340 research outputs found
System-driven design of flexible nuclear power plant configurations with thermal energy storage
No full textNuclear power plants are expected to make an important contribution to the decarbonisation of electricity supply alongside variable renewable generation, especially if their operational flexibility is enhanced by coupling them with thermal energy storage. This paper presents a system modelling approach to identifying configurations of flexible nuclear plants that minimise the investment and operation costs in a decarbonised energy system, effectively proposing a system-driven design of flexible nuclear technology. Case studies presented in the paper explore the impact of system features on plant configuration choices. The results suggest that cost-efficient flexible nuclear configurations should adapt to the system they are located in. In the main low-carbon scenarios and assuming standard-size nuclear power plants (1,610 MWel), the lowest-cost system configuration included around 500 MWel of additional secondary generation capacity coupled to the nuclear power plants, with 4.5 GWhth of thermal storage capacity and a discharging duration of 2.2 h. Net system benefits per unit of flexible nuclear generation for the main scenarios were quantified at £29-33 m/yr for a wind-dominated system and £19-20 m/yr for a solar-dominated system
A system for electrotactile feedback using electronic skin and flexible matrix electrodes: Experimental evaluation
No full textMyoelectric prostheses are successfully controlled using muscle electrical activity, thereby restoring lost motor functions. However, the somatosensory feedback from the prosthesis to the user is still missing. The sensory substitution methods described in the literature comprise mostly simple position and force sensors combined with discrete stimulation units. The present study describes a novel system for sophisticated electrotactile feedback integrating advanced distributed sensing (electronic skin) and stimulation (matrix electrodes). The system was tested in eight healthy subjects who were asked to recognize the shape, trajectory, and direction of a set of dynamic movement patterns (single lines, geometrical objects, letters) presented on the electronic skin. The experiments demonstrated that the system successfully translated the mechanical interaction into the moving electrotactile profiles, which the subjects could recognize with a good performance (shape recognition: 86±8% lines, 73±13% geometries, 72±12% letters). In particular, the subjects could identify the movement direction with a high confidence. These results are in accordance with previous studies investigating the recognition of moving stimuli in human subjects. This is an important development towards closed-loop prostheses providing comprehensive and sophisticated tactile feedback to the user, facilitating the control and the embodiment of the artificial device into the user body scheme
Multi-model assessment of heat decarbonisation options in the UK using electricity and hydrogen
No full textDelivering low-carbon heat will require the substitution of natural gas with low-carbon alternatives such as electricity and hydrogen. The objective of this paper is to develop a method to soft-link two advanced, investment-optimising energy system models, RTN (Resource-Technology Network) and WeSIM (Whole-electricity System Investment Model), in order to assess cost-efficient heat decarbonisation pathways for the UK while utilising the respective strengths of the two models. The linking procedure included passing on hourly electricity prices from WeSIM as input to RTN, and returning capacities and locations of hydrogen generation and shares of electricity and hydrogen in heat supply from RTN to WeSIM. The outputs demonstrate that soft-linking can improve the quality of the solution, while providing useful insights into the cost-efficient pathways for zero-carbon heating. Quantitative results point to the cost-effectiveness of using a mix of electricity and hydrogen technologies for delivering zero-carbon heat, also demonstrating a high level of interaction between electricity and hydrogen infrastructure in a zero-carbon system. Hydrogen from gas reforming with carbon capture and storage can play a significant role in the medium term, while remaining a cost-efficient option for supplying peak heat demand in the longer term, with the bulk of heat demand being supplied by electric heat pumps
Modelling of national and local interactions between heat and electricity networks in low-carbon energy systems
