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Battery Energy Storage Systems

Battery Energy Storage Systems

In future, there will be more demand for electricity storage facilities such as the Drakensberg Pumped Storage Scheme where water is pumped up the escarpment during lower consumption periods and flows back down generating hydro-electric power during peak demand. South Africa with its abundance of sun light hours and its current reliance on polluting, coal fired power stations is ideal for the implementation of greener power supply and storage solutions. The use of solar and wind powered electricity generation has necessitated the development of storage systems. In recent years, this technology has made remarkable strides. From the old lead-acid battery to the latest lithium iron phosphate and sodium batteries and beyond, battery energy storage solutions (BESS) are becoming cheaper and cheaper.

What is a Battery Energy Storage Solution?

A BESS is simply a method of storing generated electricity for later use. These vary from small domestic units capable of supplying off-grid power to a house, up to grid-scale units capable of supplying stored power to the national grid. It can be described as an electrochemical device that charges or collects energy from some form of power generation then discharges that energy later when required.

Battery Technology

Currently, several different battery chemistries are available and being researched and tested such as lithium-ion, lead-acid, redox flow, and molten salt (including sodium-based chemistries). Battery chemistries differ in characteristics and each type has unique advantages and disadvantages. Currently the dominant one is the lithium-ion based battery. Because of technical innovations, the price of this technology has declined over 70% between 2010 and 2016 and has continued becoming cheaper.

What size of battery energy storage system is needed for renewable energy integration?

Battery storage is one available technology that can enhance power system flexibility for integrating more renewable energy. Currently there is no rule of thumb as regards the size of the battery storage capacity for the integration of greater levels of renewable energy (RE). The amount of storage depends on system specific characteristics such as:

  • Current and planned mix of generating methods
  • Flexibility in current generation
  • Interconnections amongst generating systems
  • Electricity demand profiles, hourly, daily and seasonally of the system

What are the key characteristics of battery energy storage systems?

  • Rated power capacity or the maximum rate of discharge that the BESS can achieve from a fully charged condition.
  • Energy capacity, that is the maximum amount of stored energy in KWH
  • Storage duration, or the amount of time storage can discharge at its power capacity before depletion
  • Cycle life/lifetime is the number of cycles the storage system can provide before it degrades and needs replacement
  • Self-discharge where the battery system discharges through internal chemical processes when it is not under load
  • State of charge as a percentage influences the ability of the battery to provide energy at any given time
  • Round trip efficiency is the ratio of energy charged to the battery and energy discharged from the battery.

Where should the battery energy storage system be placed?

Essentially it depends on what the system is for and what services it will provide. It can therefore be placed in several locations. It can be in the transmission network, the distribution network near load centres or located with the renewable energy generation system.

Some examples of battery energy storage systems.

The Hornsdale Power Reserve is the largest lithium-ion BESS in the world. Opened in 2017 in South Australia it is a 100MW/129 MWh installation that provides two distinct services. With the fluctuation of electricity costs in Australia, it serves as storage as power is purchased at low prices. It also provides a contingency energy supply and can supply 30MW and 119MWh directly into the market. A reserve is held for maintaining grid frequency during unexpected outages until other, slower generators can be brought online. In 2017, after a large coal plant tripped offline unexpectedly, the Hornsdale Power reserve was able to inject several megawatts of power into the grid within milliseconds, arresting the fall in grid frequency until a gas generator could respond. By arresting the fall in frequency, the BESS was able to prevent a possible load shedding incident.

The Green Mountain Power project in Vermont, USA is a 4 MW lithium-ion project which began operations in September 2015 and is paired with a 2 MW solar installation. It provides back up power and demand charge reductions. The solar generation and storage enable the creation of a micro-grid providing power to a critical facility. It was estimated that in 2017 the installation saved $200 000 in electricity costs.

Takeaway

With the abundance of sun and in certain areas of South Africa, wind, the use of variable renewable energy (VRE) provides possibilities to provide the country with much needed additional power generation capacity. In addition it is low carbon and will reduce the sulphur pollution associated with coal powered power stations and in a water scarce environment is ideal.

With the development of more renewable sources of energy, the need is growing for energy storage systems. Read about Battery Energy Storage Systems and the necessary Evikon instruments for reliable measurement of H2, CO, temperature and relative humidity and then contact us today!