Optimal Control Of Air Conditioning Loads For Commercial Buildings

Air conditioning load constructs one of the main reasons for large peak valley load ratios in summer days in the urban areas,causing great difficulties for power supply and demand balance in the system peak load periods.As it’s not economical to increase generation or transmission investment for supplying the short peak load,peak-clipping-aimed air conditioning control has been increasingly concerned in recent years.The existing research on air conditioning control is mainly from the viewpoint of the electricity suppliers,the realization of which relies on the development of dedicated communication and control devices.This paper,however,presents a new air conditioning control method for the commercial buildings with building automation systems(BAS),which aims at reducing the electricity charges of air conditioning by periodically adjusting the interior temperature setpoint in the summer day.A parameter estimation method is first proposed for estimating the equivalent thermal parameters for the commercial buildings.Two air conditioning patterns,i.e.the precooling mode and the peak period temperature adjusting mode,are suggested for the electricity charge reduction purpose.After that,an optimization model is presented for minimizing the air conditioning charge by periodically adjusting the setpoints in the summer day.A case study is provided towards an office building located in the Jinshan District,Shanghai.The feasibility of the presented control method is examined from the aspects of setpoint regulation period,permitted range of interior temperature variation,starting time of system peak period and the peak-to-valley price ratio.Results show that the amplitude of electricity charge saving relates with the adjusting cycle and admitted range of variation of the interior temperature,the shorter the cycle and the higher the interior temperature permitted,the more the electricity charge can be saved.Another result is that precooling is feasible only for the buildings which start operationsynchronizingly with the system peak period.The amplitude of charge saving caused by precooling is related with the peak-to-valley price ratio,the larger the price ratio,the more the electricity charge can be saved.