U.S. patent application number 14/229845 was filed with the patent office on 2014-07-31 for construction material made of algae and method for producing thereof.
The applicant listed for this patent is Heinz Ploechinger. Invention is credited to Heinz Ploechinger.
Application Number | 20140212955 14/229845 |
Document ID | / |
Family ID | 45097383 |
Filed Date | 2014-07-31 |
United States Patent
Application |
20140212955 |
Kind Code |
A1 |
Ploechinger; Heinz |
July 31, 2014 |
CONSTRUCTION MATERIAL MADE OF ALGAE AND METHOD FOR PRODUCING
THEREOF
Abstract
The present disclosure describes use of filamentous algae to
form insulating construction materials which provide thermal and
noise insulation. Algae from the order Zygnematales, the
Cladophorales, or the Ulotrichales can be dried and formed for use
as insulating material. Algae mass can be combined into several
layers, using a binder to attach the layers to each other. A
composite material of algae mass and an additive can be used and
form the body of insulation panels having honeycomb-shaped
chambers, which are sealed by a foil that is laminated onto the
body.
Inventors: |
Ploechinger; Heinz;
(Freinberg, AT) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Ploechinger; Heinz |
Freinberg |
|
AT |
|
|
Family ID: |
45097383 |
Appl. No.: |
14/229845 |
Filed: |
March 29, 2014 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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13083519 |
Apr 8, 2011 |
8685707 |
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14229845 |
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61354665 |
Jun 14, 2010 |
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61380253 |
Sep 5, 2010 |
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Current U.S.
Class: |
435/257.1 |
Current CPC
Class: |
E04C 2/16 20130101; Y10T
428/24149 20150115; E04B 2001/748 20130101; C12N 1/12 20130101;
B32B 2307/102 20130101; B32B 7/03 20190101; B32B 9/02 20130101;
B32B 2307/50 20130101; B32B 2471/04 20130101; B32B 2307/206
20130101; E04B 1/90 20130101; A01G 33/00 20130101; B32B 2553/00
20130101; Y10T 428/24124 20150115; B32B 5/12 20130101; Y10T 428/239
20150115; B32B 2419/00 20130101; B32B 2307/5825 20130101; E04C
2/365 20130101; B32B 3/12 20130101; E04B 1/7604 20130101; Y02A
40/80 20180101; B32B 2262/101 20130101; Y02A 40/88 20180101; B32B
1/06 20130101; Y10T 428/24157 20150115 |
Class at
Publication: |
435/257.1 |
International
Class: |
C12N 1/12 20060101
C12N001/12 |
Claims
1. A construction material made of algae, comprising: a first layer
of filamentous string-shaped algae having a first predominant
orientation and a second layer of filamentous string-shaped algae
having a second predominant orientation, wherein the first layer
and the second layer are connected to each other by a binder and
arranged such that the first predominant orientation and the second
predominant orientation are non-parallel.
2. The construction material as in claim 1, wherein the first
predominant orientation and the second predominant orientation are
about perpendicular to each other.
3. The construction material as in claim 1, further comprising a
third layer of mesh-structured filamentous algae arranged between
the first layer and the second layer.
4. The construction material as in claim 3, wherein the first layer
and the second layer comprise algae of the order Zygnematales and
wherein the third layer comprises algae of the order
Chlorococcales.
5. The construction material as in claim 1, further comprising an
additive of silicic acid or diatom algae particles.
6. The construction material as in claim 1, wherein the first layer
of filamentous string-shaped algae and the second layer of
filamentous string-shaped algae comprise pyrolyzed filamentous
algae.
7. A method for producing for a construction material made of
algae, comprising: harvesting algae; drying the algae to form a
dried algae mass; placing the dried algae mass into a sealed
container, the algae mass being held by mounting fixtures at both
ends of the sealed container; holding the algae mass under tension
by the mounting fixtures; heating and evacuating the sealed
container; allowing the algae mass to carbonize; and removing
carbonized algae material from the container.
8. The method as in claim 7 wherein heating the sealed container
occurs in several steps, between 600.degree. C. and 900.degree.
C.
9. The method as in claim 7 wherein the dried algae mass comprises
cells having a predominant orientation and wherein the dried algae
mass is placed into the container such that its cells are
predominantly oriented parallel to the tension created by the
mounting fixture, thereby causing a predominant orientation of
carbon fibers in the carbonized algae material.
10. The method as in claim 9, further comprising: soaking two mats
of carbonized algae material in a binding agent and placing the two
mats onto each other such that the predominant orientation of
carbon fibers in each mat is substantially perpendicular to each
other.
Description
TECHNICAL FIELD
[0001] The present disclosure relates to construction materials
made of algae and methods and plants for production thereof.
BACKGROUND
[0002] Algae are known to be used as fertilizer, as food, and as a
pollution control in sewer plants. Recently, their ability to
produce more biomass per unit area in a year than any other form of
biomass has increased interest in algae as a renewable energy
source. Cultivating algae for this purpose usually involves algae
species that can produce algae oil and requires closed containers,
a tightly controlled environment, and sophisticated process
technology. Chlorella, a genus of single-celled green algae, has
been used for fuel production. The presence of other algae,
especially fast growing hair algae, is undesirable in such algae
fuel plants.
[0003] Some algae, e.g. those of the Cladophora, have been used in
fire retardant building material known in German as "Algilit".
"Algilit" is known to having been used in western Siberia for many
years. Algal plastics which comprise a foamed and stabilized
filamentous algal fiber matrix having substantial dimensional
stability are disclosed in U.S. Pat. No. 5,779,960.
[0004] Carbon dioxide is considered a green house gas, increasing
concentration of which in the earth's atmosphere leads to a rise in
global temperature levels, an effect often referred to as global
warming. A reduction in carbon dioxide emissions is deemed
desirable. Ideally, the concentration of carbon dioxide in the
atmosphere would be kept constant or even reduced, by permanently
withdrawing carbon dioxide from the atmosphere at the same or at a
faster rate than carbon dioxide is emitted into the atmosphere.
However, reducing or eliminating the emission of carbon dioxide
that is generated by fossil fuel power plants such as coal, oil or
gas power plants, has proven to be difficult, inefficient, and
expensive. The ability to reduce carbon dioxide emissions is
however of particular interest in jurisdictions that regulate
carbon dioxide emissions, including taxing such emissions, for
example by requiring an emitter to purchase carbon dioxide emission
rights.
[0005] One approach to reducing carbon dioxide emissions from
fossil fuel power plants is to pump carbon dioxide that is
generated in power plants into underground storage, e.g. caverns or
retired mines. However, this approach is expensive and potentially
dangerous, if carbon dioxide escapes from its underground
storage.
[0006] Another approach is to switch power generation plants from
fossil fuels to renewable fuels, thereby reducing the dependency on
coal, oil and gas as energy sources. However, renewable energy
sources from crop compete with crop needed as food, are
inefficient, and can at best case be carbon neutral. Burning
renewable energy typically emits about the same amount of carbon
dioxide that the underlying crop has withdrawn from the atmosphere
during its growth. A reduction of the carbon dioxide in the
atmosphere is not possible.
SUMMARY
[0007] The present disclosure reveals a new use for filamentous
algae which are produced in cultivation pools filled with
pre-treated waste water and into which carbon dioxide is injected
to create insulating construction materials. It has been found,
that dried algae mass can be used to form construction material,
especially thermal and noise insulation material. The filamentous
algae used in construction material bind carbon dioxide,
permanently removing it from the earth's atmosphere. Construction
material comprising filamentous algae is hence eligible to receive
credits for carbon dioxide reductions, where such credits are
legislated. The disclosed construction material comprises at least
20% of dried filamentous algae mass, but may consist of up to 100%
of dried algae mass.
[0008] Suitable algae for use in construction material are
filamentous species, which grow in strings of connected cells.
Filamentous algae may be branching, or non-branching, and may be
referred to as hair algae or string algae.
[0009] Several genera of green algae from the order Zygnematales
have been found suitable for use in construction. More
specifically, species from the genera of the Spirogyra, the
Zygnema, and the Mougeotia, have all been found to have desirable
characteristics for use in insulation material.
[0010] Other suitable algae are species from the Cladophora, a
genus of reticulated filamentous green algae from the order of
Cladophorales, specifically the Cladophora fracta. Species from the
Ulothrix, from the order of Ulotrichales, have also been found
suitable for construction use. Hydrodictyon of the family
Hydrodictyaceae from the order Chlorococcales are suitable due to
their usually pentagonal or hexagonal mesh that they form.
Cladophorales, Ulotrichales, Oedogonium, Chlorococcales and
Zygnematales are all green algae from the class of Chlorophyceae.
Klebsormidium is a green algae of the class of Klebsormidiophyceae.
