Economic development is driven by energy. Throughout most of the world, development has been driven by energy sources derived from coal, oil and natural gas. As a result, a lot of damage to the natural environment has been recorded over years. This has spurred the interest into the use of alternative sources of energy. It is a common goal for every government to curb environmental destruction and ensure economic development that does not hinder the ability of future generations to prosper.
Scientists and scholars have emphasized the need for adoption of clean energy resources. According to the Intergovernmental Panel on Climate Change (IPCC), the use of fossil fuels since 1850 has been increasing and dominating energy supply globally. This has led to increased carbon emissions to the atmosphere. “Emissions continue to grow and CO2 concentrations had increased to over 390 ppm, or 39% above preindustrial levels, by the end of 2010” The IPCC concluded that the global increase in average temperature is most likely attributed to the increase in greenhouse gases in the atmosphere. The move towards renewable energy is therefore the most important mitigation strategy for sustainable development. Further, the use of renewable sources of energy diversifies a country’s energy supply which results to rapid economic development.
What Is Renewable Energy?
Sources of energy are either repositories of energy or occur as flows of energy in the environment. Coal and natural gas occur in repositories and can therefore run out over time. Renewable energy sources also referred to as infinite sources are those sources that naturally replenish quickly and can never be depleted no matter how long they are used. These sources usually occur as natural flows or processes. There are a number of renewable resources that have the potential to meet the world’s energy demands. Sources from solar, wind, water, geothermal and biomass can sustainably be used over time for a wide range of uses. Consequently, there has been an increase in awareness on the benefits of switching to renewable resources due to the changing perceptions about energy. Still, the adoption of renewable energy is still considerably lower.
Challenges To Adoption Of Renewable Energy
Renewable energy gained the interest of policymakers and key energy players in the 1970s and early 80s, but the interest faded due to falling fuel prices and abundant supply of these fuels.
The move towards use of renewable energy sources has been hindered by a number of factors;
In his book, Renewable Energy: A first course, Robert Ehrlich sites the lack of awareness on impacts of fossil fuels on the environment.
“….the awareness of the environmental problems associated with fossil fuels has come very gradually, and views on the seriousness of the threat posed by climate change vary considerably. Moreover, in times of economic uncertainty long-term environmental issues can easily take a backseat to more immediate concerns, especially for homeowners’’
The cost competitiveness of renewable energy resources remains quite low compared to non renewable energy. In addition to the upfront costs involved during installation, the costs for producing larger quantities for energy varies across different renewable energy sources. It is difficult to estimate externalities for renewable resources. The Renewable Energy Policy Network for the 21st Century (REN21) recommends availing high quality and timely information on renewable energy to facilitate informed decisions by leaders and policymakers.
Status Of Global Renewable Energy Use
Most cities and towns in the world have plans, policies, and targets to advance renewable energy, often far outpacing the ambitions of the national legislation. The efforts of local government are often constricted by national budgetary provisions.
However, it is not all gloomy as the private sector is rapidly increasing investment in renewable resources. In this decade, the market for renewable energy technologies is experiencing steady growth due to factors like rising fuel prices, improvements in renewable energy technologies, and the increasing political support due to concerns about energy security and climate change. Private investment has increased to $70 billion in 2007 from $50 billion in 2005. Most technologies are still in developmental stages.
In the U.S alone, the Annual Outlook 2014 reports solar photovoltaic technology as the fastest-growing energy source for renewable generation, at an annual average rate of 6.8%. Wind energy accounts for the largest absolute increase and for 40.0% of the growth in renewable generation from 2013 to 2038. It is further projected to displace hydropower and become the largest source of renewable generation by 2040. The table below illustrates trends in production over recent times.
Renewable Sources Of Energy
Solar energy: The sun is the ultimate source of almost all energy systems in the universe. In most parts of Sub Saharan Africa, people heat water or dry agricultural produce directly by exposing them to sunlight. Solar technologies make use of solar radiation concentrate solar power and generate electric power through photovoltaics (PV). Solar heating is one of the most common applications of solar power systems. Solar heaters can either be fluid based or air-based.
Wind energy is fast catching on as an alternative renewable energy resource and buying wind turbines has become to more and more popular. According to the Global Wind Energy Council;
“Wind power has now firmly established itself as a mainstream option for new electrical generation. The most remarkable recent development is that in an increasing number of markets, wind power is the least cost option when adding new generation capacity to the grid, and prices continue to fall. There are now commercial wind power installations in more than 90 countries with total installed capacity of 318 GW at the end of 2013, providing about 3% of global electricity supply last year”.
What Is Wind Energy?
