Electricity is energy produced by behavior of electrons and protons. Electrical energy or power is not actually or potentially supplied by nature; it has to be produced or generated by various secondary means, converting one form of energy into another. In the modern world, there is an unending need for energy to power electrical appliances, such as fans, lights, communication infrastructures, machines and computing systems, and other devices operated by electrical energy. Nowadays, power can be generated from several renewable and non-renewable energy sources, including fossil fuels, nuclear, geothermal, solar, wind, hydro, wood, biomass, and more.
All these energy sources have pros and cons, but renewable energy sources have comparatively less environmental impact. However, renewable sources, including hydro, solar, and wind, also have certain advantages and disadvantages, which make the decision, about how to produce the energy optimally, even more difficult. Therefore, the in-depth examination of these three renewable power sources will provide an idea about which source works best and in what situations. Though it largely depends on availability of renewable sources in a particular region, the comparison of these sources will give a description about which source is best needed by energy system, when factors like climate, security of supply, and environment are considered.
Hydro power is one of the ancient energy sources; it has been widely used for several hundred years. In ancient periods, energy was generated through water by building hydro wheels to run mills. With time and with technology, hydro power has developed vastly.
Fig1. Hydroelectric Power Generation
Modern age hydro power harnesses the energy of moving water to produce electricity. The electricity produced by hydro power refers to hydroelectricity. It is generated in a hydro power plant, which uses the gravitational force of falling water from higher altitudes or potential energy of water flow in rivers and tidal basins to drive turbine blades. The turbines are further conjugated with huge magnets of an electric generator that produce electricity by converting mechanical energy into electrical energy. The major driving force behind hydro power is dams and water reservoirs (acting like a large battery) that create a large supply of water, used to regulate the energy extraction when needed. The power generated as an output from an electric generator is proportional to the volume and speed of the water falling on turbines. In most countries, electricity needs and demands are moderately fulfilled by hydroelectric power generation. In 2006, nearly 20% of the global electricity consumption was fulfilled with hydro power, making it the most consumed renewable energy source in the world (Maehlum, 2014). It is, by far, the leading renewable source of energy in most countries. As of 2011, over 160 countries were using hydro power capacity, with 11000 hydro power stations having a total global installed capacity of approx. 936 GW. China is the leading hydro power generating country, followed by Canada, USA, and Brazil (World Energy Sources: 2013 Survey, 2016).
- Hydro power plants are utilized to produce base-load electricity and balancing electricity, which can meet the fluctuations in demand.
- Hydro electric generators can instantly switch on and off; therefore, they are one of the most responsive energy sources during varying energy demands, especially in peak seasons.
- A significant quality of hydro power is it produces a great amount of electricity, without relying much on climatic conditions, air current flow, and complex start-up processes.
- Besides reliability and large power output, hydro power sources are flexible, because they are subjected to easy adjustments of water flow and electricity output (Kadar, 2014).
- The operating costs and maintenance costs are typically low, as they are almost entirely automated and have no fuel requirement.
- Hydro power can provide start-up power, control frequency, and follow load, which assists in protecting against system wide failure that could lead to equipment damage (Hydroelectric Power , 2005).
- Also, they have low failure rates and long economic life, i.e., they can be operated for several years due to greater life cycle.
- Despite certain advantages, the main disadvantage of hydro power is it is not appropriate for most locations, due to resource inadequacy.
- It has some environmental consequences. Though it causes no greenhouse emissions, damming of water and modifying water flow greatly affects the river ecosystems and has impingement on landscapes. They present migratory obstacles for underwater species, especially fish. In addition, during reservoir construction, there may be formation of carbon dioxide, causing different environmental impacts (Maehlum, Hydroelectric Energy Pros and Cons, 2014).
- Constructing a hydro power plant is expensive.
- The electricity generation from hydro sources depends on availability of water, so it may prove ineffective at times of drought.
- They operate only at high speeds and require sizeable modification of water resources.
Since ancient times, wind has played a pivotal role as an energy source to drive steam engines. But wind generators for producing electricity were formulated in the 19th century to reduce dependence on hydrocarbons and other sources. Wind energy has been evolved as a major renewable source and is emerging at a rapid rate.
