Information about Solar ITU

I N F O R M A T I O N A B O U T P R O J E C T

Project Team

Coordinators:
	Alp Batman
	Deniz Yildirim
Students who have worked on this project (with chronological order):
	Ali Turan	Last year graduation project during Spring 2002 semester. The project has started with him. His main work was the testing of the components and putting everything together for the entire system.

Vital Details of the Project

The aim of this project is to provide outdoor and emergency lighting of Faculty of Electrical and Electronics building using solar panels mounted on the roof.

There are a total of twenty 12V, 55W solar panels where two ten-parallel-connected panels are connected in series to obtain 24VDC. This results in ten parallel connected 24V solar array groups. The DC voltage is carried one floor down to a room where the batteries, inverter and control system are located.

The system initially used eight 12V, 100Ah stationary lead-acid batteries for energy storage during daylight. Four parallel groups of two-series-connected batteries gives a total of 24V, 400Ah energy capacity (9.6kWh). The batteries are directly connected to the output of the solar array through a DC relay switch S1. At that moment there was no charge control unit between the battery and solar panels.

The battery system now employs twelve 2V, 800AH standby lead-acid batteries for energy storage during daylight. All batteries are connected in series to give a total energy capacity of 24V, 800AH (19.2kWH). Batteries are connected to PV panels through a charge controller which prevents batteries from overcharging.

A single-phase inverter converts 24VDC to 220V, 50Hz AC voltage. Three outdoor type low-pressure sodium lights are powered from the AC voltage through two AC relays (switches S2 and S3).

Entire system is controlled by a Programmable Logic Controller (PLC). There are four inputs to the PLC.

12V test panel voltage
Battery voltage
Battery current
Solar panel temperature

Battery voltage and current are directly measured through precision voltage divider resistors and a current shunt, respectively. An additional small 12V 10W solar test panel is also mounted next to the solar arrays where this panel is solely used for determining daylight or night time. The output of this panel is connected to a dummy high-value resistive load - it basically operates at no load. A temperature sensor is glued on the back of one of the solar panels located in the center of the array. These four analog signals are sampled by the PLC every one minute and stored in a data file daily.

Things That Needs to be Done

We are looking for self-motivated, hard-working undergraduate and graduate students who can work on this project for further improvement. Your work may be counted as a last semester graduation project (for undergraduate students). A list of the possible subjects are given below. If you are interested working in any of the followings, please drop us an e-mail at gunes@elk.itu.edu.tr with a brief information about you (a resume would be helpful).

Designing and building a battery charge control unit with maximum power point tracking algorithm.
Designing and building a 1.5kVA, 24VDC/220VAC, 50Hz single-phase true-sine-wave inverter. The inverter must be designed and built in such a way that it has low weight (high frequency operation) and small size.
Replacing three mechanical relays with solid-state switches.
Development of a battery health monitor system.
Alternative energy storage mechanisms for the system (without using batteries)