Wind energy also referred to as ‘wind power’ is obtained from natural wind flows in the atmosphere. The potential of an area to provide sufficient wind energy is estimated through the measuring of wind energy density and wind speed of the area. The commercial use of wind energy became profound in the 1970s after a number of technological advancements. A number of wind technologies have been developing since. Wind turbines are used to harness the wind and convert it to electrical energy. Wind turbines can either be deployed on land or on sea. Wind technology has evolved from small, single wind turbine installations to more advanced grid connected wind turbines.
The most remarkable new growths are occurring in Brazil, Mexico and South Africa. The technical potential to develop wind power is still limited in Africa and Latin America.
The turbines are turned by wind to power electricity generators. The turbine converts the kinetic energy of moving air to electricity. A home wind turbine is smaller than a commercial turbine. A larger turbine has larger generation capacity. Most turbines today are designed as horizontal axis machines with 3 blades standing on 50-100m towers. They are of two types depending on their axes. They could be either horizontal-axis turbines or vertical-axis turbines. The horizontal-axis turbines are the most efficient and modern turbines.
Components of the horizontal-axis turbine:
Rotor (blade)- it converts the kinetic energy of the air currents into rotational shaft energy;The drive train- contains a generator and a gearbox The tower that supports the blades; and Peripheral equipment like controls, ground support equipment, electrical cables, and interconnection equipment.
The size of the wind turbines has been increasing over the recent years and so is the potential power generated. Commercial large scale wind power production involves establishment of multiple turbines in a wind farm. The wind farm is ordinarily connected to utility grid which distributes power to various connected locations.
The value of a wind farm is dependent on the energy yield which is subject to prevailing wind speeds. A change in wind speed therefore makes a difference in financial value of the farm. Every wind farm has a meteorological assessment for estimation of wind resource.
Average wind speeds vary across different geographic locations and this means different energy potentials with varying locations. However, technology improvements have created potential for wind energy deployment in areas with lower wind speeds. Variable speed turbines now exist in the market. These turbines allow for generation of real and reactive power. They are also developed with a fault-ride capability. The main weakness of the turbines is that they do not have the capability to vary power output in relation to the power system imbalances. Research is underway to improve this.
Despite trends in development of wind power, wind energy’s share in electricity supply globally is still relatively low.
Here are some of the interesting wind energy facts;
Wind Power Facts
– Wind is a form of green power
– Wind power is generated from wind which is a form of solar energy. Wind develops form irregular heating of the earth’s atmosphere. This irregularity is caused by the varying nature of the earth’s surface. The series of heat exchanges and air displacement processes cause constant air movement.
– Wind turbines convert the wind’s kinetic energy to mechanical energy that can be used for generating other forms of power. For example, a windmill can harness wind and power a wind generator which then converts the mechanical power to electricity for homes.
– Windmill energy was produced as early as the 1st century.
– Water wind pumps were used in Afghanistan as early as the 9th C.
– The traditional use of windmills was pumping water to homes or farms especially where water flows were weak or scarce.
– Large wind turbine rotors generate more energy. The higher the height of turbine support, the higher the quantity of energy produced. For instance, a wind turbine with blades of at least 120yards long and standing at least 20 stories high has potential to supply power for at least 1400 homes.
– Wind power is one of the top alternative energy sources and comprised 43% of all new U.S. electric capacity additions in 2012 and represented $25 billion in new investment. (Source: 2012 wind technologies market report).
Advantages Of Wind Energy
– It is one of the most abundant renewable energy sources. It is an inexhaustible green energy. Wind power plants do not produce any smoke. It is a clean alternative energy. In fact, according to the U.S Energy department’s statistics, in 1990, the use of wind energy reduced the emission of greenhouse gases by a huge margin and therefore ensures improved air quality.
– Wind power plants are cheap to operate.
– Wind turbines are space efficient. Unlike other forms of energy generation, wind power plants use relatively smaller spaces. They can be located on farm lands without interfering with land uses.
– Residential wind turbines are easy to install and can effectively substitute electricity demands because wind power has enormous power generation capacity.
– Wind cannot be stored and can only be used when it is available. It is unpredictable. For this reason, wind turbines are commonly installed in remote areas often far from areas where the energy will be used. Wind speeds and strength is often affected by obstructions. Wind changes direction if encounters an obstacle or resistance.
– The turning of the wind turbine can be noisy for those with close proximity to wind farms or power plants. Even a home wind turbine can create some noise that one has to get used to.
Hydropower: It is among one of the most common renewable sources of energy. Hydro power is derived from the action of moving water. Water power is typically produced by damming a river. The water is channeled through turbines to produce hydroelectric energy.
