The purpose of this project is to present an overview of renewable energy sources, major technological developments and case studies, accompanied by applicable examples of the use of sources. Renewable energy is the energy that comes from natural resources: The wind, sunlight, rain, sea waves, tides, geothermal heat, regenerated naturally, automatically. Greenhouse gas emissions pose a serious threat to climate change, with potentially disastrous effects on humanity
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The use of Renewable Energy Sources (RES) together with improved Energy Efficiency (EE) can contribute to reducing energy consumption, reducing greenhouse gas emissions and, as a consequence, preventing dangerous climate change. At least one-third of global energy must come from different renewable sources by 2050: The wind, solar, geothermal, hydroelectric, tidal, wave, biomass, etc. Oil and natural gas, classical sources of energy, have fluctuating developments on the international market. A second significant aspect is given by the increasingly limited nature of oil resources. It seems that this energy source will be exhausted in about 50 years from the consumption of oil reserves in exploitation or prospecting. “Green” energy is at the fingertips of both economic operators and individuals. In fact, an economic operator can use such a system for both own consumption and energy trading on the domestic energy market. The high cost of deploying these systems is generally depreciated in about 5-10 years, depending on the installed production capacity. The “sustainability” condition is met when projects based on renewable energy have a negative CO2 or at least neutral CO2 over the life cycle. Emissions of Greenhouse Gases (GHG) are one of the environmental criteria included in a sustainability analysis, but is not enough. The concept of sustainability must also include in the assessment various other aspects, such as environmental, cultural, health, but must also integrate economic aspects. Renewable energy generation in a sustainable way is a challenge that requires compliance with national and international regulations. Energy independence can be achieved: – Large scale (for communities); – small-scale (for individual houses, vacation homes or cabins without electrical connection).
Keywords: Environmental Protection, Renewable Energy, Sustainable Energy, The Wind, Sunlight, Rain, Sea Waves, Tides, Geothermal Heat, Regenerated Naturally.
Introduction
The purpose of this project is to present an overview of renewable energy sources, major technological developments and case studies, accompanied by applicable examples of the use of sources.
Renewable energy is the energy that comes from natural resources: The wind, sunlight, rain, sea waves, tides, geothermal heat, regenerated naturally, automatically.
Greenhouse gas emissions pose a serious threat to climate change, with potentially disastrous effects on humanity. The use of Renewable Energy Sources (RES) together with improved Energy Efficiency (EE) can contribute to reducing energy consumption, reducing greenhouse gas emissions and, as a consequence, preventing dangerous climate change.
At least one-third of global energy must come from different renewable sources by 2050: The wind, solar, geothermal, hydroelectric, tidal, wave, biomass, etc.
Oil and natural gas, classical sources of energy, have fluctuating developments on the international market. A second significant aspect is given by the increasingly limited nature of oil resources. It seems that this energy source will be exhausted in about 50 years from the consumption of oil reserves in exploitation or prospecting.
“Green” energy is at the fingertips of both economic operators and individuals.
In fact, an economic operator can use such a system for both own consumption and energy trading on the domestic energy market. The high cost of deploying these systems is generally depreciated in about 5-10 years, depending on the installed production capacity.
The “sustainability” condition is met when projects based on renewable energy have a negative CO2 or at least neutral CO2 over the life cycle.
Emissions of Greenhouse Gases (GHG) are one of the environmental criteria included in a sustainability analysis, but is not enough. The concept of sustainability must also include in the assessment various other aspects, such as environmental, cultural, health, but must also integrate economic aspects.
Renewable energy generation in a sustainable way is a challenge that requires compliance with national and international regulations.
Energy independence can be achieved:
Large scale (for communities)
Small-scale (for individual houses, vacation homes or cabins without electrical connection)
Today, the renewable energy has gained an avant-garde and a great development also thanks to governments and international organizations that have finally begun to understand its imperative necessity for humanity, to avoid crises and wars, to maintain a modern life (we can’t go back to caves).
