EP2667963B1

EP2667963B1 - A fluid agitator device for facilitating development of algae or micro-algae in trays or photobioreactors

Info

Publication number: EP2667963B1
Application number: EP11807759.3A
Authority: EP
Inventors: Enrico Zaglio
Original assignee: ASTRA Srl
Current assignee: ASTRA Srl
Priority date: 2010-12-09
Filing date: 2011-12-09
Publication date: 2016-06-29
Anticipated expiration: 2031-12-09
Also published as: ITMI20102263A1; WO2012077081A1; IT1403095B1; CN103347599B; CN103347599A; EP2667963A1

Description

The present invention relates to a fluid agitator device for facilitating development of algae or micro-algae in trays or photobioreactors. By the terms trays or photobioreactors, reference is made also to basins, fermenters and other devices suitable for cultivation of algae and micro-algae. The invention is applicable for example in cultivation of algae, micro-algae or like organisms which are suitable for or usable for production of oils, biomasses, bio-fuels, feeds etc. The use of biomasses as renewable energy sources is known, for example by combustion thereof for generating electrical energy, or by means of gasification and subsequent combustion, or for obtaining oils that can be used for combustion or for the production of bio-fuels. As sources for production of bio-masses, the prior art comprises the use of maize, soya, canola (a variety of rape-seed), jatropha (Barbados nut), hazel nuts, oil palm, but the best performance in terms of litres of oil produced per unit of surface dedicated to cultivation is obtained with specific known varieties of algae or micro-algae, such as for example clorella prototecoides (which can be grown either autotropically or heterotropically), nannochloropsis, isochrysis (T-ISO), tetraselmis suecica, or others besides.
Micro-algae are photosynthetic vegetal organisms (i.e. which actuate photosynthesis), unicellular and aquatic, which exhibit dimensions of generally less than 30 µm and, differently to the majority of green plants, can convert solar or light energy into carbohydrates or fats. Micro-algae, like all oxygenic photosynthesisers, grow by using water as a source of electrons, mineral salts and carbon dioxide as nutrients and solar radiation as a source of energy, and exhibit a considerably more rapid growth with respect to terrestrial plants.
These microalgae are therefore particularly suitable for absorption of atmospheric CO₂, for production of bio-fuels, for purification of civic and agro-zoo-technical waste and for the production of biomolecules. Microalgae of various species are already produced commercially in various countries and used for production of food integrators, feedstuffs, pigments, fatty acids, ω3, biomasses for acquaculture and for treatment of waste.
Not all strains of algae or micro-algae are suitable for massive culture, and therefore obtaining suitable strains for massive culture requires careful selection and a long acclimating. Some cyanobacteria, such as spirulina and klamath are usually denominated using the term micro-algae. Algae, after cultivation and harvesting, can be subjected to various processes such as flocculation, decanting and centrifuging such as to obtain an algae paste, after which an extraction process is applied, by pressing or use of solvents, for obtaining an oil having a production of about 15-30 tonnes per annum per hectare of terrain used for cultivation thereof. As well as oil, panels can be extracted from algae which can be used for obtaining feeds, biogas or other products, in quantities of the order of 60 - 90 tonnes per hectare per year. For the cultivation of micro-algae, use is known of cultivating trays in the open, which comprise large trays filled with water in which micro-algae to be cultivated are present, which are directly exposed to the sun's rays. The tray exhibits a large surface area, a modest depth (as light penetrates with difficulty through the layer of developing micro-algae, generally not more than 2 cm from the surface), and are generally provided with a motorised propeller arranged in a portion of the tray such as to enable displacement of the microalgae and also enable the micro-algae present at a greater depth to rise periodically to the surface of the water. The known trays are not expensive, but exhibit some drawbacks, among which a modest productivity, occupation of a large area, though less than the area occupied by other vegetable species, the need to be located in climatically suitable territories, the difficulty of maintaining the parameters of cultivation close to optimal values, the possibility of contamination, the possibility of developing insects. A known alternative solution for the cultivation of algae and micro-algae consists in the use of photo-bio-reactors, i.e. containers or close circuits, generally tubular, usually having transparent walls, containing water and algae or micro-algae which can be cultivated in optimal developing conditions and with chemical-physical and biological parameters that are controlled and optimal. In these culture systems, apart from provision of adequate illumination, the temperature has to be controlled such as to guarantee efficient transfer of the masses of algae and to limit contamination. The photobioreactors can be provided with various devices such as an automatic control system, pumps for circulation of the water, filters etc., for enabling control and maintenance of the optimal cultivation parameters.
