In many circumstances, panels can be used to directly power electronics such as a ventilation fan or a pond fountain without requiring batteries. (In a similar way, small panels can also be directly connected to 12V batteries such as car batteries to trickle charge them - see battery top-up).
When the load can tollerate an intermittent or fluctuating supply, a voltage regulator is not necessary. In such cases, the power of the panel should be matched with the requirements of the electronics being powered (e.g. the 10W AKT-10-M panel would be suitable for powering a pond fountain that runs on up to 0.75A at up to 17V).