System, device, and method for generating energy using a thermoelectric generator

A system, a thermoelectric generator, and a method for generating electricity are provided. The system includes a thermoelectric generator, a cooling system, and a heating system. The cooling system includes a cold side module configured to hold a predetermined volume of air, a subterranean heat exchanger including an underground conduit, the underground conduit having a first end configured to receive ambient air and a second end coupled to the inlet of the cold side module, and an air exhaust coupled to the outlet of the cold side module and having one or more valves configured to control an airflow from the subterranean heat exchanger towards the air exhaust. The heating system includes a first solar concentrator to collect light rays, a hot side module, and a fiber optic cable to transport the collected light rays to the hot side module.

BACKGROUND

Field of the Invention

This invention generally relates to a thermoelectric generator system. In particular, the invention provides a thermoelectric generator system based on renewable energy.

Background of the Invention

With ever increasing dependence on fossil fuels, interest in renewable energy generation is increasing. Solar energy is harnessed using a plethora of technologies such as photovoltaic cells, solar thermal heating through parabolic reflectors or concentrators, solar architecture, and artificial photosynthesis. Solar energy is one of the promising techniques of renewable energy generation and it is mainly divided into active and passive techniques depending on the means of capturing and distribing this energy. Active solar energy techniques include semiconductor or organic photovoltaic technologies and solar concentrators. Passive solar techniques include solar architecture (building orientation towards the sun), material selection that have adequate thermal mass or light dispersing properties.

A thermoelectric generator (TEG) is a device that converts thermal energy into electrical energy based on the Seebeck effect and the Peltier effect. The Seebeck effect or principle states that if two wires of different materials are joined at their ends, forming two junctions, and one junction is held at a higher temperature than the other junction, a voltage difference arises between the two junctions. The TEGs have many advantages such as no moving mechanical parts, long lifetime, quiet operation, and environmentally friendliness.

However, it has always been a challenging task to create a heat flux between the two sides of the TEG. Accordingly, what is needed, as recognized by the present inventor, is a method and system that creates the heat flux using renewable energy.

The foregoing “Background” description is for the purpose of generally presenting the context of the disclosure. Work of the inventor, to the extent it is described in this background section, as well as aspects of the description which may not otherwise qualify as prior art at the time of filing, are neither expressly or impliedly admitted as prior art against the present invention.

Accordingly it is one object of the present disclosure to provide a thermoelectric generating system that creates a heat flux for the thermoelectric generator using renewable energy.

SUMMARY

The present disclosure relates to a system for generating electricity. The system includes a thermoelectric generator, a cooling system, and a heating system. The cooling system includes a cold side module configured to hold a predetermined volume of air, a subterranean heat exchanger including an underground conduit, the underground conduit having a first end configured to receive ambient air and a second end coupled to the inlet of the cold side module, and an air exhaust coupled to the outlet of the cold side module and having one or more valves configured to control an airflow from the subterranean heat exchanger towards the air exhaust. The heating system includes a first solar concentrator to collect light rays, a hot side module, and a fiber optic cable to transport the collected light rays to the hot side module.

The present disclosure also relates to a method for generating electricity. The method includes heating a hot side of a thermoelectric generator via concentrated light rays collected using a solar concentrator and transported via a fiber optic cable; cooling a cold side of the thermoelectric generator via a cooling system; and connecting an output of the thermoelectric generator to a transformer to provide AC current. The cooling system includes a cold side module configured to hold a predetermined volume of air, the cold side module having an inlet and an outlet, a subterranean heat exchanger including an underground conduit, the underground conduit having a first end configured to receive ambient air and a second end coupled to the inlet of the cold side module, and an air exhaust coupled to the outlet of the cold side module and having one or more valves configured to control an airflow from the subterranean heat exchanger towards the air exhaust.

DETAILED DESCRIPTION

Referring now to the drawings, wherein like reference numerals designate identical or corresponding parts throughout several views, the following description relates to a system and associated methodology for electrical energy generation via a thermoelectric generator (TEG).

The renewable electricity generation system described herein uses renewable resources to provide a temperature difference to the thermoelectric generator. For example, the system uses natural convection and solar thermal energy collected via fiber optics bundles.

FIG. 1is a schematic that shows a system100for generating power using a thermoelectric generator102(i.e., a Seebeck generator) according to one example. The TEG102is a solid state device that converts heat flux (i.e., temperature differences) directly into electrical energy through a phenomenon called the Seebeck effect (a form of thermoelectric effect). The generated electrical energy is proportional to the temperature differences.

The thermoelectric generator102includes a first thermoelectric layer and a second thermoelectric layer. The first thermoelectric layer is disposed adjacent to the second thermoelectric layer in a substantially parallel spatial relationship. The thermoelectric generator102generates electrical energy as a function of a temperature difference between the first thermoelectric layer and the second thermoelectric layer based on the Seebeck effect as described previously herein (also referred to herein as the cold side and hot side of the TEG102).

The system100creates a temperature differential across the TEG102via a cooling system104and a heating system106(e.g., heat exchangers). The cooling system104and the heating system106supply cooling and heating to the cold side and hot side of the TEG102, respectively. The cooling system104is operatively connected to the cold side of the thermoelectric generator (e.g., the first thermoelectric layer) to cool the cold side. The cold side of the TEG102is maintained at a constant temperature in the range of 5 to 10° C. In one implementation, the temperature is maintained using cool air cooled via a subterranean air cooling module as shown and described inFIG. 2. The cooling system104may be coupled to multiple TEGs102. The heating system106may also be coupled to the multiple TEGs102. The TEG102may be an array of one or more TEGs102arranged in a single layer between the cooling system104and the heating system106. The one or more TEGs102may be connected as a group to provide a specified voltage and/or current.

FIG. 2is a schematic that shows the cooling system104according to one example. The cooling system104includes a subterranean air cooling module202, a cold side module204, and a first air exhaust206. Air at ambient temperature is input to the subterranean air cooling module202. The air passes through the subterranean air cooling module202and reaches a predetermined temperature (e.g., temperature between 5 to 10° C.). The higher temperature at the first air exhaust206creates a natural air flow towards the cold side module204.

The cold side module204is disposed adjacent to the first thermoelectric layer (cold side of the TEG102) and hold a predetermined volume of air. The cold side module204maintains the first thermoelectric layer at a cold temperature with respect to the second thermoelectric layer via the flow of cold air from the subterranean cooling module202towards the first air exhaust206. The cold side module204includes at least one inlet and one outlet. The inlet is coupled to the subterranean air cooling module via a conduit. The conduit is insulated to minimize heat exchange with ambient air. The cold side module204may be coupled to multiple subterranean air cooling modules.

The first air exhaust206includes an inlet and an outlet. The inlet is coupled to the outlet of the cold side module204via a conduit. The outlet includes one or more valves to control the output of the air. The first air exhaust206may be an air tank that holds a predetermined volume of air. The first air exhaust206may be heated via light rays or via ambient air to maintain a hotter temperature with respect to the air in the cold side module204. The first air exhaust may also include a fan to withdraw air from the cold side module204. Alternatively, the fan may be disposed on a side of the cold side module204to withdraw the air.

The cold side module204has a rectangular shape. At least one side of the cold side module204is in a direct contact with the cold side of the TEG102. In one implementation, the at least one side of the cold side module204has a size and a shape that match the size and the shape of the cold side of the TEG102.

In one implementation, multiple TEGs102are disposed in direct contact with the at least one side of the cold side module204to cover the complete surface of the at least one side of the cold side module204. The cold side module204may include insulating materials to minimize heat exchange with the ambient air. For example, one or more layers of insulating materials may be disposed on the side of the cold side module non-adjacent to the first thermoelectric layer (or cold side). In one example, insulating materials are disposed on inside or outside surfaces of the cold side module204that are not in direct contact with the cold side of the TEG102. Insulating materials may also be disposed on the hot side of the TEG102. Insulating materials may include non-electrically conductive materials that withstand high temperatures. High-temperature examples of insulation include ceramics in both solid and fabric form, as well as other inorganic thermal insulators. Additionally, for lower-temperature operations, various polymers can be used. Suitable examples of such polymers include neoprene and/or silicone rubber. The cold side module204may be of size and shape corresponding to the size and shape of the cold side of the thermoelectric generator102as described previously herein.

The subterranean air cooling module202may include a conduit disposed underground and coupled to the cold side module204. The subterranean air cooling module202may include a fan to induce air to the conduit. The fan may be coupled to a first end (or inlet) of the conduit. As air moves through the underground conduit the earth or ground acts as a heat exchanger to cool the air passing through the conduit. The cooled air is directed from the underground conduit into the cold side module204so to cool the cold side of the TEG102. The underground conduit has a shape/size to maximize heat transfer with the soil or geological formation. For example, the underground conduit includes multiple fins on an outer surface of the underground conduit to enhance heat exchange with the soil. An insulation layer may be disposed on outer surfaces of the conduit that are above ground level. Insulation layers may be around the entire length of the underground conduit. The layers may include a moisture retaining layer (e.g., a layer of sand disposed in between two other insulation materials). The moisture retaining layer helps increase the efficiency of heat exchange with the underground conduit. The layers type and thickness are selected based on the characteristics of the ground at the location of the system100.

In one implementation, the subterranean air cooling module includes202a metal pipe located 5 to 5 feet beneath the ground where the temperature is approximately constant at 5 to 10° C. (constant temperature depth zone). The location of the metal pipe beneath the ground may be based on the characteristics of the ground at the location of the system100(i.e., based on the type of soil). Further, the length and shape of the metal pipe may be based on the characteristics of the ground and desired temperature of air.

The underground conduit may include multiple sections of different diameters. For example, a first section of the underground conduit includes a vertical stretch from the inlet to a predetermined depth associated with the constant temperature depth zone. A second section includes a horizontal stretch at the predetermined depth. A third section includes a vertical stretch from the predetermined depth to the inlet of the cold side module204. The first section and the third section may be substantially straight stretches. The second section may have a serpentine shape (in the horizontal plane). An end of the first section is coupled to a first end of the second section via a first elbow. A second end of the second section is coupled to an end of the third section via a second elbow.

In one implementation, the second section includes two or more parallel stretches. The stretches are coupled together at the first elbow and the second elbow. A diameter of the conduit at the second section may be larger than the diameter of conduit in the first section. The diameter of the conduit in the third section is equal to the diameter of the conduit in the first section. The first elbow and the second elbow are 90 degree elbows. A first end of the first elbow has a diameter corresponding to the diameter of the conduit in the first section and a second of the first elbow has a diameter corresponding to the diameter of the conduit in the second section. The change in diameter provides greater control on the flow of air in the subterranean air cooling module202.

FIG. 3is a schematic that shows the heating system106according to one example. The heating system106includes a heat generator306, a second air exhaust302, and a hot side module304. The heat generator306may include a solar thermal concentrator or a black body system to concentrate solar radiation to generate heat for the hot side of the TEG102as discussed further below. The hot side module304maintains the second thermoelectric layer at a higher temperature relative to the first thermoelectric layer. The hot side module304may include insulating materials disposed on the side non-adjacent to the second thermoelectric layer to minimize the loss of heat due to the ambient temperature (e.g., heat exchange with the ambient air). In one example, the hot side module304may be in a direct contact with the hot side of the TEG102. In another example, a material may be deposited between the hot side module304and the hot side of the TEG102such as a heat retaining material.

