Power-to-ammonia in future North European 100 % renewable power and heat system

Power-to-gas and other chemicals-based storages are often suggested for energy systems with high shares of variable renewable energy. Here we study the North European power and district heat system with alternative long-term storage, the power-to-ammonia (P2A) technology. Assuming fully renewable power and heat sectors and large-scale electrification of road transport, we perform simultaneous optimization of capacity investments and dispatch scheduling of wind, solar, hydro and thermal power, energy storages as well as transmission, focusing on year 2050. We find that P2A has three major roles: it provides renewable feedstock to fertilizer industry and it contributes significantly to system balancing over both time (energy storage) and space (energy transfer). The marginal cost of power-based ammonia production in the studied scenarios varied between 431 and 528 €/t, which is in the range of recent ammonia prices. Costs of P2A plants were dominated by electrolysis. In the power and heat sector, with our cost assumptions, P2A becomes competitive compared to fossil natural gas only if gas price or CO₂ emission price rises above 70 €/MWh or 200 €/tCO₂.     

Towards 100% renewable energy systems: Uncapping power system flexibility

Relying almost entirely on energy from variable renewable resources such as wind and solar energy will require a transformation in the way power systems are planned and operated. This paper outlines the necessary steps in creating power systems with the flexibility needed to maintain stability and reliability while relying primarily on variable energy resources. These steps are provided in the form of a comprehensive overview of policies, technical changes, and institutional systems, organized in three development phases: an initial phase (penetration up to about 10%) characterized by relatively mild changes to conventional power system operations and structures; a dynamic middle phase (up to about 50% penetration) characterized by phasing out conventional generation and a concerted effort to wring flexibility from existing infrastructure; and the high penetration phase that inevitably addresses how power systems operate over longer periods of weeks or months when variable generation will be in either short supply, or in over-abundance. Although this transition is likely a decades-long and incremental process and depends on the specifics of each system, the needed policies, research, demonstration projects and institutional changes need to start now precisely because of the complexity of the transformation. The list of policy actions presented in this paper can serve as a guideline to policy makers on effectuating the transition and on tracking the preparedness of systems.     

Effect of wind energy system performance on optimal renewable energy model-an analysis

The Optimal Renewable Energy Model (OREM) has been developed to determine the optimum level of renewable energy sources utilisation in India for the year 2020–21. The model aims at minimising costefficiency ratio and determines the optimum allocation of different renewable energy sources for various end-uses. The extent of social acceptance level, potential limit, demand and reliability will decide the renewable energy distribution pattern and are hence used as constraints in the model. In this paper, the performance and reliability of wind energy system and its effects on OREM model has been analysed. The demonstration windfarm (4 MW) which is situated in Muppandal, a village in the southern part of India, has been selected for the study. The windfarm has 20 wind turbine machines of 200 KW capacity. The average technical availability, real availability and capacity factor have been analysed from 1991 to 1995 and they are found to be 94.1%, 76.4% and 25.5% respectively. The reliability factor of wind energy system is found to be 0.5 at 10,000 hours. The OREM model is analysed considering the above said factors for wind energy system, solar energy system and biomass energy systems. The model selects wind energy for pumping end-use to an extent of 0.3153×10¹⁵ KJ.     

A mobile renewable house using PV/wind/fuel cell hybrid power system

A photovoltaic/wind/fuel cell hybrid power system for stand-alone applications is proposed and demonstrated with a mobile house. This concept shows that different renewable sources can be used simultaneously to power off-grid applications. The presented mobile house can produce sufficient power to cover the peak load. Photovoltaic and wind energy are used as primary sources and a fuel cell as backup power for the system. The power budgeting of the system is designed based on the local data of solar radiation and wind availability. Further research will focus on the development of the data acquisition system and the implementation of automatic controls for power management.     

A hybrid model for the optimum integration of renewable technologies in power generation systems

The main purpose of this work is to assess the unavoidable increase in the cost of electricity of a generation system by the integration of the necessary renewable energy sources for power generation (RES-E) technologies in order for the European Union Member States to achieve their national RES energy target. The optimization model developed uses a genetic algorithm (GA) technique for the calculation of both the additional cost of electricity due to the penetration of RES-E technologies as well as the required RES-E levy in the electricity bills in order to fund this RES-E penetration. Also, the procedure enables the estimation of the optimum feed-in-tariff to be offered to future RES-E systems. Also, the overall cost increase in the electricity sector for the promotion of RES-E technologies, for the period 2010–2020, is analyzed taking into account factors, such as, the fuel avoidance cost, the carbon dioxide emissions avoidance cost, the conventional power system increased operation cost, etc. The overall results indicate that in the case of RES-E investments with internal rate of return (IRR) of 10% the cost of integration is higher, compared to RES-E investments with no profit, (i.e., IRR at 0%) by 0.3–0.5 €c/kWh (in real prices), depending on the RES-E penetration level.     

