Function and Use of Storage

Storage in Photovoltaic Systems

Storage plays a crucial role in photovoltaic (PV) systems by increasing the amount of time the system can power a load. Batteries are the most common type of storage used in PV systems. However, in certain applications, other storage components can also be utilized.

Importance of Storage in PV Systems

In standalone PV systems, storage is essential to power loads at night and during cloudy weather. The amount of storage required depends on the location’s weather patterns, with cloudier areas necessitating more storage. Additionally, storage can buffer the system against periods of low insolation, enhancing reliability.

Storage in Grid-Connected Systems

In grid-connected systems, storage is typically not needed as the grid provides electricity when PV power is unavailable. However, storage can still be included to increase the value of PV-generated electricity, especially for peak shifting to match peak load times.

Functions of Batteries in PV Systems

Batteries in PV systems serve multiple functions beyond storage:

• Storage: Storing energy for later use when the generating source is unavailable.
• Start-up current: Providing higher currents for loads with high start-up current draw.
• Power conditioning: Acting as power conditioning devices in various applications.

Characteristics of Batteries in PV Systems

Batteries in PV systems must exhibit reliability, low maintenance, long lifetime, and cost-effectiveness. Specific considerations include efficiency, capacity and lifetime under deep cycling, costs, and maintenance requirements.

Electrolysis of Water in Batteries

In batteries with water-based electrolytes (e.g., lead-acid batteries), electrolysis of water can occur during charging. This process can lead to water loss, hydrogen gas evolution, and safety hazards. However, gassing can also have beneficial effects such as electrolyte mixing in lead-acid batteries.

Uses of Batteries in PV Systems

Beyond providing power during sunlight absence, batteries in PV systems have various uses, including load-matching, start-up current provision, and peak shifting in grid-connected systems.