Benefits of demand-side response in providing frequency response service in the future GB power system

The demand for ancillary service is expected to increase significantly in the future Great Britain (GB) electricity system due to high penetration of wind. In particular, the need for frequency response, required to deal with sudden frequency drops following a loss of generator, will increase because of the limited inertia capability of wind plants. This paper quantifies the requirements for primary frequency response and analyses the benefits of frequency response provision from demand-side response (DSR). The results show dramatic changes in frequency response requirements driven by high penetration of wind. Case studies carried out by using an advanced stochastic generation scheduling model suggest that the provision of frequency response from DSR could greatly reduce the system operation cost, wind curtailment, and carbon emissions in the future GB system characterized by high penetration of wind. Furthermore, the results demonstrate that the benefit of DSR shows significant diurnal and seasonal variation, whereas an even more rapid (instant) delivery of frequency response from DSR could provide significant additional value. Our studies also indicate that the competing technologies to DSR, namely battery storage, and more flexible generation could potentially reduce its value by up to 35%, still leaving significant room to deploy DSR as frequency response provider

S.E.M. Analysis of the Interaction Between Green Or and the Dentine

Svrha ovoga rada bila je ispitati međuodnos desenzibilizatora dentina Green Ora i restorativnih materijala uporabljenih kod adhezijskih preparacija te možebitni učinak na sposobnost adhezije tih materijala na caklinu i dentin. Green Or se rabi za smanjenje bolne preosjetljivosti zuba, tako da uzrokuje mehaničko zatvaranje dentinskih tubulusa ili inhibira repolarizaciju neurona. Mehaničko zatvaranje dentinskih tubulusa postiže se stvaranjem kompaktnoga kristaličnog precipitata, koji pokriva površinu izloženoga dentina, a depolarizacija neurona postiže se otpuštanjem kalijeva iona. Ispitivanje je provedeno na 6 humanih trećih molara izvađenih zbog ortodontskih ili parodontoloških indikacija. Zubi su podijeljeni na tri skupine od dva zuba s obzirom na materijal uporabljen za ispun: tekući i mikro-hibridni kompozit ili srebrni amalgam. U svakoj smo skupini na zidove dentinskoga kaviteta aplicirali desenzibilizator Green Or te S.E.M. raščlambom, pri velikom stupnju povećanja, promatrali kakav je njegov utjecaj na spoj između dentina i restorativnoga materijala. Svi su se uzorci proučavali na Skening Elektronskom Mikroskopu (S.E.M.) Zavoda za kontrolu kvalitete Pliva u Zagrebu. Rezultati S.E.M. raščlambe pri velikom stupnju povećanja, u sve tri proučavane skupine zuba, pokazuju usku povezanost primijenjenih materijala s caklinom i dentinom. Mikroskopiranje spojišta dentina i materijala korištenih za ispun u Grupi A i B pokazalo je da upotreba green ora ne ometa adhezijsku sposobnost adhezivno-kompozitnih materijala za dentinsku plohu niti utječe na brtvljenje cakline i dentina. Sloj desenzibilizatora nerazlučivo je povezan sa slojem adheziva i kompozita što omogućuje čvrsto prianjanje na dentinske zidove kaviteta. Rezultati dobiveni u skupini C, u kojoj je upotrijebljen srebrni amalgam kao materijal za punjenje, pokazuju da Green Or također nije utjecao na adheziju slitine za stjenke cakline i dentina. Prema mnogim autorima upotreba Green Ora kao podloge kod kompozitnih ili amalgamskih ispuna nije smanjivala adhezijsku sposobnost spomenutih restorativnih materijala. Rezultati dobiveni u istraživanju pokazuju da Green Or stvara sloj koji jednolično prekriva i zatvara dentinske tubuluse i omogućuje dobru izolaciju dubokih dijelova dentina od restorativnih materijala. Time se postiže zadovoljavajuće brtvljenje dentinskih tubulusa i smanjuje dentinska preosjetljivost na intraoralne nociceptivne stimulanse, gotovo u njezinoj akutnoj fazi. Promatranje različitih dijelova dentina na skening elektronskom mikroskopu (S.E.M.) pokazuje da desenzibilizator dentina uspostavlja zadovoljavajuću i snažnu povezanost s različitim adhezivnim materijalima ili sa srebrnim amalgamom uporabljenima u istraživanju.The aim of this study was to evaluate the interaction between Green Or, a dentinal desensitizer, and restorative materials used in adhesive preparation, and its possible influence on the adhesiveness of those materials to the enamel and dentine. Green Or is used to reduce pain sensation in hypersensitive teeth by mehanical occlusion of the dentine tubules or the inhibition of neuronal repolarization. Mehanical occlusion is made by blocking the dentine tubules with a compact crystaline precipitate that covers the exposed dentine surface, while the neural depolarization is produce by released potassium ions. The investigation included 6 human third molars extracted for orthodontic or periodontal reasons. The teeth were divided into three groups of 2 teeth each according to the type of material used for filling: fluid and mycrohybrid composites, and silver amalgam. In every group we applied the desensitizer green or onto the walls of the dental cavities and with S.E.M. observation at high degree of magnification investigated how it affevts the conjunction of dentine and restorative materials. All speciments were observed with the Scansion Electron Microscope (S.E.M.) at the “Department of Quality Control” pliva in Zagreb. The results of S.E.M. observation at very high magnification in all three investigated groups show the close connection of the applied materials to the enamel an dentine. Microscoping the conjunction beetween the dentine and materials we used for filling in Groups A and B, showed that the use of Green Or does not alter the adhesiveness of the restorative adhesive-composite materials to the dental wall, nor does it modifies their sealing action on enamel and dentine. The desensitizer layer is indistinguishable with the adhesive-composite layers which enables strong adherence to the dentinal walls of cavities. The results obtained in group C specimens, in which silver amalgam was used as a filling material, show that Green Or did not interfere with the adhesion process of the alloy and the enamel and dentine. As found by many authors, the desensitizer Green Or, when used as a liner in the tooth filled with resins or alloys, did not decrease the adhesion of the restorative materials. The results obtained in the study show that Green Or is able to form a uniform layer that covers and occludes dentine tubules and enables good isolation of deep dentine from the restorative materials. This should constitute an efficacious sealing of dentinal tubules and provoke a decrease in dentinal sensitivity to intraoral nociceptive stimuli, almost in the acute phase. Observation of different dental sections with a Scanning Electron Microscope (S.E.M.) shows that desensitizer established an efficient and powerful interconnection with the different adhesive materials or silver amalgam utilized in the study

