Connection of renewable energy sources to the power grid

Diplomová práce se zabývá obnovitelnými zdroji energie a druhy, které se nejvíce využívají. Teoretická část je věnována obecným informacím o obnovitelných zdrojích energie, typech elektráren a v další části se zaměřuje na fotovoltaické elektrárny. Praktická část ilustruje připojení fotovoltaické elektrárny do sítě vysokého napětí (22kV) ve Středočeském kraji. Dále jsou v práci uvedena pravidla pro připojení rozptýlených výroben elektřiny z obnovitelných zdrojů energie do distribuční sítě, napěťový profil podél vedení před a po připojení FVE do distribuční sítě.This thesis deals with the renewable energy and its main types. The theoretical part is about the general information on renewable energy sources, types of power plants, focusing on photovoltaic power plants. The practical part illustrates the connection of photovoltaic power plant to a medium voltage network (22kV) in Central Bohemia region. The following part is devoted to the rules for connecting dispersed energy sources to the distribution network, voltage profile along the lines before and after connecting the PVPP's into the distribution network

Small-scale (≤6 kWe) stand-alone and grid-connected photovoltaic, wind, hydroelectric, biodiesel, and wood gasification system's simulated technical, economic, and mitigation analyses for rural regions in Western Australia

This research develops models and simulations of technical performance, net emission reductions, and discounted market values of thirteen small-scale (≤6 kWe) renewable energy projects. The research uses a simple methodology suitable for small private entities and governments to compare alternative investment options for both climate change mitigation and adaptation in the southwest of Western Australia. The system simulation and modelling results indicate that privately-owned, small-scale, grid-connected renewable energy systems were not competitive options for private entities relative to sourcing electricity from electricity networks, despite subsidies. The total discounted capital and operating costs, combined with the minimal mitigation potentials of the small-scale renewable energy systems resulted in unnecessarily high electricity costs and equivalent carbon prices, relative to grid-connection and large-scale clean energy systems. In contrast, this research suggests that small-scale renewable energy systems are cost-effective for both private entities and governments and exhibit good mitigation potentials when installed in remote locations far from the electricity network, mostly displacing diesel capacity

Development and demonstration of a renewable energy based demand/supply decision support tool for the building design profession

Future cities are likely to be characterised by a greater level of renewable energy systems deployment. Maximum impact will be achieved when such systems are used to offset local energy demands in contrast to current philosophy dictating the grid connection of large schemes. This paper reports on the development of a software tool, MERIT, for demand/ supply matching. The purpose of MERIT is to assist with the deployment of renewable energy systems at all scales. This paper describes the procedures used to match heterogeneous supply technologies to a set of demand profiles corresponding to the different possible fuel types

Voltage-based droop control of renewables to avoid on-off oscillations caused by overvoltages

To achieve the environmental goals set by many governments, an increasing amount of renewable energy, often delivered by distributed-generation (DG) units, is injected into the electrical power system. Despite the many advantages of DG, this can lead to voltage problems, especially in times of a high local generation and a low local load. The traditional solution is to invest in more and stronger lines, which could lead to massive investments to cope with the huge rise of DG connection. Another common solution is to include hard curtailment; thus, ON-OFF control of DG units. However, hard curtailment potentially leads to ON-OFF oscillations of DG and a high loss of the available renewable energy as storage is often not economically viable. To cope with these issues, applying a grid-forming control in grid-connected DG units is studied in this paper. The voltage-based droop control that was originally developed for power sharing in islanded microgrids, enables an effective way for soft curtailment without communication. The power changes of the renewable energy sources are delayed to more extreme voltages compared to those of the dispatchable units. This restricts the renewable energy loss and avoids ON-OFF oscillations

Grid Connected Renewable Energy Sources and Net Metering: A Review

In this paper, the constraints of a grid connection are presented along with some of the solutions to the problems as proposed by various researchers. Non-renewable energy sources are getting exhausted day by day. There is a need for alternative sources of energy. In this paper, various constraints in the incorporation of grid-connected renewable energy sources and the required solution are discussed. The concept of net metering and associated challenges are presented in this paper

RETS Revisited : Connecting renewables to the grid - a report by the Transmission Working Group of the Department of Trade & Industry

The aim of RETS Revisited is to review the progress that has occurred since the original RETS Report in June 2003. Given the large amount of wind generation planned, and the fact that much of it does not yet have planning consent or firm grid connection offers, it was felt that it would be helpful to take a further strategic look forward, rather than simply relying on the existing system to react to individual connection applications as and when required. RETS Revisited therefore: K considers the current likely volumes of new renewable generation, the timescales for this generation to be ready for connection to the transmission system and transmission issues impacting on the delivery of projects. K considers the effects on costs to the consumer of the rate of development of the transmission system in accommodating renewable energy to meet Government targets. K makes recommendations for action in order to connect sufficient renewables to meet the 2010 target and the aspirations beyond to 2020. Government policy is clear on the requirement for more renewable energy, and there is a market instrument, the Renewables Obligation, in place until 2027 which is driving the development of renewable projects. The Energy White Paper in 2003 recognised the need for the remodelling of the transmission grid to accept generation in new locations. Wind will be the technology capable of delivering significant capacity by 2010 and beyond. By its very nature the technology has limited ability to respond to locational price signals. In order for new generation projects to be connected, there needs to be a parallel development of transmission infrastructure. Transmission upgrades of over £560m were approved by Ofgem in December 20041. These will assist the flows of electricity from Scotland. There is a need to ensure that these projects are not unduly delayed in construction. A review of the need for the linkage between upgrades to the Scotland-England interconnectors and Beauly-Denny line should be carried out now

