Energy saving in AC & R units

[chemi-cool]

Energy prices are soaring.

We are asked daily to cut electric bills.

There are a few ways of handling it,

By lowering head pressure, better insulation, water pumps speed control, heat reclaim, etc, etc,

Post your ideas, who knows, we might come with a new invention, 20,000 members can't be wrong all the time

[Andy]

Hello Chemi

my bright idea is VSD compressors.
Then VSD fans
And don't forget VSD pumps

With the best electronic controls money can buy

Kind Regards Andy

[Grizzly]

Hello Chemi

my bright idea is VSD compressors.
Then VSD fans
And don't forget VSD pumps

With the best electronic controls money can buy

Kind Regards Andy

Andy.
Surely what you propose is viable say in AC mode where stable loads can be presumed?
But what about a large system with fluctuating loads.
The bit I am querying is the variable speed pumps.
If only because on some of the systems we look after with bordelo evaps, the variable speed pumps make control difficult.
cheers Steve.

[GXMPLX]

This subject is too broad.

I suppose you want to tackle existing systems.

The problems are:

1. Modifications may cause failure. Even insulating suction line correctly may require adjustment of system components that can lead to failure.
2. Systems were sized for a working operation. Things like improving insulation in buildings reducing thermal load may be ok only on systems that were undersized, but will leave a correctly working system oversized in general.
3. Improving control may be needed in any system adjustment, but introducing new controls may require special considerations, they usually spend more energy all the time and may be needed only for short periods of time.
4. All systems have an expected life and improving an existing system may shorten it’s life though people may think otherwise. Sometimes it’s better to throw away and start with a new more efficient system.
5. Salesmen usually play with this concept and offer huge savings but when considered carefully you end up they offer big savings on systems that were grossly oversized, inadequate, compared to competing obsolete products, and this list is endless so, etc.
6. Heat recovery that is probably where you can save most energy needs so many changes that you really have to re-design it. Besides not everybody will have an use for this heat, or not all the time and you need to interact with other systems.

So I’d say not everything that shines is gold, it needs careful consideration.

Some systems may be better left alone, other may be better thrown before their expected life, some are worth whacking, like me!

P.D. Exactly my point TKS Andy for reminding me: not all VSD are worth the trouble, some systems end up spending more energy, there is a higher fire hazard, but I agree that just a few may need and perform better with a VSD.

Too much vendor literature!

[Peter_1]

Biggest savings: increasing LP and decreasing HP.

[GXMPLX]

Biggest savings: increasing LP and decreasing HP.

As a poem sounds about right!

You do realize that increasing LP makes HP go higher right?

Well Peter_1 thanks because you let me give an example I’ve posted elsewhere about absolute remarks out of context, like this.

You are right only if the system was not working properly or was oversized.

There are some applications where this formula does not work like systems that must be kept under a certain size for example aboard ships. If you make LP go higher you won’t be able to meet demand because you will decrease heat transmission to the evaporator reducing DT.

If by making LP go higher you increase the cooling time of the load then your energy bill will go up not down!

You see I agree with you it is usually so, but not all systems are the same and you cannot consider one component only!

[Sergei]

Many people don't realise that a lot of energy in industrial refrigeration can be saved by optimizing operation of existing plant. Minimum investment and a lot of energy savings.
How to save?
1. Optimum head pressure. Operate plant as close as possible to the optimum head pressure and total(compressors and condensers) energy use will be minimal.
2. Suction pressure should be optimum as well. Don't forget that higher suction pressure will save energy for compressors, but energy use for evaporators will increase. At optimum suction pressure total power use is minimal.
3. Optimal frequency of defrosting. Don't defrost coil if it doesn't have a frost.

[coolments]

Hi all, one of the biggest savings to be made in ac i think is educating the user to get rid of the "im hot so i will turn the stat as low as it will go, now i am cold so i will turn it up as high as it will go, lets mess with the stat all day syndrome", some aplications have central controllers you can set to prevent this but sadly most dont.

Also my big idea for increased energy saving on inverters would be for ac units to have a humidity sensor installed along side the temp stat so it will work out saturation point of water at that moment in time and try to cool the room by having the the evapourator temp slighty above this point so mainly concentrating on removing sensible heat and not latent, unless it has to ramp up to acheive temp or humidity is too high, this would reduce the drying out of the air which so many people complain about and also reduce condensate issues due to lower pump use. maybe it would work maybe not?

[GXMPLX]

I like centralized systems but I'm affraid that since adaptive centralized control exists, the best way to save energy is to use distributed systems with compressor evaporator condenser distances as short as possible.

[US Iceman]

Hi Chemi.

