Energy retrofit of public office building through liquid desiccant assisted dedicated outdoor air system with fuel cell in Korea

Abstract

Zero-energy buildings have been mandated in many countries to reduce carbon emissions from buildings. Existing buildings are no exception, and should be retrofitted with renewable energy to be ZEBs. Fuel cells are attracting increasing attention owing to their high efficiency and lack of limitations on the installation area compared to photovoltaic panels. However, a fuel cell simultaneously generates heat and electricity; therefore, it is important to use heat efficiently when using a fuel cell. To achieve this, this study proposes using a liquid desiccant-based air conditioning system when the fuel cell is used for energy self-sufficiency in an existing office building. The configuration of an air conditioning system called thermoelectric and liquid desiccant-assisted dedicated outdoor air system (TELDOAS) is designed, and its annual control logic is established for cooling and heating season operations. To reveal the energy performance of the proposed system, detailed energy simulation models were developed by integrating all mathematical and empirical models of each component using MATLAB. The results revealed that 24.7% of the annual primary energy could be saved by adding a fuel cell to the current air conditioning system consisting of a heat pump and an enthalpy rotary ventilator (ERV). Moreover, the results showed that using TELDOAS instead of ERV could save an additional 32.3% of the annual primary energy by efficiently reclaiming waste heat from the fuel cell. The heat recovery ratios of each system are analyzed to prove the advantage of using TELDOAS, and heat recovery is increased from 37.1% to 51.2% by using heat during the cooling season.