Renewable Energy in Practice

Executive Summary

First, the report gives a general introduction to renewable energy and its definition. Secondly, the various forms of commonly used renewable energy are discussed one at a time. Thirdly, the review of technology used to generate each renewable energy is given. Under the technology is also the awareness and limitations of different forms of energy. Also, the demerits and merits of the popular sources are discussed. Finally in the conclusion, hydroelectricity which is the most popular of all renewable energy is again reviewed but this time in relation to all other sources of energy in terms of applicability, factors to consider before setting a plant, and merits and demerits.

Introduction

Renewable energy refers to energy obtained from natural resources and therefore they can be renewed or in other words, they can undergo natural replenishment. A good example is light from the sun, moving air, water from rain, sea tides, and also geothermal heat. At around 2006 approximately 19% of world total energy utilization originated from energy which has the ability to be renewed. The breakdown of such consumption is as shown below.

• Traditional biomass-13%
• Hydroelectricity-3%
• New renewable-2.4%

Currently, the trend is expanding at a very high rate resulting in a portion of around 18% in the generation of electricity and 15% of total world electricity originating from hydroelectricity and then a figure of almost 3.4% coming from new renewable energy. Consequently, Wind power is growing at the rate of 30% annually, with a worldwide installed capacity of 121,000 megawatts (MW) in 2008¹, and is widely used in European countries and the United States. On no yearly basis, the yield of photovoltaic power is approximately six thousand and nine hundred Megawatts. Such sources of power or energy are common in Spain and Germany. The biggest projects of renewable energy sources are found in Brazil. Most of them are advanced especially the ethanol-related source of power which amounts to approximately 19 percent.

Embracing renewable energy is a significant way of reducing the amount of carbon dioxide in the atmosphere. Co₂ is an example of greenhouse gas. There is a need to significantly reduce the production of this gas and this is a global call to action. It is upon every country to devise ways and means of reducing the emission of gas. One approach to doing this is to identify a strategic and reliable plan to lower the dependability of fossils as a source of fuel. To ensure this each country is supposed to have strong national and regional goals aimed at reducing the total emission. For example in the United Kingdom, the government decided to reduce the emissions of carbon dioxide by 20 percent come the year 2010. To cater for this they need to edge more on the production of renewable sources of energy².

Interpolation from energy data in GPG 272³ suggests lighting in homes represents around 6.6% of the capital’s annual carbon emissions. The cost of low-energy light bulbs such as compact fluorescent lamps is coming down all the time, but they are still more expensive than ordinary tungsten filament bulbs. Many poorer households do not relate to the simple fact that investment in more expensive bulbs will save them money in the long term – so they continue to replace tungsten filament bulbs with new ones. Each one typically consumes five and a half times more power than a compact fluorescent lamp alternative. Planning of renewable energy sources in London for example requires critical advancements to lower the foundational need for energy hence reducing carbon dioxide in the environment. This can be achieved by developing good design practices. The other method is by use of low carbon technological sources of energy. For the plan to succeed then demonstration of how this carbon emission can be lowered by another 15% through the use of renewable energy sources is required. This means a single or combination of non-fossil fuelled energy sources located on the site itself. The use of wind farms or the planting of forests elsewhere is not accepted in lieu of on-site renewable. For further information on renewable technologies refer to the Renewable Toolkit⁴.

Sources of renewable energy

The major source of renewable energy is by naturally oriented means which can be renewed at a constant rate. All the various forms of this type of energy are obtained directly from either the sun or heat which is generated from the earth. It can also be obtained from electric current and the heat coming from the solar. The wind is also a major source of energy the same with ocean currents, power from water, that which is obtained from biomass. Other sources include geothermal power and biofuels and hydrogen. All these types of renewable energy have specific characteristics and therefore the question of how and where they can be utilized depends on these characteristics⁵. The description of each source is given below.

Sun (solar energy)

This is the energy/power obtained from the light from the sun and it has very many applications. This may include among others; generation of electric current by use of photovoltaic solar operated cells, concentrating solar power to generate electricity, generation of electricity by means of supplying heat from the sun to convened air which in turn is used in rotating turbines, use of photoelectrochemical cells to generate hydrogen, use of solar panels to heat water for domestic use, supplying heat to a building by use of passive solar building design, solar ovens for heating food and finally for solar air conditioning. The energy from the sun is also referred to as thermal energy⁶.

