Renewable energy and shellfish farming, using solar energy to grow oyster seed that will then sequester ocean CO2 – what’s not to like? Our first post about our new demonstration Solar Powered FLUPSY (Floating Upweller System). We’re very excited about this project and as performance data becomes available we will be reporting a lot more but for now a rather longish post and photo essay about the design and construction.
The hatchery based culture of bivalve shellfish consists of two critical phases: a larval component which takes place in the hatchery; and a post-larval nursery phase which bridges the gap between the hatchery and grow-out environments, providing the animals with an opportunity to adapt to the wild conditions in a nurtured environment. Because of the high cost of algae production in modern hatcheries, it is extremely cost advantageous to develop production strategies to transfer seed at small sizes (2-3mm) from the hatchery to a nursery system supplied with natural phytoplankton. Nursery systems offer cost effective strategies to grow small seed to larger size 6mm – 10mm before transfer into the production grow-out system. While hatchery culture techniques are generally well established, the nursery phase (both land and water based) represents significant opportunities for optimization through the adoption of technological advances.
In many locations the extensive nursery systems consist of FLUPSY (Floating Upweller System), which consist of floating platforms with shellfish seed suspended on “upweller” screens in the marine environment, through which seawater containing naturally produced phytoplankton is pumped. In British Columbia, these FLUPSY’s are typically large, centralized and require inputs of electricity, usually from generators for pumping. For new native species development, this presents a variety of challenges which restrict development.
- Large systems are capital intensive and typically geared towards mass production of one species typically oysters, and do not facilitate smaller volumes with different requirements.
- Centralized systems do not facilitate the commercialization of native species that are restricted to be maintained within their own zones due to disease and genetic concerns established by Fisheries and Oceans Canada
- Electrical demands require that FLUPSY”s are plugged into shore power often unavailable in remote aquaculture development areas;
- Use of generators presents high operational costs, social issues relating to noise and increased risk of environmental contamination from accidental fuel spills.
Additionally almost all FLUPSY’s are “one-offs” built typically by operators and little information exists to provide design guidance, compare construction details and efficiencies. Without such information errors inevitably will be repeated.
For several years, we have been following emerging technological developments on the east coast of North America that potentially may greatly address shellfish nursery limitations including a small solar powered FLUPSY technology developed by engineering students and researchers at Rogers Williams University, Rhode Island.
This technology is novel on the west coast and we believe it has significant potential for adoption by the BC shellfish culture industry for a variety of species.
This project is the marriage of two recently developed advancements on FLUPSY and our suspended shellfish culture raft technologies. This project was funded by the CSR, the Aquaculture Innovation and Market Access Program (AIMAP) in conjunction with Evening Cove Oysters with assistance from Dr. Dale Leavitt from Roger Williams University.
Overview of FLUPSY principles.
FLUPSY stands for Floating Upweller System, this is essentially a field version of a standard shellfish hatchery upweller. Upwellers used for small shellfish seed consist of a cylinder or rectangular bin with a fine mesh screen on the bottom on which shellfish juveniles (typically clams oysters) are maintained. A flow of water (and phytoplankton feed) are induced to flow upwards through the screen and past the shellfish juveniles. At optimal flow the seed is maintained in what is called a “fluidized bed” in which the seed tumble and mix gently. This way the seed have uniform access to feed flowing past them.
In the FLUPSY, the upweller is taken out into the environment and floated on the surface of the ocean. By having little to no pumping head it is highly efficient to flow significant amounts of seawater and feed past the seed.
Commercial FLUPSYs typically consist of six or more “bins” that are on either side of a central channel. These bins may range between 0.25- >1m2 surface area. Water is evacuated from the centre channel by means of a propeller or paddlewheel pump, this causes water to flow through the FLUPSY bins into the centre channel.
The general flow of seawater in a FLUPSY is shown in the following diagram.
2.0 Project Objectives
The objectives of this project component are expected to produce:
- A “farm scale” extensive nursery system that will allow the commercialization of native species such as the native cockle and other shellfish species;
- Greater sustainability for the shellfish industry via integration of renewable energy sources, reduced environmental risk and operational costs;
- Further integration and usefulness of the new CSR next generation shellfish culture raft design;
- A FLUPSY design that will have greater social acceptance through lower profile, consistency with shellfish culture rafts, add quiet operations.
- Provision of FLUPSY design to industry for further adaption and improvement.
The following design criteria were established to guide design criteria during FLUPSY development:
- Adapt Roger Williams University FLUPSY design for Vancouver Island solar irradiance.
- Adapt FLUPSY components to be a “bolt-on” option for VIU next generation shellfish raft.
- Use “off-the-shelf” components wherever possible to facilitate future adaptation.
- Develop the design to be as “low profile” as possible and to be able to be integrated in normal shellfish raft farm profiles.
- Create a modular design that can be expandable
3.0 Design Notes
3.1 Renewable energy system
The electrical system was designed as per specifications provided by Dale Leavitt’s earlier designs. The electrical summary is shown in the following figure.