Vaucheria, a genus of Xanthophyceae or yellow-green algae,
characterized by multinucleate tubular branches lacking cross walls
have also been found suitable for use in construction material.
[0011] Further usable as a filler within construction material are
species from the Aulacoseira from the order of Aulacoseirales,
species of the Melosira from the order of Melosirales, species from
the Oscillatoria from the order of Nostocales, as well as species
within the order of Tribonematales. Aulacoseirales and Melosirales
belong to the class of Coscinodiscophyceae, Nostocales to the class
of Cyanophyceae and Tribonematales to the class of
Xanthophyceae.
[0012] The disclosed filamentous algae are relatively easy to
cultivate and harvest. When dried, the resulting algae mass forms a
material that has good thermal insulation characteristics.
Beneficial thermal insulation properties are caused by small
cavities within the algae mass. These cavities are small enough to
not allow any significant convective heat transfer. Also, the
disclosed algae comprise hollow cores, which act as natural
insulation. The insulating characteristic of these hollow cores is
similar to small cavities that can be found in the hair of polar
bears or chamois, causing their fur to be insulating and allowing
them to survive in very cold environment.
[0013] The species or combination of species of algae that is best
used for producing insulation material depends on several
environmental factors, such as for example temperature, sun
intensity, and water hardness. Hence, it is desirable to analyze
regional environmental factors to decide the most suitable species
of algae or combination of species of algae that can be optimally
grown at a given location.
[0014] The disclosed construction material made of dried algae mass
is naturally self-extinguishing, in spite of a relatively high
carbon content. This makes the disclosed material ideal for use in
construction, where fire retardant characteristics are
important.
[0015] While filamentous green algae species form the basis of the
disclosed construction material, filler material may be used to
fill small cavities within dried mass of filamentous green algae.
Filler material may for example be amorphous silica which is added
as a powder to the green algae mass. Another suitable filler
material is diatom algae mass. Diatom algae may be grown jointly
with the filamentous species for use in construction material.
Especially diatom algae species of the Aulacoseirales and
Melosirales whose cell wall comprises silicon dioxide (silica) form
a desirable filler, which increases the self-extinguishing
capability of the resulting construction material. By jointly
growing filamentous and diatom algae, the diatom algae naturally
adhere to the filamentous species, so they can easily be dried and
processed with the diatom species.
[0016] Algae that are harvested from a cultivation plant must be
cleaned and dried before they can be formed into construction
material. Drying can be achieved simply by natural air drying,
preferably leaving the wet algae mass exposed to sunlight.
Alternatively, the algae mass can be convectively dried using hot
air. The algae mass can also be vacuum dried or freeze-dried
(lyophilized. Vacuum drying, in which the wet algae mass is heated
while vapor is removed through a vacuum system, is especially
beneficial, as it promotes the generation of small cavities within
the dried algae mass, thereby improving its thermal insulating
capability.
[0017] Dried algae mass is processed for use in various
applications, such as for example to form upholstery material,
insulating or noise-absorbing mats, fleece, packaging material, and
textiles. Algae-based products are suitable for use in construction
and automotive, among others. In some applications, dried algae
mass, which forms a fibrous web, may be used directly, simply by
cutting or otherwise forming it into a desirable shape.
[0018] For use in other applications the dried algae mass is
further processed. Dried algae mass may be wrapped with a wrapping
material, so that the dried algae mass is mechanically and
chemically protected. Additionally, the dried algae mass may be
coated with silicon dioxide, before being wrapped.
[0019] A composite material may be formed by combining dried algae
mass with an additive, e.g. Epoxy. The consistency of dried algae
material may also be affected by adding a binding agent such as
potato starch or corn starch. An exemplary composite material
comprises pieces of isotropic green algae, which are attached to
each other by a binding agent. Gas bubbles may be injected into the
composite material to increase its thermal insulation
capability.
[0020] Several layers of dried algae mass may be used to form a
multi-layer structure, the layers being connected to each other by
a binding agent. To form a mechanically strong composite material,
algae having a predominant orientation may be used in several
layers. The algae in each layer are preferably arranged such, that
their predominant orientation is non-parallel, and preferably
approximately perpendicular to each other. An exemplary
construction material comprises two layers of algae from the
Zygnematales, their predominant orientation being approximately
perpendicular to each other, and one layer of algae from the
Chlorococcales, for example Hydrodictyon, which have a mesh-like
structure.
[0021] Dried algae mass can be used to form insulation panels. The
insulation panels preferably have a body made of 20% or more dried
algae mass. The body is shaped to form honeycomb-shaped chambers,
which are sealed by a foil that is attached to, e.g. laminated
onto, the body.
[0022] Depending on the desired characteristics of the insulation
panel, the honeycomb-shaped chambers may be evacuated, or may be
filled with various materials. Evacuation or filling with dried
algae mass produces insulation panels having good thermal
insulation. Sand, gel, or other noise-absorbing filling materials
may be used to provide good noise insulation (noise attenuation)
characteristics.
[0023] Insulation panels may be constructed of two or more layers
comprising honeycomb-shaped chambers. Each layer may be dedicated
to a particular purpose. For example, the chambers in a first layer
may be evacuated to provide good thermal insulation, whereas the
chambers in a second layer may be filled with sand to provide good
noise insulation.
[0024] Dried algae mass can further be converted into carbon fiber
material through pyrolysis, creating mechanically strong carbon
fibers from dried algae. Among many potential uses for
pyrolytically created carbon fiber material made of algae mass is
use as an additive in insulation materials to create tarnish
capable of absorbing infrared radiation. Layers of pyrolyzed green
algae may be combined by adding a binding agent as described with
reference to non-pyrolyzed algae mass above.
[0025] Algae mass for use in construction is produced in algae
cultivation plants. Algae need water, carbon dioxide (CO.sub.2),
light, and nutrients to grow. Those are provided in an open algae
cultivation pond, which is exposed to the sun. The algae
cultivation pond is filled with water suitable for growing algae,
for example pre-treated waste water from a sewer plant. Pre-treated
waste water has at least gone through a mechanical cleaning
process, during which solid contaminants have been removed from the
waste water. Carbon dioxide is injected into the algae cultivation
pond through a gas inlet. The carbon dioxide may be extracted from
the flue gas of a fossil fuel fired power plant, or from exhaust
gas of any other fuel burning facility. Alternatively, flue gas
that is rich in carbon dioxide from a fossil fuel fired power plant
may directly be injected into the algae cultivation pond without
prior extraction of carbon dioxide there from. A gas is considered
rich in carbon dioxide, if the concentration of carbon dioxide
therein is at least 0.1% by volume. This equals about three times
the concentration of carbon dioxide that is naturally occurring in
the atmosphere, which is approximately 0.0387% by volume. The
amount of carbon dioxide that is injected into the algae
cultivation pond is electronically controlled using a
microcontroller and sensors. Electric conductivity of the water is
measured by sensors to determine the amount of nutrients in the
water. An exemplary value of the minimal amount of phosphorus (P)
needed to grow algae is 10 .mu.g P/l. For optimal growth 5-10 mg
P/l are needed. The consumption of phosphorus with a full day of
solar radiation is about 250-500 mg P m.sup.2/day. Algae grow in
the algae cultivation pond when it is exposed to sunlight,
typically at a rate up to 100 times faster than other known
renewable resources.
[0026] When a sufficiently thick layer of algae slick has formed in
the algae cultivation pond, the algae are automatically harvested.
The thickness of an algae slick floating in an algae cultivation
pond is determined by sensors, which sense the amount of light
transmitted through the algae slick by comparing a light intensity
reading above and below the algae slick in the algae cultivation
pond. If the thickness of algae slick has reached or exceeds a
predetermined threshold, the algae are harvested, preferably
automatically.
[0027] Several alternative concepts for harvesting algae, referred
to as gravitational harvest, net harvest, rake harvest, circulation
and overflow harvest and a harvesting machine are disclosed.
[0028] Algae cultivation plants employing gravitational harvest
utilize an algae cultivation pond which has a sloped floor and a
pivotable dam wall at its deep end. During an algae growth period
the dam wall is closed, and the pond is filled with water that has
a high concentration of phosphates, nitrates, and other nutrients,
allowing algae to grow. To harvest algae from the algae cultivation
pond its pivotable dam wall is opened, allowing the content of
algae cultivation pond to flow down along the sloped floor into a
lower reservoir. A grill located above the lower reservoir
separates the algae mass from water, making it possible to reuse
the water for a next growth cycle, while extracting the algae mass
from the grill. Also, the algae mass may be allowed to dry on the
grill. Subsequently algae mass may be collected from the grill, and
subsequently dried, and processed into thermal insulation material
or padding material. Two of more algae cultivation ponds may form a
cascading set of algae cultivation ponds, wherein water and algae
flow from an upper pond into a lower pond, when the pivotable dam
wall of the upper pond is opened.
