Note: Descriptions are shown in the official language in which they were submitted.
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MULTILEVEL PHOTOBIOREACTOR
FIELD OF THE INVENTION
The present invention relates to a photobioreactor for production of biomass
and more
particularly to a multi-level shelf-like arrangement of elongate bioreactor
bags or sleeves
being supported horizontally over stretched transparent panels. In an
embodiment of
the invention, the modular bioreactor may be operated inside a warehouse or a
container using artificial light. In another embodiment, the bioreactor
operates inside a
greenhouse using natural light.
DESCRIPTION
This patent application claims the benefit of priority from Canadian Patent
Applications
No. 2,801,768 filed Jan. 25, 2013 and from Application No. 2,764,291 filed
Jan. 16,
2012 through PCT Application Serial No. PCT/CA2012/050750 filed Oct. 22, 2012
and
published W0/2013/082713 on 13 June 2013, the contents of each of which are
incorporated herein by reference.
BACKGROUND
The current energy crisis has prompted interest in altemative energy, bringing
a great
deal of attention to the production of algae biofuels. Beyond biofuels,
commercial algae
farming is also important to medicine, food, chemicals, aquaculture and
production of
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feedstocks. One major obstacle to algae farming is the commercial scale-up for
mass
culture, temperature control of algae and the high cost associated with such a
culture.
The vast number of different bioreactor concepts is testimony that the best
algal farming
bioreactors are still to be found. Most bioreactor designs are not suitable
for commercial
use due to cost and scale-up problems. In contrast with bioreactors, pond
technologies
are commercially viable today, but have well-established problems of their
own.
Integrated technologies might provide the control present in closed
bioreactors and the
scalability provided by open ponds.
In Healthy Algae published by Fraunhofer Magazine, January 2002, it is stated
that
algae are a very undemanding life form - they only need water, carbon dioxyde,
nutrients and sunlight. However, providing sufficient sunlight can be a
problem in large
scale facilities. As the algae at the surface absorb the light, it does not
penetrate to a
depth of more than a few millimeters. The organism inside the unit gets no
light and
cannot grow, explains Walter Troesch, who has been cultivating algae for
years. One of
the problems with growing algae in any kind of pond is that only in the top 1
inch to 4
inch or so of the pond receives sufficient solar radiation for the algae to
grow. In effect,
this means that the ability of a pond to grow algae is limited by its surface
area, not by
its volume.
Given that surface area of an algae container is more important than its
volume, then all
recent and past algae cultivators shall be re-examined in consideration of
said criteria.
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Traditional methods used for culturing autotrophic organisms have involved the
use of
shallow open ponds or open channels exposed to sunlight. Not surprisingly this
comparatively crude method has proved impractical for production of pure high
grade
products because of such problems as invasion by hostile species (sometimes
producing dangerous toxins), other pollution (such as dust and bird
droppings), difficulty
in the control of such variables as nutrient ratios, temperature and pH,
intrinsically low
yield because of escape of carbon dioxide to the atmosphere and inefficient
use of light
to illuminate only the top portion of the biomass.
Somewhat more sophisticated attempts have involved the use of horizontally
disposed
large diameter transparent plastics tubes laid on the ground for biomass
production.
The problems of such a system include the low density of biomass in the liquid
within
the tubes, coating of the pipes by algae due to low velocity flow passing
through, thus
reducing transparency, overheating in summer weather, high land usage and high
energy input to either agitate or move large amount of over diluted water.
To overcome some of the limitations of prior art, patent WO/2013/082713 issued
to the
present author, Mottahedeh, discloses a low-cost photobioreactor that provides
a wide
translucent flexible sheet that is shaped by external brackets to form an
elongate
channel adapted for biomass production therewithin. While an embodiment of
this
patent discloses bioreactor sheets that are shaped and supported in the air by
suspended brackets, the Mottahedeh patent offers only limited compactness not
sufficient for large commercial scale-up on a small footprint.
