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ecclesk
21-03-2007, 10:56 AM
Our company are in talks with these guys, have a look at the link. (never posted a link before so i'm not sure if it wil work)

[URL="http://cost-cutting-cube.com/home___news"]

they are planning to run a trial at one of our coldstores,
What do you think?

from looking at the website all thier trials so far have been carried out on smal plant, comercial systems, hotels, etc, etc. nothing like the size of our systems.

Also our company policy for plant operation is:

DO NOT operate on stats!
stats set to un-obtainable temp, run plant flat out from 00:00 till 07:00 (maximising the cheap night rate usage)

then

Shut down plant untill store reaches -18 then (normaly 3-6 hrs)

then

run plant flat out and have a second shut down at say 20:00 till 00:00.

We have run numerous trials trying many diferent philosophies, and all have proven that our current method is the most efficient way of operating for the type of bulk storage coldstores we operate.

i have seen probes installed in glycol pots before and i assume this ecube device would have the same sort of effect.

i know these may allow us to have longer shut downs but we would also have to run for longer to recover from the shut down.

any thought or ideas on this would be greatly appriciated:D . has anyone used similar devices on an industrial size coldstore before.

mreischer
18-05-2010, 04:04 PM
Hi,
I was wondering if you have tested the ecube in your larger facility yet? I have seen lots of results from smaller ones (restaurants/liquor stores) and would like to know if the device works on larger places as well.
Thank you.
Matt Reischer

Segei
18-05-2010, 08:21 PM
Hi,
I was wondering if you have tested the ecube in your larger facility yet? I have seen lots of results from smaller ones (restaurants/liquor stores) and would like to know if the device works on larger places as well.
Thank you.
Matt Reischer
What kind of result did you see? Positive or negative. How does it save energy?

Segei
19-06-2010, 03:57 PM
No answer from energy "consultant".
I think that these people look at wrong place for energy savings. Not too much you can save on suction side. Real energy savings can be achieved by improving condensing pressure, defrost. VFDs can be useful for part load operation of condensers, evaporators, screw compressors. However, VFDs are useless at full load.

Grizzly
19-06-2010, 05:18 PM
Load shedding is the real money saver
when dealing with Cold Stores!
Grizzly

Segei
19-06-2010, 05:25 PM
Load shedding is the real money saver
when dealing with Cold Stores!
Grizzly
Load shedding will save money but no energy savings.

Grizzly
19-06-2010, 06:36 PM
What we used to do was.
Run the plant to a lower set point, say-24 overnight when the tariffs are low. Plus unless a 24hr operation there is no movement in and out of the chambers.
Therefore no extra heat load added.
From say 0700 hrs through the day.
The plant was ran to say -18c and in some cases there was no need to run the plant at all during the daytime.
When the electricity tariffs are highest.
So OK you can argue your point and strictly speaking you may be correct.
But to me the energy saved by clever use of the plant loading.
Is an energy saving surely.
Yes there is a lot of money to be saved. But surely that is because we are using less energy. Or at worse using the energy more wisely?
Or as I think you mean we use the same energy just at different times!
Grizzly

Tesla
20-06-2010, 02:01 AM
Interesting thoughts here. The proof is in the pudding for energy savings on refrigeration systems. The proven methods are 1, decrease condensing pressure - 2, increase suction pressure - 3, reduce load (defrost control/service load) - 4, use power at the cheapest times and reduce the monthly peak 1/2kWh (if applicable). Even at full load VSD control is useful in lengthening the life of machinery by reducing the stress on bearings. I checked the above link - but it is a site full of links, which one should I follow?

Segei
20-06-2010, 05:01 AM
What we used to do was.
Run the plant to a lower set point, say-24 overnight when the tariffs are low. Plus unless a 24hr operation there is no movement in and out of the chambers.
Therefore no extra heat load added.
From say 0700 hrs through the day.
The plant was ran to say -18c and in some cases there was no need to run the plant at all during the daytime.
When the electricity tariffs are highest.
So OK you can argue your point and strictly speaking you may be correct.
But to me the energy saved by clever use of the plant loading.
Is an energy saving surely.
Yes there is a lot of money to be saved. But surely that is because we are using less energy. Or at worse using the energy more wisely?
Or as I think you mean we use the same energy just at different times!
Grizzly
I think that using energy wisely we should use all energy(money) saving measures. Load shifting just one of them but it is not good for every plant. Some plant have flat energy rate, other plants have small difference between pick and off peak energy rates. However, optimum condensing pressure, optimum suction pressure and optimum defrosting is beneficial for every plant.

