In the era of solar revolution taking place, solar roofs are mushrooming round the globe. In Sri Lanka also, solar roofs are becoming popular and the aim of this article is to provide some real data to help the Sri Lankan community to understand the value of these projects. This in turn will accelerate the take up of solar roofs in the country by more families learning the benefits of solar roofs. Our first article focussed on the performance of comparatively large solar roof of 20 kW. This article, J.A.P. Bodhika and I. M. Dharmadasa summarise the performance of solar roofs varying between 5 kW to 50 kW capacity.
Two photographs of typical small solar roofs in Matara, Sri Lanka are shown below, and data obtained from 12 systems are shown in the Table below.
|Power Capacity (kW)||Units (kWh) produced per annum||Annual Income (LKR)||Cost (LKR) of the system
|Simple Pay Back Period
The selected solar roofs for this article are from different parts of the country, and they are arranged according to the production capacity of the systems in kW. The power outputs produced by the solar roofs depend on several external and internal factors. The direction of the roof, angle installed, shading effects and climatic conditions of the area are some of the external factors. The internal factors like properties of components used are also contribute to the outputs depending on the manufacturer.
We have also calculated the annual income from each system using the current “Net Plus” scheme with a payment of Rs 22.00 per kWh unit, during the first seven years of installation. The cost of the system column indicates that it is financially beneficial to install larger systems. In all cases, the simple payback period is in the range 3.42 – 5.70 years. Some people may immediately calculate the interest they could earn if the initial capital is deposited in a Bank. For example, 8 Lakhs spent on a 5 kW solar roof produces on average ~Rs 160,000 per annum (please see the last three systems in the Table). At least 20% annual interest rate is needed from a Bank to get the same annual income. This way of thinking may come from people who only consider the direct monetary value of everything. However, sensible, and considerate Sri Lankan population with over 96% literacy rate, need to think beyond this, and consider other numerous social benefits to the mankind from these systems.
Imagine the production of clean energy using freely available indigenous sunlight, without polluting the atmosphere, and reducing coal burning in the country. Corresponding health related benefits are numerous. These systems cut down carbon dioxide emissions to the atmosphere and reduce expenditure for country’s fossil fuel import. These solar roofs also contribute towards reduction of global warming and mitigation of climate change effects.
The solar roofs provide free electricity after the payback period as an additional income, mainly during the retirement period of the bread winner of the family. The world is rapidly moving towards replacing the cars run on combustion engines, by electric cars. Towards this aim, UK government has already introduced policies to stop manufacturing of petrol and diesel-ran vehicles after 2030. The solar roofs will provide opportunity to charge future electric cars at home without any extra expenditure.
Future energy supply for Sri Lanka should come from a clean technology mix, rather than polluting (coal, oil, and gas) or un-safe and dangerous (nuclear) energy technologies. The most relevant energy mix for Sri Lanka should be Hydro, Solar, Wind, Biomass and imported fossil fuel. Sri Lanka should work to accelerate and expand the use of first four technologies, while allowing the fifth one to be gradually reduced. However, it is sad and surprising to see the decisions taken by authorities to expand coal power plants in the country. It is high time the Sri Lankan population raise their voice and do their obligations by installing more and more solar roofs round the country. The Ceylon electricity board (CEB) should continuously improve the national grid incorporating solar and wind energy, moving towards achieving a smart grid and carbon neutral economy. Many countries do this successfully at present, and CEB should acquire this new knowledge by training their young electrical engineers.
It is also an alarming news we hear every day about deforestation in Sri Lanka disturbing the eco system and aggravating elephant-human conflict. Solar panels are in fact “artificial leaves”; these convert sunlight into energy, very similar to our natural leaves (trees) functioning for our existence. Leaves on trees produce our food (energy) through photosynthesis, absorbing carbon dioxide from the atmosphere and releasing oxygen we breath to the atmosphere for our survival. For this reason, trees are known as “Lungs of our Planet” since their action is very similar to the function of our lungs. Our lungs absorb carbon dioxide from the blood stream and give oxygen to the blood flow, for our body to function.
In addition, trees provide many other functions like reducing soil erosion, naturally fertilising our soil, avoiding land-slides, managing water & protecting from flash floods and providing that natural coolness for our comfort. Cutting trees (destroying carbon dioxide absorbers from the atmosphere) and burning coal (pumping carbon dioxide and particulates into the atmosphere) are the enormous damage people do to our environment. Have Sri Lankans noted the gradual desertification of the north part of Sri Lanka? The sands and Palmira trees are the first signs of slow desertification and we need to wake up to realise these dangers. As a precaution for these dangers, we all should save our forests, grow trees wherever we live and install “artificial leaves or solar panels” on our freely available roof tops. In Sri Lanka, we also should take care not to cover our fertile lands with solar panels in energy production.
Authors of the Article
- A.P. Bodhika: Senior Lecturer, Department of Physics, Ruhuna University, Sri Lanka (firstname.lastname@example.org).
- M. Dharmadasa: Senior Staff Grade Professor, solar energy researcher, and promoter of clean energy applications, Dept. of Engineering and Mathematics, Sheffield Hallam University, United Kingdom (Dharme@shu.ac.uk).