No full textDecarbonisation of the heating and cooling sector is critical for achieving long-term energy and climate change objectives. Closer integration between heating/cooling and electricity systems can provide additional flexibility required to support the integration of variable renewables and other low-carbon energy sources. This paper proposes a framework for identifying cost-efficient solutions for supplying district heating systems within both operation and investment timescales, while considering local and national-level interactions between heat and electricity infrastructures. The proposed optimisation model minimises the levelised cost of a portfolio of heating technologies, and in particular Combined Heat and Power (CHP) and polygeneration systems, centralised heat pumps (HPs), centralised boilers and thermal energy storage (TES). A number of illustrative case studies are presented, quantifying the impact of renewable penetration, electricity price volatility, local grid constraints and local emission targets on optimal planning and operation of heat production assets. The sensitivity analysis demonstrates that the cost-optimal TES capacity could increase by 41–134% in order to manage a constraint in the local electricity grid, while in systems with higher RES penetration reflected in higher electricity price volatility it may be optimal to increase the TES capacity by 50–66% compared to constant prices, allowing centralised electric HP technologies to divert excess electricity produced by intermittent renewable generators to the heating sector. This confirms the importance of reflecting the whole-system value of heating technologies in the underlying cost-benefit analysis of heat networks
System-driven design and integration of low-carbon domestic heating technologies
No full textThis research explores various combinations of electric heat pumps (EHPs), hydrogen boilers (HBs), electric boilers (EBs), hydrogen absorption heat pumps (AHPs) and thermal energy storage (TES) to assess their potential for delivering cost-efficient low-carbon heat supply. The proposed technology-to-systems approach is based on comprehensive thermodynamic and component-costing models of various heating technologies, which are integrated into a whole-energy system optimisation model to determine cost-effective configurations of heating systems that minimise the overall cost for both the system and the end-user. Case studies presented in the study focus on two archetypal systems: (i) the North system, which is characterised by colder climate conditions and abundant wind resource; and (ii) the South system, which is characterised by a milder climate and higher solar energy potential. The results indicate a preference for a portfolio of low-carbon heating technologies including EHPs, EBs and HBs, coupled with a sizable amount of TES, while AHPs are not chosen, since, for the investigated conditions, their efficiency does not outweigh the high investment cost. Capacities of heat technologies are found to vary significantly depending on system properties such as the volume and diversity of heat demand and the availability profiles of renewable generation. The bulk of heat (83–97%) is delivered through EHPs, while the remainder is supplied by a mix of EBs and HBs. The results also suggest a strong impact of heat demand diversity on the cost-efficient mix of heating technologies, with higher diversity penalizing EHP relatively more than other, less capital-intensive heating options
Dual-parameter modulation improves stimulus localization in multichannel electrotactile stimulation
No full textAmong most challenging open issues in prosthetic research is the development of a robust bidirectional interface between a prosthesis and its user. Commercially available prosthetic systems are mechanically advanced, but they do not provide somatosensory feedback. Here, we present a novel non-invasive interface for multichannel electrotactile feedback, comprising a matrix of 24 pads, and we investigate the ability of able-bodied human subjects to localize the electrotactile stimulus delivered through the matrix. For this purpose, we tested conventional stimulation (same frequency for all pads) and a novel dual-parameter modulation scheme (interleaved frequency and intensity) designed to facilitate the spatial localization over the electrode. Electrotactile stimulation was also compared to mechanical stimulation of the same locations on the skin. Experimental results on eight able-bodied subjects demonstrated that the proposed interleaved coding substantially improved the spatial localization compared to same-frequency stimulation. The results also showed that same-frequency stimulation was equivalent to mechanical stimulation, whereas the performance with dual-parameter modulation was significantly better. These are encouraging outcomes for the application of a multichannel interface for the restoration of feedback in prosthetics. The high-resolution augmented interfaces might be used to explore novel scenarios for effective communication with the prosthesis user enabled by maximizing information transmission.</p
Artificial Skin and Electrotactile Stimulation for Advanced Tactile Feedback in Myoelectric Prostheses
No full textModern prosthetic arms and hands are sophisticated robotic devices that can
provide some of the motor functions lost due to an amputation. However,
none of the commonly used commercial systems restores somatosensory
feedback to its user. In principle, the latter can be achieved by recording data
from prosthesis sensors and conveying this information by stimulating the
sensory structures of the amputee using invasive and noninvasive interfaces.
