Field of the Invention

The present invention relates to an installation and method for recovering of energy in an installation that pumps water from a lower water level into a water tank, and where parts of the energy is recovered via turbines arranged in the water flow out of the water tank. Preferably, the water tank is designed for breeding of marine organisms.

The Background of the Invention.

With the major environmental problems accompanying farming at sea, new solutions are being developed to bring farming into facilities on land. This means that water must be pumped from a low level, e.g., sea, and typically 10 m up into large vessels. There are often large quantities of water involved with correspondingly large energy costs.

The facilities have different water requirements, all depending on how large a water exchange is planned. This may be anything from full flow-through, where the water flows like a river through a longitudinal flow vessel, to facilities designed as RAS facilities where the water is recycled in a loop for water treatment and is reused, and where only a few % of new water is pumped in and out. The breeder determines this based on the degree of cleaning that is planned. Particularly determining, is the amount of CO2 and particles accumulating in the water when the pump capacity and flow-through of water is reduced. The energy accounts of these facilities are therefore a challenge and represents a large cost.

The fact that these facilities are scattered along the coast where the power grid already has little capacity, is also a major problem. Therefore, there are also large costs associated with the construction of new infrastructure to transport electrical power to these facilities. Objective of the Present Invention

Thus, it is an objective to provide a solution for recovery of parts of the energy used to pump water from a lower level up to the water tank.

It is also a purpose of the present invention to calculate how much water must be pumped up into the water tank, and how much water flows out of the water tank, based on quality parameters of the water, so that intake and discharge of water may be regulated based on an optimization of the water parameters for the breeding of marine organisms.

Summary of the Invention

Thus, one aspect of the invention relates to an installation for the recovery of energy, in a land-based water tank that uses energy to move water up to a higher level than the starting point, and where the water in the water tank flows back to a lower level than in the water tank, where the installation includes one or more pumps to bring the water up, as well as one or more water turbines arranged in a water flow that flows back to a lower level, to recover energy, wherein the amount of water pumped into the water tank is optimized for high efficiency of turbines based on water parameters of the water in the water tank.

In one embodiment, the installation is located in a facility for breeding of marine organisms.

In one embodiment, the installation is placed in a flow-through facility for breeding of marine organisms.

In one embodiment, water parameters in the water tank for breeding of marine organisms are optimized with water treatment methods such as CO2 aeration, skimming of particles, addition of O2, vacuum aeration of water, amount of NH3 or other relevant water parameters. In one embodiment, the energy generated from the generator is used directly in the facility or is fed into the power grid.

In one embodiment, the energy recovered from the generator partially drives the pumps. In one embodiment, one or more turbines receive water from several vessels so that the turbines can be operated with a high degree of efficiency under different operating conditions with different amounts of water pumped into water vessels.

In one embodiment, the installation is located adjacent to a water basin where floating units for the breeding of marine organisms are located.

In one embodiment, pumps and turbines are of matching efficiency so that a water pump (3) may pump water up into a water reservoir and a turbine is adapted to the same amount of water for optimal efficiency and that several matching pumps and turbines may be installed in a facility.

In another aspect, the present invention relates to a method for recovering of energy in a facility in a land-based water tank (1 ) that uses energy to move water up to a higher level than the starting point, and where the water in the water tank (1 ) flows back to a lower level than in the water tank (1 ), where the installation comprises one or more pumps (3) directed to pump the water up into the water tank (1 ), as well as one or more water turbines (2) which are arranged in a water flow flowing back to a lower level, for recovery of energy from the water flow that flows back to lower level, characterized by that the amount of water pumped into the water tank is optimized against high efficiency of turbines based on water parameters in the water in the water tank (1 ).

In one embodiment, the installation is located in a facility for breeding of marine organisms.

In one embodiment, the installation is placed in a flow-through facility for breeding of marine organisms.

For breeding marine organisms in the water tank, the amount of water supplied to the water tank is preferably determined based on the amount of CO2 and particles in the water. By measuring and calculating the water parameters CO2 and particles in the water, it is possible to determine the amount of water in and out of the water tanks, and thereby decide which pumps and turbines should be activated.

In one embodiment, water parameters in the water tank for breeding of marine organisms are optimized with water treatment methods such as CO2 aeration, skimming of particles, addition of O2, vacuum aeration of water, amount of NH3 or other relevant water parameters, and that this determines the amount of water taken up into the tank.

In one embodiment, the energy generated from the generator is used directly in the facility or is fed into the power grid.

In one embodiment, the energy recovered from the generator partially drives the pumps. In one embodiment, one or more turbines are operated which receive water from several vessels with a high degree of efficiency under different operating conditions with different amounts of water pumped into water vessels.

In one embodiment, the installation is located adjacent to a water basin where floating units for the breeding of marine organisms are located.

