scholarly journals Practically-Achievable Energy Savings with the Optimal Control of Stratified Water Heaters with Predicted Usage

Energies ◽  
2021 ◽  
Vol 14 (7) ◽  
pp. 1963
Author(s):  
Michael J. Ritchie ◽  
Jacobus A.A. Engelbrecht ◽  
Marthinus J. Booysen
Keyword(s):  
Optimal Control ◽  
Fossil Fuels ◽  
Energy Savings ◽  
Electrical Energy ◽  
Hot Water ◽  
Prediction Errors ◽  
Water Usage ◽  
Energy Usage ◽  
Water Heaters ◽  
The Ideal

Residential water heaters use a substantial amount of electrical energy and contribute to 25% of the energy usage in the residential sector. This raises concern for users in countries with flat rate electricity fees and where fossil fuels are used for electricity generation. Demand side management of tanked water heaters is well suited for energy-focused load reduction strategies. We propose a strategy for providing an electric water heater (EWH) with the optimal temperature planning to reduce the overall electrical energy usage while satisfying the comfort of the user. A probabilistic hot water usage model is used to predict the hot water usage behaviour for the A*-based optimisation algorithm, which accounts for water stratification in the tank. A temperature feedback controller with novel temperature and energy-correcting capabilities provides robustness to prediction errors. Three optimal control strategies are presented and compared to a baseline strategy with the thermostat always on: The first ensures temperature-matched water usages, the second ensures energy-matched water usages, and the third is a variation of the second that provides Legionella prevention. Results were obtained for 77 water heaters, each one simulated for four weeks. The median energy savings for predicted usage were 2.2% for the temperature-matched strategy, and 9.6% for both of the energy-matched strategies. We also compare the practical energy savings to the ideal scenario where the optimal scheduling has perfect foreknowledge of hot water usages, and the temperature and energy-matched strategies had a 4.1 and 11.0 percentage point decrease from the ideal energy savings.

scholarly journals Optimal schedule and temperature control of stratified water heaters

2021 ◽  
Author(s):  
J.A.A. Engelbrecht ◽  
MJ Ritchie ◽  
MJ Booysen
Keyword(s):  
Optimal Control ◽  
Energy Consumption ◽  
Search Algorithm ◽  
Control Strategies ◽  
Optimal Schedule ◽  
Electrical Energy ◽  
Hot Water ◽  
Energy Usage ◽  
Water Heater ◽  
Water Heaters

Water heating is a major component of domestic electrical energy usage, in some countries contributing to 25% of the residential sector energy consumption. Demand response strategies can reduce the time-of-use costs and overall electrical energy consumption. We present a method to reduce the electrical energy usage itself. Our novel heating schedule control minimises the electric water heater's energy usage without compromising user convenience. We achieve optimal control, while taking into account the natural temperature stratification of the water in the tank, using the A* search algorithm. Since previous research assumes a one-node thermal model, we also assess the effect of excluding stratification. We match three optimal control strategies to a baseline: the standard "always on'" thermostat control. The first two strategies respectively match the temperature and the energy of the hot water supplied by the water heater. The third, a variation on the second, includes a method of preventing the growth of Legionella bacteria. We tested 77 water heaters over four weeks, a week for each season, and all three strategies saved energy. The median savings were 6.3% for temperature-matching, 21.9% for energy-matching and 16.2% for energy-matching with Legionella prevention. Taking stratification into account increased these savings by 1.2%, 5.4% and 5.5% respectively.

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 Which Strategy Saves the Most Energy for Stratified Water Heaters?

Energies ◽  
2021 ◽  
Vol 14 (16) ◽  
pp. 4859
Author(s):  
Michael J. Ritchie ◽  
Jacobus A. A. Engelbrecht ◽  
M. J. (Thinus) Booysen
Keyword(s):  
Energy Supply ◽  
Energy Demand ◽  
Energy Savings ◽  
Electricity Consumption ◽  
Hot Water ◽  
Water Usage ◽  
Point Temperature ◽  
Water Heaters ◽  
Heating Schedule ◽  
Reducing Energy

