Latest Studies

  • Rubrik: Datum: Title: 5-level topology – the next logical step for inverters

    Inverters work on the principle of switching between different levels of DC voltage. The output is thus not an ideal sine-shaped AC wave, but rather a pattern of rectangular pulses that are made to resemble the sine wave as accurately as possible by switching between specified at high frequency. Therefore, the ability to approximate an exact sine wave with rectangular pulses is restricted by the number of available voltage levels: the higher the number, the closer the approximation to the ideal sine shape. The non-ideal sine shape causes harmonics (currents and voltages at higher frequencies). Harmonic filters can be used to smooth the output by absorbing problematic harmonics, but these filters are both a cost factor and a cause of additional losses in energy conversion.

  • Rubrik: Datum: Title: Staggering growth in consumer demand for green power

    Most Europeans can choose who they buy their power from and current market data shows exactly what consumers want: "European households and businesses continue to show they are dead serious about the renewable energy transition," says Tom Lindberg, Managing Director in ECOHZ

  • Rubrik: Datum: Title: Heat transfer fluids: Safe through the winter

    Heat transfer fluids with frost protection are an important component in solar power systems and geothermal heat pump systems. Temperature resistance plays a major role for solar power systems, and for heat pumps, the potential water hazard from leaks is just as important.
    SW&E spoke to Emma Bardolph from Climalife about heat transfer fluids for solar thermal.

  • Rubrik: Datum: Title: Do it Locally: Local Voltage Support by distributed Generation

    This report by the IEA Photovoltaic Power System Programme presents an overview of research results and field experiences on the subject of local voltage support by distributed generators (DGs). The focus of this report is the German power supply system, which has experienced a significant photovoltaic (PV) expansion of approximately 36 GW within the last decade. Case study results from different countries like Belgium, Austria and the United States complement the findings on local voltage support by PV systems. A major PV integration challenge is the voltage regulation in distribution grids with a high PV penetration. Advanced PV inverter functions, like reactive power control or active power curtailment, can help to reduce the impact of PV feed-in on the local voltage magnitude. Nowadays, several countries demand reactive power and partly active power control capabilities from DGs in their grid codes and DG interconnection guidelines. Central control (coordinated control) approaches by DGs are not in the scope of this report.

  • Rubrik: Datum: Title: Network Driven Demand Side Management

    Photovoltaic energy deployment is paving the way for deep changes in the way electricity is produced and the grid is managed. While multi megawatts power plants and High Voltage power system remain the main drivers for balancing production and consumption, we see now the emergence of production of electricity and storage systems at Low Voltage level. This leads to new opportunities and challenges for active power balance and power system management. Demand Side Management is identified as a major opportunity and in this report the title “Network Driven Demand Side Management” has been chosen to emphasize a collaborative approach between decentral generation, loads, storage systems and the grid.

  • Rubrik: Datum: Title: Improving Efficiency of PV Systems Using Statistical Performance Monitoring

    Availability, high efficiency and therefore fault detection are of equal importance to the PV system owner and the grid manager for utility‐grade PV and increasingly for the small residential array. With increasing penetration of small arrays, large neighborhoods aggregate to virtual megawatt power stations, creating an amorphous and unpredictable power‐producing entity.

  • Rubrik: Datum: Title: Optimised lubricants for longer maintenance cycles

    Oils and greases protect the most important components of a wind turbine from wear and corrosion. However, demands on the lubricants have risen due to higher loads and longer oil-change intervals.

  • Rubrik: Datum: Title: Solar Heat Worldwide: Global Report on Solar Heating and Cooling

    Solar thermal systems save 40.3 million tons of oil equivalent per year and reduce CO2 emissions by 130 million tons annually. This is one of the key findings of the report Solar Heat Worldwide, published today by the International Energy Agency’s Solar Heating and Cooling Programme (IEA SHC). With data from 66 countries, it is the most comprehensive annual evaluation of solar heating and cooling markets worldwide.

  • Rubrik: Datum: Title: All-sky imager based ramp rate prediction for PV

    The solar resource shows variabilities, which influence the frequency, voltage and overall stability of electrical grids with high photovoltaic penetrations. Facing this challenge, legal limitations of the fluctuations of generated electricity (ramp rates regulations) are already effective or under discussion. As expected, small island grids with high solar penetration were the first to introduce ramp rate regulations: Puerto Rico has specified a maximum negative 1-minute ramp rate of 10 % of the rated capacity and Hawaii has defined a maximum negative ramp rate of 1 MW/min during certain times.

  • Rubrik: Datum: Title: Ingeteam's 1500 Vdc technology for Spain's first hybrid wind power storage plant

    Renewable energies, and wind and solar power in particular, are recognized as the most suitable clean energy generation sources to meet the world's growing energy demand while achieving the targets for reducing greenhouse gas emissions. However, a high penetration of these energy production sources in the generation mix does have some drawbacks. This is due to the natural intermittency associated with the wind and sun alike, which could affect the balance between generation and demand and, therefore, the stability of the distribution network. The most effective way to overcome this obstacle is to include an energy storage system (ESS), thereby making it possible to stabilize the grid and mitigate the unpredictability associated with the intermittency of renewable energy generation.