Renewable Electricity System Research Articles

Ocean Thermal Energy Conversion—Flexible Enabling Technology for Variable Renewable Energy Integration in the Caribbean

Many Caribbean island nations have historically been heavily dependent on imported fossil fuels for both power and transportation, while at the same time being at an enhanced risk from the impacts of climate change, although their emissions represent a very tiny fraction of the global total responsible for climate change. Small island developing states (SIDSs) are among the leaders in advocating for the ambitious 1.5 °C Paris Agreement target and the transition to 100% sustainable, renewable energy systems. In this work, three central results are presented. First, through GIS mapping of all Caribbean islands, the potential for near-coastal deep-water as a resource for ocean thermal energy conversion (OTEC) is shown, and these results are coupled with an estimate of the countries for which OTEC would be most advantageous due to a lack of other dispatchable renewable power options. Secondly, hourly data have been utilized to explicitly show the trade-offs between battery storage needs and dispatchable renewable sources such as OTEC in 100% renewable electricity systems, both in technological and economic terms. Finally, the utility of near-shore, open-cycle OTEC with accompanying desalination is shown to enable a higher penetration of renewable energy and lead to lower system levelized costs than those of a conventional fossil fuel system.

The Emerging Potential of Microgrids in the Transition to 100% Renewable Energy Systems

International, national, and subnational laws and policies call for rapidly decarbonizing energy systems around the globe. This effort relies heavily on renewable electricity and calls for a transition that is: (i) flexible enough to accommodate existing and new electricity end uses and users; (ii) resilient in response to climate change and other threats to electricity infrastructure; (iii) cost-effective in comparison to alternatives; and (iv) just in the face of energy systems that are often the result of—or the cause of—procedural, distributive, and historical injustices. Acknowledging the intertwined roles of technology and policy, this work provides a cross-disciplinary review of how microgrids may contribute to renewable electricity systems that are flexible, resilient, cost-effective, and just (including illustrative examples from Korea, California, New York, the European Union, and elsewhere). Following this review of generalized microgrid characteristics, we more closely examine the role and potential of microgrids in two United States jurisdictions that have adopted 100% renewable electricity standards (Hawai‘i and Puerto Rico), and which are actively developing regulatory regimes putatively designed to enable renewable microgrids. Collectively, this review shows that although microgrids have the potential to support the transition to 100% renewable electricity in a variety of ways, the emerging policy structures require substantial further development to operationalize that potential. We conclude that unresolved fundamental policy tensions arise from justice considerations, such as how to distribute the benefits and burdens of microgrid infrastructure, rather than from technical questions about microgrid topologies and operating characteristics. Nonetheless, technical and quantitative future research will be necessary to assist regulators as they develop microgrid policies. In particular, there is a need to develop socio–techno–economic analyses of cost-effectiveness, which consider a broad range of potential benefits and costs.

Fuel cell electric vehicles and hydrogen balancing 100 percent renewable and integrated national transportation and energy systems

Abstract Future national electricity, heating, cooling and transport systems need to reach zero emissions. Significant numbers of back-up power plants as well as large-scale energy storage capacity are required to guarantee the reliability of energy supply in 100 percent renewable energy systems. Electricity can be partially converted into hydrogen, which can be transported via pipelines, stored in large quantities in underground salt caverns to overcome seasonal effects and used as electricity storage or as a clean fuel for transport. The question addressed in this paper is how parked and grid-connected hydrogen-fueled Fuel Cell Electric Vehicles might balance 100 per cent renewable electricity, heating, cooling and transport systems at the national level in Denmark, Germany, Great Britain, France and Spain? Five national electricity, heating, cooling and transport systems are modeled for the year 2050 for the five countries, assuming only 50 percent of the passenger cars to be grid-connected Fuel Cell Electric Vehicles, the remaining Battery Electric Vehicles. The grid-connected Fuel Cell Electric Vehicle fleet can always balance the energy systems and their usage is low, having load factors of 2.1–5.5 percent, corresponding to an average use of 190–480 h per car, per year. At peak times, occurring only a few hours per year, 26 to 43 percent of the grid-connected Fuel Cell Electric Vehicle are required and in particular for energy systems with high shares of solar energy, such as Spain, balancing by grid-connected Fuel Cell Electric Vehicles is mainly required during the night, which matches favorably with driving usage.

