Shadow Metering

[markiec]

We're considering performing power factor correction at some of our motors and want to be able to verify the I2R loss savings in the distribution system and the savings from lowering the kVAR effects that flow through our electric tariff. (Not seeking any advice here. I'm very comfortable with the concept and options.)

My question is, someone suggested Shadow Metering to verify the savings. I had built spreadsheets that correlate our bills to various variables and was going to monitor those variables against our bill. Any practical thoughts on how to perform meaningful verification of savings without putting chart recorders everywhere? Is Shadow Metering a possibility? Thanks to anyone with experience in this area.

 

[busbar]

 
The advantage of having metering under your control is being able to configure and read at far closer intervals and with more functions than a utility typically uses, and fit with communications that automate the process. A disadvantage is expectation of exact replication utility-billing quantities.

If the installation is on the North American continent, consider obtaining applicable ANSI C12 standards, and reading, understanding, designing and specifying the system to those standards. Prior to purchase-order release, request and review potential vendors independent test reports of products’ adherence to applicable standards.

 

[markiec]

Thanks for the feedback you provide some valuable information. However, if I understand you correctly all shadow metering would allow me to do is replicate utility metering in greater detail. My challenge is to "meter" two sets of conditions to verify that a project is truly saving us money. If we go forward with a number of efficiency steps, including power factor correction at loads, we will know from our utility bills what our "new" energy/demand and bills are. What I'm trying to verify is what would our load have been without those steps. Right now all I can think of is to capture baseline conditions before the improvements and monitor changes there vs. changes in our bills following the improvement steps. That is part art, part science. I'm trying to find out if there's a practical way to meter, after a project is implemented, what our load would have been if the improvements hadn't been made.

 

[jghrist]

The kvar reductions and I²R savings can be calculated at any metered load. This will give you a more accurate measure of your savings. Your load will not be the same as before the project was implemented because equipment run times and loads will not be exactly the same as before.

 

[rbulsara]

as you mentioned realistic way is to have a baseline with all possible details noted, specailly the load (amps), voltage, and pf under various conditions and also mapped to some measurable output (production if its a manufacturing facility). If a commercial facility like office space then note occupancy etc. Your bills should reflect accurate change.

I know you did not seek advise on this, but any significant savings will be from reduction in demand charges (kVA reduction) if you are paying demand charges and savings in pf penalty is you are paying it. Savings in I2R losses will be very small and most likely difficult to measure as it may fall within tolerances of the metering accuracy, I am afraid. On the other hand, please post your findings either way and it will be beneficial to all readers.