Before I describe the above topic, I wish to draw the attention of the readers to Solar Water Heater Systems usage in Sri Lanka. About 10 years ago, very few households used solar water Heaters for hot water needs, because they were relatively high in price at that time (1) due to the use of blackened copper tubes in fabrication of Solar Water Heaters, (2). Electric Showers or Hot Water Geysers were relatively low in price and (3) electricity tariff was low during that period.

But the Solar water heaters have come down in price or remain at the same prices after ten years due to the invention of evacuated tube technology which is more efficient in harnessing solar heat. Coupled with the rise in electricity tariff and increase in Cost of living more and more households have given up Electric Geysers or Electric showers and switched on to new technology Solar Water Heaters. The advantage of the evacuated tube technology solar heat converter is it can achieve temperatures above 70 deg. Celsius on sunny days and on rainy days it produces hot water at 40 deg. Celsius. This is an Eco friendly scheme which reduces imported fuel bills to the country in water heating.

The story is same for the Solar PV Systems. With the discovery of new Solar (PV) conversion materials and new manufacturing technologies, (1) the efficiency of solar panels have increased. (2) The capture areas of the panels have become smaller and thereby manufacturing costs have come down. Coupled with this, the prices of the Inverters which covert DC power generated in Solar Panel to A.C. also have come down in prices over the last ten years and expected to come down further in future.

Since my topic has a strong connection to solar inverters, I wish to elaborate that further. There are two types of DC/AC Inverters: (1) String Inverter, (2) Micro Inverter (latest development).

In case of String Inverters several Solar Panels are connected in series to provide input voltage around 180~200 DC Volts to the String Inverter. Separate isolated DC wiring is necessary in this case from roof top where the panels are mounted to the place where the Inverter is fixed. As a result the initial investment cost and the installation cost of a string inverter solar panel system is therefore high. People who can afford onetime payment or bank loan schemes can only install and use a system like this.

On the other hand over the years the Micro Inverter technology has developed to an advance stage where the physical dimensions have come down to a such level that it can be fitted under the frame of each solar module. Their conversion efficiencies have gone up above 96%, the manufacturers offer 15 to 20 years extended warranty as they have become more reliable. Further they can be manufactured to meet grid conditions of various regions. In an Inverter mounted Solar module, 24~36 Volts DC generated by each solar panel is immediately converted to AC under the panel itself. Several such panels can be connected in parallel to increase the capacity as and when required. As a result micro Inverter mounted solar panels are now available in the market which can generate 30kWh per month. The initial cost is about US$ 400 for a high grade solar module coupled with a high grade Micro Inverter.

In case of bulk purchase this price will automatically come down. Presently solar module prices are at 8~6 US cents per watt with 25 years manufacturer’s warranty. The price will further comes down within the next few years.

Now will look at the technical advantages of Micro Inverter mounted solar module system over the String Inverter connected solar modules.

Now look at the grid electricity generation in Sri Lanka, 70% of the present day energy demand is generated by Oil and Coal Fired Thermal Plants, 23% is generated by Major Hydro Plants, balance 7% by new renewable energy sources such as wind, mini hydro, Solar PV and bio mass etc. Hydro Generation depends on the rainfall intensity of South West and North East monsoons in Sri Lanka. But the rainfall levels to catchment areas cannot be predicted. As a result the major portion of the daily electricity demand is met by thermal power generation except in very wet years.

On the other hand, petroleum and coal are dwindling resources and are subjected to price escalation due to high global demand. Therefore it is inevitable that Sri Lankan consumer will have to bear a high price for electricity and the costs of other consumer goods due to global escalation of petroleum and coal prices.