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Select your topic of interest:
- What is the power factor?
- Power control in off-peak period
- Energy management - complete management systems
- Wire mesh heating systems
What is the power factor?
To clearly understand power factor, it is imperative that resistive and inductive loads be explained.
Theresistive loads will use 100% of its power to produce work. WOW! That is not too clear, is it? Let's look at it this way: an electric heater that has a demand of 100 kW will give out 100 kW of heat. No losses! Pure and total "work". Incandescent light bulbs that have a demand of 10 kW, will give 10 kW of lighting. The power used to operate a resistive load is called the kW demand or the "real" demand.
If you would look at the wave form of a resistive load, you would see that the amperage and the voltage are on the same wave, in phase.
On the other hand, inductive loadsuse some of its power to operate, and the balance of the demand to "work". An electric motor uses some of the power to magnetize the core and the balance for "work", produce horse power. Same thing for a transformer, ballast, etc.
The power used to operate an inductive load is called kVA demand, or "apparent" demand. The inductive loads do create a dephasing of the wave : the voltage wave form and the amperage wave form are no longer in phase.
The graphics below are showing the difference between the kW and the
kVA wave forms.
What is power factor? In simple terms, power factor is the ratio of KW
versus kVA. (P.F. = kW/kVA). It is formulated in percentage. (900 kW/1000
kVA=90%). Thus, it is also the ratio of real demand/apparent demand.
Why should power factor be improved?
The most frequent answer to that one is very simple: MONEY !
Most utilities will penalize a bad power factor. In general, the acceptance is a 90% power factor. In some cases, penalties will be applied if power factor is below 95% or even 100%. Some utilities will show on their invoices the penalties, some others will not. Some will not show the penalties, but will show the power factor. Some will not even tell you anything. To explain how the penalties are applied on your invoices, we will use the way our local utility does it. On our invoices, the following information is supplied: Power Factor, Real Demand, Apparent Demand, Invoiced Demand.
This is quite complicated, you might think. But, in fact, it is very simple. The regulation is that the utility will invoice the highest of 100% of kW Demand or 90% of kVA Demand. Let's clarify that with an exemple: kW demand = 1000. kVA demand = 1500. Power factor is 66.6% (kw/kva). The utility will invoice the greatest of kW demand (1000) or 90% of kVA demand (1350). Invoiced demand would be 1350, this being the highest between kW demand and 90% of kVA demand.
The penalty in itself might not be shown on the invoice, but in the above situation, the surcharge would be for 350 kW (1350 - 1000). Assuming that the cost per kW demand is approximately $10/kW, and that this condition repeats itself every month, this would represent a monthly penalty of $3,500.00, or an annual potential saving of $42,000.00.
Other benefits in improving power factor
True, power factor improvment can definitely secure interesting savings, but there are other interesting advantages in having a good power factor. One of them is unloading the transformers.
For instance, if you have a 1000 kVA transformer and that the load on this transformer is 1000 kVA with a 70% power factor, improving the power factor to 90% for instance will reduce your load to 778 kVA, allowing you to add loads on this transformer. (1000 kVA x .70 to get the kW demand) /.90 (to determine new kVA at 90% power factor). This would reduce the load on your transformer by 222 kVA.
How to improve power factor?
The most economical and common way to improve power factor is with capacitors. The capacitors will "rephase" your power, thus reducing the kVA demand.
Where should they be installed? There are different ways to do this: on each motor, at the main service entrance, an automatic power factor correction system, on low voltage, on high voltage and finally, a combination of what is best suited for the application.
Our approach is to sit down with our customers and determine what avenue would be best for them. We are available at your convenience to help you evaluate your needs. Do not hesitate to contact us.
Products
Gestelec Inc. offers your top quality products for power factor improvement: automatic power factor correction systems with or without harmonic reactors and static capacitors for wall or floor mounting. Components used in these products are from well known manufacturers for good quality products with high life expectancy in industrial and commercial applications. All Gestelec products come with a one year warranty. Why don't you use this PRODUCTS link and have a better idea of the products we offer! Please, be our guest and don't hesitate to send us your comments !
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Power control in off-peak period
The principle of demand control is quite simple: it's the operation of given loads during off-peak periods. Let's look into this principle a little deeper by simulating off-peak electric heating.
An industry has a peak demand of 500 kW for it's production equipment. The heating source is electricity for a total of 300 kW. During non heating months, the peak is 500 kW and during colder months, when heating is required, the peak could go up to 800 kW. (500 kW for production and 300 kW for heating). Demand control consists in restricting the heating to a maximum peak and this, without affecting comfort in the building. As a rule of thumb, 50% of electric heating can be used during off-peak periods without affecting comfort. Based on this principle, the peak for this industry would be 650 kW during heating periods (500 kW for production + 50% of heating load (150 kW). This would ensure a reduction of 150 kW on demand.
The graph represents what would happen with heating loads operating with the peak limited at 650 kW.
Based on the above explained principle and on a cost of $10 a kW, an annual saving of $6 000 would be secured with peak demand controlling.
In order to ensure the efficiency of a peak load demand controller, it is important to take into consideration the load factor: consumption used versus potential consumption.