[0029] Algae cultivation plants based on net harvest comprise an
algae cultivation pond, into which a net is lowered at the
beginning of an algae growth cycle. Algae grow in the algae
cultivation pond above the net. Net positioning sliders position
the net in a submerged position at the bottom of the algae
cultivation pond while algae are growing above the net. Algae are
harvested by lifting the net positioning sliders into an upper
position, allowing the net to emerge. Next, the net is pulled,
conveying the algae from the cultivation pond to an adjacent
collector reservoir, where the algae mass is allowed to dry on the
net.
[0030] An algae cultivation plant based on circulation harvest
comprises an algae cultivation pond which is surrounded by a wall.
A circulation water inlet located at one end of the algae
cultivation pond, and overflow rim located at the opposite end. The
top of the overflow rim is the lowest point of the wall surrounding
the algae cultivation pond, so that any excess water flows out of
the algae cultivation pond over the overflow rim. The overflow rim
comprises a sloped wall, so that the speed of water flowing over
the rim successively increases until it flows over the rim. A
conveyor system is located in a collector reservoir adjacent to and
underneath the overflow rim. During operation, water circulates
from a collector reservoir underneath the conveyor system through
the circulation water inlet into the algae cultivation pond, and
across the overflow rim back into the collector reservoir. Algae
slick floating with the circulating water flows across the overflow
rim, and lands on the conveyor system, where it is separated from
the water. The algae mass is conveyed by the conveyor system to a
collection location for further processing.
[0031] The algae cultivation plant based on circulation harvest can
be operated in a continuous operating mode, wherein the water level
in the algae cultivation pond is kept high, so that algae
continuously flows across the overflow rim onto the conveyor
system. The plant can also be operated in a burst mode, wherein the
water level in the algae cultivation pond is kept below the
overflow rim during an algae growth phase and wherein water is
added to the algae cultivation pond during a harvest phase, causing
algae growing in the algae cultivation pond to flow across the
overflow rim and onto the conveyor system.
[0032] An algae cultivation plant based on rake harvest comprises
an algae cultivation pond surround by a wall. An overflow rim
located at one end of the algae cultivation pond, the top of the
overflow rim being the lowest point of the wall surrounds the algae
cultivation pond. A conveyor is located in a collector reservoir
adjacent and underneath the overflow rim. A floating rake, which is
attached to a pulley system, is used to pull algae slick growing in
the algae cultivation pond across the overflow rim and onto the
conveyor.
[0033] In another alternative, algae growing in an algae
cultivation pond can be harvested by an algae harvesting machine,
which moves across a long and narrow algae cultivation pond. As the
algae harvesting machine moves across the pond, algae slick is
lifted from the surface of the algae cultivation pond and conveyed
for collection outside the pond. The harvesting machine uses a
harvesting barrel having circumferentially and axially spaced
spikes to lift the algae slick from an algae cultivation pond. A
conveyor barrel, located adjacent to the harvesting barrel,
transports the algae slick from the harvesting barrel to a slide.
At the bottom of the slide is a conveyor belt for moving the algae
slick for collection outside of the algae cultivation pond.
[0034] Algae mass produced in an algae cultivation plant can be
weighed on a scale to calculate the amount of carbon dioxide that
is bound in the algae mass. The amount of carbon dioxide that has
been absorbed in the algae can be calculated by multiplying the
dried mass of the algae mass with a multiplication factor, which is
specific for each species of algae, and generally around two. The
bound carbon dioxide mass may be reported to obtain tax credits,
carbon emission certificates, or any other financial benefit.
[0035] The disclosed algae cultivation plants are based on a common
method for producing green algae mass, which comprises several
steps. A first step is to provide an algae cultivation pond filled
with water in which the green algae can grow. Algae or algae spores
are provided in the algae cultivation pond to start the growth of
algae. The algae cultivation pond may for example comprise spikes
to which a small amount of algae attach and remain attached even
when algae are harvested from the algae cultivation pond. The algae
attached to the spikes provide a basis for successive harvest
cycles. The algae cultivation pond is filled with water and exposed
to sunlight, allowing algae to grow therein. To foster algae growth
carbon dioxide from an exhaust gas of a fuel burning facility is
injected into the algae cultivation pond. Alternatively, carbon
dioxide may be injected into water outside the algae cultivation
pond, and the carbon-dioxide saturated water inserted into the
algae cultivation pond. The growth of algae in the algae
cultivation pond is sensed, and algae are harvested from the algae
cultivation pond when a sufficiently thick layer of algae has
formed. Harvested algae are dried to form a green algae mass, for
example by air-drying, freeze drying, or vacuum drying.
[0036] Nutrients to facilitate algae growth may be provided by
injecting pre-treated waste water into the algae cultivation pond.
Algae mass may be weighed and an amount of carbon dioxide absorbed
within the green algae mass may be calculated for the purpose of
obtaining a financial benefit associated with reducing carbon
dioxide emissions into the atmosphere, e.g. to avoid having to
purchase carbon emission certificates.
[0037] The following detailed description of the invention is
merely exemplary in nature and is not intended to limit the
invention or the application and uses of the invention.
Furthermore, there is no intention to be bound by any theory
presented in the preceding background of the invention or the
following detailed description of the invention.
BRIEF DESCRIPTION OF THE DRAWINGS
[0038] FIG. 1 shows an algae cultivation plant.
[0039] FIG. 2 is a schematic illustration of an algae cultivation
plant showing additional details.
[0040] FIG. 3 illustrates a measurement and control device for
algae cultivation in an open growth facility.
[0041] FIG. 4 shows an algae cultivation plant suitable for use in
even terrain utilizing meshwork harvesting.
[0042] FIG. 5a illustrates the structure of a Spirogyra alga.
[0043] FIG. 5b shows a cross section through a Spirogyra alga.
[0044] FIG. 6a shows an algae mat.
[0045] FIG. 6b is a cross section through two algae mats.
[0046] FIG. 6c is a top view of the two algae mats of FIG. 6b.
[0047] FIG. 6d illustrates a processed algae mat.
[0048] FIG. 7a shows a schematic top view of a water net algae.
[0049] FIG. 7b is a cross section of a laminate algae mat.
[0050] FIG. 7c is a top view of the composite material of FIG.
7b.
[0051] FIG. 8a shows a cross section and a top view of the
isotropic algae mass.
[0052] FIG. 8b shows sections of algae mass.
[0053] FIG. 8c shows an insulation material.
[0054] FIG. 9a is a top view of a honeycombed structure for an
insulation mat.
[0055] FIG. 9b is a cross section of the mat of FIG. 9a.
[0056] FIG. 9c shows a magnified cross section through the mat of
FIG. 9a.
[0057] FIG. 10a is a top view showing a honeycombed structure for a
insulation mat.
[0058] FIG. 10b is a cross section through the mat of FIG. 10a.
[0059] FIG. 10c is a cross section trough an arrangement having two
insulation mats.
[0060] FIG. 11a shows an embodiment of an insulation material.
[0061] FIG. 11b shows an alternative embodiment of an insulation
material.
[0062] FIG. 12 shows an algae cultivation pond which is suitable
for use in flat terrain.
[0063] FIG. 13 illustrates harvesting of algae in an algae
cultivation pond.
[0064] FIG. 14a is a side view of a harvesting machine for algae in
an algae cultivation pond.
[0065] FIG. 14b is a front view of the harvesting machine of FIG.
14a.
[0066] FIG. 15 is a block diagram showing a method for producing
carbon fiber from algae mass.
DETAILED DESCRIPTION
[0067] An exemplary use of filamentous algae for construction is
explained with reference to Spirogyra algae, one of many
filamentous algae that are suitable for use in construction, as
illustrated in FIG. 5a. Spirogyra algae 500 are unbranched with
cylindrical cells connected end to end in long green filaments.
Cell wall 501 comprises an outer wall of cellulose and an inner
wall of pectin. A ribbon shaped, serrated or scalloped, and
spirally arranged chloroplast 502 is embedded within cell wall 501.
Cell wall 501 further comprises nitrogen, causing spirogyra algae
500 to be self-extinguishing.
[0068] As illustrated in cross sectional view FIG. 5b a cavity 503
is formed by cell wall 501 and chloroplast 502. The average
diameter 504 of Spirogyra algae 500 is approximately 30 micrometer.
When dried, cavity 503 is filled with air. The small diameter 504
of the dried Spirogyra algae 500 reduces the possible convective
flow of air within cavity 503, causing Spirogyra algae 500 to act
as a natural heat insulator.
