WWW.WAS.ORG • WORLD AQUACULTURE • JUNE 2014 41 energy. Week 2 (Fig. 4) is for a higher level of wave energy. The wave energy system is providing a significantly greater portion of the required energy for the aquaculture operation. Week 3 (Fig. 5) is for a relatively energetic wave environment. In this scenario, the wave energy system provides nearly all the required energy, even during feeding periods. The key conclusion from this analysis is that the wave energy system substantially reduces the need for the backup diesel generator in most wave conditions, thus reducing the cost of diesel fuel and maintenance. In particular, note that on Week 3, there is very little need for the diesel in moderate waves, with the wave energy and battery providing nearly all of the energy required by the net-pen operation. Economics We have constructed a financial model (Fig. 6) for a hybrid wave-energy power system for net-pen salmon aquaculture that includes the following features: • Capital and operating costs for WEC and diesel systems • Variability in the cost of diesel fuel • Time-varying power requirements for aquaculture operations • Size of aquaculture operation. In addition, the model evaluates the potential for receiving a price premium by branding the aquaculture products as having been produced using renewable energy. The results of several different scenarios for the payback time of hybrid wave and diesel systems are shown in Figures 7, 8 and 9. The calculations are based on the following input parameters: • Average OPEX per kWh diesel is $0.59 • Diesel CAPEX per kWh is $425, with 342kWh installed capacity • Assumed nominal capacity of wave device is 220 kWh • Average production is 10,000 t • The hybrid system includes diesel, WEC and battery storage. The calculations included scenarios with a branding price premium of $0.045 or $0.090 per kg of salmon sold. The lifecycle cost over a 20-year period was calculated for a baseline diesel-only system compared to a hybrid wave-diesel system with no branding (Fig. 7), a $0.045 branding premium (Fig. 8) and a $0.090/kg branding premium (Fig. 9) of salmon sold. The effects of even a small branding premium on payback are striking. Conclusions As net-pen aquaculture moves into deeper waters, alternative means of providing power to the operations become essential to establishing and maintaining efficient and profitable operations. Initial conceptual development of systems that are a combination of diesel and wave energy conversion has shown attractive economics for powering offshore aquaculture operations. Wave Energy Conversion technology in the form of the Fred. Olsen Wave Lifesaver has demonstrated reliable operation at sea for extended periods at power levels consistent with aquaculture operational requirements. Inclusion of green, renewable energy branding further enhances the attractive economics of hybrid energy systems for offshore aquaculture. Notes Dallas Meggitt, Technical Director, Sound & Sea Technology, Inc., 3507 Shelby Road, Lynnwood, WA 98087 USA Tore Gulli, General Manager, Fred. Olsen Ltd., Pb. 1159-Sentrum, 0107 Oslo, Norway. ABOVE, FIGURE 6. Flow chart of a financial model to evaluate a hybrid waveenergy power system. TOP TO BOTTOM. FIGURE 7. Comparison of diesel only and hybrid systems with no branding premium. FIGURE 8. Comparison of diesel only and hybrid systems with $0.045/kg branding premium. FIGURE 9. Comparison of diesel only and hybrid systems with $0.090/kg branding premium.
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