Average peak sun hours at the site were calculated as shown in the following sidebar figure. Since we wanted the system to run from March through to October it is designed on the worst case average insolation received on site October of 2.17PSH.
The original configuration of six 12V (200W) solar panels that were configured as three panels in series (to total 36VDC) with two sets of panels wired in parallel. In the modified system we used eight 170watt panels at 24V each. They are set up in four strings of two, so each string is feeding 48V to the combiner and in turn the combiner sends the 48V to the maximum power point charge controller (MPPT) which charges the batteries at 36V.
In our battery bank we have twelve 6V batteries which are running in two strings of six, for two 36V strings in parallel. A Rubbermaid brand plastic garden bench storage container (Home Depot), with the floor reinforced with plywood and ventilation added was used for battery storage.
The 2.6’x 5.2’ (790x1587mm) BP brand solar panels were mounted horizontally to reduce potential windage and care was taken to allow space below the panels to allow storm winds to spill under the panels. The panels were set at an angle of 49 degrees from horizontal to maximize solar exposure for site latitude. Spacing between the panels was set so that they would not shade each other. Commercial panel racking was attached to a framework constructed from structural lumber 2×4”, 2×6” etc. Approximately 1/3 of the raft space 10’ x 27’ was taken up by the panel installation.
The total costs of electrical components at time of purchase was approximately $11,000. Significantly, these costs are well within costs or less than a diesel powered generator (before we start talking about diesel costs.)
Electric motor and pump assembly
The circulation electrical system is based on a 36VDC configuration using a 1/3hp permanent magnet 90VDC motor (Leeson C42D17FK4A DC Motor 1/3 HP 56C 90v 1750 CCW) operating with a 3 amp current draw at 85% efficiency at 90v.
Rather than using a paddlewheel drive as is common in BC FLUPSY’s we remained with a vertical flow propeller pump as used in the original Roger Williams University ALT-FLUPSY. This decision was based on the fact that engineering data was not available for a paddlewheel drive (note in future we wish to test this and have left the option open to add a paddlewheel later).
We constructed the drive assembly out of a 4.5’ piece of 12” Kor-flo ribbed sewer pipe so that the motor assembly was encased and the entire unit could be removed from the FLUPSY for winter storage or servicing. Large cut-outs in the pipe were made as inlets and the pipe protrudes below the level of the FLUPSY bins to direct discharge water away from the FLUPSY.
The motor was mounted on an aluminum plate within the pipe assembly in such a way that the motor assembly would be above the surface of the water and a LoveJoy Jaw coupling was used to connect a ½” diameter 36” long stainless steel shaft. The end of the shaft was machined to take a Minn Kota MKP-32 Weedless Wedge 2 Propeller.
The lower end of the shaft was supported by a two inch EPDM cylinder mounted in the sewer pipe, in which a marine cutlass bearing was mounted. A marine shaft zinc was installed on the S/S shaft to reduce galvanic corrosion.
FLUPSY bin and channel assembly
Typically FLUPSY bins are custom fabricated from aluminum or fiberglass. In order to reduce cost and facilitate construction We found a trash can (trade name King-Can supplied by Planet Clean, Nanaimo) constructed from structural plastics. We adapted the can by mounting a welded aluminum assembly at the top and bottom to facilitate lifting and screen assembly respectively.
The bottom of the King-can was cut out and angle aluminum was welded around the circumference. A matching square of 1” aluminum flat bar formed a plate to sandwich a layer of nitex plastic screen to retain shellfish seed above a layer of 1” vinyl coated mesh (Aqua-Pacific Wire Mesh, Nanaimo). A small marine zinc was attached to each assembly to reduce galvanic corrosion.
Discharge and alignment for the bin was facilitated by horizontally mounting a 4” schedule 40 PVC pipe through one wall of the bin. The other end of the pipe was anchored to the bin wall with a schedule 80 PVC flange fitting bolted to the bin wall. A hole saw was used to cut multiple discharge holes in the pipe. The pipe was then wrapped in vexar plastic mesh in order that seed are not accidentally discharged from the bin.
The dimensions of the centre channel are 8’x2’x2’. The centre channel assembly was constructed from ¾ marine plywood coated in marine epoxy. We would have preferred to construct the centre channel from fiberglass or aluminum but were reluctant to incur the additional expense of what is essentially a prototype that might be subject to further modification during testing.
A large hole was cut into the bottom of the channel to allow the motor/pump assemble to pass though. Eight holes were cut into the upper portion of the side walls. To vary outflow between bins, 4” PVC Schedule 40 gate valves were modified and attached flush with the side walls through these holes. These valves were installed to be able to balance flows between bins and to assist with mounting the bins (see below).
One end of the channel assembly was constructed so that it could be unbolted and removed in the future. We hope to test and compare the use of a paddlewheel pump and constructed the channel to potentially allow this.
