Dencor Digital Demand Controller

 
Dencor Digital Demand Controller
Increase Margins by Lowering Utility Costs

Covenience Store Applications

When you attend a concert, do you prefer listening to the squeaks, ekes, booms, and twangs of the pre-concert warm-up, or do you prefer the smooth-flowing, melodious harmony of the formal musical presentation? Certainly you prefer the latter.

When it comes to your C-store equipment and systems, is everything operating in the "warm-up" mode or running in concert, like a performing orchestra?

To lower operating costs (raise margins) you want to ensure that equipment is operating optimally. You can do this by orchestrating the operation of major equipment within the store. To orchestrate means "to organize, manage, or arrange so as to achieve a desired result or effective combination." Managing and arranging the operation of equipment will result in reduced operating costs.

How is this achieved? By using a "conductor" C a digital demand controller - to direct the orchestra! Let me explain.

First you should understand how you are billed for electricity. Most electric bills consist of three primary components:

Fixed charge (monthly facility or service charge)
Energy charge (kWh)
Demand charge (kW). Demand charges typically comprise about 40 percent of your total monthly electric bill.

The fixed charge is a monthly fee you pay for your electric service, regardless of how much electricity you consume during the month. Monthly charges typically range from $5 to $25 per month.

The energy charge is for units of electricity termed kilowatt-hours (kWh). You probably pay between 4 and 11 cents per kWh, depending on your region. Consumption of kWh is reduced by installing energy-efficient equipment and by performing regular maintenance. Energy consumption can be reduced by:

Cleaning fans and coils frequently (just a light coating of dust reduces efficiency by 20%)
Installing T-8 or T-5 fluorescent light fixtures inside and pulse-start metal halide or Sylvania fluorescent "Icetron" outside
Utilizing astronomic clocks to control lighting instead of conventional photo sensors, switches and timers
Using only motors that are rated "high-efficiency, high power factor"
Weatherizing the building to decrease heating and cooling requirements

In the past, reducing energy (kWh) has received most of the attention. And certainly it's worth continuing to do these things. But, there's low hanging fruit to be grabbed elsewhere! Look at the "other" part of your electric bill C the demand charge.

The demand charge is for units of electricity termed kilowatts (kW). Demand is the total amount of electricity being used at a given moment in your store. Demand charges generally pay for the capacity of the generation and transmission grid that delivers power to your doorstep. The maximum amount of electrical power you momentarily need during the month is your "peak demand." The store may average 60 kW during the month, but have a peak demand of 80 kW. Random, unorchestrated operation of equipment will "spike" the demand momentarily during the month. You are billed for the 80 kW peak demand. So, if you reduce kW, you reduce your electric bill. It's that simple.

In many areas of the country, demand charges are already high, or they are increasing. So, reducing demand is becoming increasingly important. You can reduce peak demand in a simple, cost-effective way by installing a digital demand controller (DDC).

What is a DDC? It's a compact relay box with powerful programming and data gathering capabilities. Mounted anywhere in the utility room it uses low voltage wiring to intercept existing thermostat or control circuits on controllable equipment. A pulse meter (from the utility) provides real time input so kW can be determined and demand limits can be set to maximize savings. Temperature sensors are installed to record freezer, cooler and HVAC performance during control times. A modem is installed to allow dial-in access to the DDC for remote monitoring and adjustment.

Here's the idea in a nutshell. The utility meter records the highest level of demand each month and establishes your billing level for the entire month. To lower demand and associated costs, install a DDC to prevent all connected equipment from operating simultaneously. In other words, orchestrate!

By preventing major equipment from operating randomly and unexpectedly, like various instruments during a warm-up session, a DDC will act like a conductor. It will direct each piece of connected equipment when to run, and when to stop. As a result, the entire equipment group will perform in concert.

