Wind power is a form of energy that uses wind power to generate electricity. It is achieved through a wind turbine generator. These generators transform airflow into power through a system of rotor blades and other mechanical and electrical components.
The power is transferred using a shaft to a generator which then converts it into electrical energy. With wind energy, it is feasible to deliver a consistent kilowatt hour of energy to the power grid when the wind is blowing to light up cities and homes and to supply energy to industries.
But what if one needs electricity, but the wind isn’t strong enough? In the past, this condition had to be met with another form of energy, either renewable or non-renewable. But today, it is already possible to use wind energy even when the wind is not blowing.
How is Wind Power Distributed?
In transmission substations, wind farm electricity is stepped up to a high voltage of 150-800 kV after traveling to a wind farm. The power is distributed along the electricity grid power lines to the consumer.
Wind farms typically distribute the power directly to the electrical grid. When more energy is produced than is needed, turbine speeds are slowed to sub-optimal levels without energy storage.
How can Wind Energy be Stored?
The dramatic growth of the wind energy sector has led utilities to push for large-scale capabilities to store surplus clean electricity and deliver it on demand when winds are not that strong. Through several different storage processes, excess energy can be stored and used at a later date. Let’s look at the options available for storage.
There are three important types of large-scale Battery Energy Storage. Lead-acid (LA), nickel-cadmium (NiCd), sodium-sulphur (NaS).They work identical to traditional batteries, except on a large scale, i.e., two electrodes are immersed in an electrolyte, which allows a chemical reaction to generate current when required. These batteries are well suited to trickle chargers and have a high charging efficiency.
Even when the wind is not blowing, the batteries enable the storage of wind energy for later usage when there is a need or when the electrical system calls for it, but the wind is not that strong.
Due to declining costs and steady efficiency gains, battery-powered energy storage are helpful for large-scale applications in advanced economies and domestic use on sparsely linked grids, such as those on islands.
Compressed Air Energy Storage (CAES)
Air compressed by wind turbines can be kept in enormous above-ground tanks or underground tunnels. Direct expansion into a compact air motor is one way to utilize compressed air as needed. Additionally, it can be pumped into an internal combustion turbine and burned along with fuel to provide mechanical energy that powers a generator.
The CAES system consists of a compressor, a high-pressure turbine, a low-pressure turbine, and a powerful engine that drives a generator. Traditional gas turbines use a high percentage of gas to compress the air as it occurs.
CAES uses off-peak electrical energy extracted from the grid to pre-compress the air (instead of using gas from the gas turbine plant) and store it in a large storage tank.
When the gas turbine generates electricity during peak hours, compressed air is released from the storage and used in the gas turbine cycle. Thus, cheap electricity is used instead of expensive gas, which saves money in the long run.
Large-scale storage is accomplished with CAES. Plants typically can go from 0% to 100% in less than 10 minutes, from 10% to 100% in around 4 minutes, and from 50% to 100% in about 15 seconds. Because of this, it is perfect for serving as a sizable sink for bulk energy supply and demand. It can also handle repeated start-ups and shutdowns.
Hydrogen Fuel Cell Storage
Additional power can be stored using hydrogen fuel cells. The energy produced by the wind turbine is used to electrolyze water using a hydrogen generator. The resulting hydrogen is then stored, and a fuel cell power system transforms it back into electricity when needed.
For future use, the hydrogen is preserved while the oxygen is released into the environment. Because of the high cost, only a small portion of the hydrogen generation comes through electrolysis. The best choice for future production is combining electrolyser units with renewable energy sources like wind. Below are the ways hydrogen is stored.
- Hydrogen can be compressed into containers or underground reservoirs. This is a relatively simple technology, but the energy density and efficiency (65–70%) are low.
- The hydrogen can be liquefied by pressurizing and cooling. Although the energy density is improved, it is still four times less than conventional petrol. Also, keeping the hydrogen liquefied is very energy intensive, as it must be kept below 20.27 K.
- Metal hydrides: Nanostructured carbons and clathrate hydrate absorb molecular hydrogen. It is possible to store and transport hydrogen easily by absorbing it in these materials. Parent material is separated from the hydrogen when needed.
The cost of wind-generated energy is falling, leading to a rapid increase in wind farm construction. Several innovative energy storage projects are also in the development or operating stage. Traditionally, wind energy lacks instant electricity generation, which is its main drawback.
Wind energy storage will always face significant financial challenges, as it is nearly always quite expensive to create new energy storage facilities. However, as energy storage technology advances and costs are expected to decline, this won’t be the case forever. Furthermore, fossil fuel facilities are limited in supply and cannot wholly replace wind-generated electricity.