Mounting bins to the channel assembly
Square tube aluminum cut lengthwise to form a U shape was mounted on two sides of the upper bin (facing down) and on the centre channel and on other side mounting assembly (facing up). This supports the bin assembly and allows enough play for the 4” discharge pipe to be slid horizontally into the female fitting of the gate valves
Overall adaptation of raft to support FLUPSY
FLUPSY mounting components
Adapation of the VIU Shellfish raft to support the FLUPSY unit was relatively simple. Four galvanized 4”x4” angle iron components (AIT Technologies) were constructed and these were bolted underneath the raft structural beams.
These four components were centered within the raft to support the central FLUPSY channel and the FLUPSY bins Each piece of angle iron was bolted to three structural beams. We made the central two angle iron components longer in order that we could potentially mount a paddle wheel for testing in the future.
The overall layout on the raft is shown on the following figure, The FLUPSY bins and channel were mounted centrally to one end with the raft parallel to the the floats. We did this to potentially minimize rocking due to wave action. However we noted that the bins and channel components could be mounted almost anywhere within the raft assembly by the nature of the mounting design and that multiple units could potentially be installed within a single raft.
As discussed previously the solar panels occupied the opposite third of the raft . This allowed for significant work area (~450 ft2 remaining on the deck of the raft.
Structural Supports and decking
The FLUPSY components were supported by integrating wooden components and decking onto the raft. This included:
- Wooden structural supports for solar panels (previously described).
- Supports for wooden decking by utilizing wooden cross members normally used to deploy suspended shellfish culture equipment on raft.
- Extra reinforcing to support the weight of the battery bank.
- Plywood decking painted neutral grey over work areas of the raft and over the FLUPSY bin/channel assemblies.
Details of these aspects of final construction are detailed in the following figure. Additionally we ballasted the FLUPSY with suspended concrete weights (five gallon pails of concrete) to even out the floatation and level the raft once it was launched.
Apparatus for lifting and servicing bins.
Typically a rolling gantry is installed on the deck of a FLUPSY to lift FLUPSY bins. We consciously avoided the addition of a gantry to the Solar-FLUPSY in order to maintain the low profile of the system. All lifting of bins for servicing may be done be vessel mounted boom. A small A-Frame rolling gantry could also be simply added to the raft design if required. We are also encouraged by other recent nursery designs for example Taylor Shellfish, Washington State where gantry cranes have been constructed that fold down when not in use to reduce visual profile.
4.0 Operations and Initial Observations.
Initial testing indicates that the raft is achieving all desired performance and outcomes. We will not be able to document a full analysis until the completion of at lease one growing season and will do so in a later report. Ultimate success will depend on:
- the ability of the system to provide biological (pumping) requirements;
- the ability to harvest, store and minimize the use of renewable energy;
- to survive in the marine environment under regular operating and maintenance conditions.
We hope that additional industry input and comment while the unit is operating at our research farm in Deep Bay will assist us in suggesting further improvements. We have so far made the following observations presented without order or significance.
- Total Cost of materials so far, about $32,000
- The use of 36volts for the system design significantly reduces the potential components that can be added to the system. We would like to investigate the engineering ramifications of modifying the system to work via 110AC (inverter) or more common 12 Volt.
- With the FLUPSY anchored out on the raft grid, the energy generation system could easily be increased through the addition of a consumer wind turbine system. This is complicated however by the requirement to charge at 36 Volts in the existing configuration.
- Production models of the FLUPSY could benefit from the replacement of our fabricated wood solar panel racking with more commercial aluminium racking products. This could potentially add more flexibility in adjusting for annual changes in sun inclination and direction. This however could be expected to drive construction costs up.
- We used suspended ballast to trim the FLUPSY. We note that ACE Roto-mold provider of the raft floats also makes flotation chambers similar to those used on the CSR raft which may be filled with water or air. These might be a more efficient way of providing and adjusting trim.
- Which is better a vertical axial pump or a paddlewheel? To date we have been able to find no quantifiable information in this regard. In this application we must consider the question in both terms of pumping volume and energy consumption. Hopefully in situ testing at a later date will allow us answer this question.
6.0 STAY TUNED!
We have overwintered the FLUPSY on the farm to test structural integrity and will be adding seed to it shortly. As the project progresses we’ll be reporting back on how it works. We’d really like to hear the feedback from industry on how we might improve the design so far. For more detailed information on the FLUPSY or to get a tour, please do not hesitate to contact us directly: brian.kingzett@VIU.ca
I leave you with some more photos from the project.
Dr. Dale Leavitt and VIU Renewable Energy Program grad Max Meilke (who fabricated the FLUPSY) do some early on-site solar panel placement discussions.
Sarah stands by as the FLUPSY gets launched with no fanfare at all – where’s the champagne?
Sarah and RMOT Practicum student Sean pole the raft out. “just pole the FLUPSY into the bay, we’ll come get you…. really…”
Tied up to the raft grid in Deep Bay Harbour. If you look close, in the distance are three large industry FLUPSY’s tied up together (largest in blue shed).
Much of the credit for the FLUPSY end results goes to Max, who turned the design concepts into fabrication, here shown programming the charge controller.