Jochen Benz, Ursula Wittstadt, Beatrice Hacker

Fraunhofer Institute for Solar Energy Systems ISE, Freiburg, Germany

Fernando Isorna, INTA, Madrid, Spain;

Antonio M. Chaparro, Ciemat, Madrid, Spain Loreto Daza, Ciemat & CSIC Madrid, Spain

Photovoltatic systems are widely used in autonomous power supply systems. One application that has become more important during the last years is the power supply of telecommunication equipment. An availability of 100% over the whole year makes hybrid systems necessary, especially in regions with distinct seasonal variations of insolation. A PV-hybrid system with electrolyser and fuel cell has been developed within a joint European consortium in the project FIRST (Fuel Cell Innovative Remote System for Telecom). Surplus energy in summer is stored in form of hydrogen to be used up by a fuel cell during periods of low insolation in winter. The system supplies the power for a telecommunication equipment. Operating experience from a test site will be reported.

Set-up of the test system

The autonomous power system has been designed to supply a consumer with 100-300 W (power depending on channel usage, average: 160 W) power over the whole year. The consumer is a trunked radio base station which gives wirebound telephony services to locally attached users, e. g. in remote areas or for developing countries where no grid infrastructure is available.

Thin film CuInSe2 (CIS) type PV modules (Wurth Solar, Germany) with a power of 1.4 kWpeak are connected to a lead acid battery of around 19 kWh. It allows for the load to be supplied autonomously for 5 days. .The battery serves therefore as a short term energy storage. A charge controller with maximum power point tracking (Wurth, Germany) puts the energy from the solar panels into the battery A PEM electrolyser (Fraunhofer ISE, Germany) with a maximum power of 1 kWei produces hydrogen at a pressure of 30 bar using the surplus energy during high insolation. The produced gas is fed into a gas purification unit and subsequently stored in metal hydride tanks (CSIC, Spain) with a volume of 70 Nm3 of hydrogen. During longer periods of low insolation (e. g winter), hydrogen is fed to a PEM fuel cell (Nuvera, Italy) which supplies the necessary power if the state-of-charge of the battery is low. An energy

management system (EMS) (Fraunhofer ISE, Germany) which will be described in more detail below has been developed on basis of a microcontroller. The system (see Figure 1) has been set up inside a container at the site of Ciemat (Madrid, Spain). A flow diagram of the system is shown in Figure 2. Permanent data acquisition is done by a data logger. Some parameters are acquired from the EMS’ internal quantities.