The turbines’ rotating blades spin the electricity generator that transforms the mechanical energy of the turning turbines into electrical energy. The amount of electric power generated from each hydro energy plant is largely dependent on the quantity of water flowing and the height of the fall.
How Hydroelectricity Is Generated
Most hydroelectric power plants are located near canals, rivers or streams. Dams are created across river channels to ensure a constant and reliable water supply. The dam is created at a higher point of the river; above the location of the water turbines. The dam therefore creates sufficient head for the water to fall. A penstock is used to channel the water to the turbines and create higher speed and pressure. The size of the penstock is determined by the size of turbine that powers the generator. The falling water moves the blades of the turbine powering the electric generator. When the coils of the rotor sweep past the generator, electricity is produced. The water is rechanneled to the river unchanged. The power plant consists of transformers from where power is distributed via transmission lines to various destinations connected to that power grid. The quantity of electricity produced by a plant can be easily computed and upgrades can be made with very minimal modification.
Types of Hydro Power Plants
s Run of river stations – electricity is produced through direct flowing of the river
s Reservoir stations – power is generated through releasing stored water
s Pumped storage stations – makes use of two reservoirs. Stored water is pumped back up to a higher reservoir in order to be released again. This electricity is usually generated to meet peak load and therefore allow the optimum use of other less versatile sources of electricity. They are usually the largest and have greater generation capacity. All the other stations can be upgraded to pumped-storage plants.
Trends In The Use Of Water Energy
According to the World Energy Council; at the end of 2011, over 160 countries had hydropower resources capacity, with a total capacity of 936 GW across 11,000 hydropower stations. The leading generating countries were China, Canada, Brazil and the USA respectively, although it is worth noting that Norway and India both have significant hydropower generation, particularly relative to their size and total electricity supply.
“Since 1990, global hydropower generation has increased by 50%, with the highest absolute growth in China. However, globally, around 19% of the potential has been developed. Countries which have actively developed hydropower use around 60% of their potential. Numerous other countries have a huge amount of untapped hydropower potential” (International Energy Agency [IEA]).
Generation costs of hydroelectricity vary by capacity of power developed. The cost of upgrading an existing plant’s capacity is considerably lower than setting up a new plant. This is because investment costs are affected by the size and presence of a reservoir, possible benefits/returns, and project location.
Barriers to growth of hydroelectric power production
The generation of hydroelectric power is usually affected by potential impacts on social and natural environment. The process of assessing these impacts and analyzing feasibility is time consuming and difficult. According to the IEA, some issues that arise from large production initiatives include:
s Economic equity among citizens.
s Protecting the lives and property of citizens from floods and droughts.
s Securing the rights of citizens with respect to expropriation of land to be inundated.
s Protecting the environment concerning air, land, water and biodiversity.
These issues compounded by conflicting policy agendas bring hydropower generation to political arena.
Advantages Of Hydro Power
Apart from being a green power source, it possesses a unique property over other alternative energy sources.
– Unlike other alternative renewable energy sources, water energy can be regulated and is more reliable.
– Hydropower’s fast response and storage capacity (the dam acts a power storage reservoir) characteristics are especially useful in meeting sudden electricity demand fluctuations and matching supply from less variable renewable sources and less versatile electric power sources.
– It can be produced independently by various states without relying on international sources.
– Dams used for hydropower generation can be used for secondary activities like water sports
Disadvantages Of Hydropower
Hydropower plants can affect water quality for aquatic life. The plants can cause low dissolved oxygen levels in the water, a problem that is harmful to riparian habitats and is addressed using various aeration techniques for water oxygenation. Maintaining minimum flows of water downstream of a hydropower installation is also critical for the survival of the riverine habitats. (U.S Department of Energy)
Tidal energy: Power developed form ocean tides. The tides turn turbines which transform tidal energy to mechanical energy. Tides are a result of interaction the earth, the moon and the sun’s gravity. The rise and fall of tides (ocean currents develop kinetic energy) creates potential energy. It was reportedly used in the Romans times but started to be developed commercially in the 1960s. So far, since then only about 5 projects have been developed up to the year 2012. The most recent and largest tidal barrage in the world is in north-eastern South Korea. It is called the Sihwa dam and was built in 2011 and started operating in 2012.
Tidal Energy Technologies
1. Tidal range technology – they harness the tides potential energy created by the difference in head between the flood and ebb tide. Such resources are found where there are large water mass flows into compounded water zones (estuaries) due to geological conditions. The world’s theoretical tidal power potential is in the range of 1 to 3 TW, located in relatively shallow waters (IPCC 2012). The harvesting can occur through one-way power generation at the ebb tide; a one-way power generation at the flood tide; or a two-way power generation at both outgoing and incoming tides.
