Will solar energy be the ultimate solution?

by Patali CHAMPIKA RANAWAKA

When I was working as a consultant to the Department of Mathematics of the Faculty of Engineering at the Open University of Sri Lanka, I was assigned many researches by the head of our Department, Professor Arjuna Zoysa, recognized in University circles as a very kind, honest and intelligent academic. One such research assigned was to evaluate the true or total productivity of systems. Generally, the productivity is defined as an out put - input ratio, as if to find out the number of energy units or man hours required to produce a certain quantity of goods and services etc. In this calculation we naturally ignore the man hours or energy units which are already included in the machinery and other structures.

The efficiency of a car is very often gauged by its fuel efficiency and to ascertain it we take note of the litres of fuel it needs for a running kilometre or mile. In calculating this we do not take in to account the units of fuel it needs in its manufacture. Although one can argue that the monetary value represents the “ capital energy or embedded energy” , as I have explained in my previous articles, the monetary terms do not totally represent the true resources or the environmental value. In researching this subject, I found a very important energy usage distribution of human kind. It is a known fact that we human beings need at least 2000-2500 calories daily, for our biological survival.

However, as human beings acquire more and more resources to sustain their complex life patterns, a proportionate increase of energy is also found to be necessary. I was surprised to note that the industrial human individual needs 130 times more energy than the primary energy needed to maintain our biological existence! That means, although the present population is estimated as 6.7 billion (2010), our real population burden would be (6.7 x 130), 871 billion people! and as far as the environment and the energy use is concerned, it would be the real human population. So, the increase in population does not matter as “Malthuse” had pointed out, but what it matters is the increase in energy and resource usage coupled with the pollution and waste created due to this unsustainable consumption pattern. Once Mahatma Gandhi correctly pointed out that, the mother earth could afford human needs, but not their greed.

The most challenging problem of our times is to explore for ways and means of meeting human energy demands in a sustainable manner without harming the environment.

Most of the scientists and Environmentalists are of the opinion that we should go to our roots, which means, to the sun. Each and every change, creature, enemy, human being are here on our mother earth because of the sun and its continuous flow of energy. That way, the sun and the solar energy is almighty God and the creator of this planet. (this fact is not a religious issue but I am talking about the abiological and biological existence of our mother earth) If we compare the energy that is coming from the sun, the energies generated by fossil fuel and other sources (which had been actually created by the sun) are negligible in quantity. Just one hour of sunlight is equal to one year’s total world energy consumption or just 3 days of solar energy is equal to the total energy of fossil fuel that is yet to be used.

Clean energy through solar power.

So if we have some mechanism within which we could harvest solar energy in an efficient manner, we would be able to solve our energy problem. Wind, biomass tidal etc. are indirect energy sources which are being produced by the solar energy. On the other hand we could directly harvest solar energy and generate electricity as clean energy.

Electricity can be produced from solar energy or sunlight by two main techniques. One is to produce heat from solar energy and convert that energy to produce electricity using a thermal heat powered turbine or by converting solar energy in to charge batteries which could store that energy using solar cells.

The first technique is called concentrated solar thermal (CST) and the second technique is called solar photovoltaic (PV) cells. The general mechanism of CST technique is that concaved mirrors which focus sun rays are being used to concentrate the solar energy. Then this energy is used to heat water or synthetic oil (therminol) to several hundred degrees of Celsius. This heat is then circulated through pipes to generate steam which in turn run the turbine and the generator which produce electricity. Now another innovative design has come up with some modifications to the CST method. In this method a huge power tower is installed and it is surrounded by a circle of mirrors.

These mirrors simply reflect back the solar radiation in power tower which has a large container of liquid or water. The heated water and steam are then coupled to a turbine generator. These types of power towers are now being operated in Seville - Spain and it shows that the power towers could store large amount of energy than the simple CST technique. So there are so many new designs to generate electricity using CST technique.

Using the CST method at present over 145 GW of electricity energy is being produced which is 0.5 % of the total energy consumed by the world.

The other technique is called photovoltaic (PV) cells. These cells are silicon based semi conductors and the solar energy is used to eject electrons and thus tiny electric currents may create like in diodes and transistors. These charges could be stored and used as electricity energy. Now over 13 GW (0.05% of total world energy) is being produced by solar PV method. Energy generated from PV method is more expensive than the CST method. But its size is small and anyone can smartly use these panels for various purposes. However, very serious researches are being done to improve the cost effectiveness of the PV system. Experts are now optimistic that very soon the solar power would be a cost advantage over fossil fuel based energy as this technology is improving with the rising of fuel prices.

If we consider the other advantages like the usage of water for power generation, the solar power needs very low quantities of water. In order to generate MWhr from nuclear energy, one needs 2000-4000 litres of water whereas a coal plant needs 1500-1600 litres of water. The solar PV needs no water and CST needs less water than the other options.

Solar power - viable solution for energy issues.

If we consider the carbon footprint or contained carbon for electricity generation by various sources, we could see that for one kwhr coal plants emits 966-1050 kg of carbon, whereas a Gas plant emits 443 kg and nuclear 1-288 kg of carbon. But solar CST contains only 13 kg and solar PV contains 32 kg. That means solar is not a 100% clean or green energy source but it contains less carbon than the other sources.

There is a proposal that if we install large solar panels in space we could collect more energy. Theoretically that is true because the intensity of solar energy is high in outer space. Then the collected energy could be transmitted to the earth using microwaves. But this proposal has not yet been experimented.

However, there are other smart proposals as well. When we design buildings, vehicles, ships or aeroplane we could use solar energy generation techniques and use solar energy wisely. Window cladding or rooftop of a building could be made solar panels or it could have walls and roofs so that the heat could not be accumulated or accumulated heat could be used during the winter.

The wings of an aeroplane, roof of a car could also be used as solar panel and there are so many solar energy tower stations along the side of the roads so that your battery power could be recharged.

Using solar energy street lighting, pumping of water for agricultural purposes are also practised in Sri Lanka as well. The Sun God is freely distributing enough energy for us, so why should not we tap this enormous and amazing kindness of the Sun God.