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Integration of renewable energies, flexible loads and storages into the German power grid: Actual situation

Harald SCHWARZ, Xiaoshu CAI

Frontiers in Energy 2017, Volume 11, Issue 2,   Pages 107-118 doi: 10.1007/s11708-017-0470-x

Abstract: Starting from the late 1990’s, the German government decided to change the national electric power supply system dramatically. The main stimulating instrument was the German Law on Renewable Energies (Erneuerbare Energien Gesetz (EEG)), which guaranteed a fixed feed-in tariff to everyone who was willing to invest into renewable generation. Based on the year of commissioning, defined revenues per kWh were fixed for the next 20 years. Due to a very attractive over-funding, more than 1.5 million renewable generation units were connected to the German grid up to the end of 2015. According to the EEG, renewable generation units can feed to the grid wherever they are located and whenever they are able to produce. The old physical principle was and is still neglected, which clearly stated that generation always has to follow the demand—simply due to the limited availability of storages in the power system. Only in cases, when temporarily renewable overproduction exceeds the tolerable loading of lines or transformers respectively endangers the system stability in total, are German grid operators allowed to announce curtailments by emergency measures. Even in such cases, the “not produced energy” from renewable sources has to be funded. Although the installed capacity from renewables is much higher than the peak load in Germany, it contributes only about 32% to German average annual energy. Unfortunately, the regional distribution of renewable generation and load is very different, e.g. in the northeast of Germany, this Renewable Energy (RE)-ratio meanwhile exceeds 100% due to the high RE-penetration and low load. High transits of renewable overproduction from the north to the south will be necessary at nearly every day per year. Therefore, a tremendous change is needed within the German power grid. This paper will give a first overview followed by several others, describing possible solutions on how to overcome this critical situation.

Keywords： grid integration     renewable energies     system stability     storages     flexible loads     new market design    

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Impact of renewable energies on the operation and economic situation of coal fired power stations: Actual

Hans-Joachim KRAUTZ, Alexander LISK, Joachim POSSELT, Christian KATZER

Frontiers in Energy 2017, Volume 11, Issue 2,   Pages 119-125 doi: 10.1007/s11708-017-0468-4

Abstract: Due to the fluctuating character of the renewable energy sources the demand of conventional power plants for flexibility is increasing. In the recent years, in Germany there has been a fast rise of production capacity of renewable energies, especially from wind turbines, photovoltaic installations, and biomass plants. The installed nominal power of wind turbines is actually (December 2016) 42 GW and of photovoltaic installations 40?GW. The renewable electric energy production in Germany is about 190?TWh/a, which represents a share of 33% of the yearly demand. The increased need for flexibility affects both the power gradients as well as the minimum load of conventional power plants. Due to this flexibility behaviour, conventional power plants are faced with problems concerning the durability of power plant components, corrosion, more maintenance effort and consequently the overall life expectancy. Another consequence of the increasing share of renewable energies is the decreasing full load operating hours, especially of coal fired and gas power plants. Along with decreasing revenues from the energy exchange market, coal fired power plants are faced with new economically challenges.

Keywords： flexible load operation     minimal load     power gradients     power plant maintenance     corrosion     life expectancy    

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Theoretical analysis and actual experimental research on static characteristics of suspendome structure

CHEN Zhihua, YAN Xiangyu, SUN Ruirui, FENG Zhenchang, QIN Yali, ZHAO Jianbo

Frontiers of Structural and Civil Engineering 2007, Volume 1, Issue 3,   Pages 286-292 doi: 10.1007/s11709-007-0037-8

Abstract: The suspendome used as the roof of the VIP hall in Tianjin Museum was analyzed by ANASYS under the assumptions of hinged joints and rigid joints in up chord, respectively, and the results show that the member force and nodal displacement under the two assumptions have little difference. Thus, it is attained that the suspendome can be analyzed with the assumption of hinged joints. A full-scale test on the suspendome with half-cable and half-pipe was carried out. The loading system, arrangement of measuring points, and the test procedures are introduced. Also, a test on steel wire ropes for elastic module was carried out. The experimental and theoretical values of member forces and nodal displacements were compared and it showed that they accord well with each other under low-level load. While under high-level load, the experimental value was bigger than the theoretical value due to the influence of the test environment. With the increase of the load, tension of outside cables and looseness of inside cables occurred, which indicated that the prestressing value in inside cables should be properly assigned. Both the experimental and theoretical results verify that the suspendome has a wide application prospect with the advantages of perfect mechanical characteristics, low steel consumption, convenient construction and low cost.