[0069] Diameter 504 of a Spirogyra alga is approximately 5 times
larger than the diameter of artificially created carbon fibers,
which have a diameter of approximately 6 micrometers. However,
other than artificial fiber, the mass of the Spirogyra alga is
concentrated along its outer diameter at cell wall 501, a structure
that is almost impossible to artificially create. When dried,
Spirogyra algae 500 have a very low density of approximately 0.06
g/cm.sup.3. Dried spirogyra algae mass has a large ratio of surface
area to weight, which results in high robustness for products, e.g.
composite materials, made of spirogyra algae mass. The physical
structure of filamentous algae is similar to that of bamboo plants,
in that the plant's mass is concentrated along its outer diameter,
resulting in a lightweight, but mechanically robust structure. A
similar structure can be found e.g. in Spirogyra, Zygnema,
Mougeotia, or Cladophora algae.
[0070] As illustrated in FIG. 6a, algae from the order
Zygnematales, when dried, assume a form of a naturally fibrous
algae mat 601. In calm or evenly moving water Zygnematales
naturally grow in form of threads which are oriented parallel to
each other. This allows algae mat 601 to be used as fleece, felt or
insulation material simply by cutting or otherwise shaping it into
a desired shape. Other renewable fibers, e.g. those from wood, have
to be mechanically processed in energy consuming cutting processes,
to achieve the same structure. The algae within algae mat 601 have
a predominant orientation 602 of their cells due to anisotropic
growth.
[0071] A mechanically stronger structure can be created by applying
a binding agent 606 to a first algae mat 601 and a second algae mat
603 as shown in FIG. 6b. Binding agent 606 may for example be
potato starch or corn starch, or any other single- or
multi-component binding agent known in the art. Algae mats 601 and
603 may e.g. be soaked in a bath of binding agent. Referring to
FIG. 6c algae mat 601 and algae mat 603 are then placed onto each
other, such that the predominant orientation 602 of cells in algae
mat 601 is about perpendicular to the predominant orientation 604
of cells in algae mat 603. As shown in FIG. 6d a two-layer algae
mat 605 having a first layer of cells oriented perpendicular to a
second layer of cells results. The process can be repeated to
create algae mats having more than two layers.
[0072] Referring now to FIG. 7, composite material 704 utilizing
different species of algae is disclosed. An exemplary composite
material shown in FIG. 7b comprises three layers of algae. A center
layer 701 comprises Hydrodictyon reticulatum in the family
Hydrodictyaceae from the order Chlorococcales within the class of
Chlorophyceae. Hydrodictyon reticulatum form a large, usually
pentagonal or hexagonal, mesh which is illustrated in FIG. 7a.
Outer layers 702 and 703 are dried algae from the Zygnematales,
e.g. species from the genera of Spirogyra, Zygnema, Mougeotia, or
Cladophora which have a fibrous, string-like, structure.
[0073] The composite material 704 as shown in FIG. 7c combines
string-shaped algae cells in algae mats 702 and 703, and a central
mesh-structure of cells in an algae mat forming central layer 701.
Algae cells in mats forming outer layers 702 and 703 are oriented
about perpendicular to each other. The resulting composite material
704 provides good mechanical strength and resistance against
tearing. Composite material 704 comprising layers of algae mats in
center layer 701 and outer layers 702 and 703 may be manufactured
by adding a binding agent (not shown) to the algae mats in center
layer 701, and outer layers 702 and 703. The algae mats in each
layer are then placed onto each other, and pressure is applied.
[0074] Referring now to FIG. 8a, a mass 801 of isotropic dried
algae is shown in a top view and a cross sectional view. As
illustrated in FIG. 8b, algae mass 801 may be cut into several
pieces 802. As shown in FIG. 8c, a binding agent 803 is applied to
the algae pieces 802, forming a composite material 804. Composite
material 804 may be processed in several ways to be used as an
insulation material. Composite material 804 may e.g. be molded or
pressed.
[0075] Binding agent 803 may comprise gas bubbles, e.g. carbon
dioxide that has been added under pressure. During the molding or
shaping of composite material 804 the gas bubbles within binding
agent 803 may be allowed to expand, e.g. by reducing air pressure
around the composite material 804. Alternatively, a foaming agent
may be added, which generates bubbles within composite material
804. The additional bubbles in composite material 804 reduce the
density of composite material 804, and increase its heat insulation
performance.
[0076] Referring now to FIG. 9a, an insulation panel 911 having a
honeycomb structure is shown. The walls of insulation panel 911 may
be made of composite algae material or plastic. The honeycomb
structure of insulation panel 911 comprises a plurality of
honeycomb shaped chambers 912, which are sealed by foil 913.
Depending on the intended use of insulation panel 911, chambers 912
may be filled with different materials. Chambers 912 may e.g. be
filled with air or another gas for use as a heat insulation mat.
Even better heat insulation may be achieved by evacuating chambers
912, which requires the algae composite material forming insulation
panel 911 to be airtight.
[0077] Chambers 912 may also be filled with a filler material 914,
for example loose sand or plaster for use as noise attenuator. A
more detailed view of sand as filler material 914 of a chamber 912
is shown in FIG. 9b. Sand corns 915 are loosely situated within
chamber 912, allowing movement of the sand corns through hollow
areas 916. Noise energy is largely absorbed through mechanical
friction of sand corns rubbing against each other, thereby
providing good noise attenuation of the insulation panel 911.
Alternatively, chambers 912 may be filled with a liquid foam, or
gel containing gas bubbles, suitable to absorb energy when
compressed by sound waves.
[0078] Referring to FIG. 10, an alternative structure utilizing
several layers of honeycomb shaped algae mass are shown. An upper
layer of honeycomb shaped algae mat 1021 comprises upper chambers
1022 and a lower layer comprises lower chambers 1024. Upper layer
and lower layer only meet at small intersecting areas 1030, thereby
greatly limiting the possible heat transfer between the both
layers. The upper layer of algae mat 1021 is covered by top foil
1023. The lower layer of algae mat 1021 is covered by bottom foil
1025. Instead of using top foil 1023 and bottom foil 1025 algae mat
1021 may be covered by any other form of enclosing material, e.g.
plasterboard or boards made of wood. Depending on the intended use
upper chambers 1022 and lower chambers 1024 may be filled with the
same or different material. For example, upper chambers 1022 may be
filled with a noise attenuating material, while the lower chambers
1024 are filled with a heat insulating material. The noise
attenuating material may e.g. be sand, gel, or any other noise
attenuating material known in the art. The heat insulating material
may e.g. be air, expanded algae particles, or any other heat
insulating material known in the art.
[0079] An alternative structure is shown in FIG. 10c, wherein two
honeycomb algae mats 1026 and 1027 such as those disclosed with
reference to FIG. 9 are placed onto each other. Honeycomb algae
mats 1026 and 1027 are placed in opposite orientation, such that
their respective foil covers 1028 are facing outside. The honeycomb
chambers of mat 1026 and 1027 are preferably displaced relative to
each other by 1/2 of their size. Mats having different
characteristics, such as a noise attenuating mat 1026 may be
combined with a heat insulating mat 1027 to achieve a combined
functionality of a mat that is both heat insulating and noise
absorbing. While an example with two mats has been shown it should
be understood that advantageous combinations utilizing more than
two mats are possible.
[0080] While mats comprising dried algae mass have been found to be
surprisingly beneficial, further improvements are possibly by
pyrolizing algae mass to form carbon fibers. Dried spirogyra algae
have a carbon content of approximately 45%. Their cell wall 501
comprises cellulose, making the algae a suitable raw material for
the production of carbon fiber and carbon mats.
[0081] A method for producing carbon fiber from algae mass is
illustrated in FIG. 15. In a first step 1501 algae is harvested.
Next, the algae is dried in step 1502 to create dried algae mass.
In the next step 1503 the dried algae mass is placed into a sealed
container, wherein the algae mass is held by mounting fixtures at
both ends of the sealed container. The algae mass is held under
tension by the mounting fixtures. If the algae mass has a
predominant orientation of its cells, it is placed into the
container such that its cells are predominantly oriented parallel
to the tension that is created by the mounting fixture. The
predominant orientation of the tubular cells of the algae later
leads to a predominant orientation of carbon fibers of carbonized
algae. Next, in step 1504, the container is heated and evacuated to
minimize the amount of oxygen in the container, allowing the algae
mass to pyrolize. Heating of the container may occur in several
steps, e.g. 600.degree. C., 700.degree. C., 800.degree. C. and
900.degree. C. Optionally, as shown in step 1505, gas created by
the pyrolysis can be extracted and used as a heat source. Lastly,
in step 1506, the now carbonized algae material is removed from the
container.
[0082] Two carbonized algae mats can further be processed by adding
a binding agent, e.g. soaking the carbonized algae mat in a binding
agent, and placing them onto each other. The two mats are
preferably oriented such, that the predominant orientation of
carbon fibers of carbonized algae in each mat is perpendicular to
each other.