In one embodiment, pumps and turbines are matched in efficiency so that a water pump may pump water up into a water reservoir and a turbine is adapted to the same amount of water for optimal efficiency and that several matching pumps (3) and turbines (2) may be installed in a plant.

Description of the Figures

Below, preferred embodiments of the invention will be discussed in more detail with reference to the attached figures, where:

Figure 1 shows the main components of the installation, i.e., pump that pumps the water from the sea (at lower level) to the water tank, and the generator recovers some of the energy as the water is carried from the water tank back to the sea, and the energy accounts. Figure 2 shows a configuration where water is pumped to a higher level which is controlled by a level gauge or overflow. The reference numbers in the figure are; 1 ) production unit, 2) electric water turbine, 3) water pump, 4) water intake, 5) outlet, 6) lift height and drop height, and 7) height production unit.

Figure 3 shows a facility where the pump height changes according to the ebb and flow of the tides. The reference numbers in the figure are; 1 ) production unit, 2) electric water turbine, 3) water pump, 4) water intake, 5) outlet, 6) lift height and drop height, 7) height of production unit, 8) HAT (Highest Astronomical Tide) and 9) Mean Water Level.

Figure 4 shows how several tanks are connected at the outlet in a common outlet line.

Figure 5 shows details of a water tank.

Figure 6 shows a solution for a longitudinal flow facility.

Figure 7 shows a solution where a water vessel floats in another water reservoir.

Description of Preferred Embodiments of the Invention

The description below is a description of certain embodiments of the invention. The scope of protection of the invention is defined by the accompanying patent claims.

Figure 1 shows the main components of the solution, where a pump (3) pumps water (4) from the sea into a tank (1 ). The outlet from the tank at level (7) returns to the sea through a generator (2). This generator (2) supplies power to the motor (10) which drives the pump (3) or delivers back to the power grid. Electric power to drive the pump (3) is obtained from the public grid. Recovered energy in generator (2) may be delivered back to the public grid or used to operate pump (3).

Figure 2 shows a typical configuration where water is pumped through (3) into tank (1 ) to a level (7) where there is a level gauge or preferably an overflow that controls this. From the overflow, the water returns through the generator (2) before returning to the sea.

When taking water from the sea, the pump height will change in line with the ebb and flow of the tides. This is illustrated in Figure 3. Precisely the definition of whether a facility is at sea or on land is a core question in today's development of land-based flow-through facilities, because the energy costs associated with pumping water are so high.

Figure 3 shows a typical facility for breeding of marine organisms based on the flow- through principle. The need for water may be very large, depending on how much biomass of the marine organisms are present in the water. For example, in relation to salmon farming, the question of how high the fish tank (1 ) should be located above sea level is widely discussed. The Ministry of Fisheries have emphasized that the fish tank (1 ), also called the production unit, must be located above HAT, which is Highest Astronomical Tide.

A clarification from the Directorate of Fisheries (ref .1 .)

Based on this, it is possible to point out some obvious typical examples of aquaculture facilities at sea and on land. An aquaculture facility will clearly be "at sea" if the production unit(s) floats/float in the sea, stands/stand on the seabed, or is surrounded by sea. An aquaculture facility will also clearly be "on land" if the production unit(s) is/are on solid ground or on filled masses on an area of the earth's surface that is not covered by water, if also the lowest level (bottom) of the production unit(s) is/are at a level above Highest Astronomical Tide (HAT) of the sea such that there is no direct connection between the production unit and the sea.

The facility in Figure 3, is in accordance with the Ministry of Fisheries' guidelines for farming on land. The definitions, that the bottom of the production unit (1 ) must be above HAT have been met and this means that the vessel height (7) itself is in addition to how high HAT is above mean water level. A typical vessel may have a height of 6 m and then approximately 1.5 m in addition, which is the difference between HAT and mean water level. This means that it is necessary to pump water up an average of 7.5 m. The calculation example below shows the energy needed to pump a certain amount of water up to a level of 7.5 m.

The amount of water to be pumped into the vessel is given by the biomass (amount of fish) in the facility. For example, a vessel may contain 5000 m ³ of water. There may be up to 100 kg of fish/m ³ of water, which means that such a vessel may hold up to 500,000 kg of fish. Water must be replaced to such an extent that, e.g., the Norwegian Food Safety Authority's maximum levels are not exceeded. In most cases, O2 must also be added to such a vessel. A typical requirement from breeders, is that the CO2 levels in the tank do not exceed 15 mg/L water.

It may be assumed that fish will secrete approximately 400 g of CO2/kg of feed given to the fish. Typically, a large fish can eat approximately 0.8% of its body weight per day. This means that in this tank, the fish will produce large amounts of CO2 which must be regulated by replacing the water or removing it through degassing.

500,000 kg of fish x 0.8% feed x 412 g = 1 ,648,000 grams of CO2 124 hours 1 ,648,000 grams 1 24 = 68,667 gram/hour (68,667,000 mg/hour)

At a maximum level of approximately 15 mg/L water, it is then necessary to remove as much CO2 from the vessel as is produced by the fish. This means that at 15 mg/L water leaving the vessel, the following amount of water must be removed from the vessel: 68,667,000 mg/CO2 produced I 15 mg/L = 4,577,777 L of water out every hour. This means that the same amount of new water must be pumped in. This gives 4,575 m ³ /h of new water in per hour, which corresponds to 1272 L/s new water into the facility.

When considering the cost of this when the height from which the water is collected to the water level water is pumped up to, is 7.5 m, we typically get;

P = Q- H - 9.81

• P = Power transmitted to the fluid by the pump in Watts.

• Q = Flow in m ³ /s.

• p = Density of the liquid in kg/m ³ . H = Piezometric height in meters of water.

9.81 = Average Intensity of gravity.

P = 1272 l/s x 1025kg/M3 x 7.5 x 9.81 = 96 kW. When estimating an efficiency of 80%, a pump of approximately 1 15 kW is needed to lift the water. Friction in pipes, etc., is not taken into account here. This will result in a cost of, at a price of NOK 1 /kW, approximately NOK 1 ,007,000 /year for the work of lifting the water up 7.5 m.

Several articles have been written in www.kyst.no and ilaks.no (ref.1 ) addressing the unreasonable nature of requirements that breeders put their facilities above HAT. Arguments for placing them buried, so that the level in the production unit is at the same level as the sea, is that you avoid the cost of pumping water to a higher level.

Figure 4 shows how several tanks are connected together at the outlet in a common outlet line I outlet basin that leads the water into a set of generators (2) and pumps (3). The equivalent for the longitudinal flow basin is shown in Figure 6.

A pump is most efficient at a given amount of water and a given pressure. The same applies to a turbine. As Figure 4 shows, different pumps and turbines will be placed in parallel where they have different capacities, where one typically has half the capacity of the other. When the amount of water varies, it will then be possible to run them individually and typically obtain 50% and 100% water capacity, and by running both obtaining 150%. The water demand in a farming facility is predictable and constant for long periods. The proposed solution will therefore achieve high energy recovery, which will help considerably in reducing operating costs.

In addition, the solution in Figure 5 shows details around a tank where water is fed in through intake (4) through pump (3) and over and into the tank (1 ) in a siphon (11 ). A central cylinder (15) of a grid structure prevents the fish from entering the pipes leading water out of the tank through pipes (13) to an outlet basin (14) where the water is led further into the generator (2) and on to the outlet (5). The need for water supply, and thus energy costs, are decided primarily by the level of CO2 and particles in the water in the tank (1 ). By having devices that reduce this, it will also be possible to reduce the water consumption and thus the energy costs.

Fig. 6 shows an alternative solution for a longitudinal flow system where overflow (17) keeps the level constant in the water tank. The water flows into a collection channel at the same level, where water may come from several tanks. It then flows over an overflow (17) which ensures a constant level in the water tanks. This ensures that all water can be fed towards the turbine(s) (2) to ensure optimal utilization.

Such a device for reducing the level of CO2 and particles is shown in device (12) in Figure 5. One aspect of the invention is precisely that these combined degassers/skimmers (12) may be operated in such a way that an optimal water exchange is achieved, taking into account that pumps and generators may be run optimally where energy costs are in focus, while at the same time the water will meet the requirements of breeders and authorities. Variable water flow is a well-known problem at small power plants in Norway. Here, it is a complicated task to choose the right turbine as variation in the amount of water due to rainfall, etc., comes into play. In a land-based aquaculture facility, the amount pumped is fairly constant. This means that it is possible to obtain a very good degree of efficiency on the turbine. A drop height of 5-10 m is ideal for, e.g., a Kaplan turbine.

For example, it is possible to install pumps and turbines that have a matching optimum degree of efficiency. This means that it is possible to run 1 pump with a corresponding turbine. If 2 pumps are started, a corresponding turbine will be started, etc. This means that it is possible to run pumps optimally while at the same time achieving optimal utilization of the turbine(s). It is then possible to move from efficiencies of 40% to over 80% on both pump and turbines, which yield an enormous energy gain.

A turbine may have an efficiency of 80% which means that it may be possible to recover 80% of the energy used to pump up the water into the vessel. This provides a significant saving when pumping water. The solution as described in this invention combines different sizes of pumps and generators to recover energy from the wastewater in a farming facility where energy recovery may be optimized by also synchronizing the need for degassing/skimming of the water to optimize the water flow so that it best fits the performance characteristics of the combination of pump and generator and at the same time meets the demands of farmers and the authorities to water quality. This will provide large energy savings for the breeders. Recovered energy may be used locally in the operation of the facility or exported back to the power grid.