Illuminated shelf to charge devices through a solar panel

Sergio Arce García Universidad de Oviedo

Gijon, Asturias. sergioarce@gmail.com

Abstract- This project aims to design a system capable of

providing electric power to charge USB devices and illuminate a multipurpose shelf. With a compact and economical design, it is intended for use in public places, like restaurants and pubs.

The equipment consists of a solar panel, one battery module, a device whose function is to obtain the maximum power of the solar panel, a management system of batteries aimed distribute energy from the solar panel to the batteries. Also it includes a LED lighting which is controlled by a driver.

A control circuit with LDR is responsible for determining when it is necessary to activate the LED light because it has poor lighting, for example at night. In this case the light is activated to 10% of its power, and when someone activates a switch the light will be at full power. During the day the light is not working. When the switch is activated is when you can charge devices through the USB port.

Keywords— Illuminated Shelf; Renewable Energy; Energy Efficiency; Solar Panel;Power Electronics; USB Charger.

I. INTRODUCTION This project is developed in the renewable energy

workshop WRE Electronic Department of Gijon Polytechnic School at the University of Oviedo. This project is created as a solution to the current need to charge mobile devices in the most unexpected moments. Conceived as a product to be installed in bars, restaurants or public places in general, it can charge a USB device (mobile phone, Tablet, GPS, etc ...) using a solar energy source.

Fig.1.- Illuminated Shelf

978-1-4799-2911-5/13/$31.00 ©2013 IEEE

II. MODE OF OPERATION The shelf will provide energy for USB ports so, regardless

of the status of the lighting existing in the area, it can charge the device through this port connection (mobile phone, Tablet , GPS, etc ... ) .

It also includes a LED lamp that provides light to the ledge

in that situation in which the lighting is poor. To know when that is the case, it has a LDR light sensor that, through a control unit, allows to switch on the lamp. When there is a situation like this, the lamp is lit at 10 % power until the switch is requested by the order of illumination. For this, there is a button that, when there is poor lighting and the control unit permits through LDR and the switch is on, the light will be at full load for a 10-minute period.

Timing values and percent power may be adjusted for a more customized product as needed.

III. DESCRIPTION The final product of the project will be the design of a shelf

to provide electricity for proper charging of devices that may be supplied by USB, providing LED lighting to the ledge as well. In addition, the photovoltaic solar panel used in this project gives us a lot of flexibility to choose the shape and color of this one because it allows us to customize its shape and finish, adding logos or changing its geometry.

From the solar energy received at the solar panel we

optimize energy generation with a follower of the maximum power point (MPPT) and it delivers energy to a DC bus 24 V. MPPT will verify that the solar panel delivers maximum power to the 24 V bus. Once we have our 24 V voltage we must reduce the value of this voltage to supply energy to the different elements added to the design. In this case, the services provided are: LED lights and a USB charger.

We will use a power supply (LM7805) capable of reducing the voltage from 24 to 5 volts. To store energy, modules will use BMS (Battery Management System) based on bidirectional converters which distribute the energy properly in a 3-battery lithium battery module.

Fig. 2. -Block diagram.

IV. MODULES

A. Solar Panel Module The shelf has a solar panel Soliker brand installed, exact

model UNISOL PV-43, which provides good performance under temperature and a good use of diffuse solar radiation, among other features.

The manufacturer provides that, for a 1000w/m2 radiation and the measures of our board, 415mm x 250mm x 6.5 mm, maximum power point MPP provides 5.8 W.

For example, for a period of 10h of radiation, this solar panel generates 58Wh, sufficient energy for the energy we need to have in this product.

It is important to ensure that the solar panel works at an

optimum performance point. For this, it is vital to seek this point and make it the most used working area.

The optimum operating point is not easy to get. Depending

on the solar radiation received, as well as the temperature and the load of the system, the operating point of the plate will be different, being necessary to implement a system that ensures the solar panel works at the optimum point as much as possible. The amount of power that can be drawn from a photovoltaic system in turn also depends on the voltage that the system will use.

This control system we are talking about is the follower of

the maximum power point (MPPT Maximum Power Point Tracking ) .

B. USB Charguer Module We will use a power supply (LM7805) capable of reducing

the voltage from 24 to 5 volts. The operation, from the point of view outside the

integrated, is simple. The integrated voltage is given any tension between certain values; for example, for a maximum input value of 7805, the manufacturer specifies a maximum input voltage of 35V, and he is responsible for ensuring that their output is 5V.

C. LED Module LED lighting block consists of 4 LEDS 0.25 W each,

which provides enough amount of light. These LEDs will work through a ZXLD1350 driver, manufactured by ZETEX.

D. BMS Battery Module In this project we decided to use Li-ion batteries due to the

relative autonomy/volume. It will be placed in 3-battery module, installing the corresponding BMS to ensure proper system operation. The batteries used in this project are Ultrafire BRC 18650.

The main purpose of BMS (Battery Management System) is to ensure that the DC voltage bus has always 24V. If the solar panels can’t provide sufficient tension, BMS is responsible for extracting energy from the batteries, in the amount required at every moment. And, when the DC bus has an excess of energy, BMS stores excess energy in batteries.

V. CONCLUSIONS The development of this project in the workshop WRE has

served the author to enter the field of renewable energies, as well as to learn and develop the main components used in this type of projects. The final design of the project has not been closed, and it would be possible to add new features as needs are requested.

ACKNOWLEDGMENT Acknowledge the support of the Engineering Polytechnic

School of Gijon- Asturias- Spain (EPI-Gijon) with the Workroom on Renewable Energy (WRE).

Acknowledge the support of the professors who manage the Workroom on Renewable Energy (WRE) in working with this project and its major concern about the development of it.

REFERENCES

• WRE OpenCourseWare http://workrooms.dieecs.com/wre/WRE-OCW • Vincenzo Balzani, Nicola Armaroli. “Energy for a Sstainable World:

From te Oil Age to a Sun-Powered Future”. • Ned Mohan, Tore M. Undeland, William P. Robbins. “Power

Electronics: Converters, Applications, and Design”. • Muhammad H. Rashid. “Power Electronics Handbook, Third edition”. • Ned Mohan. “First Course on Power Electronics”. • Ned Mohan. “First Course on Power Sustems”. • Soliker, http://www.soliker.com/ • Ultrafire http://www.ultrafire.net/.