The objective of this project is to develop design criteria so that PV engineers can improve the designs of PV battery chargers, to overcome problems which are currently begin experienced. As PV applications increase, it is essential that the charger is designed to improve the performance and prolong the lifetime of the battery with a minimum amount of maintenance.
Two types of battery monitoring systems have been developed in the laboratory. One is used to continuously monitor the battery (cell by cell) and the second is a manual system which is used by maintenance personnel to test individual battery cells. The innovation is the method of measurement and the algorithms and software calculations used to assess the battery state of health.
Research has been carried out to help plant managers identify and overcome the battery problems encountered in photovoltaic systems. Data has been collected from battery experiments and from photovoltaic systems and the results have been presented in a format which can be used by plant managers. A photovoltaic battery handbook has been produced along with operations and maintenance guidelines.
Prototypes for battery monitoring systems have also been designed, developed and tested.
The energy produced by a PV array varies in a daily and a seasonal cycle due to changing irradiation level. In systems which use electro-chemical batteries to store energy, it is necessary to control this energy to regulate the charging profile of battery. The charge regulators (battery chargers) which are used today are based on specifications from battery manufacturers and from experiences with other battery applications (e.g. stand-by batteries, traction batteries etc.).
The work program will be carried out in four main phases :
1) Review the status of charger technology : This review will involve the compilation of a database of chargers in the market place, a review of the charge criteria presently employed and a review of operation of existing chargers in PV systems.
2) Compile requirements specification for advanced charger : Following the Phase 1, review of charger technology a detailed specification of the requirements and functions of the advanced charger will be compiled. This will done in cooperation with battery manufacturers, PV researchers and PV designers.
3) Develop and test a prototype advanced charger : The prototype as defined in the requirements specification will be tested in the laboratory and in PV systems.
4) Provide recommendations for improvements to existing chargers. Following a period of monitoring and evaluation of the advanced charger operation recommendations for charger improvements will be circulated.
Through this work the concepts of improved charge control in PV systems will be developed and demonstrated. The involvement of the battery manufacturers and the PV industry will ensure that the benefits of advanced charge control reach the PV users.