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HOW MUCH CAN BE SAVED? ENERGY COST REDUCTION AT 9 STPS Cameron Staib, Elena Mejia Likosova, Nicholas Collins, Michael Thomas, King Intrapaiboon, Rui Yang Unitywater provides water and sewerage services over 750,000 people in the Moreton Bay and Sunshine Coast region. Unitywater has an overall Corporate Strategic Direction to pursue a business model of Operational Excellence, with the objective to “reduce the total cost to serve”. Arising from this, the Strategic Goal is to reduce rate-payers’ bills by $100 per annum. One of the strategic projects includes the reduction of Unitywater’s overall power consumption and energy costs by 25% to be achieved over 3 years commencing in FY15-16 relative to the baseline power costs in FY13-14 of approximately $9.7million. Over the FY13-15 period, Unitywater’s Treatment Plants team implemented changes across the 17 STPs that achieved ~$400k in savings. As part of Unitywater’s corporate energy cost reduction target, the Treatment Plant’s team needed to identify ‘what further energy cost reduction’ could be achieved at the Sewage Treatment Plants (STPs). This poster features a project conducted by Unitywater with MWH now part of Stantec to firstly audit 9 of Unitywater’s STPs and identify the Energy Cost Reduction Program for these STPs for the next three years, and the validated savings after the first year of interventions’ implementation. Key Issues • Identify saving opportunities beyond the already implemented by Unitywater at the 9 largest STPs. • Corporate driver is focussed on reducing the energy spend, not necessarily the power consumption; • Complicated tariff structure , i.e. the energy tariff structure varies across the 9 STPs, and • New tariffs came into effect in July 2015 and needed to be taken into account in developing the project savings. Methodology • Develop a Calibrated Energy Consumption and Spend model for each STP using the MWH MIMIC tool and identify a ‘long list’ of potential energy cost reduction opportunities; • Conduct economic assessment of opportunities and finalise the energy cost reduction program; • Develop a business case to commence implementation of opportunities with less than 10 years payback; • Implementation of the approved interventions and measurement of actual savings achieved. Summary of Activities The following activities were conducted during the course of the project: 1. MIMIC Model Calibration • Processing 2 years of 30 minute internal energy costs data and calibrate that to a typical daily energy consumption pattern for the STP as a half hourly dollar spend. • Assigning process areas to all drives and predicting the power consumption by process area on a half hourly basis for a ‘standard day’. Figure 1 contains a typical Mimic model output for one of the STPs investigated. 2. Energy Saving Opportunities Identification • Collation of opportunities already identified by the Treatment Plant’s team, together with additional opportunities identified during site audits. Benchmarking and assessment of the energy spend by process area helped in identifying opportunities that would realise significant savings. 3. Economic Evaluation of Opportunities involved: • Estimating the energy cost reduction by identifying the specific impact on electrical drives, then running the MIMIC energy cost model with this change to the electricity consumption pattern, • Identify any capital spend required to implement, • Estimating the energy spend change taking into account all the different aspects of the electricity tariff, including demand charges and peak versus off peak costs. Outcomes • 62 energy saving initiatives identified including simple operational measures (e.g. intermittent mixing) to innovative technologies (e.g. nitrite shunting), • Initiatives implementation is expected to result in up to $346k in annual savings at a cost of $1,470k (excluding project management expenses), • About 9.8% reduction on the overall energy cost is expected after implementation of the identified initiatives. Table 1 provides a summary per STP. The Implementation Stage 1 program commenced in early 2016, with: • 19 initiatives already implemented. • Annualised savings of up to $96,000 p.a. already realised by end March 2017. An example of a simple operational change is shown in Figure 2, where the fouled condition of the diffusers at Murrumba Downs STP prior cleaning in June 2016 is evident. Since cleaning and replacement of the broken diffusers (~ 4% of total diffusers) the following outcomes have been achieved: • About 10% reduction in blower power utilised, • ~367,000 kWh p.a. on energy consumption saved. • Up to $24,000 on energy cost saving will be expected on the first year. Cameron Staib MWH, Brisbane, QLD Elena Mejia Likosova MWH, Brisbane, QLD Nicholas Collins MWH, Brisbane, QLD Michael Thomas Unitywater, Caboolture, QLD King Intrapaiboon Unitywater, Caboolture, QLD Rui Yang Unitywater, Caboolture, QLD Figure 2. Fouled condition of diffusers at Murrumba Downs STP prior cleaning. Figure 1: Mimic Output Dashboard for energy consumption and cost for the Bribie Island STP Authors Table 1: Summary of Energy Cost Saving Opportunities identified for each STP with up to 10 years payback STP No. of Opportunities Potential Energy Cost Savings [$ p.a.] Capital Spend [$] Historical energy spend [$ p.a.] STP Overall Energy Cost Savings [%] Bribie Island 7 $24.3k $84k $222k 11% Brendale 5 $11.4k $18.8k $285k 4% Burpengary East 3 $4.4k $27k $346k 1.3% Coolum 3 $6.4k $23k $159k 4% Kawana 6 $39.3k $128k $406k 9.7% Maroochydore 8 $167k $879k $809k 21% Murrumba Downs 4 $18k $4k $537k 3.4% Nambour 3 $17.5k $20k $459k 3.8% South Caboolture 8 $58.4k $286k $332k 17.5% TOTAL 47 $346k $1,470k $3,554k 9.8%