Keywords： Tianjin     influence     displacement     high-level     low-level    

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Model design of static experiment for the middle tower of multispan suspension bridge based on actual

Ji Lin,Wang Tao and Wu Hanliang

Strategic Study of CAE 2012, Volume 14, Issue 5,   Pages 66-70

Abstract: In this paper, a small-scale model was designed for the middle tower of Taizhou Bridge, based on its actual

Keywords： suspension bridge     middle tower     actual working conditions     similarity theory     numerical simulation     model    

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Compressor performance of two-stage turbocharging system

HE Yituan, MA Chaochen, WEI Mingshan, ZHU Zhifu, HE Yituan

Frontiers of Mechanical Engineering 2008, Volume 3, Issue 2,   Pages 218-221 doi: 10.1007/s11465-008-0027-0

Abstract: The results showed many differences between the corrected mass flow and the actual mass flow of the highTo find out the actual supercharging effect of the two-stage turbocharging system, it is better to adoptthe actual mass flow.

Keywords： special two-stage     HP     performance experiment     reliability     actual supercharging    

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Hyperbranched magnetic polymer: highly efficient removal of Cr(VI) and application in electroplating wastewater

Frontiers of Chemical Science and Engineering 2023, Volume 17, Issue 10,   Pages 1568-1580 doi: 10.1007/s11705-023-2303-2

Abstract: For actual wastewater containing Cr(VI), the Cr(VI) concentration was reduced from 25.8 to 0.4 mg∙Lactual

Keywords： magnetic polymer     chromium removal     hydrogen bonding     recyclability     actual wastewater    

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Investigation on the integral output power model of a large-scale wind farm

BAO Nengsheng, MA Xiuqian, NI Weidou

Frontiers in Energy 2007, Volume 1, Issue 1,   Pages 67-78 doi: 10.1007/s11708-007-0006-x

Abstract: The actual wind speed power model and calculation method of a wind farm made up of many wind turbineFinally, an actual power output of the wind farm is calculated and analyzed by using the practical measurement

Keywords： power model     actual     energy     large-scale     practical measurement    

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Concepts and implementation of strain-based criteria in design codes for steel structures

Reidar BJORHOVDE

Frontiers of Structural and Civil Engineering 2012, Volume 6, Issue 3,   Pages 210-216 doi: 10.1007/s11709-012-0165-7

Abstract: It does not represent the actual behavior of the steel in a structure, and was never intended to do somaterial responds it would be better to determine the strains and deformations that will take place during actual

Keywords： steel     stress-strain characteristics     tension test     strain design     actual behavior     improved design codes    

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Evaluation of the performance of a centralized ground-water heat pump system in cold climate region

Shilei LU,Zhe CAI,Li ZHANG,Yiran LI

Frontiers in Energy 2014, Volume 8, Issue 3,   Pages 394-402 doi: 10.1007/s11708-014-0310-1

Abstract: The aim of this study is to evaluate the performance of a centralized open-loop ground-water heat pump (GWHP) system for climate conditioning in Beijing with a cold climate in China. Thus, a long-time test was conducted on a running GWHP system for the heating season from December 2011 to March 2012. The analysis of the testing data indicates that the average heat-pump coefficient of performance (COP) and the COP of the system (COPs) are 4.27 and 2.59. The low value and large fluctuation in the range of COP are found to be caused by the heat transfixion in the aquifer and the bypass in the circulation loop. Therefore, some suggestions are proposed to improve the performance for GWHPs in the cold climate region in China.

Keywords： ground-water heat pump (GWHP)     actual coefficient of performance     heat transfixion    

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Title Author Date Type Operation

Integration of renewable energies, flexible loads and storages into the German power grid: Actual situation

Harald SCHWARZ, Xiaoshu CAI

Journal Article

Impact of renewable energies on the operation and economic situation of coal fired power stations: Actual

Hans-Joachim KRAUTZ, Alexander LISK, Joachim POSSELT, Christian KATZER

Journal Article

Theoretical analysis and actual experimental research on static characteristics of suspendome structure

CHEN Zhihua, YAN Xiangyu, SUN Ruirui, FENG Zhenchang, QIN Yali, ZHAO Jianbo

Journal Article

Model design of static experiment for the middle tower of multispan suspension bridge based on actual

Ji Lin,Wang Tao and Wu Hanliang

Journal Article

Compressor performance of two-stage turbocharging system

HE Yituan, MA Chaochen, WEI Mingshan, ZHU Zhifu, HE Yituan

Journal Article

Hyperbranched magnetic polymer: highly efficient removal of Cr(VI) and application in electroplating wastewater

Journal Article

Investigation on the integral output power model of a large-scale wind farm

BAO Nengsheng, MA Xiuqian, NI Weidou

Journal Article

Concepts and implementation of strain-based criteria in design codes for steel structures

Reidar BJORHOVDE

Journal Article

Evaluation of the performance of a centralized ground-water heat pump system in cold climate region

Shilei LU,Zhe CAI,Li ZHANG,Yiran LI

Journal Article