conventional and non-conventional sources of renewable energy
June 5, 2009
What are the conventional and non-conventional sources of renewable energy?
Conventional : Energy that has been used from ancient times is known as conventional energy. Coal, natural gas, oil, and firewood are examples of conventional energy sources. (or usual) sources of energy (electricity) are coal, oil, wood, peat, uranium.
Non-conventional (or unusual) sources of energy include:
• Solar power
• Hydro-electric power (dams in rivers)
• Wind power
• Tidal power
• Ocean wave power
• Geothermal power (heat from deep under the ground)
• Ocean thermal power (the difference in heat between shallow and deep water)
• Biomass (burning of vegetation to stop it producing methane)
• Biofuel (producing ethanol (petroleum) from plants
We hope that all the conventional sources will become rare, endangered and extinct, as they produce lots of carbon dioxide that adds to the greenhouse effect in the atmosphere (uranium leaves different dangerous byproducts).
And we similarly hope that all the non-conventional sources will become conventional, common, and every day, as they are all free, green and emit no carbon dioxide (well, biomass does, but it prevents the production of methane which is a greenhouse gas 21 times more dangerous that CO2).
Brief description of non-conventional energy resources:
Most of the renewable energy is ultimately “Solar energy” that is directly collected from sun light. Energy is released by the Sun as electromagnetic waves. The energy reaching earth’s atmosphere consists of about
• 8% UV radiation
• 46% visible light
• 46% infrared radiations
Solar Heating is to capture/concentrate sun’s energy for heating buildings and for cooking/heating foodstuffs etc. solar electricity is mainly produced by using photovoltaic solar cells which is made of semi conducting materials that directly converts sunlight into electricity. Obviously the Sun doesn’t provide constant energy at any spot on the Earth, so it’s use is limited. Therefore often Solar cells are used to charge batteries which are used either as secondary energy source or for other applications of intermittent use such as night lightening or water pumping etc. A solar power plant offers good option for electrification of disadvantageous locations such as hilly regions, forests, deserts and islands where other resources are neither available nor exploitable in techno economically viable manner.
The origin for Wind Energy is Sun. When sun ray falls on the earth, it’s surface gets heated up and as a consequence unevenly winds are formed. Kinetic energy in the wind can be used to run wind turbines but the output power depends upon the wind speed. Turbines generally require a wind in the range of 20km/hr. In practice relatively few land areas have significantly prevailing winds. Otherwise wind power is one of the most cost competitive renewable energy today and this has been the most rapidly-growing means of electricity generation at the turn of 21st century and provides a complement to a large scale base load power stations. Its long term technical potential is believed to be 5 times current global energy consumption or 40 times current electricity demand.
Energy in the water can be harnessed and used in the form of motive energy or temperature difference. Since water is about 1000 times heavier than air, even a slow flowing stream of water can yield great amount of energy.
There are many forms:
• Hydroelectric energy, a term usually reserved for hydroelectric dam
• Tidal power, which captures energy from the tides in horizontal direction. Tides come in, raise water levels in a basin, and tides roll out. The water is made to pass through turbine to get out of the basin. Power generation through this method has a varying degree of success.
• Wave power, which uses energy in waves. The waves will usually make large pontoons go up and down in the water. The wave power is also hard to tap.
Hydro electrical energy is therefore only viable option. However , even probably this option is also not there with the developed nations for future energy production because most major sites within these nations with potential for harnessing gravity in this way are already being exploited or are unavailable for other reasons such as environmental consideration. On the other side, large hydro potential of millions of megawatts is available with the developing countries but major bottleneck in the way of development of these large hydro projects is that each site calls for the huge investment.
Micro/Small hydro power
This is non-conventional and renewable source and is easy to tap. Quantitatively small volume of water, with large falls and quantitatively not too large volumes of water, with small fall, can be tapped. This force of flowing and falling water is used to run water turbines to generate electricity.
Geothermal energy is very clean source of power. It comes from radioactive decay in the core of the Earth, which heats the Earth from inside out and thus energy/power can be extracted owing to the temperarture difference between hot rock deep in the earth and relatively cool surface air or water. This requires that the hot rock be relatively shallow, so it is site-specific and can only be applied in geologically active areas.
It can be used in two ways
• Geothermal heating
• Geothermal electricity
As stated above, geothermal energy from the core of the earth is closer to surface in some area than in others. Where hot underground steam or water can be tapped and brought to the surface it may be directly used to heat or cool buildings or indirectly used to generate electricity by running steam turbines. Even otherwise, on most of the globe, the temperature of the crust few feet below the surface is buffered at a constant 7-14 degree Celsius, so liquid can be pre-heated or pre-cooled in underground pipelines, providing free cooling in the summer and heating in the winter by using heat pumps.
Plants use photosynthesis to store solar energy in the form of chemical energy.The easiest way to release this energy is by burning the dried up plants. Solid biomass such as firewood or combustible field crops including dried manure is usually burnt to heat water and to drive turbines. Field crops may be grown specifically for combustion or may be for other purposes and the processed plant waste then used for combustion.Most sort of biomass including sugarcane residue, wheat chaff, corn cobs and other plant matter can be, and is, burnt quiet successfully. Currently biomass contributes 15% of total energy supply world wide.
A drawback is that all these biomass needs to go through some of these steps: It needs to be grown, collected, dried and fermeneted and burned. All of these steps require resources and an infrastructure.
Bio-fuel is any fuel that derives from biomass- recently living organisms or their metabolic byproducts, such as manure from cows. Typically bio-fuel is burnt to release it’s stored chemical energy. Biomass, can be directly used as fuel or to produce liquid biofuel. Agriculturally produced biomass fuels, such as biodiesel, ethanol and bagasse(often byproduct of sugarcane cultivation) can be burnt in internal combustion engines or boilers.
Biogas can easily be produced from current waste streams,such as paper production, sugarcane production, sewage, animal waste and so forth. The various waste streams have to be slurred together and allowed to naturally ferment, producing 55% to 70% inflammable methane gas. Biogas production has the capacity to provide us with about half of our energy needs, either burned for electrical productions or piped into current gas line for use. This has to be done and made a priority. The payback period of biogas is around 2-3 years, rather in case of community and institutional Biogas plant is even less. Therefore biogas electrification at community level is required to be implemented.