Technical and economic comparison of grid supportive vanadium redox flow batteries for primary control reserve and community electricity storage in Germany

Aquesta és una còpia de la versió author’s final draft d'un article publicat a la revista [International journal of energy research]. URL d'aquest document a UPCommons E-prints: http://hdl.handle.net/2117/127058Primary control reserve and maximising self-consumption are currently two of the main applications for large-scale battery storage systems. Although being currently the most profitable application for large-scale batteries in Germany, storage systems applying primary control reserve have not been implemented in a grid supportive manner in distribution grids yet. Despite a current unfavourable regulatory framework and reimbursement scheme for community electricity storages in Germany, they are potentially more profitable than residential storages, which is mainly due to their economy of scale, and thus they may become the major large scale battery application in the future. The two applications: primary control reserve and maximising self-consumption, are combined with a grid supportive behaviour by providing reactive power control and/or peak shaving and are fitted to a vanadium redox flow battery prototype, which is installed in a distribution grid in southern Germany. Based on measured data from the prototype, two battery models for two different time resolutions (1s, 1min) are presented in detail along with their respective operation models. The operation strategy model for primary control reserve comprises the so-called degrees of freedom used to reduce the energy needed to recharge the battery. The operation strategy to maximise self-consumption is based on a persistence forecast. The model for the operation strategy for a grid supportive primary control reserve was validated in a field test revealing a relative error of 2.5 % between the simulated and measured state of charge of the battery for a multi-week time period. The technical assessment of both applications shows that the use of the degrees of freedom can reduce the energy to recharge the battery by 20 %; and in the case of self-consumption, the curtailment losses can be kept under 1 %. The economic assessment, however, indicates that even for the most promising primary control reserve case, the investment costs of vanadium redox flow batteries must be reduced by at least 30 % in order to break even. Finally, the encouraging key finding is that the negative impact of a grid supportive behaviour, additionally to its primary purpose, is less than 1 % of the revenues. This may encourage distribution grid and battery operators to consider the integration of large scale batteries in distribution grids as part of the solution of a rising share of a decentralised renewable energy generation.Postprint (author's final draft

Techno-economic assessment of flexibility options versus grid expansion in distribution grids

In this paper five different flexibility options are analysed from a techno-economic perspective as alternatives to traditional grid expansion for a specific distribution grid in Germany. The options are: two reactive power control strategies with photovoltaic inverters (as a function of the power feed-in, or of the voltage at the connection point), one residential and two large scale battery storage applications (primary control reserve with autonomous reactive power control or self consumption maximisation strategy with autonomous reactive power control). For the pilot grid located in Southern Germany a photovoltaic expansion pathway is determined. The main goal of this work is to quantify the grid expansion actions that can be avoided by applying these five flexibility options for the assumed expansion pathway, focusing on large scale battery storages. It is shown that the five flexibility options increase the hosting capacity for PV systems, compared to a scenario without, by up to 45%. Furthermore, the results of the economic assessment indicate that the analysed flexibility options might be a viable alternative to traditional grid expansion as all of them show a cost reduction potential for the pilot region. These results could encourage DSOs to consider the integration of additional PV and battery storage systems not as a problem which triggers grid expansion, but as part of the solution reducing future grid expansion costs.Objectius de Desenvolupament Sostenible::7 - Energia Assequible i No ContaminantPostprint (author's final draft

Technical and economic comparison of grid supportive vanadium redox flow batteries for primary control reserve and community electricity storage in Germany