Many such systems have been presented in the literature with promising
results; however, they all rely on using several stimulation points to transmit
information and hence suffer from a limited information bandwidth. In this
chapter, we propose a novel concept of a high-bandwidth feedback interface
that relies on advanced sensing and stimulation to convey a large amount
of information to the prosthesis user. The interface comprises an artificial
skin covering the prosthesis with a dense network of tactile sensors (taxels)
and a compact stimulation device delivering electrical current pulses through
a matrix electrode with many conductive pads. The state-of-the-art in the
two technologies that are required for the implementation of the proposed
concept are reviewed. This includes biomimetic e-skins that are suitable
for the application in a wearable scenario, stimulation systems integrating
a demultiplexing circuit to distribute electrical pulses, and flexible electrodes
that can be produced with arbitrary shape, size, and distribution of conductive
pads. Finally, the challenges in selecting feedback variables (raw signals
versus high-level features) and mapping of these variables into stimulation
parameters are addressed
Optimization methods and advanced applications for smart energy systems considering grid-interactive demand response
No full textThermo-economic assessment of flexible nuclear power plants in future low-carbon electricity systems: Role of thermal energy storage
No full textThe increasing penetration of intermittent renewable power will require additional flexibility from conventional plants, in order to follow the fluctuating renewable output while guaranteeing security of energy supply. In this context, coupling nuclear reactors with thermal energy storage could ensure a more continuous and efficient operation of nuclear power plants, while at other times allowing their operation to become more flexible and cost-effective. This study proposes options for upgrading a 1610-MWel nuclear power plant with the addition of a thermal energy storage system and secondary power generators. The total whole-system benefits of operating the proposed configuration are quantified for several scenarios in the context of the UK’s national electricity system using a whole-system model that minimises the total system costs. The proposed configuration allows the plant to generate up to 2130 MWel during peak load, representing an increase of 32% in nominal rated power. This 520 MWel of additional power is generated by secondary steam Rankine cycle systems (i.e., with optimised cycle thermal efficiencies of 24% and 30%) and by utilising thermal energy storage tanks with a total heat storage capacity of 1950 MWhth. Replacing conventional with flexible nuclear power plants is found to generate whole-system cost savings between £24.3m/yr and £88.9m/yr, with the highest benefit achieved when stored heat is fully discharged in 0.5 h. At an estimated cost of added flexibility of £42.7m/yr, the proposed flexibility upgrades to such nuclear power plants appears to be economically justified with net system benefits ranging from £4.0m/yr to £31.6m/yr for the examined low-carbon scenarios, provided that the number of flexible nuclear plants in the system is small. This suggests that the value of this technology is system dependent, and that system characteristics should be adequately considered when evaluating the benefits of different flexible nuclear plant configurations and choosing the most cost-effective designs and operational characteristics
Increasing Distributed Generation Penetration using Soft Normally-Open Points
No full textThis paper considers the effects of various voltage control solutions on facilitating an increase in allowable levels of distributed generation installation before voltage violations occur. In particular, the voltage control solution that is focused on is the implementation of `soft' normally-open points (SNOPs), a term which refers to power electronic devices installed in place of a normally-open point in a medium-voltage distribution network which allows for control of real and reactive power flows between each end point of its installation sites. While other benefits of SNOP installation are discussed, the intent of this paper is to determine whether SNOPs are a viable alternative to other voltage control strategies for this particular application. As such, the SNOPs ability to affect the voltage profile along feeders within a distribution system is focused on with other voltage control options used for comparative purposes. Results from studies on multiple network models with varying topologies are presented and a case study which considers economic benefits of increasing feasible DG penetration is also given
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