Storing the Energy

Since the industrial revolution, our energy consumption has been continuously increasing. And with new technologies, we need more energy. Until now we are getting energy from burning fossil fuels and some from nuclear power plants. But it is causing the problems like air pollution, Global warming, and damage to the atmosphere and environment. As we concern with all the risks created by these traditional methods, we found Renewable energy. For a long time, Renewable energy is building hope to save the environment.

Renewable energy providing us with safe, green, and pollution-free energy for so many years. We have built so many hydropower plants, wind farms, solar plants, geothermal energy plants, bioenergy plants, etc. but we can’t replace them with traditional energy. Traditional energy has a negative impact on the environment but it is cheaper than renewable energy, and most importantly we can make it whenever we need it. In the case of renewable energy, we are using natural resources like sunlight, wind, and rain and these are not constant. There are more options like ocean waves, geothermal vents, and bioenergy, but it comes with different problems. We will see it later.

Although renewable energy gives us pollution-free energy, it comes with its own problems like infrastructure cost, land for the plants, and most important Continuity. As we see earlier renewable energy in not constant means we can’t get the same amount of sunshine for an entire day, month or year, as like this we can’t get constant wind flow. And the most important factor is electricity demand. we need most of electricity in peek hours, in morning and in the evening. And we can’t say if the sources will give us renewable energy when we need it the most.

This issue creates a big hurdle to making renewable energy sustainable. With growing economies and technology our energy consumption is increasing day by day. And we can’t make batteries that can store that much electricity.

But what if we can store the energy instead of electricity?

“Energy cannot be created or destroyed; it can only be changed from one form to another.” (Albert Einstein).

This sentence by Albert Einstein plays a major role to make this possible. In recent times this concept is making its place to make renewable energy sustainable. Scientists are searching for different ways to store this energy. Many foundations were created to try different concepts for storing this energy. Let’s see some of the concepts.

1. Pumped Hydroelectricity Energy Storage –

This concept has been implemented in some places. as we know that most of the electricity we are using is come from hydroelectric plants. We are storing water in mass quantities and releasing it to make electricity which can be used as we need. Using this concept we can store the renewable energy.

Pumped hydropower storage uses the force of gravity to generate electricity using water that has been previously pumped from a lower source to an upper reservoir. 

The water is pumped to the higher reservoir at times of low demand and low electricity prices. At times of high demand – and higher prices – the water is then released to drive a turbine in a powerhouse and supply electricity to the grid.

A closed loop or ‘off-river’ pumped storage hydropower project
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The energy storage capacity of a pumped hydro facility depends on the size of its two reservoirs, while the amount of power generated is linked to the size of the turbine.

A facility with two reservoirs roughly the size of two Olympic swimming pools, and a 500-metre height difference between them, could provide a capacity of 3-megawatts (MW) and store up to 3.5 megawatt hours (MWh) of electricity.

There are two main types of pumped hydro:

·      Open-loop: with either an upper or lower reservoir that is continuously connected to a naturally flowing water source such as a river.

·      Closed-loop: an ‘off-river’ site that produces power from water pumped to an upper reservoir without a significant natural inflow.

The IHA (International Hydropower Association) is one of the organization that working for sustainablity of renewable energy.

La Muela Hydroelectric Power Complex, Spain. Photo- Courtesy of Iberdrola
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This is an efficient way to store the renewable energy. But for building this kind of infrastructure, we need identical palaces with large area to build.

Read this: The 10 Largest Pumped-Storage Hydropower Plants in the World

2. Compressed Air Energy Storage

Compressed air energy storage, or CAES, is a means of storing energy for later use in the form of compressed air. CAES can work in conjunction with the existing power grid and other sources of power to store excess energy for when it is needed most, such as during peak energy hours.

Here’s how the A-CAES technology works: Extra energy from the grid runs an air compressor, and the compressed air is stored in the plant. Later, when energy is needed, the compressed air then runs a power-generating turbine. The facility also stores heat from the air to help smooth the turbine process later on.

Compressed air energy storage plant concept.
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While the efficiency of similar systems has hovered around 40 to 50 percent, the new system from Hydrostor, a major global leader in building hydroelectric storage, reportedly reaches 60 percent, according to Quartz.

Hydrostor, a private company founded in 2010 and based in Toronto, Canada, is the world’s leading developer of utility-scale energy storage facilities. It will store compressed air in a reservoir that’s partly filled with water to balance out the pressure. The whole system will hold up to 12 hours of energy for the grids where the two plants are planned. (The first plant will be built in Rosamond, California, while the second location is to be determined.)

