On the Billing and Management of the Air Conditioning Loads in Electric Power Networks

Abstract

A model is presented for analyzing the impact of air conditioning load characteristics, such as daily cooling energy consumption, start time, and duration, on the overall economy of the power system. The article then suggests a tariff system aimed at encouraging customers with an air conditioning load to cooperate with the electric utilities toward saving energy, achieving diversity between the original load and the air conditioning component, applying cooling energy storage systems, and efficiently controlling the starting time and duration. A system of inverted energy blocks and an exponential penalty function are recommended in order to encourage the customer to operate the air conditioning during daily time intervals far from the customer's original peak. Both the combined maximum demand and the demand charge increase almost linearly with the p.u. energy consumption of the air conditioning load. If the cooling energy is taken over durations longer than 20 hr/day, the demand charge will be reduced to about 80%, based on the case in which the original and the air conditioning load are coincident. The more than proportional increase in the energy bill will encourage the customer to adopt some measures in order to save cooling energy. For a certain required air conditioning energy, the total monthly bill depends strongly on its staring time. The advantage of starting the air conditioning load before 0700 or after 2000 could be seen. With the shifting of the air conditioning load, the customer will realize that a monthly savings of up to approximately 17% can be achieved. The total monthly bill can fluctuate between a value in excess of $220,000 and approximately $150,000/month, depending on the way the air conditioning is operated. It could be found that there is a duration for which the total bill reaches a minimum with an optimal duration of 11.9 hr. The customer has to adjust the operation scenario of air conditioning such that the entire cooling load will take place during the off-peak period of the system's load curve. This will encourage the user to consider and check the feasibility of using cooling energy storage systems that can enable such shifting of the air conditioning load. It can be recognized that the proposed tariff structure can be an effective tool for implementing the recommendations of some utilities in this regard.