Renewable Electricity System Research Articles

Radical transformation pathway towards sustainable electricity via evolutionary steps

A transition towards long-term sustainability in global energy systems based on renewable energy resources can mitigate several growing threats to human society simultaneously: greenhouse gas emissions, human-induced climate deviations, and the exceeding of critical planetary boundaries. However, the optimal structure of future systems and potential transition pathways are still open questions. This research describes a global, 100% renewable electricity system, which can be achieved by 2050, and the steps required to enable a realistic transition that prevents societal disruption. Modelling results show that a carbon neutral electricity system can be built in all regions of the world in an economically feasible manner. This radical transformation will require steady but evolutionary changes for the next 35 years, and will lead to sustainable and affordable power supply globally.

21st Century Climate Change Impacts on Key Properties of a Large-Scale Renewable-Based Electricity System

Efforts to reduce climate change, but also falling prices and significant technology developments currently drive an increased weather-dependent electricity production from renewable electricity sources. In light of the changing climate, it is highly relevant to investigate the extent of weather changes that directly impacts the best system design decisions for these weather-dependent technologies. Here, we use three IPCC representative CO2 concentrations pathways for the period 2006--2100 with six high-resolution climate experiments for the European domain. Climate elements are used to calculate bias adjusted 3-hourly time series of wind and solar generation, and temperature corrected demand time series for 30 European countries using state-of-the-art methodology. Weather-driven electricity system analysis methodology is then applied to compare four key metrics of highly renewable electricity systems. We find that climate change does not have a discernible impact on the key metrics of the combined electricity system dynamics, and conclude that the effect on important system design parameters can likely be ignored.

ASEAN grid flexibility: Preparedness for grid integration of renewable energy

In 2015, ASEAN established a goal of increasing its renewable energy share in its energy portfolio from approximately 13–23% by 2025. Renewable electricity, especially intermittent and variable sources, presents challenges for grid operators due to the uncertain timing and quantity of electricity supply. Grid flexibility, the electric grid's ability to respond to changing demands and supply, now stands a key resource in responding to these uncertainties while maximizing the cost-effective role of clean energy. We develop and apply a grid flexibility assessment tool to assess ASEAN's current grid flexibility using six quantitative indicators: grid reliability, electricity market access; load profile ramp capacity; quality of forecasting tools; proportion of electricity generation from natural gas; and renewable energy diversity. We find that ASEAN nations cluster into three groups: better; moderately; and the least prepared nations. We develop an analytical ramp rate calculator to quantify expected load ramps for ASEAN in an integrated ASEAN Power Grid scenario. The lack of forecasting systems and limited electricity market access represent key weaknesses and areas where dramatic improvements can become cost-effective means to increase regional grid flexibility. As ASEAN pursues renewable energy targets, regional cooperation remains essential to address identified challenges. Member nations need to increase grid flexibility capacity to adequately prepare for higher penetrations of renewable electricity and lower overall system costs.

Impact of Climate Change on the Backup Infrastructure of Highly Renewable Electricity Systems

Impact of Climate Change on the Backup Infrastructure of Highly Renewable Electricity Systems

Optimum integration of concentrating solar technologies in a real coal-fired power plant for fuel saving

The integration of Concentrating Solar Power (CSP) technology in large scale fossil-fuelled power plant is one of the best options to promote the necessary transition to a totally renewable electric system starting from the present system. This work provides a complete overview of the possible integration of CSP systems into a real 320 MW coal-fired steam power plant aimed at fuel saving. To this end, detailed off-design models of the existing steam power plant are first built and validated using experimental data measured on the field. Design and off-design models of solar section are then added considering several placement points. Unlike most of the literature, all technical constraints associated with maximum and minimum load of the existing components are also taken into account. The most efficient integration points proposed in the literature plus four new ones are considered in combination with parabolic trough collectors, linear Fresnel collectors or solar towers, for a total of twenty-two different design options. The best integration point results to be in the high-pressure preheater/s: (i) the highest hybrid thermal efficiency (42.67%) is obtained using parabolic trough/molten salt collectors to generate additional high-pressure steam from the drainage water of the last two parallel preheaters (HPH3), (ii) similar thermal efficiencies are achieved in a wide range of solar share (up to 9.1%) by including parabolic through/thermal oil collectors to heat part of the feedwater stream of HPH3 and (iii) 15,400 tons per year of coal can be saved when the solar field area is approximately four times as much the area of the existing coal storage area.

