Ljubomir Majdandzic, Croatian Professional Society for Solar Energy, J. Kavanjina 14,
HR-10090 Zagreb, Croatia, Phone. ++38 5 1/38 79 122, Fax: ++38 5 1/38 88 918,

E-Mail: hsuse@hsuse. hr

Mario Peric, Brodarski Institute, Ave. V. Holjevca 20, HR-10020 Zagreb, Croatia,

E-Mail: peric@hrbi. hr

Zdeslav Matic, Hrvoje Pozar Energy Institute, Savska cesta 163, HR-10001 Zagreb,
Croatia, E-Mail: zmatic@eihp. hr

Abstract

This paper presents a project named "Solar roof Spansko-Zagreb” with data for half a year of operation. This is the first grid-connected project in the Republic of Croatia. The project comprises of solar collectors providing thermal energy, and of PV modules providing electricity. This building does not emit carbon dioxide into the environment, a major contributor of global warming. The concept shows that passive and active use of solar energy can meet power needs of a building, without disrupting the comfort of habitation. The building reduces consumption of fossil fuels thus reducing the emission of harmful substances into the environment. This project represents an initiative for increased use of solar energy, especially on islands in coastal region and hinterland of Croatia.

1. Introduction

The project "Solar roof Spansko-Zagreb" for supply of thermal and electricity energy by solar energy is shown in Figure 1. A solar collector with 10 m2 surface and a photovoltaic array with rated power of 7,14 kW are mounted on the roof of the house. A 750 liter tank is used for storage of thermal energy for heating and hot water supply. City gas is used for backup when solar energy is not able to meet the demands for heating and domestic water preparation. The electricity produced in photovoltaic modules is primary used for loads in the house with surplus transferred to the public network. When modules can not produce enough electricity, the power supply is supplemented from the utility. The PV generator with rated power of 7,14 kW consists of 42 identical modules of 170 Wp, divided in three groups. Cables coming from module strings are introduced to a distribution board. In the board each module group is connected to the inverter. The board is equipped with surge arresters and micro circuit breakers. Both frequency and voltage are controlled and synchronized to the local electric utility. There are three converters with rated power of 3000 VA.

This photovoltaic system connected in parallel to the distribution network is specified for both electricity supply of the family house and distributive electricity production. Excess electricity is transmitted to the network. Around the middle of the day the system production is the highest and reduces the load of the network during the peak. The system is designed for automatic operation with about 30 sensors measuring over 150 different parameters.