The Cost Advantage of Implementing Wave Power in Hawaii
Dong-hyeon Park
More than 70% of planet Earth is covered with water. Since such is the case, the ocean is
an extremely large source of energy. However, very few countries take advantage of this
immense energy potential. This paper will investigate the prospect of installing wave power
plants in Hawaii and the economic benefit of replacing petroleum power plants with wave
generators. Since Hawaii depends heavily on imported fuels to generate electricity and has the
highest electricity cost in the nation, implementing wave power plants in Hawaii can be very
advantageous and energy efficient.
1.
Overview of Wave Power
1.1
What is Wave Power?
Wave power is a method of generating electricity from the ocean surface oscillating up
and down. The wave motion is generated by the wind currents traveling over the ocean. Since
wind currents are formed due to the pressure differences generated by sunlight, the original
source of wave energy is solar. Waves can travel thousands of miles with very little energy loss.
In addition, waves are extremely efficient at gathering energy from winds, so people often
considered wave energy as a highly concentrated form of solar energy1. Since wave energy
comes from solar energy, as long as sun shines on earth, wave energy is never depleted. Also,
wave power is available at any time of the day, so wave power is free of the energy storage
problems that wind and solar power plants face.
1.2
1
Energy Potential of Wave Power
Ocean Energy Council, “Wave Energy.” 2011. http://www.oceanenergycouncil.com/index.php/WaveEnergy/Wave-Energy.html (accessed n.d.).
According to United States Bureau of Ocean Energy Management, Regulation and
Enforcement (BOEMRE), the worldwide estimate of economically recoverable wave energy
resource is 140 to 750 TWh per year with the current technology2. However, a very small
fraction of that potential is currently exploited. In 2008 worldwide, only 0.546 TWh of electricity
was generated using ocean resources, which is the smallest fraction of Earth’s renewable energy
production.3 Even within 546 GWh of electricity generated, majority of this energy comes from
tidal and ocean current powers, while wave power accounts for a very small fraction. The global
wave power industry is still premature, so commercial production of wave energy is very limited.
However, there are several prototype wave energy generators that are tested in various locations
around the world.
The United States of America has one of the largest wave energy potential in the world.
The total average wave energy potential of the U.S. coastline at 60 m depth is estimated to be
Figure 1.1 – Wave Energy Potential in US
2
U.S. Department of the Interior. Technology White Paper on Wave Energy Potential on the U.S. Outer
Continental Shelf, 2006. http://ocsenergy.anl.gov/documents/docs/OCS_EIS_WhitePaper_Wave.pdf
3
International Energy Agency. http://www.iea.org/stats/renewdata.asp?COUNTRY_CODE=29 (Renewables and
Waste in World in 2008; accessed n.d.).
2,100 Terawatt-hours4. Out of the available 2,100 TWh of resource potential, 1,250 TWh is
allocated in the coasts of Alaska, and 300 TWh in the coasts of Hawaii as shown in Figure 1.1.
However, despite abundant resources, the U.S. currently generates zero energy from wave or any
other ocean resources. Developing and installing technologies that can harness these untapped
resources will greatly reduce the nation’s dependency on fossil fuel. Among the fifty states in
United States, the benefit of installing wave power plants will be the most significant in the state
of Hawaii.
In order to investigate the potential of wave power in United States, this paper will study
focus on implementing wave power in Hawaii. The resource potential of Hawaii, and the
economic advantages of replacing petroleum with wave power as the main source of electrical
energy in Hawaii will be investigated.
2.
Wave Power in Hawaii
2.1
Hawaii’s Wave Power Potential
There are several factors that make Hawaii suitable for wave power development. One of
them is Hawaii’s large dependence on imported fossil fuels. Almost one-ninth of Hawaii’s
energy comes from petroleum that is shipped from Alaska5. This is extremely inefficient, since a
large amount of fuel is lost every year in order to transport the petroleum to Hawaii. Due to
Hawaii’s dependency on imported fuel, the state has the nation’s highest residential electricity
4
U.S. Department of the Interior. Technology White Paper on Wave Energy Potential on the U.S. Outer
Continental Shelf, 2006. http://ocsenergy.anl.gov/documents/docs/OCS_EIS_WhitePaper_Wave.pdf
5
US Energy Information Administration, “Hawaii.” n.d. http://www.eia.doe.gov/state/state-energyprofiles.cfm?sid=HI (accessed n.d.).
price of 30.13 cents per kWh, which is almost three times the U.S. average of 10.99 cents per
kWh 6.