Segei
20-06-2010, 05:11 AM
Interesting thoughts here. The proof is in the pudding for energy savings on refrigeration systems. The proven methods are 1, decrease condensing pressure - 2, increase suction pressure - 3, reduce load (defrost control/service load) - 4, use power at the cheapest times and reduce the monthly peak 1/2kWh (if applicable). Even at full load VSD control is useful in lengthening the life of machinery by reducing the stress on bearings. I checked the above link - but it is a site full of links, which one should I follow?
I agree that energy savings is very interesting and complicated issue.
About proven methods. 1,2 are always right for compressors, but are not always right for the plant. I didn't get about monthly peak 1/2 KWh and bearings? Recently, I heard that VFDs spikes can damage the motor bearings.

Grizzly
20-06-2010, 08:34 AM
;)No-one has mentioned Power Factor Correction for motors.;)
Yet!
Grizzly

Tesla
20-06-2010, 10:23 AM
I agree that energy savings is very interesting and complicated issue.
About proven methods. 1,2 are always right for compressors, but are not always right for the plant. I didn't get about monthly peak 1/2 KWh and bearings? Recently, I heard that VFDs spikes can damage the motor bearings.

In many places the energy supplier charges the customer on the highest kWh during any 30 minute period of the month, so in this case you would be charged the same if you had the plant shut down for 27 days and only ran the plant for 30 minutes as you would if you ran the plant all month. There is usually peak (spike) in power consumption for say a commercial building when the AC starts in the morning and another in mid afternoon when the load is higher. These charges are to pay for the maximum size of power cable required to transmit the electricity from the power station to cover the I2R losses. Power factor increases the I2R losses for inductive loads so there is a penalty charge for that too. Some large power consumers use power factor correction (big capacitors) to minimise the penalties.
Quality VSD's like Danfoss correctly installed and commissioned have good protection from spikes and bearing damage.
Compressors are usually the largest power consumers and their efficiency is very important. I have seen chiller COP as high as 18 in Sydney using the Turbo Cor.
In Aus NABERs will become regulation in August forcing most buildings to list energy ratings. There are new products like Building IQ which can override control systems to ensure maximum efficiencies using live weather data for load matching and much much more. Energy efficiency is my favorite subject and career.

Segei
20-06-2010, 10:32 PM
In many places the energy supplier charges the customer on the highest kWh during any 30 minute period of the month, so in this case you would be charged the same if you had the plant shut down for 27 days and only ran the plant for 30 minutes as you would if you ran the plant all month. There is usually peak (spike) in power consumption for say a commercial building when the AC starts in the morning and another in mid afternoon when the load is higher. These charges are to pay for the maximum size of power cable required to transmit the electricity from the power station to cover the I2R losses. Power factor increases the I2R losses for inductive loads so there is a penalty charge for that too. Some large power consumers use power factor correction (big capacitors) to minimise the penalties.
Quality VSD's like Danfoss correctly installed and commissioned have good protection from spikes and bearing damage.
Compressors are usually the largest power consumers and their efficiency is very important. I have seen chiller COP as high as 18 in Sydney using the Turbo Cor.
In Aus NABERs will become regulation in August forcing most buildings to list energy ratings. There are new products like Building IQ which can override control systems to ensure maximum efficiencies using live weather data for load matching and much much more. Energy efficiency is my favorite subject and career.
How does VSD at full load reduce stress on bearings? Screw comopressor VSD use 3-3.5% of additional energy. At 100% load compressor with VSD is less efficient than compressor without VSD.
Different energy suppliers charge for energy differently. When we shift the load for cold storage, we increase demand charges and refrigeration load will increase as well. However, we will save on cheap energy. As far as I remember, one research was done in Industrial Refrigeration Consortium. They determine that on peak energy should be at least 2.2 times more expensive to justify full load shifting.
COP 18 tell me nothing, because COP depends of the cycle. Can you get COP 18 for cold storage?
Compressor definitely the major energy consumer, but we pay for energy use of whole plant not only compressor. So condensing pressure, suction pressure, defrost should be optimized to minimize energy use of whole refrigeration plant.

