Desert farm, Big pump, Batteries?

Getting into the nuts and bolts of wind and solar power components, installation and performance issues, ask technical questions, answers and tips

Re: Desert farm, Big pump, Batteries?

Postby jaahn » Sun May 14, 2017 7:47 am

Hi Ben :)
A couple of general comments.
The existing pump. A well set up belt drive and the bearings would give very minimal losses. Usually losses are over stated by the opposition. A mono pump is also regarded as fairly efficient if it is working in its design parameters. I could also point out the losses inherent in the wiring with a down hole pump. Not to mention the fact it is electrical and way down the hole in a well. Expensive to get quality gear. :roll:

As has been pointed out already, by Warpspeed, ice is a phase change product and you do not have to buy it at great expense :mrgreen: If you have a large ambient thermal range between day and night you can use thermal mass to even it out, water, bricks, concrete, earth. This can be combined with insulation in various ways. Even night time radiation to clear night skies can be effective. Indians in the desert in America could make ice this way :o
Cheers jaahn
jaahn
Solar Crusader
Solar Crusader
 
Posts: 132
Joined: Sun Apr 25, 2010 8:42 am

Re: Desert farm, Big pump, Batteries?

Postby Warpspeed » Sun May 14, 2017 8:18 am

Evaporative cooling is also a powerful mechanism that works especially well in dry desert heat.
Warpspeed
Solar Crusader
Solar Crusader
 
Posts: 358
Joined: Fri Jan 03, 2014 3:18 pm

Re: Desert farm, Big pump, Batteries?

Postby gfsben » Tue May 16, 2017 2:17 pm

Hi all. Have had a busy few days. A couple of them spent down the farm hooking up some wifi gear. We now have just about farm wide wifi, which should make control and monitoring things much easier. Not to mention communication around the place easy.

Gordon- Dates like many things are best kept at around 4 degrees, but it varies in importance between variety's, with most of them not being that crucial. At the moment we are switching the coolroom off at night and the temp comes back up to 10 degrees in the morning, which has been fine.
This year we sold a couple of pallets of Barhee's in the crunchy 'Khalal' stage (to Qatar). Those defiantly need cold storage. Other ones like Thory and Zahidi can probably last for years in just a cool space in the dark. I'm not sure about why you would want to specifically avoid putting them in the fridge, except that it tends to make the sugars go harder and you loose that super squishy consistency that you get with fresh Medjools.

We love our swampies here but we can justify some cold storage, even some big freezer space would be great. You do get the odd camel wandering past that is just begging to become hamburgers:)

We just had a co-op meetup and the general feel now is that we are leaning towards a new submersible. I wish we had two bores so we could just leave the other pump as is as an EMP/gamma ray burst proof backup;)

I dont really mind what way we go about the solar pump. It seems that one way or another we are going to farm out that responsibility to the installer.
I would like to focus on a really good thermal storage based cooling system that minimises or eliminates any reliance on a battery bank.
I didnt mention it before but we do have an existing off grid system- Old and recycled, it still provides us with power enough for fridges,lighting and computers. It is 24v 1200Ah gells, 1200W Selectornic inverter, two PL60 regs, and a random collection of PV that i have seen producing around 1.2 kW.

So now what i am looking for is a good 5 or 6Kw Chiller that i would plumb up to a couple of thousand litre stainless steel tank. Ideally this would be coupled directly to a further 8kW PV array using the same kind of variable frequency drive that would run the bore pump.

I quite like this http://ecozensolutions.com/innovation/micro-cold-storage but it is optimised for trans-portability, and I think I could do it cheaper and with bigger/longer storage.

Sounds like a plan?
gfsben
Solar Supporter
Solar Supporter
 
Posts: 16
Joined: Sat Dec 20, 2014 5:28 pm

Re: Desert farm, Big pump, Batteries?

Postby Warpspeed » Tue May 16, 2017 2:43 pm

Ice expands considerably when freezing, so take that into consideration when designing your tank.
It will need to be a solid block ice, not just chilled water.
A large free standing ice tank in the middle of your cool room and a single ceiling fan might be all you need.
Your chiller should preferably use a cooling tower rather than a fan coil condenser, it will be more efficient in dry daytime heat.

Keep your eye on the auctions.
Large commercial buildings that have air-conditioning chillers mounted on the roof are being demolished from time to time. You can probably get one for free if you can arrange for removal yourself.
There is no significant market for large second hand chillers and their associated cooling towers, they often go for scrap value.

The cost of removal is often more than the scrap value, so a demolition company may be glad to just see it gone..
Warpspeed
Solar Crusader
Solar Crusader
 
Posts: 358
Joined: Fri Jan 03, 2014 3:18 pm

Re: Desert farm, Big pump, Batteries?

Postby Gordon-Loomberah » Tue May 16, 2017 2:51 pm

gfsben wrote: I'm not sure about why you would want to specifically avoid putting them in the fridge, except that it tends to make the sugars go harder and you loose that super squishy consistency that you get with fresh Medjools.