[0083] Yet another example of algae-based insulation material is
illustrated in FIG. 11a. As illustrated, two mats 1101 and 1104 are
placed onto each other. Mats 1101 and 1104 may be algae mats having
honeycomb structured chambers as disclosed with reference to FIG.
9. Mats 1101 and 1104 may also be any other suitable thermoformed
or pressed material. Chambers 1103 within mat 1101 are filled with
a filling material. The filling material comprises dried algae
mass. Preferably, the filling material comprises dried algae mass
which is mixed with silicic acid using a ratio of approximately 70%
dried algae mass and 30% silicic acid. Silicic acid nanoparticles
are commercially available, for example from Wacker Chemie, Munich,
Germany. The filling material is held in chambers 1103 by foil
1102, which is placed onto mat 1101 in an evacuated chamber, so
that air is evacuated from chambers 1103 before foil 1102 seals the
chambers. The low pressure surrounding the filling material in
chambers 1103 causes foil 1102 to bend concavely into chambers 1103
when mat 1101 is exposed to standard ambient air pressure.
[0084] Place onto mat 1101 is a slightly smaller mat 1104, having
one fewer chamber along its diameter than mat 1101. Mat 1104 is
placed onto mat 1101 with an offset, such that the center of a
chamber 1103 is about one half of a chamber width offset from the
center of a chamber 1106 of mat 1104. Chambers 1106 can be filled
with dried algae mass, which provides good heat insulation.
Chambers 1106 may also be filled with sand or gypsum, thereby
providing noise attenuation. Alternatively, chambers 1106 may be
filled with a mixture of dried algae mass and sand or gypsum.
Filling material is added to a level which is below the side walls
height, such that sealing foil 1105 can form a concave indentation
above each chamber 1106. The slightly concave shape of sealing foil
1105 above each chamber 1106 guarantees, that sealing foil 1105
touches upper mat 1101 only at the vertical walls around each
chamber 1106 of lower mat 1104. The limited contact of sealing foil
1105 with upper mat 1101 reduces thermal conductivity through the
insulation panel 1100.
[0085] Upper mat 1101 and lower mat 1104 are enclosed by an air
sealed container which forms the out wall of insulation panel 1100.
A lower container tub 1107 is sealed by a container lid 1108.
Insulation panel 1100 may be evacuated, removing air between the
walls of container 1107, 1108 and the upper mat 1101 and lower mat
1104. Container tub 1107 and lid 1108 can be made of metalized
synthetic foils. Two or more identical insulation panels 1100 may
be placed adjacent to each other, every other panel being placed
upside down, so that the wider upper mat 1101 of a first panel
extends over top of the smaller lower mat 1104 of an adjacent
panel, forming a half lap joint between both panels.
[0086] To form larger units, insulation panels 1100 can be mounted
onto a supporting board 1112, for example a drywall or
plasterboard.
[0087] In another example, as illustrated in FIG. 11b, an
insulation panel 1150 is provided. Insulation panel 1150 comprises
two panel members, an upper panel member 1121 and a lower panel
member 1122. Each panel member 1121 and 1122 is preferably made of
dried algae mass and a binder additive, e.g. gypsum. Panel members
1121 and 1122 comprise wedge shaped chambers 1151, 1152. The
surface area of wedge shaped chambers 1151, 1152 may optionally be
treated, e.g. by applying a metallization layer made of
aluminum.
[0088] Depending on the intended application of insulation panel
1150, chambers 1151 and 1152 are filled with different filling
materials. As shown, the chambers 1151 of upper panel 1121 are
filled with dried algae mass being filling material 1125. The
chambers 1152 of lower panel 1122 are filled with a mixture of
dried algae mass and an additive, for example sand, gypsum powder,
nanomaterial, silicic acid, or dried diatom algae, etc.
[0089] Chambers 1151 of upper panel member 1121 are sealed with
foil 1123. Preferably, air is evacuated from the upper chamber 1151
before foil 1123 is applied, so that the air pressure in chambers
1151 is about 30 mbar. Correspondingly chambers 1152 of lower panel
member 1122 are sealed by foil 1124. The low air pressure within
chambers 1151 and 1152 reduced convective heat transport through
panel 1150, thereby improving its heat insulation capability. When
exposed to ambient air pressure of typically 1013 mbar foils 1123
and 1124 are pushed into chambers 1151, 1152, forming a
characteristic concave shape above each chamber. Upper panel member
1121 and lower panel member 1122 are placed onto each other, so
that chambers 1151 and chambers 1152 face each other and are
displaced against each other with an offset of approximately 1/2
chamber width.
[0090] Upper panel member 1121 and lower panel member 1122 may be
assembled in a low atmospheric pressure environment of e.g. 100
mbar. In this example an external seal 1131 around the panel
between upper foil 1123 and lower foil 1124 is created. This causes
only a small relative pressure difference between air in the
chambers 1151, 1152 of about 30 mbar and air between upper panel
member 1121 and lower panel member 1122 of about 100 mbar.
Consequently, the concave indentation of upper foil 1123 and lower
foil 1124 is less pronounced, as is illustrated in broken line 1127
and 1128. This gives the filling material 1125 and 1126 within
chambers 1151 and 1152 some room to move within the chambers. The
ability of filling material 1126 to move within chamber 1152 is
desirable to provide noise attenuation. Noise energy can be
absorbed by small relative movement of the dried algae mixture with
sand or gypsum being filling material 1126. The material can be
tuned to optimize noise absorption in a particular audio frequency
by variation of pressure within chambers 1152 and the pressure
between upper panel member 1121 and lower panel member 1122. Upper
panel member 1121 and lower panel member 1122 only contact each
other at surround seal 1131 of upper foil 1123 and lower foil 1124.
The reduced contact surface between upper panel member 1121 and
lower panel member 1122 provides good thermal and noise
insulation.
[0091] Luckily, green algae that are suitable for use in insulation
material are relatively easy to grow. Several alternative algae
cultivation plants, as well as harvesting methods and machines are
disclosed, which can produce green algae for use in insulation
material as described above. As part of the carbon cycle green
algae absorb carbon dioxide and water under sunlight to produce
carbohydrate energy, leaving oxygen as a byproduct. Hence it is
desirable to combine algae cultivation plants with fossil fuel
burning facilities, for example power plants or other industrial
facilities that generate carbon dioxide. The algae cultivation
plant in such a combination absorbs some of all of the carbon
dioxide that is generated by the power plant or industrial
facility, thereby reducing the carbon dioxide emissions. The
ability to reduce carbon dioxide emissions is of particular
interest in jurisdictions that regulate carbon dioxide emissions,
possibly taxing such emissions, for example by requiring an emitter
to purchase carbon dioxide emission rights.
[0092] Referring to FIG. 1, a diagram of an exemplary algae
cultivation plant in combination with a carbon dioxide generating
facility is illustrated generally. The exemplary plant includes a
cascading set of algae cultivation ponds 107 having sloped floors
115. The ponds are filled with water that is rich in phosphates,
nitrates, and other nutrients. More specifically, the ponds may be
filled with pre-treated waste water 104 from a sewer plant or
another source. Water in algae cultivation ponds 107 circulates
trough circulation pump 113. The water in ponds 107 is rich in
nutrients for cultivating algae and contains algae spores.
[0093] Carbon dioxide from a fuel burning power plant is extracted
from the power plant's flue gas. The fuel burning power plant may
for example be a fossil fuel burning power plant such as a gar or
coal power plant. The fuel burning power plant may also be a biogas
burning power plant. A carbon dioxide extractor and distributor 103
extracts carbon dioxide from the power plant's flue 102 and pumps
carbon dioxide into carbon dioxide storage tank 101, gas inlet
pipes 110, or both. Carbon dioxide storage tank 101 is used to
store carbon dioxide for use during downtimes when the power plant
is not operating. Carbon dioxide from either the flue 102 or carbon
dioxide storage tank 101 is pumped through extractor and
distributor 103 and injected into algae cultivation ponds 107
through gas inlet pipes 110. Alternatively, the step of extracting
carbon dioxide from the flue gas may be omitted, and flue gas that
is rich in carbon dioxide may directly be pumped from flue 102 into
carbon dioxide storage tank 101 or gas inlet pipes 110 for
injection into algae cultivation ponds 107. A gas is considered
rich in carbon dioxide, if the concentration of carbon dioxide
therein is at least 0.1% by volume. This equals about three times
the concentration of carbon dioxide that is naturally occurring in
the atmosphere, which is approximately 0.0387% by volume.
