Pumped storage key to optimizing other renewables
Hydropower is the oldest and largest renewable source of electrical power. In the form of pumped-storage, it is also key to balance intermittent RE generation from wind and solar installations and represents an essential EES solution.
The IEC strongly supports EES. The IEC MSB (Market Strategy Board) recently published two White Papers, the first on EES, the second analysing the role of large-capacity EES systems, integrating large-capacity RE sources. Both White Papers stress the crucial importance of EES in future installations.
IEC TC (Technical Committee) 120: Electrical Energy Storage (EES) Systems has been created to prepare International Standards for such systems.
Of all energy storage technologies, including those under development, pumped-storage hydropower is the most cost effective and technically viable. It currently accounts for more than 99% of installed storage capacity for electrical energy worldwide: around 127 GW (gigawatts), according to the EPRI (Electric Power Research Institute – the research arm of America’s power utilities) and Germany's Fraunhofer Institute.
The work of experts within IEC TC 4: Hydraulic turbines, also supports the construction, operation and maintenance of pump-turbine storage sites.
Established benefits of pumped storage
Pump storage installations are highly cost-effective, reducing electricity costs by using electricity produced at off-peak times when the price is lower, to pump water from the lower to the upper reservoir, turning electrical energy into gravitational potential energy. When power is needed, water is released back down to the lower reservoir, spinning a turbine and generating electricity along the way.
Systems demonstrate low maintenance costs and typically achieve one of the highest cycles per lifetime at some of the lowest costs. High-performance hydropower equipment can frequently run without interruption for extended periods of time and hydroelectric plants have a life-time of at least 50 years, making hydropower and pump storage a profitable long term investment.
Interest in pumped-storage is increasing, particularly in those regions and countries with the most variable renewable resources and where new installations of traditional hydropower are harder to achieve. The vast majority of installations are currently found in Europe, Asia (Japan in particular) and the US.
Experts involved in IEC TC 4 are seeing increased demand for clean energy pumped-storage installations because of the known benefits of pump-turbines. In addition, associated production and monitoring equipment provides increased revenues for producers and more affordable pricing for end-users.
Small but by no means insignificant
Small hydropower schemes are not as spectacular as large hydro projects but they play an important and growing role in bringing electricity to more people worldwide.
Small means different things to different people. In the hydroelectric domain small, for the IEC, means installations of up to 15 MW, but in some countries it may cover systems of up to 30 MW.
The concept covers a wide range as it includes micro-hydro schemes, which can be as large as 500 kW and are generally run-of–the-river developments for villages, and pico-hydro systems that have a capacity of 50 W to 5 kW and are generally used for individuals or clusters of households.
TC 4 prepared Standards that describe the installation and operating conditions of small power stations and that set out acceptance tests of small hydroelectric installations.
Harnessing power from the oceans
After developments in the solar and wind sectors, harnessing marine energy is set to provide essential additional sources of clean power in the future. IEC TC 114: Marine energy - Wave, tidal and other water current converters, is developing International Standards in this domain.
Oceans cover more than 70% of Earth's surface; they are sources of huge kinetic energy from waves, currents and tides, and of thermal energy in the form of heat they harness from the sun. They could, in theory, cover a sizeable share of the world's energy needs.
Marine kinetic energy is very strong as the density of water is roughly 850 times that of air. It comes from different sources – waves, tides or current – some more powerful and predictable than others. Therefore, its conversion into electrical energy requires a wide range of technologies to cover all its aspects.
The main criteria for selecting sites at which to tap into marine energy sources are tidal current velocity, wave formation and turbulence, water depth and bathymetry, and access to grid connection.
OTEC (ocean thermal energy conversion) uses the temperature difference between cold deep waters and the warmer waters near the surface to run heat engines that produce electricity. OTEC works best when the temperature difference is around 20o C, typically found in tropical coastal areas.
OTEC has a substantial potential, however, what is currently technically recoverable is much less significant. TC 114 set up a Project Team to look at guidelines for design assessment of OTEC systems.
Addressing essential aspects
TC 114 prepares International Standards that aim to address essential aspects for all forms of marine kinetic energy conversion.
Equipment, such as submarine cables and connecting equipment is also essential to transmit power produce from marine energy installations to grids.
Underwater connectors are also essential to link cables together or to link to renewable energy equipment, to hubs and to the power grid. International Standards for such connectors are prepared by TC 20.
Going with the wind
Wind energy is currently the most cost effective new renewable energy source. Many countries have goals for wind to supply more than 20% of their energy generation by 2030, with offshore turbines playing a significant role in some countries.
Wind power now supplies the greater part of the world’s non-hydropower renewable electricity capacity. Global wind power capacity was 238 GW (gigawatts) at the end of 2011, up from just 18 GW at the end of 2000, with a CAGR (compound annual growth rate) of over 25% over the past five years.
The supply of wind turbines is a global business, with the six largest producers all based in different countries and the 10 top manufacturers accounting for nearly 80% of global production. IEC International Standards, prepared by IEC TC 88: Wind turbines, are ever more central to the successful development of the industry and have proven essential to meet the complex challenges and set of issues faced by the wind power industry. The global nature of that industry means that International Standards play a vital role in ensuring the proper production, testing, worldwide installation and acceptance of wind power turbines, whether large or small and installed on land or offshore.
Synergies and conformity assessment
The scope of TC 114 is being extended to cover aspects of river currents as the technology deployed for certain marine tidal and current installations is also relevant for specific river applications. TC 114 AHG (ad hoc Group) 2, is tasked with assessing the "power performance (…) of electricity producing river current energy converters". Some tidal turbines are now being installed in marine and river environments. As the technologies used in small hydro can apply TC 4 and TC 114 liaise on certain aspects.
Since marine energy projects share some technical issues with offshore wind farms on common elements, such as mooring and floating installations, TC 114 is liaising with TC 88: Wind turbines.
The IEC CAB (Conformity Assessment Board set up WG (Working Group) 15 to develop a Framework for an internationally standardized approach of addressing the conformity assessment needs of the marine energy industry.
This follows the establishment of WG WT CAC (Wind Turbine Certification Advisory Committee).
Essential standardization work for RE expansion
Standardization work carried by TC 4, TC 114, TC 88, as well as by TC 82: Solar photovoltaic energy systems, TC 117: Solar thermal electric plants, and TC 120: Electrical Energy Storage (EES) Systems will ensure that the growing demand for more power for RE sources can be best integrated in the future global energy mix.