The biggest energy savings is by reducing the discharge pressure (but you already know that). The main issue to do this is based on the heat sink used for cooling the condenser.

Of course if air is used then the ambient air + the condenser design TD determines the design condensing temperature.

Depending on you exact location water cooled might be acceptable if you use a cooling tower or evaporative condenser (small ones do exist). These are driven by we bulb temperatures, which are usually lower than the dry bulb temperatures.

I'll offer something possibly new... How low does your ground temperature get in the summer, or how low would you have to drill a hole to get relatively lower temperatures? You might be able to use a bore hole heat exchanger similar to those used geothermal heat pump systems.

[WINJA]

switch off all heating , give all staff a free jacket,
then for sumer , singlets for everyone

[GXMPLX]

switch off all heating , give all staff a free jacket,

coolments already mentioned this it´s called demand control.

then for sumer , singlets for everyone

I don´t see how this could help it would add the energy used by them, plus thermal load to the system.

To give each a personal water spray, (remember to use none ozone depleting propellants) would also add latent load.

Have any serious study on their use?

[SteinarN]

I'll offer something possibly new... How low does your ground temperature get in the summer, or how low would you have to drill a hole to get relatively lower temperatures? You might be able to use a bore hole heat exchanger similar to those used geothermal heat pump systems.

This solution has been utilized in some large new buildings AC/heating system here in Norway. Such a system may consist of say 50 to 200 holes, each 100 to 160 meters deep. A heat pump is extracting the heat from the anti freeze in the closed loop system in the winter. The ground cools down to a lower temperature than before. The cooling in summer can be done to a large extent by a heat exchanger between the ground loop and the AC water system or alternatively the anti freeze can be feed directly into the AC system.

The temperature in the ground may in the end get so high it is necessary to run the heat pump in reverse to cool down the AC system.

Such a system offers a huge reduction in the energy consumption both for heating as well as for cooling. The upfront cost is however large.

[US Iceman]

This solution has been utilized in some large new buildings AC/heating system here in Norway.

I've read some articles on this and they are really interesting.

The results in Israel may be different because of the location. It would take some investigation to determine the soil temperatures and any possible gound water movement to see if this is a viable alternative for Chemi to use.

[chemi-cool]

We had once a company that used to bury the condenser and compressor under ground.

Never heard afterwards what happened with it.

Our soil is acidic so pipes have to be coated, the whole process is very expensive and I doubt it worth the effort.
Don't forget that you have to check the soil heat conductivity before [ how exactly it done, I have no idea].

[GXMPLX]

We had once a company that used to bury the condenser and compressor under ground.

Never heard afterwards what happened with it.

Our soil is acidic so pipes have to be coated, the whole process is very expensive and I doubt it worth the effort.
Don't forget that you have to check the soil heat conductivity before [ how exactly it done, I have no idea].

Interfering with underground water would not be good in dessert areas.

Also here the soil temperature at 160m would be much higher, possibly even higher than ambient, we have several volcanoes in less than 100km.

And we have lots of seismic activity so it's not just ground quality but activity!

[star882]

If it's not already there, a reflective coating on the roof. A surprisingly simple idea that can save a lot.

Window tint - very cheap to install and should quickly pay for itself.

Turn up the thermostats by a few degrees and use fans to take advantage of the wind chill effect.

Use evaporative coolers (indirect types that do not increase humidity are also available) when weather permits. Evaporative condensers are also available.

Add more insulation.

Use more efficient lighting. (Reduces heat load.)

[ptkambdg]

Dear Member...
Suggest we can change the perseption of the customer about cold.. if they think to have cold they should set the thermostat to 20 degree Celcius, why don't they set it to be 23 or 25 deg Celcius

[Tesla]

Hi Guys
I've been into this for many years and the key word is LOAD MATCHING using close control, then minimise waste like floating setpoint to incorperate OATemp conditions ie on a hot day increase setpoint. Also utilise waste heat from exchangers and reuse condensate... These scientists and designers have got thier head so far ..(in the sand) it's not funny - they told me there were only 3 states of matter in school now there's 5.

[roman19]

hey guys,
vapour absorption air conditioning can lead to substantial energy saving by utilising waste heat. The initial cost is higher than the vapour compression system but the long term benefits are better.

[salmanprince08]

hello sir,

how is calculate chiller, any formula, and how many ton available in the market,

so please reply me, i dont understand chiller calculation please help me.

i know ahu and fcu, i am calculation A/C ton and supply duct, all calculation but how is calculate chiller pipe.

i am confused.

please reply....

[dr_ace_2008]

i think the best suggestion to saving the energy is set the sleep program everyday
if we cant do it
we start ac on maximum load condition only
maybe in indonesia at 10 AM to 3 PM

thanks