http://www.aps.com/main/services/bus...ToSave_59.html
can you add more ?
the one who comes with more than 3 tips... gets a meal when he travels in Romania. :rolleyes:
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http://www.aps.com/main/services/bus...ToSave_59.html
can you add more ?
the one who comes with more than 3 tips... gets a meal when he travels in Romania. :rolleyes:
Energy saving is easy. Turn the unit off and no energy is used.:p
I think that you are just win the prize!:DQuote:
Originally Posted by US Iceman
conclusion:
Romania is not such a great travel destination !
In my opinion, good maintenance is the best energy saving.
Operation cost is more than 60% in Life cycle cost, hence focus should be on operation for saving energy as it will recurring.
S**t,
Just missed a good lunch in Romania......;)
I'll just switch on the unit instead....:cool:
The article is largely aimed at Supermarket and similar. Energy opportunities are usually site and operation specific though the easiest way to get management involved is to have them read about it somewhere.
All of the big winners in this area have involved something that a) already existed and b) was really dumb the first day it existed. Many of the opportunities are there when people are not present; especially when you look at the low-load performance of high capacity systems.
As example: years ago, a major cold storage chain found that their lighting was on 24-hours a day. Why? Cause those old fluorescents, at CSW temperatures, took 100 min. to reach full intensity if they ever got there...So they were simply never turned off.
Replacement was: Shatter Proof Mercury Halide lights. 8-min to full intensity with the quick fire, polycarbonate housed ballasts even at low temperature. 168 hours per week of 6-sq ft per watt went down to 50 hours a week at 9 sq ft per watt; and those watts are a load on the refrigeration as well.
Many people are focused only on energy efficient design of refrigeration plant. However, our goal in energy savings is efficient operation.
Assume that we have defrost control and floating head pressure control as mentioned in these tips. How should we set these controls to get maximum energy savings?
Better late than never!
If your defrost can be ran at anytime you can get fewer defrosts by defrosting based on liquid run time rather than defrost clocks. Keeping your head pressure at wetbulb and increasing the pressure to a predetermined defrost point only for defrost time is another saver. The head pressure can be increasing during coil pumpdown. A defrost termination can be used to terminate a defrost before the defrost timer has expired. This is initiated if the coil temp reached a predetermined temperature for some period of time. Say you have a defrost time set for 40 minutes, say after 20 minutes the coil temp is at 60degF, if it stays there for say 10 minutes the defrost can be stopped about 10 minutes early. Demand defrost can also be used where coil and room parameters are monitored to determine if a defrost is needed. After the defrost has ended fans should stir the are for a period of time before making any fan speed or BPR (if aplicable) adjustments.
Lots of other energy ideas:
This first one costs nothing
Reduce system lift (delta between suction and discharge)
Reduce compressor part load operation. Make sure smallest compressor is the one trimming while the larger ones stay loaded. Too many operators have multiple compressors running part loaded much of the time. If you start trimming with the smallest machine you can save alot. (add a VFD to that trim machine and it can run loaded more often also) This saves in a couple of ways first you will be able to have less compressors running. Second once a screw Slide valve goes below 95% the efficiency of the compressors work drops dramatically.
Upgrade as much equipment as you can to latest efficient motors.
Insulate better and add more efficient lighting.
If building a system or retrofiting.
Go with larger sized piping and larger condenser capacity.
Add VFD to condenser and evaporator fans.
Use milti stage compression, liquid subcooling
Have thermosiphon cooling on compressors
reduce/eliminate non-condensibles
Use flexible computer control
1. Liquid run time. What is the setting should be? 4,8,24,48 hours. This is only one variable of rate of frost formation. Humidity in cold room and temperature difference is others.Quote:
Originally Posted by MeanMack
2. Increase pressure for defrost. I prefer don't increase. Large plant with many coils will run on defrost pressure continuously.
3. Reduce system lift. Don't agree. This lift should be optimum. Criteria is total plant power use.
4. Fight compressor partload. Agree.
5. Below 95% efficiency of compressor drop dramatically. Don't agree. Typically efficiency reduction is linear down to 50%. It will reduce exponentially below 50%.
Certainly, we can use many ways to save energy. Just 2 questions. What is the payback? How much energy will be saved? Some measures have long payback, others will save little energy.
1. Liquid run time.Quote:
Originally Posted by Segei
The operator would adjust the hours based on room conditions (RH etc), he would tune his system. So he would answer the questions by trial, how few of defrosts can I get by with. Typically (though not always possible) 1 to 2 defrost a day at most. However some plants can only defrosts at exact times each day and thus liquid time is not a viable option. However any operator can probably lower his defrost times. Typically HG entering the coil returns to the compressor ready to use as a liquid but as the defrost winds down and the coil temp rises the HG returns to the compressor needing to be recompressed placing a significant increase in load.
2. Increase pressure for defrost.
The idea is not to increase pressure during defrost but to allow for a reduction when not in defrost (90-100psi). Granted there are plants where they may not be able to lower their head pressure, however, the vast majority can and most with some kind of computer control do. Generally 12 or 24 hours of liquid time is used.
2. Reduce system Lift
In a, NH3 refrigeration system the efficiency of a compressor increases about 1.5 to 2% per degree of reduction in condensing pressure. This magnitude is dependent on the operating pressure ratio of the compressor. The question is do I want to work a 30 HP condenser fan/pump harder or a 300HP compressor. I think generally the plant savings is in the compressor. Optimally running the highest suction possible and the lowest discharge. Keep that delta down. The number of run hours on some compressors will go down also.
5. Below 95% efficiency of compressor drop dramatically.
The efficiency of "all" industrial compressors degrades as they operate at a fraction of full load capacity. The plotted curve is totally non linear. For example when a SV reaches 10% the power used by the compressor is still well above 50%, virtually no work being done yet large amounts of energy cost incurred. As far as over the range of the SV, at 90% SV the tonnage of a compressor drops to around 80% and the power is way up around 95%. At 75% SV the tonnage is at about 60% and the power is about 85%. At 50% SV the tonnage is at around 35% and the power around 70%. This shows a definite non-linear curve. You can easily check the power by hooking up a KW meter while unloading the SV. So now you know the power and the SV position the unknown is the amount of work the compressor is doing at that point. In the past manufacturers were only concerned about full load rating for compressor design. With the rise in energy awareness part-load has become more prominent. While part-load ratings are presented far less often then full load ratings they are possible. Most manufacturers offer rating software that allows detailed part-load curves to be developed and documented. Just crunch the numbers from the manufacturers curve fit equations and see the results.
What is the payback?
1. Time Savings. Less maintenance (less run hours)
2. Lots of money saved. A lot of money can be had in incentive payback from utilities. The utilities know these things work as their power meters don't lie. Thus they give substantial rebates to companies that implement the above regimes (these are tried, proven and documented) Examples
A) Installation Cost - 410,000
Incentive rebates - 213,500
documented energy savings before/after 58% reduction (1,140,000 kWh/yr) or 51,000 per year in cheap Pacific NW power. Could be 4 times that savings back east.
B) Cost - 241,777
Incentive - 100,000
Energy savings 34%, 1,939,000kWh/yr, 77,700. Again NW rates of around 3-4 cents per kWh.
C) Cost $310,000
Incentive 127,000 plus state tax breaks of up to 108,000,
energy savings 40%, 2,000,000 kWh/yr, 75,500 per year in savings from there on.
There are many more. Typically if an existing plant will make an effort to operate more efficiently they can easily save 25% in energy cost and more likely closer to 50%. Some plants can save money with no expenditures, simply smarter and aggressive control techniques. The problem with most operators is they don't pay the bills. They have no incentive to see to what extremes they can go and still maintain product quality.
Hi, MeanMack.Quote:
Originally Posted by MeanMack
Welcome back.:)
This is some information about hot gas defrosting and about optimized suction pressure.
1. Reduce system lift. Don't take it personally, but this is old simplified approach. Suction pressure up, head pressure down. This is major misconception in energy savings in industrial refrigeration. Look, you have two contradicting staments. Floating condensing pressure save condenser energy. It doesn't save compressor energy. To save compressor energy we have to run all condensers at full capacity. What should we do? I think that head pressure and suction pressure should be optimum to minimize plant energy use. This is an idea of optimization.
2. 95% of capacity. I suggest you to read Doug Reindl(IRC) book "Industrial Refrigerating Energy Efficiency Guidebook" page 6-168. Couple years ago Frick and FES had presentations at IIAR conference and they gave similar information about pert load energy use. Not all industrial compressors have poor part load performance. Reciprocate compressor have good part load efficiency.
3. 40-60% of energy savings sounds like fairytale. It can happen at two scenarios.
- New plant. Somebody done estimation of potential energy use based on false assumptions.
- Existing plant. Somebody started up all compressors, set head pressure to 180psig, defrost to 6 times per day and let it run. I didn't see such plants. Typically 10-20% can be saved.
Attachment 3148
Attachment 3149
Attachment 3150
Attachment 3151
Thanks for the welcome backQuote:
Originally Posted by Segei
1. Reduce system lift.
Things that may keep you from lowering head: Hot Gas Defrost, Heated Zones (40-55 degF rooms), Oil Separators, Hot Gas Unloaders, Flooded system delivery, Liquid injection cooling, Water defrost Tanks, Under floor heating, Etc. All have viable solutions.
Misconseptions: Reducing condensing pressure increases fan/pump power. This is true but compressor energy savings will almost always exceed the increase in condenser power. Wet bulb should always keep this in line.
I think this is your optimization thought. There can be a conflict between increasing suction for compressor savings and keeping a good enough Coil TD so Fan Cycling or VFD control can be effective. This balance is different with each application. It is very sensitive to the ratio between compressor and fan power especially because of the non-linear nature of VFD fan energy savings. The evap fan HP can be low enough that operating the compressors at the highest possible suction and operating the fans at full capacity is most efficient. If dealing with large HP fans the VFD might make fan savings a higher priority than compressor. It gets complicated with different process loads on the same compressor header, here more detailed analysis is the only way to optimize. If a plant has one small -20 room and 12) -10 zones the -20 is dictating the evaporating temp. We may find here the savings may be in dedicating a compressor to the -20 room and letting the rest of the plant run a lower temp off the main compressors. Done this several times. In other words the goal is always the same that is the lowest system energy use. Some systems may not like the higher speed of the refrigerant at higher suctions, current limiting may need to be added, lots of issues may arrise. Generally speaking most plants can run at a higher suction and lower (Floating) discharge.
2. I totally agree that recip compressors have a nice linear power to capacity ratio when unloading but not Screws. Their own numbers show it. Mycom, FES, Vilter and Frick. That's why we put VFD's on Screws and not recips, because of the part load performance (we actually have put a few on recips but for smaller load reasons). We can run a compressor speen down to 40-50% and the power to tonnage in a pretty equal linear slope, not a curve like when you start unloading the Slide Valve.
3. 40-60% of energy savings sounds like fairytale.
I think I said 25 to 50% this most being closer to 50.
I don't think I have ever seen below 25% and you haven't seen above 20. One of us needs to get out more. ;)
BTW all the numbers I supplied here are verified by 3rd party audits through major utilities like Boenneville Power, Pacific Power, Puget Power, Seattle City light. These are extensive verifications that can have several months of data. Like the saying goes the proof is in the pudding.
A) Installation Cost - 148,800
Incentive rebates -
documented energy savings before/after 50+% reduction (722,000 kWh/yr) or 26,900 per year. 5.5 year payback
A) Installation Cost - 225,317
Incentive rebates -
documented energy savings before/after 48% reduction (897,000 kWh/yr) or 32,600 per year in cheap Pacific NW power.
Probably 2/3 of the projects I deal with are retrofit. Those are obviously the only ones you can get before/after numbers on. I think we probably agree on more than we might think we may be loosing a few things in translation. (Except the part-load SV and the 20%) :)
Quote:
Originally Posted by MeanMack
For screws this is true, for recip.'s not so much. You should not categorize all compressors as the same. Now if you said it's a general tendency for all screw compressors to behave this way (some have different variations of what you described) then I would agree.
Another obvious attempt at low defrost pressure is to find the minimum pressure needed for adequate defrosts and then use a dedicated compressor to supply the hot gas for defrosts. That way you only penalize the system power for a much smaller compressor instead of the whole system.;)
1. Reduce system lift.Quote:
Originally Posted by MeanMack
I give one more article to show the difference between minimum condensing pressure and floating cond. pressure. I think that it is clear that this pressure should be floated down to minimum allowable pressure. Today almost everybody float condensing pressures. "We float head pressure" is very popular expression. However, 99% people have little information about this issue. Why to float? How to float? When to float? Head pressure can float itself when wet bulb temperature and/or load change. To save energy, it should be floated at optimum level. What are the benefits of floating? Actually the benefits are not huge. What can we save? I found that good floating can give savings of 15-20% of condenser power because floating saves only condenser power. This is 1-2% of plant power. Not huge savings. How long can we get these savings. Typically in summer all condensers run at full capacity. In winter plants run at minimum allowable pressure(no floating). Spring and fall are seasons to float. Actually I think that lowering minimum allowable head pressure by 5 psig will give savings similar to the floating head pressure.
About suction pressure. I mentioned in my articles that this for single speed evaporator fans. I agree that with evaporator fan VFDs it will be more complicated. However, suction pressure should be optimum based on power use of evaporator fans.
2. Compressor VFDs. These VFDs are expensive. They use additional energy( around 3.5%). Let's compare efficiencies of regular compressor with slide valve and compressor with VFDs. From 100% to 85% regular compressor more efficient because of additional 3.5% for VFD. Efficiencies will be equal around 85%. From 85% to 70% compressor with VFD is more efficient. So if we can run compressor in the range 70-100% efficiencies compressors with and without VFD will be equal. It can be done by choosing the right combination of different compressors. Good designed and good operated refrigeration plant without VFDs have efficiency similar to the plant with VFDs.
3. Percentage of energy savings.
You gave 3 example: 38, 40 58%. This is the range of 40-60%.
You gave 2 additional example with savings around 50%. Can you give us more information about one project? For example. Condensing pressure was lowered from 140psig to 110psig and savings 20%. Defrost changed from...to.... and savings 15%. Suction pressure changed from... to .. and savings 10%............ Total is 50%. It will look more like technical discussion but not sale pitch.
I agree that this is one option. However, it requires capital investment for re-piping.Quote:
Originally Posted by US Iceman
This is the artical.
Attachment 3153
Part load performance of a screw compressor(Frick)
Attachment 3154
[QUOTE=Segei;166356]This is the artical.Hi I am interested in learning more on your aproach to this our plant has installed the hench system and i would like to learn to optimize for our conditions . what type of info do i need to get this accomplished. Thank you Mike. We are a production facility using ammonia and are located in maryland
Mike.
I think that Hench representatives should tell you about optimum wet bulb approach. However, if you want to get more information about this issue, you can go on my website www.skenergy.ca I have 70+ newsletters related to energy savings. You can ask questions at this forum as well.
When not in use. That rule still applies, and in fact this is one of the golden rules for energy efficiency at home. Even as simple as dragging television when not in use, unplug chargers when you’re done with the cargo, and disconnecting all devices not in use. Can you even in standby mode still consumes energy and made a number of devices in standby and connected can still consume a large amount of energy.
To save energy at home, you can use again and again and be able to recycle more to save energy at home. You can also decide that you buy and save energy to turn. You can also find alternatives and, alternative energy, which is much cheaper to find.
Maybe in the United States, but electricity is 5 times more expensive here (the U.S equivalent of $0.50/kWh), so almost all of the life cycle cost of A/C here is electricity. The electric bill is so scary that it makes people scream when they see it. :DQuote:
Originally Posted by Sridhar1312
Some residential tips from my website:
* Set up reflective window tints (such as the quantum type)
* Use a pedestal fan that is at least 16 inches wide and point it at yourself, the small fans are not effective. In order for a fan to be effective it is to be the right size and should be pointed at you, the user.
* Place the pedestal fan in front of the air conditioner, turn the thermostat temperature up to turn the compressor down, and have the fan blow the slightly cooled air on you.
* You can also use the 16 inch pedestal fan anywhere in an air conditioned room to benefit from the cooling effect of a fan + the air conditioned air. Remember, the fan is to be pointed at you. Using it to circulate the air in a room is not nearly as effective.
Two tips I forgot to add: Program the thermostat to turn the unit on briefly (daily) and then back off before you get home from work, but only if you have the tendency to leave the unit on because you don't want to wait for it to cool. This means that you can be cooled as soon as you get home.
* Purchase window blinds that you can close during summer days to block out sunlight (hence some heat), and open during the winter to let in sunlight when you need heat.
Another great way to reduce energy costs and associated carbon emissions is through voltage optimisation. Is this something you guys have heard of before? It essentially lowers the incoming voltage to your premises to more accordingly match the electrical start up of your appliances. Powerstar have helped a number of big named companies reduce their energy consumption through voltage optimization including Australian based cold chain manufacturer SWIRES,and Leed’s based refrigeration service Tdg.
How do you calculate the energy savings? Can you give us example?
Oh this is great! A centralized location for energy saving links! Thanks so much! I am always looking for ways to save money, now I have lots of ideas!