Energy-Saving Effects of the Intermittent Control of Pumps in Ground Source Variable Refrigerant Flow Systems with a Buffer Water Tank

Toya Tanaka, Sayaka Kindaichi (), Keita Kawasaki and Daisaku Nishina
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Toya Tanaka: Department of Civil Engineering and Architecture, Shikoku Electric Power Co., Inc., Takamatsu 760-8573, Japan
Sayaka Kindaichi: Graduate School of Advanced Science and Engineering, Hiroshima University, Higashihiroshima 739-8527, Japan
Keita Kawasaki: Department of Architecture and Structural Engineering, National Institute of Technology (KOSEN), Kure College, Kure 737-8506, Japan
Daisaku Nishina: Graduate School of Advanced Science and Engineering, Hiroshima University, Higashihiroshima 739-8527, Japan

Energies, 2024, vol. 17, issue 22, 1-15

Abstract: Variable refrigerant flow (VRF) systems are common air-conditioning systems used in regions with moderate climates that have cooling and heating demands. Unlike typical air-source VRF systems, ground-source VRF systems require heat-source water circulation, and reducing the pumping power remains a significant problem. Herein, the intermittent pump control for circulating heat source water was achieved by installing a buffer water tank between the ground heat exchangers and VRF units. An intermittent control methodology was developed based on the indices of water transport efficiency and incorporated into a system simulation model with 72 boreholes, a cooling capacity of 252 kW, and a buffer water tank of 30 m 3 . Results indicated that intermittent control was achieved at heat load ratios lower than 40% as expected. This intermittent control allowed more efficient water transport with 38% lower pumping power than conventional inverter controls. Although the proposed system equipped more pumps and heat exchangers than conventional systems, it exhibited higher energy efficiencies for most measurement days than the conventional air-conditioning systems. The annual energy consumption was thus reduced by 34% and 8% compared to air-source VRF systems and conventional ground-source VRF systems, respectively.

Keywords: ground-source variable refrigerant flow systems; buffer water tank; intermittent control; water transportation factor; energy consumption (search for similar items in EconPapers)
JEL-codes: Q Q0 Q4 Q40 Q41 Q42 Q43 Q47 Q48 Q49 (search for similar items in EconPapers)
Date: 2024
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