Sonar Systems to Support Monitoring of
Marine and Hydrokinetic Energy Sites
- A White Paper –
Patrick K Simpson
President, SciFish Sonar
February 2011
1. Introduction
Ocean wave and hydrokinetic energy shows great promise and new
technologies are becoming available which can make this renewable alternative
energy source more efficient and effective at replacing fossil fuels, and
keeping the environment clean. More
companies are investing in hydrokinetic energy research and development, for a
number of reasons. Environmentally
friendly power sources which are clean and do not cause pollution or
environmental harm are the key to the future, and there is more time and money
being invested in these areas.
Water that flows carries a great deal of energy, and the tides do not
have to be extremely strong for this power to be harnessed and used. Also, the undulations of waves on an
ocean surface can yield tremendous energy.
Advancements in technology have resulted in many new products and
methods being considered and evaluated concerning these alternative power
sources and generation methods.
One drawback to this sector is that the fish and marine wildlife
can be disturbed or potentially harmed in some cases, so constant monitoring of
the underwater environment is needed to ensure this does not happen. As an example, tidal turbines can kill
fish and other species if they get caught up in the equipment, and this can
change the underwater ecosystem, so newer methods and equipment are being
developed to minimize these impacts and protect the current habitat and marine
life.[1] With these new developments comes the
need to monitor underwater animal activities to confirm these new capabilities
are performing as expected.
2. Potential Environmental Effects of
Marine and Hydrokinetic Energy Technologies
In
recent testimony provided to the U.S. Congress,[2]
the Department of Energy reported that there are well over 100 conceptual
designs for converting the energy of waves, river and tidal currents, and ocean
temperature differences into electricity.
Most of these ocean energy and hydrokinetic renewable energy
technologies remain at the conceptual stage and have not yet been developed as
full-scale prototypes or tested in the field. Consequently, there have been few
studies of their environmental effects.
Most considerations of the environmental effects have been in the form
of predictive studies and environmental assessments that have not yet been
verified. While these assessments
cannot predict what if any impact a given technology may have at a given site,
they have been instructive in identifying several common elements among the
technologies that may pose a risk of adverse environmental effects:
·
Alteration
of current and wave strengths and directions
·
Alteration
of substrates and sediment transport and deposition
·
Alteration
of habitats for benthic organisms
·
Noise
during construction and operation
·
Generation
of electromagnetic fields (EMF)
·
Toxicity
of paints, lubricants, and antifouling coatings
·
Interference
with animal movements and migrations, including entanglement
·
Strike
by rotor blades or other moving parts
Recent
examples of these concerns have been seen in Southern California,[3]
where a broad array of commercial and recreational fishing associations in Noyo Harbor announced that it would be joining with major
stakeholders to monitor and comment on wave energy proceedings off the
Mendocino coast. The ad hoc committee, known as Fishermen Interested in Safe
Hydrokinetics, or the "FISH Committee," has filed a motion to
intervene with Pacific Gas & Electric's pilot project application for a 40
megawatt wave energy facility located in a 68 square mile area directly in front
of Noyo Harbor on the Mendocino Coast.
Fortunately,
there are tools available to support the monitoring that would be needed to
support the full utilization of our ocean’s renewable resources. In particular, monitoring animal
movements and migrations at or near a hydrokinetic site can be accomplished
using sonar technology. Sonar can
be used to detect, localize, track and report the presence of marine animals
including fish, whales, sharks, swimming birds and other marine life. Sonar systems can be deployed in advance
of a site installation to collect baseline data for comparison after an
installation and sonar systems can be mounted to an existing underwater
structure to provide constant monitoring during operations.
3. Sonar
Systems to Support Hydrokinetic Site Monitoring
Active
acoustics, more commonly referred to as sonar (sound navigation and
ranging), can meet a wide range of a hydrokinetic site’s
monitoring requirements. With
sonar, acoustic energy (sound) is projected into the water. The sound bounces off of underwater
targets such as fish, bottom, surface, and marine mammals and the echo is
returned to the sonar system.
Information can be extracted from these echoes, including the range,
location, size, and sometimes the composition. Some sonar systems, such as those
developed for the U.S. Navy are very sophisticated and specialized for specific
tasks. Other sonar systems are
relatively low cost and provide basic information, such as the fathometer on a
boat.
Two
notional concepts showing how sonar systems can provide hydrokinetic site
monitoring are shown below in Figures 1 and 2. Figure
1 illustrates the use of an upward looking sonar system that monitors
activity near a wave energy site.