Various types of photobioreactors are known, which can for example be flat panels, horizontal tubes, inclined tubes, helices, and so on. For example, panel photobioreactors are constituted by rectangular recipients, arranged vertically, having a breadth comprised between 1 and 5 cm, made of glass or Plexiglas, in which the algae are maintained in suspension by an air flow introduced generally via a special tube located low down, and are collected from above. Photobioreactors enable a greater productivity in terms of cultivation of algae and micro-algae, also thanks to a greater photosynthesising performance thanks to the greater surface of the algae exposed to solar radiation, the possibility of automatic control of the cultivation process; they also have a smaller environmental impact, can be located in many more geographical environments, and occupy a much smaller space than trays out in the open.
These photobioreactors however exhibit some drawbacks, such as costs of realisation and management that are much higher, a greater energy consumption and expensive maintenance. These photobioreactors further involve an accumulation of oxygen which must be removed from the photobioreactors, and are subject to increases in temperature due to the reactions that occur in them, requiring cooling systems (shading, spraying with atomised water etc). The high costs of maintenance of these types of cultures limit their use only in massive cultures of great purity, required for extraction of biomolecules having a high commercial value, and for inoculation in open systems.
Also known is the use of solar concentrators in combination with the photobioreactors, such as to concentrate solar radiation and cause it to penetrate more greatly among the algae; however, these solar concentrators are complicated and expensive. Examples of prior art fluid agitators are described in US2009/0321369 A1 and EP-A-0261533 .
In this situation, an aim of the present invention is to make available a fluid agitator device for facilitating the development of algae or micro-algae in trays or photobioreactors, which obviates one or more of the above-cited drawbacks. A further aim of the present invention is to realise an agitator device which enables reducing the area required for cultivation of algae or micro-algae. A further aim of the present invention is to realise an agitator device which enables increasing production of algae or micro-algae.
A further aim of the present invention is to realise an agitator device which enables a reduction in energy consumption required for cultivation of algae or micro-algae.
A further aim of the present invention is to realise an agitator device which is simple and economical to maintain.
A further aim of the present invention is to realise an agitator device which has a smaller environmental impact.
A further aim of the present invention is to realise an agitator device which is simple and economical to realise, and which enables a reduction in overall cultivation costs of the algae or micro-algae.
These aims and others besides, which will better emerge from the following description, are substantially attained by an agitator device for facilitating development of algae or micro-algae in trays or photobioreactors, according to what is expressed in one or more of the accompanying claims, taken alone or in combination among themselves, or in combination with any one of the further aspects or characteristics as described herein below, taken alone or in any combination among them.
The invention further relates to a device according to one or more of the attached device claims, along or in combination among them, or with any one of the further aspects indicated herein, wherein a photovoltaic module or a plurality of photovoltaic modules are mounted on a support solidly constrained to an agitator element and mobile together with the agitator element.
The invention further relates to a device according to one or more of the attached device claims, along or in combination among them, or with any one of the further aspects indicated herein, wherein the agitator device further comprises a light guiding device, or a solar conveyor, suitable for collecting a light radiation and conveying it to at least a portion of the agitator element and therefore onto the algae or micro-algae.
The invention further relates to a device according to one or more of the attached device claims, along or in combination among them, or with any one of the further aspects indicated herein, wherein the agitator element is rotatably mounted and activatable in rotation by means of the motor and/or comprises a shaft by means of which it is rotatably mounted to the support element. The invention further relates, in a further aspect thereof, also in combination with any one of the accompanying claims, a fluid agitator device for facilitating the development of algae or micro-algae in trays or photobioreactors, the device comprising at least an actuator device, at least a support element on which the actuator device is mounted, and at least an agitator element mobilely or rotatably mounted on the support element and activatable by means of the actuator device and at least partially insertable in a tray of water or in a photobioreactor in order to move algae or micro-algae contained in the tray of water or photobioreactor.
The actuator device can comprise at least a photovoltaic module suitable for absorbing a light radiation in order to produce electrical energy and at least a motor powered by the photovoltaic module.
The actuator device can comprise a wind turbine and/or an element configured such as to be actuable in rotation by wind. The actuator device can comprise other types of activation operatively active such as to move the agitator element.
The invention further relates to a process according to one or more of the accompanying process claims, alone or in combination with one another, or with any one of the further aspects indicated herein, further comprising a step of removing at least an agitator device damaged by a tray or photobioreactor and to replace it with a further functioning agitator device.
By way of non-limiting example, a detailed description follows of one or more preferred embodiments of a device according to the invention, in which:

figure 1 is a perspective view of an agitator device according to a first embodiment of the present invention;
figure 2 is a perspective view of an agitator device according to a second embodiment of the present invention;
figure 3 is a view in longitudinal section of the device of figure 2;
figure 4 is a perspective exploded view of the device of figure 2;
figure 5 is a perspective view of a plurality of agitator devices according to an embodiment of the invention, inserted in a tray for cultivation of micro-algae or photobioreactors.

In the present text the term tray is taken to mean any open container suitable for containing liquid and for cultivation of algae, micro-algae or the like, and therefore also basins and the like, while the term photobioreactor is taken to mean any closed container suitable for cultivation of algae, micro-algae or the like. The terms algae or micro-algae are intended to comprise various forms of vegetable life suitable for being cultivated in water in trays or photobioreactors and usable for producing biomasses, biofuels, or the like. During the course of the following non-limiting description of some embodiments of the invention, reference number 1 refers in its entirety to a fluid agitator device for facilitating the development of algae or micro-algae in trays 20 of water or photobioreactors. The agitator device 1 can comprise at least an actuator deice 2. The agitator device 1 or the actuator device 2 can comprise at least a photovoltaic module 3, for example a photovoltaic panel, suitable for absorbing a light radiation in order to produce electrical energy. In the illustrated examples of the figures, two photovoltaic panels are shown for each agitator device 1. The agitator device 1 or the actuator device 2 can comprise at least a motor 4 which can be operatively connected to the photovoltaic module 3. The motor 4 can be for example electrical and is not described in greater detail as it can be of any known type suitable for the purpose. The agitator device 1 can comprise at least an agitator element 5 mobile and activatable by means of the actuator device 2 or the motor 4 and at least partially insertable in a tray 20 of water or in a photobioreactor such as to move algae or micro-algae contained in the tray 20 of water or in the photobioreactor.
In a variant which is not illustrated, the actuator device 2 can comprise a wind turbine and/or an element configured such as to be activatable in rotation by the wind such as to move the agitator element 5. The actuator device 2 can comprise other type of activation operatively active such as to move the agitator device 5. The agitator device 1 can further comprise at least a lighting device 6, for example of a LED type, destined to illuminate the algae or micro-algae.
The lighting device 6 can be operatively connected and supplied by the photovoltaic module 3 or by the actuator device 2. The lighting device 6 or the plurality of lighting devices can be mounted on the agitator element 5 or inside the agitator element 5 such as to move solidly with the agitator device 5 and illuminate the algae or micro-algae. In a further embodiment, not illustrated, the agitator device 1 can further comprise at least a light guiding device, or a solar conveyor, destined to collect a light radiation and convey it to at least a portion of the agitator device 5. The agitator device 1 can further comprise at least a support element 7 on which the agitator device 5 and/or the actuator device 2 and/or the photovoltaic module 3 and/or the motor 4 can be mounted mobile or rotatably. The actuator device 2 and/or the photovoltaic module 3 and/or the motor 4 can be mounted on the support element 7 at an upper surface 7a of the support element 7. The agitator device 5 can be mounted at a lower surface 7b of the support element 7 opposite the upper surface 7a. The agitator element 5 can be rotatably mounted and activatable in rotation by means of the actuator device 2 or the motor 4. The agitator device 5 can comprise a rotation shaft 8 by means of which the support element 7 is rotatably mounted. The rotation shaft 8, as illustrated in the figures, can be constituted by several parts assembled together and can be mounted on the support element 7 by means of conventional bearings and by means of any other structure that is suitable for the aim. The shaft 8 can be internally hollow and bear internally thereof electric supply cables for lighting devices 6 housed in the agitator device 5. The support element 7 can be destined and configured such as to float on the water of a tray 20 of water or a photobioreactor. The support element 7 can support and maintain at least an actuator device 2 and/or the photovoltaic module 3 and/or the motor 4 above the free surface of the water. At least a portion of the support element 7 can be made of a transparent material, such as to allow passage of light radiation through the support element 7 and better illuminate the algae or micro-algae in the tray 20 or photobioreactor. The agitator device 1 can further comprise a support 9 on which at least the actuator device 2 and/or photovoltaic module 3 and/or the motor 4 can be mounted. The support 9 can be mounted solidly to the agitator element 5 