Benefits of smart control of hybrid heat pumps: an analysis of field trial data

Smart hybrid heat pumps have the capability to perform smart switching between electricity and gas by employing a fully-optimized control technology with predictive demand-side management to automatically use the most cost-effective heating mode across time. This enables a mechanism for delivering flexible demand-side response in a domestic setting. This paper conducts a comprehensive analysis of the fine-grained data collected during the world’s first sizable field trial of smart hybrid heat pumps to present the benefits of the smart control technology. More specifically, a novel flexibility quantification framework is proposed to estimate the capability of heat pump demand shifting based on preheating. Within the proposed framework, accurate estimation of baseline heat demand during the days with interventions is fundamentally critical for understanding the effectiveness of smart control. Furthermore, diversity of heat pump demand is quantified across different numbers of households as an important input into electricity distribution network planning. Finally, the observed values of the Coefficient of Performance (COP) have been analyzed to demonstrate that the smart control can optimize the heat pump operation while taking into account a variety of parameters including the heat pump output water temperature, therefore delivering higher average COP values by maximizing the operating efficiency of the heat pump. Finally, the results of the whole-system assessment of smart hybrid heat pumps demonstrate that the system value of smart control is between 2.1 and 5.3 £ bn/year

Application of liquid-air and pumped-thermal electricity storage systems in low-carbon electricity systems

In this study, w e consider two medium - to large - scale electricity storage systems currently under development, namely ‘Liquid - Air Energy Storage’ (LAES) and ‘Pumped - Therma l Electricity Storage’ (PTES). Consistent t hermodynamic models and costing methodologies for the two systems are presented , with the object ive of integrating the characteristics of these technologies in to a whole - electricity system assessment model , and assess ing the ir system - level value in different scenarios for power system decarbonisation . It is found that the value of storage varies greatly depending on the cumulative installed ca pacity of storage in the electrical system, with the s torage technologies provid ing greater marginal benefits at low p enetrations . T wo carbon target scenarios showed similar results, with a limited effect of the carbon target on the system value of storage (although it is noted that this may change for even more ambitious carbon targets). On the other hand, the location and installed capacity of storage plants is found to have a significant impact on the syste m value and acceptable cost of the se technologies. The w hole - system value of PTES was found to be slightly higher than that of LAES, driven by a higher storage duration and efficiency, however, due to the higher power capital cost of PTES, this becomes les s attractive for implementat ion at lower volumes than LAES

Modelling of national and local interactions between heat and electricity networks in low-carbon energy systems

Decarbonisation 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

Multi-scale modelling of interactions between heat and electricity networks in low-carbon energy systems

Decarbonisation 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 approach cost-optimises the portfolio of heating technologies, including Combined Heat and Power (CHP) and polygeneration systems, large-scale heat pumps (HPs), gas boilers and thermal energy storage (TES). It is implemented as a mixed-integer linear programming (MILP) optimisation model that minimises net cost of heat supply, taking into account investment and operation cost of heat supply and storage options as well as the impact of local and wider interactions with the electricity system

Thermo-economic assessment of flexible nuclear power plants in the UK’s future low-carbon electricity system: role of thermal energy storage

Nuclear power plants are commonly operated as baseload units due to their low variable costs, high investment costs and limited ability to modulate their output. The increasing penetration of intermittent renewable power will require additional flexibility from conventional generation units, 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 considers options for upgrading a 1610-MWel nuclear power plant with the addition of a thermal energy storage system and secondary power generators. The analysed configuration allows the plant to generate up to 2130 MWel during peak load, representing an increase of 32% in nominal rated power. The gross whole-system benefits of operating the proposed configuration are quantified over several scenarios for the UK’s low-carbon electricity system. Replacing conventional with flexible nuclear plant configuration is found to generate system cost savings that are between £24.3m/yr and £88.9m/yr, with the highest benefit achieved when stored heat is fully discharged in 0.5 hours (the default case is 1 hour). At an estimated cost of added flexibility of £42.7m/yr, the proposed flexibility upgrade to a nuclear power plant appears to be economically justified for a wide range of low-carbon scenarios, provided that the number of flexible nuclear units in the system is small

Whole-systems assessment of the value of energy storage in low-carbon electricity systems

Energy storage represents one of the key enabling technologies to facilitate an efficient system integration of intermittent renewable generation and electrified transport and heating demand. This paper presents a novel whole-systems approach to valuing the contribution of grid-scale electricity storage. This approach simultaneously optimizes investment into new generation, network and storage capacity, while minimising system operation cost, and also considering reserve and security requirements. Case studies on the system of Great Britain (GB) with high share of renewable generation demonstrate that energy storage can simultaneously bring benefits to several sectors, including generation, transmission and distribution, while supporting real-time system balancing. The analysis distinguishes between bulk and distributed storage applications, while also considering the competition against other technologies, such as flexible generation, interconnection and demand-side response

System-driven design of hybrid electricity- and hydrogen-based systems for domestic heat decarbonisation

For the purpose of Open Access, the authors have applied a CC BY public copyright licence to any Author Accepted Manuscript version arising from this submission.This paper 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. A technology-to-systems approach is adopted in the paper 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 paper focus on two archetypal systems that differ in terms of heat demand and availability profiles of renewables (North and South). Modelling results indicate a preference for a portfolio of low-carbon heating technologies including EHPs, EBs, HBs and TES, while AHPs are not chosen for investment due to their high investment cost. Capacities of the four heating 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, HBs and TES. The results also suggest a strong impact of heat demand diversity on the cost-efficient mix of heating technologies, with higher diversity (i.e. lower coincidence factor) favouring less EHP and more of the other, less capital-intensive heating options. Finally, if only a subset of heating technologies is available for investment, the modelling suggests that coupling EHPs with TES is the second best solution in the North system, while in the South it was the combination of EHPs and EBs.UK Engineering and Physical Sciences Research Council (EPSRC) grant number EP/R045518/1 (IDLES Programme)