Patent Description:
Various indoor environments such as data centres, refrigerated warehouses, factories, buildings and so on rely on cooling technologies including chilled-water systems, air-cooled systems, water-cooled systems, glycol-cooled systems, refrigerant-cooled systems and so on [<NUM>] to maintain their temperatures within a range that is sufficiently low for their required applications. Certain indoor environments such as data centres require to be supplied at once with cold energy as well as power. In large-scale data centres (≥ <NUM> kW), the chilled-water system is the most commonly used cooling system. It involves a vapour-compression chiller which is supplied with electricity from the utility grid or a backup power generator to provide the cooling load to the indoor environment. The Power Usage Effectiveness (PUE) is a de facto standard within the data centre industry. It measures the total energy drawn by a data centre (including for cooling, lighting, power network equipment etc.) to the energy consumed by the information technology (IT) equipment, as defined by equation (<NUM>) below.

Lower PUE is desirable as this indicates that the data centre is efficient in terms of energy usage. However, some surveys reported comparable and relatively high PUE average ratings in some parts of the world, for example, <NUM> in Singapore, <NUM> in the United States and <NUM> in Europe [<NUM>].

While liquified natural gas (LNG)-based power and regasification systems appear to be energy-efficient alternatives for electricity and cold energy consumers such as those requiring cooling, refrigeration, freezing etc., use of LNG-based systems requires proximity to LNG terminals which in many cases is not possible.

It is therefore desirable to provide an energy-efficient system for cooling and powering an indoor environment that does not require use of LNG while achieving lower PUE than is currently obtainable using conventional powering and cooling systems.

<CIT> discloses that a method of cooling a data center can include: extracting compressed air from a storage vessel or process stream, expanding the air to lower a pressure of the air, with the ratio of the pressure of air after expansion to the pressure of air before expansion being the critical pressure ratio, defining choked flow, providing a constant mass rate of cooling air, thus lowering a temperature of the air; and dispersing the expanded air through a heat sink onto a microprocessor or other heat generating component of a server or a storage device, thus cooling the microprocessor or the other heat generating component of the server or the storage device.

The presently disclosed cryogenic energy system is a zero-emission polygeneration alternative that uses liquid air or liquid nitrogen or liquid hydrogen or any other suitable cryogen other than LNG to provide efficient "green" power and cooling solution for various indoor environments, such as data centres, warehouses, factories, buildings and so on. The system may serve as a backup power solution or be used during particular on-grid conditions (e.g. grid peak demand, high electricity pricing) to provide combined generation of cooling and power to indoor environments or other end users. When used for data centres, the system can lead to low PUE values of around <NUM> as a result of combined generation of cooling and power. The system is flexible to operate under various configurations (standalone or hybrid, full-setup nominal use or partial-setup use) and various control strategies (electrical-load-following control strategy or a thermal-load-following control strategy or other strategies) depending on occurring events and facility availability. In addition, the system also has the potential for extension and synergistic use with other energy sources, as well as for derivation to further uses such as in thermal energy storage, fire suppression, etc. The system is conceived to be applicable in retrofit mode to existing sites and/or in on-plan mode to future sites that require both power and cooling.

According to the present invention, there is provided a cryogenic energy system for cooling and powering an indoor environment according to claim <NUM>.

In order that the invention may be fully understood and readily put into practical effect, there shall now be described by way of non-limitative example only embodiments of the present invention, the description being with reference to the accompanying illustrative drawings.

Examples of embodiments of a cryogenic energy system <NUM> (also referred to as a cryo-system <NUM> or a cryo-cogenerator <NUM> in this application) will be described below with reference to <FIG>. The same reference numerals are used across the figures to denote the same or similar parts. In the figures, solid lines refer to active components while components and connection depicted in dotted lines are either inactive or optionally activatable.

In general, the cryogenic energy system <NUM> is applicable to all types or layouts of cooling / refrigeration system such chilled water systems, air-cooled systems, water-cooled systems, glycol-cooled systems, refrigerant-cooled systems and so on. In the following description of exemplary embodiments of the cryogenic system <NUM>, the system <NUM> is schematized based on a commonly used conventional cooling system <NUM> (i.e., chilled process) as shown in <FIG>. The conventional cooling system <NUM> is typically composed of a chiller <NUM>, a cooling tower <NUM>, a cooling unit <NUM> (e.g. computer room air conditioning unit or air handler (CRAC/CRAH)) for removing heat from air in the indoor environment, a heat removal loop <NUM> within the indoor environment <NUM>, a first heat transfer loop <NUM> transferring waste heat from the cooling unit <NUM> to the chiller <NUM> (e.g. via a water return) and providing cold flux from the chiller <NUM> to the cooling unit <NUM> (e.g. via a water supply), a second heat transfer loop <NUM> connecting the chiller <NUM> to the cooling tower <NUM> for heat rejection, and two feed pumps <NUM>, <NUM> for the fluid circulation in the first and second heat transfer loops <NUM>, <NUM> respectively.

In all embodiments, as shown in <FIG> and <FIG>, the cryogenic energy system <NUM> comprises a cryogenic open loop <NUM> and a heat supply open loop <NUM> wherein at least one of the cryogenic loop <NUM> and the heat supply open loop <NUM> are in thermal connection with the conventional cooling system <NUM> to provide cold flux to the indoor environment <NUM> that is cooled by the conventional cooling system <NUM>.

The cryogenic loop <NUM> comprises an open thermodynamic cycle that uses liquid air or liquid nitrogen or liquid hydrogen or any other suitable cryogen <NUM> (pure substance or a mixture of various substances) except LNG for the combined generation of cold energy and power. The cryogenic loop <NUM> comprises a cryogen supply <NUM> that may be provided in the form of one or more tanks stored onsite or supplied externally (e.g., via a supply through-pipe from a gas production plant where the cryogen is supplied in a gaseous state). When the cryogenic loop <NUM> is fuelled by cryogenic fluids <NUM> stored in tanks onsite, the cryogenic energy system <NUM> is an autonomous cogenerator as it does not require direct coupling to an external regasification process. Optionally, an external cryogen supply <NUM> provided at a desired pressure may also be connected to the cryogenic loop <NUM> to provide more cryogen to the cryogenic loop <NUM>.

The cryogenic loop <NUM> further comprises at least one transfer-expansion stage. <FIG>, <FIG>, and <FIG> depict single stage embodiments of the cryogenic energy system <NUM> that comprise one transfer-expansion stage in the cryogenic loop <NUM> while <FIG> depict multistage embodiments of the cryogenic energy system <NUM> that comprise two transfer-expansion stages in the cryogenic loop <NUM>. Single stage embodiments offer simplicity to the system <NUM> and occupies less space. In the multistage embodiments, two or more transfer-expansion stages can lead to a decrease in cryogen <NUM> consumption and offer self-redundancy to the system <NUM> by providing each of the plurality of transfer-expansion stages in the multistage embodiments with a bypass configured to allow each of the plurality of transfer-expansion stages to be selectably bypassed in case it is not serviceable for any reason. For example, if one transfer-expansion stage is out of service (e.g., partial failure, maintenance issue or other situations), the system <NUM> can still operate by activating the associated bypass of the non-serviceable transfer-expansion stage and involve only the available other transfer-expansion stage(s). Also, use of all multiple stages in the cryo-system <NUM> under nominal operation leads to lowest cryogen consumption.

Each transfer-expansion stage comprises at least one heat exchanger that includes one evaporator <NUM> and may or may not include one or more superheaters <NUM> or one or more reheaters <NUM>, as will be described in greater detail below. Each transfer-expansion stage also comprises one power unit <NUM> or <NUM> to generate electricity. The electricity may be used to at least partially power the indoor environment <NUM>, and may be provided directly to the indoor environment <NUM> or to a grid that provides power to the indoor environment <NUM>. The power unit <NUM>, <NUM> may comprise expansion machinery such as a power turbine or positive-displacement machine or any other engine and a power generator. For two-stage embodiments of the system <NUM>, the turbines <NUM>, <NUM> in the two transfer-expansion stages may be named according to the pressure level they each experience: turbine HP (high pressure) <NUM> and turbine LP (low pressure) <NUM> respectively.

The cryogenic loop <NUM> may further comprise an optional preheater <NUM> arranged to provide an internal heat transfer within the cryogenic loop <NUM>. The cryogenic loop <NUM> may also further comprise two optional cold recuperators <NUM>, <NUM> provided in parallel downstream of the last transfer-expansion stage <NUM> or <NUM> wherein the first and second cold recuperators <NUM>, <NUM> respectively directly connect the output of the last transfer-expansion stage <NUM> or <NUM> to the first and second heat transfer loops <NUM> and <NUM> respectively of the conventional cooling system <NUM> of <FIG>.

The cryogenic loop <NUM> also comprises a pump or compressor <NUM> to move the cryogen <NUM> through the cryogenic loop <NUM> and piping (including valves, by-pass lines and drain lines) that place the cryogen supply <NUM>, the preheater <NUM> (optional), at least one transfer-expansion stage and the cold recuperators <NUM>, <NUM> (optional) in series connection in the given order.

In the cryogenic open loop <NUM>, the cryogen <NUM> (at subzero temperature and liquid state in some embodiments) may be successively compressed through the feed pump or compressor <NUM> (at subcritical or supercritical pressure), gasified in the preheater <NUM>, heated up by transferring cold flux to either the heat supply open loop <NUM> (to be described in greater detail below) or the cooling system first heat transfer loop <NUM> through at least one of the active heat exchanger(s) <NUM>, <NUM>, <NUM> and then expanded through the active power unit(s) <NUM>, <NUM> to deliver gross power output. A fraction of this power output may be used to cover auxiliary power consumption by the system <NUM> itself, such as to power the motor-pump(s) or compressor <NUM> and a blower/compressor <NUM> of the heat supply loop <NUM>.

In the cryogenic loop <NUM>, available energy at the exit <NUM> of the last turbine or power unit <NUM> or <NUM> can be recovered according to different modes. For example, the available energy can be internally transferred as a hot flux to preheat the cryogen through the preheater <NUM> prior to heating of the cryogen by the evaporator <NUM>, or directly transferred as a cold flux to the cooling system first heat transfer loop <NUM> through a first cold energy recuperator <NUM> and / or as a cold flux to the cooling unit second heat transfer loop <NUM> through a second cold energy recuperator <NUM> to cover a cooling part-load and/or to fully or partially support the heat rejection process when the chiller(s) <NUM> is operating together with the cryo-cogenerator <NUM>, thus resulting in a further reduction of the cryogen consumption. The cold energy still available at the exit <NUM> of the preheater <NUM> or at the exit <NUM> of the last stage <NUM> or <NUM> of the cryogenic open loop <NUM> can also be subject to optional Cold Energy Storage (CES) or to optional external use.

Optionally, additive fluid <NUM>, <NUM> such as helium, hydrogen or any other suitable additive may be injected into the cryogenic open loop <NUM> to be mixed with the cryogen <NUM> at the entrance of the turbine(s) <NUM>, <NUM> respectively. This would increase the power density and thus decrease the cryogen consumption. Considering this option, the determination of the mass fraction of the additive fluid <NUM>, <NUM> can be a trade-off between the total storage volume for cryogen (land space) and the operational cost.

The heat supply open loop <NUM> provides a hot fluid to drive the power generation process. The heat supply open loop <NUM> is configured to be able to use hot fluid from a hot fluid source <NUM> such as ambient air which is free, or to use other hot fluids instead of ambient air, such as a glycol-water mixture or other fluids such as water (e.g. from a river or lake), as the hot fluid to provide heat flux to the cryogenic loop <NUM> for power generation when the cryogenic energy system <NUM>, as shown in <FIG>.

The heat supply open loop <NUM> is further configured to be able to use an alternative hot or warm fluid <NUM> from an external process (instead of ambient air or other hot fluid sources <NUM>) that is passed from an active line <NUM> from the external process to the heat supply open loop <NUM> as the hot fluid to provide heat flux at high temperature to the cryogenic open loop <NUM>, thus increasing the turbine inlet temperature in each expansion stage of the cryogenic loop <NUM>.

Use of alternative hot or warm fluid from an external process <NUM> may be considered a hybrid operation of the cryogenic energy system <NUM> as shown in <FIG> where the cryo-cogenerator <NUM> is coupled with a fuel-based power generation process (e.g. internal combustion engine, fuel cell) or other process via the heat supply open loop <NUM>. This enables reduction of the specific consumption of cryogen <NUM> compared to when the cryogenic energy system <NUM> is operated as a standalone cryo-cogenerator <NUM> using ambient air <NUM> or another hot fluid source <NUM> to provide heat flux. The hybrid cryo-cogenerator <NUM> offers higher redundancy and higher functionality levels compared to the standalone cryo-cogenerator <NUM> due to the multi-energy vector. Accordingly, the alternative hot/warm fluid <NUM> may comprise exhaust gases, vapour, fuel, refrigerant such as flue gases in the case of hybrid operation with a combustion engine process or exhaust gases and vapour / stack coolant outlet / surplus fuel return in the case of hybrid operation with a fuel cell process.

For certain hot fluids such as stack coolant or surplus fuel from a fuel cell process, the fluid is preferably not discharged at the exit of the heat supply open loop but subject to recirculation.

Under hybrid operation with a combustion engine process supplying the hot fluid <NUM> in the heat supply open loop <NUM>, a part of the cold energy delivered by the cryogenic open loop <NUM> can be used for Cryogenic Carbon Capture and Storage (CCCS) from the flue gases. Under hybrid operation with a fuel cell process supplying the hot fluid <NUM> in the heat supply open loop <NUM>, the use of liquid hydrogen <NUM> as a cryogen is advantageous as the cryogenic open loop <NUM> can supply the fuel cell process with the exhausting hydrogen gas. A part of the cold energy delivered by the cryogenic open loop <NUM> can be used for the stack cooling process.

The heat supply open loop <NUM> further comprises a blower or compressor or pump <NUM> for air flow (depending on the pressure losses within the loop <NUM>) or liquid flow through the heat supply open loop <NUM> as well as appropriate pipes and valves to establish fluid connection between components in the heat supply open loop <NUM>.

The heat supply open loop <NUM> is thermally connected to the cryogenic loop <NUM> (via direct or indirect connections <NUM>, <NUM>, <NUM>) to effect heat exchange between the hot fluid <NUM> or <NUM> in the heat supply open loop <NUM> with the cryogen <NUM> in the cryogenic loop <NUM>.

Where the connection <NUM>, <NUM>, <NUM> is direct, as shown in <FIG>, the hot fluid <NUM> or <NUM> is directly connected to a heat exchanger of at least one of the evaporator <NUM> (e.g. <FIG>), the superheater <NUM> (e.g. <FIG> and <FIG>) or the reheater <NUM> (e.g. <FIG> and <FIG>) of the cryogenic loop <NUM>, where such is provided, as will be described in greater detail below. Alternatively, where the connection <NUM>, <NUM>, <NUM> is indirect, exemplary embodiments of the indirect connection as shown in <FIG> may comprise one or more intermediate heat transfer loops in which CO<NUM>, glycol-water mixture or other suitable fluid is passed through a pump or compressor <NUM> to an intermediate heat exchanger <NUM> of the intermediate heat transfer loop for heat exchange with (i.e. heat transfer from) the hot fluid <NUM> or <NUM>. In the embodiment shown in <FIG>, the fluid in the intermediate heat transfer loop is then passed through an expansion valve <NUM> to the heat exchanger of the evaporator <NUM>, superheater <NUM> or reheater <NUM> as the case may be for heat exchange with (i.e. transfer to) the cryogen <NUM> in the cryogenic loop <NUM>. This can be adopted to limit the freezing of the air moisture content in the heat exchanger(s) <NUM>, <NUM>, <NUM>, especially in humid climates.

Other exemplary embodiments as shown in <FIG> of the indirect connection <NUM>, <NUM>, <NUM> include a topping thermodynamic cycle for a higher performance of the system <NUM> with or without an intermediate heat transfer loop. The topping cycle is a closed cycle using a further cryogen for power generation and contains a pump (or a compressor) <NUM>, a topping cycle heat exchanger <NUM> and a topping cycle power unit <NUM> that may comprise expansion machinery (such as a power turbine) and a power generator. The further cryogen is passed through a pump or compressor <NUM> to the topping cycle heat exchanger <NUM> for heat exchange from the hot fluid <NUM> or <NUM> to the further cryogen. The heated further cryogen is then expanded through the power unit <NUM> and passed to the heat exchanger of the evaporator <NUM>, superheater <NUM> or reheater <NUM> as the case may be for heat exchange with (i.e. transfer to) the cryogen <NUM> in the cryogenic loop <NUM>. Where a topping cycle is included, the cryo-system <NUM> is a cryogenic cascade where the cryogenic loop <NUM> comprises a bottoming open cycle in addition to the topping cycle provided in the indirect connection between the heat supply open loop <NUM> and the cryogenic loop <NUM>. Exemplary embodiments of the cryogenic cascade include a nitrogen-based bottoming open cycle + argon-based topping closed cycle; a hydrogen-based bottoming open cycle + nitrogen-based topping closed cycle; a hydrogen-based bottoming open cycle + argon-based topping closed cycle; a nitrogen-based bottoming open cycle + hydrocarbon-based topping closed cycle; and a hydrogen-based bottoming open cycle + hydrocarbon-based topping closed cycle. Where a topping cycle is included together with a preheater <NUM>, the preheater <NUM> may alternatively be located immediately downstream of the evaporator <NUM> instead of upstream of the evaporator as shown in <FIG> and <FIG>, depending on the properties of the further cryogen used in the topping cycle and the operating conditions of the topping cycle.

Notably, all embodiments of the cryogenic energy system <NUM> comprise an evaporator <NUM> for heat transfer to the cryogen <NUM>.

In configurations where the system <NUM> depends solely on hot fluid <NUM> or <NUM> provided by the heat supply open loop <NUM> for heat flux such that the heat supply open loop <NUM> is the only driver for power generation (as shown in <FIG>, <FIG>, <FIG>, <FIG> and <FIG>), heat exchange between the hot fluid <NUM> or <NUM> and the cryogen <NUM> is configured to take place at the evaporator <NUM> via a direct or indirect connection <NUM> as described above. In such configurations, the system <NUM> may optionally further comprise a superheater <NUM> in addition to the evaporator <NUM> for further heat exchange between the hot fluid <NUM> or <NUM> and the cryogen <NUM> for better performance, wherein the evaporator <NUM> and superheater <NUM> are provided in a serial-parallel cascade configuration in the direct or indirect connection <NUM>.

In configurations of the system <NUM> where the heat supply open loop <NUM> is not the only supplier of heat flux as the driver for power generation (as will be described in greater detail below), the system <NUM> includes at least one superheater <NUM> (as shown in <FIG>, <FIG>, <FIG>, <FIG>, <FIG>, <FIG>, <FIG> and <FIG>) in direct or indirect connection <NUM> (as described above) with the heat supply open loop <NUM> for heat exchange between the hot fluid <NUM> or <NUM> and the cryogen <NUM>. Multiple superheaters <NUM> may be provided in the connection <NUM> in serial-parallel cascade configuration for better performance.

Multistage embodiments of the cryogenic system <NUM> (as shown in <FIG>) include at least one reheater <NUM> in direct or indirect connection <NUM> (as described above) with the heat supply open loop <NUM> for further heat exchange between the hot fluid <NUM> or <NUM> and the cryogen <NUM>. Multiple reheaters <NUM> may be provided in the connection <NUM> in serial-parallel cascade configuration for better performance.

At the exit <NUM> of the heat supply open loop <NUM>, the excess cold energy may be released to surroundings or alternatively delivered to other locations for cooling purposes. In cases where the hot fluid <NUM> comprises glycol-water (or liquid use in general), the exhausted cold liquid can be collected and warmed back by free convection for future reuse (recycling). This option would require an additional space for liquid storage and recovery, but has the advantage of reducing the auxiliary power consumption (and thus the cryogen consumption) since in this case a liquid pump is used instead of an air blower/compressor.

As mentioned above, the heat supply open loop <NUM> can be designed to serve as the only driver of the gasification and power generation processes or another heat source can be provided in addition to the heat supply open loop <NUM> to drive the gasification and power generation processes, depending on the application.

In cases where there is no cooling requirement or a non-important thermal load, the heat supply open loop <NUM> can be used as the only driver of the gasification and power generation processes. In such cases, as shown in <FIG>, <FIG>, <FIG>, <FIG> and <FIG>, the heat supply open loop <NUM> also serves as an intermediate heat transfer loop between the cryogenic loop <NUM> and the first heat transfer loop <NUM> transferring waste heat from the cooling unit <NUM> of the conventional cooling system <NUM>. In such cases, fluid in the heat transfer open loop <NUM> that has gone through heat exchange with the cryogen <NUM> receives the waste heat from the cooling unit <NUM> via a heat exchanger or cooler <NUM> that connects the first heat transfer loop <NUM> with the heat supply open loop <NUM> downstream of the heat exchanger(s) <NUM>, <NUM>, <NUM> in the cryogenic loop <NUM>. In other words, when the heat supply open loop <NUM> is the only driver used for power generation, the received cold flux or a part of the received cold flux from the cryogenic loop <NUM> is retransferred from the heat transfer open loop <NUM> to the first heat transfer loop <NUM> of the conventional cooling system <NUM> through the cooler <NUM>.

In cases involving an important thermal load (e.g. removing waste heat from server racks in a data centre), removed heat from the indoor environment <NUM> can be used as an additional or alternative source of heat to drive power generation in the cryogenic loop <NUM>, as shown in <FIG>, <FIG>, <FIG>, <FIG>, <FIG>, <FIG> and <FIG>. For example, the removed heat from the second heat transfer loop <NUM> of the conventional cooling system <NUM> and the outside ambient air <NUM> may together serve as dual hot sources for the cryo-cogenerator <NUM>. In such cases, the heat supply open loop <NUM> is connected only to the cryogenic loop <NUM> and has no connection with any heat transfer loops <NUM>, <NUM> or <NUM> of the conventional cooling system <NUM>. In such cases, the heat transfer loop <NUM> of the cooling unit <NUM> is thermally connected to the gasification segment of the cryogenic loop <NUM> at the evaporator <NUM> via a direct or indirect connection <NUM>. The direct or indirect connection <NUM> may be the same as any of the direct or indirect connections <NUM>, <NUM>, <NUM> described above with reference to <FIG>.

For certain applications where the cold energy requirement of the indoor environment <NUM> is much higher than the electricity requirement (e.g. warehouses, district cooling, etc.), the heat supply open loop <NUM> does not have to be implemented (as can be seen in <FIG> and <FIG>) as the removed heat from the indoor environment <NUM> is sufficient to drive the power generation processes.

By providing the cryogenic energy system <NUM> with a heat supply open loop <NUM>, the cryogenic energy system may be operated under either an electrical-load-following control strategy or a thermal-load-following strategy. Electrical-load-following means that the cryogenic energy system <NUM> will have to first satisfy the energy requirement of the indoor environment <NUM> in terms of electricity. Thermal-load-following means that the cryogenic energy system <NUM> will have to first satisfy the energy requirement of the indoor environment <NUM> in terms of cold energy.

Electrical-load-following is the convenient control strategy to generate backup power since, during a power outage, the cryo-cogenerator <NUM> must provide a net power output fully satisfying the electricity requirement of the indoor environment <NUM> (e.g. IT load in a data centre). Here, the heat supply open loop <NUM> is able to assure high air flow rates from the outside to fulfil that requirement but this could then result in an excess of cold energy being produced and relatively high cryogen consumption.

Thermal-load-following control strategy would not lead to an excess of cold energy production and to relatively high cryogen consumption. It is more adapted to on-grid use depending on the interest (e.g. electrical load supplied by the utility grid and the cryo-cogenerator <NUM> jointly) or to generate decentralized power or backup power for particular end-users <NUM> where the electricity requirement is much lower than the cold energy requirement (e.g. decentralized power for tropical islands, backup power for warehouses or shopping malls or others). It is worth noting that, under-thermal-load following control strategy, it is possible to allocate a share of the produced power to drive the main cooling facility (e.g. chiller(s)) and provide a cooling part-load, which results in a reduction of the cryogen consumption.

