In this article, you will get all information about geothermal energy as renewable energy. So Lets discuss more in detail.
Geothermal Energy Resource’s Six categories And Their Pros & Cons
We have divided Geothermal energy resources into six categories. Let’s discuss them below.
Normal Geothermal Gradient
In the locations where a normal geothermal energy gradient exists, the temperature of rocks becomes hot enough that provides useful energy with the help of working fluid like water. This method is technically feasible to generate electricity but it is not economically viable.
Hot Dry Rock as a Geothermal Energy
hot dry rocks are the same as the geothermal gradient but they provided excess temperature. In this method to elevate temperature, hydraulic or explosive techniques, that are to fracture rocks. Then they use working fluid. This technology is still in its early stages and its economic feasibility is also uncertain.
Hot Water Reservoirs
It occurs due to the water as working fluid undergoes and reaches the geothermal energy graduates. It produces heat that helps to produce power. Hot water reservoirs are used as the direct sources of heating and producing electricity. And for the latter purpose, natural steam deposits are so one of the choices.
Natural Steam Reservoirs
When little or no water to associate with the collaboration of geothermal gradients, it produces a natural steam reservoir with a very high temperature. These are rare resources and until now only 2 of them was found. Hot water reservoirs and natural steam reservoirs have been exploited naturally.
Geo-Pressurized Regions
Depressurized resources came into existence with the dissolution of methane gas with water. From these types of resources, we can produce thermal as well as chemical and mechanical energy. But these are also not economically feasible. But researchers are trying hard to make it possible in the future.
Molten Magma:
Molten Magma is too unstable and unpredictable to extract geothermal energy.
A most common type of geothermal energy plant. The principle behind the Binary geothermal power plant.
Flash steam plants are the most common type of geothermal power generation plant nowadays. In a binary geothermal power plant, the hot water or steam extracted from the geothermal energy reservoirs drives the turbines to produce electricity. Furthermore, flash steam plants also have the same production cycle. In a binary cycle power plant, the thermal energy so water or steam is transferred to the second working fluid energy with the heat of a heat exchanger. This working fluid exists in a closed system and is converted into vapors in the heat exchanger. These vapors are then used to drive the turbines and again returned to the liquid.
The principle behind OTEC. Operational differences between the three types of OTEC systems for Geothermal Energy
OTEC’s basic principle depends on the temperature gradients between the surface and very deep water in the ocean that is situated only in the topical regions. Due to this principle, the conversion of thermal energy in the ocean to mechanical energy relies totally on cold reservoirs into which excess heat can be transferred.
Open Cycle Systems:
This system uses sweat water as a working fluid and enters into the left side of the diagram and is converted into vapors then sweat water is mixed to drive pressure and run turbines.
Closed Cycle Systems:
In this system, the working fluid can be a substance that is compatible with temperature and pressures present in the system. So, these substances like ammonia are mixed with sweater warm water in a closed system to heat the working fluid. When the heat reaches the boiling point it vaporized and then the vapors are used to drive the turbines to produce electricity.
Hybrid system:
It has its operations the same as in a closed cycle system. However, the warm seawater used to vaporize the working fluid is vaporized; this vaporized working fluid runs the turbines. Then, again this vaporized water is re-condensed to produce desalinated water and reused again.
A tidal generating station (barrage design) produces electricity at an efficiency of 40% during the falling tide (only) from a basin that is 20 km2 in area with a tidal range of 10 m. Energy is stored during the rising tide and distributed uniformly in time. What is the average power output?
P= (20*10*10^6m^2) x (10m)^2 x (9.8m/s^2) x 1025kg/m^3 /12.4*3600s/h
P= 4.8GW
The Pelamis is an excellent device for harvesting wave energy. It consists of four hinged sections and has a total length of 120 m.
One of the best non-traditional energy sources for producing power is wave energy. Mechanical conversion can turn wave energy into electricity. The most popular technology for turning wave energy into electricity is the Pelamis wave converter. “Salter’s Duck,” created by Professor Stephen Salter of the University of Edinburgh, helped to establish the field of wave energy research. The duck follows the waves up and down with an efficiency of around 90%. Thus, The Pelamis has four main tube segments that are to connect with hinged joints. It was cylindrical. Each section weighs 750t when fully ballasted and is 120m long and 3.5m broad. The machine runs partially underwater and generates electricity from the motion of the hinged joints caused by waves. Hydraulic rams will use to counteract the power. So, Hydraulic rams, which provide high-pressure oil to hydraulic motors via smoothing accumulators, withstood the force.
Comparing and contrasting high-head/low-head hydro systems. What are the basic types of turbines for hydropower?
Pressure and water flow work together to create power in a reaction turbine. In order to prevent the blades from getting stuck separately. A runner will position immediately in the water stream. So, the most prevalent kind now utilize in the United States are reaction turbines, which are often employed at sites with lower heads and larger flows. The runner of a propeller turbine typically contains three to six blades. All the blades are continually in touch with water. Think of a pipe that a boat propeller is running through. The pressure within the pipe is constant; otherwise, the runner wouldn’t be in balance.