The grower reckoned they would go mouldy, and some did start going (so we had to quickly eat them all :) ), after only 2 days at room temp, 10-20C. They were Medjools... and extremely delicious!
http://gunagulla.com Loomberah weather and astronomy including live solar radiation intensity and UV + Gunagulla aquaponics, organic eggs and cherries
User avatar
Gordon-Loomberah
Community Moderator
 
Posts: 5401
Joined: Thu Sep 24, 2009 9:41 pm
Location: Loomberah NSW Australia

Re: Desert farm, Big pump, Batteries?

Postby gfsben » Tue May 16, 2017 3:18 pm

So I was thinking of filling the tank with PCM. It could be a commercial product designed to run at sub zero temperatures, which could possibly allow for some frozen storage space.
Alternatively i could just use a whole bunch of one or two litre HDPE containers to hold purified water. Then the remaining volume of the tank and the loop that runs to the chiller could be filled with a glycol-water mix. That would keep the cost of coolant down.
If I just used containers of water as my PCM then my storage temp would be just above zero. I imagine this would mean a larger heat exchange area would be required to keep the main coolroom at around 4 C. It could be an oversized air-handler, or chilled beams, or just fans running from highly insulated room with the tank in it?

Why has this not been done/ or done and well documented on the web? It seems quite doable. And now i search a bit deeper, i am finding a number of commercial offerings that are similar.
gfsben
Solar Supporter
Solar Supporter
 
Posts: 16
Joined: Sat Dec 20, 2014 5:28 pm

Re: Desert farm, Big pump, Batteries?

Postby gfsben » Tue May 16, 2017 3:45 pm

How about this one https://www.machines4u.com.au/view/advert/Industrial-Water-Liquid-Chiller-7-75kW/345174/
If it were possible to hook it up to bore-water on the condenser, or possibly just a big out door water tank as a passive heat loss device, then it could solve the issues of trying to dump heat into 45 degree desert temperatures in the middle of summer.... or it could just be an added complication. Perhaps a air-cooled chiller is simpler?
What do you think about running it from PV using the 10kw version of this https://www.commodoreaustralia.com.au/product/ac-pump-inverter-3000la-run-your-ac-pump-for-free-grid-backup-model-gprs-phone-remote-monitoring-copy/ ?
gfsben
Solar Supporter
Solar Supporter
 
Posts: 16
Joined: Sat Dec 20, 2014 5:28 pm

Re: Desert farm, Big pump, Batteries?

Postby Gordon-Loomberah » Tue May 16, 2017 4:34 pm

gfsben wrote:If I just used containers of water as my PCM then my storage temp would be just above zero.


Use a saturated saline (NaCl) solution and it will be melt at around -20C. That's what I used in 2l bottles for transporting frozen trout for many hours- they stay solid. CaCl2 is another salt which will deliver an even lower MP.
http://gunagulla.com Loomberah weather and astronomy including live solar radiation intensity and UV + Gunagulla aquaponics, organic eggs and cherries
User avatar
Gordon-Loomberah
Community Moderator
 
Posts: 5401
Joined: Thu Sep 24, 2009 9:41 pm
Location: Loomberah NSW Australia

Re: Desert farm, Big pump, Batteries?

Postby Warpspeed » Tue May 16, 2017 4:48 pm

Cooling towers are sometimes less desirable on top of inner city buildings, over spray and Legionnaires disease frighten a few people off, so conventional smaller fan coil units are sometimes preferred.
Out in the open, cooling towers don't have those same problems.

If you have bore water, or a pond of sufficient size with enough surface area for natural evaporation that should certainly work. But warm untreated water will quickly de-aerate, and maybe suffer from rapid growth of various flora and fauna that could then make the water unhealthy and unusable for other purposes.

A cooling tower may still be the best solution, if the wet bulb temperature is suitably low.
The Bureau of Meteorology should be able to help with some annual wet and dry bulb temperatures.
In dry desert conditions it should work wonderfully well, especially as you have plenty of make up water available. It will be a thirsty beast.
Warpspeed
Solar Crusader
Solar Crusader
 
Posts: 358
Joined: Fri Jan 03, 2014 3:18 pm

Re: Desert farm, Big pump, Batteries?

Postby gfsben » Tue May 16, 2017 5:43 pm

I'm sure a cooling tower would work great. The vast majority of the time it is dry here. Sometimes (usually in summer) we can have periods of wet and humidity, but its not the norm.
I'm just thinking its another component to manage. I'd probably want to RO the makeup water because our water is very hard. That's no big problem either, but these extra systems start to add up.
When you look at how Big solar thermal is done now, they seem to be opting for dry cooling even though cooling towers would work well where many of them are.
It might just come down to that thing that seems common now- 'just add some more PV' to make up for increased pressures in the condesor.
gfsben
Solar Supporter
Solar Supporter
 
Posts: 16
Joined: Sat Dec 20, 2014 5:28 pm

PreviousNext

Return to Components, Installation And Performance

Who is online

Users browsing this forum: No registered users and 4 guests

new solar power specials