Solar Developments in the OSC Neighborhood
Like other parts of the planet there are significant developments in solar energy generation in Sri Lanka. The costs of photovoltaic (PV) panels have come down and net metering allows small operators to export their power to the grid built and maintained by the Ceylon Electricity Board. After many years of reading about the solar revolution it has been thrilling to have a colleague install a system at her house. Encouraged by these developments, OSC’s DP Environmental Systems and Societies (ES&S) students are investigating the basics of PV-generated energy. It has given me a chance to brush up on power and energy concepts as are applicable when talking about the generation of renewable energy.
My personal interest in energy goes back to my father Merrick Lockwood who has been working with alternative energy projects since the late 1970s. His significant work was on a biomass-fueled Stirling cycle engine that produced power to run a rice mill. You can about the joys and tribulations of his work in Bangladesh in How I Built a 5HP Stirling Engine (it is an intriguing account narrating the Rice Husk Energy project though the title was not Merrick’s choice). Stirling engines were a major focus point but Merrick has always been interested in an array of conventional and non-conventional energy technologies. I have strong childhood memories of PV cells, batteries, meters and literature on renewable energy in the wonderful clutter of his office and workshop. Earlier this year my alma mater KIS installed a 2 kw set of panels though the tireless work of Class of 1952 alum Dr. Clarence Maloney. His efforts helped get me thinking about solar energy as a viable option.
Sri Lanka sits in an enviable location to tap into renewable energy. Because it is so close to the equator (6°-9.5° N) it is bathed in insolation (solar irradiance) throughout the year. Sri Lanka is blessed with high rainfall in its “wet zone” and here it taps into large and medium-sized hydroelectric schemes which generate about half of all the electricity use in a year. Sri Lanka’s coastal areas offer great potential for wind power generation (something being explored in the Kalpitiya region). Biomass fuel provides for much of the country’s cooking needs in rural areas and if managed correctly can be a sustainable energy source. At the moment Sri Lanka’s electricity demand is growing and it gets significant power (up to 40-45%) from thermal plants burning heavy oil and coal. The chart below shows the source of electricity on 16th November 2015. Because of the high rainfall in the catchment areas there is optimal hydroelectric production (68% of the total).
The catalysis for my current interest interest in solar energy at OSC was my colleague’s Chamilla Ratnaweera decision to install an array of PV panels on her rooftop in July this year. She and her husband have sixteen 0.46 m2 panels for a total of 23.36 m2. They have a net-metering arrangement, which means the power that they generate goes straight into the grid and runs their meter backwards (“exporting” units on their bill). When they draw power (it is mostly at night and on weekends) the system takes electricity from the grid. Not having batteries and having to deal with the storage of solar generated electricity simplifies the process in net metering. It assumes, of course, that there is functioning electricity grid.
In September Chamilla’s panels produced an average of 14.3 kWh of solar energy every day (see graph below) and they have not paid an electric bill for the last three months! What is even more remarkable is that have also purchased a Nissan Leaf eclectic car and are able to charge the vehicle and meet their electrical energy requirements with their panels! Chamilla has access to daily, monthly and yearly data on solar energy generated (in kWh). There are several companies offering schemes and they purchased their set up through Solar Edge (marketed here by JLanka Technologies). According to their company literature a similar set with installation costs roughly LKR 1.1 million (US$ 7,700). Our class has been checking on her daily power generation every day for the last two weeks.
As a part of this study I visited the Sri Lanka Department of Meteorology on November 6th. On this initial trip I had several interesting discussions with the meteorologists who run operations and I was also able to purchase solar radiance and rainfall data. The graphs below chart solar radiance (in MJ/m2/day) against the solar energy generated by Chamilla’s panels (in kWh/day). Other than the days where there was maintenance on the panels there is a clear pattern between radiance and solar energy generated as one would expect.
To better understand solar energy the class tested a small 31 x 37 cm 15w panel that the Physics class purchased last year. Will Duncan, the Head of Science, gave me a primer and demonstration on how to rig up the voltage and current meters and make calculations on energy generated by the panel. We are using Vernier’s Labquest2 devices and these are versatile data loggers that allow students to gather raw data from a variety of probes. This year we purchased the pyranometer probe, which measures irradiance (in w/m2) and allows you to then calculate the efficiency of solar panels. I ran trials with the Labquest simultaneously taking in data from three probes (voltage, current and irradiance). The raw data is then imported into Loggerpro where power and efficiency is graphed and analyzed.
Weather is obviously a major factor in producing solar energy. We have just experienced unseasonably wet months in September and October. In fact his last Sunday- an overcast, gloomy day that experienced rainfall for much of the day- Chamilla’s panels generated 6.89 kWh of solar energy! That is lower than the 14.34 kWh September average but still significant. We have not yet done a full cost benefit analysis of the panels but it is quite clear that they pay for themselves quickly. If the electricity bill was roughly LKR 25,000 a month, the system would pay for itself in under four years. The company, like many here in Sri Lanka, is advertising the system to have a 25 year lifespan. If you are a house owner or run a large institution, such as a school like OSC, investing in a PV systems makes both sense for the climate and your wallet.
In the next post I’ll explore rainfall data in these last few months in order look at patterns and changes from past years.
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