Exo Terra-TESS

Description

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application claims benefit of U.S. Provisional Patent Application No. 63/686,554 filed Aug. 23, 2024, which is incorporated herein by reference in its entirety and for all purposes.

FIELD

The technology herein relates to thermal storage devices.

BACKGROUND

Thermal storage (“TESS”) systems typically require exhaustive and expensive insulation to retain the stored energy. Solar concentrators typically result in temperatures exceeding 1000 C at the focal point. The material that can handle this temperature are cost prohibitive. To further move the heat from the point of source convectively, the subsequent system pressure drop reduce the round trip efficiencies significantly.

Moreover, TESS systems are subject to severe parasitic losses during the convective charging and discharge cycles. Eliminating parasitic losses during the charge cycle, and optimizing the TESS performance during the discharge cycle are worthy goals.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram of an example underground TESS silo “pod”.

FIG. 2 shows an example parallel discharge from a number of TESS pods to a heat sink such as a Stirling engine

FIG. 3 shows an example serial discharge from a number of TESS pods to a heat sink such as a Stirling engine

FIG. 4 is a block diagram of an example underground TESS silo “pod”.

FIG. 5 shows an example parallel discharge from a number of TESS pods to a heat sink such as a Stirling engine via convection.

FIG. 6 shows an example serial discharge from a number of TESS pods to a heat sink such as a Stirling engine via convection.

FIG. 7 is a block diagram of an example underground TESS silo “pod” using high temperature heat pipes.

FIG. 8 shows an example parallel discharge from a number of TESS pods to a heat sink such as a Stirling engine via high temperature heat pipe.

FIG. 9 shows an example series discharge from a number of TESS pods to a heat sink such as a Stirling engine via high temperature heat pipe.

DETAILED DESCRIPTION OF NON-LIMITING EMBODIMENTS

In one embodiment, a heat storage system comprises a first heat storage pod, a second heat storage pod, and thermal connections to thermally connect the first heat storage pod and the second heat storage pod either together in series or in parallel to a heat sink, wherein the first heat storage pod is designed to have a different heat transfer rate as compared to the second heat storage pod.

The thermal connections can comprise heat pipes and/or convection paths.

In one embodiment, at least one of the thermal connections comprises a heat pipe wherein the heat pipe comprises an envelope, a wick structure and working fluid.

The heat pipe comprises an evaporator that causes the working fluid to change state from liquid state to vapor which moves to a colder, condenser of the heat pipe where it releases its latent heat and condenses back to the liquid state.

The wick structure causes the working fluid in the liquid state to flow back to the evaporator.

Flow of the working fluid is continuous across the heat pipe with little temperature difference across the heat pipe.

At least some of the thermal connections comprise convection paths.

In one embodiment, a heat storage method comprises storing heat in a first heat storage pod, storing heat in a second heat storage pod, and moving heat from the first heat storage pod and/or the second heat storage pod via a thermal connection that thermally connects the first heat storage pod and the second heat storage pod either together in series or in parallel to a heat sink, wherein moving heat to/from the first heat storage pod is at a different heat transfer rate as compared to moving heat to/from the second heat storage pod.

At least one of the thermal connections comprises a heat pipe.

The heat pipe comprises an envelope, a wick structure and working fluid.

An evaporator may cause the working fluid to change state from liquid state to vapor and moving the vapor to a colder, condenser of the heat pipe where it releases latent heat and condenses back to the liquid state.

The wick structure may be used to cause the working fluid in the liquid state to flow back to the evaporator.

Continuous flow of the working fluid across the heat pipe may be provided with little temperature difference across the heat pipe.

At least some of the thermal connections may comprise convection paths.

Example embodiments provide a compact TESS “pod” or module that eliminates parasitic losses during the charge cycle, optimizes TESS performance during the charging cycle by having an option to discharge in series or parallel configuration, and reduces the TESS foot print.

In one embodiment, as FIG. 1 shows, the TESS media (combination of ceramic, sedimentary and/or metamorphic substances) is encapsulated underground and contained in a packed bed form. Collected radiant energy (e.g., from an optical solar collection system including Fresnel lenses and/or reflectors) can be directly stored into the TESS media without requiring it to be transported out for the risk of material breakdown. This eliminates the pressure drop losses during the charging process.

