Cost Saving by Load-Shaving

I think the term is peak shaving, which means when the electricity you are purchasing is at premium rate, say in the dead of summer or winter, you would run your gen sets to shave some of the peak rates..

What you must do is calculate the cost of power vs. the cost of diesel to run your gen-sets.. One option may be to schedule your maintenance runs for the time your purchased electricity is at a premium which will limit some costs.

The price of diesel these days probably will exceed purchased power from grid..

As far as load shaving, you must identify loads that are non-critical for your operation, and shed them when not necessary..I do not think your standby machines will need to be in this calculation..

Thanks for all the replies,they really help me alot..I'm already start doing energy audit in this plant and data collection using a data analyser.

From the reply of JMueller ,"Typically air conditioning can be cycled off for 2-5 minutes out of every 20-30 minutes without any significant change in indoor comfort levels, so the cost for doing this is the installation of a simple control (typically utility-supplied)."

Can I know more detail about that include the reference website,case studies and manufacturer of the controller if possible?thanks

Go to your local utility's web site and follow the commercial/industrial link to see what programs they offer. They may even send a rep to help with a casual survey and suggest ideas to investigate.

John M has given some VERY good advice in his note. Gather ALL the data you can about costing and power usage.

as part of the internship, you should then ask your employer to introduce you to someone (probably in accounts) who can then lead you through a "cost benefit" analysis to determine whether any particular strategy is of benefit.

Make sure they calculate the "do nothing different" scenario so that you can compare any future action with what would happen if nothing was done.

Remember for your sake there are two outcomes to this project.

First, the benefit to the company in potential power reduction.

Second is the learning experience for you. This is something that will stay with you forever regardless of the outcome for the company. Enjoy!!

One other question to ask while you're dealing with the accounting folks is to see 24 months of utility bills; electric, gas, fuel, water, sewer, etc. Taske the data and generate a spreadsheet of units billed per month, cost per unit, total monthly cost.

For electricity, your spreadsheet will probably record KWHr used, KW demand, $/KWH, $/KW demand, and total cost. Plot curves for each utility.

What you might see are certain peaks or spikes in monthly usage and/or costs. Find out what causes the peaks, and see if that is a target to go after. In my case, it was a matter of letting operator know that it was better to anticipate which days an 800 HP chiller needed to run and starting it before 8AM to avoid the in-rush starting current from peaking a demand charge during the expensive part of the day. A no cost change in operating procedure that saved several thousand per year in reduced demand costs.

Were those generator sets originally installed to allow critical manufacturing processes to continue through power outages? If so, the cost of running them was probably not the principal consideration when they were purchased. Power from these generator sets may exceed the cost of power from the utility company to a considerable degree.

A setup to measure power consumption throughout your plant could cost quite a bit in time and materials, whether you deploy devices that use a computer interface or something like a strip recorder. You can get a fair idea of the normal usage pattern by scheduling hourly readings of all the watt-hour meters, noting the time of day and ambient temperature. This isn't as precise as making instrument readings of all your circuits, but it will give your bosses an idea of the facility's current hourly power consumption without requiring a large investment in electronics and skilled labor.

You can also review the electric bills for the past year or so to see what the overall pattern of consumption is. These things will give Management a handle on the situation, and it doesn't cost very much.

It is usually Management's job to negotiate electric rates with the power company, and Management will also decide whether using the emergency generators to shave peaks makes sense. If you can quickly provide them with information that enables them to make an intelligent decision, it will be in your favor. This sounds more like a desperate solution than a sensible one, but it isn't my factory. I wish you all well.

Dear Sir,

As you are operating your own system with the help of 4 generator sets, and as a system, all are running in parallel.

For power system operation and control, electrical system frequency plays a vital role.

You have stated that you have to do load shaving i.e. you have to do load shedding for smooth system operation I suppose.

Please monitor closely the system frequency and do load shedding depending upon how you are facing the system frequency problems.

For a small and compact system it is a very very delicate and ardous task of system control and Load Shedding process. Only in case of major grid systems , you can control the system frequency and there , it is a child's play, provided you are absolutely devoted and dedicated to the power system which you are operating and controlling.

Regards,

Ulhas Pradhan

My dear friend

if you are sure the gen sets you have are Standby rated then you may not be able to run the same as peak shaving application please go through the rating definition as per relevant ISO.you can run the sets as you wish at the cost of life of the generator. as stand by application the engine can run about 200Hours in a year with rated load in other words your savings will be zero as the engine will be due for overhaul after 200Hours of running and you would be paying through your nose for the parts replacement

crm

Hope the information given bellow would of use in deciding the application of standby rated gen-set as peak shaving gen-set

Understanding gen set ratings

Rating gen sets for standby, prime or continuous power uses is based on industry and engineering standards. Architectural engineers,contractors and even building owners and maintenance personnel have common questions about gen set rating criteria.

Following are answers to commonly asked questions:

Q. What is the meaning of standby and prime ratings?

A. Standby power ratings for specific gen set models are determined under the following parameters:

· peak cylinder pressure

· exhaust temperature

· smoke level

· turbocharger speed (if applicable)

.

Ratings are based on fuel stop power in accordance with ISO 3046/1, AS 2789, DIN 6271 and BS 5514. The fuel stop is fixed for each engine model/configuration. It represents the maximum safe horsepower the engine model/configuration will be able to produce without exceeding the limits set according to the parameters.

in accordance with ISO 8528 as well as ISO 3046/1, AS 2789, DIN 6271 and BS 5514.

Electric power generation rating guidelines

Rating Standby

Typical load factor 60%

Typical hours/year 100 hours

Typical peak demand 80% of standby rated kW 100% of rating available for,

duration of an emergency outage

Typical application Building service standby Standby Industrial Base load

Enclosure/sheltered environment Rental Pumping Utility

Power module Construction Co generation

Unreliable utility

crm

I believe as an intern you should be able to and must learn this information from your supervisor/mentor. Not only that would develop a stronger relationship w/ them, but also would help you understand how to get information from your co-workers who would be a much better source. Not that any of the posted suggestions/help is wrong or so. However, there would be several cases where your co-workers are your best bet. A little googling to better understand and to have good impression is a good idea, but at the end of the day, go ahead and ask your supervisor. The worst case, he/she may ask you to figure it out yourself. Also, its good way to know how much the company is willing to invest in you. I am not a big fan of institutions that don't take much care of their employees. I am sure you didn't ask for career development advice; however, you said you are an intern

The only thing I can add is that when I was doing this for this location, I did not rely on equipment name plate data. I took an clamp-on amp meter (and a good electrician so I wouldn't get fried in the 480v) and measured "everything" at full load (as close as I could get). With this data, and everything that has been stated above, I was able to come up with savings for optimum start-stop, load shedding, duty cycling, etc.

Hi,

There are two concepts. Please check there shall be four Main Distribution Board fed by separte transformer and each board shall have a separate DG back up. Also, check the DGs may be of different capacity depending upon the load on the MDBs.

Load sharing will come to picture only if all the Loads are distributed to a common Distribution Board. In this case all transformers might have been paralleled and the DGs will be paralleled.

N.Suresh