Dispatchable Renewable Energy Research Articles

Power supply characterization of baseload and flexible enhanced geothermal systems

We investigated the techno-economic feasibility and power supply potential of enhanced geothermal systems (EGS) across the contiguous United States using a new subsurface temperature model and detailed simulations of EGS project life cycle. Under business-as-usual scenarios and across depths of 1–7 kilometers, we estimated 82,945 GW and 0.65 GW of EGS supply capacity with lower levelized cost of electricity than conventional hydrothermal and solar photovoltaic projects, respectively. Considering the scenario of flexible geothermal dispatch via wellhead throttling and power plant bypass, these estimates climbed up to 184,112 GW and 44.66 GW, respectively. The majority of EGS supply potential was found in the Western and Southwestern regions of the United States, where California, Oregon, Nevada, Montana, and Texas had the greatest EGS capacity potential. With advanced drilling rates based on state-of-the-art implementations of recent EGS projects, we estimated an average improvement of 25.1% in the levelized cost of electricity. These findings underscored the pivotal role of flexible operations in enhancing the competitiveness and scalability of EGS as a dispatchable renewable energy source.

Merit-order of dispatchable and variable renewable energy sources in Turkey's day-ahead electricity market

This study employs linear and non-linear quantile regression models to assess the merit-order effect (MOE) of integrating renewable energy sources (RESs) into the Turkish day-ahead electricity market. The analysis spans nine different quantiles from January 2019 to December 2022. Our results show that both dispatchable and variable renewable energy sources (VREs) are essential for reducing market clearing prices (MCPs) in the Turkish day-ahead market. However, they have different impacts on quantiles of MCPs and price variability. VREs enhances the price variability across all hours in linear and non-linear models, while dispatchable renewable energy reduces price variability except at night.

Design of a Solar Dish Receiver and Life Cycle Assessment of a Hot Water System

The energy sector is the main source of greenhouse gases, so it has the highest potential for improvement. The improvements can be achieved by generating energy from renewable sources. It is necessary to combine production from renewable sources with storage systems. Thermal energy storage using concentrated solar power systems is a promising technology for dispatchable renewable energy that can guarantee a stable energy supply even in remote areas without contributing to greenhouse gas emissions during operation. However, it must be emphasised that greenhouse gases and other impacts can occur during the production process of concentrating solar system components. This paper analyses the receiver design to produce thermal energy for the existing CSP dish plant at the Energy Center of the Politecnico di Torino. The plant is designed to produce electrical energy in the spring and summer periods. In addition to this energy production, the CSP can be adopted to produce thermal energy, through hot water, during the less favourable periods of the year in terms of global solar radiation. The surface heat flux is calculated in the first part of the analysis to obtain the maximum internal temperature in the receiver, which is 873.7 °C. This value is a constraint for the choice of material for the solar receiver. A life cycle assessment is performed to compare the emissions generated during the production of the main components of the CSP system with the emissions generated by the methane-fuelled water heater to produce the same amount of thermal energy. It can be concluded that the production of the main components of the CSP system results in lower greenhouse gas emissions than the operational phase of a conventional system. Given the assumptions made, the utilization of methane leads to the emission of approximately 12,240 kg of CO2, whereas the production of the CSP system results in emissions totalling 5332.8 kg of CO2 equivalent

Geothermal energy exploitation in an island-based 100% renewables strategy. Case study of Tenerife (Spain)

The large-scale integration of non-dispatchable renewable energy must be carefully planned, especially in poorly robust electrical energy systems. Tenerife is the most populated of the islands in the Canary Archipelago (Spain) and has an isolated electrical system. It is envisaged for the horizon of 2040 that the island will have a high contribution of non-dispatchable renewable energies (fundamentally wind and solar photovoltaic). Tenerife also has exploitable high enthalpy geothermal resources. An energy planning model is implemented in this paper based on which different scenarios with high non-dispatchable renewable energy penetration in the island's electrical system are simulated. Geothermal energy is also incorporated in the simulations as a dispatchable renewable energy source, with the power required sized according to the hypotheses of each scenario. The results are compared according to different technical and economic parameters. An evaluation is also made of the influence that the capacity of the electrical system to take on higher non-dispatchable renewable power and the presence of energy accumulation systems might have on the minimization of losses in the non-dispatchable renewable energy capacity factor. The results of the simulated scenarios show that geothermal energy could meet up to 28.8% of the island's electrical energy demand, increasing the stability, flexibility and supply guarantee of system. A 100% renewable system could be possible through the incorporation of this energy source and the planning of energy accumulation systems. In the case study, the economic saving for Spain's electrical system could exceed 400 €million per year.

HelioCon: A roadmap for advanced heliostat technologies for concentrating solar power

Heliostat-based concentrating solar-thermal power (CSP) systems can offer immense potential to provide low-cost, dispatchable renewable thermal and electrical energy to help achieve 100% decarbonized energy infrastructure in the United States. Heliostats are a major determinant of both capital cost and performance of state-of-the-art commercial molten salt towers and Generation 3 CSP systems. In 2021, the U.S. Department of Energy (DOE) Solar Energy Technologies Office (SETO) launched the Heliostat Consortium (HelioCon), a five-year initiative to advance heliostat technologies. The HelioCon mission is threefold: (1) establish strategic core testing and modeling capabilities and infrastructure at national labs; (2) support heliostat technology development in relevant industries; and (3) serve as a central repository to integrate industry, academia, and other stakeholders for heliostat technology research, development, validation, and deployment. In this Perspective, HelioCon presents a roadmapping study on advancing heliostat technologies, intended as a central reference for the entire CSP community.

Demand-driven biogas production from Upflow Anaerobic Sludge Blanket (UASB) reactors to balance the power grid

Future energy systems necessitate dispatchable renewable energy to balance electrical grids with high shares of intermittent renewables. Biogas from anaerobic digestion (AD) can generate electricity on-demand. High-rate methanogenic reactors, such as the Upflow Anaerobic Sludge Blanket (UASB), can react quicker to variations in feeding as compared to traditional AD systems. In this study, experimental trials validated the feasibility of operating the UASB in a demand-driven manner. The UASB was operated with leachate produced from a hydrolysis reactor treating grass silage. The UASB demonstrated a high degree of flexibility in responding to variable feeding regimes. The intra-day biogas production rate could be increased by up to 123% under 4 hours in demand-driven operation, without significant deterioration in performance. A model based on kinetic analysis was developed to help align demand-driven operation with the grid. The findings suggest significant opportunities for UASBs to provide positive and negative balance to the power grid.

Market profitability of CSP-biomass hybrid power plants: Towards a firm supply of renewable energy

CSP-biomass hybrid power plants are promising options for displacing electricity from flexible fossil systems and increasing the share of dispatchable renewable energy in power grids. However, they are investment-intensive technologies whose competitiveness in electricity markets is still uncertain. This paper explores for the first time the profitability of CSP-biomass hybrid systems, assuming their participation as price-taking technologies in the Iberian day-ahead electricity market. For this purpose, a new economic evaluation metric called the Profitability Factor is proposed to extend the scope of the levelized cost of electricity (LCOE) by including the variability of market electricity prices. Besides, a stochastic approach integrating uncertainty related to investment costs, electricity prices and biomass costs through Monte-Carlo sampling methods has been applied. Results show that CSP-biomass schemes have up to 33% probability of being profitable in the electricity market before considering external financial support. High biomass share (approx. 76%) leads to a profitability increase of up to 0.11 USD/kWh (median value) compared to an equivalent CSP stand-alone plant. In addition, best-performing hybrid configurations would require a maximum add-in tariff between 0.040 and 0.071 USD/kWh (95% probability) to achieve grid parity. The resulting external financial support is significantly lower than those set through Power Purchase Agreements for the first generation CSP stand-alone plants (still in operation). Thus, CSP-biomass hybrid plants could provide flexibility and other services to power grids, which, if valued in the electricity market, would further increase the technology's competitiveness.

