METHOD AND SYSTEM FOR UTILIZING HEAT IN A PLANT OR ANIMAL GROWING DEVICE, AND GREENHOUSE

Abstract

A method for utilizing heat in a plant or animal growing device includes circulating a heat transfer fluid through a circuit forming a closed fluid loop, heating, via a heat source, the heat transfer fluid in the fluid circuit to a temperature within an efficient operating range of a first heat unit, supplying heat from the heat transfer fluid to a first heat unit, the first heat unit cooling down at least part of the heat transfer fluid to a temperature within an efficient operating range of at least one additional heat unit connected in serial arrangement with the heat source and the first heat unit, supplying heat from the heat transfer fluid from the first heat unit to the additional heat unit, the additional heat unit cooling down at least part of the heat transfer fluid, and returning the cooled down part of the heat transfer fluid from the additional heat unit to the heat source in the fluid circuit.

Claims

1. A method for utilizing heat in a plant or animal growing device, comprising: circulating a heat transfer fluid through a circuit forming a closed fluid loop; heating, via a heat source, the heat transfer fluid in the fluid circuit to a temperature within an efficient operating range of a first heat unit; supplying heat from the heat transfer fluid to a first heat unit, the first heat unit cooling down at least part of the heat transfer fluid to a temperature within an efficient operating range of at least one additional heat unit connected in serial arrangement with the heat source and the first heat unit; supplying heat from the heat transfer fluid from the first heat unit to the additional heat unit, the additional heat unit cooling down at least part of the heat transfer fluid; and returning the cooled down part of the heat transfer fluid from the additional heat unit to the heat source in the fluid circuit.

2. The method according to claim 1, wherein: a heat fluid outlet temperature of one of the respective heat unit and the heat source equals a heat fluid inlet temperature of a following one of the respective heat unit and the heat source.

3. The method according to claim 1, wherein the first heat unit includes a thermal desalination unit, the additional heat unit includes a heating device of a medium of the plant or animal growing device, and wherein the heat transfer fluid is cooled down further to a temperature equal to or lower than an outlet temperature of the thermal desalination unit.

4. The method according to claim 3, wherein the heating device includes a crop heating device and/or a space heating device.

5. The method according to claim 1, wherein the first heat unit includes a thermal desalination unit, the additional heat unit includes a salt production device for producing salt from brine created in the thermal desalination unit, and wherein the heat transfer fluid is cooled down further to a temperature equal to or lower than an outlet temperature of the thermal desalination unit.

6. The method according to claim 1, wherein the first heat unit includes a steam cycle machine, the additional heat unit includes a thermal desalination unit, and wherein the heat transfer fluid is cooled by the first heat unit down from a starting temperature lower than or equal to an outlet temperature of the heat source to a temperature lower than or equal to an inlet temperature of the thermal desalination unit.

7. The method according to claim 6, wherein the steam cycle machine includes an organic rankine cycle machine.

8. The method according to claim 1, wherein at least part of the heat transfer fluid is temporarily stored in a heat buffer for later use in at least one of the heat units.

9. The method according to claim 1, wherein the heat source includes a solar driven heat source which is driven by concentrated solar power.

10. A system for utilizing heat in a plant or animal growing device, comprising: a fluid circuit including a pump and forming a closed fluid loop, wherein the pump is configured to circulate heat transfer fluid through the fluid circuit; a heat source configured to add heat to the heat transfer fluid in the fluid circuit; and a first heat unit configured to be heated by the heat transfer fluid in the fluid circuit to an efficient operating range of temperature of the first heat unit; at least one additional heat unit connected in serial arrangement with the heat source and the first heat unit, configured to be heated by the heat transfer fluid in the fluid circuit from the first heat unit to an efficient operating range of temperature of the additional heat unit.

11. The system according to claim 10, wherein the first heat unit includes a thermal desalination unit, the additional heat unit includes a heating device of a medium of the plant or animal growing device, and wherein the additional heat unit is disposed between an outlet of the thermal desalination unit and an inlet of the heat source.

