The products we have so far imported are the SAMIL Inverters Solar River up to 5kW, Solar Lake of 10kW and KINVE Mono-crystalline 250Wp panels. These have been selected to suit Sri Lankan environment and local usage patterns.
INVERTERS
Inverters are of different types such as:
- ‘Grid tied’ inverter – where the solar system is connected directly to the main power grid without the need for expensive & high maintenance storage batteries.
- ‘Off grid or stand alone’ inverter – where solar power generated is stored in batteries and inverted to a.c.
- Grid-tied Inverters are also differentiated according to the size as Micro inverters and String inverters
SOLAR PANELS
Solar panels are of different types – mono-crystalline, polycrystalline and thin film.
Mono crystalline are :
Of highest efficiency (15 to 20%), whilst polycrystalline (13 to 15%) & thin films (13 to 14%) Better space-efficient and hence needs lesser space/weight than the poly panels. Perform better than similarly rated polycrystalline solar panels at low-light conditions.
More durable hence easy for solar panel manufacturers to give a 25-year warranty. More efficient in hot weather. Efficiency is lowered as temperature goes up. Polycrystalline panels degrade much faster and steeper.
More aesthetically pleasing since they have a more uniform look compared to the speckled blue colour of polycrystalline silicon
MPPT
In order to harness the maximum amount of energy in various light conditions, the systems use a unit called MPPT, short form for Maximum Power Point Tracker. The majority of string invertors today have built in multiple MPPTs to take in multiple strings of panels with wide voltage range making them suitable for varying light conditions.
Only a few inverters however do not have built in MPPTs but are connected to outdoor MPPTs installed under each solar panel. This can lead to multiple points of failure, loss of efficiency of the system due to high temperatures on the roof as these are generally rated for temperate (25°C) climates. Mean time between failures (MTBF) for these external MPPT units had not been proven so far and will require removal and reinstallation of solar panels to replace faulty MPPTs. External MPPTs will also increase the total solar system cost but may marginally increase the overall efficiency, if at all, of the solar PV system by less than 10%.
The most common reason touted for external MPPTs is to avoid impact of shadows on solar panels that can affect production efficiency. However tropical countries like Sri Lanka lying near the Equator get direct overhead sunlight throughout the year. As such 80% of solar energy generation is within 2 hours immediately before and after the high noon when the sun is right above them. The effect of any chance of shadows on the roof during this period is minimal and can be fully avoided by proper designing of the solar panel layout. As such the benefit of external MPPTs are not generally applicable in Sri Lankan environments.