The blades’ pitch may be permanent or adjustable. James Francis, a British-American engineer, created the Francis turbine, the first hydroelectric turbine of the modern era, in 1849. The runner of a Francis turbine contains fixed blades, often nine or more. Just above the runner and all around it, when it falls through, the blades begin to spin. The runner is one of the main parts, along with a scroll case, wicket gates, and a draught tube. In an impulse turbine, the velocity of water moves the runner typically which discharges at atmospheric pressure. On the runner, each bucket receives a stream of water. The water pours out the bottom of the turbine’s downside since there is no suction there.
The Hoover Dam has a head of 180 m and a maximum output capacity of 2080 MWe. If the generator efficiency is 90% what is the flow rate in m3/s at maximum capacity? (show the calculations)
H= 180m
P=2080MWe
ρ= 90%
V=?
The power generated is P=mgh=ρV×gh
2080=0.90V * 9.8(180)
2080 =0.90V* 189.8
2080/189.8= 0.90V
10.96=0.90V
10.96/0.90=V
12.18m^3/s=V
What is Betz’s limit? Explain its relevance and factors involved in maximizing wind-turbine efficiency
The wind turbine’s maximum speed, which is necessary to produce power, is called the Betz limit. The Betz limit is 59.3%, which is virtually unattainable. The maximum efficiency of a wind turbine is around 45%. The wind will slow down as it moves through the turbine by the movement of the blades. It allows wind energy to be transformed into electricity. To ascertain the effectiveness of the wind turbines, the Betz limit will measure. However, the generation of power at a steady speed, air density, and the radius of the blades are all variables in obtaining optimal wind turbine efficiency.
Compare and contrast heat engines versus Photovoltaic devices of energy from the sun for geothermal energy
While the science and the specifics may be challenging, the distinction between the two is very straightforward. A solar PV system is one in which energy will produce when light strikes a solar panel. A solar thermal system, on the other hand, takes in the sunshine and utilizes the energy to heat your workplace or water. Regarding power plants, the goal of both PV and thermal systems is the generation of energy. Thermal systems heat a fluid (such as water, oil, steam, or air) that will power a steam engine, gas turbine, or something similar, whereas PV systems produce that electricity directly from solar energy. So, the voltage and AC form of the power will send to the grid.
Evaluate the usefulness of solar heating on the basis of heating requirements for a building
The term “solar heating” refers to a system that stores sunshine for later use in industry. Solar heating is beneficial for heating solar panels on top of buildings by employing non-conventional thermal energy. However, Propylene glycol helps in solar heating systems to transfer heat and circulate hot water in the tank. Solar systems rely on sunlight to function. Thus, to utilize active solar heating to heat your home, panels of tubes or pipes, or a radiant slab system, we place them in the walls or floors. According to Understand Solar, when we heat the liquid, it will circulate throughout the house and radiate heat out from the tubes to heat the air in the space.
True False Statement On Geothermal Energy
- False: Solar constant is ~ 1267 W/m2.
- True: Passive solar heating relies on the optical properties of windows.
- True: Geothermal energy production is an example of a heat pump.
- False: In warmer climates, heating degree days are used to measure the energy requirements for air-conditioning.
- False: Optimal efficiency of the passive solar heated house depends on incorporating north-facing windows.
- True: Carnot η limits the solar-to-electric η through heat engines.
- True: The size of the band gap in a PV cell depends primarily on the material used.
- False: A two-blade wind turbine is intrinsically less efficient than a 3-blade design.
- True: The maximum theoretical efficiency that can be achieved by a wind turbine is ~ 59%.
- False: Your body’s power output is ~ 100 Mw.
- True: To extract optimal wind energy, turbines should be spaced in accordance with rotor diameter.
- True: Hydroelectric energy generation η can be as high as 85-90%.
- False: The Kaplan water turbine is the most commonly used in the electric power industry.
- True: Grand Coulee Dam is one of the best examples of a Low Head System.
- False: Wave energy is primarily a manifestation of wind energy.
- True: Oscillating Water Columns to harness wave power are primarily located offshore.
- True: The Pelamis has been one of the most successful devices for harvesting wave energy.
- False: The Wave Dragon is an Oscillating Water Column (OWC) device.
- False: Tidal energy is less predictable than wave energy.
- True: In principle the operation of a tidal lagoon is similar to a barrage system.
- False: Underwater turbines use the potential energy associated with tidal currents.
- False: Water turbines are generally vertical-axis machines.
- True: Overall 𝜂𝜂 of “Ocean Thermal Energy Conversion” systems is very low.
- True: The possibility of utilizing geothermal energy is the greatest at or near plate boundaries.
- True: Most geothermal energy electricity generation uses hot water as an energy source.