12. The system according to claim 11, wherein the heating device includes a crop heating device and/or a space heating device of a greenhouse.

13. The system according to claim 10, wherein the first heat unit includes a thermal desalination unit, the additional heat user includes a salt production device for producing salt from brine created in the thermal desalination unit.

14. The system according to claim 13, wherein the salt production device includes a salt pond.

15. The system according to claim 10, wherein the first heat user includes a steam cycle machine, the additional heat unit includes a thermal desalination unit, and wherein the first heat unit is disposed between an outlet of the heat source and an inlet of the thermal desalination unit.

16. The system according to claim 15, wherein the steam cycle machine includes an organic rankine cycle machine.

17. The system according to claim 10, further comprising a heat buffer having a fluid inlet and at least one fluid outlet, wherein the fluid inlet is in direct fluid communication with the fluid circuit, and the at least one fluid outlet is in direct fluid communication with a fluid inlet of the heat unit and/or of the at least one additional heat unit.

18. The system according to claim 17, wherein the heat buffer includes a vertical tank, and wherein the vertical tank includes: the fluid inlet; and at least one heat transfer fluid take-off outlet disposed at a height between a top end of the vertical tank and a bottom end of the vertical tank, wherein the at least one heat transfer fluid take-off outlet is in direct fluid communication with the fluid circuit, wherein the height between the top end of the vertical tank and the bottom end of the vertical tank is selected such that a temperature of the heat transfer fluid at a respective one of the at least one heat transfer fluid take-off outlet is equal to or approximate to a temperature of the heat transfer fluid in a respective heat unit at a location where the heat transfer fluid from the respective take-off outlet is added to the fluid through the respective heat unit.

19. The system according to claim 10, wherein the heat source includes a solar driven heat source.

20. A greenhouse, comprising the system according to claim 10.

21. The method according to claim 1, wherein the first heat unit includes a thermal desalination unit, the additional heat unit includes a heating device of a medium of the plant or animal growing device, a salt production device for producing salt from brine created in the thermal desalination unit, and/or a steam cycle machine.

22. The method according to claim 21, wherein at least part of the heat transfer fluid is temporarily storable in a heat buffer for later use in at least one of the heat units, wherein the heat buffer includes a vertical tank, and wherein the vertical tank includes: a fluid inlet disposed at a top end of the vertical tank and connected to an outlet of the heat source; at least one heat transfer fluid take-off outlet disposed at a bottom end of the vertical tank and connected to an inlet of the heat source; and at least one fluid outlet connected to an inlet of a respective heat unit.

23. The method according to claim 1, wherein at least part of the heat transfer fluid is temporarily storable in a heat buffer for later use in at least one of the heat units, wherein the heat buffer includes a vertical tank, and wherein the vertical tank includes: a fluid inlet disposed at a top end of the vertical tank and connected to an outlet of the heat source; at least one heat transfer fluid take-off outlet disposed at a bottom end of the vertical tank and connected to an inlet of the heat source; and at least one fluid outlet connected to an inlet of a respective heat unit.

24. The system according to claim 10, wherein the first heat unit includes a thermal desalination unit, the additional heat unit includes a heating device of a medium of the plant or animal growing device, a salt production device for producing salt from brine created in the thermal desalination unit, and/or a steam cycle machine.

25. The system according to claim 24, wherein at least part of the heat transfer fluid is temporarily storable in a heat buffer for later use in at least one of the heat units, wherein the heat buffer includes a vertical tank, and wherein the vertical tank includes: a fluid inlet disposed at a top end of the vertical tank and connected to an outlet of the heat source; at least one heat transfer fluid take-off outlet disposed at a bottom end of the vertical tank and connected to an inlet of the heat source; and at least one fluid outlet connected to an inlet of a respective heat unit.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0020] FIG. 1 schematically shows a first embodiment of the system according to the invention.