Modeling of a Marine Hydrokinetic Cycloturbine Vehicle

A marine hydrokinetic (MHK) cycloturbine is a renewable electric power generation system used in rivers or tidal environments to address the need for electricity in remote regions. MHK cycloturbines have hydrofoils oriented perpendicular to the flow in a paddlewheel configuration, and use lift generated from these foils to produce power. Due to the high cost associated with its operation and maintenance, an MHK system with four stacked counter-rotating turbines that can self-deploy and with propulsion and control mechanisms similar to a cycloturbine aircraft has been designed. A detailed turbine simulation model is necessary to understand the vehicle dynamics and assist in the design of the vehicle controllers. The simulation model solves the six degree-of-freedom rigid body equations of motion for the maneuvering MHK system subject to the hydrodynamic lift and drag forces, hydrostatic forces, and the propulsive forces from the turbines. The turbine propulsive force model is matched to computational fluid dynamics analysis and experimental data. Experimental work includes investigation at 1/5.56 scale of a single turbine rapid prototype device and a subscale demonstrator in a reverberant tank.

Understanding New Zealand’s wind resources as a route to 100% renewable electricity

The New Zealand Government has a goal of a 100% renewable electricity system by 2035. Wind generation is expected to play a major role in achieving this target. However, there is limited public data on current and potential wind generation. We use the Renewables.ninja model to simulate wind output at 44 wind farm sites in New Zealand over a 20-year period. We make our data publicly available and use them to analyse New Zealand’s wind resources.We find the long-run average capacity factors over all current and potential sites is 40%. It is lowest in autumn (around 35%) and highest in spring (around 45%). Output is similar across all demand percentiles with little correlation between wind output and demand. A small positive correlation exists between wind output and daily inflows into hydro storage dams. A more significant positive correlation exists between wind output and inflows in the period leading up to winter (when lake levels are typically lowest), implying that wind cannot help energy shortfall during dry years. Finally, we explore how much wind capacity must be installed to give a 100% renewable electricity system, and the trade-offs between energy storage and spilling wind for achieving this target.

ИСПОЛЬЗОВАНИЕ ФОТОЭЛЕКТРИЧЕСКИХ МОДУЛЕЙ С ДВУХСТОРОННЕЙ ПРИЁМНОЙ ПОВЕРХНОСТЬЮ ДЛЯ УСТАНОВОК МАЛОЙ ГЕНЕРАЦИИ

In the presented work, the possibility of using photovoltaic silicon panels with a double-sided arrangement of solar cells on the front and back sides is presented. With a lack of space for placing solar panels, these types of modules can significantly increase the generation of electrical energy. Equipping photovoltaic systems with rechargeable batteries contributes to a more rational consumption of electrical energy, while energy storage systems significantly increase the efficiency of solar generating systems. The proposed designs are intended to increase the power characteristics of solar energy converters in the winter months, in the presence of snow or when using reflective surfaces on road surfaces. The results of the experimental studies have shown a significant efficiency of the proposed designs, as well as an increase in the total generation of electrical energy. With the development of the global technical potential and a significant increase in the production of power plants for solar energy, a new opportunity has emerged to use combined solar plants for photovoltaic conversion of the flux of incident solar radiation. At the Department of Renewable Energy Sources and Electrical Systems and Networks at Sevastopol State University, at the site of the Institute of Nuclear Energy and Industry, a photovoltaic installation was developed and studied, consisting of two side silicon solar cells and energy storage systems. The article presents the results of experimental and theoretical studies, presents diagrams, drawings and graphs of various characteristics of the FSM-110D photovoltaic panel and storage batteries. The research results show the increased efficiency of the proposed installation, as well as a good possibility of using the presented photovoltaic systems to provide them with autonomous and individual consumers living in the Crimean region and the city of Sevastopol.

Potentials of Hydrogen Technologies for Sustainable Factory Systems

The industrial sector is the world’s second largest emitter of greenhouse gases, hence a methodology for decarbonizing factory systems is crucial for achieving global climate goals. Hydrogen is an important medium for the transition towards carbon neutral factories due to its broad applicability within the factory, including its use in electricity and heat generation and as a process gas or fuel. One of the main challenges is the identification of economically and environmentally suitable design scenarios, such as for the entire value chain for hydrogen generation and application. For example, the infrastructure for renewable electricity, hydrogen generation, hydrogen conversion (e.g. into synthetic fuels), storage and transport systems as well as application in the factory. Due to the high volatility of energy generation and the related dynamic interdependencies within a factory system, a valid technical, economic and environmental evaluation of benefits induced by hydrogen technologies can only be achieved using digital factory models. In this paper, we present a framework to integrate hydrogen technologies into factory systems. This enables decision makers to identify promising measures according to their expected impact and collect data for appropriate factory modelling. Furthermore, a concept for factory modelling and simulation is presented and demonstrated in a case study from the electronics industry, assessing the use of hydrogen for decentralized power and heat generation.