The Goderich A-CAES Facility, located in Goderich, Ontario, Canada.
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3. Thermal Heat Storage

 Modern solar thermal power plants, which produce all of their energy when the sun is shining during the day. The excess energy produced during peak sunlight is often stored in these facilities – in the form of molten salt or other materials – and can be used into the evening to generate steam to drive a turbine to produce electricity. Alternatively, a facility can use ‘off-peak’ electricity rates which are lower at night to produce ice, which can be incorporated into a building’s cooling system to lower demand for energy during the day.

Gemasolar Concentrated Solar Power (CSP) plant
  • Pumped Heat Electrical Storage (PHES)

In Pumped Heat Electrical Storage (PHES), electricity is used to drive a storage engine connected to two large thermal stores. To store electricity, the electrical energy drives a heat pump, which pumps heat from the “cold store” to the “hot store” (similar to the operation of a refrigerator). To recover the energy, the heat pump is reversed to become a heat engine. The engine takes heat from the hot store, delivers waste heat to the cold store, and produces mechanical work. When recovering electricity the heat engine drives a generator.

  • Liquid Air Energy Storage (LAES)

Liquid Air Energy Storage (LAES), also referred to as Cryogenic Energy Storage (CES), is a long duration, large scale energy storage technology that can be located at the point of demand. The working fluid is liquefied air or liquid nitrogen (~78% of air). LAES systems share performance characteristics with pumped hydro and can harness industrial low-grade waste heat/waste cold from co-located processes. Size extends from around 5MW to 100s+MWs and, with capacity and energy being de-coupled, the systems are very well suited to long duration applications. 

4. Flywheel Energy Storage

Mechanical energy storage systems take advantage of kinetic or gravitational forces to store inputted energy. While the physics of mechanical systems are often quite simple (e.g. spin a flywheel or lift weights up a hill), the technologies that enable the efficient and effective use of these forces are particularly advanced. High-tech materials, cutting-edge computer control systems, and innovative design makes these systems feasible in real-world applications.

Flywheel energy storage systems (FESS) employ kinetic energy stored in a rotating mass with very low frictional losses. Electric energy input accelerates the mass to speed via an integrated motor-generator. The energy is discharged by drawing down the kinetic energy using the same motor-generator. The amount of energy that can be stored is proportional to the object’s moment of inertia times the square of its angular velocity. To optimize the energy-to-mass ratio, the flywheel must spin at the maximum possible speed. Rapidly rotating objects are subject to significant centrifugal forces however, while dense materials can store more energy, they are also subject to higher centrifugal force and thus may be more prone to failure at lower rotational speeds than low-density materials. Therefore, tensile strength is more important than the density of the material. Low-speed flywheels are built with steel and rotate at rates up to 10,000 PRM.

Generation 4 Flywheel
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More advanced FESS achieve attractive energy density, high efficiency and low standby losses (over periods of many minutes to several hours) by employing four key features: 1) rotating mass made of fiber glass resins or polymer materials with a high strength-to-weight ratio, 2) a mass that operates in a vacuum to minimize aerodynamic drag, 3) mass that rotates at high frequency, and 4) air or magnetic suppression bearing technology to accommodate high rotational speed. Advanced FESS operate at a rotational frequency in excess of 100,000 RPM with tip speeds in excess of 1000 m/s. FESS are best used for high power, low energy applications that require many cycles.

Additionally, they have several advantages over chemical energy storage. They have high energy density and substantial durability which allows them to be cycled frequently with no impact to performance. They also have very fast response and ramp rates. In fact, they can go from full discharge to full charge within a few seconds or less. Flywheel energy storage systems (FESS) are increasingly important to high power, relatively low energy applications. They are especially attractive for applications requiring frequent cycling given that they incur limited life reduction if used extensively (i.e., they can undergo many partial and full charge-discharge cycles with trivial wear per cycle).

FESS are especially well-suited to several applications including electric service power quality and reliability, ride-through while gen-sets start-up for longer term backup, area regulation, fast area regulation and frequency response. FESS may also be valuable as a subsystem in hybrid vehicles that stop and start frequently as a component of track-side or on-board regenerative braking systems.

Know more about FESS

Source: Energy storage associations

These are some energy storage systems. There are more ways to store energy and use it as we need. More and more concepts are making their way to make renewable energy sustainable. In furure it can be gamechanger.

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