scholarly journals Comfort, peak load and energy: Centralised control of water heaters for demand-driven prioritisation

2019 ◽  
Author(s):  
Marcel Roux ◽  
Mark Apperley ◽  
MJ Booysen
Keyword(s):  
Smart Grid ◽  
Peak Load ◽  
Hot Water ◽  
Domestic Water ◽  
Water Heaters ◽  
Usage Patterns ◽  
Grid Load ◽  
Temperature Levels ◽  
Load Limits ◽  
Ripple Control

Recent advances in smart grid technology enable new approaches to address the problem of load control for domestic water heating. Since water heaters store energy, they are well-suited to load management. However, existing approaches have focused on the electrical supply side, ignoring the obvious link between the user and the grid: individual hot water consumption patterns. This paper proposes a load spreading approach in which water heaters compete for access to the heating medium. The proposed smart grid solution takes grid load limits, real-time temperature measurements, water usage patterns, individual user comfort, and heater meta-data into consideration. The scheduler only turns on the heaters with the highest level of need, but limits the number of on heaters to ensure that the grid load stays below a set limit for a set time. The method is evaluated by simulation against various heater set temperature levels, and for various load limits, and compared with ripple control and actual consumption measured in a field trial of 34 water heaters. The proposed algorithm reduces the load from 62kW to 20, 30, 40, and 50kW (vs. 106kW for full ripple control). The resulting number of unwanted cold events is fewer than for ripple control, and only slightly more than no control, while reducing the total energy by 14% from a user-optimised natural experiment.

The Thermal Performance of Residential Electric Water Heaters Subjected to Various Off-Peak Schedules

1996 ◽  
Vol 118 (2) ◽  
pp. 73-80 ◽  
Author(s):  
A. H. Fanney ◽  
B. P. Dougherty
Keyword(s):  
Thermal Efficiency ◽  
Laboratory Tests ◽  
Test Procedure ◽  
Hot Water ◽  
Department Of Energy ◽  
Water Heater ◽  
Domestic Water ◽  
Peak Period ◽  
Water Heaters ◽  
Solar Water Heaters

An increasing number of utilities control the supply of power to residential water heaters as one means of reducing peak electrical demand. Water heaters operated in this manner are referred to as off-peak water heaters. Several utilities are also considering the use of solar domestic water heaters as an additional means of limiting power demand during times of greatest electrical usage. The research described within this paper quantifies the variation in thermal efficiency attributable to subjecting residential electrical water heaters to various off-peak and water removal schedules and, thus, forms a basis of comparison to which the thermal efficiency of solar water heaters or other water heating technologies may be compared. Laboratory tests, where the off-peak period and hot water draw schedule were varied, were conducted on two residential storage water heaters. A computer model of an electric water heater was developed and validated. The laboratory tests and the model were used to quantify the effect that various off-peak and hot water draw schedules have on water heater thermal efficiency. Thermal efficiency was found to vary up to seven percent for water heaters which meet the present minimum efficiency standards as specified within the National Appliance Energy Conservation Act. The energy factor, as measured using the Department of Energy Test Procedure for Water Heaters, is shown to be independent of the off-peak schedule because of a “normalizing” that occurs as part of the calculation procedure.

Solving Design Problems for Cathodic Protection of Glass-Lined Domestic Water Heaters

CORROSION ◽  
1960 ◽  
Vol 16 (9) ◽  
pp. 9-17
Author(s):  
H. C. Fischer
Keyword(s):  
Cathodic Protection ◽  
Hot Water ◽  
Test Results ◽  
Domestic Water ◽  
Design Data ◽  
Design Problems ◽  
Water Heaters ◽  
Protection Systems ◽  
Current Densities ◽  
Cathodic Protection System

Abstract Factors important in designing” a cathodic protection system for glass lined domestic hot water heaters are considered. Method by which bare areas of single coated glass lined tanks can be calculated is explained, and comparisons are made between calculated values and those obtained by tests on tanks under protection. Instruments for making these tests and techniques are illustrated and described. Design data relevant to required current densities are considered with respect to platinum clad tantalum and platinum plated titanium anodes. Regulations of Underwriters’ Laboratories concerning accumulated gas from cathodic protection systems are weighed against test results and the volume of gas actually produced is measured and analyzed. Design criteria and details for rectified current used in systems applied to electrically heated tanks are given. Details of a thermoelectric generator for use with gas fired tanks are given. This generator produces sufficient current to protect a well-lined tank in the highest resistivity water likely to be encountered. 5.2.3

scholarly journals Centrally adapted optimal control of multiple electric water heaters

2021 ◽  
Author(s):  
Michael Ritchie ◽  
J.A.A. Engelbrecht ◽  
MJ Booysen
Keyword(s):  
Optimal Control ◽  
Control Strategies ◽  
Management Strategies ◽  
Peak Load ◽  
Hot Water ◽  
Storage Devices ◽  
Improve Energy Efficiency ◽  
Water Heaters ◽  
Generation Capacity ◽  
Matching Strategy