Comparative Life Cycle Environmental Impact and Price Analyses of Renewable Electricity Systems for Net Zero Greenhouse Gas Emissions between Global Economies

Comparative Life Cycle Environmental Impact and Price Analyses of Renewable Electricity Systems for Net Zero Greenhouse Gas Emissions between Global Economies

MENA compared to Europe: The influence of land use, nuclear power, and transmission expansion on renewable electricity system costs

Most studies that examine CO2-neutral, or near CO2-neutral, power systems by using energy system models investigate Europe or the United States, while similar studies for other regions are rare. In this paper, we focus on the Middle East and North Africa (MENA), where weather conditions, especially for solar, differ substantially from those in Europe. We use a green-field linear capacity expansion model with over-night investment to assess the effect on the system cost of (i) limiting/expanding the amount of land available for wind and solar farms, (ii) allowing for nuclear power and (iii) disallowing for international transmission. The assessment is done under three different cost regimes for solar PV and battery storage.First, we find that the amount of available land for wind and solar farms can have a significant impact on the system cost, with a cost increase of 0–50% as a result of reduced available land. In MENA, the impact on system cost from land availability is contingent on the PV and battery cost regime, while in Europe it is not. Second, allowing for nuclear power has a minor effect in MENA, while it may decrease the system cost in Europe by up to 20%. In Europe, the effect on system cost from allowing for nuclear power is highly dependent on the PV and battery cost regime. Third, disallowing for international transmission increases the system cost by up to 25% in both Europe and MENA, and the cost increase depends on the cost regime for PV and batteries.The impacts on system cost from these three controversial and policy-relevant factors in a decarbonized power system thus play out differently, depending on (i) the region and (ii) uncertain future investment costs for solar PV and storage. We conclude that a renewable power system in MENA is likely to be less costly than one in Europe, irrespective of future uncertainties regarding investment cost for PV and batteries, and policies surrounding nuclear power, transmission, and land available for wind- and solar farms. In MENA, the system cost varies between 42 and 96 $/MWh. In Europe, the system cost varies between 51 and 102 $/MWh.

The Value of Inter-Regional Coordination and Transmission in Decarbonizing the US Electricity System

Summary Preventing global warming in excess of 1.5°C–2°C requires a transition to zero-carbon electricity systems by midcentury along with the widespread electrification of other sectors. Current state-level renewable portfolio standards and regional transmission arrangements do not capture the benefits of inter-regional transmission or coordination of planning and dispatch for renewable-energy integration. Here, using a co-optimized capacity-planning and dispatch model over 7 years of hourly operation, we show that inter-state coordination and transmission expansion reduce the system cost of electricity in a 100%-renewable US power system by 46% compared with a state-by-state approach, from 135 $/MWh to 73 $/MWh. Sensitivity analyses show that reductions in the cost of photovoltaics, wind, and lithium-ion batteries lead to the lowest electricity costs for systems in which transmission expansion is allowed, while cost reductions for nuclear power or long-duration energy storage lead to greater electricity cost reductions for isolated systems.

Stronger together: Multi-annual variability of hydrogen production supported by wind power in Sweden

Hydrogen produced from renewable electricity will play an important role in deep decarbonisation of industry. However, adding large electrolyser capacities to a low-carbon electricity system also increases the need for additional electricity generation from variable renewable energies. This will require hydrogen production to be variable unless other sources provide sufficient flexibility. Existing sources of flexibility in hydro-thermal systems are hydropower and thermal generation, which are both associated with sustainability concerns. In this work, we use a dispatch model for the case of Sweden to assess the power system operation with large-scale electrolysers, assuming that additional wind power generation matches the electricity demand of hydrogen production on average. We evaluate different scenarios for restricting the flexibility of hydropower and thermal generation and include 29 different weather years to test the impact of variable weather regimes. We show that (a) in all scenarios electrolyser utilisation is above 60% on average, (b) the inter-annual variability of hydrogen production is substantial if thermal power is not dispatched for electrolysis, and (c) this problem is aggravated if hydropower flexibility is also restricted. Therefore, either long-term storage of hydrogen or backup hydrogen sources may be necessary to guarantee continuous hydrogen flows. Large-scale dispatch of electrolysis capacity supported by wind power makes the system more stable, if electrolysers ramp down in rare hours of extreme events with low renewable generation. The need for additional backup capacities in a fully renewable electricity system will thus be reduced if wind power and electrolyser operation are combined in the system.

