Renewable Energy Electricity Generation Research Articles

Improving the load flexibility of coal-fired power plants by the integration of a thermal energy storage

Improving the flexibility of conventional power plants is one key challenge for the transformation of the energy system towards a high share of renewable energies in electricity generation. Flexible and dispatchable power plants will contribute to this ongoing transformation process as they compensate the fluctuating electricity generation from renewable energy sources such as wind and photovoltaics. In this context, dynamic simulation models offer an efficient tool to evaluate flexibility measures and the resulting highly transient power plant operation. In this paper, the buildup of a dynamic power plant model using the modeling language Modelica in the simulation environment Dymola is presented. The detailed dynamic power plant model is validated successfully against measurement data from the underlying coal-fired reference power plant. The paper then focuses on the integration of a steam accumulator – also known as a Ruths storage – into the power plant process in order to increase its flexibility. The results of the dynamic simulations show that charging the steam accumulator leads to a reduction of the net power up to 7.0%. By discharging the Ruths storage an additional net power of 4.3% can be activated very quickly. Thus, the storage integration leads to an improved load flexibility with regard to a temporary reduction of the minimum load as well as to the possibility of performing a load change at a constant firing rate (e.g. to participate on the quarter-hourly intraday markets). Furthermore, the integrated energy storage enhances the provision of primary control reserve significantly by ±2.8%.

Process development of silica extraction from RHA: a cradle to gate environmental impact approach.

India is one of the major rice-producing countries. Rice husk is a major agricultural by-product from rice production, which is used as a fuel in boilers. Its use as fuel produces huge amounts of silica-rich rice husk ash (RHA). This paper aims at providing an overall assessment of environmental impacts associated with the extraction of silica from RHA-a process developed by our study group. The functional unit used in this study is production of 100kg of silica. The analysis included the extraction and transportation of other raw materials; RHA was assumed to be processed at the site. The study was conducted in accordance with the international ISO 14040 procedural framework. LCA is performed using GaBi Education software, and five midpoint indicators are chosen to assess the environmental impacts of silica extraction. The overall climate change (CC) of the extraction process is 7.26kg CO2 equivalent per kg of silica produced. A high contribution of calcination to CC is attributed to the use of electricity. The comprehensive environmental impacts of silica-rich RHA resulting from processing of RHA and improvement options to achieve sustainable production are presented. The negative impacts that can be avoided during silica extraction are also discussed. It is observed that calcination is a major contributor to the overall environmental indicators. The work also stresses on the use of renewable energy for electricity generation, which would help in decreasing the overall greenhouse gas emissions during extraction while ensuring waste utilization.

Setting course for demand response in the service sector

The increasing share of renewable energies in electricity generation is within the scope of the energy transition and will lead to a more volatile generation of electricity. A more flexible energy demand could contribute to handling the resulting challenges in electricity grid management. The service sector is one of the target groups for utilizing flexible demand, also called demand response (DR). Supermarkets, hotels, and office buildings can be found in regions throughout Germany. This could be an advantage regarding the compensation of grid instability in any region, compared to more locally focused industrial enterprises. First estimations point out considerable unused DR potentials for the service sector. However, currently, there is less knowledge about flexibility options in the service sector than in industry. Moreover, market barriers, such as a missing adequate regulatory framework offering attractive incentives prevent that the potentials are tapped. Therefore, in this paper, we first analyze survey data from 1.000 enterprises of the service sector in Germany to identify subsectors that have a high share of flexible cross-sectoral technologies in electricity consumption. Data indicates that the subsectors trade, restaurants, and hotels as well as office-like buildings are the most promising subsectors of the service sector regarding demand response potential, since they have a high stock in flexible cooling appliances, air conditioning, and ventilation. In a second step, we conducted stakeholder interviews, to find specific barriers, drivers, and possible starting points in each of the identified subsectors. Still unapt or missing regulatory framework conditions, low profitability, and a lack of knowledge regarding flexibility potentials and marketing mechanisms seem to be the main barriers. However, framework conditions promoting demand response measures are improving, e.g., technical standards and latest regulatory revisions. This indicates that in order to tap the existing demand response potentials in the service sector, the value of flexibility in demand needs to be appreciated, e.g., by facilitating market participation or by creating offers resp. rewarding the enterprises’ flexibility of demand. In addition, addressing demand response issues in already existing policy measures, such as energy audits could raise awareness and knowledge.