This system is fully autonomous, dropped at the location of interest and
moored to the bottom with an anchor, and collects data for several weeks or
months. The upward looking sonar is
well suited for placement either at a proposed site, so that baseline
information can be gathered, or near an existing site so that comparative data
can be collected.
Figure
1. Autonomous Upward Looking sonar monitors
activity near a wave energy site
Figure
2. Networked sonar system with multiple
nodes monitors activity from a tidal energy site
Figure 2 illustrates the concept where several
sonar units, referred to herein as pods, are placed at key locations on a tidal
turbine system. The sonar pods are
networked together with the information aggregated, processed, stored and
transmitted as needed.
For
these sonar concepts to be practical for use as monitoring tools, they should
meet some basic requirements:
·
Remote
or Autonomous Operation
– the sonar system will be not be immediately accessible and should be
capable of either remote operation, or preferably, autonomous operation;
·
Rugged – hydrokinetic sites are
located in areas with large tides, high currents, high waves, and high winds,
therefore the sonar system will need to be built to withstand these extreme
conditions;
·
Adaptable – the sonar system should be
easily expandable to allow complete monitoring with a system that is sized
correctly for the site and each of the units in the system should be available
on a network using standard technology so that data can be transferred for any
additional processing that would be needed;
·
Easily
Deployed –
the sonar system should not be large and cumbersome and require expensive
equipment for deploying (and retrieving) the systems;
·
Reliable – the sonar system must be capable
of operating continuously for years with modest servicing, providing accurate
monitoring information throughout its use; and
·
Low-Cost – the system should be
affordable.
4. SciFish Sonar Systems
SciFish Sonar has two sonar systems that meet
the requirements described above: the Model PM-01 and the Model SS-01. The Model PM-01 is an
upward looking sonar for autonomous operations from the sea-bottom. The Model SS-01 is a sonar unit that can
be assembled into a networked sonar array attached to a site’s
superstructure. Details on each
model immediately follow.
4.1
Model PM-01
The Model PM-01 (Figure 3) is a standalone sonar system
designed to operate for up to a month on the sea bottom autonomously and is
able to count and track fish continuously. All data is stored in the unit
and an optional wireless connection at the surface allows you to access your
data at any time and it can provide complete control of the unit while
underwater; allowing you to change sampling parameters to better fit your needs.
Figure
3. SciFish Model
PM-01 Sonar
The Model PM-01 is an
upward looking, split beam, narrowband sonar system. Each unit utilizes a
custom electronic circuit board designed for power distribution, data storage,
and signal conditioning, providing the low power autonomous operations needed
for extended autonomous deployments.
Recent testing in
Alaska’s Bering Sea has demonstrated the Model PM-10’s ability to
reliably collect fish passage data within one meter of the surface. These
units can be programmed to collect data for up to several months at a time.
4.2
Model SS-01
SciFish Model SS-01 sonar (Figure 4) is a low-power, rugged, and
highly portable system originally designed to be deployed in remote Alaska to
count the abundance of smolt migrating down a
river. The Model SS-01 is a single
sonar unit, a pod, that can be networked together to form a sonar array with
one to one hundred individual sonar units.
Each Model SS-01 sonar pod is an upward looking, single beam, narrowband
transducer sonar system. The system
gets power and stores data via custom underwater cables from a terminal
box. Each sonar pod has a custom
electronic circuit board designed to provide the necessary power distribution
and signal conditioning.
Figure
4. SciFish Model
SS-01 Sonar
The
Model SS-01 is cost-effective, needing minimal monitoring by any technician or
biologist. Real-time backup ensures
no data loss. System can be
accessed at any time to get counts when needed. Modular design allows customized fit to
any river system using a simple shore-based deployment.
With
several years of successful deployment in the harsh climates of Alaska, this
system has demonstrated the reliability and accuracy needed for a wide range of
related applications including: monitoring fish behavior near structures and
fish counting. The low cost, modular design of the system makes it ideal for
integration in offshore wind and tidal energy projects.
5. Conclusion
Hydrokinetic
energy offers great promise toward providing a source of renewable energy. As these systems are deployed, they will
need to monitor their affect on the environment and the marine life that occupy
the same area. SciFish
Sonar provides affordable monitoring tools that can assist with these
monitoring efforts.
For
more information on SciFish Sonar products, please
visit our website: www.SciFish.com or contact the author at the address
found below.
Patrick
K Simpson
President, SciFish Sonar
PO Box 242065
Anchorage AK 99524-2065
(o) 907-563-3474
(c) 360-509-2440
(f) 907-563-3442