Published On: Jan 28, 2016
Today’s energy world is at a turning point. Resources are depleting, pollution is increasing and the climate is changing. As we are about to run out of fossil fuels in the next few decades, it is important to find substitutes that will guarantee our future energy supply on a sustainable basis. The global energy demand is huge and is set to grow by approximately 37% until 2040 (as per World Energy Outlook 2014). This global energy need, at the same time, has to be cleaner than the energy produced from the traditional generation technologies like coal, natural gas, etc. With this backdrop, the electrical grid and the power systems are experiencing rise of some disruptive innovations and possibly tomorrow’s power grid would see flow of power from both directions and an island of power systems comprising of Distributed Generation (micro grids, mini grid), Renewable Energy, etc.
While the extensive use of such energy sources can minimize threat of global warming and climate change, however the power output of these sources are not as reliable and as easy to manage the energy demand than the traditional power sources. One of the effective ways to overcome this challenge (reliable power delivery) is to store the power produced by these systems and subsequently use it in a controlled manner. The role of enabling technologies such as energy storage is becoming more important as the world moves towards deeper penetrations of innovative power systems. In order for these new sources of energy to become reliable as primary sources of energy, energy storage is a crucial factor.
The blog identifies the energy storage technologies available today, their market segments and its applications, key drivers, types of storage technologies, etc. that would be an enabler in overcoming the challenges of modern grids and distributed generation through available alternative energy sources.
Energy storage technologies can operate across different technical and commercial functions of the electricity market segments, including generation, transmission, distribution, end-use or direct off-grid use. Key applications across each segments are illustrated below:
Brief description of each application is mentioned below:
In each of these market segments, energy storage technologies can simultaneously fulfil multiple roles varying from load shifting, to spinning reserve, wholesale arbitrage and power quality.
Some of the prominent drivers for storage technologies are:
Energy storage technologies can be divided into three types,
Let us first understand in brief the description of key technologies, followed by qualitative comparison of those technologies.
Parameters |
PHS |
CAES |
BES |
FS |
SC |
---|---|---|---|---|---|
Technology |
Proven |
Proven |
Proven |
Promising |
Proven |
Storage Mechanism |
Mechanical |
Mechanical |
Electrochemical |
Mechanical |
Electrical |
Typical Range |
Up to 2.1 GW |
25 – 350 MW |
100 W – 20 MW |
On kW scale |
1 kW – 250 kW |
Environmental/Emission concerns |
No emission |
No emission |
Very Low |
No emission |
No emission |
Expected Life (Years) |
40-60 |
20-25 |
5 – 15 |
30 |
30 |
Self-Discharge rate |
Very Low |
Very Low |
Very Low |
Very High |
Very High |
Electrical Efficiency |
75-80% |
>60% |
88-90% |
90-95% |
>95% |
Key Applications |
Spinning reserve, Wholesale arbitrage |
Wholesale arbitrage (Peak shaving), Spinning reserve |
Spinning reserve, Power quality |
Voltage regulation |
Emergency power sources, power quality |
Key Advantages |
High bridging time, Infinite number of cycles |
Large power and Energy density |
High energy density, High bridging time |
High efficiency, Steep accessibility |
Maintenance free, |
Key Disadvantage-s |
Ecological problem (at-least 2 reservoirs needed) |
Large space required |
Low power density, hazardous to environment |
Small power range |
Less storage capacity, low bridging time |
Table 2. Qualitative Comparison of Key Energy Storage Technologies
From Table 2, it is clear that a variety of energy storage technologies exists with each one possessing different attributes and intended for different applications. The choice of the ideal storage technology to be used depends on a number of factors. The key ones, among others, are the amount of energy to be stored, the time for which this stored energy is required to be retained or to be released, spacing and environmental constraints, cost, and the exact location of the network on which the storage is required.
Problem Statement: The utility Kodiak Electric Association (KEA) in Alaska has a peak load of 27 MW and base load of around 11 MW. It’s existing power capacity consisted of 23 MW hydropower and 33 MW diesel generation, in addition to 4.5 MW of installed wind power capacity. The utility was further in phase of adding additional 4.5 MW of wind capacity into the system, however the existing power assets would not be able to provide sufficient frequency response to help compensate for the additional capacity to come on stream.
Solution Adopted: KEA selected battery storage solution (instead of adding diesel generation) to provide frequency response on stream as spinning reserve. The battery system by Xtreme Power delivered a 3 MW advanced lead – acid battery solution to the utility. The lead – acid battery system was considered because the system remains at a high state of charge and can discharge quickly for very short periods. The system monitors grid conditions 100 times per second and can instantly deliver 3 MW of power within 50 milliseconds, if grid frequency falls significantly. The system responds to an average of 285 of these events throughout each day and enables much fuller use of the wind resource. The total cost for turnkey storage system was approx. INR 20 Cr. ($ 1 million/MW) (excluding costs incurred by the utility, including a step-up transformer and MV switchgear).
Benefits & Conclusion: In the first six months of implementation, KEA integrated another ~4.4 MW of wind power into grid, displacing diesel generation that would have higher generation costs and increasing environmental concerns too. The utility’s decision to use storage system was based on a desire to increase its renewable wind source integration, improve sustainability and reduce operating costs.
(For details, visit link: ALASKA, U.S., ISLAND/OFF-GRID FREQUENCY RESPONSE)
We thus note that there are daunting challenges to harness sustainable power supply through alternative energy sources for the future. Such energy sources contribute varied quantum of energy in intermittent forms. There is a clear need and capability of Energy storage which can be deployed throughout electricity systems to help facilitate increased penetrations of intermittent renewable generation, while producing numerous other operational benefits in parallel, such as load shifting, grid stability and power quality.
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