The impact of renewable energy on household electricity prices in liberalized electricity markets: A cross-national panel data analysis

The main research questions addressed in this paper are: first, have electricity market reforms achieved lower household electricity prices and, second, has the introduction of renewable energy increased household electricity prices in deregulated markets Answers to the questions were derived using static and dynamic panel data analysis from 1991 to 2014 employing explanatory variables such as the extent of electricity market reform and the share of generation from renewable energy resources. The dynamic model suggests that a lower household electricity price is associated with the degree of electricity market reform, while the share of renewable energy in electricity generation is not statistically significant.

Novel energy management method for suppressing fuel cell degradation in hydrogen and electric hybrid energy storage systems compensating renewable energy fluctuations

This research investigates an energy management method utilized in a hydrogen and electric hybrid energy storage system (HESS), which is utilized as an ancillary system for renewable energy electricity generation. To suppress the performance degradation of the fuel cell (FC), the newly proposed energy management method deals with main FC degradation causes, such as low humidification and frequent and rapid voltage changes. The entire HESS's performance is demonstrated using the proposed energy management method. In addition, a simulation is conducted to evaluate the proposed energy management method's performance in terms of both suppressing the FC's degradation and ensuring system efficiency. The results of the experiment and simulation show that the proposed energy management method can suppress the FC's harmful working states while maintaining high system efficiency.

Smart Over Speed Protection of Zafarana Grid-connected Wind Farm during Wind Gust Conditions

The increasing share of renewable energy in electricity generation requires an effective operation and protection scheme using Smart Grid (SG) technologies. Smart meters of SG allow the transfer of the measured signals in the wind farm to the operation and protection centre of the SG. Such signals transmission can improve the farm performance and reduce system cost. The secure operation of wind farms requires an efficient over speed protection of the turbines under wind gust conditions. Therefore, this paper is concerned with integration of a new over speed protection algorithm with the existing protection centre in SG. The main objective of the proposed algorithm is the dynamic updating of Critical Clearing Time (CCT) for over speed protective relays against severe wind gusts to minimize loss of life and component damage. In this respect, long-term data of wind speed of Zafarana farm have been collected and processed to define gust intensity and its distribution Moreover, the geographical farm area is classified to different rows according to the recorded gust values. A smart relay setting will be formulated by developing heuristic algorithm, which relates CCT with the gust intensity, and its row along the geographical area of Zafarana farm. Accordingly, general two variables second order function will propose to identify the dynamic CCT based on wind speed measured by smart meters installed on each wind farm row. The digital relay settings are updated according to the determined CCT using the communication facilities existing in the SG. The simulation results indicate that the proposed over speed protection improves significantly the performance of the grid connected wind farm under wind gust conditions.

Studies on the Electrification of the Transport Sector in the Island of Crete, Greece

The possibility of electrifying the transport sector in Crete, Greece has been investigated. Currently the conventional vehicles in Crete consume annually 316,872 tons of gasoline and diesel oil emitting 1,030,188 tons of CO2. Electrification of the transport sector in Crete will result in a decrease of imported fossil fuels use and a reduction of CO2 emissions. It will also increase the use of locally available renewable energies in electricity generation. If all the existing conventional vehicles in Crete were to be replaced by electric vehicles, the annual electricity requirements in their batteries would be 1,092,568 to 1,311,077 MWh depending on the type of battery. The energy demand of the electric cars could be covered with electricity generated by renewable energies including solar and wind energy which are abundant in the island. The batteries of the electric cars could be used as electricity storage devices facilitating the penetration of intermittent renewable energies, with distributed generation systems, into the smart electric grid of Crete. It has been estimated that the aggregated theoretical storage capacity of all the batteries would be 6.33 GWh and that the size of the solar-PV plants and wind energy systems, generating all the electricity required by electric vehicles, would be 728 to 874 MWp and 445 to 534 MW respectively.

Impacts of renewables and socioeconomic factors on electric vehicle demands – Panel data studies across 14 countries

Electric vehicle demands have increased rapidly since 2010, and depend on renewables and socioeconomic factors. Using panel data from fourteen countries between 2010 and 2015, we study impacts of seven factors in a multiple linear regression model. The factors include percentage of renewable energies in electricity generation, number of charging stations, education level, population density, gasoline price, GDP per capita and urbanization. The first four factors have apparent and positive impacts on the demands, and the last two factors don’t. The gasoline price affects the demands for BEVs (battery electric vehicles) more than that for PHEVs (plug-in hybrid electric vehicles). One percent increase in renewables would lead to approximately 2–6% increase in EV demands. Based on the results, policy implications are discussed.

