Nigeria’s over-dependence on gas powered turbines and a few hydro power plants is the reason for her inability to generate enough power for her domestic needs as well as meet her international obligations to her neighbours. It is beyond my imagination why NEPA/PHCN has not ventured into renewable power generation with all the shortcomings experienced in their current and past concentration on gas powered systems! It is as if that is the only power generating model known to them.
Wind power is the conversion of wind energy into a useful form of energy, such as electricity, using wind turbines. The wind turbines are power systems consisting of two or three blades, propelled by the wind and attached to a shaft with gear mechanisms and generators sitting on top of a tower.
Wind mills dated back over a hundred years. Technological improvements has made it more powerful, robust, easier to deploy, flexible and adaptable to a lot of climatic conditions and hence now referred to as wind turbines.
Large-scale wind farms are connected to the electric power transmission network (on-grid); whereas smaller facilities are used to provide electricity to isolated locations (off-grid). Utility companies in Europe and USA increasingly buy back surplus electricity produced by small domestic turbines. Nigeria is also on the match to develop and pass a legislation that will require PHCN to buy surplus electricity generated by small independent power producers. The NERC (Nigeria electricity regulatory commission) and ECN (Electricity commission of Nigeria) are behind the legislation.
Wind energy as a power source is attractive as an alternative to fossil fuels, because it is plentiful, renewable, widely distributed, clean and produces no greenhouse gas emissions. However, the construction of wind farms is not universally welcomed due to their visual impact and other effects on the environment.
Wind power is non-dispatchable, meaning that for economic operation, all of the available output must be taken when it is available. Other resources, such as hydropower, and standard load management techniques must be used to match supply with demand. The intermittency of wind seldom creates problems when using wind power to supply a low proportion of total demand. Where wind is to be used for a moderate fraction of demand such as 40%, additional costs for compensation of intermittency are considered to be modest.
The challenges of intermittency is shared commonly by all power systems; solar power has to deal with issues of sunshine and cloudy days, gas turbines have to deal with gas supply and price fluctuation issues, hydro plants have to contend with dry or rainy seasons and water levels behind the dams.
All over the world conventional and alternative power generation systems are not fail-proof and are therefore integrated with each other to provide stable and uninterrupted power supply to consumers. Nuclear, hydro, gas power plants are interconnected with each other along the same transmission lines to provide seamless power supply to consumers. When one power source goes down a back up source is activated to cover the shortfall. No nation depends on only one or two sources of power generation no matter how abundant. That is why even in the US and Europe with very stable and highly integrated variety of power supply systems the market for standby generators and back-up UPS/batteries is still huge.
At the end of 2008, worldwide nameplate capacity of wind-powered generators was 121.2 gigawatts (GW). In 2008, wind power produced about 1.5% of worldwide electricity usage; and is growing rapidly, having doubled in the three years between 2005 and 2008. Several countries have achieved relatively high levels of wind power penetration, such as 19% of stationary electricity production in Denmark, 11% in Spain and Portugal, and 7% in Germany and the Republic of Ireland in 2008. As of May 2009, eighty countries around the world are using wind power on a commercial basis, off course Nigeria is not one of them.
The renewable wind energy market in Nigeria has not arrived. I hope Nigeria is not waiting for the time when ‘tokunbo’ (second hand) wind turbines will be available before acquiring them as alternative power supply source.
Studies commissioned by the Federal ministry of science and technology (not PHCN or ministry of power) carried out by Lahmayer International has confirmed great potentials and identified possible sites for viable wind energy projects across Nigeria.
From a recent study across Nigeria by a group of reseachers (Ogbonaiya Okoro and others), the mean speed at a height of 10m above the ground ranges between 2.3m/s to 3.4m/s for selected sites along the coastal areas and 3.0m/s to 3.9m/s for high land areas and semi-arid regions. The rule is that the higher up you go the windier it gets. Wind turbines are normally installed at heights of between 18m to 90m above ground.
Several researchers have shown that in areas with annual mean wind speeds of 3.5m/s- 4.0m/s or greater, wind power systems can usually deliver electricity or pump water at costs lower than photo-voltaics, diesels, or grid –extension.
By using meteorological data collected from some selected weather stations in Nigeria, analysis of such data shows that wind power prospects in Nigeria is high. From the analysis also, it was clearly seen that coastal and hilly areas are excellent sites for wind power development. Therefore, using wind turbines for electric power generation and supply in Nigeria—especially around areas with mean wind speed of about 3.78m/s, will be cost effective.
CONCERNS ABOUT WIND POWERED GENERATORS
Compared to the environmental effects of traditional energy sources, the environmental effects of wind power are relatively minor. Wind power consumes no fuel, and emits no air pollution, unlike fossil fuel power sources. The energy consumed to manufacture and transport the materials used to build a wind power plant is equal to the new energy produced by the plant within a few months of operation. Garrett Gross, a scientist from UMKC in Kansas City, Missouri states, "The impact made on the environment is very little when compared to what is gained." While a wind farm may cover a large area of land, many land uses such as agriculture are compatible, with only small areas of turbine foundations and infrastructure made unavailable for use.
Danger to birds and bats has been a concern in some locations. However, studies show that the number of birds killed by wind turbines is negligible compared to the number that die as a result of other human activities, and especially the environmental impacts of using non-clean power sources. Bat species appear to be at risk during key movement periods. Almost nothing is known about current populations of these species and the impact on bat numbers as a result of mortality at wind power locations. Offshore wind sites 10 km or more from shore do not interact with bat populations.
