In this first post I presented the Prosol Elec project that the Tunisian government introduced in 2009 to promote photovoltaic electricity generation, in today’s post I will review and criticise the technical requirements of eligible installations.
According to the guidelines defined by the ANME, the following specifications must be met:
- CEI-61215: mono- and poly- crystalline PV modules.
- CEI-61646: thin film PV modules.
- Modules must be tested and certified by an accredited lab.
- All modules used to make the PV array must be identical with a tolerance of +/- 5% of nominal peak power.
- Moules must have a junction box with a minimum weatherproof rating of IP54, and bypass diodes.
- Minimum product warranty for the PV modules must be of 5 years. Performance guarantee have to be at least 90% for the first 10 years and 80% after 25 years.
- Installers will have to properly choose the PV array installation location, with the client’s agreement. This location must have enough available area, facing south as much as possible, and without obstacles that may create a shadow on the modules in any season. Furthermore, this location will have to support the modules weight. Optimal inclination is 30° to he horizontal plane. Nevertheless, installers are free to choose other inclination angles to privilege yield in some seasons, with the client’s agreement.
- Rows of PV modules should not shade each other.
- When installing the mounting systems, installers must make sure that the roof remain waterproof (no drilling) without compromising the stability of the structure.
- Mounting systems must resist without damage to strong winds and to corrosion.
And here is my criticism to every one of these points below:
- This is fine and pretty mainstream, almost all modules on the market have it, otherwise no chance to be sold in the most important PV markets in EU.
- Same as above.
- The text does not make any reference to what kind of accreditation the testing lab must have (does it have to be accredited by a tunisian ministry, or what exactly).
- This is non-sense, because many inverters have now more than one MPP tracker and can have two totally different PV arrays connected to their separate inputs. A proper wording would be to insist on having identical modules on each string.
- Many new thin film modules do not have bypass diodes and that is totally fine. Just as an example, Schott Solar makes the amorphous silicon-based ASI series and they are excellent modules by any mean, with 30 years linear performance warranty, and they don’t incorporate any bypass diodes. For the curious readers, this is an interesting read that explains why (in a nutshell because cells in a thin film module are connected in parallel and are less vulnerable to shading).
- This is fine even though market standards are now higher than these requirements.
- There is enough room for interpretation in this point to make me uncomfortable about it: I think that words “properly” and “enough” do not have a place in a technical specification document. Requirements must be defined in terms of measurable figures and in the corresponding units.
- The same comment applies, there should be a defined safety margin with a tolerance for this requirement.
- The same comment applies again.
- This point really makes me doubt about the seriousness of such a document. The forces that mounting systems are usually defined using many factors, including the strongest measured wind velocity in the region in the last 50 years and other meteorologic data. In Germany for example there is the DIN 1055 and in every other EU country there is an equivalent standard. What is a strong wind? and how to ensure that the structure will resist corrosion without requiring testing certificates or defined materials? do we just believe the seller’s word? A lot of improvement must be done on this point, including making a national norm for light construction structures.
Already many flaws found in this law and this is only the beginning. I am quite impressed to find such flaws in a law that was drafted with the support of the GIZ and the italian ministry for the environment.
In the next couple of posts I will examine the requirements for DC cables, solar inverters and AC cabling, then I will re-evaluate the Prosol Elec project as a whole, as well as the national energy policy.