and be rotatably mounted on the support element 7 such as to rotate together with the agitator element 5 following the action of the motor 4. The photovoltaic module 3 or a plurality of photovoltaic modules can be mounted on the support 9 solidly constrained to the agitator element 5 and mobile together with the agitator element 5. The motor 4 can be provided with activating means 20, for example comprising a pulley or a cogged wheel, engaged with engaging means 11, for example a fixed cogged crown wheel, of the support element 7 such as to move with respect to the support element 7 and move at least the agitator element 5. The agitator device 1 can further comprise a covering element 13 destined to close, cover and protect, for example, the motor 4, activating means 10 and engaging means 11. The covering element can be fixed to the support element 7 and can develop about the support 9 such as to define a closed solid and not to enable access to some parts of the agitator device 1.
The agitator device 5 can comprise a plurality of projecting elements 12 destined to agitate the algae or micro-algae. The projecting elements 12 can be mounted on the rotation shaft 8 rotatably mounted on the support element 7. At least one of the projecting elements 12 can be made of a transparent material, for example Plexiglas or another material, and can be provided internally with at least a lighting device 6, preferably a LED, which can be supplied by the photovoltaic module 3. In the embodiment illustrated in the figures, each projecting element 12 is transparent and provided with a plurality of LED lighting devices 6. Each projecting element 12 can be for example a hollow and transparent tubular body, in which the LED lighting devices 6 powered for example by the photovoltaic panel are housed.
The projecting elements 12 can develop transversally or perpendicularly to the rotation axis of the agitator element or shaft 8. The LED type can be of a sort which emits light radiation at specifically researched frequencies for increasing the growth of vegetables or micro-algae and/or the process of photosynthesis. As illustrated in the accompanying figures of the drawings, the agitator device 1 can be realised in a single module, removably insertable in a tray 20 of water for cultivation of algae or micro-algae in a photobioreactor.
As illustrated in figure 5, the agitator device 1 can be configured such as to float in a tray 20 of water or photobioreactor. The structural parts of the agitator device 1 not illustrated in greater detail in the present description are to be taken as being constituted by elements of essentially known and conventional type. The agitator device 1 can exhibit overall dimensions of less than 5 metres x 5 metres x 5 metres or less than 2 metres x 2 metres x 2 metres or less than 1.5 metres x 1.5 metres x 1.5 metres. For example, the overall dimensions can be about 1 metre x 1 metre x 1 metre.
The invention further relates to a use of an agitator device 1 of the above-mentioned type, at least partially immersed in a tray 20 of water or in a photobioreactor such as to encourage development of algae or micro-algae contained in the tray 20 and/or for agitating and/or illuminating and/or facilitating cultivation of unicellular algae, for example clorella prototecoides, or others besides.
The invention further relates to a tray 20, to a basin or a photobioreactor, or the like, for cultivating algae or micro-algae comprising at least an agitator device 1 of the above-described type. In a preferred embodiment the agitator device 1 can be freely mobile, without constraints, in the water contained in the tray 20.
The invention further relates to a process of realising a tray 20 for cultivation of algae or micro-algae or a photobioreactor comprising at least the steps of inserting algae or micro-algae to be cultivated in a tray 20 or photobioreactor containing water, removably inserting, in the tray 20 or photobioreactor, at least an agitator device 1 or a plurality of agitator devices of the above-described type.
The process can further comprise a step of maintaining the tray 20, comprising the step of removing at least an agitator device 1 damaged by the tray 20 or photobioreactor, and replacing it with another functioning agitator device.
The present invention enables at least one of the above-cited aims to be attained.
The invention enables increasing the productivity of a the cultivations of algae and micro-algae and thus of significantly reducing the area required for cultivation of the algae or micro-algae. The invention further enables reducing the energy consumption required for cultivation of algae or micro-algae and exhibits a smaller environmental impact.
The invention further exhibits very low maintenance costs and great ease of operations.
The invention further enables a significant reduction of overall cultivation costs of the algae or micro-algae to be made.
The invention enables increasing the number of geographical locations in which algae or micro-algae can be cultivated.
The invention further enables automatically respecting pauses is photosynthesis, by not lighting the algae or micro-algae in dark conditions.
The invention is also simple and economical to realise.