Off-grid and decentralized hybrid renewable electricity systems data analysis platform (OSDAP): A building block of a comprehensive techno-economic approach based on contrastive case studies in Sub-Saharan Africa and Canada

Off-grid and decentralized Hybrid Renewable Electricity Systems (OHRES) play a promising role in providing sustainable energy access to 860 million people around the globe with no access to electricity. However, the diversity of global geographies, lack of performance analysis standardization, and modeling limitations hinder the scalability of OHRES. This study outlines the creation of a data analysis platform (OSDAP) and irradiance forecasting models for OHRES that can be used to support the provision of global energy access. The paper presents the technical layout of OHRES in two case studies in Canada and Uganda and outlines an assessment and modeling platform that can be used to assess OHRES performance across widely varying geographic locations. Two irradiance forecasting models are developed using artificial neural networks, which can be used to increase solar energy utilization in OHRES.

Desalination and sustainability: a triple bottom line study of Australia

For many arid countries, desalination is considered as the final possible option to ensure water availability. Although seawater desalination offers the utilisation of almost infinite water resources, the technology is associated with high costs, high energy consumption and thus high carbon emissions when using electricity from fossil sources. In our study, we compare different electricity mixes for seawater desalination in terms of some economic, social and environmental attributes. For this purpose, we developed a comprehensive multi-regional input-output model that we apply in a hybrid life-cycle assessment spanning a period of 29 yr. In our case study, we model desalination plants destined to close the water gap in the Murray-Darling basin, Australia’s major agricultural area. We find that under a 100%-renewable electricity system, desalination consumes 20% less water, emits 90% less greenhouse gases, and generates 14% more employment. However, the positive impacts go hand in hand with 17% higher land use, and a 10% decrease in gross value added, excluding external effects.

Sustainability assessment of a hybrid CSP/biomass. Results of a prototype plant in Tunisia

A renewable electricity system hybrid concentrated solar power/biomass power plantin Tunisia has been assessed. Life Cycle Assessment (LCA) and the Input-Output Analysis (IOA) methodologies have been performed to assess the environmental and socio-economic impacts of this technology in the Tunisian context. Application of these methodologies allowed computing environmental footprint, and the total economic stimulation produced by the increase in the demand for goods and services needed to build and operate this kind of plant. Results show for system operates in closed digester conditions value of 18.5 gCO2eq per kWh. In an open digester system, levels of GHG emissions are similar to fossil electricity generation with 550 gCO2eq per Kwh. For socioeconomic impacts, the multiplier effect of the direct investment for production of goods and services amounts is 2.43. Domestic value added created was quantified in a 42% (0.15 €2015/kWh) and employment creation in 532.9 FTE (0.006 FTE/MWh). Finally, the calculated abatement costs are low, 86 US$/tCO2eq. From the obtained results, it can be concluded that investments in this technology are then a cost-effective way of mitigating global warming emissions while also producing additional benefits in terms of value-added creation in the country and domestic employment generation.

Dynamic modeling and energy analysis of renewable heating and electricity systems at residential buildings using phase change material based heat storage technologies

Several heat storage systems for domestic application can be used to promote Renewable Energy Sources (RES) penetration by storing excess energy, which would otherwise be rejected during curtailments. The present study investigates two types of PV powered latent heat storage technologies for delivering heat and/or electricity at residential buildings and compares them against a reference case which uses a conventional heat pump as a heating system, also powered by a PV. One technology involves a low temperature PCM thermal energy storage system (LT-TES) heated by either an electric resistance or a heat pump and the other technology involves an ultra-high temperature TES (UHT-TES). It is revealed that any case with heat storage is preferable for better exploiting the produced renewable energy than the conventional one which does not include heat storage. The most favorable from this aspect are the cases which include the UHT-TES, which provide both heat and electricity. Focusing exclusively on heat supply, the most preferable case from a technical performance aspect is the one which includes a heat pump and a LT-TES system, albeit not providing any electricity. On the other hand, the most advantageous only in terms of electricity supply is the case which includes the UHT-TES system.

