GB2460114A - Apparatus for the containment of open water algae plantations - Google Patents

Abstract

Apparatus for the containment of algal plantations in open water, seas or oceans comprises a plurality of linked booms to form an enclosure. Each boom has floating part2and a skirt4which hangs generally vertically from the floating part by means of a weighted hem3. The apparatus may have a plurality of anchors which provide a level of control of the shape of the linked booms and prevent the prevailing winds from closing up the sides of the enclosure. There may be unmanned agitation vessels that transverse the enclosure to circulate the developing crop and ensure even expose to sunlight. There may also be a fertilization mechanism which brings up nutrient rich cold deep water. This invention includes a novel mechanism that combines the provision of nutrient from depth with the sequestration of liberated gases from that deeper water and with the provision of renewable energy that drives the whole process and delivers a surplus of energy for additional supplementary processing.

Description

Containment, Agitation and Fertilisation of Large Open Water Algae Plantations This invention relates to large scale algae plantations in open water where physical containment and crop agitation is required for practical cultivation purposes or for limiting the spread of applied nutrients whether these are applied artificially or by bringing up nutrient-rich water from lower depths.

Background to the Invention

Biomass derived from algae is increasingly seen to have higher energy content than conventional sources of biomass and its value as a feedstock for new types of bio fuel is now widely recognised.

Two forms of production are in common use -Open Pond cultivation and Photo-bioreactor cultivation. Both systems of production lack the capacity to provide the enormous volumes of biomass necessary to replace fossil fuel feedstocks and neither system can come close to meeting the economic levels of production that underpin conventional petroleum fuels.

Bio fuel production from agricultural sources is also hampered by the Food versus Fuel' debate where land and water resources are under increasing pressure to supply more high value crops for food leaving little scope for low value crops for energy.

In the short term, massive subsidies are being employed to promote agricultural bio crops but this will still not supply sufficient biomass and merely results in sharp increases in the price of basic foodstuffs and animal feeds.

Marine microalgae are much more efficient converters of solar energy than terrestrial plants, they are already in aqueous suspension and they do not compete for scarce resources with the production of food crops.

Marine microalgae in this context refer to photosynthetic organisms (phytoplankton) that range in size from 10 microns to up to 2millimetres in individual cell length and which link together to form multi-cellular chains or colonies several millimetres in length.

Plantations in this context refer to large areas of open ocean ranging in size from 5Oha to 50, 000ha or larger.

Vast tracts of seas and oceans have ample exposure to energy from the sun to maintain ideal conditions for substantial algal growth but lack the nutrients necessary to stimulate and sustain such growth. These low fertility regions can be used for the artificial cultivation of large plantations of marine algae.

This invention provides a viable means of containing such plantations in the open ocean and restricting the spread of applied nutrient to the area of the plantation. It provides an organic source of nutrient by using renewable energy to pump nutrient rich cold water from below the warm surface water. It further introduces a mechanism for the agitation of the growing algae within the containment area so as to optimise the crop by ensuring equal access to solar radiation and nutrient supply.

Statement of Invention

Containment of the plantation both above and below the surface of the water is achieved by continuous linked lengths of floating booms that are deployed from a seivice vessel. The upper part of the boom comprises floatation chambers that support the whole structure and rise above the water level. The lower skirt' of the boom drops down below the water level and is kept at that level by a weighted hem on the bottom edge.

The floating boom encircles the whole of the plantation and enables a cultivation environment to be created within a contained area and to a defined depth of water.

Optional Features 1) To promote even cultivation of the crop, a powered floating device circulates the water column vertically by taking in water from below and pumping it out at the surface. This has the effect of stirring up the crop to ensure that lower growing algae are equally exposed to light and that nutrients are evenly distributed vertically and horizontally within the containment area. This device can be naturally powered (e.g. Solar) or artificially powered.

2) To organically enhance the growing environment, a floating fertilisation device takes cool, nutrient rich water from a pre-set depth and brings it to the surface region for the benefit of the crop. This device can be naturally powered (e.g. Solar, OTEC*, etc) artificially powered, stimulated by the natural action of the waves or a combination of these.

*Ocean Thermal Energy Conversion

Introduction to the Drawings

Figure laP! shows a section of containment boom floating on the surface of the water (I) with the flotation collar (2) projecting above the surface and the weighted hem (3) keeping the lower end of the device at depth and the skirt (4) set vertically in the water. The depth (d) is variable and set by the length of skirt ranging up to 3 metres.

Figure IbIf shows an area of open water (1) encircled by a series of linked containment booms (2) floating on the surface with the whole structure being free to move with the ocean currents while a number of sea anchors (3) are deployed to provide some resistance on one side of the structure to resist the tendency for the prevailing winds (4) to bring the windward sections into contact with the downwind sections of the enclosure.

Figure 2a/7 represents the Agitation Mechanism (pump variation) mounted on a pair of catamaran hulls (I) connecting the main deck (2) in which is located the pump, battery pack and control/mixing valves. The vessel is steered and powered by a pair of electric propulsion motors (3) which can optionally be propeller or waterjet propulsion units. Main and auxiliary power is from an array of solar cells (4) which also charge up the battery bank that supply main power during periods of darkness.

The positional control unit (5) and navigation unit (6) are located on the superstructure and communicate wirelessly with the Base Station (not shown) and with GPS satellites. On the pump variant, a water intake (7) is positioned at the end of an inlet pipe (8) set to depth (d) to take in the water/algae mix at the lower levels of the water column to redistribute the mixture through the outlet (9) at the top of the water column.

Figure 2b17 represents the paddle variation of the Agitation Mechanism which is very similar to the pump variation except that the paddle (10) rotates slowly so as to gently chum the water column in order that algae within the water column are more likely to receive equal exposure to the different levels of sunlight and shade.

Width of processing is a key processing efficiency factor and both mechanisms can be configured to cover the entire width of the vessel carrying the agitation mechanism.

Figure 3a/7 represents the Fertilisation Mechanism mounted on a pair of catamaran hulls (1) connecting the main deck (2) in which is located the pumps, battery pack, de-aeration equipment and control valves etc. The vessel is steered and powered by a pair of electric propulsion motors (3) which can optionally be propeller or waterfet propulsion units. Main and auxiliary power is from an array of solar cells (4)* which also charge up the battery bank that supply main power during periods of darkness.

The positional control unit (5) and navigation unit (6) are located on the vessel superstructure and communicate wirelessly with the Base Station (not shown) and with GPS satellites. Features 7-11 have the same purpose as described in figure 3b.

Figure 3b17 shows the vessel is connected via securing cables (8) to a buoyancy chamber (7) from which is suspended a large diameter pipe (12) extending into the deeper, colder, nutrient-rich water. Wave-action supported by the non-retum valve (13) and on-board pumps draw the cold water up the pipe and into the de-aeration plant via a pressurised tube (9). Carbon dioxide and other gases liberated by the drop in water pressure and the de-aeration equipment are pumped back via the gas line (10) down to depth (15) where it is retained. The nutrient-rich water is sprayed onto the surface from the nozzles (11) to provide natural nutrients to the developing crop. A pair of stabilising cables (14) attached to the bows of the vessel maintains the vertical attitude of the tube as it moves slowly through the water.

*Optionally the power can be derived from OTEC (Ocean Thermal Energy Conversion) with the necessary temperature gradient being enhanced by heating the surface water via a solar panel and raising it substantially above the temperature of the cooler, nutrient rich water being pumped up from below.

Figure 3c/7 is a depiction of a standard OTEC system illustrating the novel features of de-aerationlsequestration of liberated gas from the cold water and the use of nutrients from the cold water either by extraction or by discharging the nutrient rich water at the surface.

Warm water is pumped from the surface of the water (1) via an optional solar panel (2) (to increase the water temperature during sunlight hours) to a heat exchanger (3) where a Working Fluid is raised into a gaseous phase (4) and used to generate electricity by means of a turbine (5). Cold water is pumped from depth (7), de-aerated in (8) with the liberated gas being pumped (9) back down to depth (10) where it is sequestered back into the cooler water. The de-aerated cold water is pumped into a heat exchanger (11) which evaporates the Working Fluid back into the liquid phase allowing it to be pumped (6) back to repeat the process. The cold water extract from the heat exchanger is either processed to remove nutrients (12) or the nutrient-rich water is discharged to the surface (13) to organically fertilise the developing crop.

Detailed Description of the Invention

Containment, Aciitation and Fertiisation of Large Open Water Algae Plantations Containment Principles The key features of containment mechanism are:- > Concentrate the cultivation area of the algae bloom > Restrict the spread of nutrients horizontally > Contain the growing crop within a prescribed area > Establish physical boundaries for cultivation processes > Discourage predatory invasion from floating organisms > Intensify the cultivation region in the vertical water column > Define the ownership' of the crop The containment mechanism comprises linked sections of standard 1 kilometre lengths of neoprene/rubber material incorporating inflatable or foam-filled compartments along the top edge which provides the flotation and a chain sinker' along the bottom edge which stabilises the mechanism vertically in the water.

These sections are similar in construction to the heavy duty oil-spill containment booms used to recover oil from accidental spillage in the open sea. They utilise standard linking systems similar to those used in oil containment.

The principle of the containment boom is illustrated in figure Ia.

The linked sections form a completely enclosed area which can vary from a few square kiometres to hundreds of square kiometres. By the very nature of the open ocean environment, the shape of this area will be irregular as the effects of winds and currents act differently upon each section of the enclosure.

Some control of shape is desirable to maintain a single open area for harvesting and strategically deployed sea-anchors are used to achieve this open shape. These resist the effect of the prevailing wind on any given sections and help to preserve some open shape to the enclosure.

The concept of the enclosures is illustrated in figure lb. Agitation Principles The key features of the optional agitation mechanism are:- > Ensuring even exposure of the crop to both sunlight and nutrient supply Encouraging consistency of the crop at all appropriate depths > Increasing density of the crop to deter invasive species > Automated monitoring and reporting of the cultivation environment > Automated addition of trace nutrients that enhance the favoured species > Distributes but does not damage the crop cells > Minimum disruption of the water surface.

> Self-propelling and self-steering by means of controlled water jets > Intelligent with capability to receive and respond to remote instructions > Positionally aware (eg GPS, wireless coordinates etc) > Optionally can be naturally powered (e.g. Solar) or artificially powered.

Algae will develop to depths within the water column that depend upon the particular species, the amount of sunlight, the distribution of nutrients and other environmental factors.

Those growing at the lower depths will be increasingly shaded from the sun by those developing in size at the surface. Because of this and the other factors mentioned above, algal growth within the water column will be uneven unless natural or artificial mechanisms disturb this natural order.

Commercial cultivation on the scale necessary to provide algal biomass as a blo fuel feedstock requires some considerable degree of consistency in the harvested crop and a regular circulation of the algal growth within the water column will be required.

This is achieved by the deployment of unmanned cultivators that are programmed to move in a directed pattern of travel that regularly traverses the developing crop while continually circulating the algal growth within the water column.

Water is circulated in the water column by either pump action, paddle action or a combination of both depending upon the species and the depth of cultivation required. Key features of both water circulatory mechanisms is that they shall move large amounts of algae laden water gently so as to avoid damage to the crop and ensure that all algae within the water column are exposed to the same range of environments in terms of sunlight and nutrient supply.

Data remotely supplied from aerial survey coupled with automated sampling of nutrient levels on board the cultivator itself may trigger the release of nutrient supplements from the cultivator or optionally call up some other form of activity such as aerial delivery of specific supplements into a discrete area at a defined level. This continuous patrol, monitoring and cultivation of the crop is aimed at producing even and consistent exposure of the algae to the growing environment and to signal to the plantation management the state of the crop in terms of growth, maturity, nutrient levels and predatory threats.