Another factor that makes Hawaii suitable for wave energy development is its wide
interest in renewable energy. Although less than 10 percent of Hawaii’s electricity generation
comes from renewable energy sources, Hawii has a diverse portfolio of renewable energy.
Hawaii’s renewable energy production ranges from solar to hydroelectric, geothermal, wind, and
even biomass. Hawaii is one of the top-ten producers of solar energy in the nation and third
biggest generator of geothermal energy. In addition, the state of Hawaii plans to increase its
renewable energy portfolio to 40 percent by 2030, and large portion of this plan rely on the
development of wave and other ocean energy resources.
Lastly, Hawaii’s wave resource potential is one of the largest in the nation. As mentioned
before, total estimate of wave energy potential in the coasts of Hawaii is 300 TWh per year. This
number comes from the following equation, which calculates the raw energy that can be obtained
from any wave:
𝑃=
𝜌𝑔� 𝑇𝐻 �
32𝜋
The equation yields power in watts per meter, where ρ is the density of seawater, which is 1,025
kg/m3, g is the gravitational acceleration, 9.81 m/s2, T is the period of the wave in seconds, and
H is the wave height in meters7. The equation shows that power generated from waves varies by
the square of wave height. Since Hawaii is an island located in an area that experiences strong
6
US Energy Information Administration, “Hawaii.” n.d. http://www.eia.doe.gov/state/state-energyprofiles.cfm?sid=HI (accessed n.d.).
7
U.S. Department of the Interior. Technology White Paper on Wave Energy Potential on the U.S. Outer
Continental Shelf, 2006. http://ocsenergy.anl.gov/documents/docs/OCS_EIS_WhitePaper_Wave.pdf
wave swells from all four sides, it has one of the world’s most powerful waves per square meter.
According to BOEMRE, typical wave energy in Hawaii tends to be 12 to 22 kW/m due to trade
winds.
2.1
Current Technologies
Thanks to Hawaii’s interest in renewable energy and its abundant wave resources, several
wave energy projects are under consideration. The three main wave energy projects which are
expected to be implemented in the near future are Office of Naval Research’s PowerBuoy,
Oceanlinx’s Oscillating Wave Column (OWC), and Ocean Power Delivery’s Pelami.
Office of Naval Research’s PowerBuoy, is classified as a point absorber, which
generates electricity by taking advantage of the vertical up and down movement of the wave at a
single point. The PowerBuoy’s main compartment is fixed at a single location. Floating buoy
located inside the main compartment is free to move vertically depending on the wave motion at
that location. One unit of PowerBuoy is known to generate up to 40kW of energy, and it has
been tested in various locations around United
States, including the coast of Oahu, Hawaii8.
According to the Office of Naval Research,
PowerBuoy has been under operation for over
4,400 hours since December 14th 2009 and no
major problems had occurred. A single unit of
PowerBuoy is very compact, with a diameter
Figure 2.1 - PowerBuoy
8
of less than 12 feet and length of only 55 feet,
U.S. Department of the Interior. Technology White Paper on Wave Energy Potential on the U.S. Outer
Continental Shelf, 2006. http://ocsenergy.anl.gov/documents/docs/OCS_EIS_WhitePaper_Wave.pdf
most of which is submerged in water 9. Thanks to its compact design, a 10 MW power station
composed of PowerBuoys will only occupy 0.125 square kilometers of space. According to
Ocean Power Technologies, the developer of PowerBuoy, the cost of electricity generated by the
PowerBuoy is estimated to be 15 cents per kWh, which is half of Hawaii’s current electricity
cost10.
The Oscillating Water Column (OWC) developed by Oceanlinx is a terminator type
generator. The terminator device tries to capture the power of the wave by lying perpendicular to
the direction of wave motion. In OWC, a chamber inside the device lets wave move freely
through the chamber. As the volume of water inside the chamber varies due to the wave motion,
air travels though a turbine, causing the
turbine to rotate and generate electricity.
Each unit of Oceanlinx’s Mk2 generation
generator can generate up to 1000kW of
energy. Based on the performance testing
in Californian coast, one unit of OWC
produced approximately 1,973 MWh/yr of
Figure 2.2 - Oceanlinx’s Mk2 generator
energy, which corresponds to 225
households11. According to cost analysis by Global Energy Partners, installation cost of one unit
of OWC is $3.9 to 7.2 million without federal aid. In addition, for a full-scale 300,000 MWh per
year plant in California, 152 units will be needed with total investment cost of $238 million and
annual maintenance cost of $11 million. The expected electricity cost is 9.2 cents per kWh in this
9
Ocean Power Technologies, “PowerBuoy.” 2011.http://www.oceanpowertechnologies.com/projects.htm(accessed
n.d.).
