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

Michael J. Ritchie, Jacobus A.A. Engelbrecht and Marthinus J. Booysen
Additional contact information
Michael J. Ritchie: Electrical and Electronic Engineering, Stellenbosch University, Stellenbosch 7600, South Africa
Jacobus A.A. Engelbrecht: Electrical and Electronic Engineering, Stellenbosch University, Stellenbosch 7600, South Africa
Marthinus J. Booysen: Electrical and Electronic Engineering, Stellenbosch University, Stellenbosch 7600, South Africa

Energies, 2021, vol. 14, issue 7, 1-23

Abstract: 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.

Keywords: domestic energy saving; electric water heater; energy usage prediction; Legionella; optimal control; scheduled control; water heater temperature control (search for similar items in EconPapers)
JEL-codes: Q Q0 Q4 Q40 Q41 Q42 Q43 Q47 Q48 Q49 (search for similar items in EconPapers)
Date: 2021
References: View references in EconPapers View complete reference list from CitEc
Citations: View citations in EconPapers (4)

Downloads: (external link)
https://www.mdpi.com/1996-1073/14/7/1963/pdf (application/pdf)
https://www.mdpi.com/1996-1073/14/7/1963/ (text/html)

Related works:
This item may be available elsewhere in EconPapers: Search for items with the same title.

Export reference: BibTeX RIS (EndNote, ProCite, RefMan) HTML/Text

Persistent link: https://EconPapers.repec.org/RePEc:gam:jeners:v:14:y:2021:i:7:p:1963-:d:528846

Access Statistics for this article

Energies is currently edited by Ms. Agatha Cao

More articles in Energies from MDPI
Bibliographic data for series maintained by MDPI Indexing Manager ().