Several individual TESS pods can be tailored to utilize TESS media with varying thermal properties. For example, utilizing a high thermal conductive material such as graphite flakes in a pod will enable faster charge/discharge durations in comparison to those with poor thermal properties. This will be helpful in scenarios when a shorter discharge ramp rates are desired. An array of different TESS pods with different charge/discharge rates can provide a mix of fast and slow charge/discharge rates. For example, a TESS pod with a faster discharge rate can provide a faster ramp for a Stirling engine to begin operating, and less expensive, slower discharge rate TESS pods can be used to supply heat once the Stirling engine has begun operating. Such hybrid systems can provide at low cost, additional flexibility that may not be present in single-pod systems.

Such compact TESS pods can be used in combination to provide additional capacity and capabilities. An arrangement of any array of TESS pods enable heated working fluid discharge modes via series or parallel configuration as shown in FIGS. 2 and 3. Thus, multiple TESS pod can concurrently discharge stored heat either in parallel (FIG. 2) or in series (FIG. 3) to a shared heat sink (“DPD”) such as a Stirling engine.

In the FIG. 2 arrangement, multiple TESS pods supply heat to a common shared heat sink to thereby increase storage capacity and create redundancy. If one TESS pod fails, the others can continue to operate and supply heat to the common heat sink. Different TESS pods can have different heat storage capacities and can store heat from different respective sources.

The serial connections of FIG. 3 can provide increasingly elevated temperature for supplying to the sink or load, where a second series-connected pod increases the temperature of the heat output of a first pod, a third series-connected pod increase the temperature of the heat output of the second pod, and so on. Different pods can use different materials to provide desired performance without any cross-contamination or interference issues.

In one embodiment shown in FIGS. 4, 5, and 6, the thermal connections between pods can be via convection. For example, electrical operated blowers can move heated air as a working fluid through high temperature ductwork.

In another embodiment shown in FIGS. 7, 8 and 9, the thermal connections between pods can be via heat pipes (HTHP”). Heat pipes are devices to move heat collected at a source very quickly and efficiently from one point to another. For example, many high performance integrated circuit chips such as microprocessors and GPUs that generate a lot of heat use a heat pipe to remove the heat away from the chip die. The moved heat can then be released or exchanged to the ambient environment.

One type of known heat pipe comprises a passive two-stage heat transfer device that uses a fluid's high latent heat of vaporization to achieve efficient heat transfer. Such a heat pipe may comprise an envelope, a wick structure and working fluid. Heat is input to an evaporator—a structure that causes the working fluid to change state from liquid to vapor (i.e., causes the liquid to boil). The vapor moves to colder regions of the heat pipe (the “condenser”) where it releases its latent heat and condenses back to the liquid state. A wick structure causes the liquid to flow (passively recirculate or pump) back to the evaporator so the evaporation-condensing process can repeat. The flow can be continuous across the heat pipe with little temperature difference across the heat pipe. See e.g., Seshan et al, Heat pipes—concepts, materials and applications, Energy Conversion and Management Volume 26, Issue 1986, Pages 1-9, doi.org/10.1016/0196-8904(86)90025-7. In such example arrangements, the evaporator side of the heat pipe is disposed within the heat storage pod, and the condenser side of the heat pipe is used to connect the heat storage pod to outside devices, i.e. other heat storage pods and/or a thermal sink such as a Stirling engine.

Advantages include eliminating charging losses, utilizing in-ground reduced temperature fluctuation to hold heat efficiently, and the ability to scale by adding additional pods.

Although the examples above show multiple TESS pods providing heat to a common heat sink, in other embodiments a common heat source can be substituted for the common heat sink.

All patents and publications cited herein are incorporated by reference as if expressly set forth.

While the invention has been described in connection with what is presently considered to be the most practical and preferred embodiments, it is to be understood that the invention is not to be limited to the disclosed embodiments, but on the contrary, is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims.