Patent Application
20130291857
Solar power systems, or plants, are known and used for capturing solar energy and generating electricity. The system typically includes one or more solar collectors that direct solar energy into a heat-absorbing fluid, such as a synthetic oil. The heated fluid is used in a thermodynamic cycle to produce steam that drives a turbine to generate electricity. In some systems, a molten salt absorbs and stores heat from the heat-absorbing fluid via a heat exchanger.
A heat exchanger according to an exemplary aspect of the present disclosure includes, among other things, at least one heat pipe having a first end and a second end. The heat exchanger further includes a first housing including a first plenum, the first end of the at least one heat pipe within the first plenum. Also included is a second housing including a second plenum. The second end of the at least one heat pipe is within the second plenum, and the second housing is spaced from the first housing to provide a double-layer boundary between the first plenum and the second plenum.
In a further non-limiting embodiment of the foregoing heat exchanger, the first plenum is in communication with a first fluid, and the second plenum is in communication with a second fluid different from the first fluid.
In a further non-limiting embodiment of the foregoing heat exchanger, the first and second fluids are reactive when brought together.
In a further non-limiting embodiment of the foregoing heat exchanger, the first fluid is oil and the second fluid is a molten salt.
In a further non-limiting embodiment of the foregoing heat exchanger, the at least one heat pipe has a working fluid contained therein.
In a further non-limiting embodiment of the foregoing heat exchanger, the working fluid is non-reactive with oil and molten salt.
In a further non-limiting embodiment of the foregoing heat exchanger, the heat pipe has a longitudinal axis, and the first and second housings are spaced apart along the longitudinal axis of the heat pipe.
In a further non-limiting embodiment of the foregoing heat exchanger, the first and second ends are closed ends.
A solar power system according to an exemplary aspect of the present disclosure includes, among other things, a concentrated solar receiver, an oil circuit, a molten salt circuit, and at least one heat exchanger in communication with both the oil circuit and the molten salt circuit. The at least one heat exchanger includes a first housing including a first plenum in communication with the oil circuit, and a second housing including a second plenum in communication with the molten salt circuit. The first housing is spaced from the second housing to provide a double-layer boundary between the first plenum and the second plenum.
In a further non-limiting embodiment of the foregoing solar power system, the at least one heat exchanger includes at least one heat pipe having a first end within the first plenum and a second end within the second plenum, and the first and second ends are closed ends.
In a further non-limiting embodiment of the foregoing solar power system, the second housing is a molten salt storage tank.
In a further non-limiting embodiment of the foregoing solar power system, the molten salt circuit includes a first and second molten salt storage tanks.
In a further non-limiting embodiment of the foregoing solar power system, the second housing is separate from the first and second molten salt storage tanks, and is separate from the first housing.
In a further non-limiting embodiment of the foregoing solar power system, the oil and molten salt circuits each include a plurality of pipes and valves, and the valves are selectively adjustable to configure the oil and molten salt circuits for thermal energy charging and discharging conditions.
In a further non-limiting embodiment of the foregoing solar power system, the system further includes a controller, and the valves adjustable in response to the controller.
In a further non-limiting embodiment of the foregoing solar power system, the at least one heat exchanger includes two heat exchangers, and the valves are adjustable to direct the oil and molten salt circuits to a particular one of the two heat exchangers based on whether the solar power system is in a thermal energy charging or discharging condition.
A method of leak detection according to another exemplary aspect of the present disclosure includes, among other things, providing a solar power system including a concentrated solar receiver, an oil circuit, and a molten salt circuits. The method further includes establishing a flow of oil within the oil circuit, and establishing a flow of molten salt within the molten salt circuit. At least one heat exchanger is provided in communication with both the oil and molten salt circuits, and the at least one heat exchanger providing a double-layer boundary between the oil and molten salt. The at least one heat exchanger is monitored for a potential compromise in the double-layer boundary.
In a further non-limiting embodiment of the foregoing method of leak detection, the at least one heat exchanger includes two spaced-apart housings and at least one heat pipe.
In a further non-limiting embodiment of the foregoing method of leak detection, the method further includes providing at least one of the two spaced-apart housings and the heat pipe with a sensor.
In a further non-limiting embodiment of the foregoing method of leak detection, the monitoring step includes comparing, with a controller, a signal from the sensor with a predetermined threshold.
These and other features of the present disclosure can be best understood from the following drawings and detailed description.
The drawings can be briefly described as follows:
The example system 10 includes an oil circuit 12 and a molten, or solar, salt circuit 14. The oil circuit 12 includes pipes 16 and valves 18a-e, which are selectively adjustable to direct oil flow in a particular manner. The oil circuit 12 is further in communication with concentrated solar receiver S, which in this example includes parabolic troughs 20 and a collector pipe 22. A thermodynamic cycle including a steam generator 24, turbine 26 and a generator 28 is located downstream of the troughs 20. The oil circuit 12 includes a pump P.