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A closer look at receptacles disclosed in prior documents and more
particularly for
potential use as low-cost raceway-type pond or as photobioreactors, reveals
that in the
last five decades, since conception of early photobioreactors until now,
people skilled in
the art have strongly discouraged suspending or supporting horizontally-
oriented
structures above ground, particularly carrying heavy loads of liquids over
suspended
structures. This discouragement has been extended even further when liquids
were to
be carried and contained in flexible or semi-rigid containers. Objectors have
argued
that such an undertaking calls for extra support costs, requires additional
structural
stability or may be subject to environmental risks. Exceptionally,
horizontally-oriented
and elevated glass tubes of small diameter and more recently of polycarbonate
material
have been used at laboratory scale or for cultivating expensive microalgae in
few pilot
projects. It is therefore known that capital costs, installation and
maintenance for such
suspended tubular systems are exhorbitant.
Prior attempts to concentrate a large number of bioreactor containers on a
small surface
area include a multilayered photobioreactor disclosed in U.S. Patent 7,618,813
to Lee et
al. which teaches primarily a series of vertical cylindrical photobioreactors
limited to two
or three layers of culture in same containers. It is known that vertical
culture systems
offer a low surface-to-volume ratio in terms of exposure to light. They also
require large
areas of land to be efficiently deployed.
Another attempt to stack multiple bioreactors next to each other is disclosed
by Masse
in U.S. Pat 7,997,025 who teaches an algae production with a harvesting
apparatus.
The disclosed modular production system teaches stackable vertical-type photo-
bioreactor modules adapted for producing algal bioproducts. Vertical, column-
type
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bioreactors are known to require extra pumping pressure to overcome water
pressure
during gasing because of height. It is also known that in such column-type
bioreactors
sparging of C.O2 and 02 at high pressure causes shearing of algae
cells as
well as dead zones below and around nozzles, both sources of added
contamination.
The photobioreactor disclosed by Levin in US Patent Application No.
20070155006
teaches a large number of small troughs constructed from relatively short
profiled units
having bottoms provided with recesses or transverse low partitions. The system
is
provided with feeding pipes having nozzles delivering the microalgae
suspension to the
troughs and a pumping system that feeds the system. Throughs are built on two
parallel
ropes or parallel rods. When troughs are sufficiently rigid, they are
installed at their ends
immediately on the vertical posts without application of the ropes. Levin
further
discloses that the entire set of the vertical rows of the troughs with optical
elements
positioned between these vertical rows can be placed in a greenhouse
construction
which prevents ingress of the dust into the microalgae suspension. This Levin
patent
discloses a system of narrow open troughs suspended to ropes or rods. Despite
its
complexity, troughs are still left open and rely on an external greenhouse
cover to
prevent contamination or cross-contamination.
Accordingly, there is a need for an algae production system suitable for the
mass
production of algae. Addressing such a need requires that past objections and
long
standing prejudices against horizontally supported flexible bioreactors being
suspended
in the air be re-examined.
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What is needed is an apparatus that overcomes the aforementioned limitations,
prejudices and disadvantages of prior art while being cost effective and able
to integrate
the scalability provided by ponds with the controls provided by
photobiorectors.
Preferably, inventive steps disregarding past prejudices would lead to an
apparatus
configured with a large surface-to-volume ratio while erectable on a small
footprint, easy
to maintain, to operate and to scale-up.
SUMMARY OF THE INVENTION
The disclosed bioreactor is generally directed to a modular multilevel photo
bioreactor
suitable for mass culture of algal biomass being either exposed to artificial
light, to solar
light or to a combination thereof.
The modular bioreactor of the invention can be extended longitudinally,
vertically and to
some extend transversally. It features a surface area as large as the number
of its
levels while standing on a footprint equivalent to only a single level.
Each bioreactor level is made of transparent shelves. Depending on the
bioreactor size
and configuration, shelves form collectively one or two flat horizontal
elongate surfaces
over which are laid elongate bioreactor bags or sleeves. Each sleeve
incorporates at
least two sparger tubes, each being alternately pressurized by an aeration
pump. An
electronic switching system turns on and off air pressure between the two
sparger tubes
creating transversal waves, vibrations and agitation along the full length of
the sleeves.
