The conventional benefits of pumped storage, coupled with its modern application of integration with intermittent renewable energy technologies, are fuelling its development. Purushottam Uniyal of business intelligence provider GlobalData reports
Pumped storage is a well-known energy storage technology. The rapidly increasing renewable energy capacity in the grid is acting as a driver for the growth of energy storage technologies, and pumped storage in particular has a role to play.
The countries which already have a higher penetration of renewable energy into the grid/or are planning for a large renewable capacity, are also planning to ramp up their pumped storage capacity at the same pace. Even companies with higher wind installation are looking to develop their own pumped storage plants for the optimisation of renewable energy sources, while an increasing trend in pumped storage installation can be observed in countries with a higher renewable penetration plan.
Apart from the inbuilt characteristics of pumped storage; two important factors are driving the development of pumped storage power plants for energy storage. These are (i) compatibility of pumped storage with intermittent renewable sources to optimise their performance and (ii) advantages over other technologies for energy storage.
Compatibility of pumped storage with intermittent renewable sources
The intermittent nature of renewable energy sources such as wind and solar is of benefit to pumped storage power plant development. Incorporating wind power into the grid could prove difficult just because of bottlenecks in the grid and so the integration of energy storage facilities with wind farms could be favourable to such investors.
With solar and wind power development forecast by various agencies the world over, the amount of investment in storage technologies is expected to grow exponentially. Europe and the US are aiming at 20% renewable penetration by 2020; largely with wind power.
Advantage over other energy storage technologies for energy storage
Currently pumped storage has the edge over other energy storage technologies and may provide a solution to the issue of the intermittent nature of renewables. Nowadays much is talked about the development of other energy storage technologies but so far no other storage technology meets the criteria to absorb the intermittent nature of renewable energy sources on a larger scale. No other technology has so far achieved a breakthrough in storing large amounts of energy in a cost effective manner. Each energy storage technology is limited in some fundamental way to meet the specific needs of high amounts of energy storage.
Compressed air energy storage (CAES) and batteries can be thought of as energy storage technologies to replace pumped hydro, but both have their own limitations.
• A compressed air energy storage (CAES) system stores compressed air under pressure in a naturally occurring underground cavern with the help of motors. Currently there are only two commercial CAES systems operating in the world with a third system in the development stage (according to the Energy Storage Association, 2009). The limitations of this technology are low energy efficiency; it is very site specific, and has lower storage in comparison with pumped storage. With only two CAES systems operating, there currently is no widespread knowledge about the technology.
• Batteries are most suitable for hybrid systems with smaller storage needs and are not useful on a utility scale. Rechargeable batteries store electricity in chemical energy. Though batteries are capable of long term storage; factors like higher initial capital cost, a very short life (in comparison with the life of a power plant), and the space required makes them an unattractive option. Space and maintenance costs are other associated issues. Batteries also often suffer from memory effect (something observed in rechargeable batteries that causes them to gradually lose capacity over time).
• Pumped storage on the other hand is a well developed and matured technology and provides a solution for energy storage amounting to up to 2000MW. Pumped storage can store thousands of megawatts over a daily and seasonal period, and has the ability to quickly adapt to real time requirements. Currently pumped storage has an edge over other energy storage technologies and may provide a solution to the intermittent nature of renewables.
Spanish power
A case in point is Spanish power utility Iberdrola. Among other several existing generation technologies available to stabilise the variability of wind capacity, Iberdrola chose pumped storage, which is always available and provides significant flexibility with regard to start ups and shutdowns. Iberdrola Renovables is a subsidiary of the Iberdrola Group and has a total installed capacity of 11,010MW. Out of this, 5587.60MW has been installed in Spain since June 2010. Among all the renewable sources; wind contributes the most. The company optimises its wind resources with the integration of pumped hydro.
Iberdrola has the 635MW La Muela pumped storage facility and is building the 852MW La Muela 2 pumped storage plant in order to integrate wind and its other renewable sources. The company is further investigating the construction of three additional pumped storage plants with a total capacity of 1640MW.
Global trends
According to GlobalData research; the current global pumped storage installed capacity is approximately 132GW. Japan, the US and China are the world leaders in pumped storage installation. Many countries around the globe have plans to aggressively increase their pumped storage capacity.
In response to environmental concerns, renewable energy resources are being promoted all over the world with the help of various policy measures and incentives. However the issue of intermittence is an obstacle and is hindering the rapid growth of these clean sources of energy. Pumped storage may play an important role in the fast development of renewable energy technologies – which are sporadic by their very nature. Countries, along with leading wind power producers, are focusing on the fast development of pumped storage facilities. Its grid friendly characteristics – such as frequency-voltage balancing, reserve generation, optimisation of base loads clubbed with renewable energy integration; make it one of the best energy storage technologies. The technology will certainly attract large investments in years to come and is expected to be a major hot-spot for investment by various energy utilities in the world.
Purushottam Uniyal is an Analyst with the Alternative Energy Team at GlobalData
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