Advantages of Enhancement of Street Lighting Infrastructure with DC link A. Suzdalenko 1 , I. Galkin 2 1 Riga Technical University, Kronvalda boulevard 1 -324, LV1010, Riga, Latvia, E-mail: aleksandrs.suzdalenko@rtu.lv 2 Riga Technical University, Kronvalda boulevard 1 -324, LV1010, Riga, Latvia, E-mail: gia@eef.rtu.lv ABSTRACT: The present paper deals with analysis of advantages of enhancement Street Lighting Infrastructure with DC link. The dynamics of electricity price and Solid State Lighting (SSL) technology development are discussed and prognosis is drawn for the nearest future, based on statistical data. The advantages of implementation of Direct Current (DC) link for supplying street lighting grid are discussed, as well as connection of Renewable Energy Sources (RESs) to the lighting grid is proposed. 1. Introduction The energy consumed in the sphere of artificial illumination shares about fifth part of the global electricity market, which, in turn, has great potential for energy saving initiatives. Street lighting represents one of the noticeable parts of artificial illumination, for which 40% of municipality’s budget is spent in average, making great interest for minimisation of these expenditures. Another research [1] results that saving 1 kWh of electrical energy, potentially could save the equivalent of 2 kWh of fossil fuel. It relates with the total system efficiency of energy delivery from mining site to an end- user. The losses occur at each stage of energy delivery process, like use of energy during mining process of fossil fuels, energy conversion and transmission (mechanical and electrical) losses, as well as end-device efficiency. Consequently, locally generated energy (especially from renewable energy sources) is much preferable, because it excludes the major of the mentioned losses. The concept of intelligent building, which is defined as “building, that provides a productive and cost-effective environment through optimisation of its four basic elements - structure, systems, services and management - and the interrelationships between them”, can also be projected on the street lighting infrastructure, that could utilize renewable energy sources as lighting poles are mostly located in open-air. This is confirmed by various projects happening all over the world, creating autonomous street illumination, which is based on energy accumulation in batteries during day and using it by night to supply the lamp. Nevertheless, reliability of such system is insufficient due to unpredictability of weather and limited lifetime of batteries. However, there are known other projects like “SCOTIA” [2] or “Solar Street Lights USA” [3], which utilises lighting poles with equipped Photo-Voltaic (PV) panels and energy efficient luminaries to implement intelligent street lighting infrastructure – during night lighting poles are powered from the main utility grid, but during day PVs supply valuable energy to the grid. This system greatly reduces the initial investment, as eliminates use of batteries. Thus, the enhancement of street lighting infrastructure is an important task, leading to minimization of global energy demand and reduction of municipal expenditures on illumination of public places and streets. 2. Advantages of DC link for Street Lighting Infrastructure The rapid development of Solid State Lighting (SSL) technology and decrease of initial cost is described by Haitz’s law [4], who noticed that price/lumen relation is decreasing tenfold per decade, at the same time lumens/package – increasing thirtyfold per decade. Concerning these advantages, it may be assumed that SSL is going to be the replacement technology in lighting sphere in the nearest future. Another assumption can be drawn on base of the fact, that LEDs are DC load, what for street lighting grid could be supplied with DC voltage. In this case configuration of lighting pole could be as it is drawn in Fig. 1. Fig. 1. Configuration of street lighting pole. 235 2012 13th Biennial Baltic Electronics Conference (BEC2012) Tallinn, Estonia, October 3-5, 2012 978-1-4673-2773-2/12/$31.00 ©2012 IEEE