The difference between energy consumption and energy cost: Modelling energy tariff structures for water resource recovery facilities

Abstract

The objective of this paper is to demonstrate the importance of incorporating more realistic energy cost models (based on current energy tariff structures) into existing water resource recovery facilities (WRRFs) process models when evaluating technologies and cost-saving control strategies. In this paper, we first introduce a systematic framework to model energy usage at WRRFs and a generalized structure to describe energy tariffs including the most common billing terms. Secondly, this paper introduces a detailed energy cost model based on a Spanish energy tariff structure coupled with a WRRF process model to evaluate several control strategies and provide insights into the selection of the contracted power structure. The results for a 1-year evaluation on a 115,000 population-equivalent WRRF showed monthly cost differences ranging from 7 to 30% when comparing the detailed energy cost model to an average energy price. The evaluation of different aeration control strategies also showed that using average energy prices and neglecting energy tariff structures may lead to biased conclusions when selecting operating strategies or comparing technologies or equipment. The proposed framework demonstrated that for cost minimization, control strategies should be paired with a specific optimal contracted power. Hence, the design of operational and control strategies must take into account the local energy tariff.

Plant-wide modelling of phosphorus transformations in wastewater treatment systems: Impacts of control and operational strategies

“…All these options, including evaluating the impact of influent flow equalization basins, are identified as promising research avenues that will be further studied in the near future (Jeppsson et al, 2013). The latter could be combined with proper electricity tariff models (Aymerich et al, 2015) and dramatically change the way how energy must be optimized. In this case study relative costs have been used (Jeppsson et al, 2007) due to the volatility of the prices (chemicals, electricity, sludge disposal, …).…”

Evaluating Physical and Fiscal Water Leakage in Water Distribution System

“…Uniform tariff scheme is the fixed price regardless of the quantity of water used by the consumer. Process of tariff revision is simple, easy to understand for consumers, and organizations pay according to the amount of water they actually use [37,38]. Due to lack of periodical proper monitoring, this also fails to control accurately and genuinely, especially in-line to leakage [39].…”

An Internet of Things Based Platform for Real-Time Management of Energy Consumption in Water Resource Recovery Facilities

“…While there is plenty of experience in optimizing energy generation and distribution, it is the demand side management that is receiving increasing attention by research and industry [4]. Thus far, there still exists a gap between energy consumption and costs since there is no generalized cost model describing current energy tariff structures to evaluate operating costs at WRRF [5]. In most energy studies, the energy consumption is multiplied by an average energy price.…”