Distributed energy storage using residential hot water heaters

This paper proposes and analyses a new demand response technique for renewable energy regulation using smart hot water heaters that forecast water consumption at an individual dwelling level. Distributed thermal energy storage has many advantages, including high overall efficiency, use of existing infrastructure and a distributed nature. In addition, the use of a smart thermostatic controller enables the prediction of required water amounts and keeps temperatures at a level that minimises user discomfort while reacting to variations in the electricity network. Three cases are compared in this paper, normal operation, operation with demand response and operation following the proposed demand response mechanism that uses consumption forecasts. The results show that this technique can produce both up and down regulation, as well as increase water heater efficiency. When controlling water heaters without consumption forecast, the users experience discomfort in the form of hot water shortage, but after the full technique is applied, the shortage level drops to nearly the starting point. The amount of regulation power from a single dwelling is also discussed in this paper

Managing Flexible Loads in Residential Areas

Load flexibility in households is a promising option for efficient and reliable operation of future power systems. Due to the distributed nature of residential demand, coordination mechanisms have to cope with a large number of flexible units. This thesis provides a model for demand response analysis and proposes different mechanisms for coordinating flexible loads. In particular, the potential to match intermittent output of renewable generators with electricity demand is investigated

Sustainability Matchmaking: Exploration into using excess renewable energy to deliver ‘free’ energy to fuel poor homes – a preliminary case study in Ireland

The aggregated fuel cost of domestic hot water (DHW) generation in Ireland, in 2022, was €529M with associated emissions/load of 1.3MtCO2/289GWh. The shadow price of carbon monetises the negative impact of emissions, rising with time; DHW generation has an associated shadow carbon cost of €13M in 2022, rising to €42M in 2030 and €335M in 2050. In 2020, c12%/€441M of wind was curtailed or wasted as inter alia, there was no demand at times of high wind. Meanwhile, a ‘silent crisis’ is occurring in Ireland wherein one-in-two dwellings were considered in fuel poverty in 2022. Households in fuel poverty are known to limit DHW generation, impacting hygiene and well-being. As most Irish households have an electrical immersion already installed in DHW tanks, this research develops a preliminary (first round) wind allocation model to assess the potentials and economics of redeploying excess wind to heat DHW and, in the interest of a just-transition, focuses on households at risk of fuel poverty. It is found that fuel-poor households in Ireland could be theoretically provided with a ‘free’ full tank of hot water, once in every 3 weeks, redeploying 89% of overnight curtailed wind energy in 2019, realising a potential carbon cost saving to the Irish state of c€4M in 2030, rising to c€11M in 2050 along with a better quality of life for fuel-poor citizens. This research concludes this massive, readily deployable, shared, citizen-owned dispatch-down resource should be utilised and further research into redeployment of dispatch-down as a service is merited

Synergy of smart grids and hybrid distributed generation on the value of energy storage

In smart grids, demand response and distributed energy systems aim to provide a higher degree of flexibility for load-shifting operations and the leverage to control intermittent wind supply. In this more dynamic energy system, deployment of energy storage at the site of consumption is envisioned to create synergies with the local distributed generation (DG) system. From a large end-user perspective, this paper contributes to the practical understanding of smart grids by modelling the impact of real-time pricing schemes (smart grids) on a hybrid DG system (mixed generation for heating and electricity loads) coupled with storage units. Specifically, we address: How does the portfolio of DG units affect the value of energy storage? and, what is the value of energy storage when assessing different designs of demand response for the end-user? To this end, we formulate a dynamic optimization model to represent a real-life urban community’s energy system composed of a co-generation unit, gas boilers, electrical heaters and a wind turbine. We discuss the techno-economic benefits of complementing this end-user’s energy system with storage units (thermal storage and battery devices). The paper analyses the storages policy strategies to simultaneously satisfy heat and electricity demand through the efficient use of DG units under demand response mechanisms. Results indicate that the storage units reduce energy costs by 7–10% in electricity and 3% in gas charges. In cases with a large DG capacity, the supply–demand mismatch increases, making storage more valuable

Balancing of intermittent renewable generation in smart grid

This thesis researches a novel electricity demand response method and renewable energy management technique. It demonstrated the use of flow batteries and residential hot water heaters to balance wind power deviation from plan. The electricity supply-demand balancing problem becomes increasingly more difficult. A large portion of complexity to this problem comes from the fact that most renewable energy sources are inherently hard to control and intermittent. The increasing amount of renewable energy generation makes scientists research new supply-demand balancing possibilities to adapt for the changes. In this research wind power data was used in most cases to represent the supply side. The focus is on the actual generation deviation from plan, i.e. forecasting error. On the other hand, the methods developed in this thesis are not limited to wind power balancing. Two major approaches were analysed - heating ventilation and air conditioning system control (mainly focused on, but not limited to, residential hot water heaters) and hybrid power system comprising of thermal and hydro power plants together with utility scale flow batteries. These represent the consumption side or the demand response mechanism. The first approach focused on modelling the behaviour of residential end users. Artificial intelligence and machine learning techniques such as neural networks and Box-Jenkins methodology were used to learn and predict energy usage. Both joint and individual dwelling behaviour was considered. Model predictive control techniques were then used to send the exact real-time price and observe the change in electricity consumption. Also, novel individual hot water heater controllers were modelled with the ability to forecast and look ahead the required energy, while responding to electricity grid imbalance. It proved to be possible to balance the generation and increase system efficiency while maintaining user satisfaction. For the second approach, the hybrid multi-power plant system was exploited. Three different power sources were modelled, namely thermal power plant, hydro power pant and flow battery. These sources were ranked by the ability to rapidly change the output of electricity. The power that needs to be balanced was then routed to different power units according to their response times. The calculation of the best power dispatch is proposed using a cost function. The aim of this research was to accommodate for the wind power imbalance without sacrificing the health of the power plants (minimising load variations for sensitive units)

Forecasting hot water consumption in residential houses

An increased number of intermittent renewables poses a threat to the system balance. As a result, new tools and concepts, like advanced demand-side management and smart grid technologies, are required for the demand to meet supply. There is a need for higher consumer awareness and automatic response to a shortage or surplus of electricity. The distributed water heater can be considered as one of the most energy-intensive devices, where its energy demand is shiftable in time without influencing the comfort level. Tailored hot water usage predictions and advanced control techniques could enable these devices to supply ancillary energy balancing services. The paper analyses a set of hot water consumption data from residential dwellings. This work is an important foundation for the development of a demand-side management strategy based on hot water consumption forecasting at the level of individual residential houses. Various forecasting models, such as exponential smoothing, seasonal autoregressive integrated moving average, seasonal decomposition and a combination of them, are fitted to test different prediction techniques. These models outperform the chosen benchmark models (mean, naive and seasonal naive) and show better performance measure values. The results suggest that seasonal decomposition of the time series plays the most significant part in the accuracy of forecasting