The most common sheddable loads are: ambient electric heat, hot water heaters, air conditioning, ventilation. In some distinct cases, production equipment can be operated during off-peak periods. This has to be determined with the production specialist of the industry. Wire-mesh in-floor electric heating or snow melting systems can be operated in a very economical way with peak load demand controllers.
All the sheddable loads are operated under a "cycling" principle to ensure that the ambient temperature will be satisfactory in all parts of the buildings.
The peak load demand controller can be supplied with outdoor temperature sensor to automatically adjust the set point of the controller. This approach would provide additional savings.
We are available at your convenience to assist you in evaluating the potential savings and the requirements of your application. Do not hesitate to contact us.
Energy management - complete management
systems
Gestelec's Series GES6000 offers an interesting and affordable choice of superior quality peak load demand controllers and energy management systems. Designed with microprocessor modules of 4, 8 or 32 inputs/outputs, each of these modules can operate either as stand alone units or connected into a network. Whatever the way they are used, they are stand alone units and, in some cases, require a non dedicated IBM compatible computer to act as an accessory to modify the parameters of operation and display the conditions of the building. From a basic peak load demand controller to a total energy management system of over 200 inputs/outputs these systems are all microprocessor based. One of these systems will certainly meet your application.
- Microprocessor based.
- 4 outputs, extendable to 12 outputs.
- 8 amps, 240 volts, dry type output contacts.
- Metering in amps only.
- Digital display.
- NEMA 1 Cubicle.
GES6200 - This controller offers additional options to the basic
demand control: daily, weekly, monthly and yearly scheduling, programmable
to meet the customer's application. Some of the other available options
are differential for each load, multiple clyclers, IBM PC compatible,
modem connection, etc.
GES6400 - Total Energy Management System with universal inputs
and outputs (analog or digital), with the following functions: peak load
demand controlling, multiple differentials, temperature monitoring, temperature
setback, optimal start, personalized operating menu,operating from an
IBM compatible computer, network operation, graphics, humidity monitoring,
gas monitoring, etc. The GES4000 is a complete, versatile personalized
system.
GES6800 - This model completes our line of controllers. Gestelec
Inc. offers the possibility of designing your custom made system. A microprocessor
based controller with universal inputs/outputs permitting to widen the
choice of usage. With the appropriate software, the GES6800 can
fill out any monitoring and control functions you can think of. Our programmers
will be pleased to evaluate your needs and give you full support. Please
feel free to contact us at your convenience.
GES6200 - GES6400 - GES6800
- Microprocessor based
- Stand alone controller
- Modular assembly on tracks
- Universal inputs and outputs
- Analog or digital inputs and outputs
- Dry type output contacts rated at 8A, 240 volts
- Digital display or IBM PC compatible computer operation
- Custom Applications
- Ease of operation and programming
- Operating Menus on IBM Compatible computers
- NEMA 1 cubicle with key lockable door
- Expendable with additional 8 inputs/outputs modules
- Modular approach
- Non dedicated IBM PC compatible
- (RS485) allowing greater distances (8000 feet)
- Password protected
- Modem Connection
- Cycling of sheddable loads
- Analog or digital inputs
- Network Connection
- Pulse metering
Wire mesh heating systems
The comfort of radiant floor heating is not new. The wire mesh heating system utilizes the standard reinforcement grids in concrete floors as a low density heating element. As a result, the installation costs compare favorably with other compatible methods of heating, but there are no heating cables to break or deteriorate.
The thermal capacity of the concrete floor, and the ground beneath the floor, form a large heat reservoir. This reservoir will supply a continuing source of heat if the electrical power is disconnected for periods of time. The reservoir is so effective that when the electrical energy is interrupted, the temperature will only be reduced my 1/2 of a degree per hour, when the outside temperature is zero. This enables the heating system to effectively utilize the "off peak" rates offered by many of the utility companies. When connected to a peak load demand controller, the wire mesh heating system provides one of the lowest operating costs available.
The main element of the wire mesh heating system is a heavy duty transformer which electrically energizes the structural reinforcing grids. The resistive characteristics of the were mesh convert the electrical energy into a radiant heat source which provides comfortable, draftless, low intensity heat, exactly where you want it.
The temperature controls normally consist of slab thermostats to control the maximum surface temperature of the concrete and room thermostats to control the comfort.
APPLICATIONS
The main applications of wire mesh heating are:
- Space heating
- Snow melting
- Frost barrier
ADVANTAGES
There are many advanatages by using a wire mesh heating system :
- Comfort
- Economy
- Less design time
- Saves space
- Can operate on "off-peak" periods
- Reliable
- Efficient
- No maintenance
- Lower insurance
- No pollution
- Explosion proof
INSTALLATIONS
- Plants
- Sports arenas
- Saw mills
- Commercial buildings
- Institutional buildings
- Transportation terminals
- Outdoor sidewalks
- Outdoor parkings
Do not hesitate to contact us or take a look at the schematic installation for more information. You may also click here to see what wire mesh looks like. We will be glad to send you more information on this type of electric heat.