Principal flow patterns across renewable electricity networks

Using Principal Component Analysis (PCA), the nodal injection and line flow patterns in a network model of a future highly renewable European electricity system are investigated. It is shown that the number of principal components needed to describe 95% of the nodal power injection variance first increases with the spatial resolution of the system representation. The number of relevant components then saturates at around 76 components for network sizes larger than 512 nodes, which can be related to the correlation length of wind patterns over Europe. Remarkably, the application of PCA to the transmission line power flow statistics shows that irrespectively of the spatial scale of the system representation a very low number of only 8 principal flow patterns is sufficient to capture 95% of the corresponding spatio-temporal variance. This result can be theoretically explained by a particular alignment of some principal injection patterns with topological patterns inherent to the network structure of the European transmission system.

Model based approach for planning dynamic integration of renewable energy in a transitioning electricity system

Reality of climate change threats have spurred mitigation interventions across the world. For electricity sector, the interventions are predominantly in terms of mainstreaming renewable energy sources. Consequently, there is a consistent increase in the share of renewable energy-based electricity systems which has caused emergence of several new challenges. The challenges have emerged both with respect to planning and management of the transitioning electricity systems. These new challenges are because of shift away from supply-chain influenced conventional energy resource supply to nature influenced dynamic renewable energy resource supply; shift from conventional firm power to renewable intermittent power; operational complexities due to frequent and steeper ramps; and need for matching dynamic demand for power. We propose, develop and validate a novel approach for better representation of these resource-supply-demand dynamics in evolving suite of generation expansion models with operational details. First, we discuss development of an electricity generation expansion planning model with operational details. Second, to model the dynamic nature of renewable energy resources and demand for power, we develop an approach for generating annual wind and solar resource profiles, and representative load curves respectively, and harmonizing them before they are fed into the generation expansion model. We validate this approach using India’s electricity system data and use the model to evaluate implications of varying levels of renewable energy integration. We find that this increased penetration of renewable energy while bringing significant climate change benefits creates substantial capacity redundancy leading to lower capacity utilization of the overall system.

A new approach for assessing synergies of solar and wind power: implications for West Africa

West African countries’ energy and climate policies show a pronounced focus on decarbonising power supply through renewable electricity (RE) generation. In particular, most West African states explicitly focus on hybrid mixes of variable renewable power sources—solar, wind and hydropower—in their targets for the electricity sector. Hydropower, the main current RE resource in West Africa, is strongly sensitive to monsoon rainfall variability, which has led to power crises in the past. Therefore, solar and wind power could play a stronger role in the future as countries move to power systems with high shares of RE. Considering the policy focus on diversified RE portfolios, there is a strong need to provide climate services for assessing how these resources could function together in a power mix. In this study, climate data from the state-of-the-art ERA5 reanalysis is used to assess the synergies of solar photovoltaic (PV) and wind power potential in West Africa at hourly resolution. A new metric, the stability coefficient Cstab, is developed to quantify the synergies of solar PV and wind power for achieving a balanced power output and limiting storage needs. Using this metric, it is demonstrated that there is potential for exploiting hybrid solar/wind power in a larger area of West Africa, covering more important centers of population and closer to existing grid structures, than would be suggested by average maps of solar and wind resource availability or capacity factor for the region. The results of this study highlight why multi-scale temporal synergies of power mixes should be considered in RE system planning from the start.

Comparison of different operation strategies for PV battery home storage systems including forecast-based operation strategies