Having intemal sparger tubes built-in into a bioreactor sleeve reduces sources
of
contamination caused by introduction of external sparger tubes. The
compactness
provided by the present multilevel bioreactor improves monitoring and control
of factors
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that influence generally the operation of a bioreactor. Such factors include
temperature,
light, pH, agitation, gas flow and liquid flow and physical factors of the
like.
The bioreactor is expandable with modular components that may be arranged in a
manner that facilitates efficient deployment and maintenance. The unique
arrangement
of its horizontal shelves, each being independently secured, at each rack
level, to
opposite upright posts, avoids the vertical build-up of pressure among
bioreactor
sleeves; this arrangement departs fundamentally from prior art bioreactors
wherein the
taller a bioreactor is raised, the more pressure is required to overcome flow
of gases
needed to feed algae and to agitate the system; this problem affects
negatively all
vertical bioreactors, whether panel-like, column-like, cylindrical-like or bag-
types.
Furthermore, the present multilevel bioreactor takes advantage of gravity ¨ a
medium
entering higher level sleeves may freely flow into lower level bags after
being exposed
to light along the full length of said sleeves while travelling across the
selected
horizontal shelves. This arrangement again saves substantially energy and
costs.
Furthermore, providing a multilevel bioreactor enables to allocate different
processes to
different sleeves located at various levels, all within the same bioreactor.
As an example,
to dewater an algal culture, the cultured algae may be directed towards a
bioreactor
sleeve positioned at a lower level wherein a natural filtration by gravity may
take place.
Thus reducing substantially the amount of energy associated to dewatering.
In an embodiment of the invention, the multilevel bioreactor is operated in a
warehouse,
in a building or fitted modularly to operate a shipping cargo using artificial
light such as
light emitting diodes LED, including embedded LEDs in a mat. In another
embodiment
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of the invention, the multilevel bioreactor is surrounded by a circular-shape
greenhouse
cover in which the lower portion of the cover close to the ground takes on a
parabolic
shape covered by a reflective material.
The advantages of the invention will be set forth in part in the description
which follows,
and in part will be understood from the description, or may be learned by
practice of the
disclosure herein. It is to be understood that both the foregoing general
description and
the following detailed description are exemplary and explanatory only and are
not
restrictive.
BRIEF DESCRIPTION OF THE DRAWINGS
These and other objects and advantages of the invention will become apparent
upon
reading the detailed description and upon referring to the drawings in which:
Figure 1 is a cross-sectional front view of two superimposed sleeves of the
multilevel
photo bioreactor.
Figure 2 is a front view of a multilevel photo bioreactor surrounded by a
greenhouse
cover.
Figure 3 is a perspective view of the bioreactor of Figure 2.
Figure 4 is a cross-sectional side view of a sleeve with a movable roller
separating fluid
content in two portions.
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Figure 5 is a perspective back view of the bioreactor showing replacement
rollers.
Figure 6 is a cross-sectional view of a bioreactor sleeve provided with a
water jacket.
Figure 7 is a cross-sectional view of a bioreactor sleeve provided with a
filter membrane
inside.
Figure 8 is a perspective view of two flexible light emitting diode LED mats.
Figure 9 is a perspective view of a bioreactor fitted into a shipping
container.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS OF THE INVENTION
The present invention best described in FIG. 1 provides a multilevel
photobioreactor
500 comprising an assembly of self-standing modular frames 62 each comprising
a set
of opposite rack uprights 62 having feet anchored to the ground and tops
connected by
horizontal beams.
Multiple levels of transparent horizontal thin hammock-like shelves 82 are
stretched
between said rack uprights 62. Shelves 82 are comprised of transparent, semi-
rigid
plastic sheets having two opposite borders secured to rigid metal profiles by
fasteners
means such as industrial staples. In tum, said rigid metal profiles are
tightly stretched by
fasteners means 94 between rack uprights 62. The degree of stretch of said
semi-rigid
sheets 82 determines the degree of deflection anticipated by the shelf 82
under load
when bioreactor sleeve 100 is loaded.