Wind power

This is whereby the power in moving air is harnessed to run turbines. Currently, wind turbines’ power range between 600KW and 5MW but the most commonly used for commercial purposes is the one with a rated output of between 1.5 and 3 MW. The power to be generated by wind is a function of the speed of the wind. The mathematical relationship is as shown below;

The above function implies that the power generated/output is directly proportional to the speed of the wind. This means that if the speed of the wind increases the power output increases at a very high rate⁷. For an area to be considered for wind power generation there are several factors. The winds in such an area must be strong. Also, the wind must be flowing at a constant rate. Such areas include offshore and high-altitude strategic positions. The technical potential of wind power is almost five the optimum produced energy. This figure is about forty times the demand for electric current. Generally, wind power does not produce carbon dioxide and methane which are greenhouse gases⁸.

Hydropower

Moving water has energy which is in the form of kinetic energy, temperature, and salinity gradient. This energy can be tapped and then consumed. In water, there is quite a good amount of energy since it is almost eight hundred times heavier than normal air. This explains why even a slowly flowing river or sea waves can be tapped and generate a lot of energy in terms of electric current⁹. Water energy can be viewed in different forms. The terms which are commonly used in relation to water energy include;

• Hydroelectric energy- a term usually used in relation to large scale hydroelectric dams
• Micro-hydro systems-electric installations that usually produce about 100 kW
• Dam-less hydro systems- this usually obtain their kinetic energy from either rivers or sea but without using a dam.
• Ocean energy illustrates the entire technology of getting electric current from both ocean and sea.
• Tidal power-this is usually associated with the energy from tides
• Osmotic/salinity gradient power-this is the energy obtained from the potential difference in salt concentration between seawater and water from the rivers flowing into the ocean
• Vortex power-power is obtained by laying barriers in rivers. This results in vortices which are therefore harnessed to produce energy.

Biomass

This is generally the power obtained during the burning of biomass. Biomass has the ability to produce about 10 to 20 MJ/kg of heat energy. Sources of such energy are solid municipal waste, normal wood fuel, and field crops. Many kinds of biomass have a certain percentage of fuel. Cow dung manure has 63 percent of the initial energy consumed by the animal. Power from biomass is harvested through a bioreactor is a cost-effective way of doing away with both human and animal waste. For instance, a farmer can generate enough biogas waste from animal manure which can be used to run the whole farm.

Liquid bio-fuel

This can be divided into two major categories. Bio-alcohol for example fuel from ethanol and oils like bio-diesel and or direct vegetable oil. This kind of fuel can be used in the current vehicles without modifications. A primary advantage of consuming bio-diesel is that it lowers the total carbon dioxide emissions. This is because all the carbon dioxide produced was currently involved during the previous phase of the biomass¹⁰. Consumption of biodiesel fuel is able to lower carbon dioxide production and other pollutants by approximately 30 percent. Biomass is also called bio-matter. There are very many uses of biomass. These may include among others; fuel and to produce bio-fuel. Biomass fuels that are related to agriculture are fuels like bio-diesel and ethanol. Other fuels such as molasses which is commonly produced as waste during sugar processing. The major use of this molasses is in an internal combustion engine where it is subjected to burning to produce enough energy that can be used to drive the engine. The molasses can also be used in boilers. Generally, bio-fuel is composed of in-built chemical energy which when burned it is realized. When the energy is released it can then be converted to other forms of energy depending on the desired end-use.

Geothermal energy

This is the energy derived from the heat deep within the earth. This can be either several kilometers into the crust of the earth or just several meters in a geothermal heat pump in all the places of the planet. The financial expenses for running a geothermal power station or plant are high compared to the initial cost of laying the foundation.

Renewable energy technology

Wind power

There are several characteristics of wind that make it a reliable source of power.

