To rehydrate (reactivate) silica gel for use in a solar plant, heat the gel in a convection oven at 110-120°C,

 To rehydrate (reactivate) silica gel for use in a solar plant, heat the gel in a convection oven at 110-120°C, periodically shaking the container for even heating, until the indicator changes color (e.g., pink to blue) or until a consistent weight is achieved, indicating maximum moisture release. Afterward, allow the gel to cool to room temperature and use it immediately or store it in a tightly sealed container to maintain its dry state. 

1. Preparation 

Check the color:

Color-indicating silica gel changes color as it absorbs moisture, making it easy to see when it's exhausted.

Use an appropriate container:

Place the silica gel in a convection oven-safe container or on a baking tray, ensuring proper air circulation around the gel.

Consider measuring weight:

You can weigh the silica gel before heating and periodically during the process to track moisture loss, which is a definitive indicator of full regeneration.

2. Heating Process

Set the oven temperature: Preheat the oven to 110-120°C (230-250°F). 

Heat the gel: Place the container with the silica gel in the preheated oven. 

Promote even heating: After some time, remove the container and gently mix or shake the beads to expose new surfaces to the heat. 

Continue heating: Repeat the heating and mixing steps until the indicator gel changes back to its original color (e.g., from pink to blue). If tracking weight, continue heating until the weight no longer decreases, indicating that all absorbed moisture has been released. This process can take 1 to 2 hours or more, depending on the amount of moisture and the oven. 

3. Post-Heating

Cooling:

Once fully dried, turn off the oven and allow the silica gel to cool completely to room temperature before handling. 

Storage and Use:

Use the rehydrated silica gel immediately, or transfer it into a tightly sealed container to prevent it from absorbing moisture from the air. 

Important Considerations

Solar application: In a solar system, the silica gel is often used to adsorb moisture from the air and is then regenerated using solar heat. 

Frequency: This regeneration procedure may need to be repeated periodically, as over time the pores in the silica gel can collapse, reducing its effectiveness. 

Safety: Be careful when handling hot containers from the oven.