The operation of water heating uses a substantial amount of energy and is responsible for 30% of a household’s overall electricity consumption. Determining methods of reducing energy demand is crucial for countries such as South Africa, where energy supply is almost exclusively electrical, 88% of it is generated by coal, and energy deficits cause frequent blackouts. Decreasing the energy consumption of tanked water heaters can be achieved by reducing the standing losses and thermal energy of the hot water used. In this paper, we evaluate various energy-saving strategies that have commonly been used and determine which strategy is best. These strategies include optimising the heating schedule, lowering the set-point temperature, reducing the volume of hot water used, and installing additional thermal insulation. The results show that the best strategy was providing optimal control of the heating element, and savings of 16.3% were achieved. This study also determined that the magnitude of energy savings is heavily dependent on a household’s water usage intensity and seasonality.

scholarly journals Impact of node count on energy-optimal control of stratified vertical water heaters in smart grid applications

2021 ◽  
Author(s):  
MJ Ritchie ◽  
J.A.A. Engelbrecht ◽  
MJ Booysen
Keyword(s):  
Optimal Control ◽  
Energy Savings ◽  
Variable Number ◽  
Hot Water ◽  
Water Heater ◽  
Total Energy Consumption ◽  
Water Heaters ◽  
Greenhouse Gases Emissions ◽  
Four Seasons ◽  
Grid Applications

The energy requirements for an Electric Water Heater (EWH) accounts for 40% of a household's total energy consumption and 30% of greenhouse gases emissions. The flexibility of the device to store thermal energy for long periods highlights how the intensity of the grid demand can be alleviated by implementing demand-side management (DSM) strategies. In this paper, we evaluate energy savings that can be achieved by modelling the EWH as a variable number of multiple nodes and providing it with optimal control with perfect foreknowledge of the hot water usage profile. We simulated 77 household's for all four seasons and determined that an average daily energy saving of 6.2% for temperature-matching and 16.3% for energy-matching can be achieved for a 20-node EWH. We also evaluated how increasing the number of nodes of the EWH when determining the optimal planning affects energy savings. It was concluded that using more than four nodes produced diminishing returns.

scholarly journals AUDIT ENERGI PADA SEBUAH HOTEL

2012 ◽  
Vol 16 (3) ◽  
pp. 131
Author(s):  
Didik Ariwibowo
Keyword(s):  
Energy Consumption ◽  
Air Conditioning ◽  
Energy Savings ◽  
Electric Energy ◽  
Electrical Energy ◽  
Hot Water ◽  
Electrical Energy Consumption ◽  
Energy Audit ◽  
Electric Energy Consumption ◽  
Pumping System

Didik Ariwibowo, in this paper explain that energy audit activities conducted through several phases, namely: the initial audit, detailed audit, analysis of energy savings opportunities, and the proposed energy savings. Total energy consumed consists of electrical energy, fuel, and materials in this case is water. Electrical energy consumption data obtained from payment of electricity accounts for a year while consumption of fuel and water obtained from the payment of material procurement. From the calculation data, IKE hotels accounted for 420.867 kWh/m2.tahun, while the IKE standards for the hotel is 300 kWh/m2.tahun. Thus, IKE hotel included categorized wasteful in energy usage. The largest energy consumption on electric energy consumption. Largest electric energy consumption is on the air conditioning (AC-air conditioning) that is equal to 71.3%, and lighting and electrical equipment at 27.28%, and hot water supply system by 4.44%. Electrical energy consumption in AC looks very big. Ministry of Energy and Mineral Resources of the statutes, the profile of energy use by air conditioning at the hotel by 48.5%. With these considerations in the AC target for audit detail as the next phase of activity. The results of a detailed audit analysis to find an air conditioning system energy savings opportunities in pumping systems. Recommendations on these savings is the integration of automation on the pumping system and fan coil units (FCU). The principle of energy conservation in the pumping system is by installing variable speed drives (VSD) pump drive motor to adjust speed according to load on the FCU. Load variations FCU provide input on the VSD pumps to match. Adaptation is predicted pump can save electricity consumption up to 65.7%. Keywords: energy audit, IKE, AC

scholarly journals Assessment and Modeling of Household-Scale Solar Water Heater Application in Zambia: Technical, Environmental, and Energy Analysis

2021 ◽  
Vol 2021 ◽  
pp. 1-13
Author(s):  
Mehdi Jahangiri ◽  
Esther T. Akinlabi ◽  
Sam M. Sichilalu
Keyword(s):  
Fossil Fuels ◽  
Hot Water ◽  
Climate Data ◽  
Ghg Emission ◽  
Water Heater ◽  
Ghg Mitigation ◽  
Solar Water ◽  
Water Heaters ◽  
Industrial Sectors ◽  
Solar Water Heaters