10
Same as [9]
11
Roger Bedard, “Offshore Wave Power Feasibility Demonstration Project.” (2005):
http://oceanenergy.epri.com/attachments/wave/reports/009_Final_Report_RB_Rev_2_092205.pdf
full-scale OWC plant. On February 4th, 2008, Oceanlinx announced a wave energy project on the
coast of Maui, Hawaii, to install a 2.7 MW plant by 2011. The estimated cost of the project is
$20 million, for three wave platforms. Oceanlinx’s latest wave generator, the blueWAVE, can
generate over 2.5 MW per unit in deep water for a much less manufacturing cost than their older
generators.
The Pelami generator by Ocean Power Delivery is an attenuator. Attenuators are wave
generators that have long floating structures that lie parallel to the wave movement. These
devices create electricity using the difference in height along each structure. Each unit of Pelami
developed by Ocean Power Delivery can produce 750 kW of energy. One unit has four
segments, each 30 meters long and 4.6 meters in diameter12. The four segments float on the
ocean as a one long unit, attached by three joints. Based on performance assessment conducted
on Hawaii, each unit of Pelami is expected to produce 1,663 MWh of energy every year, which
can provide power to 191 homes. The capital cost of installing a single unit of Pelami is
estimated to be $3.5 to 5.5 million, but this cost could be reduced to $3.3 to 5.0 million with
Figure 3.3 – Pelami generator
12
U.S. Department of the Interior. Technology White Paper on Wave Energy Potential on the U.S. Outer
Continental Shelf, 2006. http://ocsenergy.anl.gov/documents/docs/OCS_EIS_WhitePaper_Wave.pdf
federal assistance. Further cost analysis, provided by Global Energy Partners, show that for a
300,000 MWh/yr plant, 180 units of Pelami will be needed, resulting in a total investment cost of
$270 million. Note that unit installation cost of Pelami is lower in the power plant estimation,
since the generators are mass produced. In addition, annual maintenance cost on the devices is
expected to be $11 million for 180 units. This results in an estimate of 10.4 cents per kWh of
wave energy cost in Hawaii for a Pelami power plant13.
3.
Cost Analysis of Converting to Wave Power in Hawaii
3.1
Current Petroleum Cost
In the year 2009, the state of Hawaii consumed 12,954 thousand barrels of petroleum to
generate 80.4 trillion Btu of electrical energy. Based on United State’s average domestic crude
oil price of $85.66 per barrel, the cost of importing petroleum for electricity generation in Hawaii
each year is estimated to be (12,954 × 10� 𝑏𝑎𝑟𝑟𝑒𝑙𝑠 𝑜𝑓 𝑝𝑒𝑡𝑟𝑜𝑙𝑒𝑢𝑚) × $85.66⁄𝑏𝑎𝑟𝑟𝑒𝑙 =
$1.11 𝑏𝑖𝑙𝑙𝑖𝑜𝑛. Note that this is a rough estimate of the cost, since it does not take into account
the cost of transporting the oil to Hawaii, or any federal aid. Since 1000 Btu is equivalent of
0.2928kWh, the amount of electricity generated by 80.4 trillion Btu of petroleum is
80.4 × 10�� 𝐵𝑡𝑢 ×
3.1
(�.���� ���)
���� ���
= 23.5 𝑚𝑖𝑙𝑙𝑖𝑜𝑛 𝑀𝑊ℎ14.
Oscillating Wave Column Plant
The first cost analysis will use Oceanlinx’s OWC generators as the model for wave
power. Based on Oceanlinx’s Mk2 generation generators that produce 1,973 MWh per year, it
13
Roger Bedard, “Offshore Wave Power Feasibility Demonstration Project.” (2005):
http://oceanenergy.epri.com/attachments/wave/reports/009_Final_Report_RB_Rev_2_092205.pdf
14
US Energy Information Administration, “Hawaii.” n.d. http://www.eia.doe.gov/state/state-energyprofiles.cfm?sid=HI (accessed n.d.).
will take 23.5 × 10� 𝑀𝑊ℎ ×
� ����
�,��� ���
= 14,910 𝑢𝑛𝑖𝑡𝑠 to power the whole state of Hawaii.
