Embodiments of the invention relate energy systems based on a geothermal heat sources.
Thermodynamic cycles such as the Rankin cycle or a derivative thereof such as the Organic Rankin cycle (ORC) use heat or thermal energy to heat a working fluid that can then be used to perform work, e.g. driving a turbine to produce electricity.
The heat to drive the aforesaid thermodynamic cycles may be obtained from a geothermal heat/energy source where it is extracted from a hot geo-fluid that percolates from the earth.
Geothermal heat sources vary in grade from high to low. High grade geothermal heat sources are characterized in they have high temperature geo-fluids (>100° C.) with high flow rates (>2000 liters/minute). Low grade geothermal heat sources have low temperature geo-fluids (<100° C.) with flow rates <1000 liters/minute.
Low grade geothermal heat sources may be not be suitable to provide the heat to drive thermodynamic cycles.
Generally, embodiments of the present invention disclose a method and apparatus to utilize a low grade geothermal heat source to supply heat to a first thermodynamic cycle. The method may comprise boosting or supplementing the heat being supplied to the first thermodynamic cycle by feeding waste heat from a second thermodynamic cycle into the first thermodynamic cycle. The second thermodynamic cycle may be driven by heat derived through combustion of a fuel. Advantageously, the second thermodynamic cycle may be operated to service a location e.g., a hotel, by providing heating and/or cooling at the location.
Specifically, in one aspect the invention provides a method for using heat to perform work, comprising: operating a first thermodynamic cycle wherein heat for a first working is provided by combustion of a fuel-based (FB) energy source; operating a second thermodynamic cycle wherein heat for a second working fluid is from a combination of a non-fuel-based (NFB) energy source and waste heat from the first thermodynamic cycle.
Specifically, in another aspect, the invention provides a method for using heat to perform work, comprising: modifying an existing installation that operates a first thermodynamic cycle so that waste heat from said thermodynamic cycle can be fed into a second thermodynamic cycle, wherein said first thermodynamic cycle relies on combustion of an fuel-based (FB) energy source to heat a first working fluid; and constructing a new installation to operate the second thermodynamic cycle wherein a second working fluid is heated by a combination of a non-fuel-based (NFB) energy source and the waste heat from the first thermodynamic cycle.
Specifically, in yet another aspect, the invention provides apparatus to convert heat into energy, comprising: a first sub-system to operate a first thermodynamic cycle to harness heat derived through combustion of a fuel-based (FB) energy source; and a second sub-system to operate a second thermodynamic cycle to harness heat derived from a combination of a non-fuel-based (NFB) energy source and waste heat from the first sub-system.
Other aspects of the invention will be apparent from the written description below.
In the following description, for purposes of explanation, numerous specific details are set forth in order to provide a thorough understanding of the invention. It will be apparent, however, to one skilled in the art that the invention can be practiced without these specific details.
Reference in this specification to “one embodiment” or “an embodiment” means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment of the invention. The appearances of the phrase “in one embodiment” in various places in the specification are not necessarily all referring to the same embodiment, nor are separate or alternative embodiments mutually exclusive of other embodiments. Moreover, various features are described which may be exhibited by some embodiments and not by others. Similarly, various requirements are described which may be requirements for some embodiments but not other embodiments.
The present invention discloses, in one embodiment, a system for the conversion of heat into usable energy in the form of electricity, in the form of a heating medium (a fluid including but not limited to water), and in the form of a coolant medium (another fluid including but not limited to water). The electricity may be used to drive electrical appliances such as is found in a residence, a commercial entity, or a factory. The heating medium may be used to provide space heating and hot water to a facility. The coolant medium may be used to supply a cooling supply to air conditioning units in the same settings.
Referring to
Heat exchanger 108 extracts some portion 110, of waste heat 106, and transfers it to distributor 112 and absorption chiller 118 via heat flows 110 and 116. This heat transfer can occur via one or more mechanisms such as the flow of a fluid medium, or via a heat pipe in a fashion which was disclosed in patent application Ser. No. 12/396,336 which is herein incorporated by reference. Distributor 112 provides some useful heat output via a heating medium circulation loop 114, for use in facilities which may require space heating or for some other purpose. Circulation loop 114 could include a network of pipes or heat pipes which carry liquids (such as water) or vapors (such as steam) to carry the heat to areas where it is needed.
Absorption chiller 118 (or some other mechanism for converting heat into cooling capacity) provides some useful cooling capacity via coolant medium circulation loop 120. Circulation 120 loop could include a network of pipes or heat pipes which carry liquids (such as water) or vapors (such as steam) to extract heat from areas where it is appropriate. In general all heat flows, heat transfers, or circulation loops within and outside the system described in this application can be accomplished using conventional piping networks or networks of heat pipes depending on the application in a manner described in patent application Ser. No. 12/396,336.
Referring to
Methods for extracting this heat are described in patent application Ser. No. 12/396,336. A portion of the heat delivered to heat exchanger 204, heat flow 206, is used to drive ORC engine 208. Rotational shaft power developed by ORC engine 208 is used to drive generator 210 to produce electricity. Another portion of the heat from heat exchanger 204 is extracted in the form of heat flow 212. This heat is delivered to distributor 214, and chiller 220, which serve the same function as distributor 112, and chiller 118 in
Referring now to
Heat exchanger 308 extracts a portion of heat flow 306 and transfers it via heat flow 326 to heat exchanger 328. Heat flow 326 may be accomplished via circulating fluid medium or heat pipe. Heat exchanger 328 serves to combine heat flow 326, with heat derived from geothermal heat source 330. Other heat sources may be combined but are not shown here for purposes of simplification. The combined heat flow 332, is transferred to ORC engine 334 which produces shaft power used to drive generator 336, producing electricity. Heat exchanger 308 may also supply heat to thermal storage unit 338 under circumstances when all available heat is not required.
Referring again to
Booster burner 344 is shown providing supplementary heat flow 342 to heat exchanger 308. Prime mover 302, if is in the form of a turbine, is generally constrained to operate at one speed with a constant fuel consumption rate in order to maintain optimum efficiency. In circumstances where additional fuel based heat is required to optimize the overall system performance then booster burner 344 may be engaged to supply varying amounts of additional heat to supply this need.
Referring now to
Referring again to
Control unit, 424, is connected to sensor/control network 440. The network as portrayed does not reveal all possible connections to system energy conversion system components for simplicity. This network allows the control unit to monitor all parameters of the energy conversion system including but not limited too, component temperatures, turbine speeds, working fluid flow rates, and electrical output. This network also allows for control signals originating from the control system to be directed to various components including but not limited to pumps, turbines, flow control valves, generators, and grid interface electronics. All of these parameters are used as inputs by a control program which resides on control system 424. Control system 424 may be a microprocessor based computer or equivalent hardware allowing for complicated computing and control programs to be run. The control software uses the sensor inputs to keep the energy conversion system running within preset operational regions, and is capable of responding to changes, by sending appropriate control signals, in the needs of whatever facility is using the combined energy outputs. The control software can manage a number of sophisticated tasks including optimizing overall system efficiency, optimizing the efficiency of particular outputs (heating, electricity, cooling). It can also be connected to an external network (i.e. internet, satellite, or cellular networks) so that it's operation may be remotely monitored and controlled.
Referring now to
In general, this system provides several advantages over converting energy from a single heat source. In one case a geothermal heat source with a temperature of 65° C. has useful energy which may be extracted, but not by using HFC134a as a working fluid because the characteristics of this fluid make it difficult to extract energy at temperatures below approximately 70° C. While it may be possible to raise the temperature of the geothermal heat source by drilling deeper into the reservoir, the expense of this drilling usually outweighs the benefits, thus the geothermal heat source has a fixed set of characteristics which must be accommodated. With the system described herein, it is possible to combine heat flows. Thus, if the geothermal heat sources are above a new lower threshold, at least approximately 30° C., a single heat flow with sufficient temperature can thus be consolidated. This heat flow contains energy from both the geothermal heat source, and the combustible fuel. A fuel based heat source can be controlled, in a simple fashion, by adjusting the rate of combustion and/or the overall characteristics of the combustion portion of the energy conversion system. In this fashion the combustion heat source may be easily modified to permit economic extraction of the geothermal energy. The same ability to enhance a low temperature source applies to solar thermal sources as well which supply temperatures which vary according to the weather and time of day. The threshold at which these sources can provide useful energy is lowered, and therefore overall energy utilization is enhanced.
The same mechanisms apply if the flow rate of the geothermal heat source is too low. Even if the temperature is sufficiently high, say 85° C., the required flow rate may be beyond the reservoir's potential, or the expense of increasing it too costly. Again, by consolidating multiple heat sources into one, the energy of the geothermal resource may be exploited to some extent without the need for modifications. Depending on prevailing weather patterns, a viable installation may result from the combination of a geothermal source and a solar thermal source without utilizing combustion to supply additional heat.
The ability to bring together more than two heat sources, for example solar, fuel, biomass, geothermal and others simplifies the issue of variations in the availability of each of the sources. These variations may occur for a number of reasons such as cloud cover (which impacts the incident solar flux), fuel prices, or external temperatures which impact the efficiency of heat rejection. Alternatively, the facility which consumes the combined utility may have different demands during the day, at night, and during the year for electricity, heating, and cooling. The system can dynamically adapt to all of these variations and maintain the delivery of the desired electricity, heating, and cooling supply if it designed and operated properly.
The overall efficiency of energy conversion is greater because the consolidated energy sources are delivered in the form of electricity, heating, and cooling, potentially realizing >60% conversion in some cases. Additionally, overall CO2 emissions are lowered as a greater portion of the consolidated heat source may be extracted from renewable sources depending on the nature of the site on which the system is located.
Frequently, in cases where a geothermal heat source is being exploited for other purposes (recreational bathing for example), the facility which exploits the geothermal heat source (a hotel for example) incorporates infrastructure for the combustion of fuels to provide heating. Often the facility may also have the capability to support infrastructure for the collection of heat from solar radiation. Advantageously, in accordance with embodiments or the present invention, the heat from combustion and/or solar sources may be uses to supplement the heat from the geothermal heat source can to provide opportunities for enhanced energy extraction, utilization, and conversion from multiple heat sources.
In some cases, the geo-fluid from a geothermal heat source emerges with sufficient temperature such that some portion of the geo-fluid emerges as steam, the steam may be used directly to drive a turbine for the purpose of generating electricity. The portion of the geo-fluid which emerges in liquid form is re-injected into the ground along with the condensed steam. In circumstances such as these, it may be advantageous to consolidate the waste heat from this process (liquid portion of the geo-fluid and the steam before it is condensed) with other heat sources. In this fashion additional power (electricity, heating, and cooling) may be derived with higher overall efficiency.
Number | Date | Country | |
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Parent | 12495858 | Jul 2009 | US |
Child | 15927041 | US |