Aquesta és una còpia de la versió author’s final draft d'un article publicat a la revista [International journal of energy research]. URL d'aquest document a UPCommons E-prints: http://hdl.handle.net/2117/127058Primary control reserve and maximising self-consumption are currently two of the main applications for large-scale battery storage systems. Although being currently the most profitable application for large-scale batteries in Germany, storage systems applying primary control reserve have not been implemented in a grid supportive manner in distribution grids yet. Despite a current unfavourable regulatory framework and reimbursement scheme for community electricity storages in Germany, they are potentially more profitable than residential storages, which is mainly due to their economy of scale, and thus they may become the major large scale battery application in the future. The two applications: primary control reserve and maximising self-consumption, are combined with a grid supportive behaviour by providing reactive power control and/or peak shaving and are fitted to a vanadium redox flow battery prototype, which is installed in a distribution grid in southern Germany. Based on measured data from the prototype, two battery models for two different time resolutions (1s, 1min) are presented in detail along with their respective operation models. The operation strategy model for primary control reserve comprises the so-called degrees of freedom used to reduce the energy needed to recharge the battery. The operation strategy to maximise self-consumption is based on a persistence forecast. The model for the operation strategy for a grid supportive primary control reserve was validated in a field test revealing a relative error of 2.5 % between the simulated and measured state of charge of the battery for a multi-week time period. The technical assessment of both applications shows that the use of the degrees of freedom can reduce the energy to recharge the battery by 20 %; and in the case of self-consumption, the curtailment losses can be kept under 1 %. The economic assessment, however, indicates that even for the most promising primary control reserve case, the investment costs of vanadium redox flow batteries must be reduced by at least 30 % in order to break even. Finally, the encouraging key finding is that the negative impact of a grid supportive behaviour, additionally to its primary purpose, is less than 1 % of the revenues. This may encourage distribution grid and battery operators to consider the integration of large scale batteries in distribution grids as part of the solution of a rising share of a decentralised renewable energy generation

Increasing the hosting capacity of distribution grids by implementing residential PV storage systems and reactive power control

The rapidly increasing number of implemented photovoltaic (PV) systems in the German distribution grid in recent years has led to power quality issues due to the intermittent generation and reverse power flows in periods of low demand. In order to decrease this impact, different solutions are being investigated. The aim of this study is to analyze the maximum possible grid relief by using residential PV storage systems and different reactive power control strategies from the viewpoint of a distribution system owner. To compare the different voltage control method scenarios the hosting capacity is used as a performance indicator

Increasing the hosting capacity of distribution grids by implementing residential PV storage systems and reactive power control

The rapidly increasing number of implemented photovoltaic (PV) systems in the German distribution grid in recent years has led to power quality issues due to the intermittent generation and reverse power flows in periods of low demand. In order to decrease this impact, different solutions are being investigated. The aim of this study is to analyze the maximum possible grid relief by using residential PV storage systems and different reactive power control strategies from the viewpoint of a distribution system owner. To compare the different voltage control method scenarios the hosting capacity is used as a performance indicator

Ezetimibe - A clinically effective and a cost-effective treatment option for dyslipidaemia

Although statins are first-line treatment for most patients with dyslipidaemia, some people require additional or alternative treatment to modify their lipid profile. Many patients treated with statins still fail to achieve increasingly stringent LDL-C goals in clinical practice, and can benefit from add-on ezetimibe therapy, which has a complementary mechanism of action to other drugs in current use. Many clinical studies have demonstrated that combinations of ezetimibe with statins, fibrates, and other lipid-modifying therapies, provide better normalisation of lipid profiles than these drugs given as monotherapy. Moreover, ezetimibe is also effective as a monotherapy. The safety and tolerability profile of ezetimibe as monotherapy is similar to placebo, and is also excellent when given in combination with other lipid-modifying agents. Ezetimibe may also provide a cost-effective alternative to statin titration. These findings suggest that ezetimibe represents a useful alternative and adjunct to other lipid management strategies. © 2008 CSF Medical Communications Ltd

Ezetimibe - A clinically effective and a cost-effective treatment option for dyslipidaemia

Although statins are first-line treatment for most patients with dyslipidaemia, some people require additional or alternative treatment to modify their lipid profile. Many patients treated with statins still fail to achieve increasingly stringent LDL-C goals in clinical practice, and can benefit from add-on ezetimibe therapy, which has a complementary mechanism of action to other drugs in current use. Many clinical studies have demonstrated that combinations of ezetimibe with statins, fibrates, and other lipid-modifying therapies, provide better normalisation of lipid profiles than these drugs given as monotherapy. Moreover, ezetimibe is also effective as a monotherapy. The safety and tolerability profile of ezetimibe as monotherapy is similar to placebo, and is also excellent when given in combination with other lipid-modifying agents. Ezetimibe may also provide a cost-effective alternative to statin titration. These findings suggest that ezetimibe represents a useful alternative and adjunct to other lipid management strategies. © 2008 CSF Medical Communications Ltd