Semitransparent polymer solar cell/triboelectric nanogenerator hybrid systems: Synergistic solar and raindrop energy conversion for window-integrated applications

Development of photovoltaic (PV)-derived hybrid power systems can overcome the weather-dependent electricity production and increase the amount of dispatchable renewable energy generation. Herein, monolithic hybrid devices are developed via rational integration of high-performance semitransparent polymer solar cells (ST-PSCs) and liquid−solid triboelectric nanogenerators (TENGs). High-performance PSCs with efficiencies of 17.4% for rigid and 15.7% for flexible devices are achieved. Further electrode modifications and integration of transparent TENGs synergistically balance the above-bandgap photon harvesting and transparency in a broad wavelength range (380 − 1000 nm), yet significantly reduce the transmittance in the near-infrared wavelength range (1000 − 2500 nm) of hybrid devices. The hybrid devices simultaneously provide high visible light transparency, good color fidelity, efficient heat resistance and possibility to integrate on rigid and flexible substrates. The hybrid devices attain a high solar conversion efficiency of 10.1% under 1 sun, indicating efficient light-to-electricity conversion (a maximum electrical power output: 101 W m−2) on sunny days. The hybrid devices can also generate a maximum electrical power output of 2.62 W m−2 through waterdrop energy conversion, implying complementary green electricity production on rainy days. The controlled ambient temperature and specific transmittance windows provided by the hybrid devices sustain plant growth and highlight their great potential in agricultural applications. Gratifyingly, this work demonstrates the first example of ST-PSC/TENG hybrid systems for scaling up renewable power generation in different weather conditions, considering architectural and agricultural applications.

Bioenergy siting for low-carbon electricity supply in Australia

In the context of renewable energy (RE) generation, biomass resources are different to other renewable resources because they can be stored and transported. These characteristics make bioenergy a dispatchable renewable energy source. While this property is recognised as being very important in supporting the global energy transition, the potential of bioenergy in renewable electricity generation systems is not well understood owing to coarse assumptions around the distribution and availability of the resource.To address this limitation, this study derived a new database of prospective new bioenergy sites in Australia based on a geographic information system (GIS)- bioenergy siting algorithm. The optimised site selection relies on high-resolution biomass resource maps, resources transport distance and other key spatial constraints.Specifically, we present biomass resources maps for bagasse, forestry and cropping residues at a spatial resolution of 5 × 5 km. Australia is on one of the top global producer of sugar cane and as such bagasse was included as feedstock for bioenergy generation. The study identified potential utilisation of 1.0, 16.6 and 28.7 million tonnes of bagasse, forestry and stubble residues respectively at over 223 prospective sites.The new biomass site database is the most comprehensive and up-to-date compilation of prospective bioenergy sites in Australia. Moreover, by considering the real-world spatial constraints, this new data set allows for a reliable appraisal of potential biomass resource utilisation. While our study is focussed on Australia the approach is broadly applicable to other jurisdictions worldwide.

An Energy-Dense, Powerful, Robust Bipolar Zinc-Ferrocene Redox-Flow Battery.

Zinc metal represents a low-cost, high-capacity anode material to develop energy-dense aqueous redox-flow batteries (RFB). However, the energy-storage applications of traditional inorganic Zn halide flow batteries are primarily plagued by the material challenges of traditional halide cathode electrolytes (e.g., bromine), including corrosion, toxicity, and severe crossover. Herein, we report a bipolar zinc-ferrocene salt compound, zinc 1,1'-bis(3-sulfonatopropyl)ferrocene, Zn[Fc(SPr)2 ] (1.80 M solubility or 48.2 Ah L- charge storage capacity)-a robust, energy-dense, bipolar redox-active electrolyte material for RFBs. Zn[Fc(SPr)2 ]-based redox-flow batteries operated at high current densities of up to 200 mA cm-2 and delivered an energy efficiency of up to 81.5 % and a power density of up to 270.5 mW cm-2 . A Zn[Fc(SPr)2 ] flow battery demonstrated an energy density of 20.2 Wh L-1 and displayed nearly 100 % capacity retention for 2000 cycles (1284 h or 53.5 days).