Breakthroughs in smart grid technology make it possible to deliver electricity in controlled and intelligent ways to improve energy efficiency between the user and the utility. Demand-side management strategies can reduce overall energy usage and shift consumption to reduce peak loads. Electric water heaters account for 40% of residential energy consumption. Since they are thermal storage devices, advanced control strategies can improve their efficiency. But existing methods disregard the connection between the user and the grid. We propose a centrally adapted control model that allows for coordinated scheduling to adapt the optimal control schedule of each EWH, spreading the load into off-peak periods to ensure that the grid's generation capacity is not exceeded. We consider two strategies for the delivery of hot water, temperature matching, and energy matching with \textit{Legionella} sterilisation, and compare them to a baseline strategy where the thermostat is always switched on. Simulation results for a grid of 77 EWHs showed that an unconstrained peak load of 1.05 kW/EWH can be reduced as low as 0.4 kW/EWH and achieve a median energy saving per EWH of 0.38 kWh/day for the temperature matching strategy and 0.64 kWh/day for the energy matching strategy, without reducing the user's comfort.

scholarly journals How much energy can optimal control of domestic water heating save?

2019 ◽  
Author(s):  
MJ Booysen ◽  
J.A.A. Engelbrecht ◽  
Michael Ritchie ◽  
Mark Apperley ◽  
Andrew Cloete
Keyword(s):  
Optimal Control ◽  
Fossil Fuels ◽  
Energy Use ◽  
Hot Water ◽  
Water Usage ◽  
Water Heating ◽  
Domestic Water ◽  
Water Heaters ◽  
Point Of Use ◽  
The Impact

Scheduled control of domestic electric water heaters, designed to cut energy use while minimising the impact on users' comfort and convenience, has been fairly common for some time in a number of countries. The aim is usually load-shifting (by heating water at off-peak times) and/or maximising time-of-use pricing benefits for users. The scheduling tends not to be linked to actual hot water usage and depends largely on stored thermal energy. Heat losses therefore tend to be greater than if the heater ran without a break. The effect of such a control strategy is thus to worsen the energy loss and in most cases increase greenhouse gas emissions. Many developing countries have flat-pricing (no time-of-use incentives) and rely heavily on energy from fossil fuels, making these considerations even more pressing. We explore three strategies for optimal control of domestic water heating that do not use thermostat control: matching the delivery temperature in the hot water, matching the energy delivered in the hot water, and a variation of the second strategy which provides for Legionella sterilisation. For each of these strategies we examine the energy used in heating, the energy delivered at the tank outlet, and issues of convenience to the user. The study differs from most previous work in that it uses real daily hot-water usage profiles, ensures like-for-like comparison in delivered energy at the point of use, and includes a daily Legionella avoidance strategy. We tackled this as an optimal control problem using dynamic programming. Our results demonstrate a median energy saving of between 8\ and 18% for the three strategies. Even more savings would be realised if intended and unintended usage events are correctly classified, and the optimal control only plans for intended usage events.

scholarly journals Characterization of interaction between electric vehicles and smart grid

2021 ◽  
Vol 237 ◽  
pp. 02004
Author(s):  
Yan Zhang ◽  
Yongxiu He ◽  
Fengyu Su ◽  
Xiaoqing Wang ◽  
Diling Zhang
Keyword(s):  
Smart Grid ◽  
Electric Vehicles ◽  
Economic Benefit ◽  
Power Grid ◽  
Peak Load ◽  
Fluctuation Effect ◽  
Load Shifting ◽  
Significant Fluctuation ◽  
Grid Load

With the development of smart distribution technology in the future, electric vehicle users can not only charge reasonably based on peak-valley price, they can also discharge electricity into the power grid to realize their economic benefit when it’s necessary and thus promote peak load shifting. According to the characteristic that future electric vehicles can discharge, this paper studies the interactive characteristics between electric vehicles and smart grid. In this paper, the example shows that the charging and discharging behaviour of EV users will bring significant fluctuation effect to the power grid load, and the reasonable TOU strategy can stimulate EV users to conduct reasonable charging and discharging, so as to smooth the peak and valley difference of some power grid.

Virtual test bench for the design of control strategies for water heaters

2021 ◽  
pp. 1-36
Author(s):  
André Quintã ◽  
Jonathan Oliveira ◽  
Jorge Ferreira ◽  
Vítor Costa ◽  
Nelson Martins
Keyword(s):  
Test Bench ◽  
Control Strategies ◽  
Heat Pumps ◽  
Open Loop ◽  
Hot Water ◽  
Hardware In The Loop ◽  
Water Heater ◽  
Domestic Water ◽  
Virtual Test ◽  
Water Heaters

Abstract An innovative methodology and a virtual test bench are proposed to support the design of water heaters' control strategies. This platform allows to speed up the development and evaluation of control systems even before the existence of prototypes or real test environments. By simulating the environmental conditions and the state of the different device components, it will be possible to detect and correct possible initial errors in the control system design which can be time consuming and costly due to subsequent modifications to the system or equipment components. The architecture of the proposed system establishes four operating modes, open loop data acquisition, real time simulation, hardware-in-the-loop simulation, and test of the complete real system, the incorporation of these functionalities in the same platform is not reported in the literature for domestic water heaters. The virtual test bench was designed to accommodate different water heaters including, but not limited to, gas, electric and heat pumps, for instantaneous hot water production or including hot water storage. The prototype of the virtual test bench is described emphasizing the hardware-in-the-loop methodologies and embedded control. The particular case study of a tankless gas water heater is presented implementing the different operation modes in the virtual test bench. The water heater models, control strategies, simulation and experimental data are presented and discussed.

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