The heat generator306may include one or more fans to circulate the heated air towards the hot side module304. In one implementation, natural convection heat transfer mechanism is used to transfer heat using air flow.

Air and/or fiber optics bundles (FOB) are used to carry heat or concentrated solar light rays to the hot side of the TEG102. The temperature of the generated heat depends on weather conditions, time of the year, time of the day, and the like. The hot side module304includes insulating materials and heat retaining materials as discussed previously herein. The hot side module304may be of a size and shape corresponding to the hot side of the TEG102. The heat generator306may provide heat to multiple TEGs102.

FIG. 4is a schematic that shows the heat generator306according to one example. The heat generator306includes a solar concentrator402and an optical fiber bundle404. The solar concentrator402may include one or more optical elements (e.g., lenses, mirrors) configured to focus incident light rays from the sun to an entry of an optical fiber and/or a bundle of optical fibers. The optical fiber bundle404carries the concentrated light to the hot side module304. The fiber optics may be composed of plastic fiber optics (e.g., Polymethyl methacrylate (PMMA) and fluorinated polymers). In one implementation, the fiber optics may carry to one or more thermoelectric generators as discussed further below. The solar concentrator402may include a Fresnel lens which focuses light and infrared radiation from the sun onto a solar radiation collector or a collector plate of the solar concentrator402. The solar concentrator402may be rotatable in order to maximize power generation. For example, the solar concentrator402may be oriented with the sun to maintain proper focus.

In one implementation, the solar concentrator402is a Fresnel lens. The fiber optic bundle terminates to provide a surface that coincides with the focal point of the Fresnel lens. The fiber optic bundle can be cut so it has an angled terminus (a terminus that ends in a 45° angle) and the Fresnel lens is focused on the exposed ends of the cable.

In one implementation, the fiber optic bundle is mounted on a stage to maximize the coupling efficiency of the focused lights from the Fresnel lens. The fiber optic bundle may couple light from the ultraviolet (UV) and infrared (IR) spectra to maximize the heating.

The concentrated light rays heat the air in the hot side module304. In one implementation, the concentrated light rays may heat directly the second thermoelectric layer and/or the hot side module304as shown inFIG. 5.

FIG. 5is a schematic that shows the heat generator306according to another example. The heat generator306includes a heat concentrator510, a hot air tank502, and a third air exhaust508. The hot air tank502is coupled to the hot side module304via a first air conduit504. The hot side module304is coupled to the third air exhaust508via a second air conduit506.

The heat concentrator510may include a solar concentrator that focus light and infrared radiation on the hot air tank502to heat the air. The solar concentrator includes two or more solar concentrators that focus light on multiple locations of the hot air tank502. Each of the solar concentrators may include multiple parabolic units configured to focus light on one location of the multiple locations. The two or more solar concentrators are mounted on a controlled stage to track the sun to maximize efficiency.

In addition or alternatively, air may be heated in an insulated conduit using the heat concentrator510. The insulated conduit may be positioned along the focal location (e.g., focal axis) of each parabolic unit of the solar concentrator. In other words, multiple heat concentrators are positioned so as the insulated conduit is in the direct path of the reflected solar light rays. A first end of the insulated conduit is coupled to the hot side module304. A second end of the insulated conduit is coupled to the hot air tank502. Thus, air in the insulated conduit get heated and flow towards the hot side module304.

In one example, the hot side module304and the cold side module204may include compressed air to facilitate heat exchange. The subterranean air cooling module202may receive compressed air from an air compressor or a compressed air storage tank. Further, the hot air tank502may be filled with compressed air. The third exhaust508may be coupled to the hot air tank502to recycle air in the system.