The concepts of the Agitation Mechanisms are illustrated in figure 2a & figure 2b.

Fertilisation Principles The key features of the fertilisation mechanism are:- Organically compensate for low nutrient levels at the surface.

> Enhance the atmospheric CO2 take up by cooling the water surface > Extraction of cool, nutrient laden water from a set depth below the surface > Distribution of that cool nutrient laden water at the surface or, optionally, the separation and extraction of those nutrients & minerals.

Automated addition of trace nutrients that enhance the favoured species > Minimum disruption of the water surface.

> Self-propelling and self-steering by means of controlled water jets > Intelligent with capability to receive and respond to remote instructions > Positionally aware (eg GPS, wireless coordinates etc) > Optionally can be naturally powered (e.g. Solar, OTEC) or artificially powered.

> De-aeration of the rising water.

> Capture and sequestration of CO2 and other gases liberated as the deeper water is pumped up to the surface.

Where cooler, deeper water harbours nutrients not available at the warmer surface levels, the fertiliser mechanism is a means to transfer those nutrients for the benefit of the algal crops growing at or near the surface. This mechanism can be deployed centrally within the plantation, in plant located strategically around the plantation or in plant that moves slowly around the area of the plantation following a programmed or remotely directed route.

The fertilisation mechanism can also add controlled quantifies of trace elements that crop analysis (local or remote) has indicated is required to enhance the crop in that particular area.

It is anticipated that these units would operate unmanned apart from maintenance and the replenishment of trace elements. Positional knowledge is gained from on-board GPS with communication, data transfer and control via wireless links to a control centre.

Power for the pumping and for the propulsion is derived from solar energy (either solar cells or OTEC*) with battery storage of energy enabling 24 hour operation of the system.

Water pumped up from lower depths will liberate gases such as CO2 and removing these gases from solution is further enhanced by de-aeration plant at the surface.

This can either be active or passive de-aeration with the liberated gases being trapped and pumped back down to depth where they can again be sequestered.

Vertical separation is required between the bottom of the water intake and the gas discharge outlet to enable the gas to be absorbed by the surrounding water rather than being taken directly back up the inlet pipe.

The cool, de-aerated water is sprayed over the crop providing enhanced nutrient levels to aid the crop development.

Alternatively, the nutrients can be extracted from the water pumped from depth and stored for wider distribution as required within the cultivated area.

Release of the stabilising cables will allow the bottom of the tube to swing into a more horizontal position to enable rapid repositioning, towing or securing during periods of excessive surface turbulence.

The concepts of the Fertilisation Mechanism are illustrated in figure 3a & figure 3b.

*The concepts illustrating the novel adaptation of the Ocean Thermal Energy Transfer (OTEC) principle to sequester liberated gases and to extract nutrients to aid the cultivation of the algae crop are illustrated in figure 3c. Utilising this technology will not only provide the power for the Fertilisation Mechanism but will provide additional supplementary power to drive additional processes associated with the open water algae plantation.

Claims (4)

1. Claims 1) Linked floating booms that have the explicit role of enclosing and containing large scale algae plantations located in the open ocean, limiting the surface spread of applied nutrients and providing some level of protection against predatory' floating organisms.
2. 2) Strategic deployment of sea anchors to provide a level of control of the shape of the linked booms according to claim I whereby the anchors are deployed to optimise the open structure of the enclosure and prevent prevailing winds from closing up the sides of the enclosure.
3. 3) Unmanned agitation vessels that traverse the enclosure according to claim I and circulate the developing crop in the vertical column to ensure even exposure to sunlight and to available nutrients.
4. 4) Unmanned fertilisation mechanisms that bring up nutrient rich cold water to the surface, sequester liberated gases back to depth and distribute nutrients across the enclosure according to claim I.