Power Factor Correction to Boost Your Bottom Line

User Rating: / 0
PoorBest 

Written by Electrical Line Magazine
Posted in Electrical Distribution - Power Factor

As companies look for ways to become greener power factor correction is providing opportunities to be a better environmental steward, but also to potentially save some cash along the way. Here's how companies are saving green by being green.

What Is Power factor and why should I care About It?

Power factor is a measure of efficiency in the use of supplied power. Mathematically, it is the relationship between Working Power (power that does the "work" for the system such as, light the lights and drive the motors) and apparent power which is the s& of working power and reactive power (power required to sustain electromagnetic field required by motors, transformers and relays for them to operate).

Inefficient use of power means that the more power must be supplied by utilities to meet a companies needs. Electrical items, which are staples for many facilities – such as variable frequency drives, uninterruptable power supplies, motors and even some lighting banks – are notoriously are inefficient and therefore have very poor power factor. So the problem lies not just with large manufactures or heavy computer users. Virtually every facility can benefit from some level of power factor correction. Just how much correction is needed is a function of economics – which we’ll discuss later. Regardless of the economics involved, all facilities can benefit from a reduced carbon footprint as a benefit of improving power factor.

Improved Power Factor Reduces Carbon Footprint.

Let’s assume that a typical plant has a 1500 KVA demand and uses 500,000 KWH/month. Typical I (squared) R losses can be as high as 2% of the KWH consumption, resulting in 120,000 KWH saved annually. Transformer losses can account for an additional 10% KWH loss as well. On average a KWH produced generates about 1.25 lbs. of CO2. This is derived from US government data for electrical demand and carbon footprint. Actual figures may vary from 0.8 lb. to 2 lbs. per KWH depending on the percentage of electricity generated by coal, oil, gas or non fossil fuels such as nuclear, hydro, solar or wind.

Greening the Bottom Line Too.

In addition to the carbon footprint reduction that accompanies each fore factor correction project, there is another reason that power factor correction should be “top of mind.” Recall that the inefficiency hinders not the user but the supplier of power because more energy is required due to the inefficiencies. Utilities that are strapped for capacity are unable to supply more electricity without major capital investments. Rather than absorb this internally, utilities are increasingly restructuring their rate plans to include a surcharge for poor power factor or a charge per KVA. As a result, users with poor power factor are paying additional sums to support their inefficient usage habits.

Let’s assume that a facility requires 1500 KW and has an apparent power 1921 KVA and 1200 KVAR of utility supplied power. Keeping in mind that PF = KW/KVA, then this facility has a power factor of just 78% (1500/1921). Let’s also assume the utility supplying power charges $1.10/KVAR demand in excess of 1/3 of the KW demand. For our example, the excess KVAR is 1200 – 1500 / 3 or 700 KVAR. To improve their power factor and eliminate the power factor penalty, this facility can add 700 KVAR of customer supplied power by adding capacitors. Under the new scenario the new PF = 1500 / 1581 or 95%.

Adding 700 KVAR would save over $9000 per year resulting in a payback of as little as 2 years.

Including the KVAR demand charge shown in the example above, utilities can also charge for poor power factor three ways.

1. KVAR demand charge (shown above)
2. KW demand charge (must include a target power factor and adjust the KW demand for actual power factor)
3. KVA demand charge – any time that the facility is billed for the KVA they are paying a power factor charge!

If utility invoice includes one of these three, then they are charging for poor power factor. Each utility invoices differently – so prior to planning your power factor correction strategy, you should look at your utility bill.