Aesthetics have also been an issue in some areas. In the USA, the Massachusetts Cape Wind project was delayed for years partly because of aesthetic concerns. In the UK, repeated opinion surveys have shown that more than 70% of people either like, or do not mind, the visual impact. According to a town councillor in Ardrossan, Scotland, the overwhelming majority of locals believe that the Ardrossan Wind Farm has enhanced the area, saying that the turbines are impressive looking and bring a calming effect to the town. The turbines are more than 3 kilometers from the town.
Nigeria is in dire straits with reference to her power supply needs for industries and general usage. Nigeria is therefore not in a position to pick and choose what her sources of power generation should be, based on cosmetics. Nigeria should diversify and integrate her power sources with a mix of gas, wind, solar, nuclear, hydro, biomass etc with each contributing to the national grid. Aesthetics and environmental impact considerations are both good but let us have enough to power our needs and necessities first. An African adage says ‘the dog that is full should not play with a hungry dog’
INTERMITTENCY OF WIND POWER
Intermittent energy source is a term usually used to refer to some sources of renewable energy, such as wind and solar,( but not to geothermal generated electricity or nuclear electricity), because these sources of electric power generation may be uncontrollably variable or more intermittent than conventional power sources. However it needs to be borne in mind that conventional sources are also intermittent to the extent that they cannot be relied on 100% and therefore means have to be provided to deal with their intermittency – such as multiplication of sources, fast acting reserves and interconnection with other systems.
The Nigerian environment is not different. Nigeria needs to diversify her types and sources of power generation. Nigeria’s almost total dependence on hydro and gas powered turbines is the cause of her inability to have steady power supply.
Even as it were, for very large penetrations of the most intermittent source, wind energy, such sources become highly reliable, and whilst the aggregate output can change with weather changes, this is highly predictable, and much more reliable than say a single large power station which can (and do) fail suddenly and unpredictably.
Technological solutions to deal with large scale wind energy type intermittency already exist and studies by academics and grid operators indicate that the cost of compensating for intermittency is expected to be low even at levels of penetration substantially higher than those prevailing today. Large, distributed power grids are better able to deal with high levels of penetration than small, isolated grids. For a hypothetical European-wide power grid, – ( European super grid] analysis has shown that penetration levels as high as 70% are viable, and that the cost of the extra transmission lines would be only around 10% of the turbine cost, yielding power at around present day prices. Smaller grids may be less tolerant to high levels of penetration.
Matching power demand to supply is not a problem specific to intermittent power sources. Existing power grids already contain elements of uncertainty including sudden and large changes in demand and unforeseen power plant failures. Though power grids are already designed to have some capacity in excess of projected peak demand to deal with these problems, significant upgrades may be required to accommodate large amounts of intermittent power. But again, large amounts of large inflexible plant (nuclear, supercritical coal, coal plus CCS) will also require grid upgrades and increased interconnection or incur financial costs – e.g the French nuclear programme necessitated its 2 GW HV link to UK, and increased imports and exports to neighbouring countries.
The International Energy Agency (IEA) states: "In the case of wind power, operational reserve is the additional generating reserve needed to ensure that differences between forecast and actual volumes of generation and demand can be met. Again, it has to be noted that already significant amounts of this reserve are operating on the grid due to the general safety and quality demands of the grid. Wind imposes additional demands only inasmuch as it increases variability and unpredictability. However, these factors are nothing completely new to system operators. By adding another variable, wind power changes the degree of uncertainty, but not the kind…"
The US Federal Energy Regulatory Commission (FERC) Chairman Jon Wellinghoff has stated that “baseload capacity is going to become an anachronism” and that no new nuclear or coal plants may ever be needed in the United States implying that his organization does not see intermittency as an issue.
At present, the penetration of intermittent renewables in most power grids is low, but wind for example provides nearly 20% of the electricity generated in Denmark (where plans are underway to increase this substantially) 11% in Spain and Portugal, 9% in the Republic of Ireland, and 7% in Germany. The use of small amounts of intermittent power has little effect on grid operations. Using larger amounts of intermittent power may require upgrades or even a redesign of the grid infrastructure. However, it should be borne in mind that large amounts of large inflexible plant, such as nuclear or supercritical coal or coal plant equipped with CCS will also require significant grid upgrades to deal with their inflexibility.
Small-scale wind power
Small scale wind power is the name given to wind generation systems with the capacity to produce up to 50 kW of electrical power. Isolated communities, that may otherwise rely on diesel generators may use wind turbines to displace diesel fuel consumption. Individuals may purchase these systems to reduce or eliminate their dependence on grid electricity for economic or other reasons, or to reduce their carbon footprint. Wind turbines have been used for household electricity generation in conjunction with battery storage over many decades in remote areas.
Grid-connected wind turbines may use grid energy storage, displacing purchased energy with local production when available. Off-grid system users can either adapt to intermittent power or use batteries, photovoltaic or diesel systems to supplement the wind turbine. In urban locations, where it is difficult to obtain predictable or large amounts of wind energy (little is known about the actual wind resource of towns and cities, smaller systems may still be used to run low-power equipment. Equipment such as parking meters or wireless Internet gateways may be powered by a wind turbine that charges a small battery, replacing the need for a connection to the power grid.
A new Carbon Trust study into the potential of small-scale wind energy has found that small wind turbines could provide up to 1.5 terawatt hours (TW·h) per year of electricity (0.4% of total UK electricity consumption), saving 0.6 million tonnes of carbon dioxide (Mt CO2) emission savings. This is based on the assumption that 10% of households would install turbines at costs competitive with grid electricity, around 12 pence (US 19 cents) a kWh.
Distributed generation from renewable resources is increasing as a consequence of the increased awareness of climate change. The electronic interfaces required to connect renewable generation units with the utility system can include additional functions, such as the active filtering to enhance the power quality.
Report prepared by Olumide Ogunleye