Design of direct solar PV driven air conditioner Bin-Juine Huang a, * , Tung-Fu Hou a , Po-Chien Hsu a , Tse-Han Lin a , Yan-Tze Chen a , Chi-Wen Chen a , Kang Li a , K.Y. Lee b a Department of Mechanical Engineering, National Taiwan University, Taipei, Taiwan b Department of Engineering Science and Ocean Engineering, National Taiwan University, Taipei, Taiwan article info Article history: Received 17 July 2015 Received in revised form 31 October 2015 Accepted 7 November 2015 Available online xxx Keywords: Solar cooling Solar air conditioning Solar PV cooling abstract Solar air conditioning system directly driven by stand-alone solar PV is studied. The air conditioning system will suffer from loss of power if the solar PV power generation is not high enough. It requires a proper system design to match the power consumption of air conditioning system with a proper PV size. Six solar air conditioners with different sizes of PV panel and air conditioners were built and tested outdoors to experimentally investigate the running probabilities of air conditioning at various solar ir- radiations. It is shown that the instantaneous operation probability (OPB) and the runtime fraction (R F ) of the air conditioner are mainly affected by the design parameter r pL (ratio of maximum PV power to load power). The measured OPB is found to be greater than 0.98 at instantaneous solar irradiation I T > 600 W m À2 if r pL > 1.71. R F approaches 1.0 (the air conditioner is run in 100% with solar power) at daily-total solar radiation higher than 13 MJ m À2 day À1 , if r pL > 3. © 2015 Elsevier Ltd. All rights reserved. 1. Introduction The cooling load and the energy consumption of air condition- ing system in buildings or vehicles are in phase with solar radiation intensity. Solar cooling is thus promising. Many researchers developed solar cooling technology using absorption or adsorption chiller [2,5]; or ejector cooling [9,11] driven by solar thermal en- ergy. Collector used to drive absorption, adsorption, or ejector chiller requires high energy conversion efficiency at high temper- ature. Usually, vacuum-tube or parabolic-trough collector is used. The cost of collector as well as heat-driven chiller is high and makes the solar cooling not economical. Recently, many researches study solar cooling using vapor- compression cooler driven by solar PV system since solar PV sys- tem cost falls down very fast. Hartmann et al. [4] compared theo- retically solar thermal and photovoltaic cooling for a small office building in Freiburg and Madrid and found that the grid-tied PV system has lower cost of primary energy savings. Similar result is obtained by Ref. [16]. Both [4] and [16] assumed that the PV system used in solar cooling is grid-tied type which does not have energy storage (battery). In these solar cooling systems, the power grid will supply electricity for cooling when solar energy is not available. In off-grid applications, solar air conditioner needs to be pow- ered by stand-alone PV system. The design of stand-alone solar cooling system is complicated in view of possible loss of power during low solar radiation periods. A typical example is solar refrigerator. The electricity is produced by photovoltaic panels to drive refrigerator based on vapor compression cycle through bat- tery, charge controller [3,13,17,18] and inverter [14,15]. Axaopoulos and Theodoridis [1] designed a solar photovoltaic powered ice-maker which operates without the use of batteries and may be used in truly autonomous applications in remote areas. The refrigerator is made of four compressors. The operation of the compressors by the PV panels is ensured by the use of a controller, which provides startup, maximum power tracking and power management for the four compressors of the system. Solar air conditioner is different from solar refrigerator in cooling capacity and load pattern. The refrigerator is always well- insulated and the cooling load may be increased only when it is suddenly or frequently opened. The effect of thermal mass plays a significant role in stabilizing the refrigerator temperature. In addition, the cooling power is usually small for refrigerator. For air conditioner, the cooling load is usually large, in several kW, and may vary with solar radiation intensity and outside air temperature. Air filtration or people moving to or from the cooling space also affect the cooling load. Besides, solar radiation may fluctuate. All of these make the design of solar air cooling system * Corresponding author. E-mail address: bjhuang@seed.net.tw (B.-J. Huang). Contents lists available at ScienceDirect Renewable Energy journal homepage: www.elsevier.com/locate/renene http://dx.doi.org/10.1016/j.renene.2015.11.026 0960-1481/© 2015 Elsevier Ltd. All rights reserved. Renewable Energy 88 (2016) 95e101