Segei
21-06-2010, 12:08 AM
To prove my statements.
Floating condensing pressure(not minimum cond. pressure)

Tesla
21-06-2010, 01:46 AM
Hi Segei
The VSD reduces stress by taking around 30 seconds to start and or stop a compressor, fan or pump instead of upto around 6 seconds for a large motor. Yes at full load the VSD driven motor defiantly uses more power. Yes load shifting will save on power costs from cheaper tariffs also loading and unloading of product at lower tariff rate times. I saw a documentary where in the USA they are starting to use solar PV panels for super markets saving around 15% over a 10 year period.
They are working on prototypes for electromagnetic bearing compressors for the lo temp range - so in the near future we will see COPs of 18. Yes we at the end of the day need to look at the plant on a wholeistic approach over the life cycle of machinery to get the biggest savings on energy.

Segei
21-06-2010, 03:11 AM
Hi Segei
The VSD reduces stress by taking around 30 seconds to start and or stop a compressor, fan or pump instead of upto around 6 seconds for a large motor. Yes at full load the VSD driven motor defiantly uses more power. Yes load shifting will save on power costs from cheaper tariffs also loading and unloading of product at lower tariff rate times. I saw a documentary where in the USA they are starting to use solar PV panels for super markets saving around 15% over a 10 year period.
They are working on prototypes for electromagnetic bearing compressors for the lo temp range - so in the near future we will see COPs of 18. Yes we at the end of the day need to look at the plant on a wholeistic approach over the life cycle of machinery to get the biggest savings on energy.
Hi, Tesla.
I don't see the benefits to start compressor within 30 sec instead of 6 sec. Large motor(compressor) should not start often, because this is not home fridge. My experience have shown that mechanical seal will fail first, because of start and stop of the compressor. Electrical motor bearings can work with soft starter 50,000 Hrs or longer. A refrigeration plant should be set up properly to minimize starts and stops of the compressors.
As I mention COP depends of the cycle. Assume that refrigeration capacity is 100 KW. Compressor energy is 20 KW. COP is 100/20 = 5 What can we improve? Compressor energy. However, 19 KW is work to compress the refrigerant and 1 KW(5%) compressor friction. You can improve 1 KW(if you can), but not too much you will get. So COP depends of cycle.
About solar panel. They have 10 years payback or longer. VFDs have 2-3 years payback with generous government or/and utility incentives. Optimization of refrigeration plant operation has 2-3 months payback(no incentives). You invested $100 to save energy. After 1 year solar panel will give you $10, VFDs will give you $40, optimization will give you $400. What investment do you prefer?

desA
21-06-2010, 03:35 AM
Good reply, Segei.

Achieved COP is indeed mainly a function of the refrigeration cycle itself. There are a number of additional technologies that can be used to increase the isentropic efficiency of the compressor - leading to direct COP improvement.

mad fridgie
21-06-2010, 04:20 AM
Energy saving made simple
1; Minimise Load
2; Reduce compression ratio
3; Reduce transport losses (heat and pressure)
4;optomize aux equipment, run time and performance (fans, pumps electronics etc)
If you have have not achieved maximum of all of the above then you still have a way to go.

desA
21-06-2010, 05:13 AM
Good points, mf.

Has anyone come across technology which improves the compressor's isentropic efficiency?

Segei
21-06-2010, 10:36 PM
Good reply, Segei.

Achieved COP is indeed mainly a function of the refrigeration cycle itself. There are a number of additional technologies that can be used to increase the isentropic efficiency of the compressor - leading to direct COP improvement.
Thanks, desA.
Definitely this opportunity exists. Recently, Mycom presented new type "J" of screw compressor.They claim that it is 15% more efficient than previous type. However, it took them almost 20 years to design new one. This is a lot of investment.