Integrating Autonomous Load Controllers in Power Systems

Elektriske energisystemer undergår radikale forandringer, fordi et presserende behov for at nedsætte drivhusgasudledningen forudsætter en mere effektiv udnyttelse af energiressourcerne og en overgang til mere vedvarende energi. Nye vedvarende energikilder som vind og sol har et stort potentiale, men er karakteriseret ved en fluktuerende produktion, som kun delvist er forudsigelig. Styring af forbrug er allerede brugt i begrænset omfang for at forbedre leveringssikkerhed og effektiviteten af energisystemet. I energisystemer med en høj andel fluktuerende vedvarende energikilder kan intelligent styring af forbruget spille en stor rolle i balanceringen af systemet. Det store antal og den geografiske spredning af forbruget gør koordinering af forbrugets respons en udfordring. Nye kommunikationsteknologier har reduceret omkostningerne til at forbinde apparater og lover et ”Internet of Things" (”Tingenes internet") i fremtiden, hvor apparater er fuldt forbundet til en globalt datanetværk. Strenge realtids- og pålidelighedskrav til elsystemet har motiveret forskning i nye styrings arkitekturer velegnet til sådan et stort og komplekst system. Denne afhandling har fokus på et mellemstadie i evolutionen fra dagens passive belastninger mod et ”Internet of Things". Mere præcist udgøres dette mellemstadie af autonome apparater med sensorer, aktautorer, og software til at kontrollere lokale processer, men uden et digital kommunikationsinterface. Dearkitekturer der er undersøgt i denne afhandling er ret nye, så fokus ligger på gennemførlighed og system modelleringer. Tidligere forskning har foreslået brug af frekvensfølsomme autonome belastninger til at levere primær frekvensreserve. Denne forudgående forskning har fokuseret på effekten af autonome belastninger på et højt abstraktionsniveau i store energisystemer. Analyser på dette høj niveau analyser ignorerer en væsentlig forskel mellem konventionel frekvensereserve og frekvensfølsom belastning, nemlig effekten af reduceret belastningsmangfoldighed på frekvensresponsen. For at adressere denne mangel udførte man tidsdomænemodeller af frekvensfølsomme belastninger for at tage højde for den variation i frekvens responsen, som stammer fra variationen i belastningerne. Eksperimenter og analyser har afsløret potentielle ulemper ved høj andel af frekvensfølsom belastning: tidsafhængigheder i processer, som begrænser frekvensresponsen og overskridelse af spændingskrav i elforsyningsnettet. For at håndtere disse ulemper er to strategier fremlagt, som hver for sig tilføjer værdifulde tjenester udover at de forhindrer de førnævnte problemer. Den første strategi for at håndtere tidsafhængigheder er at drive et synkront netområde på ikke-nominelle frekvenser i diskrete domæner. Det begrænser uønsket skift af tilstand i de frekvensfølsomme belastninger og fungerer som direkte kontrol af den pågældende belastning. Store synkrone maskiner kan kun langsomt ændre frekvensens setpunkt, hvilket begrænser takten, hvorved kontrol kommandoer kan blive sendt. Derimod har energikilder, der er forbundet igennem effektelektronik, mulighed for at ændre frekvenssetpunkt meget hurtigt og kan skabe en strøm af kommandoer som kan tolkes med eksisterende kommunikations protokoller. Den anden strategi er at forene en spændingsfølsom styring med en frekvensfølsom styring, og på den måde direkte undgå uønskede spændinger. Denne spændingsfølsomme styring kan også blive brugt alene, uden den frekvensfølsomme del, for at stabilisere spænding og reducere behovet for netforstærkninger alle steder hvor lavere spænding falder sammen med højere forbrug. En frekvensfølsom styring er udviklet, implementeret, og testet under realistiske forhold. Resultaterne viste en stor potentiel ressource, i nogen tilfælde større end gennemsnittet af effektforbruget. Nøjagtigheden af belastningsmodeller var verificeret ved hjælp af måledata. En spændingsfølsom styring var udviklet, implementeret og testet under laboratorieforhold, og dens opførsel var simuleret i repræsentative energisystemer. Problemerne forårsaget af udbredt anvendelse af frekvensfølsomme belastninger var simuleret, og afværgelsesstrategier anvendt. For at underbygge gennemførligheden af det fremlagte frekvensbaserede belastningskontrolsystem er analyser af eksisterende energisystemer blevet gennemført med henvisninger til tekniske standarder, specifikationer og endeligt data indsamlet fra systemer i drift. Resultaterne viser, at frekvens- og spændingsfølsomme autonome belastninger er leveringsdygtige alternativer til konventionel frekvens- og spændingsregulerende teknikker. Når de bruges sammen, komplementerer de hinanden. I systemer, hvor operatøren har mulighed for at regulere frekvensen centralt, kan de direkte kontrollere de ellers autonome frekvensfølsomme apparater. Derudover, i systemer, hvor frekvens reguleringsressourcer tillader hurtigt skift af frekvenssetpunkt, for eksempel micro-grids, kan energikilder blive brugt som sender i et lavhastigheds-envejs- kommunikationssystem.Electric energy systems stand on the brink of radical change as the urgent need to reduce greenhouse gas emissions pushes more efficient utilization of energy resources and the adoption of renewable energy sources. New renewable sources such as wind and solar have a large potential, but they are characterized by variable generation that is only partly predictable. Managing loads is already used in limited circumstances to improve security and efficiency of the power system. In power systems with a large penetration of variable generation, load management has large role to play in adapting consumption to the fluctuating production. The large number and geographic dispersion of loads make coordinating their behavior challenging. New telecommunication technology has reduced the cost of linking devices, promising a future "Internet of Things" where loads are fully networked. Strict real-time constraints and reliability constraints in power systems are motivating research into new control architectures suitable for such a large and complex system. The focus of this thesis is on an intermediate stage of evolution between today's largely passive loads and a future "Internet of Things". Specifically, this intermediate stage is autonomous devices with sensors, actuators, and software to control local processes but without digital communications interfaces. The architectures explored in this thesis are newly emergent, so the focus is on feasibility and system modeling. Earlier research has proposed using autonomous load controllers to provide primary frequency reserves. This previous research has mainly focused on the effect of autonomous loads at a high level of abstraction, in large-scale power systems. High-level analysis ignores a significant difference between conventional frequency reserves and frequency-sensitive loads, namely the effects of reduced load diversity on the frequency response. To address this shortfall, time-domain models of the frequency-sensitive loads were constructed that include the variation of frequency response resulting from changes in load diversity. Experiments and analysis have revealed potential drawbacks of high penetrations of autonomous frequency-sensitive loads: time constraints on the underlying processes which reduce the frequency response, and violations of voltage constraints in the distribution systems arising from synchronized loads. Addressing these drawbacks, two mitigation strategies are proposed, each of which add valuable services in addition to preventing the above mentioned problems. The first strategy to address time constraints is to operate a synchronous power system at off-nominal frequencies in discrete domains, thus limiting unintended state changes of frequency-sensitive loads. The effect of operating in discrete frequency domains is to dispatch frequency-sensitive loads. Large synchronous machines can only change their frequency setpoint slowly, greatly limiting the rate of change of dispatch symbols. However, energy sources interfaced with power electronics can change their frequency setpoint very rapidly, creating a stream of symbols that can be decoded with conventional telecommunication protocols. The second strategy is to merge a voltage-sensitive control loop into the frequency-sensitive controller to directly avoid violations of voltage constraints. This voltage-sensitive controller can also operate alone, without the frequency-sensitive controller, to provide voltage regulation service and increase load diversity in any distribution network where lower voltage level corresponds to higher load.The frequency-sensitive load controller has been designed, implemented, and tested in real-life settings. Its performance demonstrated a large potential resource, in some cases greater than the average power consumption. The accuracy of load models was validated by comparison with field data. A voltage-sensitive controller was designed, implemented in an embedded system, and tested in laboratory settings. The voltage-sensitive controller was also implemented in a software simulation environment and tested in representative distribution systems. The problems anticipated by large-scale deployment of frequency-sensitive loads were simulated, and mitigation strategies were applied. To support the feasibility of the proposed frequency dispatch system, analysis of existing power systems was conducted using existing technical norms, specifications, and data collected from operating power systems. The results shows that frequency-sensitive and voltage-sensitive autonomous load are viable alternatives to conventional frequency and voltage control devices. When used in combination, they complement each other. In systems where the operator has centrally dispatchable resources to regulate frequency, these resources can be used to dispatch otherwise autonomous frequency-sensitive loads. Moreover, where centrally dispatchable frequency regulation resources can rapidly change operating points, such as in a micro-grid, the energy sources can be used as transmitters for a ultra-low-bandwidth uni-directional power line communication system