Materials and Methods
The Micro-Hydropower Potential
Hydroelectric power comes from the action of moving water. It can be seen as a form of solar energy because the sun feeds the water circuit in nature. Within this circuit, the water from the atmosphere reaches the surface of the earth in the form of precipitation. Part of it evaporates, but much of it penetrates the soil or becomes flowing water to the surface. Rainwater and melted snow finally end up in ponds, lakes, reservoirs or oceans where evaporation takes place permanently.
Water resources due to inland rivers are estimated at about 42 billion cubic meters per year, but under unchecked storage, it can only account for about 19 million cubic meters per year due to fluctuations in river flows.
Low-power hydropower plants are a major contributor of renewable electricity at European and world level. Worldwide, it is estimated that there is an installed capacity of 47,000 MW, with a potential – technical and economic – close to 180,000 MW.
Low-Power Hydropower Plants (HMP) are powered by natural water flow, i.e., it does not involve large-scale water capture and therefore does not require the construction of large dams and reservoirs, although they help where they exist and can be used easily. There is no international definition of the HMP and the upper limit varies between 2.5 and 25 MW depending on the country, but the 10 MW value is generally accepted and promoted by European Association of Low Power Hydro Power Plants (ESHA).
Low power plants are one of the most reliable and cost-effective technologies for producing clean electricity.
In particular, the key advantages of HMPs to wind-based, wave-based or solar power plants are:
High efficiency (70-90%), by far the best of all energy technologies
A high capacity factor (usually> 50%), compared to 10% for solar energy and 30% for wind power
High predictability, depending on yearly rainfall patterns
Low rate of variability; The energy produced varies only gradually from day to day (not from one minute to the next)
Good correlation with demand (eg output is maximum in winter)
It is a sustainable and solid technology; Systems can be designed to work for over 50 years
HMPs are also environmentally friendly. Most of the time, they work on the natural course of water. Therefore, this type of water-based installation does not have the same negative environmental effects as large hydropower plants.
Small hydropower plants can be located either in mountainous areas where rivers are fast or in low-lying areas with large rivers. The four most common types of micro-power plants are presented below.
For large and medium fall schemes, channel and duct combinations are used. If the terrain is injured, the construction of the canal is difficult and then only the forced duct that can sometimes be buried is used. In the barrage arrangements the turbines are placed in or in the immediate vicinity of the dam, so that there is almost no need for the channel or the pipeline.
Another option of placing the microturbines is to use the flows from the water treatment plants.
The objective of a hydroelectric system is to convert the potential energy of the volume of water flowing from a certain height into electricity at the bottom end of the system where the power plant is located. The water level difference, known as “fall”, is essential for the production of hydroelectricity; The simple rapid flow of water does not contain enough energy to produce significant electrical energy than on a very large scale such as coastal submarine currents. That is why two indicators are needed: Q water flow and H dropping. It is generally better to have a larger drop than a higher flow, because smaller equipment can be used.
Grossfall (H) is the maximum vertical distance between upstream and downstream water levels. The actual fall seen at the turbine will be somewhat lower than the gross fall, due to the loss of water in and out of the system. This low fall is called the Net Fall.
Flow rate (Q) is the volume of water passing into the unit of time, measured in m3/s. For small systems, the flow rate can also be expressed in liters/second, where 1000 l/s = 1 m3/sec. Depending on the fall, hydroelectric plants can be classified into three categories:
Large drop: Over 100 m
Average fall: 30-100 m
Reduced fall: 2-30 m
These categories are not strict, but are only a possible ranking system for locations.
Hydroelectric installations can also be defined as:
Installations on the water wire
Installations with a power plant located at the base of a dam
Integrated systems on a channel or in a water supply pipe
Generally, large-scale locations are less expensive to develop than small-fall ones, because for the same level of energy produced, the flow required by the turbine will be lower than hydro-technical constructions. For a river with a relatively high slope in a sector of its course, the level difference can be used by conducting part or all of the course and returning it to the river bed after passing through the turbine. The water can be brought directly from the source to the turbine via a pressure pipe.
