Page 282 - Renewable Energy Devices and System with Simulations in MATLAB and ANSYS

Marine and Hydrokinetic Power Generation and Power Plants 269

A wide variety of MHK technologies have been proposed and tested by industry develop-
ers, particularly in oceanic countries such as Ireland, Denmark, Portugal, Sweden, the United
Kingdom, and the United States. There are many examples of recent installations of wave energy
conversion (WEC) devices. A Swedish company, Seabased, is currently installing a 10 MW dem-
onstration plant off Sotenäs on the west coast of Sweden [8]. A U.S. company, Ocean Power
Technologies, deployed a 150 kW system in Scotland in 2011 [9]. In the United Kingdom,
Aquamarine tested their 315 kW Oyster wave energy device at the European Marine Energy
Center’s test site in Orkney in 2009 [10]. Northwest Energy Innovations tested their prototype
Azura device off the coast of Oregon in 2012 and started a grid-connected demonstration proj-
ect at the U.S. Navy’s Wave Energy Test Site in Hawaii in 2015 [11]. Regarding current energy
conversion (CEC) devices, in the United States, Ocean Renewable Power Company deployed a
TidGen tidal power system in northern Maine [12], and Verdant Power completed a grid-connected
demonstration of their prototype design in the East River in New York Harbor in 2009 [13]. In the
United Kingdom, Marine Current Turbines successfully deployed a 1.2 MW SeaGen tidal energy
system in Strangford Narrows in Northern Ireland in 2008 [14].
However, there are social, economic, regulatory, and environmental issues (e.g., marine mammal
protection areas, fishing permit areas, and shipping routes) when considering MHK generation, and
there are technical challenges, including the device power capture efficiency, the array/farm system
performance, and the conversion efficiency of the power take-off system (PTOS). As a result, MHK
technology is still emerging, and the cost of energy from MHK energy devices is not yet competitive
with other forms of renewable energy. Studies from the Carbon Trust [15] and a reference model
supported by the U.S. Department of Energy [16] showed that the levelized cost of energy (LCOE)
is approximately 60–80 cents/kWh for a WEC array and 40–50 cents/kWh for a CEC farm in the
commercial-demonstration-scale size of 10–30 MW. The Carbon Trust report also estimated the
relative contribution of different subsystems to LCOE for typical WEC and CEC devices as sum-
marized in Table 11.2.
A successful MHK energy converter design requires a balance between the design performance
and cost. The cost of energy depends on the device’s power output; the cost of manufacturing,
deployment, and operations and maintenance (O&M); and environmental compliance (e.g., marine
mammal protection areas and shipping lanes). The research community and industry developers will
need to overcome technical and practical barriers to improve power generation performance and
reduce LCOE to accelerate technology development to commercial readiness.
Cost reductions for MHK energy devices will come primarily from improving device power
performance, optimizing array/farm layouts, reducing capital costs, and improving O&M strategies.
In particular, the capability to apply an advanced control algorithm to improve power output, reduce
loads, and improve the conversion efficiency of the PTOS is essential to improve the MHK device’s
power performance, especially for most WECs. The objective of this chapter is to review the status
of current MHK renewable energy, particularly focusing on the generator and power conversion

TABLE 11.2
Estimated Percent Contributions to Levelized Cost of Energy for Early Commercial-Scale
Wave Energy Conversion and Current Energy Conversion Systems
Installation Structural Station Power Grid O&M
Technology (%) Costs (%) Keeping (%) Take-off (%) Connection (%) (%)
WEC 10.0 29.0 6.0 20.0 8 27.0
CEC 33.2 13.8 15.5 10.8 8.7 18.0

Source: Adapted from Carbon Trust, Accelerating Marine Energy, Carbon Trust, London, U.K., Tech. Rep., 2011.