The Potential of Utilising Residential Demand Response to Balance the Fluctuation of Wind Power in New Zealand

The substantial penetration of wind power introduces increased flexibility requirements on the power system and puts increased pressure on the instantaneous reserve levels required. Instantaneous reserves are a security product that ensures that electricity demand can continue to be met in the event of unplanned generation or transmission interruptions. This reserve must be available to respond very quickly to generation-demand variability. While this is an integral component of the power system, providing instantaneous reserve increases the production cost of power. More calls from energy researchers and stakeholders ask for loads to play an increasingly important role in balancing the short timescale fluctuations in generated wind power. The purpose of this study is to assess the current level of demand responsiveness among domestic refrigerators, freezers, and water heaters and their potential to contribute towards instantaneous reserve and balance the fluctuation of wind. Refrigerators, freezers, and water heaters can generally store energy due to their thermal mass. Interrupting these domestic loads for short time by employing direct load control strategies makes it possible to control these appliances by turning them on or off before their reach their maximum or minimum temperatures or by slightly modifying their temperature set point. Using this strategy helps to ensure that the overall satisfaction of consumers should not be affected. This study first modelled the load profiles of the participated residential appliances and statistically assessed the potential of controlling these residential loads using direct load control strategies to contribute towards instantaneous reserves to mitigate and balance the fluctuation of wind power in the years: 2014, 2020 and 2030. In the second section, it demonstrated the capabilities of the assessed residential responsive loads within Wellington Region network to compensate for and balance the fluctuation of wind power generated from the West Wind Farm in seven selected days in 2013-2014 as a showcase. Such technology can enable a power system operator to remove the burden of both providing instantaneous reserve from conventional sources, and instead maintain such capacity from available residential demand response. The study ends with recommendations to engage residential loads in fast timescale demand response and suggests directions for future research