• The condition of wind-wind is generally clean and this translates to the absence of contamination in the system
• Inexhaustible-the source wind power cannot get exhausted. This implies that there is a continuous supply of power given that other factors are held constant.
• It is an indigenous form of energy resource and the fact that it is not under the mercy of any person then is limitless.

The energy from wind can be used to supply electricity to thousands of homes and business units. In comparison to the other form of renewable energy wind power is one of the most growing sources of power. The operating experts in the sector of industry anticipate that if fully harnessed wind power can produce approximately 20 percent of the global industrial energy. Research indicates that there is a possibility of producing more wind power. Since the cost wind turbines that generate electricity will be in a position to compete with that of the other conventional means of power generation. There are two basic designs of wind electric turbines:

• Vertical axis- this is also called egg-beater style and
• Horizontal-axis – which is also known as propeller style machines? It is the popular kind nowadays.

Solar power

The technological know-how of extracting energy from such a source of power or energy uses the potential of the sun and light to emit heat and light. This is the cleanest, most plentiful, and renewable energy source available. The greatest disadvantage of energy from the sun is the ways or methods of stepping-up synthesis. Also, distribution technology to harness the energy from the sun to put down the cost is a major challenge. The energy from the sun can be generated on a distributive means, known as distributed production. The equipment in this case is located on roofs or on mounted fixtures near to where the power is consumed. Various technologies have been devised so as to grab the opportunity of such a source of power¹¹.

Photovoltaic systems

This is whereby solar cells change sunlight into electric currents. The cells are used to ignite instruments that use solar cells.

Solar thermal

This is whereby the light from the sun is harnessed and used for both heating and cooling systems.

Concentrating solar power

This is whereby the light from the sun is converted to a utility-scale suitable for lighting.

Active solar energy systems

The technology to change the light or the heat from the sun to a form in which it can be utilized is expensive

Passive solar

It involves an in-built design and construction structures that are in a position to utilize the benefit of the position of the sun to provide heat and light. Consequently, it also employs devices that provide shading to reduce the amount of heat in a building.

Hydropower

Much of hydropower comes from the energy in dammed water¹². This energy known as potential energy drives a water turbine and a generator. The power output in hydropower depends on several factors; the volume of the water and the height variation between the source and the position from which the water is coming. This height difference brings about pressure and since the pressure in a liquid depends on depth. It implies that the higher the difference the higher the pressure and this amounts to higher output. Hydro energy or power is directly related to the variation in height. This is referred to as the head. Hydroelectric plants without capacity are known as running-river plants since in such cases it is not possible to store water. The main merit of this kind of power is that it minimizes fuel costs. Another benefit is that it lasts for long compared to other sources of energy. Also, the cost of operating such a source is low and it also provides recreational services like swimming among others.

Geothermal power

Generation of geothermal energy needs large and extensive land for closed loops and this amounts to extra cost. Also with such sources, there is a need for though ground work-study prior to the actual drilling. It also requires the services of a professional in that field which adds to more cost. The possibility of a heat rejection system despite running cooling water reduces has the advantage of lowering the heat island effect. Also, geothermal energy is carbon efficient. So as to generate power from a geothermal source there at least three feasible methods can be used. This can be either in form of steam which is a dry, flash method, or binary method. In the plants which utilize dry steam usually the steam is taken from the cracks underground and then consumed in running a turbine which in turn drives a fixed power generator. In other plants instead of direct steam which is dry water is used. In such a case hot water at approximately 200 degrees Celsius from underground is drawn up. The water is then allowed to rise up while boiling is taking place. On reaching the ground hot water is separated to steam by mounted separators. The steam is then directed to a turbine and it is rotated by the same. On the other hand, for plants that use binary technology the hot water is directed into heat exchangers. The water then boils a fluid that is usually organic in nature. It is this fluid that is used to drive the turbine which in turn rotates the generator. The design in all these methods is in a way that the steam which condenses after use together with geothermal fluid that remains is taken back to acquire heat.

Awareness and limitations

Under this topic, the limitations of the major methods of generating renewable energy and their merits and demerits will be highlighted.

Solar energy

Solar collectors require a lot of roof space but they are generally cost-effective. This ensures that house lighting and the provision of hot water can be guaranteed throughout the year. The demerit is that it allows for a minor saving on the emission of carbon dioxide¹³.

