PROGRAM OF CONTROLLING THE AIR-CONDITIONING LOADS OF THE MAJOR CUSTOMERS

The application of the electricity loads control aims at reducing the maximum load and recessing the large increases in the electricity loads which are experienced by Saudi Electricity Company, that account for 2,000 MW annually. For the purpose of achieving this goal, SEC applied a special system in this concern, to control the loads of the A/C systems in the summer of 1995 during peak load period, which extend from Saturday through Thursday (from 13:00 to 16:00 during summer, June to September).

This system represents a direct intervention in the power utility to control the A/C systems units, for the purpose of reducing their loads, and ultimately reduce the peak load of the electrical network. The company applied this system to control the operation of the A/C systems of the Major customers, and reduce their loads at different rates during the above mentioned peak load periods.

This system included all the A/C coolers (large coolers), split units, and combined A/C units, control systems and relays. This system includes the installation of relays, control and communication systems on the A/C appliances at the customer's location. In this concern, SEC provides all the required controls and equipment for this system, in addition to the operation and maintenance.

SEC's contractors and consultants installed these equipment at the location of the customer and ensure their operational safety for the A/C systems. The selected customers of this system are required to do the following:

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

- Written consent to apply this system on the A/C systems and units that are already available with the customer.

- Allow the contractors and consultants of the Company to enter the locations of the A/C systems and their accessories in the building of the customer to install the system devices, electrical fittings and internal communication for the customer, and shall be allowed to check and maintain these devices whenever needed.

Here Below Steps for Operating This System :

Operation Steps of the Central Air-Conditioning Coolers :

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 main building of the Company. The system calculates the reduced amount/rate of the power load by a software duly designed for this purpose. Then high frequencies radio signals are created and sent through the communication network to the receivers installed at the selected customers' locations. Once the signal is received and decoded, it will be sent to one of the relays specially programmed to reduce the coolers load to the desired level, and restrain it to this limit for the required period.

2- Starting the coolers in this matter will be carried out only in case of the system is operated and signals are sent from the control center. Therefore, if this system was not operated, then the coolers will operate by its own control system without the intervention of SEC.

3- Controlling the coolers through this system will reduce the timely power load of these coolers, which will be done in two stages :

- Stage one:   Reducing the coolers' loads by (20%) and limiting their load at (80%), only for one hour, which operation will start at 1:00 pm.

- Stage two:   Reducing the coolers' loads by (40%) and limiting their load at (60%) starting at 2:00 pm. It is worth noting that their operation time of this stage will be very close to the end of the work day of the workers in these buildings, which means that the period these systems will be affected by the high temperatures will be relatively short for the building users.

Furthermore, the coolers fans will continue functioning normally during these stages, without the intervention of the system in these fans.

Load Management Strategies:

The following curve shows how the load management changes the curve of the electric grid load according to the desired target. The objective may be reducing the peak load through the use of an 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 :