Desert farm, Big pump, Batteries?

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Re: Desert farm, Big pump, Batteries?

Postby gfsben » Wed May 31, 2017 6:23 pm

I looked through that video. It is definitely headed in the right direction- designed for solar -DC input, built in Inverter, VFD running a high COP scroll compressor. It also has heat recovery/hot water output as well as the chilled loop. I fished out the website http://multiaqua.com/index.php/chillers/mhrc-ae
I'm sure its still pretty expensive... and the wrong side of the pacific.

In response to other comments: The coolroom is only 3m by 4m. It's sitting on an (un-insulated) slab that is the floor of our packing shed. We probably put around 6 tonne of dates through the coolroom throughout the season. There was probably never more than 800kg in at any one time. We would be aiming to put around 10 tonne through in the future and store more for longer.
It would be good if it were bigger, then I would be tempted to put an exposed tank of coolant filled with PCM/ice straight in the coolroom and aim for mostly passive heat transfer. But I think that would steal too much room. We could add on to it, and we may.
That would require either a liquid chiller outside circulating glycol inside, or a condensing unit outside and refrigerant lines running inside to a submerged evaporator. Both solutions look to involve fairly high costs.

I am leaning towards something like one of those 2kw drop in units with the forementioned copper coil evaporator that would hang below the condenser, submerged in a very well insulated IBC tank that would be mostly filled with PCM/ice packs. That whole unit could sit outside and then i would pump glycol from the ibc through heat exchangers in the coolroom. I would plan on the PCM and glycol to run at somewhere just below zero to keep the COP as high as possible.
If this struggled to draw down the temperature when we added hot dates, then we could just run the existing drop-in for a bit to get it cold, then rely on the stored coolth to keep it cold.
I am trying to envisage something fairly simple to commission. I can handle plumbing of coolant and heat exchanges, but it would be good to be able to get a fridgie in town add the custom evaporator and gas it up. Getting people down to the farm is pricey cause of the roads/remote.
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Re: Desert farm, Big pump, Batteries?

Postby Gordon-Loomberah » Wed May 31, 2017 7:37 pm

gfsben wrote: There was probably never more than 800kg in at any one time.


For cooling hot dates to coolroom temperature: the good news is that the Specific Heat of dates is very low, just 20% of the Specific Heat of water - 0.84 vs 4.18 kJ/kg degC

So (ignoring any inefficiencies in the heat exchange process) for equal weights of cold water and hot dates:
1 deg increase in the water temp = 5 deg decrease in the dates temp. Of course as they approach temperature equilibrium the heat echange will become very slow, so you'd want to run the water temp as low as possible. This may require using a saline solution, which will decrease the Specific Heat along with the melting point.
Spacing the boxes of dates apart so that there isn't a big mass of them in one block would be necessary too, although no doubt you already know that!
http://gunagulla.com Loomberah weather and astronomy including live solar radiation intensity and UV + Gunagulla aquaponics, organic eggs and cherries
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Re: Desert farm, Big pump, Batteries?

Postby Warpspeed » Fri Jun 02, 2017 10:46 am

I suppose a good start to all this might be to monitor your existing system for power usage pattern.
That should give you at least a bit of an idea about heat loading under various operating conditions.

Although its not the ideal time of year for doing this, the only real difference to summer is the outside temperature. Its still possible to use the data for some very rough thermodynamics calculations.
If you can carry on data logging, by the time we reach mid summer there should be a pretty complete picture of what is required.
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Re: Desert farm, Big pump, Batteries?

Postby gfsben » Tue Jul 18, 2017 11:44 am

Yep monitoring is on the agenda. Its a bit of a mute point right now though as all the dates are sold and the cool room is off. We just have a fridge, computer and and multiple long range wifi transceivers plugged in.

I'm just going to step back to the original question for a bit, as we are just about to make the final decision on the pump and installer.
We are trying to decide over two options of submersible pump/controller/PV combinations. Both are capable of delivering around 340kL per day. Both are around $40-50 K fully installed with the Lorentz option being several thousand dollars more expensive.

So the option is a Lorentz PSK2-21 with 17kW of Trina PV

or a Grundfos 15A01906 SP 46-6 with Winaco PV

The Grundfos inverter - RSI, looks pretty bullet proof, its IP66, but the display and monitoring seems more rudimentary and less user friendly than the corresponding Lorentz version (which includes android tablet). Also the Lorentz has an obvious input and logging capability for flow rate from a water meter. Maybe the Grundfos has this but i cant see it referenced in the (100 page) manual.

The monitoring and control stuff is nice but probably what we would value more is the longevity and reliability of the pump itself. The extra cost is probably acceptable if the pump and controller lasts longer before replacement or repair is necessary.
Repairability between either option would also be great to know about.

Both installers are local, experienced and top notch.

Any advice based on real world experience would be greatly received. This is crunch time and we are going to make a decision in the coming days.

Cheers

Ben
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Re: Desert farm, Big pump, Batteries?

Postby gfsben » Wed Aug 23, 2017 2:56 pm

Just in case anyone is interested- We are going for the Lorentz. It should be installed next month.
I will endeavour to post some follow up as it happens and as we use it.
Really looking forward to some clean, silent and plentiful water.
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Re: Desert farm, Big pump, Batteries?

Postby Warpspeed » Wed Aug 23, 2017 3:12 pm

Yes, please keep us in the loop.
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Re: Desert farm, Big pump, Batteries?

Postby Helipos » Thu Oct 19, 2017 9:07 am

Any news or pictures?
Safe to say quite a few of us found this a quite interesting topic.
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Re: Desert farm, Big pump, Batteries?

Postby gfsben » Thu Oct 19, 2017 10:49 am

Yes actually. We just got the pump in and connected last week. Its running very well.

I will give you more pictures and details soon, but here is a sneak peak.
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pump solar array.jpg
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Re: Desert farm, Big pump, Batteries?

Postby australsolarier » Thu Oct 19, 2017 11:32 am

looking good
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Re: Desert farm, Big pump, Batteries?

Postby gfsben » Tue Jan 09, 2018 10:24 am

submersible pump.jpg

pump hanging .jpg

last bit of lowering .jpg
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