Cuba's Energy Revolution and 2030 Policy Goals: More Penetration of Renewable Energy in Electricity Generation

Cuba has been remarkably successful at revitalising its energy sector over the last two decades, significantly increasing efficiency and reducing energy intensity and emissions. This article analyses those successes and looks at the policy challenges ahead for Cuba to achieve its 2030 energy policy goals. We argue the nascent success of the 2006 Energy Revolution is due to its comprehensive approach, targeting infrastructure, consumption habits and people's understanding of energy issues. We then examine some of Cuba's current energy challenges, presenting data on Cuba's energy mix as of 2014. We analyse the country's proposed energy policy to achieve 24% penetration of renewable energies in electricity generation by 2030. The Cuban government has an array of policy tools, from stimulating domestic production to changing foreign investment regulations, in order to achieve its goals. One of the most significant recent policy shifts includes the External Investment Law, which creates a regulatory framework and policies, including ones to utilise and develop perspectives of renewable sources of energy that will help to expedite the path toward a diverse energy mix with a large presence of renewables.

The Law and Policy for Electricity Generated by Renewable Energy: Greening the Power in Three Middle Eastern Jurisdictions

This thesis examines the law and policy concerning renewable energy electricity generation in Palestine, Jordan, and Abu Dhabi. The thesis gives greater attention to the promotion of solar power owing to the abundance and viability. It appears that energy security profoundly underpins the utilisation of renewable electricity, and the motivation of climate change mitigation also pays a role in the promotion of renewable energy in these jurisdictions. However, current policies and regulations are not fully able to promote the renewables in the power sector. The thesis submits that reforms of law and policy are necessary to enhance the achievement of environmental and energy goals.

Determinants of smallholder farmers’ continuous adoption of Jatropha as raw material for biodiesel production: a proposed model for Nigeria

ABSTRACTDespite the introduction of the Nigerian Biofuel Policy and Incentive in 2007, little is known about the impact of that policy for biodiesel development in Nigeria. The objective of this study is to explore the determinants of smallholder farmers’ continued adoption of Jatropha as raw materials for biodiesel development in northern Nigeria, with Jigawa State as an area of study. Building on the literature, this paper proposes a model for Nigeria on determinants of smallholder farmers’ continued adoption of Jatropha as raw material for biodiesel production. A pilot testing using few samples in Jigawa state revealed that the determinants composed in the proposed model are likely to influence farmers’ decision on continued adoption of Jatropha as a raw material for biodiesel production. The proposed model if further validated using larger survey samples will guide policymakers towards the enhancement of farmers’ participation and retention in the Jatropha project for biodiesel raw materials production. As a byproduct, implementing research findings from the larger sample will be employment generation, poverty reduction, combating desert encroachment, economic diversification to renewable energy sources and electricity generation using biodiesel.

Comparison of Well-to-Wheel Efficiencies for Different Drivetrain Configurations of Transit Buses

The transportation sector, especially road transport, must reduce its energy consumption and emissions significantly. This requirement also applies to road-bound public transport, which uses mainly diesel buses. A reasonable measure for reaching this goal is to electrify the vehicle's drivetrain. During the past decade, several alternative technologies have evolved, namely, hybrid electric buses, fuel cell electric buses, and battery electric buses (BEBs). For a comparison of their energy efficiency, both the drivetrain's efficiency and the efficiency of the energy supply must be examined to determine well-to-wheel efficiency. This paper attempted to compare seven drivetrains for urban transit buses: diesel, natural gas, diesel–electric, hybrid electric (series and parallel), fuel cell electric, battery electric, and trolley bus. This comparison will become the main part of a more extensive model that supports decision making in bus procurement processes. The model will be as simple as possible. This factor makes it suitable also for the practitioner's use. Therefore, an analytic approach instead of a simulation tool was used. The model's outcomes were both total and specific energy consumption of four generic bus types operating on a dedicated bus line. The result of the study found that the trolley bus, closely followed by the BEB, was the most efficient, even when the share of renewable energy in electricity generation was low. The possibility to reduce specific energy consumption by increasing the occupation rate is outlined as well.

Tailoring HYSOL: Solar Energy Contribution to Reach Full Dispatchability and Firmness in Target Markets

Renewable energies for electricity generation are traditionally considered a risk for the electricity system due to their lack of dispatchability and firmness. Renewable energies penetration is constrained to strong grids or else its production must be limited to ensure grid stability, which is kept by the usage of hydropower energy or fossil-fueled power plants. CSP technology has an opportunity to arise not only as a dispatchable and firm technology, but also as an alternative that improves grid stability. To achieve that objective, solar hybrid configurations are being developed, HYSOL being the most recent solution. Three reference scenarios have been defined: Kingdom of Saudi Arabia (KSA), Northern Chile (CHL) and Baja California in Mexico (MEX), considering their respective weather conditions and market demand profile. These scenarios have been modelled, simulated and evaluated in terms of dispatchability and firmness defined by the authors. The results show that HYSOL technology has potential to become a reference in providing firm and renewable power, although a detailed design and control system are required.

Long-term effects of changing atmospheric pollution on throughfall, bulk deposition and streamwaters in a Mediterranean forest

The abatement programs implanted in Europe to reduce SO2, NO2 and NH3 emissions are here evaluated by analyzing the relationships between emissions in Spain and neighboring countries and atmospheric deposition in a Mediterranean forest in the Montseny mountains (NE Spain) for the last 3decades. A canopy budget model was applied to throughfall data measured during a period of high emissions (1995–1996) and a period of lower emissions (2011–2013) to estimate the changes in dry deposition over this time span.Emissions of SO2 in Spain strongly decreased (77%) and that was reflected in reductions for nssSO42− in precipitation (65% for concentrations and 62% for SO42-S deposition). A lower decline was found for dry deposition (29%).Spanish NO2 emissions increased from 1980 to 1991, remained constant until 2005, and decreased thereafter, a pattern that was paralleled by NO3− concentrations in bulk precipitation at Montseny. This pattern seems to be related to a higher share of renewable energies in electricity generation in Spain in recent years. However, dry deposition increased markedly between 1995 and 2012, from 1.3 to 6.7kgha−1year−1. Differences in meteorology between periods may have had a role, since the recent period was drier thus probably favoring dry deposition.Spanish NH3 emissions increased by 13% between 1980 and 2012 in Spain but NH4+ concentrations in precipitation and NH4+-N deposition showed a decreasing trend (15% reduction) at Montseny, probably linked to the reduction ammonium sulfate and nitrate aerosols to be scavenged by rainfall. NH4+-N dry deposition was similar between the compared periods.The N load at Montseny (15–17kgha−1year−1) was within the critical load range proposed for Mediterranean sclerophyllous forests (15–17.5kgha−1year−1). The onset of N saturation is suggested by the observed increasing N export in streamwaters.

Spain's energy outlook: A review of PV potential and energy export

Spain must reduce its energy consumption by 23% and achieve 100% renewable energy in electricity generation by 2030. This paper presents the current energy scenario en Spain, and the outlooks for different renewable options, with special focus on photovoltaic (PV) solar energy. In 2012, Spain was the number two European country in terms of installed rewnewable energy power. Solar PV technology has the potential to meet Spain's future energy demand and its associated environmental challenges. This paper gives a review of solar energy economy at global scale for both PV and thermal power technologies. The Spanish energy scenario shows actual trends and progress made by solar power. Economic concepts of levelised cost of electricity and grid parity are presented. The financial analysis shows that PV electricity achieves grid parity at a plant profitability rate up to 7.26%.

Mandatory versus voluntary payment for green electricity

Renewable energy sources have a critical role to play in contributing to the diversity, sustainability and security of energy supplies. The main objective of the paper is to gain an understanding of the support mechanism of renewable energy sources most preferred by households in the United Kingdom. This paper analyses households' preferences and willingness to pay under a mandatory scheme where all households contribute compared to a voluntary scheme where only those who wish to pay to support renewables do so (such as the green tariffs offered by electricity suppliers in the UK). Two contingent valuation method (CVM) surveys are used to explore whether the type of payment option has an impact on households' willingness to pay (WTP) for increasing share of renewable energy in electricity generation. The paper also investigates whether the type of payment mode affects respondents' self-reported certainty of paying their stated valuations. The results indicate that the likelihood of paying a positive amount for supporting renewable energy is higher under a mandatory scheme compared to a voluntary payment option in the UK. Respondents have a higher level of certainty in paying their stated WTP under a mandatory payment scheme.

