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.