In a preferred embodiment of the bioreactor 500 as best described in FIG. 2,
multiple
transversally-oriented adjacent shelves 82 form collectively side-by-side at
each level,
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two adjacent columns of longitudinal shelves 82. On these tightly stretched
horizontal
shelves 82 are laid bioreactor sleeves 100, each shelf level being itself
created by
multiple rows of flat horizontal stretched panels 84; each shelf 82 being
adapted to
support a wide elongate sleeve or bag 100 that contains an algal medium. In
between
columns, a repeating number of vertical perforated plates supports horizontal
elongate
middle bars 64 to support load at the center of panels 84.
In another embodiment of the invention, longitudinally-oriented panels 84 form
collectively at each level, a single column, each including multiple levels of
flat
horizontal elongate surfaces or shelves 82; each shelf 82 adapted to support a
wide
elongate sleeve or bag 100 that contains an algal medium.
Sleeves 100 are preferably made of an upper 14 and a lower 12 light-
penetrating
transparent or translucent layer of flexible plastic sheets having their
longitudinal edges
sealed together for creating a container means 100 adapted for biomass
production. In
the preferred embodiment of the invention, the bottom sheet layer 12
incorporates two
sparger tubes 22 and 24 for dispensing gases along the sleeve 100 full length.
Sparger
tubes 22, 24 are shaped by respectively folding, perforating and sealing a
sleeve 100
bottom member portion 12 along the full sleeve member 100 length.
It is known that in any photosynthetically-driven algae farming system, proper
agitation
of algal medium is critical to expose all algae cells to light, no matter
medium depth.
Traditionally, substantial amount of energy is allocated to agitation of the
algal medium.
To reduce this energy consumption, the present invention discloses two low
energy
agitation systems.
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In a first embodiment of the agitation system, an algal medium 42 contained in
sleeve
100 is agitated by gases. This is achieved by alternately pressurizing each of
the two or
more sparger tubes 22, 24 provided with their own holes 17 positioned at the
bottom of
the sleeve member 12. Pressure variation in sparger tubes 22, 24 creates a
transversal
harmonic agitation along the full length of sleeve 100 creating waves that mix
intimately
gases with the algal medium.
In a second embodiment of the agitation system, physical vibration of air
exiting from
sparger tubes 22, 24 is used as a source of agitation, adding to the agitation
created by
bursting bubbles 32 that exit from same tubes 22, 24. To increase vibration, a
pressure
pulsation similar to "water-hammer" in liquids is created in sparger tubes 22,
24.
Vibrations may be also be generated using a venturi effect caused by releasing
a
pressurized but un-even air flow via small orifices positioned along the two
sides of the
thin air sparger tubes 22, 24 positioned under algal medium.
Volume and pressure fluctuation of gases generated in sparger tubes 22, 24 is
created
by adding to an air or carbon dioxide gas delivery system a means such as, but
not
limited to, modified diaphragm, a floating tongue, an unbalanced or balanced
rotor, an
unbalanced or balanced propeller, an electrically-driven modulator or a
combination
thereof.
As shown in FIGS. 1, to remove oxygen from the bioreactor sleeve 100, at least
one
elongate border portion of sleeve 100 is elevated above fluid level and
secured to a
railing-type support 92. This creates space for vents to be inserted into the
bioreactor
sleeve 100 to vent excess gases. To achieve this, a folded portion of the
sleeve walls
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12, 14 is sealed and laced with a rope-like filler that can be removably
engaged in
railing 92 attached to the side of an upper shelf located just above shelf 82
that supports
said sleeve 100. The filler means includes foam rope, plastic rope, jute rope
and cotton
rope. Such an arrangement makes installation, retrieving and maintenance of
sleeves
100 easy.