Solar water heaters (SWHs) are one of the most effective plans for general and easy use of solar energy to supply hot water in domestic and industrial sectors. This paper gives the first-ever attempts to assess the optimal localization of SWHs across 22 major cities in Zambia, as well as determine the possibility of hot water generation and model the greenhouse gas (GHG) emission saving. The climate data used is extracted by using the MeteoSyn software which is modeled in TSOL™. Results show the high potential of GHG emission reduction due to nonconsumption of fossil fuels owing to the deployment of SWHs, and three cities Kabwe, Chipata, and Mbala had the highest GHG mitigation by 1552.97 kg/y, 1394.8 kg/y, and 1321.39 kg/y, respectively. On average, SWHs provide 62.47% of space heating and 96.05% of the sanitary hot water requirement of consumers. The findings have shown the potential for the deployment of SWHs in Zambia. The techno-enviro study in this paper can be used by the policymakers of Zambia and countries with similar climates.

scholarly journals Non-Invasive Estimation of Domestic Hot Water Usage with Temperature and Vibration Sensors

2019 ◽  
Author(s):  
MJ Booysen
Keyword(s):  
Water Flow ◽  
Flow Rate ◽  
Water Consumption ◽  
Flow Measurement ◽  
Hot Water ◽  
Water Usage ◽  
Flow Rates ◽  
Domestic Hot Water ◽  
Non Invasive ◽  
Water Heaters

Electric water heaters are responsible for a large portion of electricity consumption and water usage in the domestic sector. Smart water heaters alleviate the strain on the electricity supply grid and reduce water consumption through behavioural change, but the installation of in-line flow meters is inconvenient and expensive. A non-invasive water flow meter is proposed as an alternative. Non-invasive flow measurement is more common for high flow rates in the industrial sector than for domestic applications. Various non-invasive water measurement methods are investigated in the context of domestic hot water, and a combination of thermal- and vibration-sensing is proposed. The proposed solution uses inexpensive, easily installable, non-invasive sensors and a novel algorithm to provide the same flow measurement accuracy as existing in-line meters. The algorithm detects the beginning and end of water consumption events with an accuracy of 95.6%. Quantitative flow rate estimation was possible for flow rates greater than 5 L min⁻¹ with an accuracy of 89%, while volumetric usage estimation had an accuracy of more than 93%. The algorithm limitations were applied to field data, revealing that water consumption could be detected with an error of less than 12% within the limitations of the proposed algorithm. The paper presents a successful proof of concept for a non-invasive alternative to domestic hot water flow rate measurement.

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 Building hvac retrofitting using a pv assisted dc heat pump coupled with a pcm heat battery and optimal control algorithm

2019 ◽  
Vol 111 ◽  
pp. 04041 ◽  
Author(s):  
Ettore Zanetti ◽  
Rossano Scoccia ◽  
Marcello Aprile ◽  
Mario Motta ◽  
Livio Mazzarella ◽  
...  
Keyword(s):  
Optimal Control ◽  
Heat Pump ◽  
Control Algorithm ◽  
Energy Savings ◽  
Residential Building ◽  
Hot Water ◽  
Photovoltaic System ◽  
Case Scenario ◽  
Dynamic Simulations

In the last years, the EU and scientific community put a lot of effort in trying to increase the sustainability in renovated buildings by introducing novel concepts and technologies. This paper presents the outcomes of a retrofit case study carried out within the Heat4Cool H2020 project concerning space heating (SH) and domestic hot water (DHW) systems. The case study is a multi-family residential building located in Chorzow, Poland, where the SH and DHW are provided by natural gas boilers present in each apartment. The proposed approach is to combine the existing gas boilers with phase change material storages (PCM) and a direct current air source heat pump (DC-EHP) assisted by a photovoltaic system (PV) connected to the grid. TRNSYS was used for the dynamic simulations, and to support the introduction of the retrofit layout. New custom TRNSYS’ types were developed for each technology and tested against experimental data provided by industrial partners. Furthermore, a state-of-the-art rule-based controller was developed combining TRNSYS with a MATLAB’s script and tested against an interior point optimal control algorithm. In the best-case scenario the yearly primary energy savings are more than 30% accounting for the PV energy sold to the grid and around 11% considering only self-consumption, while the pay-back time is around 10 years considering EU28 economic conditions and 20% overall discount for the renovation project.

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