Understanding Energy storage
Energy storage has been fingered as the ‘holy grail’ of the energy transition. In this series, we demystify energy storage technologies and keep you abreast of the developments in the energy storage space.
Renewables like solar and wind technologies are penetrating our power systems in an unprecedented manner and this will continue. A combination of factors is responsible for this trend. Climate change concerns, security of supply, policy and the need to move towards clean energy are some of the key factors. These renewable energy technologies like solar and wind, however, are intermittent; the sun does not shine all day and the wind does not blow all night.
“Energy storage has been considered a powerful missing link that can unlock the benefits of clean, and resilient energy supply.”
This intermittent nature brings uncertainty to the planning and operation of power systems. To mitigate against this challenge, energy storage has been considered a powerful missing link that can unlock the benefits of clean, and resilient energy supply. It is believed that Solar and wind energy technologies will start replacing fossil fuels on a significant scale once we get a handle on energy storage. From all indications, this will not be long.
By the way, what is Energy storage?
In the most fundamental sense, energy storage technologies are technologies that can store various forms of energy and make them available at a later time. They can operate at grid level, taking in energy when there is surplus and supplying back into the grid when demand rises. Likewise, they can operate at individual consumer level, taking in excess energy when produced, and supplying energy when the supply diminishes. Either way, the energy storage technology helps to balance demand and supply. Though there has been lot of innovation and buzz in energy storage space today, the concept of energy storage has been around for ages. A common form of energy storage that has been used for ages is pumped hydro storage (PHS) tagged the world’s “water battery”. Here, electric energy is generated by water previously pumped from a lower source to a higher reservoir in a hydroelectric development.
When demand is low, water is pumped uphill, when demand increases, water from the upper reservoir runs down and turns a turbine, generating electricity. The International Hydro power Association, in its 2018 paper, indicated that Pumped hydro accounts for over 94 per cent of installed global energy storage capacity. There are other forms of energy storage technologies .
Classifications of energy storage
nergy storage technologies are classified according to function (designed for power quality or energy management) or energy forms. The table below gives a high-level classification of existing energy storage technologies based on energy forms. The diverse characteristics of these technologies makes it easy to adapt to different applications — whether stationary or mobile. Clearly, energy storage is beyond batteries.
Energy storage can be applied at different points of the electricity value chain — within grid network or with the individual customer. The diagram below shows the different possible locations of energy storage within the grid. According to Rocky Mountain analysis, the benefits of energy storage increases as one goes further away from the supply network
Homes that are farther from the grid are more vulnerable to disruptions than homes close to the power sources. This is obvious. As earlier pointed out, different energy storage technologies can be applied across the shown electricity value chain to optimize the gains of storage.
Before looking at the applications of energy storage, it is useful to understand these commonly used phrases: Behind the meter and front-of-the meter energy storage installations.
Behind-the-meter (BTM) systems provide electricity directly to the home or business without going through the grid or the electric meter. For example, if you power your home with solar and store excess generated energy in a battery, there is no need for the generated energy to pass through your meter. In this case, your onsite generation and storage are BTM system. Conversely, In Front-of-the-meter (FTM) scenario, the power must pass through an electric meter to reach the end customer. Grid electricity typically passes through an electric meter before hitting the appliances in the home. This is a typical FTM system. The diagram below shows a representation of BTM and FTM system
Research indicates that across three stakeholder groups — customer, transmission organizations (ISOs/RTOs) and utilities, energy storage has up to thirteen (13) grid level and customer applications. The table below demonstrates the respective value across the value chain.
Storage as transmission
Deploying storage as “virtual transmission” is a relatively new concept and has been tested in a few markets. Here, energy storage is installed in a way to “mimic” transmission lines flows, absorbing and injecting real and reactive power, effectively solving line congestion.
The potential benefits of storage as transmission abound such as:
i. It is faster to deploy. Hundreds of megawatt capacity is provided in far less time than the legacy assets would have taken. The giant 100 MW capacity battery built by Tesla in Australia only took 100 days. An equal legacy transmission capacity would take upwards of years.
ii. Storage is scalable and modular and takes far less footprint compared to typical transmission projects. Also, Right-of-way, visual impact and related environmental assessments do not arise.
iii. In addition to the virtual transmission service, storage asset can provide a range of ancillary services, such as frequency and voltage control further increasing the economic potential of the assets.