Optimizing energy consumption of a water-loop variable-speed heat pump system

Water-loop heat pump (WLHP) systems have been widely used for decades. The most appealing feature of WLHP is its capability of handling simultaneous heating and cooling demands in a building and recovering heat generated from zones in cooling. The typical heat sink and source are cooling tower and boiler. WHLPs discussed in this paper are equipped with a variable-speed compressor; the cooling tower comes with one variable-speed fan; and the boiler has a continuously-adjustable capacity. This paper analyzes how the energy efficiency of individual component responds to variations in loop water temperature; demonstrates that there exists a unique loop-water temperature that minimizes overall energy consumption given a certain building load; proposes a practical strategy to find the optimal temperature in a real-time manner.