Fig.2 Wind Power Generation
Wind power plants utilize the kinetic energy of flowing air to generate power mechanically. The energy of wind motion is harvested by turbine blades that activate an electrical generator. They have an in-built automated control system, but they require monitoring by manual procedures. The trend of generating electricity from flowing winds is quickly evolving in many countries, as it is one of the eco-friendliest sources of power generation. Wind energy sources constitute about 5% of the total electricity demands. There are typically two types of wind power generation: off-shore and on-shore. Wind power generation is one of the best alternatives to fossil fuels, because it provides environmentally and economically superior output. It is estimated that, by 2050, power generation from worldwide wind energy sources will increased to 18%, from around 3%. The current share of worldwide wind power capacity is around 430 GW, with China and US as the leading wind power producers, followed Germany, Spain, and India.
- Wind power is the eco-friendliest and greenest energy source of electricity generation, as the energy produced is free from harmful gas emissions.
- They perform well in stormy weather conditions.
- The potential of generating power from wind energy sources is massive (over 400 TW); it is 20 times more than global demands (Maehlum, Wind Energy Pros and Cons , 2015).
- They typically have low maintenance and operational costs.
- Wind power sources are space efficient, as they do not require a large area for construction. The land where wind turbines are located can be used for other purposes.
- A highlighting advantage of wind power is they have good potential for residential use, yielding energy savings and protecting residents from power outages (Maehlum, Wind Energy Pros and Cons , 2015).
- Available in various sizes, they have low cost per watt hour and predictable power output (Edvard, 2010).
- The biggest disadvantage of wind power is that wind is sporadic throughout the year; therefore, it cannot meet constant energy demands.
- Initial installation and manufacturing investment is too high in cases of industrial setup and domestic setup.
- It is subjected to generation volatility and unusual behavior in case of frequency deviation (Kadar, 2014).
- Wind power generators create sound pollution as wind turbines are noisy, while operating.
- It may somewhat impose threat to wildlife. Flying creatures, such as bats, birds etc. near wind turbines are in great danger.
Electrical energy generation from solar (sun’s) radiation is a comparatively new idea, rapidly booming in the electricity market. Sun is a colossal source of energy. The energy from the sun could be harnessed using solar (photo-voltaic) cells to convert it into electrical energy. When sunlight composing small particles strikes on photo-voltaic cells, the cells absorb energy. This creates an electrical imbalance in the cell, and particles move faster, creating electricity (Dreier).
Fig3. Solar Power Generation
The two technologies include photovoltaic systems that directly convert sunlight into electricity and concentrated solar power (CSP) that uses the sun’s energy to make steam, which drives turbines to produce electricity. Photo-voltaic technology is widely used, with approx. 98% of installed capacity, whereas CSP share is about 2%. By 2013, the total worldwide installed capacity of solar power was around 142 GW, with Germany being the highest solar power producer, followed by EU, China, US, and Japan (Sawin, 2014). It is estimated to supply approx. 1% of the total electricity consumption, but it is a rapidly growing alternative energy source and is expected to reach 3.5% by 2025 (Solar Generation, 2006).
- It is the most environment friendly source of generation, as it produces no harmful gas emissions or pollution, nor poses any threat to wildlife.
- Solar power sources can be used virtually anywhere, as they can harness electricity in remote locations, not connected to an electrical grid (Bratley, 2010).
- They are the quietest source of electricity generation.
- The maintenance and infrastructure are cost-effective, as they do not require high wiring costs.
- Solar power plants are space efficient, because they are generally installed on roof-tops, so they eliminate the need for a large space.
- They have long use life, and they are not manually monitored.
- The photovoltaic technology has low material consumption, smooth appearance, simple installation, and unobtrusive operation.
- The biggest disadvantage of solar power generation is high initial installation cost. Solar cells are expensive, making it costly to generate power from solar energy.
- The output and efficiency vary in different regions, depending on climatic factors.
- Daylight hours are limited; therefore, solar photo-voltaic cells are constrained by intermittency issues (Solar Power).
- The mechanical resistance of cells is weak.
It has been deduced that no single renewable energy source works supremely at all times and in every situation. All these renewable energy sources have certain environmental impacts. Wind power and solar power are rapidly growing technologies, and in the future, the electricity generation from these sources is likely to increase rapidly. Each power source has specific advantages and disadvantages; hence, they must be used in combination to cover for their drawbacks.