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On/off controlled chiller is wildly used for small-scale air-conditioning (AC) system. For many existing systems, the chiller may be switched on and off frequently, which speeds up the wear and aging of the chiller and introduces significant disturbances on the space temperature control. This paper presents an experimental study on a control method which combines a set-point reset technique with a bilinear control technique. The set-point reset technique is adopted to reduce the on/off frequency of the chiller, and the bilinear control is used to track the space temperature set-point. The control method was realized in a building automation system (BAS) and applied to a test rig. The experimental results show that the set-point reset technique can reduce the chiller on/off frequency obviously. The bilinear control can achieve more robust space temperature control while comparing with conventional PI control. This proposed control method has the potential to be used in the existing on/off chiller integrated AC systems with the small chilled water volume. It is able to reduce the on/off frequency of the chiller efficiently and guarantee the robustness of the space temperature control simultaneously from the control role. [ABSTRACT FROM AUTHOR]

This paper presents an experimental study on a bilinear temperature control of a ground source heat pump (GSHP) integrated variable air volume (VAV) air-conditioning system, which may experience significant variations in the supply air temperature due to the frequent on/off switch of the ground source heat pump and the low thermal capacity at the air side. The bilinear control was realized in a building automation system (BAS) and applied to a test rig. The experimental results show that with an online estimation of the cooling load the bilinear control was able to maintain the space temperature at its set-point well and the control performance was superior to that of a conventional PI control. Therefore, the bilinear control has the potential to be used in GSHP integrated air-conditioning systems to improve the robustness and accuracy of the space temperature control. [ABSTRACT FROM AUTHOR]

This paper presents a method which combines the bilinear control technique with a set-point reset technique to control the space temperature when its cooling is provided by a GSHP equipped with an on/off capacity control, aiming to (i) improve the robustness of the space temperature control by taking account of load uncertainty; and (ii) to reduce the frequency of the GSHP on/off cycling by using the indoor space temperature set-point reset. When the GSHP is on, a smaller space temperature set point is used; while the GSHP is off, a larger set point is used. The proposed control was tested on a simulation platform, which consists of a ground source heat exchanger, a GSHP, an air-handling unit (AHU) and a middle-sized room. The test results show that the proposed control method is able to achieve a good control performance and has the potential to be applied to a real GSHP integrated air conditioning system to improve the robustness of space temperature control and simultaneously reduce the on/off frequency of the GSHP. [ABSTRACT FROM AUTHOR]