Technical assessment of the use of a small-scale wind power system to meet the demand for electricity in a land aquafarm in Taiwan

Due to the widespread aquaculture at coastal area in Taiwan and high wind power potential in the sites, it is worthy to carry out the technical potential assessments of small-scale wind power system used for aquaculture in Taiwan. The present work analyzed wind power potential, described the practical installation, measured the actual energy output, verified the reliability of the energy output estimation method and elucidated important considerations associated with the use of this estimation method. The relationship between the actual energy generated and the wind speed characteristics were thus introduced. The power quality produced by a small-scale wind power generator was also evaluated.     

Carbon pricing and the diffusion of renewable power generation in Eastern Europe: A linear programming approach

The purpose of this paper is to analyze the costs for reducing CO₂ emissions in the power-generating sectors in Croatia, the European part of Russia, Macedonia, Serbia and the Ukraine in 2020 by using a linear programming model. The model takes into account the impact of technology learning and is based on the underlying assumptions of the so-called RAINS model frequently used to assess the potential and the costs for reducing air pollution in Europe. The results based on an exogenously given 15 percent reduction target for CO₂ emissions show that the marginal cost for switching from a carbon-intense fuel to either a low-carbon or to a renewable energy source differs significantly among the countries. The marginal costs range from 4 to 90€ per ton CO₂, and are mainly due to country differences in the availability of renewables, existing technologies and costs. The results also indicate that although it is clear that the Eastern European countries are not homogeneous in terms of CO₂ abatement potential and costs, no general conclusions can be made of the region. This may have important implications for future JI/CDM activities. For instance, risk factors such as policy uncertainty and institutional obstacles may become crucial in determining the future allocation of JI/CDM projects across the region.     

Decision-making between a grid extension and a rural renewable off-grid system with hydrogen generation

Most populations in rural Africa have no access to electricity, in this study, a comparative analysis between grid extension and the implementation of renewable off-grid hybrid power system is carried out. The objective of the study is to determine the best feasible option. Napier, a farming village in the Western Cape province of South Africa was selected as the site for the comparative analysis and HOMER PRO software was used to develop an optimal system using the wind and solar resources of the selected site. The load profile considered in the analysis includes lighting, cooking and hot water demands. The best feasible option is determined based on the Net Present Cost of each feasible scenario. Sensitivity analysis on the current cost and the projected cost of hydrogen storage w conducted to observe the impact of the cost of hydrogen storage on the renewable off-grid system cost of energy.     

Challenges and options for a large wind power uptake by the European electricity system

The contribution of renewable energies (in particular of wind power) to the electrical power generation has been continuously increasing in the recent decades. This article focuses on the necessary options that manage the variability of wind turbine output and enable the large scale integration of wind power with the current electricity system, such as additional power reserves, distributed storage technologies, in particular electric vehicles, and cross-boarder power transmission. The influence of geographical distribution of wind turbines on the produced power variability is described as well. The article highlights that even though state-of-art technologies for higher wind integration are present, there is a necessity for the proper management and integration of mentioned options.     

Modelling of energy systems with a high percentage of CHP and wind power

This paper presents the energy system analysis model EnergyPLAN, which has been used to analyse the integration of large scale wind power into the national Danish electricity system. The main purpose of the EnergyPLAN model is to design suitable national energy planning strategies by analysing the consequences of different national energy investments. The model emphasises the analysis of different regulation strategies and different market economic optimisation strategies.At present wind power supply 15% of the Danish electricity demand and ca 50% is produced in CHP (combined heat and power production). The model has been used in the work of an expert group conducted by the Danish Energy Agency for the Danish Parliament. Results are included in the paper in terms of strategies, in order to manage the integration of CHP and wind power in the future Danish energy supply in which more than 40% of the supply is expected to come from wind power.     

Large scale wind power integration in China: Analysis from a policy perspective

Between 2006 and 2010 the installed capacity of wind power in China has doubled and by 2010 China's cumulative installed capacity of wind power ranked the first in the world, surpassing the United States. However, the rapid expansion of installed capacity has not been matched by grid connection, and this deficiency has aroused the concern of both policy makers and scholars. Unlike most of the current studies which focus on technical strategies in China's wind power industry, this paper analyzes the problem from a policy perspective. The paper analyzes the four challenges that large scale wind power integration in China faces: the uncoordinated development between wind power capacity and power grids; the lack of suitable technical codes for wind power integration; the unclear nature of the grid companies’ responsibility for grid connection; and the inadequate economic incentives for grid enterprises. To address these problems, the paper recommends that the government: formulates policies to better coordinate the development of wind power and the planning and construction of power grids; establishes grid codes that reflect in particular the requirements to be met by users of power transmission and distribution networks; and integrates administrative intervention and economic incentive policies to stimulate the grid enterprises’ enthusiasm to absorb wind power generation.     