FIG. 6is a schematic600that shows an illustration of the system according to one example. The TEG606includes a cold side612and a hot side614. A cold side module608is disposed in a parallel fashion with respect to the cold side612. The cold side module608may be in a direct contact with the TEG606. A hot side module610is disposed in a parallel fashion with respect to the hot side614of the TEG606. The hot side module610may be in a direct contact with the TEG606. Hot air to the hot side module610is heated using solar energy. The light rays are directed to the hot side module610using fiber optics628from a solar concentrator626. In addition, solar energy is used to heat a hot air tank622. The hot air tank622has an input to receive air at ambient temperature. The air is heated in the hot air tank622and directed to the hot side module610via conduit620. The hot side module610is connected to a third air exhaust616via conduit618. The concentration of air at the third air exhaust616creates a natural flow from the hot air tank622towards the hot side module610then towards the third air exhaust616.

The cold side module608is coupled to a first air exhaust602via conduit624. Cold air is provided to the cold side module608via an underground conduit604. Air at ambient temperature is cooled when passed through the underground conduit604. The first air exhaust602may be heated by solar energy to create a natural air flow from the underground conduit604towards the first air exhaust602.

FIG. 7is a schematic that shows a system700for generating energy from a plurality of thermoelectric generators according to one example. In one implementation, the system700may include a first thermoelectric generator102a, a second thermoelectric generator102b, and a third thermoelectric generator102c. The system700may include a processor702to control the operation of each of the first thermoelectric generator102a, the second thermoelectric generator102b, and the third thermoelectric generator102c. The TEGs may be arranged in a vertical fashion to minimize ground space usage. The processor702may control one or more systems of the solar concentrator402associated with each of the first thermoelectric generator102a, the second thermoelectric generator102b, and the third thermoelectric generator102c. For example, the processor702may control the stage associated with each of the solar concentrator402to follow the sun to maximize efficiency.

In one implementation, a solar concentrator may be coupled to two or more thermoelectric generator system. For example, the fiber optics may carry light rays to the first thermoelectric generator102a, the second thermoelectric generator102b, and the third thermoelectric generator102cfrom a single solar concentrator. A first end of the fiber optics is coupled to the concentrator and a second end is coupled to a fiber optic splitter. For example, a 1×3 equal ratio splitter may be used to divide the concentrated solar light rays into 3 beams, each representing ⅓ of the concentrated solar light rays. Each beam is coupled to hot side modules associated with each of the first thermoelectric generator102a, the second thermoelectric generator102b, and the third thermoelectric generator102c. A non-equal ratio splitter may be used to direct a larger portion of the concentrated solar light rays towards one of the thermoelectric generators. For example, 50% of the concentrated light rays are directed to a first hot side module, 25% of the concentrated light rays are directed to a second hot side module, and 25% are directed to a third hot side module when the predetermined volume of air associated with the first hot side module is greater than the predetermined volume of air held in the second and the third hot side module.

FIG. 8is a flowchart for a method800for generating power using the thermoelectric generator according to one example. At step S802, a hot side of a thermoelectric generator is heated via concentrated rays of the sun.

At step S804, a cold side of the thermoelectric generator is cooled via air cooled via an underground conduit. The underground conduit is positioned at a predetermined distance beneath ground.

At step S806, an output of the thermoelectric generator is connected to a transformer to provide a voltage based on the user requirements.

FIG. 9is a schematic that shows a system900for generating energy from a plurality of thermoelectric generators according to one example. The cold side module may provide cooling for two or more TEGs102. For example, a first side of the cold side module904is in direct contact with a cold side of a first TEG902aand a second side of the cold side module904is in direct contact with the cold side of a second TEG902b. In addition, as discussed previously herein, the first side of the cold side module904may provide cooling to multiple TEGs. In one implementation, an entire outer surface of the cold side module is in contact with cold sides of multiple TEGs. In one implementation, 25 TEGs may be arranged in a single 5×5 matrix between the cold side module204and the hot side module304.

A system which includes the features in the foregoing description provides numerous advantages to users. In particular, the system is practical, relatively inexpensive, durable, and easy to maintain. The system described herein provides electricity for long period. The system described herein has low noise generation and does not include moving parts.