[0094] The amount of carbon dioxide or flue gas that is injected
into algae cultivation ponds 107 is controlled by a control system
based on several inputs. Among the inputs of the control system are
one or more of the water level in ponds 107, temperature of the
water in ponds 107, acidity of the water in ponds 107, intensity of
sunlight 116, and sunlight intensity in pond 107 below algae slick
109, to create optimal growth conditions for algae in ponds
107.
[0095] The control system may further comprise sensors for sensing
air pressure and water pressure in the algae cultivation ponds 107
and control the pressure of carbon dioxide or flue gas in gas inlet
pipes 110 to be below the sum of air and water pressure, thereby
avoiding excess carbon dioxide or flue gas to escape through algae
cultivation ponds 107.
[0096] The control system comprises tables stored in electronic
memory, correlating sensors inputs for sunlight intensity, water
oxygen saturation and water acidity in ponds 107 with an optimal
carbon dioxide or flue gas injection rate. For example, the amount
of carbon dioxide injected into pond 107 increases with increasing
sunlight intensity and decreases with decreasing sunlight
intensity. The data in the tables may be empirically derived trough
tests and be specific for different kinds of algae. The control
system controls the amount of carbon dioxide or flue gas injected
into the algae cultivation ponds 107, and the amount of waste water
104 inserted through waste water valve 105 and waste water inlet
106. The control system further controls the amount of water 117
that is recycled through from collector basin 118 through
circulation inlet 114 into algae cultivation pond 107.
[0097] Continuous growth of algae in algae cultivation ponds 107
leads to formation of an algae slick 109, which floats on top of
the water in algae cultivation pond 107 and prevents sunlight from
penetrating the water, thereby reducing further growth of algae in
algae cultivation pond 107. Sensors (not illustrated) determine the
thickness of algae slick 109 and generate a signal, once a
predetermined thickness has been reached. Responsive to the signal,
the injection of carbon dioxide or flue gas into algae cultivation
pond 107 is stopped, and gravitational harvest of the algae is
initiated. Thickness of the algae slick 109 may be determined by
comparing sunlight intensity measured by a first sensor outside the
algae cultivation pond 107 with sunlight intensity measured by a
second sensor within the algae cultivation pond 107. The second
sensor is located within the algae cultivation pond 107 below the
algae slick 109. A large difference in sunlight intensity between
the first and the second sensor indicates a thick, light absorbing
algae slick 109. Instead of utilizing sunlight, an artificial light
source (not shown) may be used to determine the thickness of algae
slick 109.
[0098] A carbon dioxide sensor may be located above the water level
of algae cultivation pond 107 to reduce or stop the injection of
carbon dioxide or flue gas into algae cultivation pond 107, if
increased levels of carbon dioxide are measured to be escaping
algae cultivation pond 107.
[0099] Algae cultivation ponds 107 comprise a sloped floor 115 and
a pivotable dam wall 108. Algae are harvested by opening pivotable
dam walls 108, which pivot in a downhill direction, allowing water
and algae slick 109 to flow downhill from algae cultivation ponds
107 into a collector basin 118. Grill 112 is used to separate algae
mass 111 from the water. As water and algae slick 109 from ponds
107 slides downhill the sloped floor 115 of ponds 107 into
collector basin 118 algae mass 111 is caught on grill 112, while
water 117 flows through grill 112 into collector basin 118. Algae
mass 111 may be left on grill 112 to dry, and be removed from grill
112 for further processing.
[0100] Water 117 may be recycled by pumping water 117 from
collector basin 118 through circulation pump 113 and circulation
inlet 114 back into pond 107.
[0101] If flue gas from flue 102 is directly injected into ponds
107, it beneficially heats the water in ponds 107, thereby causing
optimal conditions for algae growth.
[0102] An aerator device 119 may be operatively connected to the
outlet of carbon dioxide carrying gas inlet pipe 110 into ponds
107. Aerator device 119, which may be a membrane comprising small
holes, causes carbon dioxide or flue gas from gas inlet pipe 110 to
form small bubbles when injected into pond 107. These bubbles
support a uniform saturation of pond 107 with carbon dioxide. They
further spread sunlight entering pond 107, causing an increases
photosynthesis activity of the algae growing in pond 107.
[0103] Opening and closing pivotable dam walls 108 causes
alternating growth and harvesting cycles, wherein the pivotable dam
walls 108 are closed and ponds 107 are filled with water during a
growth cycle and pivotable dam walls 108 are opened during a
harvesting cycle.
[0104] Algae mass 111 that has been removed from grill 112 may be
dried and processes into construction material as described above.
Algae mass 111 may also be utilized as a resource for
pharmaceutical, medical or cosmetic use. Algae mass 111 may further
be used as a resource for animal food, renewable fuel, fertilizer,
or natural fiber construction material.
[0105] An alternative algae cultivation plant using an indirect
injection of carbon dioxide is disclosed with reference to FIG. 2.
Several algae cultivation ponds 207 are provided, arranged in a
cascade along the slope of a hill or mountain, each having a wall
208 that can be lowered. Below the last cultivation pond 207 is an
overflow and mixing reservoir, which is adapted to inject carbon
dioxide and nutrients for algae cultivation thereto. Water
circulates from circulation inlet 214 into the uppermost
cultivation pond 207, through the cascading set of cultivation
ponds 207, and the overflow and mixing reservoir 224. The
circulation is facilitated by circulation pump 213, which pumps
water from the overflow and mixing reservoir 224 uphill to
circulation inlet 214 and the uppermost cultivation pond 207.
[0106] To grow, algae need water, nutrients, carbon dioxide, and
sunlight. The open structure of algae cultivation ponds 207 exposes
algae to sunlight 216. Alternatively algae cultivation pond 207 may
be underneath a transparent cover through which sunlight can enter
the algae cultivation pond 207. The sunlight exposure may be
amplified by placing reflective material onto the floor of algae
cultivation ponds 207, thereby exposing algae not only to the
direct sunlight 216, but also to light that is reflected of the
floor of algae cultivation ponds 207. Alternatively, algae
cultivation ponds 207 may be made of a reflective material, e.g.
stainless steel or alloy to achieve the same effect.
[0107] Nutrients are added to the water in cultivation ponds 207
through overflow and mixing reservoir 224. Nutrients may
specifically include phosphates and nitrates, which can be a side
product of sewer plants. Water that is rich in nutrients is pumped
through pipe 204 and pump 205 and inlet 206 into a heating
reservoir 221. Pump 218 has an inlet pipe 219 which reaches into
heating reservoir 221. Pump 218 pumps warm, nutrient rich water
from heating reservoir 221 through outlet pipe 217 into overflow
and mixing reservoir 224, where it enters the water circulation
through cultivation ponds 207.
[0108] The necessary carbon dioxide to stimulate growth of algae in
algae cultivation ponds 207 stems from a powerplant or other
facility producing gas that is rich in carbon dioxide. Carbon
dioxide rich gas is diverted from flue 202 to compressor 203, where
the gas is compressed to about 6.5 bar. Through gas pipe 222 the
warm, carbon dioxide rich gas is pumped through a heat exchanger in
heating reservoir 221, thereby cooling the gas in gas pipe 222 and
heating the nutrient rich water in heating reservoir 221. Through a
control valve 225, which also acts as a check valve, the carbon
dioxide rich gas is injected into an underground water reservoir
201. Underground water reservoir 201 is a sealed pressure
container. Overflow and mixing reservoir 224 and underground water
reservoir 201 are connected by pipe 210. Underground water
reservoir 201 is located lower than the open overflow and mixing
reservoir 224, for example 60 meters below the overflow and mixing
reservoir 224. Consequently, the pressure in underground water
reservoir 201 is approximately .DELTA.P=6 bar above the pressure at
the bottom of overflow and mixing reservoir 224.
[0109] Water within the underground water reservoir 201 having a
temperature of 10.degree. C. and a pressure of 6 bar can absorb 6
gram of carbon dioxide per liter. Underground water reservoir 201
can therefore store carbon dioxide, for example carbon dioxide that
is generated at night, when due to lack of sunlight the algae in
cultivation ponds 207 can't grow, and hence don't need any carbon
dioxide. An underground reservoir holding a volume of 1000 m.sup.3
of water at 10.degree. C. and 6 bar can store 6000 kg of CO2. Rest
gas having low CO2 content can escape the underground water
reservoir 201 through pressure relieve valve 223 in pipe 220.
Flowing in opposite direction, pipe 220 may also be used to add
water into underground water reservoir 201.
[0110] Assuming a temperature of 22.degree. C. and standard
atmospheric pressure of 1 bar, water in overflow and mixing
reservoir 224 can store only 1.5 gram of carbon dioxide per liter.
