AIR-CONDITIONING LOADS CONTROL PROGRAM FOR MAJOR CUSTOMERS

The application of controlled electrical loads aims at reducing the maximum load and recessing the large increases in electrical loads as experienced by Saudi Electricity Company, which account for 2,000 MW annually. For the purpose of achieving this goal, SEC applied a special system to control air conditioning (AC) loads during peak period in the summer of 1995, which run from Saturday through Thursday from 12:00 noon to 5:00 pm,  during the months of May to September.

This system represents a direct intervention in power facilities to control and reduce AC loads and ultimately reduce the peak load in the electrical network. The company applied this system to control the operation of AC systems of major customers, and reduce their loads at different rates during peak demand mentioned earlier.

This system includes all central AC chillers (large coolers), split type units, and integrated AC systems, control systems and relays. It also includes the installation of relays, air conditioning control and communication systems at the customer's location. In this concern, SEC provides all required controls and equipment for this system, in addition to their operation and maintenance.

SEC's contractors and consultants installed these equipment at the customer's location and confirmed the operational safety of the AC systems. The selected customers to this system are required to do the following:

- Cooperate with the company to bring this project to success.

- Written consent allowing the application of this system on all installed AC systems and units in customer's facilities.

- Allowing entry of contractors and consultants of the Company to locations of the AC systems and their accessories in the building to install system devices, perform electrical connections to electrical network and internal communications of the customer, and to carry out maintenance checks on these devices whenever needed.

The Following Steps Explain the Operation of This System :

Operating Steps for Central Air Conditioning :

1- When there is a need to reduce the power load during the peak period, SEC will operate the system from the control center of the Company's main building. Where the system calculates the amount/rate of electrical load to be reduced by means of computer-aided software designed specifically for this purpose. High frequency radio signals are then generated and sent through the communications network to the receivers installed at selected customers' locations. Once the signal is received and decoded, it will be sent to an air conditioner relay specially programmed to reduce the cooler's load to the desired level, and maintain it at that limit for the required period.

2- Running the chillers in this manner can be carried out only when the system is operated and signals are sent from the control center. Therefore, if this system is not in operation, then the air conditioner will operate, aided by its own control system, without the intervention of SEC.

3- Controlling air conditioners through this system will reduce their electric load duration, which can be done in two stages :

- Stage one: Reducing the cooler's load by 20% and maintaining the load at 80% for one hour, starting at 1:00 pm.

- Stage two: Reducing the cooler's load by 40% and maintaining the load at 60% starting at 2:00 pm. It is worth noting that operation time for this stage will be very close to the end of the work day within the building. Therefore, the impact of a warm temperature on building users will be relatively short.

Furthermore, the air conditioning fan will continue functioning normally during these stages, without system intervention.

Load Management Strategies:

The following curve shows how load management changes the curve of the electric grid load according to the desired target. The objective may be that of reducing the peak load through the use of auto generation or stopping certain production lines, or through the use of the thermal energy storage system.

Load management changes the curve of the electric grid load :