By doing this, the peak demand can generally be reduced 10C15 kW per store per month. So, if your utility charges $10 per kW, and demand is lowered 15 kW, your bill will be reduced about $150 that month. In a year, this would reduce your operating cost $1,800. The aggregated savings potential for multiple stores is significant:
Programmed kW Reduction Using DDC

Utility Charge/kW of Demand

1 Store per Month Savings

10 Stores per Month Savings

100 Stores per Month Savings

1,000 Stores per Month Savings
10 kW
$8
$80
$800
$8,000
$80,000

10 kW
$10
$100
$1,000
$10,000
$100,000

10 kW
$12
$120
$1,200
$12,000
$120,000

10 kW
$14
$140
$1,400
$14,000
$140,000
Programmed kW Reduction Using DDC

Utility Charge/kW of Demand

1 Store per Month Savings

10 Stores per Month Savings

100 Stores per Month Savings

1,000 Stores per Month Savings

12.5 kW
$8
$100
$1,000
$10,000
$100,000

12.5 kW
$10
$125
$1,250
$12,500
$125,000

12.5 kW
$12
$150
$1,500
$15,000
$150,000

12.5 kW
$14
$175
$1,750
$17,500
$175,000
Programmed kW Reduction Using DDC

Utility Charge/kW of Demand

1 Store per Month Savings

10 Stores per Month Savings

100 Stores per Month Savings

1,000 Stores per Month Savings

15 kW
$8
$120
$1,200
$12,000
$120,000

15 kW
$10
$150
$1,500
$15,000
$150,000

15 kW
$12
$180
$1,800
$18,000
$180,000

15 kW
$14
$210
$2,100
$21,000
$210,000

Demand charges vary from utility to utility. The amount of demand that can be controlled may also vary from month to month, depending on weather conditions, the level of member activity and the amount and type of store equipment installed.

For the past year, Dakota Electric Association has installed DDCs for C-store chains in the upper Midwest, including Speedway SUPERAMERICA, Yocum Oil Company and Severson Oil Company. Experience has shown that a demand reduction of 10 C 15 kW is typical. Demand profiles and control strategies vary somewhat from store to store due to differences in equipment, lighting load, and car wash activity.

Benefits and Features of a Digital Demand Controller

Targeted loads that can be controlled include: Compressors for walk-in coolers, freezers, and HVAC; door warmers; electric space heaters; electric water heaters; snow and ice melting cables; stand alone reach-in coolers or freezers; selected lighting; and other loads that can be interrupted for as little as 7-8 minutes.
Installation is easy and requires about 7 hours. Most wiring involves low-voltage control wire. Back-up thermostats and sensors virtually eliminate the possibility of over-temp conditions in freezers and coolers.
Remote, dial-in capability permits monitoring and adjustment from anywhere. After initial set-up, quarterly monitoring will maximize savings and efficiency.
Building/load profile data can be downloaded to your PC as often as desired for reports and analysis.
Financing is often available from 3-6 percent. Leasing is another option. Some utilities like Dakota Electric Association near Minneapolis, MN permit members to make payments for DDC installations on their monthly power bill.
Turn-key installation in the upper Midwest averages $3,800 - $4,200. The DDC may also be purchased and installed by your own contractors or service personnel. Factory training is available.
Payback is generally 1-3 years, depending on utility demand charges in your area (see savings charts above).
10-year warranty. The DDC has a 25-year record of high performance and is practically maintenance-free. It has a "no hassle, no worry" warranty.

While utility costs may not be the biggest expense you're dealing with every day, a DDC is something quick and easy to do. Grab the savings and move on to other things.

Remember, demand (or kW) comprises a large part of your monthly electric bill. Cut the kW, cut the cost of operation. Orchestrate! Use a DDC to automatically manage and arrange the running cycles of major equipment in your store. You'll achieve the desired results -- Savings. Now that's music to anyone's ears!

Mark Kortkamp is a Business Account Executive for Minnesota-based Dakota Electric Association. You may contact him at 1-800-874-3409. Dakota Electric is one of the largest electric cooperatives in the United States and is a Touchstone Energy Partner. Touchstone Energy is an alliance of more than 600 electric cooperatives nationwide that collectively serve 590,000 commercial and industrial members coast to coast. Cooperatives provide electricity, products and services at cost to their customer-members who own them.
Brian LaFreniere (left), Northern Aera Project Coordinator for Speedway SUPERAMERICA, and Mark Kortkamp of Dakota Electric Association discuss control strategy for the walk-in cooler. Strict temperature control is maintained using a sensor and backup thermostat.
Jake Selseth, project manager for Dakota Electric Association, makes a final check of the DDC's control wiring at a Yocum Oil store in Eagan, Minn.
Mark Kortkamp (right), Business Account Executive with Dakota Electric Association, explains some functions and features of the DDC computer to Brian LaFreniere of Speedway SUPERAMERICA.
This DDC is installed and ready to go at a Yocum Oil C-store in Lakeville, Minn., a larger store with a car wash. Six of the standard eight 2-pole dc relays are being used.