and airflow are going to be very variable...

I wonder how a standard conservatory could be persuaded to vent through a drying chamber... ?

keithatbeaugut

Joined: 14 Oct 2007
Posts: 16
Location: Puy-De-Dôme, Auvergne, France

Posted: Sat Oct 20, 07 11:16 am Post subject:
Actually our climate here doesn't differ too much from yours, being 2000 feet up in the Massif Central and only 60 Kms north of and thus affected by the volcano chain. Still, the indications are good for a well made unit, and I may consider locating it in the greenhouse I keep promising to buy as soon as the cash is there. Keith

ken69

Joined: 17 Jul 2005
Posts: 316
Location: Norfolk

Posted: Sat Oct 20, 07 12:24 pm Post subject:

I made this, Keith, from a 'copper', it's insulated and contains an 8litre cooking pot painted black. It produces hot water and sometimes very hot water in the summer. Othertimes it's warm and these days hardly worth using as the water is lukewarm, tho could be additionally heated in a kettle.
Havn't tried dehydrating fruit and veg but, given Dougal's refinements would probably work. Certainly there is enough retained heat.
It's an old fashioned washing 'copper', actually cast iron with an original lining of copper.
A small tin bath would also suffice. The problem is the fruit matures when the sun is getting weaker.

ken69

Joined: 17 Jul 2005
Posts: 316
Location: Norfolk

Posted: Sat Oct 20, 07 12:27 pm Post subject:
Here is a smaller system, usually sited in the greenhouse, heats a small kettle for hot water. Still usuable hot water but not so fierce heat as the 'copper'.

keithatbeaugut

Joined: 14 Oct 2007
Posts: 16
Location: Puy-De-Dôme, Auvergne, France

Posted: Sat Oct 20, 07 12:45 pm Post subject:

Thanks Ken. I'm finding myself torn between something that works well and looks good, and would not be out of place on the terrace, and something that works well but not necessarily on open view. The alternative is always an electric dehydrator, but I don't really want to go down that route, although a hybrid machine - solar but with a backup heat source (possibly a light bulb or maybe even small candles) secreted inside it for those days when the sun doesn't perform.

Keith

ken69

Joined: 17 Jul 2005
Posts: 316
Location: Norfolk

Posted: Sat Oct 20, 07 2:31 pm Post subject:

Know what you mean Keith. This odd looking set-up of mine enough hot water in the summer for personal washing, dish washing and overnight pre-soaking clothes (and finish off with cold wash and spin).20litres in total but never use it all. Might try converting some to dehydrator next year for early plums and such.
Don't know if you get BBC 2 or Channel 4 but last week Ray Mears liquidised some hawthorn berries, it set like jam and then he dried it. Came out was dry as jerky and tasted sweet. Quite possible, I would have thought, with dried beans, sweet and sour 'jerky' plus stored apples and fresh garden produce TO SWITCH OFF THE FREEZER.

dougal

Joined: 15 Jan 2005
Posts: 7184
Location: South Kent

Posted: Sat Oct 20, 07 3:42 pm Post subject:

keithatbeaugut wrote:

Actually our climate here doesn't differ too much from yours, being 2000 feet up in the Massif Central and only 60 Kms north of and thus affected by the volcano chain. ...

Keith, you're maybe selling yourself short!

The insolation figures for Lyons compared to London show rather more incident solar radiation - particularly in June/July/August.
Lyons 5.40 / 6.03 / 5.23
London 4.51 / 4.74 / 4.01
figures in kW/m2
Looks like almost 20% up on London!
https://www.navitron.org.uk/solar_insolation.htm

I found some figures to compare Bourges (North of you a bit) with Manston (my nearest airport/weather station).
The climate is indeed kinda similar - BUT -
- Bourges is 5ºC hotter on *average* during the summer months
- and gets at least an hour more sunshine per day on *average*
https://en.allmetsat.com/climate/france.php?code=07255
https://en.allmetsat.com/climate/france.php?code=03797

Then there's your altitude - at 2,000 ft you have noticeably less atmospheric pressure - so water boils at a slightly lower temperature, and for the same temperature/air humidity, evaporates faster.
(I spent nearly three years at 5,000 ft in the tropics...)

So, something like (they are the most 'local' figures I could find quickly) 20% extra summer solar energy, an extra 5ºC, and an extra hour of sunshine per day, plus altitude assisted drying... I think you have the advantage when it comes to drying conditions, sir!

ken69

Joined: 17 Jul 2005
Posts: 316
Location: Norfolk

Posted: Sat Oct 20, 07 4:05 pm Post subject:
Wow some research that Dougal. Two layers of glass, Keith does reduce growing conditions in a greenhouse, so also perhaps with solar drying. On the other hand equipment would be pre-warmed. If DIY you will probably finish up using a Mk !! version anyway.

keithatbeaugut

Joined: 14 Oct 2007
Posts: 16
Location: Puy-De-Dôme, Auvergne, France

Posted: Sun Oct 21, 07 2:02 pm Post subject:

I'm thinking that if I make it to a sufficiently high quality I shall be able to experiment and explore options.

That's the plan anyway.

According to my neighbour, who has lived next door for nearly three decades, a hot summer reaches 40C with, because of the proximity of the volcano chain, a good number of thunderstorms; and a cold winter reaches -20C.

Our experience so far was (last year) max 33C, min -12C. This alleged summer is nothing to judge by - I hope!

ken69

Joined: 17 Jul 2005
Posts: 316
Location: Norfolk

Posted: Mon Oct 22, 07 8:09 am Post subject:

I would make a prototype version incorporating all the essential features such has heat, space and ventilation, then experiment from there.
Once you know it works, and that you yourself are happy with the manual side of loading and tending and unloading and so on, then make a de luxe version.
Never used one, but it could be that you have to hang about so as not to overdry. Can the stuff be dried in one day, would you need to insulate at night. ??

keithatbeaugut

Joined: 14 Oct 2007
Posts: 16
Location: Puy-De-Dôme, Auvergne, France

Posted: Tue Oct 23, 07 3:38 pm Post subject:
You make a good point Ken, and your questions are valid. I really shan't know until the book arrives - hopefully that will be quite soon. In fact I shall check with Amazon now! Keith

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