A centralised grid is inefficient and costly. Only a fraction of the fuel energy burnt in power plants ends up as electricity, with half lost as waste heat. Additional one-third is lost along long-distance transmission and distribution lines. Moreover, 20% of generating capacity is only there to meet peak demand, so it runs just 50% of the time and provides just 1% of supply.
Denmark, leading the world in decentralised power generation, now generates half of its electricity through decentralised grids with combined heat and power accounting for 80% of local-area heating, and wind power about 50% of all electricity. As an outcome, its carbon dioxide emissions have tumbled from 937 grams per kilowatt per hour in 1990, to 460 grams per kilowatt hour in 2007.
Electric utilities can also install their small generators near consumers. Security benefits may come from increasing the geographic dispersion of the nation´s electricity infrastructure and from reducing its vulnerability to terrorist attack that could interrupt electricity service over large areas.
Electric utilities are continually seeking alternative sources for generating electrical energy to meet the future demand. At present, hydroelectric generators, thermal and nuclear-generating stations are predominantly used for power generation and are referred to as conventional means of power generation. These generating plants are rotating machines that rely on electromechanical energy conversion.
The non-conventional energy sources that could offer suitable alternatives to the conventional sources include direct solar energy, wind energy, tidal power, biomass, geothermal energy, etc. All these sources are sun-based and hence renewable and can seasonally be restored by nature.
The objective of this post is due to the following observations:
- The knowledge of the limitation of the non renewable fuel sources.
- Inability of the public to wholly accept the concept of nuclear power generation
- Hydroelectric power plants has its limitations
- Imminent exhaustion of the natural topography which makes the erection of the hydroelectric plants non-viable
- The inherent limits for efficiency imposed by the Carnot cycle. We all know it is unavoidable to lose heat to the condenser as heat energy cannot be converted into mechanical energy without a temperature difference from the upper reservoir to the lower reservoir. The steam in the condenser is at the lowest temperature to allow the steam to expand to its lowest pressure. This loss of heat at different stages in the process is why the efficiency of thermal power plants are considerably low at about just 29%.
- The knowledge that the demand for power will continue to increase and as such there must be plans in place to match the demand as it comes.
- The need to reduce environmental degradation and pollution to the barest minimum, And this can be achieved by adopting widespread renewables which is a clean energy source.
- The need to eliminate the losses inherent in transmission and distribution and also to save cost with regards to transmission and distribution network.
- The growing accumulation of greenhouse gas emission and the rise in the cost of fossil fuel is another factor that motivated the shift from conventional generation to Renewables.
Based on the above points and given that the developing countries where these natural resources are abundant can harness it is quite attractive for the following reasons:
- The sources are replenished by nature and quite affordable because of its inherent low running cost.
- They have the least impact on the environment.
- They are available everywhere and can be sited near the rural dweller to improve their standard of living.
Distributed generation is the production of electricity at or near the place of consumption. There are little or no losses in transmission and distribution system. Distributed generation can be in the form of stand-alone generators in telephone exchanges, backup generators at hospitals, radio stations, cinema, solar photovoltaic systems on rooftops, and creative power/cogeneration in industrial plants.
The technologies involved in renewables offers means of using sustainable local resources, enhances widespread electrification and reliability, and minimising the impact on the global environment and degradation.
Renewable are modular. Solar and wind technologies do not take so much time to come into operation from installation, completion and operation as opposed to a hydroelectric power plant. They provide a flexible option for adding generating capacity in community-scale applications. We can construct biomass, geothermal, solar PV, wind and small hydro fairly rapidly. A consumer can produce one´s electricity. They can sell any excess electricity to power utility using net metering.
Wind Energy
Wind power is one of the most promoting technology for onshore and offshore applications. India ranks fifth with 13GW of installed capacity. From wind, Spain is producing around 25GW. The power is obtained from the conversion of the energy inherent in the wind into electricity with the help of wind turbine.