Microgrids

Integration of renewable energy sources in the electrical power system is key for enabling the decarbonization of that system. The connection of renewable generation to the electrical system is being performed in a centralized form (large renewable power plants like wind or solar power plants connected at the transmission system) and in a decentralized manner (through the connection of dispersed generation connected at the distribution system). The connection of renewable generation at distribution levels, together with other generating sources as well as energy storage systems (the so-called DER, Distributed Energy Resources) close to consumption sites, is promoting the development of microgrids: DER installations that have the capability to operate grid connected and grid isolated. The uncertainty and variability of the renewable energy sources that integrate microgrids, as well as the need for coordination with other energy sources, pose challenges in the operation, protection, control, and planning of microgrids. The five selected papers published in this Special Issue propose solutions to address these challenges.Peer ReviewedObjectius de Desenvolupament Sostenible::7 - Energia Assequible i No ContaminantObjectius de Desenvolupament Sostenible::7 - Energia Assequible i No Contaminant::7.1 - Per a 2030, garantir l’accés universal a serveis d’energia assequibles, confiables i modernsObjectius de Desenvolupament Sostenible::7 - Energia Assequible i No Contaminant::7.2 - Per a 2030, augmentar substancialment el percentatge d’energia renovable en el con­junt de fonts d’energiaPostprint (published version

Integrating Distributed Generation: Regulation and Trends in Three Leading Countries

We explore trends in the deployment and integration of distributed generation in Germany, Denmark and Sweden. In particular, we examine the regulation of renewable energy generation with a focus on grid access and connection mechanisms. The high rate of distributed generation penetration in these countries is the result of early support given to the expansion of renewable energy generation – mainly wind and solar - within their respective national policies. Germany and Denmark are the countries with the most sophisticated support schemes, which have shown changes over time. In terms of connections, Germany is the country with the most favourable connection regime. It provides not only priority connection but also priority use of the grid to generation units that produce electricity from renewable energy sources. Sweden guarantees equal treatment among different technologies (i.e. a non-discrimination principle) and is thus the least favourable. High connection costs have been observed, especially in Germany and Denmark. The costs of network upgrades are usually socialised across customers. The use of smart solutions combined with novel business models might allow more efficient use of the current distribution electricity infrastructure. Hence, integration issues should be taken into consideration in order to avoid expansion of distributed generation in a way that unnecessarily raises total system costs, via high connection costs

Integrating distributed generation: regulation and trends in three leading countries

This paper explores the trends in the deployment and integration of distributed generation in Germany, Denmark and Sweden. The study concentrates on the regulation of renewable energy generation with a focus on grid access and connection mechanisms. The high rate of distributed generation penetration is mainly based on the early support that these countries gave to the expansion of renewable energy generation – mainly wind and solar – within their respective national policies. Germany and Denmark are the ones with the most sophisticated support schemes, which have shown a dynamic design over time. In terms of connections, Germany has the most favorable connection regime which provides not only priority connection but also priority grid access for generation units that produce electricity from renewable energy sources. Sweden guarantees equal treatment among different technologies (i.e. a non-discrimination principle). High connection costs have been observed specially in Germany and Denmark. The costs of network upgrades are usually socialised across demand customers. However, integration issues should be taken into consideration in order to avoid expansion of distributed generation in a way which unnecessarily raises total system costs, via high connection costs.The authors wish to acknowledge the financial support of UK Power Networks via the Low Carbon Networks Fund’s Flexible Plug and Play project

Energy Production Analysis and Optimization of Mini-Grid in Remote Areas: The Case Study of Habaswein, Kenya

Rural electrification in remote areas of developing countries has several challenges which hinder energy access to the population. For instance, the extension of the national grid to provide electricity in these areas is largely not viable. The Kenyan Government has put a target to achieve universal energy access by the year 2020. To realize this objective, the focus of the program is being shifted to establishing off-grid power stations in rural areas. Among rural areas to be electrified is Habaswein, which is a settlement in Kenya’s northeastern region without connection to the national power grid, and where Kenya Power installed a stand-alone hybrid mini-grid. Based on field observations, power generation data analysis, evaluation of the potential energy resources and simulations, this research intends to evaluate the performance of the Habaswein mini-grid and optimize the existing hybrid generation system to enhance its reliability and reduce the operation costs. The result will be a suggestion of how Kenyan rural areas could be sustainably electrified by using renewable energy based off-grid power stations. It will contribute to bridge the current research gap in this area, and it will be a vital tool to researchers, implementers and the policy makers in energy sector