Photovoltaic battery energy storage systems can increase the self-consumption from residential PV systems and therefore contribute to a decentralized renewable electricity system. Rising electricity prices and decreasing battery prices enhance the economics of residential battery storage. Intelligent operation strategies could further improve the economics and lead to grid relief as well.This paper presents new forecast-based operation strategies for increased battery lifetime and reduced curtailment of PV power feed-into enhance system economics. In addition, these strategies are compared to different commonly used operation strategies in terms of economics and self-sufficiency of the system. Increased battery lifetime is achieved by reducing the average state of charge of the battery by limiting the stored energy according to the predicted energy demand during night. Forecast-based operation strategies are used in combination with variable power feed-in limits of the PV battery storage system to relieve the grid. Two different forecast strategies are discussed: the perfect forecast, which is used as the best case, and the persistence forecast, representing the worst case in terms of forecast accuracy.The operation strategies are evaluated by simulating a DC-coupled PV and battery system. The model is parameterized with measured data from cell testing and battery aging tests. The levelized cost of electricity is used for the economic evaluation of the operation strategies.Results show that the developed forecast-based operation strategy can drastically increase battery lifetime and thus total energy throughput and therefore reduce the levelized cost of electricity by up to 12%. This has been shown effectively for two different types of battery cell, a low-cost consumer cell and a high-quality battery cell. The combination of forecast-based operation strategies with variable feed-in limits can nearly eliminate curtailed PV energy for the simulated system. Sensitivity analyses of component sizing and load profile confirm the findings. The developed strategy can easily be implemented on real residential PV battery energy storage systems since no additional communication interface is required.

Cost optimal scenarios of a future highly renewable European electricity system: Exploring the influence of weather data, cost parameters and policy constraints

Cost optimal scenarios derived from models of a highly renewable electricity system depend on the specific input data, cost assumptions and system constraints. Here this influence is studied using a techno-economic optimisation model for a networked system of 30 European countries, taking into account the capacity investment and operation of wind, solar, hydroelectricity, natural gas power generation, transmission, and different storage options. A considerable robustness of total system costs to the input weather data and to moderate changes in the cost assumptions is observed. Flat directions in the optimisation landscape around cost-optimal configurations often allow system planners to choose between different technology options without a significant increase in total costs, for instance by replacing onshore with offshore wind power capacity in case of public acceptance issues. Exploring a range of carbon dioxide emission limits shows that for scenarios with moderate transmission expansion, a reduction of around 57% compared to 1990 levels is already cost optimal. For stricter carbon dioxide limits, power generated from gas turbines is at first replaced by generation from increasing renewable capacities. Non-hydro storage capacities are only built for low-emission scenarios, in order to provide the necessary flexibility to meet peaks in the residual load.

(Invited) Hydrogen Fuel Cell Systems in Nordic Regions

The Nordic Hydrogen Corridor (NHC) project was launched in 2016 to introduce new Hydrogen Refueling Stations (HRS), hydrogen production units (electrolysers) and Fuel Cell Electric Vehicles (FCEV) along the Trans-European Transport (TENT-T) Network in Sweden in the period 2017-2020. This HRS network will enable zero emission transport facilities between the capital of the Nordic countries from Norway through Sweden to Denmark and Finland and further via Germany to the rest of the Europe [1]. In the case of Norway, the country’s strategy is structured around five closely interrelated themes addressing: (i) energy supply security, (ii) a fully-integrated energy market, (iii) energy efficiency, (iv) decarbonising the economy and (v) research, innovation and competitiveness. Climate change is one of the policy priorities of Norway. The country is a heavy producer of renewable energy and electricity generation, with hydropower being the source of most of the production [2]. For example, in 2013 Norway produced circa 134 TWh of electricity from which 96%, 1.5% and 2.5% was generated from hydropower, wind power and thermal power, respectively [2]. There is also a large potential in wind power, offshore wind power and wave power, as well as the production of bio-energy from biomass. Although, Norway has limited resources in solar energy, it is one of the world's largest producers of solar grade silicon and silicon solar cells. Hydrogen Energy has been identified by Norway as an alternative fuel with the potential for a substantial contribution to reduce petroleum dependence and greenhouse gases emissions in the long term. The Norwegian government supports the potential role of hydrogen for Norway in the transition to a zero-emission society [3,4]. In line with the EU, Hydrogen and Fuel Cell Technologies (HFCTs) have been identified as a key area of research priority for Norway [3-5]. For example, the White Paper on Norway’s energy policy [4] explicitly describes the national hydrogen priorities, which focus on research and development within production, storage and use of hydrogen. Indeed, among the renewable energy sources, HFCTs are considered as a key technology of the 21st century, not only because of its high efficiency in heat and electricity generation, but also because of its potential role in attaining sustainable energy system. It is also envisaged that HFCT will be integrated into “intelligent” energy networks, with conventional and distributed renewable electricity systems. Also, they enable flexible and adaptable fueling strategies, according to local resources, with fossil, bio-fuels or synthetic fuels to reduce impact on air pollution and climate change. For a few years, Norway has put significant effort in HFCT R&D through national and international projects as well as in implementing a hydrogen infrastructure. This presentation highlights the main HFCT projects in Norway along with the other Nordic countries.