In an embodiment of the invention, the multilevel photobioreactor 500 includes
a source
of artificial light such as LED tapes 202, LED bars, LED lamps or LED mats 210
as
shown in FIG. 7. These are positionable under, above or at the side of sleeve
members
100 or according to a combination of said locations.
The source of light may also include solar light in combination with
artificial light. In a
preferred embodiment the light source, multiple parallel rows of light
emitting diodes
LED are positioned over a mat 210. They are provided with select wavelengths
that
enhance algae growth. They are either embedded, sandwiched and laminated
between
two transparent films to form collectively a wide, flexible, modular
transparent mat 210
that may be electrically connected via connectors 212 among themselves and
powered
by an electrical source.
Fluid level and flow from one or multiple sleeves 100 located on a higher
shelf 82 to
sleeves located on lower shelves 82 may be controlled via height-adjustable
fluid exit
means 19 such as height-adjustable overflow valves 19 to establish the desired
level of
fluid in each sleeve 100 before extra fluid overflows to another destination;
said valves
19 being positioned at one or both ends of each sleeve 100.
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To engage different individual or groups of sleeves 100 to perform different
tasks or
processes in a same multilevel bioreactor 500, valves 19 may be opened or
closed
manually or automatically enabling fluid flow in a sleeve 100 in a vertical
downward
direction, in a horizontal sideway direction from left to right or vice-versa,
or follow a
pattern programmable by a controller means (not shown). As an example, six
upper
levels of sleeves 100 may be engaged in culture of an algae species receiving
air,
C.O2, agitation and nutrients, whereas three lower levels of algal medium
may be
cut off from air and nutrients to undergo a starvation process forcing them to
transform
their biomass into oil, and finally three lowest levels may be used as
transfer containers
to maintain continuity of the process.
Thus, having multiple sleeves 100 so densely located next to each other
enables to
subject algae to collaborative processes including extreme environmental
conditions
and shocks that stimulate algae growth. Such environmental treatment may
include
subjecting them to high or low electromagnetic fields, high or low flashes of
light, flashes
of heat, exposure to sound waves, and a combination thereof.
Providing sleeves 100 whose weight is independently carried by shelves 82
which are in
turn affixed to the rack system 62 eliminates transfer or accumulation of
weight or fluid
pressure being exercised on lower sleeves 100. This eliminates the need for
pumps to
operate under higher pressures such as for aerating the bioreactor system 500
or
displacing fluids. This saves energy and reduces substantially operation
costs.
In the present photobioreactor of the invention 500, biofilm or deposits from
sedimentation in sleeves 100 may be removed by displacing manually,
automatically or
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by pressure differential means a movable cleaning pig (not shown) in the
sleeve 100. To
achieve this, a mop-shape cleaning pig attached to two ropes, one on each side
of the
cleaning pig, may be pulled.
In an embodiment of the bioreactor exposed to solar light 1000, to prevent
photo
inhibition, the transparent or translucent material that composes the sleeve
100 may be
adapted to allow only photosynthetically active radiation (PAR) wavelengths of
about
400 nm to 700 nm to reach an algal medium contained in the sleeves 100.
In the preferred embodiment of the bioreactor 500, the sleeves 100 are sized
to be
about 0.5m to about 4m wide, but preferably about 1.2m to about 2,4m wide;
rack
uprights 62 are about 50cm to about 6m high but preferably about 2.4m to about
3.6m
high; bioreactor 500 length extends between about 1.2m to about 100m long but
are
preferably about 2.4m to about 50m long.
The photobioreactor 500 is provided with about 2 to about 40 levels of shelves
82, but
preferably about 19 to about 30 shelf levels; each panel 84 making
collectively shelves
84 is substantially about 0.010" (0.254mm) to about 0.080" (2.032mm) thick,
but
preferably about 0.02" (0.508mm) to about 0.03" (0.762mm) thick; and the
elongate
sleeves 100 are about 2 Mil (50.8micron) to about 12 Mil (304.8micron) thick
but
preferably about 4 Mil (101.6 micron) to about 8 Mil (203.2micron) thick.