Therefore, carbon dioxide rich water from underground water
reservoir 201 is added to overflow and mixing reservoir 224 through
control valve 227 at a maximum ration of 1 liter of water from
underground water reservoir 201 per every 3 liter of water in
overflow and mixing reservoir 224. Carbon dioxide mixed into the
water of overflow and mixing reservoir 224 enters the circulation
through the cultivation ponds 207, where the carbon dioxide is
absorbed by the growing algae.
[0111] Algae from the order Zygnematales, especially species from
the genera of the Spirogyra, the Zygnema, and the Mougeotia, and
Hydrodictyon algae from the order Chlorococcales grow close to the
surface of cultivation ponds 207, forming algae slick 209. Sunlight
216 is used for the photosynthesis of algae slick 209, absorbing
primarily blue and red, including near infrared, light. Zygnema and
Spirogyra algae grow in a preferred orientation of their cells.
[0112] To harvest algae from cultivation ponds 207, the lower walls
208 of algae cultivation ponds 207 be lowered, so that water and
algae contained in the cultivation ponds flows downhill towards
overflow and mixing reservoir 224. A grill 212 is provided above
overflow and mixing reservoir 224 to capture algae mass 211 and
separate it from water of the cultivation ponds 207. Algae mass 211
may be left on grill 212 to air dry, or removed when still wet for
further processing.
[0113] The right time to harvest algae can be determined by a
control system as illustrated in FIG. 3. Algae 309 grow in an algae
cultivation pond 307, which is filled with water that is rich in
nutrients and carbon dioxide. Algae 309 hereby forms an algae slick
which floats on the water of algae cultivation pond 307. A side
wall 338 having a pivotable wall segment 337 is provided. An
overflow gate 339 extends above pivotable wall segment 337,
allowing excess water to flow through it, while holding algae 309
back inside algae cultivation pond 307.
[0114] Through valve 305 and first inlet 306 an aqueous nutrient
solution can be added to algae cultivation pond 307. The aqueous
nutrient solution may for example we water that is rich in
phosphates and nitrates, a typical byproduct of sewer plants.
[0115] Through valve 313 and second inlet 314 fresh water and algae
spores can be added to algae cultivation pond 307. Second inlet 314
may also be connected to a circulation pump to circulate water in
algae cultivation pond 307.
[0116] An aerator 336 is provided, through which a gas, e.g. carbon
dioxide, flue gas, air, or a mixture thereof, can be injected into
algae cultivation pond 307. The amount of gas is controlled through
gas inlet valve 303. The volume or mass flow of gas through gas
inlet pipe 310 into aerator 336 is measured by a volume flow or
mass flow sensor 330.
[0117] Algae 309 grow in the presence of sunlight 316. The
intensity of sunlight 316 is measured by exterior sunlight sensor
317, which is mounted outside of algae cultivation pond 307. A
second, submersed light sensor 318 is disposed inside algae
cultivation pond 307, located under algae 309 that are floating in
algae cultivation pond 307. Both exterior sunlight sensor 317 and
submersed light sensor 318 are operatively connected to a central
control unit 319. Central control unit 319 is adapted to read data
from exterior sunlight sensor 317 and submersed light sensor 318.
By comparing data from exterior sunlight sensor 317 and submersed
light sensor 318 underneath algae 309, the thickness of algae 309
can be determined. A thicker layer of algae 309 absorbs more light,
thereby leading to a larger difference in light sensed between
exterior sunlight sensor 317 and submersed light sensor 318. The
difference in sensor measurements between exterior sunlight sensor
317 and submersed light sensor 318 is used as an input to an
algorithm in central control unit 319 which determined the right
time to harvest algae 309. A more accurate measurement may be
achieved by using an artificial light source (not shown) to
illuminate submersed light sensor 318 trough algae 309 with a
predetermined light intensity.
[0118] While exterior sunlight sensor 317 and submersed light
sensor 318 are used to determine sufficient thickness of algae 309
for harvest, information from one or both of these sensors is also
used to determine the correct amount of carbon dioxide to inject
through aerator 336 into algae cultivation pond 307. The amount of
carbon dioxide that can be processed by photosynthesis in algae 309
depends on the amount of sunlight 316, and changes over the course
of a day. At night, exterior sunlight sensor 317 detects the
absence of sunlight 316. Central control unit 319, responsive to a
signal from exterior sunlight sensor 317 indicating darkness,
closes gas inlet valve 303 through its output 327.
[0119] Central control unit 319 is an industrial control system,
such as a programmable logic controller. Central control unit 319
comprises a microcontroller, power supply, electronic memory, and
input and output circuitry such as for example A/D converters, D/A
converters, and PWM signal generators. Central control unit 319 is
powered through power input 324.
[0120] Central control unit 319 also determines and control optimal
growth conditions for algae 309. Operatively connected to central
control unit 319 is further a temperature sensor 320, configured to
measure the temperature of water inside algae cultivation pond 307.
A pH probe 321 is also operatively connected to central control
unit 319 and adapted to measure the acidity of water in algae
cultivation pond 307.
[0121] An external CO.sub.2 sensor 322 is provided outside algae
cultivation pond 307, positioned such that it can sense carbon
dioxide concentration around algae cultivation pond 307, the
CO.sub.2 sensor 322 being operatively connected to central control
unit 319. If elevated carbon dioxide levels are sensed by CO.sub.2
sensor 322, central control unit 319 reduces the inflow of carbon
dioxide into algae cultivation pond 307 through aerator 336 by
closing gas inlet valve 303. Potentially dangerous levels of
CO.sub.2 sensed by CO.sub.2 sensor 322 can trigger an visual or
audible alarm, alerting personnel of a potential health risk around
algae cultivation pond 307.
[0122] Outputs 325 through 329 of central control unit 319 are
connected to the various actuators of the system. More
specifically, output 325 is operatively connected to valve 305,
providing central control unit 319 control over the inflow of
nutrients into algae cultivation pond 307. Output 326 is
operatively connected to valve 313, providing central control unit
319 control over the inflow of fresh water, or water circulation
into algae cultivation pond 307. Output 327 is operatively
connected to gas inlet valve 303, providing central control unit
319 control over the flow of carbon dioxide into algae cultivation
pond 307. Output 328 is operatively connected to pivotable wall
segment 337, allowing central control unit 319 to open algae
cultivation pond 307 so that algae and water flow out. Lastly,
output 329 provides a diagnostic interface for use with a
diagnostic control device (not shown).
[0123] An external input 323 is used to program central control
unit 319. The external input may e.g. be a connection to a computer
system for downloading tables of empirically gathered data that
correlate sensor data from one or more of sensors which are
operatively connected to central control unit 319 with a suitable
carbon dioxide volume flow. Central control unit 319 in this
example controls gas inlet valve 303, using feedback from mass flow
sensor 330, to achieve a predetermined flow of carbon dioxide
through aerator 336 into algae cultivation pond 307. The target
value of carbon dioxide flow is determined through one or more
lookup tables, which correlate sensor inputs with a target volume
flow of carbon dioxide.
[0124] Alternatively, external input 323 may provide a pH setpoint.
In this example central control unit 319 controls the acidity water
inside algae cultivation pond 307. For some green algae, the water
acidity, measured by pH probe 321, is kept preferably between pH
6.0 and 9.2. A max acidity of pH 10.0 should not be exceeded to
prevent damage to the algae in algae cultivation pond 307. The
acidity of water in algae cultivation pond 307 is controlled by
increasing or decreasing the amount of carbon dioxide that enters
algae cultivation pond 307 through gas inlet valve 303. If the
water in algae cultivation pond becomes too acidic, central control
unit 319 adds fresh water by controlling valve 313.
[0125] Central control unit 319 may be connected to additional
sensors, e.g. an atmospheric pressure sensor, or a water pressure
sensor (not shown). Central control unit 319 may comprise
programmable operating parameters, e.g. water hardness of water in
algae cultivation pond 307, which can be determined through manual
tests and entered manually into central control unit 319.
[0126] Central control unit 319 is configured to create optimal
growth conditions for a particular species of algae to be grown in
algae cultivation pond 307. Algae species from the genera of the
Spirogyra, for example, thrive in water having a temperature of
25.degree. Celsius, and a pH-value of between 6.2 and 8.2,
preferably 7.2. The ideal acidity of water to foster growth of
Spirogyra algae depends on its hardness, as illustrated in the
table below:
TABLE-US-00001 Carbonate hardness pH value 7 6.8 11 7.0 14 7.1
Central control unit 319 is configured to regulate acidity of the
water to a predetermined target level, which is configured for each
installation of an algae cultivation pond based on the hardness of
water to be used in the algae cultivation pond.
[0127] Referring now to FIG. 4, an alternative design for
cultivating and processing algae using net harvest is illustrated.