[0021] FIG. 2 schematically shows a second embodiment of the system according to the invention.

DETAILED DESCRIPTION

[0022] An exemplary embodiment of a system S1, S2 which is part of a greenhouse for growing plants of the present invention is described with reference to FIGS. 1 and 2.

[0023] The system S1 includes tubes, or piping, 1 represented by lines. The system S1 also contains a solar collector 2 that makes use of optical mirrors (not shown) to concentrate incident solar rays on a fluid line, and as such, to heat the fluid in the fluid line of the solar collector. The solar collector 2 is part of a fluid loop which includes the tubes 1, valves 3, a thermal desalination unit 4, a salt production unit 5, a heat exchanger 6 for a greenhouse air space heating 7 and an electrical pump 8. Arranged parallel to the line with the solar collector 2 and the pump 8 is a line with a heat buffer tank 9 and a pump 10. Line 11 is a bypass line for the thermal desalination unit 4. Line 12, between the buffer tank 9 and the salt production unit 5, connect the buffer tank 9 with the salt production unit 5 and the heat exchanger 6. The heat exchanger 6 is part of a second fluid loop 13, which loop 13 serves as a thermal connection between the heat exchanger 6 and the space heating 7 of the greenhouse.

[0024] The salt production unit 5 may be a multi stage flash unit, with an operating temperature between 70 and 110 degrees Centigrade. Alternatively, it may be a high performance salt production device with plastic heat exchangers that may have a slightly lower operating temperature, or it may be an open salt pond which may have an even lower operating temperature, where water evaporates from brine, and salt remains.

[0025] The buffer tank 9 is a vertical tank, of which a fluid inlet 14 is located at its top end and connected to the heat source outlet 15. A fluid outlet 16 of the buffer tank 9 is located at its bottom end and connected to the heat source inlet 17. The vertical buffer tank 9 has one fluid outlet 18 at its top end, connected via pump 10 to the thermal desalination unit 4, and has four fluid outlets 19 connected to inlets 20 and 21 of the salt production unit 5 and the heat exchanger 6, respectively. Each of the fluid outlets 19 is located at a different height between the top and bottom ends of the buffer tank 9, allowing for different take-off temperatures at the different fluid outlets 19 when a vertical temperature gradient is present within the buffer tank 9.

[0026] In the method according to an example embodiment of the present invention of system S1, a heat transfer fluid, such as glycol, is circulated through the heat users, in a serial arrangement, i.e., one after the other, i.e. through the thermal desalination unit 4, the salt production unit 5, and the heat exchanger 6 of the greenhouse air space heating 7.

[0027] The fluid is heated in the solar collector 2, to a temperature of up to 400 degrees Centigrade, then, in normal operation mode, passes through the heat exchanger of the thermal desalination unit 4, giving heat to that unit.

[0028] The fluid leaves the heat exchanger at around 70-110 degrees Centigrade, and enters the salt production unit 5, cools down further and continues to the heat exchanger 6 at a temperature between 50-90 degrees Centigrade. It returns to the solar collector 2 at a temperature between 20-70 degrees Centigrade, where it starts a new cycle through the fluid circuit.

[0029] It is possible to change the described normal operation mode to other operation modes, by, e.g., closing and opening valves 3 and activating or stopping pumps 8 and 10.

[0030] Via tubes 1 and pump 10 heat transfer fluid may be tapped from the buffer tank 9 and may be fed to the thermal desalination unit 4. This may be useful when the solar collector 2 may not be providing enough heat and/or provides heat at inadequate temperatures for the thermal desalination unit 4 to operate or to operate optimally, for instance, during nighttime conditions.