(Note that this assumes the power generation on the shore of California to be same as the power
generation on the shore of Hawaii. However, since Hawaii has greater wave energy potential
than California, the actual energy generation by a single unit will be much greater 1,973 MWh in
Hawaii.) The capital cost of installing such power plant will be 14,910 𝑢𝑛𝑖𝑡𝑠 ×
$��� �������
��� �����
=
$23.35 𝑏𝑖𝑙𝑙𝑖𝑜𝑛. Since the energy cost from OWC plant is 9.2 cents per kWh, the annual benefit
cost of replacing petroleum with wave power will be 0.13 𝑐𝑒𝑛𝑡𝑠/𝑘𝑊ℎ − 9.2 𝑐𝑒𝑛𝑡𝑠/𝑘𝑊ℎ =
20.93 𝑐𝑒𝑛𝑡𝑠 𝑝𝑒𝑟 𝑘𝑊ℎ. This results in an annual price benefit of 23.5 × 10� 𝑘𝑊ℎ ×
20.93
�����
���
= $4.92 𝑏𝑖𝑙𝑙𝑖𝑜𝑛 solely based on difference in electricity price. Combined with $1.11
billion spent on petroleum purchase, $6.03 billion is earned with the new plant. Assuming $1
billion is spent each year on maintenance, the annual benefit of OWC plant is roughly $5.03
billion. Therefore, it will only take $23.35 𝑏𝑖𝑙𝑙𝑖𝑜𝑛 ×
� ����
$�.�� �������
= 4.64 𝑦𝑒𝑎𝑟𝑠 to pay off the
initial capital cost. The pay-off duration of 4.64 years is very reasonable, which makes wave
power an extremely desirable alternative.
3.1
Pelami Wave Plant
The other option is to use Pelami wave generator by Ocean Power Delivery. Since one
unit of Pelami can generate 1,663 MWh each year, it will take 23.5 × 10� 𝑀𝑊ℎ ×
� ����
�,������
=
14,131 𝑢𝑛𝑖𝑡𝑠 to power the entire state of Hawaii. This corresponds to initial installation cost of
14,131 𝑢𝑛𝑖𝑡𝑠 ×
$��� �������
��� �����
= $21.2 billion. The electricity cost from Pelami wave plant is 10.4
cents per kWh. This is much smaller than the current petroleum-based electricity cost of 30.13
cents per kWh, so the electricity cost benefit of implementing Pelami wave power plant is
30.13
�����
���
− 10.4
10� 𝑘𝑊ℎ × 19.73
�����
���
�����
���
= 19.73 𝑐𝑒𝑛𝑡𝑠 𝑝𝑒𝑟 𝑘𝑊ℎ. This leads to price benefit of 23.5 ×
= $4.64 𝑏𝑖𝑙𝑙𝑖𝑜𝑛 each year for replacing petroleum with wave power,
based solely on the change in electricity price. Taking into account $1.11 billion spent each year
on purchasing petroleum, $5.75 billion is saved each year if wave power is implemented in
Hawaii. Therefore it will only take $21.2 𝑏𝑖𝑙𝑙𝑖𝑜𝑛 ×
� ����
$�.�� �������
= 3.69 𝑦𝑒𝑎𝑟𝑠 to pay off the
initial installation cost of Pelami power plant, which is very short. Even with annual maintenance
cost of the plant, which will be much less than $1 billion, it will still take only $21.2 𝑏𝑖𝑙𝑙𝑖𝑜𝑛 ×
� ����
$�.�� �������
= 4.46 𝑦𝑒𝑎𝑟𝑠. This suggests that using Pelami wave generators as sole source of
electricity generation is extremely beneficial solely based on cost analysis. As for the total ocean
space the 14,131 unit power plant will cover, assume each Pelamis will be separated by 20
meters, so each unit will cover 50𝑚 × 150𝑚 = 7500𝑚� or 0.0075 km2 of sea area. Therefore,
the total area covered by the power plant is 14,131 𝑢𝑛𝑖𝑡𝑠 ×
extremely reasonable amount of space.
�.���� ���
� ����
= 106 𝑘𝑚� , which is an
Between Oceanlinx’s OWC and Ocean Power Delivery’s Pelami, since Pelami power
plant takes slightly less time to pay off the initial capital cost than OWC power plant, Pelami
power plant is more advantageous by a very small margin. However, Oceanlinx’s latest
blueWAVE generator is highly likely to be a better option since it has greater power generation
per unit for a smaller installation cost.
4.
Additional Benefits
Hawaii can further lessen petroleum consumption in the country switching to electric cars
for main source of transportation. Since Hawaii requires little or no heating, fossil fuel
dependency will be greatly reduced if transportation sector reduce its dependence on oil. By
increasing electricity consumption, Hawaii can aim to become energy independent and reduce its
reliance on outside sources for energy. This is advantageous for Hawaii since it can significantly
reduce its energy cost and eliminate the energy lost from transporting fuel from outside.