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Record-breaking year for renewable energy generation

Technology breakthroughs are lowering the cost of renewable energies while low-voltage direct current systems (LVDC) are being tested by experts both in the developed and developing world.

A new hydro plant using pumped storage in Veytaux, near Lake Geneva (Photo: Alpic)

In the sun

According to the 2018 Global Status Reportby REN21, the international non-profit association based at the United Nations Environment Programme (UNEP) in Paris, 2017 was another record-breaking year for renewable energy, characterized by the largest ever increase in renewable power capacity.

Solar photovoltaic (PV) technology is playing an increasingly important role in electricity generation. Lower prices due to increased production capacity, new technology and breakthroughs in efficiency are the main reasons for the increased adoption of solar PV systems around the world. Passivated emitter rear cell (PERC) technology has become standard in module production lines. The technique reflects solar rays back to the rear of the solar cell, increasing the overall energy efficiency of the product and improving its performance in low-light environments. A number of research projects are focusing on perovskite, a structured form of crystal compounds, because it reflects light more efficiently than crystal silicon.

IEC Technical Committee (TC) 82 prepares International Standards relating to the conversion of solar PV into electrical energy. The TC issues several ground-breaking publications which have paved the way for the adoption of PV systems, including in developing countries. One of them is the IEC 62257 series on recommendations for small renewable and hybrid systems for rural electrification. The significance of these Technical Specifications (TS) has been recognized by the World Bank and the United Nations Industrial Development Organization (UNIDO). The IEC has a cooperative agreement with these organizations to provide developing countries with access to important technical documents, which form part of the IEC TS 62257 series.The publications provide project implementers with information on how to select the best product from those available in their local markets, the quality tests best suited to specific market conditions, and on the technical and economic aspects of energy products and systems.The adoption and use of internationally accepted Standards and Technical Specifications also helps to ensure that product components work properly together and that businesses involved in the off-grid sector are able to deliver reliable products and systems.

First things first

Concentrating solar thermal power (CSP) technologies employ reflective material that concentrate the sun’s heat to drive steam or gas turbines which in turn produce electricity. CSP is used in the growing number of solar thermal electric (STE) plants being built around the world. According to the REN21 report, new STE capacity came on line in South Africa in 2017 and several facilities are being constructed in other sun-drenched countries. Most new STE plants can store heat during the day and convert it to electricity during the night, making them a predictable and reliable source of energy.

IEC TC 117: Solar thermal electric plants, has published its first three publications in the area of CSP: IEC TS 62862-1-1,IEC TS 62862-1-2 and IEC TS 62862-1-3. “For the financing of projects, we need a reliable, comprehensive and unambiguous calculation of future generation throughout the lifetime of plants. This can be predicted with a precise simulation and prediction of the yield based on meteorological data sets. The newly published Technical Specifications deal with the question of how to prepare such data sets”, explains the Chair of IEC TC 117, Werner Platzer.

The power of water

Hydropower remains the main renewable source for electricity generation worldwide. According to the REN21 report, generation from both hydropower and global pumped storage capacity (each of which is accounted for separately in the report) was estimated to have risen by 2% in 2017.

Pumped storage projects store and generate energy by moving water between two reservoirs located at different heights. This form of storage can employ surplus power from the grid, using the excess electricity produced by wind or solar systems, to pump the water in the reservoirs. The reservoirs store water when electricity demand is low and release it at peak demand times, enabling them to compensate for the intermittent generation of electricity available from the wind or sun.

One example of a new hydro pump storage facility is the upgraded Veytaux power plant near Montreux on Lake Geneva, in Switzerland, which has an installed capacity of 480 MW. Around one eighth of that capacity is held in reserve and the rest is used for energy generation. The HYPERBOLE research project, led by the laboratory for hydraulic machines of the Swiss Federal Institute of Technology (EPFL-LMH) in Lausanne, seeks to enhance the capability of hydropower plants. EPFL-LMH is equipped with three universal type test rigs complying with IEC 60193, published by IEC TC 4: Hydraulic turbines.

LVDC on trial

LVDC is a new way of transmitting power that differs considerably from the conventional centralized model of distributing electricity via alternating current (AC). In the centralized system, electricity is generated in large utility plants and then transported through a network of high-voltage overhead lines to substations. It is then converted to lower voltages before being distributed to individual households. With LVDC, power is produced close to where it is consumed. Installing LVDC systems can help remote and rural locations to access electricity. A number of LVDC projects have been rolled out in India where the technology is viewed as one of the solutions for bringing electricity to the millions of homes which still have limited and intermittent access to power.

LVDC is also viewed by an increasing number of experts as an energy-efficient option for developed nations. Most of the devices found in today’s homes and buildings, from mobile phones to LED lights, use direct current (DC) power and renewable energy sources such as wind and solar yield DC power. The direct current system minimizes the energy loss that results from the conversion of AC to DC power. The energy efficiency of LVDC systems has given rise to a number of trials. One of the most advanced is the Finnish LVDC RULES project that is led by the Lappeenranta University of Technology (LUT) and financed by the Finnish Funding Agency for Technology and Innovation.

“The LVDC RULES project has put together complete specifications for LVDC equipment optimized for public power distribution, especially in a Nordic environment”, says Tero Kaipia, one of the LUT researchers involved in the project. Kaipia also insists on the need for standards: “Standardization at system and equipment level is an essential prerequisite for the wide-scale roll-out of LVDC in Finland. Without standards, it will be difficult to construct systems using components from different manufacturers. And most of all, the network companies will not buy LVDC systems, if the certified components and standard design guidelines are not available.”

The IEC is leading efforts to promote the benefits of LVDC and to assist in the specification and ratification of these new Standards. It has set up a Systems Committee, SyC LVDC, which identifies gaps where International Standards are needed. It also helps in coordinating the work of the different TCs involved in that area.