Thermophotovoltaic efficiency of 40%

Thermophotovoltaics (TPVs) convert predominantly infrared wavelength light to electricity via the photovoltaic effect, and can enable approaches to energy storage1,2 and conversion3–9 that use higher temperature heat sources than the turbines that are ubiquitous in electricity production today. Since the first demonstration of 29% efficient TPVs (Fig. 1a) using an integrated back surface reflector and a tungsten emitter at 2,000 °C (ref. 10), TPV fabrication and performance have improved11,12. However, despite predictions that TPV efficiencies can exceed 50% (refs. 11,13,14), the demonstrated efficiencies are still only as high as 32%, albeit at much lower temperatures below 1,300 °C (refs. 13–15). Here we report the fabrication and measurement of TPV cells with efficiencies of more than 40% and experimentally demonstrate the efficiency of high-bandgap tandem TPV cells. The TPV cells are two-junction devices comprising III–V materials with bandgaps between 1.0 and 1.4 eV that are optimized for emitter temperatures of 1,900–2,400 °C. The cells exploit the concept of band-edge spectral filtering to obtain high efficiency, using highly reflective back surface reflectors to reject unusable sub-bandgap radiation back to the emitter. A 1.4/1.2 eV device reached a maximum efficiency of (41.1 ± 1)% operating at a power density of 2.39 W cm–2 and an emitter temperature of 2,400 °C. A 1.2/1.0 eV device reached a maximum efficiency of (39.3 ± 1)% operating at a power density of 1.8 W cm–2 and an emitter temperature of 2,127 °C. These cells can be integrated into a TPV system for thermal energy grid storage to enable dispatchable renewable energy. This creates a pathway for thermal energy grid storage to reach sufficiently high efficiency and sufficiently low cost to enable decarbonization of the electricity grid.

Optimization of green ammonia distribution systems for intercontinental energy transport

SummaryGreen ammonia is a promising hydrogen derivative which enables intercontinental transport of dispatchable renewable energy. This research describes the development of a model which optimizes a global green ammonia network, considering the costs of production, storage, and transport. In generating the model, we show economies of scale for green ammonia production are small beyond 1 million tonnes per annum (MMTPA), although benefits accrue up to a production rate of 10 MMTPA if a production facility is serviced by a new port or requires a long pipeline. The model demonstrates that optimal sites for ammonia production require not only an excellent renewable resource but also ample land from which energy can be harvested. Land limitations constrain project size in otherwise optimal locations and force production to more expensive sites. Comparison of current crude oil markets to future ammonia markets reveals a trend away from global supply hubs and toward demand centers serviced by regional production.

Dispatchable renewable energy from CSP and CSP+EGS in the Kingdom of Saudi Arabia

Renewable energy is part of the national sustainable energy mix for the Kingdom of Saudi Arabia (KSA). Relevant contributors are wind, and more importantly solar photovoltaic. Wind and solar photovoltaic (PV) are cheap, but they are suffering from variability, unpredictability, and in the case of solar PV, also intermittency. As the lithium-ion battery energy storage needed to make a stable grid only accepting these supplies is unaffordable, dispatchable renewable energy technologies are under study. Concentrated solar power (CSP) with thermal energy storage (TES) is the most promising opportunity. Requesting significant R&D, but having a large potential, enhanced geothermal systems (EGS) may help in the future, especially if coupled to CSP. Other relevant help may come from waste valorization. A renewable only grid managed by artificial intelligence (AI) operator will have to couple variable, unpredictable, and intermittent renewable energy supplies with battery energy storage and dispatchable renewable energy.

Techno-Economic Feasibility Analysis of Concentrated Solar Thermal Power Plants as Dispatchable Renewable Energy Resource of Pakistan: A case study of Tharparkar

Pakistan is identified to be one of the next-11 the top emerging economies of the world after the BRICS. This emphasizes the establishment of a competitive electricity market that can fulfil the demand of the country considering the environmental concerns. In this scenario reliability of power is something that cannot be compromised. Dispatchable power stations play a major role in balancing supply and demand; this balance is essential for maintaining the power cuts free country. All dispatchable power stations incorporate some form of storage particularly thermal or chemical (i.e. a stored fuel). Earlier dispatchable power was regarded as the generation which can start quickly and meet the peak demand requirements but arrival of renewables in power system has increased worth of its presence since it has just not to supply peak demand but also to meet during the unavailability of other renewable energy sources because of their intermittent behavior meanly at times of dark hours and slow wind speed. This study considers the viability of Concentrated Solar Thermal Power in Pakistan and thoroughly analyses several characteristics i.e., Availability of fuel, water, road and communication network, flexibility and environmental impacts of the technology for the cite of Tharparkar.

Coordinated Operation of Concentrating Solar Power Plant and Wind Farm for Frequency Regulation

As a dispatchable renewable energy technology, the fast ramping capability of concentrating solar power (CSP) can be exploited to provide regulation services. However, frequent adjustments in real-time power output of CSP, which stems out of strategies offered by ill-designed market, may affect the durability and the profitability of the CSP plant, especially when it provides fast regulation services in a real-time operation. We propose the coordinated operation of a CSP plant and wind farm by exploiting their complementarity in accuracy and durability for providing frequency regulation. The coordinated operation can respond to regulation signals effectively and achieve a better performance than conventional thermal generators. We further propose an optimal bidding strategy for both energy and frequency regulations for the coordinated operation of CSP plant and wind farm in day-ahead market (DAM). The validity of the coordinated operation model and the proposed bidding strategy is verified by a case study including a base case and sensitivity analyses on several impacting factors in electricity markets.

The roles of biomass and CSP in a 100 % renewable electricity supply in Australia

Because of the variability of wind and solar resources, high shares of wind and solar PV in power supply systems can lead to supply gaps during occasional low-resource periods. Due to their ability to meet demand in a short term, dispatchable renewable energy (RE) resources – biomass, concentrating solar power (CSP) and hydropower – can assist in meeting such supply gaps. In this study, we investigate the spatial and temporal configurations of least-cost 100% renewable power supply in Australia, at various levels of biomass resource use and CSP penetration. To this end, we carry out a high-resolution Geographic Information System (GIS)-based hourly electricity supply-demand matching simulation. We find that, based on the current existing biomass capacity (1.7 GW) installed in Australia, a 100% national RE supply is possible with around 146–148 GW system installed capacity at a levelized cost of electricity (LCoE) of 9–10 US' kWh−1 (95% level of confidence). Under a 5–15 times expansion of biomass, the system capacity would be reduced to around 70–110 GW at an LCoE of 6–8 US' kWh−1. Depending on limitations to the generation from biomass posed by competing land uses, CSP could play an important role in reducing the system capacity to nearly 120 GW.

Decentralized Renewable Hybrid Mini-Grids for Rural Communities: Culmination of the IREP Framework and Scale up to Urban Communities

The Integrated Rural Energy Planning (IREP) framework offers a unified road map for locating, planning and operating decentralized renewable hybrid off-grid energy systems for localized (rural) applications in low-income countries. This paper presents the culmination of the IREP framework and aims to illustrate the final step of the IREP framework for two communities in Nigeria. It is focused on two aspects. Firstly, the techno-economic modeling (investment and operation optimization) of a hybrid mini-grid system using HOMER Pro, a techno-economic evaluation tool; and evaluating the benefits of demand side management (DSM) based on energy efficiency on the overall system economics using a scenario-based approach. Secondly, the conceptualization of a sustainable business model using the business model canvas scheme to deliver measurable socio-economic impacts in these communities. The results provide valuable insights into rural electrification via renewable hybrid mini-grids powered primarily with solar photovoltaic technology. Transcending mere electricity access, electricity is provided for productive uses (considering disaggregated end-uses) by harnessing other dispatchable renewable energy resources such as waste biomass. Given high share of rural population in developing countries, these insights are applicable in these regions and further the realization of the United Nations’ goal of sustainable energy (SDG7) and sustainable cities and communities (SDG11).

Cost-effective flexibilisation of an 80 MWe retrofitted biomass power plants: Improved combustion control dynamics using virtual air flow sensors

As they deliver dispatchable renewable energy, biomass power plants are expected to play a key role in the stability of the future electricity grids dominated by intermittent renewables. Large-scale, biomass-fired power plants are often retrofitted from coal-fired plants. Such a fuel modification combined with decreasing pollutant emission limits and higher requirements in terms of load flexibility can lead to a decrease of the maximum power delivered by the unit. The limiting factors are partly related to the control systems of those plants. In this paper, we present the results of the upgrading of an 80 MWe, retrofitted biomass power plant that was achieved by improving the dynamic control of the combustion process. Thanks to the addition of virtual air flow sensors in the control system and the re-design of the combustion control loops, the undesired effects of a recent 10% power increase on NOx emissions were more than compensated. The accurate control of the local NOx production in the furnace resulted in a decrease of these emissions by 15% with an increased stability. This study will help increasing the cost-effectiveness of such conversions, and facilitate the development of dispatchable, renewable power units able to contribute to the grid stability.

An inexpensive storage material for molten salt based thermocline concepts: Stability of AlferRock in solar salt

The implementation of inexpensive scalable thermal energy storage will play a crucial role in the successful establishment of dispatchable renewable energy technologies. Storage based on molten nitrate salts is one of the most relevant technologies implemented in the GWh-scale. Yet, there is significant cost reduction potential in replacing the conventional two-tank system by a single-tank thermocline system. The latter involves the use of a single-tank design where a large fraction of the costly salt is replaced by an inexpensive filler material. Industrial waste materials such as AlferRock (red-mud-derived Fe2O3-rich ceramics), have significant potential since they are readily available in the Mt-range and have adequate thermal and mechanical resistance at the intended temperature of use. This study explicitly investigates the corrosion resistance of AlferRock in Solar Salt, 60% NaNO3-40% KNO3 mixture, at 560 °C. By variation of particle sizes classical exposure tests as well as accelerated test methods can be applied to understand the long-term stability of this waste material under relevant conditions. Salt chemistry and compositional changes in the filler are analyzed in terms of ion chromatography, titration, diffraction techniques (XRD) as well as electron microscopy (SEM) coupled with element mapping (EDX).

Developing New Chemistries for Redox Flow Batteries (AORFBs)

Aqueous organic redox flow batteries (AORFBs) have emerged as an attractive alternative RFB technology because redox active organic molecule materials are synthetically tunable, sustainable, and potentially low cost. The presentation will cover our recent research efforts in developing viologen anolyte materials for both anion and cation exchange pH neutral AORFBs with a variety of catholyte materials including ferrocene, TEMPO, ferrocyanide and halides. The viologen AORFBs demonstrated outstanding battery performance including an energy density of up to 30.4 Wh/L, a power density up to 220 mW/cm2, energy efficiency up to 72% at 60 mA/cm2, and capacity retention up to 99.999% per cycle up to 1000 cycles, representing the most stable organic RFB reported to date. In addition, this presentation will discuss mechanistic understandings of investigated redox active molecules using a variety of spectroscopic tools. Particularly, the presentation emphasizes that fundamental understandings of redox active electrolytes at molecular level are crucial to develop new generations of redox flow batteries for large scale and dispatchable renewable energy storage.