The algae cultivation ponds shown in FIG. 1, FIG. 2 and FIG. 3
utilize gravitational harvest, in which algae is harvested by
opening an algae cultivation pond, allowing its content to flow
down a slope through a harvesting grill. In contrast, the design
illustrated in FIG. 4 does not need a sloped arrangement of algae
cultivation ponds, and leans itself for use in flat terrain.
[0128] An algae cultivation pond 401 is provided, which is located
adjacent to a collector reservoir 402 of similar size. A net 403 is
provided, the width of which extends across algae cultivation pond
401. Net 403 is rolled into a roll 409, which is located at one end
of algae cultivation pond 401. Net 403 extends along algae
cultivation pond 401 and collector reservoir 402. Net 403 is
connected to a pulling device 407 located at the opposite end of
collector reservoir 402. Net positioning sliders 404 are provided,
through which net 403 can be pushed to the bottom of algae
cultivation pond 401 or collector reservoir 402. FIG. 4 shows net
403 being positioned at the bottom of algae cultivation pond 401 by
net positioning sliders 404, which are in their lowered
position.
[0129] Algae cultivation pond 401 uses the water circulation,
carbon dioxide injection, and control concepts described with
reference to FIG. 1, FIG. 2 and FIG. 3 above. For simplicity, those
are not shown in FIG. 4.
[0130] To cultivate algae, net 403 is lowered towards the bottom of
algae cultivation pond 401 by lowering net positioning sliders 404.
This is done before any algae are allowed to grow in algae
cultivation pond 401. Algae are then allowed to grow in algae
cultivation pond 401 by injecting algae spores, carbon dioxide, and
nutrients are described. Once algae 405 have grown sufficiently
thick, they are harvested.
[0131] To harvest algae 405, net positioning sliders 404 are lifted
into their upper position, which is above the water level of water
in algae cultivation pond 401. Pulling device 407 is activated,
thereby lifting net 403 out of algae cultivation pond 401,
conveying algae 405 into position of algae mass 406. Algae mass 406
is left in position above collector reservoir 402 to dry.
[0132] Depending on the application, dried algae mass 406 is
removed from net 403 for further processing. Alternatively, algae
mass 406 may be processed jointly with net 403, which becomes part
of a raw material. The process of growing and harvesting algae can
continue, until net 403 on roll 409 is exhausted. Alternatively,
net 403 may be replenished, connecting a net 403 from a new roll
409 with the end of a net 403 from an empty roll, thereby allowing
continuous operating of the algae cultivation plant as shown.
[0133] An alternative harvesting technique is disclosed with
reference to FIG. 12. An algae cultivation pond 1200 is provided,
having a recirculation inlet 1205 and a freshwater inlet 1206 on
one end of algae cultivation pond 1200. On the opposite end of
algae cultivation pond 1200 is an overflow rim 1202. The top edge
of overflow rim 1202 is at the lowest point of the wall surrounding
the algae cultivation pond and thereby establishes the maximum
water level of water in algae cultivation pond 1200. Overflow rim
1202 is fin-shaped, to allow algae slick 1201 to easily flow across
it. Any excess water entering algae cultivation pond 1200 through
recirculation inlet 1205 or freshwater inlet 1206 flows over
overflow rim 1202 into collector reservoir 1204. Disposed within
collector reservoir 1204 is conveyor belt 1203.
[0134] In a continuous operating mode of an algae cultivation
plants as illustrated in FIG. 12 water constantly circulates within
algae cultivation pond 1200 by pumping water through pump 1207 from
collector reservoir 1204 through pipes and recirculation inlet 1205
into algae cultivation pond 1200. Any water loss is replenished by
adding water through freshwater inlet 1206. Water added through
freshwater inlet 1206 may be rich in nutrients that are required to
foster growth of algae slick 1201. Circulation of water through
algae cultivation pond 1200 causes algae slick 1201 to move with
the circulating water over overflow rim 1202 and onto conveyor belt
1203. Conveyor belt 1203 separates algae mass from water, and
transports the algae for further processing.
[0135] In a burst operating mode, the water level in algae
cultivation pond 1200 is kept below overflow rim 1202 during a
growth phase of algae slick 1201. When algae slick 1201 is ready
for harvest, water is added into algae cultivation pond 1200
through freshwater inlet 1206. Additionally, water may be caused to
circulate by pumping water through pump 1207 from collector
reservoir 1204 to recirculation inlet 1205. The flow of water from
through algae cultivation pond 1200 from inlets 1205 and 1206 to
overflow rim 1202 causes algae slick 1201 to flow over overflow rim
1202 onto conveyor belt 1203. Conveyor belt 1203 transports the
algae for further processing. To provide optimal growth conditions
of algae slick 1201 water that is saturated with carbon dioxide can
be injected into the water circulation of algae cultivation pond
1200 from an underground water reservoir 1209 through pump 1208.
Flue gas which is rich in carbon dioxide is inserted into
underground water reservoir 1209 through compressor 1210. Excess
carbon dioxide which does not dissolve into the water in
underground water reservoir 1209 returns through return pipe 1212
back to the flue. To protect the algae in algae cultivation pond
1200 a transparent cover 1213 is provided, which prevents
contaminants such as leafs, dust, or rain from entering algae
cultivation pond 1200. Transparent cover 1213 is mounted such, that
rain water is directed into a trench 1214, which directs the rain
water away from algae cultivation pond 1200, thereby maintaining
close control over the environment in algae cultivation pond
1200.
[0136] An alternative algae cultivation plant is illustrated in
FIG. 13. Algae cultivation pond 1300 is provided. Through water
inlet 1305 water can be pumped into algae cultivation pond 1300,
e.g. water that is rich in nutrients that are required for algae
slick 1301 to grow in algae cultivation pond 1300. Located at one
end of algae cultivation pond 1300 is an overflow rim 1303. Located
behind overflow rim 1303 is a conveyor belt 1304. Algae slick 1301
can be harvested manually by pulling a floating rake 1302 across
algae cultivation pond 1300 towards overflow rim 1303. Floating
rake 1302 pulls algae slick 1301 across overflow rim 1303 onto
conveyor 1304. From there, algae slick 1301 is transported by
conveyor 1304 for further processing. Located around conveyor 1304
are water drains or recirculation pipes (not illustrated) to drain
water that is pulled with algae slick 1301 onto conveyor 1304.
[0137] An alternative approach of harvesting algae in an algae
cultivation pond is the use of an algae harvesting machine 1400 as
shown in FIG. 14. Algae harvesting machine 1400 is preferably used
in algae cultivation ponds 1420 having a width that is only
slightly wider than the width of algae harvesting machine 1400.
Algae harvesting machine 1400 comprises a frame 1402, which rests
on wheels 1403. Wheels 1403 allow algae harvesting machine 1400 to
move forward and backward in algae cultivation pond 1420.
[0138] An algae slick 1401 floating in algae cultivation pond 1420
can be automatically harvested with algae harvesting machine 1400.
Algae slick 1401 is picked up by a rotating harvesting barrel 1404.
Harvesting barrel 1404 comprises circumferentially and axially
spaced spikes 1421 which lift algae mass 1401 out of the water in
algae cultivation pond 1420 as algae harvesting machine 1400 moves
along cultivation pond 1420. From harvesting barrel 1404 algae
slick 1401 is transferred to conveyor barrel 1405, which conveys
algae mass 1401 from harvesting barrel 1404 to slide 1409. Slide
1409 utilizes a comb-shaped end, through which spikes 1406 of
conveyor barrel 1405 can pass. Algae slick 1401 is separated from
conveyor barrel 1405 and slides along slide 1409 onto conveyor belt
1410. Conveyor belt 1410 transports algae slick for further
processing outside algae cultivation pond 1420.
[0139] Algae harvesting machine 1400 is powered electrically
through photovoltaic cells 1411 located on top of frame 1402. Since
algae slick 1401 needs sun to grow, and algae harvesting machine
1400 needs sunlight to charge batteries (not shown) through
photovoltaic cells 1411, photovoltaic cells 1411 can be dimensioned
such, that they supply just enough energy to facilitate harvesting
algae slick 1401 that has grown when exposed to the same sunlight
as photovoltaic cells 1411.
[0140] Algae harvesting machine 1400 further comprises an exterior
light sensor 1407 above algae slick 1401 and a submersed light
sensor 1408 below algae slick 1401. The difference in sunlight
sensed by exterior light sensor 1407 and submersed light sensor
1408 indicated the thickness of algae slick 1401, and can be used
to determined the best speed of algae harvesting machine 1400.
[0141] While the present invention has been described with
reference to exemplary embodiments, it will be readily apparent to
those skilled in the art that the invention is not limited to the
disclosed or illustrated embodiments but, on the contrary, is
intended to cover numerous other modifications, substitutions,
variations and broad equivalent arrangements that are included
within the spirit and scope of the following claims.
* * * * *