In another embodiment of the bioreactor 500 shown in FIG. 7 the sleeve member
100 is
comprising, in addition to an upper 14 and a lower 12 flexible sheet portion,
a middle
detachable filter sheet portion 16 adapted to dewater the algal medium and
retain a thin
layer of biomass body above the filter sheet 16 when ends or bottom of said
sleeve
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lower sheet portion 12 is opened, enabling fluid contained in the sleeve
member 100 to
escape and, or be recycled.
In yet another embodiment of the sleeve member 100, the sleeve member has a
middle
filter sheet portion 16 adapted to be disconnected from the sleeve upper 14
and lower
sheet portions 12 and can be carried away by a conveyor belt into a heating
zone able
to dry and transform said biomass into thin peelable biomass crust.
In an embodiment of the multilevel photobioreactor 500 shown in FIG. 5, a
biomass
dewatering system 400 is further provided. The dewatering system 400 is
comprising an
elongate motorized conveyor belt located in a trough 420 that is positioned at
the lowest
level of bioreactor 500; the belt of the conveyor also functions as a filter
16 adapted to
receive and partially dewater biomass. Filter / belt 16 is being exposed to a
heating
zone that dries and transforms the thin layer of biomass into a peelable crust
collected
by gravity.
Bioreactors 500 of the inventions have tightly stretched shelves 82 or panels
84 that
may support one or two lines of elongate sleeve members 100. When two lines of
sleeve members are laid on shelves 82 or on panels 84, a central support
system 64 is
being provided.
While some embodiments of bioreactor 500 are adapted to operate indoor, inside
a
warehouse, a shipping container 600 (see FIG. 9) or inside any other closed
structure or
building; other embodiments of bioreactor 500 are configured to operate
outdoor,
protected from weather conditions under structures such a greenhouse 1000 or
an
inflatable structure. In such a configuration, the elongate bioreactor 500 is
located at
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the center of the tunnel-shape greenhouse 1000 with the cover being adapted to
provide optimum photosynthetically active radiation (PAR) within wavelengths
ranging
about 400nm to 700nm with about 95% light diffusion; the lower portion of the
greenhouse 1000 is provided with a reflective portion 210 having a parabola-
shape
configuration. The reflective material 210 may be flexible or semi-rigid and
is adapted to
reflect incoming light towards sleeves 100.
In an embodiment of the invention (FIG. 5), replacement of disposable or re-
usable
bioreactor container means or sleeves 100 is made easy by providing a stand
(not
shown) holding multiple rollers 18; the stand is located at one end of
bioreactor 500 for
holding a supply of rolls 18 of flexible container means 100; pulling out,
from one end
of bioreactor 500 a container means portion 100 causes a supply of fresh
container
means portion 100 to be dispensed from a corresponding roll 18 located at the
other
end of bioreactor 500; thus an empty or partially dewatered container means
portion
100 may be easily and readily (after dewatering) replaced by a fresh un-
contaminated
container means portion 100. Replacement of an older container means may take
place because of damage, leakage, contamination, wear and tear, loss of
clarity or as
part of a processing step wherein biomass contained in the container means 100
may
be collected and further processed.
As an example of a processing step, a dewatered container means portion 100
may be
gradually pulled out of the bioreactor shelves 82, sealed and then separated
into small
packages; this guarantees avoidance of contact with air or other extemal
sources of
contamination. In a further step, the sealed packages may be safely
transported, frozen
or directly sold to consumers or to buyers.
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The bioreactor of the present invention 500 provides a controlled environment
in which
multiple parallel or serial processes may occur within a container means 100
of
bioreactor 500 itself or in association with equipment and accessories that
are in air or
fluid communication with container means 100 or are introduced in said
container
means 100. As an example, in the present invention internal layers of said
container
means 100 may function as filtering membranes 16 having their own sparger
tubes 22,
24 with holes 17 along their full length. When dealing with fluids of
different densities,
intemal layers may transfer or filter fluids via osmosis or reverse osmosis.