Segei
21-06-2010, 10:58 PM
Energy saving made simple
1; Minimise Load
2; Reduce compression ratio
3; Reduce transport losses (heat and pressure)
4;optomize aux equipment, run time and performance (fans, pumps electronics etc)
If you have have not achieved maximum of all of the above then you still have a way to go.
I agree with 1. Only question is How can we do that? Increased insulation, fast acting doors, modify lightning... What is the payback for these improvement? Not so often you can get acceptable 2 years.
#2 and 4 contradict each other. Reduce compression ratio means minimum condensing pressure and maximum suction pressure. To achieve that, aux(pumps, fans..) should be operated at full capacity. Condensing pressure should be optimum(not minimum) and suction pressure should be optimum as well.
I didn't get about transport losses.

mad fridgie
22-06-2010, 12:01 AM
I agree with 1. Only question is How can we do that? Increased insulation, fast acting doors, modify lightning... What is the payback for these improvement? Not so often you can get acceptable 2 years.
#2 and 4 contradict each other. Reduce compression ratio means minimum condensing pressure and maximum suction pressure. To achieve that, aux(pumps, fans..) should be operated at full capacity. Condensing pressure should be optimum(not minimum) and suction pressure should be optimum as well.
I didn't get about transport losses.
These rules apply to all refrigeration including AC
So looking at load reduction, i gree with your methods, but what about using shading to remove solar gain, or wetted surface to reduced TD across insulation.
Compression ratio we can agree on principle (I think), this normally is limited to the compressor limits. What is required is exansion devices that are able to control to the min and max of the compressor and system limits.
Re the aux, are you using fans and pumps that are at the optimum on the perfromance curves, are these driven high efficient moters, do they turn off or down when load/compressor limits reduces/reached.
Transport losses, relates to non useful heat gain (poorly insulated suction lines) and excessive pressure drops in refrigeration and fluid lines.
For example we have a water flow of 'X', ideally we need a 2" pipe, but we know if we up the pump pressure a bit we can fit a 1 1/2" line. This is done all of the time, quite good reductions installation cost (pipe, labour, valves insulation) poor for efficiency.
Then we come to payback, this is where all the best engineering the world falls over. At what point is advances to high. This depends upon the client, if a goverment dept, then then they should be seen to being the right thing (long payback are acceptable)
Commercial clients need to ensure a return to their sharholders, again this depends upon the type of business and how they precieve their long term business models. For example in NZ agri business in the main stay, but is quite fickle (produce price go up and down a lot) so most need devices that have shport term paybacks. Verses say a building which may have a constant return over 20 years.
Domestic refrigeration (including AC) which is a massive industry, should be improved by means of minimum performance regualtion.

Segei
22-06-2010, 01:41 AM
These rules apply to all refrigeration including AC
So looking at load reduction, i gree with your methods, but what about using shading to remove solar gain, or wetted surface to reduced TD across insulation.
Compression ratio we can agree on principle (I think), this normally is limited to the compressor limits. What is required is exansion devices that are able to control to the min and max of the compressor and system limits.
Re the aux, are you using fans and pumps that are at the optimum on the perfromance curves, are these driven high efficient moters, do they turn off or down when load/compressor limits reduces/reached.
Transport losses, relates to non useful heat gain (poorly insulated suction lines) and excessive pressure drops in refrigeration and fluid lines.
For example we have a water flow of 'X', ideally we need a 2" pipe, but we know if we up the pump pressure a bit we can fit a 1 1/2" line. This is done all of the time, quite good reductions installation cost (pipe, labour, valves insulation) poor for efficiency.
Then we come to payback, this is where all the best engineering the world falls over. At what point is advances to high. This depends upon the client, if a goverment dept, then then they should be seen to being the right thing (long payback are acceptable)
Commercial clients need to ensure a return to their sharholders, again this depends upon the type of business and how they precieve their long term business models. For example in NZ agri business in the main stay, but is quite fickle (produce price go up and down a lot) so most need devices that have shport term paybacks. Verses say a building which may have a constant return over 20 years.
Domestic refrigeration (including AC) which is a massive industry, should be improved by means of minimum performance regualtion.
Remove solar gain and wetted surface these are from theoretical area. It is difficult and expensive to implement in real life.
About compression ratio. Problem is not compressor limits or TEV limits. Condensing pressure should be optimum. It means that total power Compressors+Condensers(pump, fans) are minimum. This is criterion of optimization. This is system approach. For evaporative condensers it is based on wet bulb temperature. During period of cool weather wet bulb tem. will be low and optimum cond. pressure will be low as well. At this time we have to look at the barriers to run the plant at low condensing pressure. There barriers are hot gas defrost, TEVs, liquid injection oil cooling, oil carry-over, space heating..... However, every barrier has a solution. During the winter many ammonia industrial refrigeration plants can operate at condensing pressure below 100 psig.
In North America in industrial refrigeration payback should be 2 years.