Wind energy

For an area to be considered for wind power generation there are several factors. The winds in such an area must be strong. Also, the wind must be flowing at a constant rate. Such areas include offshore and high-altitude strategic positions. The technical potential of wind power is almost five the optimum produced energy. This figure is about forty times the demand for electric current. Generally, wind power does not produce carbon dioxide and methane which are greenhouse gases¹⁴.

Geothermal power

To generate geothermal power there is a need for extensive land for closed loops. This makes it expensive. Also, investigations prior to drilling and also need for a specialist contribute to the higher cost. The possibility of a heat rejection system despite running cooling water reduces has the advantage of lowering the heat island effect. Also, geothermal energy is carbon efficient. Geothermal power usually relies on a trend of generation which is low. This ensures that depletion does not happen but if in any case, it happens the initial temperature can be restored if left without being used for a long time¹⁵.

Conclusions/summary

The power or energy in water on the other hand prevents the dangers of extracting coal. It prevents also the related health effects due to coal pollution. Enough data of approximately fifty and above years concerning the behavior of the station is needed to be taken into account when evaluating the suitable location of a hydrological plant. The number of locations for the hydroelectric power plant is relatively low compared to those plants which can be run using such fuels like fossil and nuclear-related sources and generally, most of the potential areas have been utilized

Other possible locations seem to be very far from populated areas and need large and elaborate lines for transmitting the power. The generation of such power relies on the amount of rain in the water catchments area. This may be drastically lowered during seasons of low rain or melting of snow. This implies that the energy output depends more on changes in climate. In the seasons when there are reduced water levels in the hydroelectric dams those who depend completely on hydropower need to invest extra capital so as to ensure that there is enough electricity. But on the other hand, when it comes to the question of how long it can last the power or energy from water dams cannot stay over the years. This means that the water has to remove one time and be replaced. Consequently, there are occasions whereby the weather changes and also tilting of riverbeds hence altering the ability of water dams to function properly. This reduces the available time for the plant to produce hydropower.

Works cited

Building a Sustainable Future; homes for an autonomous community, GIR 53, DETR

Density Altitude Calculator. 

Eric, M. and Janet, S. (2009) Renewable Global Status Report 2009 Update, Renewable Energy World GPG 272: Lighting for people, energy efficiency and architecture – an overview of lighting requirements and design, September 1999.

Integrating renewable energy into new developments: Toolkit for planners, developers, and consultants: Faber Maunsell for London Energy Partnership, September 2004.

Mark, Z. and Mark, A. (2009), Sustainable development and Energy by the year 2030, Scientific American, p. 43.

Richard S. (2005). European Wind Energy Association. Web.

Richard S. (2005). “Density Altitude Calculator” .

Footnotes

1. Global status report 2007,p8.
2. Mark Z. Jacobson and Mark A. Delucchi. A Path to Sustainable Energy by 2030, Scientific American,2009, p. 43.
3. GPG 272: Lighting for people, energy efficiency and architecture – an overview of lighting requirements and design, 1999.
4. Integrating renewable energy into new developments: Toolkit for planners, developers and consultants: Faber Maunsell for London Energy Partnership, 2004.
5. Building A sustainable Future; homes for an autonomous community’, GIR 53, DETR
6. Daniel Budny and Paulo Sotero, editor (2007).
7. European Wind Energy Association. Web.
8. World Wind Energy Association (2008).
9. Richard Shelquist (2005). “Density Altitude Calculator”. Web.
10. Eric Martinot and Janet Sawin. Renewables Global Status Report 2009 Update, Renewable Energy World, 2009.
11. Building A sustainable Future; homes for an autonomous community’, GIR 53, DETR
12. Richard Shelquist (2005). “Density Altitude Calculator”. Web.
13. Mark Z. Jacobson and Mark A. Delucchi. A Path to Sustainable Energy by 2030, Scientific American,2009, p. 43.
14. World Wind Energy Association (2008)
15. Australian Broadcasting Company. Critics say geo-thermal power not renewable. 2008. Word count: 3,105