Energy Storage Systems (ESS)
Generally, the energy storing device is defined as a storing device that is
used to store direct energy generated from energy sources like the energy
generated from solar panels and wind turbines as well as other sources that
generate electricity. It is also defined as the storage of the element or
substance to be used later as a source of generating energy when the energy
sources are not available like steam, heat, cold, compressed air, and
Hydrogen storage
tanks.
Energy storage system |
The most important use of energy storage in electrical engineering is using
these energy storing devices in emergency cases like power cuts or the
condition of electrical power instability in critical places or with critical
equipment through an Uninterrupted Power Supply (UPS) where the batteries are
used.
Energy storage is used widely with
renewable energy
sources where these sources are not available all the time. For example, the
electrical power generated from
solar panels
and wind turbines is available only during daylight and when windy weather
with a specified minimum speed is available.
What are the advantages of energy storage devices?
Taking the electricity energy storage or the storage of the materials used
in electricity generation as a reference and besides the main target of the
energy storage devices mentioned in the introduction, it has a lot of other
significant advantages listed as:
- It can be used easily without problems where you want it. That is because no need to transfer it to its final place. The transfer is only for the first time without any continuous transportation difficulties especially if some of them need special treatment during transportation.
- The filling or charging /discharging process of the storage element could be easily done by the application that is using it and in the same place as batteries or supercapacitors so no need to transfer the storage in or out for the charging cycle.
- It makes systems more reliable and more flexible by balancing the system during unstable sources or sharp changes in process operation due to fast load change. This may widely exist also with the use of renewable sources.
- It is considered an environment friend as it has a minor bad effect on the surrounding environment. That is because most of the storage is used with or in renewable sources.
- It has a significant impact on costs by saving the electricity bill or when losing electrical power at the time that it is needed. It also decreases the operation cost when transferring the energy through an overhead transmission line (OHTL) or the national grid.
- Easy for energy management systems and applications when it is used with another power system where the haul system is called a hybrid power system like using (PV) power system, wind turbine system, Battery system, fuel cell system, and finally, the supercapacitor system. The most known application is the hybrid vehicles.
What are the disadvantages of the Energy Storage Systems (ESS)?
- High initial cost especially with the use of renewable energy sources. With renewable energy sources, the time of using the ESS is considerably long (during the night with PVs and non-windy days with wind turbines), and that will affect the size of the storage devices, and as a result, it will affect the initial cost of the project will be increased. The payback of the project should be calculated and considered.
- ESS Limited Lifetime: as the charging/ discharging of the storage is affecting the lifespan of the device, it needs to be replaced after a certain time which leads to replacement cost increases. The replacement downtime may cause production losses.
- As the size and capacity of the energy storage device are limited, large areas for large-scale projects are needed.
- Self-discharging inside the storage prevents the usage of the energy storage device’s full-capacity element
What properties should the energy storage have?
- Size and capacity.
- Performance and efficiency.
- Cycle life or device durability.
- Self-discharge parameter.
- Energy storing Cost.
- Power rating.
- Response time.
- Energy density.
- Power density.
sizing and capacity of the energy storage
One of the most important properties and the priority to be considered for
energy storage is the size and capacity. At the engineering phase of any
project or even during its operation, the energy storage size and capacity
should be calculated based on the application and system load. Other
parameters like cost and area are affected by the size and capacity.
The actual system load and its variation along the time should be studied
and calculated and finally, the size and capacity should be designed to be
more than the maximum load of the system. In some cases, the charging of the
other energy storage elements in the hybrid system should be considered
during the sizing calculation.
Performance and efficiency of the energy storage?
As there are many categories for energy storage based on its characteristics
and applications, some storage devices are suitable in certain places while
other is not. For example, Supercapacitors are perfect for fast and rapid
load change and batteries are good for stable operations. The behavior of
the storage device at minimum, average, and maximum load should be
considered for the storage device.
What is the Cycle life or device durability?
Cycle life or device durability means the maximum number of charging and
discharging cycles (N) of the energy-storing device. Depending on the
storage device's entire materials and the electrochemical reactions inside
it, the storage device’s efficiency will deteriorate tell reaches the
condition that it can't work normally at that time. In the battery, after a
certain number of charging and discharging, the battery will be unable to
supply its stored energy at that time it is called dead.
What is the meaning of Self-discharge for energy storage?
The self-discharge means that some energy storage devices like batteries and
supercapacitors leak energy without any connection to an external load
according to their entire electrochemical reaction. In that case, the total
stored energy will be reduced when putting it in operation.
Energy storing Cost.
As the cost of energy storing devices plays an important role and although
the advantage of cost saving of the energy storing device, other parameters
should be considered in cost calculations, especially in the large-scale
projects’ initial cost. These parameters include transportation and
installation. A payback study should be prepared.
What is the energy Storage duration?
Is the time for the energy-storing devices to supply their full energy
stored at their power capacity. For example, the time of 50 kWh energy and
50 KW power capacity is 5 hours. The design and calculation of the storage
device should consider the main system load as well as the utility loads.
A detail of the energy storage devices will be discussed later.
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