mad fridgie
22-06-2010, 02:15 AM
Remove solar gain and wetted surface these are from theoretical area. It is difficult and expensive to implement in real life.
About compression ratio. Problem is not compressor limits or TEV limits. Condensing pressure should be optimum. It means that total power Compressors+Condensers(pump, fans) are minimum. This is criterion of optimization. This is system approach. For evaporative condensers it is based on wet bulb temperature. During period of cool weather wet bulb tem. will be low and optimum cond. pressure will be low as well. At this time we have to look at the barriers to run the plant at low condensing pressure. There barriers are hot gas defrost, TEVs, liquid injection oil cooling, oil carry-over, space heating..... However, every barrier has a solution. During the winter many ammonia industrial refrigeration plants can operate at condensing pressure below 100 psig.
In North America in industrial refrigeration payback should be 2 years.
I perhaps should of said the first critiria is that the refrigeration process does the job is was designed to do.
Most compressor have compression limits upper and lower, maximum efficiency is generally gained at these minimum limits, so this could be called optimum or goal.
How this is achieved is very much plant specific. if you use heat recovery for space heating, then if the heat of elevated rejection is more efficient than another heating source then the system will be at optimum. even though the cooling side is not at optimum.
Re solar and wetted areas, this is not theoretical and can be very cheap, simple shade cloths (solar) and irrigation systems on roofs (a few hundred dollars does a lot of surface area) you could use you bleed from your evap cooling towers as the water source.
I have seen hugh drops in temperature between the roofs and coolstore structures as much as 25C

Segei
22-06-2010, 02:38 AM
I perhaps should of said the first critiria is that the refrigeration process does the job is was designed to do.
Most compressor have compression limits upper and lower, maximum efficiency is generally gained at these minimum limits, so this could be called optimum or goal.
How this is achieved is very much plant specific. if you use heat recovery for space heating, then if the heat of elevated rejection is more efficient than another heating source then the system will be at optimum. even though the cooling side is not at optimum.
Re solar and wetted areas, this is not theoretical and can be very cheap, simple shade cloths (solar) and irrigation systems on roofs (a few hundred dollars does a lot of surface area) you could use you bleed from your evap cooling towers as the water source.
I have seen hugh drops in temperature between the roofs and coolstore structures as much as 25C
You still look at the compressor. Did you read my newsletter? Definitely compressor use less energy at 119 psig than at 125 psig, but 125 psig is optimum, because system energy use is minimum. You can read additional newsletters about optimum suction pressure and optimum condensing pressure in the thread of this forum "energy saving tips".

mad fridgie
22-06-2010, 03:08 AM
You still look at the compressor. Did you read my newsletter? Definitely compressor use less energy at 119 psig than at 125 psig, but 125 psig is optimum, because system energy use is minimum. You can read additional newsletters about optimum suction pressure and optimum condensing pressure in the thread of this forum "energy saving tips".
Sorry Segei, I did not read your report, I have now!
I can see how you have come to your opinion.
Without sounding critical, what you have not calculated into your calculations is the nett increase in refrigeration effect, without knowing all your systems details this could be upto 20% between step 1 and 6.
If its a LT system lets say a COP of 2, then this equates to a further 10% reduction in power (across the board)

Segei
22-06-2010, 03:37 AM
Sorry Segei, I did not read your report, I have now!
I can see how you have come to your opinion.
Without sounding critical, what you have not calculated into your calculations is the nett increase in refrigeration effect, without knowing all your systems details this could be upto 20% between step 1 and 6.
If its a LT system lets say a COP of 2, then this equates to a further 10% reduction in power (across the board)
I've done this estimation for Frick screw compressor. Just double checked Frick numbers. Refrigeration effect difference(120 psig and 150 psig) is 1% for compressor with economizer and 3% without(this is not typical for industrial refrigeration). Suction pressure 3.6 psig(-20F) is typical for cold storages.