[0031] Via tubes 12 the buffer tank 9 may be tapped at different heights, and the tapped fluid may be mixed with the fluid from the solar collector 2 entering either the salt production unit 5 or the heat exchanger 6. This may temporarily lead to some loss of energy, but may make it possible to operate these two heat users within their allowed temperature ranges, and thus, to operate the whole system Si, without having the need for a backup system. Moreover, adding fluid from the buffer tank 9, may allow for driving the heat users at their optimal temperature ranges, with respect to life expectancy and/or energy efficiency, thereby saving either investment costs or energy costs, or both.

[0032] A bypass tube 11 allows for bypassing of the thermal desalination unit 4, for instance when the thermal desalination unit 4 may be subject to maintenance operations.

[0033] FIG. 2, shows the system S2, which is similar to the system S1 of FIG. 1 but has an additional heat user, in the form of a turbine 25 of an organic rankine cycle. The heat exchanger of the thermal desalination unit 4 serves as the condenser of the organic rankine cycle; thus, the cycle is integrated in the fluid circuit of system S2. The turbine 25 is mechanically coupled to a generator 26 of electricity.

[0034] Salt production unit 5 is a high-performance salt production device with plastic heat exchangers, operating at lower temperatures than the multistage flash unit 5 of FIG. 1.

[0035] Pump 10 of system S1 is replaced by pump 27 integrated in tubes 12 connecting the buffer tank 9 to an inlet 20, 21, 28, 29 of each of the heat users.

[0036] In the method according to an example embodiment of the present invention of system S2, a heat transfer fluid, e.g., an organic fluid with a high molecular mass and a boiling point below that of water in the atmosphere, is circulated through the heat users, i.e. through the organic rankine cycle turbine 25, thermal desalination unit 4, the salt production unit 5, and the heat exchanger 6 of the greenhouse air space heating 7. The fluid is heated and evaporated in the solar collector 2, to a temperature up to 400 degrees Centigrade, then, in normal operation mode, passes through the turbine 25 of the organic rankine cycle, where it may lose energy, in terms of both pressure and heat, while driving the generator 26 and thereby producing electricity for the greenhouse climate control equipment (fans, pumps, etc.) and other electrical equipment. Next, the fluid enters at a temperature between 90-130 degrees Centigrade, a heat exchanger of the thermal desalination unit 4 and condenses while giving heat to the desalination unit 4. The fluid leaves the heat exchanger between 70-110 degrees Centigrade, and enters the salt production unit 5, cools down further and continues to the heat exchanger 6 at a temperature between 50-90 degrees Centigrade. It returns to the solar collector 2 at a temperature between approximately 20-70 degrees Centigrade, where it starts a new cycle through the fluid circuit.

[0037] It is possible to change the described normal operation mode to other operation modes, by, e.g., closing and opening valves 3 and activating or stopping pumps 8 and 27.

[0038] Via tubes 12 the buffer tank 9 may be tapped at different heights, and the tapped fluid may be mixed with the fluid from the solar collector 2 entering any of the heat users. The reasons for doing so are described above with respect to system S1.

[0039] Not shown in FIG. 2, are bypass tubes in each of the heat users. These bypass tubes may allow the system S2 to operate when one of the heat users may temporarily not be used, e.g. because there may be no heat demand or during maintenance activities. Alternatively, the tubes 12 may be used as bypass tubes.

[0040] Also not shown in FIGS. 1 and 2, is an additional heat source, operating on fossil fuel and arranged in parallel and or series to the solar collector 2. This additional heat source provides heat at moments when the demand is higher than the solar collector 2 is capable of supplying.

[0041] The described and shown embodiments of the invention serve for illustration of the invention. Variations on these embodiments are possible. For example, a buffer container may be interposed between two heat users, instead of between the outlet and inlet of the heat source. Also, a heat user may be composed of a heat exchanger with an attached second fluid circuit as a closed loop that comprises two or more heat users, for example, in order to be able to apply different fluid pressures in each of the fluid loops. This is in particular useful for keeping the organic rankine cycle in FIG. 2 as a separate loop, fed by a heat exchanger through which the heat transfer fluid from the solar collector 2 flows.