Photovoltaic: Efficiency and direction of development

I started studying renewable energies in 2001. I was already sure at that time that Photovoltaic technology would become a key player in the race for renewable energy sources. Using the sunlight and technology that does not require complicated mechanical elements or difficult process control during energy production is fascinating. The ability to create small installations everywhere with no impact on the climate is another strong point in the argument for Photovoltaic. More than 10 years have passed since I began to study renewable energies, yet there is still a long way to go.

We are not satisfied with the cost situation of Photovoltaic and its efficiency. To earn back the energy, which is necessary to produce a mono crystal silicon solar panel, we need 8 to 10 years. The panel has an estimated lifespan of 20 years. This, in my opinion, is still not a satisfying ratio. The energy usage for production is much lower for thin film technology. We can calculate that the thin film solar panel will earn back its production energy in 3 to 4 years.  However, there still lies the problem that  thin film technology cannot achieving a reliable lifespan of 20 years.

Let us look now to the efficiency of solar panels. The biggest impact of efficiency is caused by the materials itself. The following picture shows the maximum possible efficiency of solar cells by different materials.





Using silicon as the material, solar cells cannot be more efficient than 23%. Today’s silicon solar panels are claiming an efficiency of 12% to 15%. If I put now the 23% to 100%, because there is no influence by technology possible, we achieve efficiency levels from 55% to 75% for silicon solar panels. Looking to these figures I would estimate that there is still a possible efficiency increase of 10% to 15%. Still, we face the limits of the materials and their physical conditions. The materials used for thin film technology have not proven much better than silicon under the same conditions. Theoretically it is possible to make a multilayer thin film out of different materials, which presents the possibility of multi-junction absorption of sun energy. This could bring the efficiency of solar cells to a higher level.

Out of the above mentioned issues, I propose and expect the following further development:

Silicon cell efficiency can be improved by nearly 10%. The possible cost reductions should be pursued. The technology to produce reliable solar panels with silicon cells is mature; near and midterm future silicon cells will play the dominating role in the Photovoltaic market.

Thin film technology for solar cells is, theoretically, a much more efficient and low-cost possibility. But we have to make thin film solar cells much more durable, otherwise they will be neither efficient nor cost-effective in the long-term. My estimation is that this development needs at least another 5 years to mature. Companies and research institutes should assign resources for this direction to participate in the developments and to bring Photovoltaic technology into the mainstream as soon as possible in the “pool position.”

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