2. Tidal current technologies – these are the most commercially available technologies. The power production mechanism is similar to that of wind turbines. Large scale projects make use of horizontal-axis turbines. A large number of these turbines are currently being developed in the UK’s territorial waters. The international Renewable Energy Agency in 2014 noted that 76% of all tidal current projects have horizontal –axis turbines. And in 2011, 76% of all R&D went into horizontal –axis turbines, 4% into enclosed turbines and 2% into vertical-axis turbines. (Joint Research Centre, 2013).
3. Ocean current technology- studies into generation of electricity using ocean currents is ongoing. So far no such installations have been made. Despite their slow speeds, ocean currents are continuous.
Generally, the world’s tidal resources are enormous but are also largely unmapped. The Carbon Trust 2011 estimated the technically harvestable parts near the coasts at 1TW. Often, the tidal range is determined by the shape and form of the coastline.
Advantages of tidal energy
Tidal range energy is predictable, as the energy production is not influenced by weather conditions, but rather by the cyclical constellations, the gravity of the moon, sun and earth, providing a predictable bi-week, biannual and annual cycle (International Renewable Energy Agency, 2014).
Geothermal energy: The main sources of geothermal energy are the residual energy available from planet formation and the energy continuously generated from radionuclide decay. The tapped heat from an active reservoir (the earth’s core) is continuously restored by natural heat production, conduction and convection from surrounding hotter regions, and the extracted geothermal fluids are replenished by natural recharge and by reinjection of the cooled fluids (IPCC 2012). Geothermal are physically similar to steam thermal power stations. The heat from the earth’s interior is extracted using wells and is used to heat a working fluid which then turns a generator turbine to generate electricity. Geothermal technology has developed well and has been in use for at least 100 years. The conventional geothermal plants make use of binary cycle units and steam condensing turbines. Geothermal resource potential requires a number of surveys including geological, geophysical and geochemical surveys.
Limitations of geothermal energy generation
Geothermal operations release carbon dioxide and therefore contribute to GHG emissions. A field survey of geothermal plants operating in 2001 found a wide spread in the direct carbon dioxide emission rates, with values ranging from 4 to 740 g/kWhe depending on technology design and composition of the geothermal working fluid in the underground reservoir.
Geothermal activities have large space requirements. This might cause competing land uses. The effects of these activities on other natural resources cause a serious impediment in development of geothermal energy.
Bio-energy: Energy developed from biomass (organic). Biomass stores solar energy in form of chemical energy. Biomass can be converted to liquid fuel, gas or bio products. Biomass is available as plant waste, agricultural/forestry products or as animal waste. Development of biomass energy is dependent on availability of sunlight and abundance of natural plant resources and advanced bio energy R&D.
IPCC estimates that in 2008, biomass provided about 10% (50.3 EJ/yr) of the global primary energy supply. Low efficiency technologies include use of plant material for cooking or heating. This is a major contributor to green house gas emissions. Furthermore, increased demand for fuel causes deforestation. Therefore, at this level it cannot be seen as sustainable energy.
Technology advancements have led to high efficiency bio technologies. These are common in developed countries and include development of convenient solids, liquids and gases as secondary energy carriers to generate heat, electricity, combined heat and power (CHP), and transport fuels for various sectors. This is relatively a new green energy technology. Biomass fuels are derived from anaerobic digestion of organic residue. From recent renewable energy news, Australia is markedly a top producer of biomass energy.
1. U.S. Energy Information Administration, Annual Energy Outlook 2015 With Projections to 2040
2. IRENA Ocean Energy Technology Brief 3, 2014. www.irena.org
3. Doner, J. (2007), Barriers to Adoption of Renewable Energy Technology. Illinois State University, Institute for Regulatory Policy Studies.
4. AEE – Institute for Sustainable Technologies (2009), Thermal use of solar energy. Soltrain; training course for experts and professionals
5. Herzog, Antonia V., Timothy E. Lipman, and Daniel M. Kammen. Renewable Energy Sources. Berkeley, CA: Energy and Resources Group.
6. Wiser Ryan and Mark Bolinger 2013, 2012 Wind Technologies Report accessed on https://emp.lbl.gov/publications/2012-wind-technologies-market-report
7. IPCC 2014, Renewable Energy Sources and Climate Mitigation: Summary for Policymakers and Technical Summary. Technical Support Unit Working Group III
Potsdam Institute for Climate Impact Research (PIK).