Wind turbines can be made of two or three propellers and arranged in such a way as to capture wind’s energy, which is mounted on the rotor, to generate electricity. The turbines are mounted on top of towers, taking advantage of the stronger and less turbulent wind at 30 meters or more above the ground.
A blade operates on much the same principle as an airplane wing: when the wind blows, a pocket of low-pressure air works on the downward side of the blade. The low-pressure air pocket then drags the blade towards it, turning the rotor by that action. This action is known as the lift.
A force acts on the lift which is much stronger than the wind´s force impressed on the front of the blade, which is called drag. The combination of lift and drag causes the rotor to spin like a propeller, and the turning shaft rotates a generator to make electricity.
Wind turbines can be used directly from the wind farm (stand-alone) applications, or they can be connected to the centralised power grid, or they can work in conjunction with photovoltaic (solar cell) system. The raw material is available free in nature and inexhaustible. The gestation period is small.
Ocean Tides and Waves
This form of energy is very obtainable in places surrounded by sea or large bodies of water.The total energy derivable from tides is enormous, at about 40000MW-2000000MW. Unfortunately, only a small fraction of these would be harnessed in the nearest future, and this is because the energy is spread diffusely over a wide area that is far from areas of consumption. The best mechanism for exploiting tidal and wave energy is to utilise estuarine barrages at suitable sites with high tidal ranges. The technology is relatively old, and to assemble the components won't be difficult.
Fuel Cell
The fuel cell has a great 21st century. A fuel cell converts chemical energy directly into electricity permitting a high efficiency of 50-70%. The solid oxide fuel cell uses high ceramic material rather than liquid electrolyte and operates at 1800 degree F. Depending on the operating cost and fuel required; this could be an excellent replacement to the millions of diesel generators used across Nigeria.
Solar
The harnessable solar energy could power entire Nigeria. We can apply solar energy to solar heating, that is active solar heating of water for home heating, hot water supply, air conditioning, drying various materials including farm produce, desalting of water.
In solar heating, higher temperature such as the one that could boil water or produce process steam can be obtained by applying devices such as parabolic mirrors or Fresnel lenses capable of bringing solar radiation into a focus. We can utilize this device in solar cookers and hot plate. It is primarily a parabolic reflector of diameter 1.2m which is made from high polish aluminium and secured to a base. The reflected focal point is the place for the container meant for either boiling water or cooking meals.
In most developing countries, woods accounts more than 50% of their energy consumption leading to widespread deforestation. But with direct conversion of solar energy to heat, the accumulation of greenhouse gas emissions, deforestation for the quest of wood will all be a thing of the past.
Agricultural uses for solar are numerous and include the drying of different types of crops which could either be by direct exposure to sunlight or the use of heated air passed through or over the material to be dried. They can be used for drying grains, fruits, vegetable, skin, hides, fishes etc.
Residential heating by solar has been successfully carried out and still in use today.
The production of salt using evaporation of seawater or inland brines has been in practice for ages and can be harnessed whenever salt containing water exists.
Photovoltaic (SPV) Cells: While both thin film and traditional silicon-based PV cells seem to set new efficiency records of 20%. For practical applications under typical conditions, efficiencies of 21% to 45% are expected to be reached in the not so distant future.
Nanotechnology allows us to make high-capacity, more efficient photovoltaic cells to make solar energy economically attractive. At present, every two years, the power from the solar panel is doubling.
Stand-alone solar photovoltaic system has the following possible applications: lighting (street, residences, public places, etc), running or operating electro-mechanical equipment (radio and other systems, TV and video players, fans, pump to set supply drinking or irrigation water, etc, supplying electrical power to operate poultry incubators, brooder houses, telecommunications´ equipment in remote areas, radios and 60V, 1500W, SPV (6 panels) irrigation tube wells.
Land availability is not a challenge to tap solar energy contrary to the concern expressed by most. Roof-top panel mounting can be adopted, and recently some roofs can double as solar panel and as roofs at the same time.
A solar cell is a junction diode that has provision for illumination by the solar spectrum and allows for electrical connections to an external circuit. Photons enter the cell through the front surface, which is usually with an anti-reflection layer alongside an encapsulation layer or glass plate depending on the type of cell.