Automation infrastructure and operation control strategy in a stand-alone power system based on renewable energy sources

The design of the automation system and the implemented operation control strategy in a stand-alone power system in Greece are fully analyzed in the present study. A photovoltaic array and three wind generators serve as the system main power sources and meet a predefined load demand. A lead-acid accumulator is used to compensate the inherent power fluctuations (excess or shortage) and to regulate the overall system operation, based on a developed power management strategy. Hydrogen is produced by using system excess power in a proton exchange membrane (PEM) electrolyzer and is further stored in pressurized cylinders for subsequent use in a PEM fuel cell in cases of power shortage. A diesel generator complements the integrated system and is employed only in emergency cases, such as subsystems failure. The performance of the automatic control system is evaluated through the real-time operation of the power system where data from the various subsystems are recorded and analyzed using a supervised data acquisition unit. Various network protocols were used to integrate the system devices into one central control system managing in this way to compensate for the differences between chemical and electrical subunits. One of the main advantages is the ability of process monitoring from distance where users can perform changes to system principal variables. Furthermore, the performance of the implemented power management strategy is evaluated through simulated scenarios by including a case study analysis on system abilities to meet higher than expected electrical load demands.     

Dynamic model of wind energy conversion systems with variable speed synchronous generator and full-size power converter for large-scale power system stability studies

This paper presents a dynamic model for variable speed wind energy conversion systems, equipped with a variable pitch wind turbine, a synchronous electrical generator, and a full power converter, specially developed for its use in power system stability studies involving large networks, with a high number of buses and a high level of wind generation penetration. The validity of the necessary simplifications has been contrasted against a detailed model that allows a thorough insight into the mechanical and electrical behavior of the system, and its interaction with the grid. The developed dynamic model has been implemented in a widely used power system dynamics simulation software, PSS/E, and its performance has been tested in a well-documented test power network.     

A transition toward a market expansion phase: Policies for promoting wind power in Taiwan

Considering the significant issues on global warming and environmental protection, the energy sector needs a long-term policy, by which renewable energies gradually replace conventional fossil fuels. In terms of an energy system, the development of renewable energies implies a challenge to existing energies like fossil fuels and nuclear power that have been for decades equipped with sound infrastructure and regulations. And a transformation of the energy system cannot expect any achievement without overcoming considerable opposition from vested interests involved with the fossil fuels technologies.     

Education and training in renewable energy sources in Serbia and Montenegro

This paper reports the status of Education and Training in Renewable Energy Sources (RES) in Serbia and Montenegro (SAM) at the end of May 2003. It was found that universities in SAM do not give diplomas in RES. RES subjects primarily solar and wind energy are taught at graduate levels. RES units are taught as a part of some classical engineering disciplines at undergraduate level especially in solar and biomass energy. Teaching is mainly at encyclopedic level and staff is mainly trained in general fields. This education may be regarded as unsatisfactory and should be expanded and intensified in future.     

Rural electrification of a remote island by renewable energy sources

India has a large number of remote small villages and islands that lack in the electricity, and probability of connecting them with the high voltage gridlines in the near future is very poor due to financial and technical constraints. The main electrical load in these villages is domestic. In this paper a study has been presented for sustainable development of renewable energy sources to fulfill the energy demands of a remote island having a cluster of five villages. The total potential of electricity from these resources is estimated to be equivalent to 3530 kWh/day whereas demand is only 2310 kWh/day with an installed capacity of 450 kW, which is sufficient to replace the existing power generation system dominated by diesel operated system.     

Successful renewable energy development in a competitive electricity market: A Texas case study

The development of renewable energy in markets with competition at wholesale and retail levels poses challenges not present in areas served by vertically-integrated utilities. The intermittent nature of some renewable energy resources impact reliability, operations, and market prices, in turn affecting all market participants. Meeting renewable energy goals may require coordination among many market players.     

An application of a combined wind and solar energy system in Izmir

In this work, a combined system which is produced electrical energy from both solar radiation via solar cells and wind energy by using wind turbine was studied. For wind energy, measurements of wind velocities at 12 m height were taken. Then, these values were calculated for 42 m by using Hellmann equation. After that, wind energy converted to the electrical energy. However, value of solar radiation from solar cells was taken at the optimum slope angle of collector which provided higher energy production for each 1 h during this application. Thus, obtained data from each system were used together for finding total energy. For this study, measurements, which would be used in calculation of wind energy and solar energy were taken for four years between 1995 and 1998 in Izmir. As a result, energy of the combined system could support each other when one of them produces energy insufficiently.     

Critical evaluation of solar chimney power plant performance

This paper evaluates the influence of a recently developed convective heat transfer equation, more accurate turbine inlet loss coefficient, quality collector roof glass and various types of soil on the performance of a large scale solar chimney power plant. Results indicate that the new heat transfer equation reduces plant power output considerably. The effect of a more accurate turbine inlet loss coefficient is insignificant, while utilizing better quality glass enhances plant power production. Models employing Limestone and Sandstone soil produce virtually similar results to a Granite-based model. The plant collector height is found to differ from previously obtained optimal values.