Electricity system resilience in a world of increased climate change and cybersecurity risk

The shift to widely distributed forms of energy generation and storage, requiring increased interconnectivity to geographically balance supply with distributed demand for electricity, creates a more complex electrical network – the ‘Internet of Energy’. A growing array of threats now impact the resilience of the electrical network including digitalisation, cybersecurity, technological changes of the power system, and the potential for climate change to expose the system to more extreme weather events. Whether distributed and renewable electricity systems will be more resilient through multiple pathways and redundancy, or less resilient due to greater cybersecurity risks than a conventional centralised electricity system, is the key focus of this paper.

The near-optimal feasible space of a renewable power system model

Models for long-term investment planning of the power system typically return a single optimal solution per set of cost assumptions. However, typically there are many near-optimal alternatives that stand out due to other attractive properties like social acceptance. Understanding features that persist across many cost-efficient alternatives enhances policy advice and acknowledges structural model uncertainties. We apply the modeling-to-generate-alternatives (MGA) methodology to systematically explore the near-optimal feasible space of a completely renewable European electricity system model. While accounting for complex spatio-temporal patterns, we allow simultaneous capacity expansion of generation, storage and transmission infrastructure subject to linearized multi-period optimal power flow. Many similarly costly, but technologically diverse solutions exist. Already a cost deviation of 0.5% offers a large range of possible investments. However, either offshore or onshore wind energy along with some hydrogen storage and transmission network reinforcement appear essential to keep costs within 10% of the optimum.

Electric Vehicles and Biofuels Synergies in the Brazilian Energy System

Shaping a secure and sustainable energy future may require a set of transformations in the global energy sector. Although several studies have recognized the importance of Electric Vehicles (EVs) for power systems, no large-scale studies have been performed to assess the impact of this technology in energy systems combining a diverse set of renewable energies for electricity production and biofuels in the transportation sector such as the case of Brazil. This research makes several noteworthy contributions to the current literature, including not only the evaluation of the main impacts of EVs’ penetration in a renewable electricity system but also a Life-Cycle Assessment (LCA) that estimates the overall level of CO2 emissions resulted from the EVs integration. Findings of this study indicated a clear positive effect of increasing the share of EVs on reducing the overall level of CO2 emissions. This is, however, highly dependent on the share of Renewable Energy Sources (RES) in the power system and the use of biofuels in the transport sector but also on the credits resulting from the battery recycling materials credit and battery reuse credit. Our conclusions underline the importance of such studies in providing support for the governmental discussions regarding potential synergies in the use of bioresources between transport and electricity sectors.

Role of Long-Duration Energy Storage in Variable Renewable Electricity Systems

Summary Reliable and affordable electricity systems based on variable energy sources, such as wind and solar may depend on the ability to store large quantities of low-cost energy over long timescales. Here, we use 39 years of hourly U.S. weather data, and a macro-scale energy model to evaluate capacities and dispatch in least cost, 100% reliable electricity systems with wind and solar generation supported by long-duration storage (LDS; 10 h or greater) and battery storage. We find that the introduction of LDS lowers total system costs relative to wind-solar-battery systems, and that system costs are twice as sensitive to reductions in LDS costs as to reductions in battery costs. In least-cost systems, batteries are used primarily for intra-day storage and LDS is used primarily for inter-season and multi-year storage. Moreover, dependence on LDS increases when the system is optimized over more years. LDS technologies could improve the affordability of renewable electricity.

Optimal mix of climate-related energy in global electricity systems

Abstract Existing studies on high renewable share electricity systems are usually based on least cost optimization. Running the related models can be time-consuming when space-time resolution is high. This study investigates the optimal mix of climate-related energies for most countries in the world with optimization models based on three criteria: cost, residual load variability, and portfolio output variability. The objectives of minimizing residual load variability and portfolio output variability are to ensure the overall complementarity of the generation portfolio, which may result in less conventional dispatchable units needed in a system. Compromise solutions based on the three objectives are proposed as the optimal mix. This method can produce solutions in acceptable modelling time, and considers the portfolio output characteristics which can make higher climate-related energy penetration more practical. The results show that the compromise solutions can effectively minimize the three objective values in most countries. The results also suggest that wind power is crucial in higher renewable share systems while solar power does not reach over 50% capacity share.