A decision support system for evaluating effects of Feed-in Tariff mechanism: Dynamic modeling of Malaysia’s electricity generation mix

Malaysia has abundant potentials of renewable energy resources mainly because of its rich agriculture that makes high potential in bio-power and its tropical climate, which provides sufficient sunlight for utilization of solar systems. Feed in Tariff mechanism has been applied since 2011 in Malaysia to expand utilization of renewable energy for electricity generation. In this study, a broad range of data is gathered to develop a comprehensive system dynamics model to evaluate the impacts of Feed in Tariff mechanism on the generation mix of Malaysia during a 20-year period between 2011 and 2030. Results demonstrate that although the policy may lead to a satisfactory level of target achievement but the Malaysian government may face an increasing shortage in its RE fund budget starting around 2019 unless it increases its income sources by rising the surcharges on electricity bills or decreases its expenditures by optimizing the amount of FiT payments in different periods. The sensitivity analysis illustrates that the more funding will not lead to a more sustainable generation mix unless it is paid in the right time and in the right direction. Using this model, policymakers can carry out analysis to determine the amount of money that must be collected from the electricity consumers through the surcharges on electricity bills as well as the amount of feed in tariff to be paid for different renewable resources in different periods.

Scenario Planning of Substitution of Wind Power for Coal-Fired Power: A Case Study from the Coastal Zone of Laizhou Bay, China

Emissions of air pollutants from coal-fired power plants pose a threat to healthy living environment. Developing renewable energy and changing electricity generation structure dominated by coal-fired power has become a vital national strategy. In this paper, taking a rapidly urbanizing coastal area in southern Laizhou Bay of China as the study area, a scenario planning concerning substitution of wind power for coal-fired power in enterprise-owned power plants was conducted. Coupled with the electricity generation prediction by a grey prediction model GM (1, 1) and the calculation of pollutant emission intensity, we obtained three scenario schemes: no substitution (Scenario 1), low substitution (Scenario 2) and high substitution (Scenario 3). The results showed that Scenario 1 is not acceptable; Scenario2 is acceptable, but not ideal; Scenario 3 is optimal. The electricity generation structure under Scenario 3 has been radically converted from the type dominated by fossil fuel to one dominated by renewable energy, becoming an environment-friendly power generation framework with fairly low pollutant emission densities. This study can contribute to local managers to seek more concrete measures in mitigating the conflict between electricity demand and environmental health.

Considerations for an EU-wide use of renewable energies for electricity generation

This paper studies a joint Europe-wide use of renewable energies for electricity generation. With actual wind data of eight and photo voltaic (PV) data of four countries the benefits are assessed of an EU-wide use of renewable energies (RES) for electricity production in comparison to an independent national use. The data of 2012 are scaled to a 100% supply by RES to characterise the future final situation. Where available, wind and PV data are optimally mixed. Wind turns out to have the largest averaging effect. Nevertheless, surplus energy is produced and residual power still has to be provided. When surplus electricity is produced it is simultaneously produced by the neighbour countries. The use of an EU-wide RE field allows to reduce the back-up and the surplus energy of individual countries typically by 30%. The interconnection capacity has to be increased above the peak load in most cases to allow the distribution of surplus power. The RE power capacity to be installed for a 100% supply has been considered for 29 countries. The present RE capacity of 185GW has to be increased to 1272GW. Under these conditions the produced surplus energy corresponds to the consumption of Germany plus Poland.

Condition Monitoring Philosophy for Tidal Turbines

Renewable energy is currently considered as the main solution to reduce greenhouse gas emission. This has led to great developments in the use of renewable energy for electricity generation. Among many renewable energy resources, tidal energy has the advantage of being predictable, particularly when compared to wind energy. Currently the UK is the world leader in extracting energy from the tide; an estimation shows a potential of 67 TWh per year. In order to ensure safe operation and prolonged life for tidal turbines, condition monitoring is essential. The technology for power generation using tidal turbines is new therefore the condition monitoring concept for these devices is yet to be established. Also, there is a lack of understanding of techniques suitable for health monitoring of the turbine components and support structure given their unique operating environment. In this paper the condition monitoring of a tidal turbine is investigated. The objective is to highlight the need for condition monitoring and establish procedures to decide the condition monitoring techniques required, in addition to highlighting the impact and benefits of applying condition based maintenance. A model for failure analysis is developed to assess the needs for condition monitoring and identify critical components, after which a 'symptoms analysis' was performed to decide the appropriate condition monitoring techniques. Finally, the impact of condition monitoring on system reliability is considered.