The molten salt circuit 14 includes a plurality of pipes 32 and valves 34a-d. Like the valves 18a-e, the valves 34a-d are selectively adjustable to route molten salt between heat exchangers 30, 36, and first and second molten salt storage tanks 38, 40, respectively, as desired. In the illustrated example, the system 10 is arranged such that the first molten salt storage tank 38 receives and selectively stores hot molten salt, while the second molten salt storage tank 40 receives and selectively stores cold molten salt.
The valves 18a-e and 34a-d are selectively adjustable in response to a controller C to operate the system in different modes (or, conditions), as will be described below. In other examples, however, the valves 18a-e and 34a-d could be manually adjustable.
In this example, the oil circuit 12 includes five valves 18a-e. A first valve 18a is upstream of the concentrated solar receiver S, and allows selective bypass of the concentrated solar receiver S. A second valve 18b is positioned downstream of the concentrated solar receiver to selectively tap heated oil that would otherwise be directed to the steam generator 24. A third valve 18c is downstream of the steam generator to selectively direct relatively cold oil to a heat exchanger or the concentrated solar receiver S. Another valve 18d is adjustable to direct oil to one of heat exchangers 30, 36. A fifth valve, 18e, is selectively opened to prevent flow to the steam generator 24.
The molten salt circuit 14 includes valves 34a, 34c adjustable to allow entry of molten salt into the molten salt storage tanks 38, 40, respectively. Similarly, valves 34b, 34d are adjustable to release molten salt from the tanks 38, 40, respectively.
Via valve 34d, the molten salt circuit 14 directs cold molten from the cold molten salt storage tank 40 to the heat exchanger 30 to absorb heat from the hot oil. The heated molted salt is then stored in the hot molten salt storage tank 38, by way of valve 34a, for later use. While the steam generator 24 is operating in
In conditions where sunlight is inadequate or unavailable, as examples, the hot molten salt from storage tank 38 can be discharged in another mode of operation of the system 10 to transfer heat to the oil circuit 12. As illustrated in
While illustrated, valves 34b and 34d do not need to be included. For instance, flow through these valves could be regulated by operation of the pumps alone, while flow would generally be prevented by either gravity, shutting off the associated pumps, or a combination of the two.
The first and second plenums 48, 50 are in communication with the molten salt circuits 14 and the oil circuit 12, respectively. During a thermal energy charging condition, such as that illustrated in
Relatively cold molten salt enters the plenum 48 via the pipes 32, absorbs heat from the heat pipe 42, and then is directed toward the hot molten salt storage tank 38. The relatively cold oil is returned to the oil circuit 12, where it is re-heated. Then, the working fluid F condenses and moves toward the opposite end 46 of the pipe.
Because oil is a fuel, and molten salt is an oxidizer, the two may be reactive when brought together. Accordingly, the heat exchanger 30 includes two double-layer boundaries between the oil and the molten salt. A first of these double-layer boundaries is provided by a space 58 between the housings 52, 54. In this example, the space 58 is an axial space, relative to the longitudinal axis A of the heat pipe 42. A second double-layer boundary is provided by the closed ends 44, 46 of the heat pipe 42, as well as the arrangement of those ends 44, 46 within separate housings 52, 54.
Should one end 44, 46 of the heat pipe 42 be compromised, the other end of the heat pipe 42 would prevent mixing of the molten salt and oil. Likewise, should one of the housings 52, 54 be compromised, the other housing would prevent mixing between the molten salt and oil.
This arrangement of the heat pipe 42 between the spaced-apart housings 52, 54, provides the heat exchanger 30 with double-layer boundaries that effectively permit heat transfer between the molten salt and the oil.
Further, a leak detection system L (e.g., visual inspection, temperature sensors, pressure sensors, liquid detection, alarm circuits, etc) could be incorporated into the heat pipe 42, and/or the housings 52, 54 to detect a breach of the above-described double-layer boundaries. For example, these leak detection systems permit leak detection before compromise of the second layer of the double-layer boundaries occurs.
An example leak detection system L is shown in
While only one heat pipe 42 is shown in
While the housings 52, 54 of
Although the different examples have the specific components shown in the illustrations, embodiments of this invention are not limited to those particular combinations. It is possible to use some of the components or features from one of the examples in combination with features or components from another one of the examples.
One of ordinary skill in this art would understand that the above-described embodiments are exemplary and non-limiting. That is, modifications of this disclosure would come within the scope of the claims. Accordingly, the following claims should be studied to determine their true scope and content.