A hybrid energy system based on renewable energy for the electrification of low-income rural communities

Electrification of low-income rural areas that have a limited connection or no access to electrical grids is one of the most demanding challenges in developing countries such as Peru. The international commitment to stop global warming and the reduction in the cost of renewable sources of energy have reduced the prices of fossil fuels in some cases. This has opened the way to the current research which proposes a hybrid energy system (HES) based on the use of renewable sources of energy. Therefore, a renewable electricity system (HRES) was set up at the village of Monte-Catache in the Cajamarca region, which is one of the poorest areas of Peru. Surveys and field studies were used to evaluate the socioeconomic characteristics, availability of renewable energy resources, and energy demand of this region. Potential energy sources were evaluated, and isolated photovoltaic systems with a battery bank were found to be the most appropriate according to the results obtained in the simulation with HOMER. This proposal constitutes an interesting contribution for future energy solutions in isolated and low-income rural areas.

Resource portfolio design considerations for materially-efficient planning of 100% renewable electricity systems

Different configurations of a 100% renewable electricity system are possible, but not all are equally desirable in terms of the scale of material resources required to sustain them. This study compares different approaches for developing a 100% renewable electricity system on the basis of the material mass investment required to sustain their physical components. Electric grid modeling accounting for operational constraints is used to determine the scale of energy technology capacities required to achieve a 100% renewable electricity system using California as a representative example and translating those requirements to material mass requirements. Using a wind/solar/storage approach requires exponentially growing capacities of energy storage to meet operational needs and requires significant material mass investments. Material resource efficiency of the system is shown to be improved by maximizing the use of regional non-variable renewables to the extent possible within local capacity constraints. Alternatively, overbuilding the wind and solar capacity in excess of that needed to meet annual demand is also shown to improve material resource efficiency of the system. Overall, different approaches for meeting a 100% renewable electricity penetration are not equally desirable when material resource usage is considered. This should be taken into account in future energy system planning studies.

Response to ‘Burden of proof: A comprehensive review of the feasibility of 100% renewable-electricity systems’

A recent article ‘Burden of proof: A comprehensive review of the feasibility of 100% renewable-electricity systems’ claims that many studies of 100% renewable electricity systems do not demonstrate sufficient technical feasibility, according to the criteria of the article's authors (henceforth ‘the authors’). Here we analyse the authors’ methodology and find it problematic. The feasibility criteria chosen by the authors are important, but are also easily addressed at low economic cost, while not affecting the main conclusions of the reviewed studies and certainly not affecting their technical feasibility. A more thorough review reveals that all of the issues have already been addressed in the engineering and modelling literature. Nuclear power, which the authors have evaluated positively elsewhere, faces other, genuine feasibility problems, such as the finiteness of uranium resources and a reliance on unproven technologies in the medium- to long-term. Energy systems based on renewables, on the other hand, are not only feasible, but already economically viable and decreasing in cost every year.

Flow-based nodal cost allocation in a heterogeneous highly renewable European electricity network

For a cost efficient design of a future renewable European electricity system, the placement of renewable generation capacity will seek to exploit locations with good resource quality, that is for instance onshore wind in countries bordering the North Sea and solar PV in South European countries. Regions with less favorable renewable generation conditions benefit from this remote capacity by importing the respective electricity as power flows through the transmission grid. The resulting intricate pattern of imports and exports represents a challenge for the analysis of system costs on the level of individual countries. Using a tracing technique, we introduce flow-based nodal levelized costs of electricity (LCOE) which allow to incorporate capital and operational costs associated with the usage of generation capacity located outside the respective country under consideration. This concept and a complementary allocation of transmission infrastructure costs is applied to a simplified model of an interconnected highly renewable European electricity system. We observe that cooperation between the European countries in a heterogeneous system layout does not only reduce the system-wide LCOE, but also the flow-based nodal LCOEs for every country individually.

