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 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 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 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.

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.

Heat Pump Water Heater Control Strategy Optimization for Cold Climates

2015 ◽  
Author(s):  
Jayson Bursill ◽  
Cynthia A. Cruickshank
Keyword(s):  
Heat Pump ◽  
Control Strategy ◽  
Control Strategies ◽  
Thermal Storage ◽  
Hot Water ◽  
Space Heating ◽  
Cold Climates ◽  
Water Heater ◽  
Water Heaters ◽  
Surrounding Space

Commercially available heat pump water heaters (HPWH) have been used successfully in warm humid climates (southern United States), and recently, have been proven effective in replacing electric water heater technology in cooler climates within Canada. Using an air source HPWH unit within a dwelling can yield electrical coefficients of performance that are indicative of significant energy savings, but can also add an additional load to the space heating system. Current control strategies do not attempt to mitigate the heating load added to the surrounding space, and only consider the water temperature in the tank. This is because, to date, the primary application has been in sub-tropical climates where cooling is frequently beneficial. Starting in 2015, the US Department of Energy is mandating that all electric water heaters have an energy factor (unit of heat applied to hot water per unit of energy applied to the system) greater than 2, which makes technologies that utilize electrical coefficients of performance, such as HPWH technology, mandatory. To ease the inevitable transition to heat pump water heaters in lieu of electric water heaters, modified control strategies that highlight using thermal storage to reduce space heating loads must be implemented. This paper presents a study which was conducted to evaluate the performance of a commercially available HPWH with modified controls. The HPWH is first characterized experimentally under a series of different thermal conditions and draw parameters. The test tank contains a 1500 W electric auxiliary heater that provides on demand heat to the top 0.30 m (1 ft) of the tank, and a wraparound heating coil. An air source heat pump, using R-134A as the refrigerant, draws air from, and returns air to the surrounding space and provides heating to the whole tank through the coil. The tank has been tested using Canadian Standards Association draw profiles to characterize performance under different hot water demands. Electricity consumption and thermal flux is measured for each vertical tank section, and various performance metrics are calculated using energy balances. A TRNSYS model is then calibrated to the experimental data to allow for the flexibility of varying multiple parameters over various climates. Using this calibrated TRNSYS model, an optimal control strategy and tank set-points can be determined for use in cold climates. As expected from previous work, there is a decrease in performance of the heat pump when heating the tank to higher temperatures to facilitate thermal storage, but the benefits from taking advantage of shifting electrical demand (of water heating) to space heating demand can outweigh the loss of performance.

scholarly journals Variable Refrigerant Flow (VRF) System for Space Heating: A Case Study of Resort

2018 ◽  
Vol 14 (1) ◽  
pp. 1-13
Author(s):  
Tri Ratna Bajracharyaa ◽  
Rabindra Nath Bhattaraiai ◽  
Sarika Kumari Mishra ◽  
Ashesh Babu Timilsina
Keyword(s):  
Energy Consumption ◽  
Urban Areas ◽  
Financial Analysis ◽  
Electrical Energy ◽  
Heating System ◽  
Hot Water ◽  
Space Heating ◽  
Water Heater ◽  
Alternative Means ◽  
Solar Powered

 The need of thermal comfort is one of the major topic of energy consumption in building. Alternative means for space heating are required for reducing building energy consumption and also reduce its carbon footprint. Solar thermal systems are matured technology in field of hot water and space heating. Though solar water heater has flourished in Nepal, space heating system is less popular. With an objective to assess the less popularity of such system in Nepal, financial comparison of solar underfloor heating system against commonly used VRF system designed to meet heating requirements of a particular site is done. The selected site is a resort in Nagarkot, Nepal. The selected site has minimum temperature of 3 ºC which is to be maintained at 20 ºC of which the total heating load is 10.527 kW. From the financial analysis, it is seen that though installation cost of solar powered system is more, in long run it turns out to be economic and in this case the system is technically and financially viable. For solar underfloor heating, the levelized cost of energy when subsidized with 3.5 % interest rate is NRs. 13.18 which is slightly more than current rate of electrical energy. The solar powered heating system has very high footprint because of which this type of system is less employed in urban areas and high rise buildings.Journal of the Institute of Engineering, 2018, 14(1): 1-13

SIMULATED PERFORMANCE OF A COMBINED RADIANT FLOOR HEATING AND DOMESTIC HOT WATER SUPPLY SYSTEM UNDER DIFFERENT CONTROL STRATEGIES

2013 ◽  
Vol 21 (02) ◽  
pp. 1350011 ◽  
Author(s):  
L. LI ◽  
M. ZAHEERUDDIN ◽  
SUNG-HWAN CHO ◽  
SEONG-KI HONG
Keyword(s):  
Optimal Control ◽  
Energy Consumption ◽  
Water Supply ◽  
Control Strategy ◽  
Control Strategies ◽  
Hot Water ◽  
Domestic Hot Water ◽  
Hot Water Supply ◽  
Radiant Floor Heating ◽  
Floor Heating

A dynamic model of a combined radiant floor heating (RFH) and domestic hot water supply (DHWS) system is developed and validated by using measured data gathered from an experimental test facility. The validated model was used to study the dynamic responses of the system under different operating conditions. Optimal control and predictive control strategies were designed and simulated to study system performance and energy consumption. Results showed that the control strategy with the heating load prediction could save up to 12.7% energy. Also, the optimal control strategy with optimal set-points could save 8.6% energy input to the boiler and 42.9% pump energy consumption while maintaining the zone temperatures and DHWS temperatures close to their respective set-points.

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

Energy Consumption Modeling of a Heat Pump System for Combined Space Conditioning and Residential Water Heating in a Typical Household in Quito, Ecuador

2016 ◽  
Author(s):  
Gabriel Agila ◽  
Guillermo Soriano
Keyword(s):  
Energy Consumption ◽  
Heat Pump ◽  
Thermal Storage ◽  
Hot Water ◽  
Water Heating ◽  
Water Heater ◽  
Pump System ◽  
Detailed Model ◽  
Heat Pump Water Heater ◽  
Residential Water

This research develops a detailed model for a Water to Water Heat Pump Water Heater (HPWH), operating for heating and cooling simultaneously, using two water storage tanks as thermal deposits. The primary function of the system is to produce useful heat for domestic hot water services according to the thermal requirements for an average household (two adults and one child) in the city of Quito, Ecuador. The purpose of the project is to analyze the technical and economic feasibility of implementing thermal storage and heat pump technology to provide efficient thermal services and reduce energy consumption; as well as environmental impacts associated with conventional systems for residential water heating. An energy simulation using TRNSYS 17 is carried to evaluate model operation for one year. The purpose of the simulation is to assess and quantifies the performance, energy consumption and potential savings of integrating heat pump systems with thermal energy storage technology, as well as determines the main parameter affecting the efficiency of the system. Finally, a comparative analysis based on annual energy consumption for different ways to produce hot water is conducted. Five alternatives were examined: (1) electric storage water heater; (2) gas fired water heater; (3) solar water heater; (4) air source heat pump water heater; and (5) a heat pump water heater integrated with thermal storage.

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.

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