Photons with energy more than the band gap of the semiconductor will be absorbed in the semiconductor and create electron-hole pairs. The minority carriers diffuse to the space charge region of the PN junction and are swept across the region by the built-in electric
Solar Thermal: The new solar thermal power plants which can generate electricity several hours after sunset, could reduce dependence on coal thermal power plants.
Geothermal Power
Geothermal power is the natural heat of the earth. It comes from heat energy buried beneath the surface of the earth. In some areas of the country (1000 MW potential), enough heat rises close to the surface of the earth to heat underground water to steam, which can be tapped for use at steam-turbine plants.
Small Hydropower
Hydropower is a process in which flowing water is used to spin a turbine connected to a generator. Small hydro-power up to 25MW is considered renewable. It is simple to construct and do not damage ecology. No resettlement of population is required. It needs to tap small rivers, rivulets, and artificial storage dams.
Thus, there is need for communities to invest in this type of projects, and this would boost the reliability and efficiency and at the same time savings in transmission and distribution networks. These communities can run and maintain its power system.
Biomass
Biomass includes wood, and agricultural waste, such as corn cobs, wheat straw, rice husk, Cotton straw, etc. These sources are the replacement of fossil fuels in the boiler. In addition to being renewable, recycling of the carbon by photosynthesis is one of the major attraction for biomass.
Biomass involves the production of gas by the anaerobic fermentation of animal dungs, organic and industrial wastes in airtight tanks. The gas produced can be used in an internal combustion engine or for cooking.There is more than 20000MW potential of power generation from biomass.
Biomass is renewable on a time scale that depends on its form. The hardware required and economics are closely related to the manner in which the resources are utilized.
Biomass can be utilized in different ways that include:
- Direct heating of air for cooking, process and space heating.
- Combustion as fuel for electric power generation.
Gasification and aerobic digestion (to produce biogas) for on-site use or transportation through pipelines to consumers.
The biogas technology has found favour all over the world as we can produce methane in anaerobic digesters from human, animal and agricultural wastes.
Urban Waste
According to a study (2007) in India, every year, in urban areas, municipal solid waste (garbage), there is 45000 million tonnes solid waste and 5000 tonnes of liquid waste, having the power generation potential of 27000MW.
Gas-based Small Power Generation
As far as possible, coal use must be discouraged. There should be laying of grid pipeline. Gas for decentralised power generation along the route of gas grid pipeline and close to load centres should be enabled. The typical plant sized can be in the range of 30-150MW can be installed. Combine cycle (CCGT) can be more beneficial having high efficiency of 70%. Overall, there may be saving 0f 70%, e.g., 30% Transmission and Distribution losses and 40% extra efficiency in the gas combined cycle.
Nanotechnology
Nanotechnology means the manipulation of individual molecules or group of atoms towards nanostructure engineering in the creation of useful materials, devices and systems. Fiber-based nano-generator would be an economical way to harvest energy from the physical movement of a person, making enough current to charge a cell phone or small MP3 music player.
Nanotechnology allows us to make high-capacity, more efficient fuel cells, photovoltaic cells with about 45% efficiency, light emitting diodes (LED) light, batteries to make these economically attractive. It will afford to make small size sensors with reduced weight, low power requirement and higher sensitivity.
CONCLUSION
As a mission, every village in the country should be made self-sufficient in energy using local natural resources. In villages solar, biomass, biogas, wind energy, geothermal energy, tidal waves (coastal communities), etc. have sufficient potential for power generation.
If we fully harness solar energy, it will go a long way to improve the standard of living of poor rural dwellers in Nigeria as well as contribute to the country´s future energy security. Harness solar energy using LED´s (Light Emitting Diodes) as the principal source of lighting.
The widespread use of renewables will also create sufficient jobs opportunities for rural people. For agriculture, install solar power electricity to power water pump for irrigation. Rainwater harvesting in villages maybe mandatory to charging and storage (for re-use) in village ponds to safeguard falling water table.
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