Tackling energy efficiency from the start

Better energy efficiency is central to our future energy supply and to sustain growth

By Morand Fachot

Energy efficiency represents the biggest source of untapped energy in the world and, by helping slowing down final energy consumption, one of the main contributors in the reduction of noxious gases emissions. Improved electrical energy efficiency is made possible by standardization work performed by many IEC Technical Committees (TCs) and starts with electricity generation, distribution and storage.

PS10 CSP Power Plant near Seville (Spain) PS10 CSP Power Plant near Seville (Spain)

Covering all areas

Energy intensity, the measure of energy consumption per unit of gross domestic product (GDP), can be an [imperfect] indicator [1] of energy efficiency in general. In recent years, despite relatively low energy prices, energy intensity has improved greatly, contributing significantly to a slowdown in energy-related emissions of greenhouse gases (GHG), CO2 in particular.

“Increasing mandatory energy efficiency regulation, which now covers 30% of global final energy use, played a key role in moderating the effect of low energy prices on energy use,” according to an International Energy Agency (IEA) report. The report indicates that some 1,5 billion tonnes (GtCO2) of GHG were not released in 2015 and 13 GtCO2 cumulatively since 2000, thanks to energy efficiency (EE).

Electrical energy efficiency (EEE), which is central to overall energy efficiency, ranges from electricity generation, improved electricity distribution and storage infrastructure, to the introduction of more energy efficient equipment and systems in industry, buildings, transport and consumer goods. 

Generation first…

EEE starts with energy generation, the conversion of primary energy (from hydropower, fossil fuels, nuclear, renewables, such as wind, solar, marine or geothermal sources) into electricity.

Hydropower was the first source of electricity, it represents now some 15% of electricity production in OECD countries, which is 75% more than the share of electricity generated by other renewable sources. Modern hydro turbines can convert 90% of all available energy into electricity.

IEC TC 4, established in 1913, develops International Standards for hydraulic turbines. TC 4 develops and maintains publications that assess the “hydraulic performance of hydraulic turbines, storage pumps and pump-turbines.” Hydropower installations are robust and reliable but they need rehabilitation after 30 to 50 years of operation. TC 4 works on a new edition of a Standard that deals with the various options to increase power and efficiency in rehabilitation projects.

Burning fossil fuels – coal or oil – in thermal power plants is the second oldest form of generating electricity. The share of electricity generated from fossil fuels was 67% in 2014, according to the IEA. A significant amount of primary energy is wasted in the conversion of fossil fuels into electricity in thermal plants (up to 60-65%). One way of reducing waste is to recover waste heat generated in cogeneration Combined Heat Power (CHP) installations to use in industry or for urban heating systems.

Thermal power plants use steam turbines to convert heat and steam into power. International Standards for steam turbines, which are used also in nuclear power plants, geothermal installations, solar thermal electric and CHP plants, are developed by IEC TC 5.

IEC TC 2: Rotating machinery, develops International Standards for rotating electrical machines, including motors, used, for instance in “generators driven by steam turbines or combustion gas turbines”. This work includes aspects aimed at improving the EE of motors.

Renewable sources are set to play a central role in EEE efforts, by reducing the share of fossil fuels. All IEC TCs involved in renewable sources installations work on developing new more EE systems and in improving the EE of existing ones. These TCs include:

IEC TC 82: Solar photovoltaic energy systems, which develops also International Standards for various measurements and performance parameters of PV devices.

IEC TC 88: Wind energy generation systems. TC 88 prepares, for instance, International Standards “for power performance measurements of electricity-producing wind turbines”. In wind power generation, drivetrain, voltage optimization, use of high voltage direct current (HVDC – IEC TC 115) and advanced control systems (IEC TC 57) contribute to better EEE.

IEC TC 114: Marine energy – Wave, tidal and other water current converters, is a recent IEC TC, but the potential of harnessing marine energy is very promising. Much of the work of this TC focuses on power performance assessment of these converters.

IEC TC 117: Solar thermal electric plants, also covers a fairly recent area, which is fast expanding and showing a significant potential. 

…followed by distribution

Electricity distribution is also an area where EE is addressed by developing new technologies and systems or improving existing ones.

Electrical energy produced by power plants in medium (MV 20 000 V) or low (LV 1 000 V) voltage is elevated to HV (up to 400 kV) by a step-up substation before being transmitted across long distances by high-tension power lines. A step-down station converts HV to MV to transport it to feed MV or LV transformers for use by households, factories, commercial buildings, etc. The efficiency of large transformers in step-up and step-down substations is very high and can reach 99%. The efficiency of MV and LV transformers may range between 90% and 98%. IEC TC 14 develops International Standards for power transformers.

Losses in cables are higher than in transformers, but EE is improving there as well. IEC TC 20 develops and maintains International standards for electric cables and incorporates improved efficiency and durability in its maintenance procedure. Ultra high voltage (HUV) distribution of both DC and alternating current (AC) is seen as allowing the EE transmission of power generated by renewable energy sources in sites far away from the main load centres, e.g. in offshore wind farms, large hydropower plants or large solar installations in deserts with acceptably low transmission losses. International Standards for HV and UHV transmission systems for DC and AC are being developed by IEC TC 115 and IEC TC 122, respectively. 

Storing electricity for later use

Energy storage is an important component of EE projects. It helps reduce transmission losses and help balance power from intermittent RE sources. By allowing electricity to be stored for later use, it can eliminate the need for the expensive (and polluting) use of generators and idling power plants. It is also an essential ingredient in so-called microgrids and off-grid rural electrification. International Standards for electricity storage systems are developed by:

IEC TC 4: Hydraulic turbines: Hydropower, in addition to generating electricity, makes up some 90% of installed storage capacity worldwide, in the form of pumped storage hydro (PSH) installations. In PSH, water is pumped in a reservoir uphill when electricity is cheap and plentiful (excess electricity from wind or solar power installations) and released downhill to generate electricity, when needed. It is highly efficient (80% or more). IEC TC 4, prepares also International Standards for “storage pumps and pump-turbines”.

IEC TC 21: Secondary cells and batteries, prepares International Standards for all types of batteries used in energy storage, including stationary (lead-acid, lithium-ion and NiCad/NiMH) batteries and flow batteries.

IEC TC 120: Electrical Energy Storage (EES) Systems, develops International Standards in the field of grid integrated EES Systems, focusing on system aspects rather than energy storage. 

Into the future…

In many countries, electricity grids were designed based on technology that was modern more than 100 years ago. Standardization work by several IEC TCs makes it possible to update these legacy systems in order to transform them in “Smart Grids”. This is essential to reduce distribution losses and identify energy efficiency opportunities. This means updating the ageing infrastructure to allow the integration of intermittent renewable energy sources, ensure the security of supply and increase in energy use.

[ ] “For instance, a small service-based country with a mild climate would have a lower intensity than a large industry-based country in a cold climate, even if energy was used more efficiently in the latter country.” (IEA)

Gallery
Limberg reservoir pumped storage Upper and lower basin of Limberg II pumped storage plant, Austria (Photo: Voith)
transformer Transformer
Cutaway of Siemens SST-500 GEO steam turbine for geothermal power plants Cutaway of Siemens SST-500 GEO steam turbine for geothermal power plants (Photo: Siemens)
PS10 CSP Power Plant near Seville (Spain) PS10 CSP Power Plant near Seville (Spain)