In another
example, introducing venturi jets into the algal medium creates micro bubbles
that
separate solids from liquids and lift agglomerated cells to the fluid surface
making
harvesting of microalgae easy as a simple skimming process. Other processing
steps
within the bioreactor container means 100 may include electro flocculation,
bioflocculation, blofloatation, fermentation, lysing, hydrogenation, localized
heat
treatment, localized light flash treatment, localized high or low magnetic
field treatment;
some of said processes causing stresses that may increase biomass productivity
or
influence it; yet another example include oil extraction by fracturing cells
walls with
cavitational micro-bubbles, and a combination of multiple processes mentioned
before.
The multilevel photobioreactor 500 is best made of at least one of the
materials selected
from the group consisting of: fiber reinforced plastic, low density
polyethylene, high-
density polyethylene, nylon, hard acrylic, polyvinyl chloride, polycarbonate,
composite
plastic, ethylene vinyl acetate, fiber glass, woven fabrics, non-woven fabrics
and a
combination thereof.
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In an embodiment of the photobioreactor 500, the modular bioreactor 500 is
encased
and installed in a steel structure such as a shipping container 600; grouping
multiple
shipping containers 600 together scales-up fast installation of bioreactor
500.
In yet another embodiment of invention 500 shown in FIG. 6, thermal control of
the
bioreactor 500 is provided by circulating a cooling or heating fluid 40 in a
water jacket
20; the water jacket 20 is created by positioning an elongate bag 120
longitudinally just
below panels 84 and above a surface created by a repeating number of modular
supports 86. Supports 86 are simply made by doubling panels 84 with a slight
difference.
While they share same two opposite borders and respective holding attachments
for
tightening them, upper panels 84 are tightly stretched while lower panels 86
are loosely
stretched and secured to opposite rack uprights 62; the upper tightly
stretched panel 84
is sized to be of slightly shorter length that of the lower loosely stretched
panel 86; in
such an arrangement, lower loosely stretched panels 86 form collectively an
elongate
surface 88 over which may be extended a long flexible or semi-rigid shallow
chamber or
jacket 20. Circulating a slightly pressurized hot or cold fluid 40 in said
shallow chamber
20 causes chamber 20 to press upwardly against the bottom of the upper tightly
stretched panel 84 and exchange its heat or cold with bioreactor sleeve 100.
Depth of
said shallow chamber 20 may vary between about 10mm to about 50mm at its
lowest
point.
In another embodiment of the invention, cooling of bioreactor 600 is achieved
by
evaporating dew very slowly seeping out from bioreactor container means upper
wall 14.
To optimize cooling by evaporation, the container means 100 is having,
preferably a top
wail 14, a bottom wall 12, or both walls 12, 14 made of a transparent
waterproof
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material that is breathable to enable very slow evaporation of condensates
under a
warm climate.
To expand inoculum gradually, controllably and safely without being exposed to
contamination, mainly during traditional transfer of medium to larger
containers has
been a challenge among algae farmers. To overcome this challenge, the present
bioreactor 500 provides an external movable divider 310 that enables a full
volume of
medium 42 contained in each of the container means 100 to be divided, then
isolated
and then expanded in a controlled manner; control of expansion being achieved
by
simple rolling or sliding one or multiple movable dividers 310 that are
positionable under
walls 12 and 14 of the flexible container means 100; said dividers 310
elevating and
isolating a portion of said container means 100 include, but not limited to,
movable
rollers 310, liftable bars, roller-over-bars, stretchable bungees, ropes,
cables, raisable
panels, slidable self-standing dividers and a combination thereof.
To channel and collect water from spills or leakage from the bioreactor
container means
100, a waterproof sheet positioned at the lowest level of the bioreactor 500
is provided
with elongate borders being loosely stretched between the bioreactor opposite
rack
uprights 62; said waterproof sheet is further provided with a drainage means
connected
to hoses that carry water spills away.
The scope of the claims should not be limited by the preferred embodiments set
forth in
the examples, but should be given the broadest interpretation consistent with
the
description as a whole.