Claims

A fluid agitator device for facilitating development of algae or micro-algae in trays (20) or photobioreactors, the device comprising at least an actuator device (2) having at least a photovoltaic module (3) destined to absorb a light radiation in order to produce electric energy and at least a motor (4) which is operatively connected to the photovoltaic module (3); and further comprising at least an agitator element (5) which is mobile and activatable by means of the motor (4) and is at least partly insertable in a tray (20) containing water or in a photobioreactor for moving algae or micro-algae contained in the tray (20) or photobioreactor, the device being characterized in that it comprises at least a lighting device (6) or at least a LED type lighting device (6) designed and destined to illuminate the algae or microalgae.
The device of claim 1, wherein said at least a lighting device (6) or at least a LED type lighting device (6) is operatively connected to and supplied by the actuator device (2) or by the photovoltaic module (3).
The device of claim 1 or 2, wherein the lighting device (6) and/or the plurality of lighting devices are mounted on the agitator element (5) or internally of the agitator element (5) such as to move solidly with the agitator element (5) and illuminate the algae or microalgae in the tray (20).
The device of any one of the preceding claims, further comprising at least a support element (7) on which the agitator element (5) and/or the actuator element (2) and/or the photovoltaic module (3) and/or the motor (4) are movingly or rotatably mounted.
The device of claim 4, in which the actuator device (2) and/or the photovoltaic module (3) and/or the motor (4) are mounted at an upper surface (7a) of the support element (7) and the agitator element (5) is mounted at a lower surface (7b) of the support element (7) opposite the upper surface (7a).
The device of claim 4 or 5, wherein the support element (7) is designed and configured such as to float on the water of a tray (20) of water or a photobioreactor and/or the support element (7) is destined and configured such as to float on the water of a tray (20) of water or photobioreactor supporting and maintaining at least the actuator device (2) and/or the photovoltaic module and/or the motor (4) above the free surface of the water
The device of any one of claims from 4 to 6, and/or wherein at least a portion of the support element (7) is made of a transparent material.
The device of any one of claims from 4 to 7, further comprising a support (9) on which at least the actuator device (2) and/or the photovoltaic module (3) and/or the motor (4) are mounted, the support (9) being mounted solidly to the agitator element (5) and rotatably mounted on the support element (7) in order to rotate together with the agitator element (5) following the action of the actuator device (2) or the motor (4) and/or in which the motor (4) is provided with activating means (10) engaged with engaging means (11) of the support element (7) in order to move with respect to the support element (7) and to move at least the agitator element (5).
The device of any one of the preceding claims, wherein the agitator element (5) comprises a plurality of projecting elements (12) destined to agitate the algae or microalgae and/or mounted on a rotating shaft (8) rotatably mounted on a support element (7) and/or in which at least a projecting element of the projecting elements (12) is made of a transparent material and is internally provided with at least a lighting device (6) or at least a LED type lighting device (6), preferably supplied by the photovoltaic module (3).
The device of any one of the preceding claims, characterised in that it is made in a single module, removably insertable in a tray (20) of water for cultivation of algae or microalgae or in a photobioreactor and/or in that it is configured such as to float in a tray (20) of water.
The device of any one of the preceding claims, characterised in that it exhibits overall dimensions that are less than 5 metres x 5 metres x 5 metres or less than 2 metres x 2 metres x 2 metres or less than 1.5 metres x 1.5 metres x 1.5 metres.
The device of any one of the preceding claims, further comprising a light guiding device, or a solar conveyor, suitable for collecting a light radiation and conveying it to at least a portion of the agitator element and therefore onto the algae or micro-algae.
Use of an agitator device (1) as in any one of the preceding claims, at least partially immersed in a tray (20) of water or in a photobioreactor such as to facilitate development of algae or microalgae contained in the tray (20) and/or to agitate and/or illuminate and/or facilitate cultivation of single-cell algae, for example clorella prototecoides.
A tray or photobioreactor for cultivation of algae or microalgae comprising at least a device as in any one of claims from 1 to 12 and/or comprising at least a device, as in any one of claims from 1 to 12, freely mobile, without constraints, in the water contained in the tray (20).
A process for realising a tray (20) for cultivating algae or microalgae or a photobioreactor comprising steps of:
inserting algae or microalgae to be cultivated in a tray (20) or a photobioreactor containing algae, removably inserting, in the tray (20) or photobioreactor, at least an agitator device (1) or a plurality of agitator devices as in any one of claims from 1 to 12.