1. Lightweight encapsulation
The weight of one complete PV panel should be about 1kg; the weight of the encapsulation should not exceed 100g. Because of weight saving I want to examine if a simple encapsulation technique, would be sufficient. The corrosion protection requirements are not as high as PV panels that are used on house roofs, with 30 year lifetime. A lifetime of 10 years would be fine. The solar bike PV panel can be kept dry if not used and will not often be exposed to rain.
Here I will test different encapsulation materials on properties such as corrosion protection, weight and transmission loss. I have done the measurements with my solar cell curve tracer.
2. Bare solar cells exposed to the elements
I wondered what would happen when a solar cell is exposed outside in the rain without any protection.
After some weeks already I saw a huge degradation of the performance. The result is not surprising, protection can’t be neglected. I will divide solar cell corrosion in three types:
- Metallization corrosion, increases in RS. This is clearly visible.
- Light sensitive surface corrosion.
- Antireflection coating deterioration.
Here are some graphs of a corroded solar cell:
3. Plastic laminating sheets
In my garden I have a painting which consists of a laminated poster. The poster is made of ordinary paper and is still in good condition while it is exposed to the elements for many years. The laminating sheet must also be completely water and moisture tight. I wonder if such a material would also be suitable for lightweight mobile PV panels.
Laminating sheets can be made of different materials such as PVC, PET, EVA and polypropylene. There are also matte sheets. The thickness is commonly about 0.075mm. The lifetime outside can be 7 years. Due to the small thickness it is light and it could also have a low transmission loss. The use of this material for solar cell encapsulation could be investigated further.
4. EVA film test
EVA film (Ethylene-vinyl acetate) is one of the most used encapsulation materials. However it is heavy, 500g/m2. Also, EVA has relatively high moisture diffusivity. The transmission loss of EVA, measured with the solar cell curve tracer and the slide projector, is 6%. Note that this is not a measurement under laboratory conditions and only used for comparison.
5. Anti-Reflection Coatings
Much profit can be taken from anti-reflection coating, see pveducation.