mad fridgie
22-06-2010, 03:54 AM
I've done this estimation for Frick screw compressor. Just double checked Frick numbers. Refrigeration effect difference(120 psig and 150 psig) is 1% for compressor with economizer and 3% without(this is not typical for industrial refrigeration). Suction pressure 3.6 psig(-20F) is typical for cold storages.
Do not have Frick data, but other compressors, my calcs come out to be 17% increase in evap refrigeration effect. But I am not one to argue with frick. (non economized)

mad fridgie
22-06-2010, 05:08 AM
Hey Segei,
can you post copies of your Frick calculations at 120 and 150 PSIG
cheers
Mad

desA
22-06-2010, 01:50 PM
Originally Posted by desA
Good reply, Segei.

Achieved COP is indeed mainly a function of the refrigeration cycle itself. There are a number of additional technologies that can be used to increase the isentropic efficiency of the compressor - leading to direct COP improvement.

Segei wrote:
Thanks, desA.
Definitely this opportunity exists. Recently, Mycom presented new type "J" of screw compressor.They claim that it is 15% more efficient than previous type. However, it took them almost 20 years to design new one. This is a lot of investment.

I'd be interested in understanding how they managed to increase compressor isentropic efficiency. These kinds of gains would be very useful for the heat-pump industry.

There are a few theoretically simple ways to push the compressor line on either the log(p)-h, or T-s diagrams, into an almost vertical position, or even leftward leaning. I have not seen this done in practice, however. The gains in isentropic efficiency would be incredible.

Segei
23-06-2010, 02:37 AM
Hey Segei,
can you post copies of your Frick calculations at 120 and 150 PSIG
cheers
Mad
I'll try to post it later.
This is additional information.

Segei
25-06-2010, 01:22 AM
Mad.
I scanned Frick data, but can not upload the file. Probably, it is too big. Send me your e-mail and I'll send you back Frick numbers.

Sergei

Segei
26-06-2010, 03:36 AM
;)No-one has mentioned Power Factor Correction for motors.;)
Yet!
Grizzly
Ten years ago one operator mentioned that they invited electrical engineer to save energy for the refrigeration plant. This was surprise for me, because I believed that majority energy savings should be done by refrigeration engineers. That day was starting point of my research in energy efficiency of the industrial refrigeration.
What did I find? For many years major effort was given to the design of the refrigeration plants. Little attention was given to the operation. However, I believe that efficient operation of the refrigeration plant is major energy saving opportunity. Unfortunately, many operators believe that they have "good" operation of their refrigerating plants.There are significant difference between "good" and energy efficient operation. Recently, several PhD and master degree papers were written in US universities, but they only touched the surface of energy efficiency in industrial refrigeration, because it is complicated issue.Sometimes people saved 10% of energy use and they claim that it was easy. In energy saving process it is easy to save first 10%, it is not easy to save next 10% and it is hard to save last 10%. Every step is harder and harder. I believe that optimization of a refrigeration plant operation is the best way to save energy.

buddy
21-12-2010, 02:14 AM
Our company are in talks with these guys, have a look at the link. (never posted a link before so i'm not sure if it wil work)

[URL="http://cost-cutting-cube.com/home___news"]

they are planning to run a trial at one of our coldstores,
What do you think?

from looking at the website all thier trials so far have been carried out on smal plant, comercial systems, hotels, etc, etc. nothing like the size of our systems.

Also our company policy for plant operation is:

DO NOT operate on stats!
stats set to un-obtainable temp, run plant flat out from 00:00 till 07:00 (maximising the cheap night rate usage)

then

Shut down plant untill store reaches -18 then (normaly 3-6 hrs)

then

run plant flat out and have a second shut down at say 20:00 till 00:00.

We have run numerous trials trying many diferent philosophies, and all have proven that our current method is the most efficient way of operating for the type of bulk storage coldstores we operate.

i have seen probes installed in glycol pots before and i assume this ecube device would have the same sort of effect.

i know these may allow us to have longer shut downs but we would also have to run for longer to recover from the shut down.

any thought or ideas on this would be greatly appriciated:D . has anyone used similar devices on an industrial size coldstore before.

Dear ecclesk,

I would be interested to know the results of the ecube trial.

Any favourable results?

best regards