One of the major problems with using renewable energy is the mismatch between power generation and demand as renewable energy generation and energy usage from HVAC equipment depend on unsynchronized natural factors. To reduce this supply-demand mismatch many researchers suggested using thermal energy storage to shift cooling and/or heating loads. A thermal energy storage (TES) tank can be integrated with building heating and cooling systems using several methods described in the open literature. This thesis explores a novel method to integrate water-based TES with an indoor air coil using a three fluid heat exchanger (TriCoil(TM)). The three fluid heat exchanger will thermally connect water from the TES, refrigerant from the outdoor unit, and indoor air. A test setup has been developed inside the Psychrometric Coil Testing Facility of Oklahoma State University (OSU) to test the TriCoil(TM). The heat balance of the test setup for different operation modes and test points was within +/-5%. An uncertainty analysis has been performed on the test results and major sources of uncertainties have been identified. In the experiment done for this thesis, water from the TES was successfully charged up to 15 kW (cooling) with a log mean temperature difference (LMTD) of 18.5 K using a 4-ton capacity outdoor unit. TriCoil(TM) was also used to discharge the water from TES with a max capacity of 11.5 kW (heating) with an LMTD of 8.7 K, a water flow rate of 1700 kg/h, and an airflow rate of 1600 CFM.