Smart Net Energy Metering System

With the proliferation of distributed generation technologies and renewable energy electric power system isbecoming more complex. In traditional grid system and current energy metering infrastructure line losses are growingday by day. This project will enable smart net energy metering by using GSM technology, user will not only able to viewreal time usage of energy but also will be able to sell excessive energy to utility which is produced in the vicinity of user.Either Renewable or nonrenewable energy resources can be utilized and controlled remotely through mobileapplication, the energy sold out to utility will be deducted from energy consumed from utility which enables dual waysmart net energy metering system. Net metering makes residential solar energy system ownership even more attractiveand affordable for many families. It can save homeowners hundreds more rupees per year on their utility bills, and itmakes the process of accounting for the energy flowing to and from the utility simpler and easier to administer.

More homogeneous wind conditions under strong climate change decrease the potential for inter-state balancing of electricity in Europe

Abstract. Limiting anthropogenic climate change requires the fast decarbonization of the electricity system. Renewable electricity generation is determined by the weather and is hence subject to climate change. We simulate the operation of a coarse-scale fully renewable European electricity system based on downscaled high-resolution climate data from EURO-CORDEX. Following a high-emission pathway (RCP8.5), we find a robust but modest increase (up to 7 %) of backup energy in Europe through the end of the 21st century. The absolute increase in the backup energy is almost independent of potential grid expansion, leading to the paradoxical effect that relative impacts of climate change increase in a highly interconnected European system. The increase is rooted in more homogeneous wind conditions over Europe resulting in intensified simultaneous generation shortfalls. Individual country contributions to European generation shortfall increase by up to 9 TWh yr−1, reflecting an increase of up to 4 %. Our results are strengthened by comparison with a large CMIP5 ensemble using an approach based on circulation weather types.

RE-Europe, a large-scale dataset for modeling a highly renewable European electricity system

Future highly renewable energy systems will couple to complex weather and climate dynamics. This coupling is generally not captured in detail by the open models developed in the power and energy system communities, where such open models exist. To enable modeling such a future energy system, we describe a dedicated large-scale dataset for a renewable electric power system. The dataset combines a transmission network model, as well as information for generation and demand. Generation includes conventional generators with their technical and economic characteristics, as well as weather-driven forecasts and corresponding realizations for renewable energy generation for a period of 3 years. These may be scaled according to the envisioned degrees of renewable penetration in a future European energy system. The spatial coverage, completeness and resolution of this dataset, open the door to the evaluation, scaling analysis and replicability check of a wealth of proposals in, e.g., market design, network actor coordination and forecasting of renewable power generation.

Initial perspective on a 100% renewable electricity supply for Prince Edward Island

Prince Edward Island, already with the highest wind energy penetration of any province in Canada, aims to increase its renewable energy generation. A challenge is realizing better matching of intermittent wind and solar power with on-island electricity demand. This paper provides an initial perspective by considering the case of a 100% renewable island electricity system. Using time-series power data of wind, solar, and electricity demand for the province, varying capacities of wind and solar power along with battery energy storage and biomass are considered to model 100% renewable electrical energy scenarios. Wind, solar, and storage combinations without curtailment show how complementary supply combinations can reduce seasonal variations. Scenarios including curtailment demonstrate significantly reduced storage requirements. Scenarios that include biomass suggest little benefit in combining biomass and storage. Least-cost solar, wind, and storage capacities are estimated. Potential storage cost reductions appear to be transformative in enabling greater renewable energy integration.

Flow tracing as a tool set for the analysis of networked large-scale renewable electricity systems

The method of flow tracing follows the power flow from net-generating sources through the network to the net-consuming sinks, which allows to assign the usage of the underlying transmission infrastructure to the system participants. This article presents a reformulation that is applicable to arbitrary compositions of inflow appearing naturally in models of large-scale electricity systems with a high share of renewable power generation. We propose an application which allows to associate power flows on the grid to specific regions or generation technologies, and emphasizes the capability of this technique to disentangle the spatio-temporal patterns of physical imports and exports occurring in such systems. The analytical potential of this method is showcased for a scenario based on the IEEE 118 bus network.