Abstract- The Low Voltage Direct Current (LVDC) system concept has been growing in the recent times due to its characteristics and advantages like renewable energy source compatibility, more straightforward integration with storage utilities through power electronic converters and distributed loads. This paper presents the energy efficiency performances of a proposed LVDC supply concept and others classical PV chains architectures. A PV source was considered in the studied nanogrids. The notion of Relative Saved Energy (RSE) was introduced to compare the studied PV systems energy performances. The obtained results revealed that the employment of the LVDC chain supply concept is very interesting and the use of DC loads as an alternative to AC loads, when a PV power is generated locally, is more efficient. The installed PV power source in the building should be well sized regarding to the consumed power in order to register a high system RSE. I. INTRODUCTION The photovoltaic electricity was primarily established for standalone applications deprived of any connection to a power grid. Such was the case of satellites or isolated habitations. Currently, PV's are found in many power applications like personal calculators, watches and other objects of daily use, they can supply many individual DC loads without difficulty. Due to the evolution of photovoltaic systems connected to the grid, the PV has considerably exploited as a solution to produce electricity. The main objective of this paper is to investigate the energy efficiency performance of a proposed Low-Voltage Direct Current (LVDC) PV system regarding to a classical LVDC architecture and classical PV systems using AC loads. All the studied PV chains are on-grid ones and are supposed supplying offices. In general, electric energy consumption in office applications and housing is achieved by using the alternative current plugs even for Grid Tie PV panel systems. In this case the use of AC's can increase system losses especially when DC current is used at the load levels. LVDC systems have been gaining more interest during the past few years both in academia and industry. LVDC systems offer many advantages covering higher energy efficiency and easier integration of modern energy resources in comparison to conventional AC systems. Multiple factors affecting the reliability performance and power quality of the electricity supply permit the use of DC systems instead of AC systems. Direct use of DC power would reduce many power conversion losses by exploiting self-consumption of the energy produced on site and decreasing imports of electricity from the grid. DC loads used in households and office buildings, also operate on DC, heating/cooling systems and larger equipment used in industry such as variable frequency drives have also adopted DC motors. Direct current power systems are essentially more efficient than their AC counterparts; since in DC systems do not suffer from skin effect or reactive power [1], [2], [3], [9]. A literature research has exposed the study of the first system analysis explored the use of very low voltage (<120 V) in small-size systems, particularly residential dwellings [6]. Subsequently, Lasseter R.H proposed the concept of the DC Microgrid as a low voltage distribution network. This concept was projected as the future low voltage distribution systems which were facing revolutionary variations at the time due to emanation of distributed generation and market liberalization. The basic idea behind this concept is to combine micro sources and loads into one entity which could be interpreted as a single dispatch-able load that could respond in short time to meet the transmission system needs [7]. For many years, The LVDC system has been developed for specific applications like aerospace, automotive and marine [4], [5], [8]. Literature review reveals that over the last decades, LVDC systems are growing rapidly for industrial applications, essentially in the telecommunication industry, ships and buildings. Adopting Direct Current in data centers Energy Efficiency of LVDC Supplies Including PV Sources 1 Department of Electrical Engineering, College of Engineering and Islamic Architecture, Umm Al- Qura University, KSA 2 Department of Electrical Engineering, National School of Engineers of Sfax, University of Sfax, Tunisia Received: March 3, 2021. Revised: March 29, 2021. Accepted: April 2, 2021. Published: April 6, 2021. INTERNATIONAL JOURNAL OF MATHEMATICS AND COMPUTERS IN SIMULATION DOI: 10.46300/9102.2021.15.9 Volume 15, 2021 E-ISSN: 1998-0159 46 Anis Ammous 1,2 , Abdulrahman Alahdal 1 , Kaiçar Ammous 2