Hydroelectric turbines convert water pressure into mechanical power to the shaft, which can be used to drive an electric generator or other equipment. Available electricity is directly proportional to the fall and flow rate.
The best turbines can have hydraulic efficiency in the order of 80-90% (higher than any other driving force), although it decreases with size.
The main component of a small hydropower plant is the hydraulic turbine. All of these turbines convert the falling water energy into kinetic rotation shaft energy, but confusion often arises as to which type of turbine should be used depending on the circumstances. The choice of the turbine depends on the location characteristics, especially the drop and flow, plus the desired generator speed and if the turbine has to operate under low flow conditions.
There are two main types of turbines, called “impulse” and “reactive”.
The impulse turbine converts the potential energy of the water into kinetic energy through a jet that comes out of a nozzle and is projected onto the rotor cups or blades.
The reaction turbine uses pressure and water speed to create energy. The rotor is completely immersed and the pressure and speed drop from intake to exhaust. By contrast, the rotor of a pulse turbine operates in air, driven by a jet (or jets) of water.
There are 3 main types of impetus turbines: Pelton, Turbo and Cross Flow (or Banki). The main 2 types of reaction turbines are helical (Kaplan) and Francis.
Most existing turbines can be grouped into three categories:
Kaplan and helical turbines
Turbine Francis
Pelton turbines and other impulse turbines
Kaplan and propeller turbines are axial flow turbines, generally used for small falls (typically less than 16 m). The Kaplan turbine has adjustable blades and may or may not have an adjustable stator head unit. If both the rotor blades and the steering gear are adjustable, we are dealing with a ‘double-tuned’ turbine. If the directing device is fixed, we are dealing with a ‘simple tuned’ turbine. In the conventional version, the Kaplan turbine has a spiral chamber (either steel or reinforced concrete); the flow enters radially inward and makes a straight angle before entering the rotor in the axial direction. If the rotor has fixed blades, the turbine is called a propeller turbine.
Propeller turbines may have mobile or fixed devices. Turbines with nipples are used only if flow and fall are practically constant.
Bulb and tubular turbines are derived from the Kaplan and helical variants, where the flow enters and exits with minor directional changes. In the Bulb turbine, the multiplier and the generator are located in a submerged capsule. The tubular turbines allow several arrangements, namely: Straight-angle transmission, Straflo turbines with S-ducts, belt drive generators, etc. Versions with straight-angle transmission are very attractive, but they are only manufactured to a power of 2 MW.
Francis turbines are radial-flow turbine engines with fixed rotor blades and mobile guides used for mid-fall. The rotor is made up of cups with complex profiles. A Francis turbine typically includes a spiral cast iron or steel chamber to distribute water throughout the perimeter of the rotor and a series of guide elements to adjust the flow of water into the rotor.
Pelton turbines are single or multiple jet turbines, each jet being designed with a needle nozzle to control the flow. They are used for medium and large falls. The nozzle axes are on the rotor plane.
The cross-flow turbine, sometimes called the Ossberger turbine, after a company that has been manufacturing it for over 50 years, or the Michell turbine is used for a wide range of falls, overlapping with Kaplan, Francis and Pelton turbine applications. This type is very suitable for a high-flow and low drop stream.
Turbo can operate under a fall ranging from 30-300 m. Like the Pelton turbine, it is a pulsating turbine, but the blades have a different shape and the water jets hit the plane of the rotor at an angle of 20°. The water enters the rotor through one side of it and goes out through the other. The high turbo turbine speed due to its smaller diameter than other models makes it more likely to directly engage the turbine and generator. A turbine of this type may be suitable for average falls where a Francis turbine could also be used. But, unlike Pelton, the water passing through the rotor produces an axial force that requires the installation of a transmission shaft on the shaft.
The type, geometry and dimensions of the turbine will be fundamentally conditioned by the following criteria: