Electric Water Heaters Research Articles

Optimal Scheduling Strategy of Building Integrated Photovoltaic Microgrid Considering Virtual Energy Storage

Building integrated photovoltaic (BIPV) is one of the most efficient ways to utilize renewable energy in buildings. However, the stochastic characteristic of PV power generation and load challenges the optimal dispatch of the BIPV. This paper proposes an optimal scheduling strategy of BIPV microgrid considering virtual energy storage (VES), which intends to further improve the operating economy of a BIPV microgrid. Firstly, existing research findings and gaps in this research area were analyzed. Then, the mathematical model of each unit in the system was created, meanwhile, the air conditioner-based VES (ACVES) model and electric water heater-based VES (EWHVES) model are built by exploiting the heat/cold storage capability of building and the electric water heater, respectively. Next, the optimal scheduling model considering the VES is designed. Finally, the optimal scheduling model is solved by CPLEX to obtain the optimal scheduling strategy that reduces the operating cost of the system. Simulation results demonstrate that the proposed strategy can reduce the operating cost of the system. Furthermore, the VES shows the potential to replace the battery energy storage system.

Identification of hot water end-use process of electric water heaters from energy measurements

This paper presents an algorithm for the identification of parameters for a stochastic hot water end-use process that drives a homogeneous population of thermostatically controlled electric water heaters (EWH). Usually, only metered interval consumption data (kWh) is collected and the hot water end-use process is unobservable to utility and aggregators. However, the availability of EWHs for demand response (DR) is closely coupled with the hot water end-use process. In this context, the hot water end-use process is modeled as a two-state Markov chain (Use / No use), which causes the thermostatic ON-OFF switching process to behave as a Markov renewal process (MRP). A set of first passage-time problems is developed to obtain the moments of the transition probability densities of the MRP. These problems are addressed by establishing a system of coupled partial differential equations characterizing the temperature evolution of the EWH population. A key quantity in the methodology for estimating the parameters is the total time an EWH is ON within a period of interest. It is referred to as the total busy time. Total busy time in this approach is a random variable for which analytical expressions of the moments are developed as a function of the metered window length. The latter expressions become the basis of a hot water demand model identification algorithm which is validated using agent-based simulations of EWHs.

Technical and Lifetime Cost Benefit Analysis of RET Solar Water Heater a Way to Substitute Electrical Water Heaters for Domestic use:

Technical and Lifetime Cost Benefit Analysis of RET Solar Water Heater a Way to Substitute Electrical Water Heaters for Domestic use: - written by Tamerat Demeke Agonafer , Abdulbasit Nasir Jemal published on 2020/08/04 download full article with reference data and citations

Primary Frequency Control in Isolated Microgrids Using Thermostatically Controllable Loads

Hybrid renewable energy sources (RES)-diesel systems are now being considered as an economic, attractive and clean option for remote isolated microgrids, to offset diesel consumption by displacing generation from conventional units; however, system security and stability is a challenge as the penetration of RES increases. In this context, Demand Response (DR) can be used to increase grid flexibility, improve efficiency, and facilitate the penetration of RES. Thermostatically controllable loads (TCLs), i.e., electric water heaters (EWHs), air conditioners (ACs), and ground source heat pumps (GSHPs), are ideal candidates to participate in such a DR strategy, since their power consumption can be controlled without affecting consumer comfort. Therefore, this paper presents novel, computationally efficient, and adequate thermo-electrical dynamic models of ACs and GSHPs, along with an existing model of EWHs, to adapt and improve a decentralized DR strategy for Direct Load Control (DLC) for primary frequency regulation in hybrid isolated microgrids. Different cases studies are presented for a real microgrid to analyze and compare the system frequency response and determine the adequacy of the proposed approach and models, demonstrating their effectiveness for primary frequency control provision to facilitate higher RES penetrations.

Electricity Use Behaviour in a High-Income Neighbourhood in Johannesburg, South Africa

Worldwide, households’ consumption of electricity contributes to a substantial proportion of total national energy demand. Thus, the residential sector is a major entity in efforts to define and achieve global sustainability goals. Understanding electricity use behaviour and factors underlying behaviour is critical for designing behaviour change interventions, particularly in contexts characterised by fast-growing economies, burgeoning number of high-income households, and consumption growth. However, relative to developed economies, very little is known on this subject in South Africa. Using structured questionnaires, this study examines electricity use behaviour among high-income households in Johannesburg, South Africa. Findings indicate evidence of electricity-saving behaviour, but the proportion of households doing so was less than 50% for many actions, indicative of widespread wasteful habits. Other particular wasteful electricity use habits include leaving electronic gadgets and appliances on ‘standby’ mode, not turning off electric water heaters and not defrosting fridges without automatic settings. The findings lend support to the positive and negative influence of self-transcendence and egoistic values respectively on environmental behaviour, but other value orientations did not yield significant relationships. The implications of the findings on practical interventions for and theoretical constructs underlying strategies for environmentally-sustainable behaviour are discussed.

Integration of heat pipe solar water heating systems with different residential households: An energy, environmental, and economic evaluation

This study presents a detailed methodology for evaluating the energy, environmental, and economic contributions of heat pipe solar water heating (HPSWH) systems in various households. The hot water consumption patterns of Perth residents in Australia in one, two, and four-occupant houses are extracted in hourly basis throughout a year. The annual performance of the system is evaluated based on parameters such as saved energy, solar fraction, avoided CO2 emission, saved money, and payback period. Moreover, an experimental rig is designed, manufactured, and tested. The results show that the contribution of the solar system in meeting the hot water demand is around 99% in summer, while this contribution drops to 36–51% in winter. Almost 387–1146.8 kg of CO2 emissions can be avoided annually in Perth if HPSWH systems are integrated with the conventional heating systems. In addition, it is shown that the HPSWH system has its most economic justification in households with higher number of occupants. Moreover, the payback period is much lower for houses with conventional electric water heating systems compared to houses with LPG systems.

As one falls, another rises? Residential peak load reduction through electricity rate structures

In this study, we analyze the potential for time-varying electricity rate structures to reduce and/or shift peak demand in the residential sector. To do so, we develop a convex optimization model in which a household with four major appliances minimizes electricity costs, with marginally increasing penalties for deviating from temperature set-points or operating appliances at inconvenient times. The four specific appliances we include are: heating, ventilation and air-conditioning (HVAC) systems, electric water heaters (EWHs), electric vehicles (EVs), and pool pumps (PPs). The study incorporates a one-parameter thermal model of the home and the electric water heater, so that the penalties can apply to the room and water temperatures rather than the total appliance loads. Analysis is performed on a community of 100 single-family detached homes in Austin, TX. These homes each host a combination of the four end-use devices while some also have onsite solar panels. We find that dynamic pricing effectively shifts the residential peak away from the time of overall peak load across the electricity system, but can have the adverse impact of making the residential peak higher. The energy consumption does not differ significantly across the different rate structures. Thus, we infer that the time-varying rates encourage customers to concentrate their electricity demand within low-price hours to the extent possible without incurring significant inconvenience. By incorporating the novel approach of including monetary value of customer behavior in price-based demand response models, this study builds a tool to realistically quantify peak load reduction and shifts in the residential sector.

Sustainable Residential Building Considerations for Rural Areas: A Case Study

Intelligent use of rural residential land and sustainable construction is inexorably linked to cost; however, options exist that are eco-friendly and have a positive return on investment. In 2011, a research residence was built to evaluate various land-use and sustainable components. This Texas house has subsequently been used for both residential and research purposes. The purpose of this case study was to evaluate break-even construction considerations, to assess environmental impacts, and to evaluate qualitatively efficacy of sustainable options incorporated in the research residence. Some of the specific components discussed are home site placement (directional positioning); materiel acquisition (transportation); wood product minimization; rainwater harvesting; wastewater management; grid-tied solar array power; electric car charging via a solar array; geothermal heating and cooling; insulation selection; windows, fixtures, and appliance selection; and on-demand electric water heaters for guest areas. This study seeks to identify the impact of proper land use and sustainable techniques on the environment and return-on-investment in rural areas. Break-even and 15-year Net Present Value (NPV) analysis at 3% and 5% cost of capital were used to evaluate traditional construction, partially sustainable construction, and fully sustainable construction options for the case study house, which was built sustainably. The additional cost of sustainable construction is estimated at $54,329. At 3%, the analysis suggests a 15-year NPV of $334,355 (traditional) versus $250,339 million (sustainable) for a difference of $84K. At 5% cost of capital, that difference falls to $63K. The total estimated annual difference in carbon emissions is 4.326 million g/CO2e for this research residence. The results indicate that good choices for quick return-on-investment in rural construction would be the use of engineered lumber, Icynene foam, and Energy Star windows and doors. Medium-term options include photovoltaic systems (PVS) capable of powering the home and an electric car. Sustainable construction options should positively affect the environment and the pocketbook. Regulations and code should require adoption of short-range, break-even sustainable solutions in residential construction.

Effect of thermostat position and its set-point temperature on the performance of a domestic electric water heater

Abstract In domestic buildings, water is generally heated by an immersion type electric water heater, equipped with a thermostat as one unit, which is fitted at the bottom of the tank. Despite these systems are driven by electric energy, which is not favorable compared to direct solar water heaters, they are still widely used due to the practicality and low installation costs. In current use of electric water heaters, thermostat position and water set-point temperature are crucial and these parameters should be optimized for efficient and economic use of such systems. In this study, the impact of placing the thermostat at three different elevations; namely near the bottom, in the middle and near the top of an EWH is experimentally investigated. In addition, the effect of temperature setting of the thermostat near the bottom of the tank, on the performance of the EWH is experimentally investigated. Data were obtained for 5 L/min discharging rate of the heated water. The discharge efficiencies are found to be higher for the thermostat position at the bottom, while the discharge efficiencies for thermostat positions in the middle and near the top are very close but lower than that of the one near the bottom.

Balancing supply and demand in the presence of renewable generation via demand response for electric water heaters

With the increasing presence of renewable energy sources in the electrical power grid, demand response via thermostatic appliances such as electric water heaters is a promising way to compensate for the significant variability in renewable power generation. We propose a multistage stochastic optimization model that computes the optimal day-ahead target profile of the mean thermal energy contained in a large population of heaters, given various possible wind power production and uncontrollable load scenarios. This optimal profile is calculated to make the variable net demand as even as possible.

Performance evaluation of continuous solar still water desalination system

In this paper, the experimental study aims to enhance a distillate water productivity of solar stills. To achieve this objective, solar still with continuous water desalination along 24 h was designed, structured, and operated in the city of Tanta, Gharbia Governorate, Egypt. For the solar stills, the temperatures of the condensing surface are very low throughout the night and during the early hours of the morning. This advantage makes the uses of the solar stills with continuous desalination along 24 h to be more effective. To achieve the continuous water desalination, the electric water heater (EWH) was installed in the basin of solar still to heat the basin water in the night and during the early hours of the morning. The EWH is powered by solar batteries that are charged by PV panels during sunrise. The experimental results presented that the accumulated distillate water productivity for using the continuous water desalination along 24 h varied between 10,631 and 12,087 mL m−2 day−1 after period use of 2 May to 11 August. The improvement in accumulated productivity of solar still with continuous water desalination along 24 h varied between 159.3 and 177.9% as compared to solar still working without EWH. Also, the improvement in the overall efficiency of solar still with continuous water desalination varied between 27.9 and 31.3%.

Domestic hot water technology transition for solar thermal systems: An assessment for the urban areas of Maputo city, Mozambique

Solar thermal systems have been widely used to increase energy efficiency in residential sector, since it became one of the top priorities in many countries to mitigate the electricity shortage. Thus, for better deployment of solar thermal systems in the residential sector it is important to understand the household electricity consumption and energy usage for domestic hot water, though developing countries lack this type of accurate data.This work assesses a domestic hot water technology transition to solar thermal systems in the urban areas of developing countries, taking as case study Maputo city, in Mozambique.First, a survey was made to the domestic hot water needs, demand and usage, in 700 households, 28 neighbourhoods of Maputo, having identified the sources and technologies used to heat water and quantified the domestic hot water needs. Then, the impact on energy demand, cost and CO2 emissions of domestic hot water technology change to solar thermal systems was modelled as well as the impact on electricity grid.The survey results point that the predominant energy sources used for domestic hot water in urban areas are electricity and biomass with nearly 46% and 41% shares, respectively. Further, results show that the domestic hot water technology used depends on household income, being the electric water heaters mostly used in households with relatively high-income.The technology transition to solar thermal systems results in a positive impact on the grid by reducing up to 65.7% the domestic hot water electricity demand and 78.7% of the CO2 emissions, while the economic savings are up to 244 USD/household/year. However, peak load is expected to increase by 11%, suggesting the need for load management policy implementation.

Utilizing the flexibility of distributed thermal storage in solar power forecast error cost minimization

Intermittent renewable energy generation, which is determined by weather conditions, is increasing in power markets. The efficient integration of these energy sources calls for flexible participants in smart power grids. It has been acknowledged that a large, underutilized, flexible resource lies on the consumer side of electricity generation. Despite the recently increasing interest in demand flexibility, there is a gap in the literature concerning the incentives for consumers to offer their flexible energy to power markets. In this paper, we examine a virtual power plant concept, which simultaneously optimizes the response of controllable electric hot water heaters to solar power forecast error imbalances. Uncertainty is included in the optimization in terms of solar power day-ahead forecast errors and balancing power market conditions. We show that including solar power imbalance minimization in the target function changes the optimal hot water heating profile such that more electricity is used during the daytime. The virtual power plant operation decreases solar power imbalances by 5–10% and benefits the participating households by 4.0–7.5 € in extra savings annually. The results of this study indicate that with the number of participating households, while total profits increase, marginal revenues decrease.

A Novel Domestic Electric Water Heater Control Method

As one of important thermostatically controlled loads (TCLs), domestic electric water heaters (DEWHs) show considerable potential for utilities to shave peak load working with direct load control (DLC). The electricity consumption of DEWHs is high in regard to daily domestic electricity consumption, which shows the potential for peak shifting services through the direct control of DEWHs. In practice, off-control is commonly used to control DEWHs, and finding suitable DEWHs to turn off is the main objective of DLC. However, it is difficult to decide which DEWH can be turned off when end-user comfort is taken into consideration, especially with the absence of temperature measurement information. In this paper, a novel control method is proposed to control DEWHs without temperature information. A time-varied weight matrix is generated based on patterns of DEWHs, and the temperatures of DEWHs can be estimated by the weight matrix and their states. The weight matrix and heating durations are used to generate a customer satisfaction prediction index, which can be used as a reference during DLC. The index can be used to select suitable DEWHs to turn off or to turn back on to maintain end-user comfort. The proposed method only needs the on-off states of DEWHs, which are available in practice. Simulation results prove that the proposed method can work well to reduce peak demand without affecting end-user comfort.

Fuzzy Based Particle Swarm Optimization for Modeling Home Appliances Towards Energy Saving and Cost Reduction Under Demand Response Consideration

Recently, homes consume around 40% of world power and produce 21% of the total greenhouse gas emissions. Thus, the proper management of energy in the domestic sector is a vital element for creating a sustainable environment and cost reduction. In this study, an intelligent home energy management system (HEMS) is developed to control domestic appliances load. The motivation of this work is reduced the electricity cost and power consumption from all the appliances by maintaining the customer’s high comfort level using an efficient optimized controller. The domestic household appliances such as heating ventilation and air conditioning (HVAC), electric water heater (EWH) and lighting were modelled and analysed using Simulink/Matlab. The developed models analysed the appliances’ energy consumption and cost sceneries during peak, off-peak and both peak and off-peak hours. Fuzzy logic controller (FLC) was developed for the HEMS to perform energy utilization estimation and cost analysis during these periods taking the Malaysian tariff for domestic use into consideration. To improve the FLC outcomes and the membership function constraint, particle swarm optimization (PSO) is developed to ensure an optimal cost and power consumption. The results showed that the developed FLC controller minimized the cost and energy consumption for peak period by 19.72% and 20.34%, 26.71% and 26.67%, 37.5% and 33.33% for HVAC, EWH, and dimmable lamps, respectively. To validate the optimal performance, the obtained results shows that the FLC-PSO can control the home appliances more significantly compared to FLC only. In this regard, the FLC-PSO based optimum scheduled controller for the HEMS minimized power and cost by 36.17%-36.54%, 54.54%-55.76%, and 62.5%-58% per day for HVAC, EWH, and light, respectively. In sum, the PSO shows good performance to reduce the cost and power consumption toward efficient HEMS. Thus, the developed fuzzy-based heuristic optimized controller of HEMS is beneficial towards sustainable energy utilization.

Environmental and Health Impacts of Domestic Hot Water (DHW) Boilers in Urban Areas: A Case Study from Turin, NW Italy

Domestic hot water heat pumps (DHW HPs) have spread fast in recent years in Europe and they now represent an interesting opportunity for implementing renewable energy sources in buildings with a centralized/district heating system, where DWH is generally produced by a gas boiler or an electric water heater. Replacing these appliances has several environmental benefits, including the removal of air pollution sources and the reduction of Green House Gasses (GHG) emissions. In this work, we present the techno-economic and environmental evaluation of implementing DHW HPs in Turin, where 66% of the DHW demand is covered by dedicated gas boilers. The impact of such boilers was assessed through numerical air dispersion modeling conducted with the software SPRAY (Aria Technologies, Paris, French). Results show that removing these sources would reduce yearly average concentrations of NOx up to 1.4 µg/m3, i.e., about 1% of monitored concentrations of NOx, with a benefit of 1.05 ÷ 15.15 M€/y of avoided health externalities. Replacing boilers with DHW HPs is always financially feasible with current incentives while, in their absence, it would be convenient for residential units with 3 cohabitants or more (51.22% of the total population), thanks to scale economies.

Resource Study of Large-Scale Electric Water Heater Aggregation

Residential-scale distributed energy assets, like residential electric water heaters, individually present a negligible load to the power grid. When aggregated, however, these assets can impart significant effects within a balancing area; they may be dispatched en masse to provide grid services. An aggregation of water heaters may be controlled to assume generator-like functions with the ability to effectively “decrement power” through dispatch of load. This resource study examines the capabilities of a 10,000 unit water heater aggregation by subjecting the aggregate to dispatch requests of various size and duration, then analyzing how the aggregate responds to and recovers from these requests. Results show that a large-scale aggregation of electric water heaters may effectively decrement power on the scale of megawatts when the dispatch request size and duration are appropriately considered.

An optimization methodology for self-consumption of residential photovoltaic energy

This paper considers the optimization of the self-consumed power locally produced by residential photovoltaic panels. We focus on a simplified set-up where only the Electric Water Heater (EWH) is regulated, while the rest of the appliances represents an uncontrollable load. We formulate an unconstrained optimization problem by inverting the EWH dynamics and prove that the corresponding objective function is continuously differentiable. Thanks to an explicit characterization of its critical points, we propose a tailored and computationally efficient optimization algorithm. Simulations performed in Dymola over a one-year time horizon allow us to demonstrate the merits and performances of the proposed method.

Greenhouse gas emission estimations for Depok’s (West Java, Indonesia) middle-class household water end-uses

The rising concentration of greenhouse gases (GHG) is highly associated with climate change. Previous studies showed that end-use household water consumption contributes 58% of the total GHG emissions from the water sector. We attempted to calculate the GHG emissions associated with household water end-uses from an area that uses groundwater as the main water source. Data were collected from 100 households in the Cinere subdistrict of Depok, West Java. Questionnaire surveys and interviews were conducted to obtain data related to each type of water end-use consumption and energy consumption from water appliance usage. Existing GHG emissions were calculated based on the water and energy consumption data. The results showed that the average end-use household water consumption for the study area was 214.3 liters per capita per day. The GHG emission associated with household water end-uses was found to be 0.379 kg CO2 per capita per day and mainly resulted from water heating. Two intervention scenarios to minimize GHG emissions were evaluated. The first scenario—retrofitting water-related appliances and exhibiting water-conscious behavior—could reduce GHG emissions by 1%, whereas the second scenario—replacing electric and gas water heaters to solar water heaters—could reduce emissions by 66%.

Application of Modelling and Statistical Inferences To Compare Performance of Hot Water Heating Devices in the Residence of University Campus

Implementation of an energy efficiency intervention in a university campus can resulted in both energy and electricity cost saving. The study focused on retrofitting a 12 kW electric boiler of 1000 L tank with a 4.0 kW air source heat pump (ASHP) unit. A data acquisition system was built to monitor the performance of the electric boiler before intervention and the ASHP water heater after implementation. The results depicted that the average daily electrical energy and hot water consumed during the summer season with the utilization of the electric boiler and the ASHP water heater were 132.53 kWh and 1836 L, and 37.52 kWh and 1818.2 L, respectively. Wilcoxon rank sum test was employed to compare both the daily volume of hot water and electrical energy consumed for both winter and summer seasons by the electric boiler and the ASHP water heater. Linear regression models of the electrical energy consumed as function of volume of hot water consumed, per day for both hot water heating devices was established. The models’ determination coefficients and the root mean square errors of the electric boiler and ASHP water heaters was 0.960 and 1.33, and 0.970 and 0.23 for summer and 0.970 and 0.21, and 0.980 and 0.08, for winter seasons. All four models gave very good predictions with the measured experimental values.