In the hybrid configuration, the cryo-cogenerator <NUM> can be used as a backup power generator when operated under thermal-load-following control strategy or other particular control strategies. This can be achieved since the electrical load is supported by both processes the cryo-cogenerator <NUM> and the external fuel-based power generation process from which the hot fluid <NUM> in the heat supply open loop <NUM> is supplied. For high source temperatures, the operating conditions and accordingly the turbine(s) <NUM>, <NUM> inlet temperature(s) can be varied according to the needs (e.g. operational cost, emission level limit, etc.) of the indoor environment <NUM>. From certain high turbine inlet temperatures, the cold energy recuperation at the exit <NUM> of the last cryogenic turbine <NUM> or <NUM> is no longer applicable and the resulting regime of the cryo-system <NUM> cannot fully support the required thermal load. In this case, the conventional chiller(s) is/are required to add cold energy and is/are supplied by the hybrid cryo-cogenerator <NUM>.

Where an additive fluid <NUM>, <NUM> is injected into the cryogenic open loop <NUM> as discussed above, from a certain mass fraction of the additive fluid <NUM>, <NUM>, electrical-load-following may lead to a lack of cooling; in this case, thermal-load-following becomes the convenient control strategy to generate backup power.

In all configurations, within the cooling system first heat transfer loop <NUM>, the main cooling facility (e.g. chiller) <NUM> may be by-passed if the cryo-cogenerator <NUM> is fully supporting the cooling load (as shown in <FIG>).

Exemplary embodiments of exemplary implementations of the cryogenic energy system <NUM> will now be described with reference to <FIG>.

<FIG> depicts the exemplary dual stage system <NUM> of <FIG> configured as a standalone cryogenic energy system <NUM> operated under electrical-load-following control strategy, with the full-setup in nominal use where multiple transfer-expansion stages are connected in series and in use. Electrical-load-following is a convenient control strategy to generate backup power since, during a power outage, the cryo-cogenerator <NUM> must provide a net power output fully satisfying the electricity requirement of the indoor environment <NUM> (e.g. IT load in a data centre). During nominal operation (lowest cryogen consumption), both of the transfer-expansion stages are functioning. Therefore, the bypasses of both stages are inactive. The cryogen <NUM> is consecutively pressurized in the motor-pump <NUM>, gasified in the preheater <NUM>, heated up in the evaporator <NUM> and the superheater(s) <NUM>, expanded in the turbine HP <NUM>, reheated in the reheater(s) <NUM>, expanded again in the turbine LP <NUM>, cooled down further in the preheater <NUM>, and then exhausted <NUM>. The generators coupled to the turbines <NUM>, <NUM> deliver power outputs that fully satisfy the electricity requirement of the indoor environment <NUM>. This can be assured since the heat supply open loop <NUM> is able to add the necessary heat flux for backup power generation from ambient air <NUM> or another hot fluid source <NUM>. As the cryogen consumption is controlled following the electrical load requirement, cold energy that still available at the exit <NUM> of the preheater <NUM> is not needed for internal use and can be subject to loss or to optional storage or to optional external use. The cold recuperators <NUM>, <NUM> connected to the conventional cooling system <NUM> are then inactive. In the cooling system first heat transfer loop <NUM>, all the required cold energy for the cooling load is received from the cryogenic open loop <NUM> via the evaporator <NUM> while the chiller <NUM> and its related heat rejection process (i.e. cooling system second heat transfer loop <NUM>) are inactive.

<FIG> depicts the exemplary dual stage system <NUM> of <FIG> configured as a standalone cryogenic energy system <NUM> operated under electrical-load-following control strategy, under partial-setup use where the low pressure transfer-expansion stage (stage LP) <NUM>, <NUM> is out of service. Electrical-load-following is a convenient control strategy to generate backup power since, during a power outage, the cryo-cogenerator <NUM> must provide a net power output fully satisfying the electricity requirement of the indoor environment <NUM> (e.g. IT load in a data centre). If stage LP is out of service (e.g. partial failure, maintenance issue or other situations), only the high pressure transfer-expansions stage (stage HP) <NUM>, <NUM>, <NUM> will be functioning. Therefore, the bypass of stage LP is activated to skip the reheater <NUM> and turbine LP <NUM>. The cryogen <NUM> is consecutively pressurized in the motor-pump <NUM>, gasified in the preheater <NUM>, heated up in the evaporator <NUM> and the optional superheater <NUM>, expanded in the turbine HP <NUM>, cooled down further in the preheater <NUM>, and then exhausted <NUM>. The generator coupled to turbine HP <NUM> delivers power output that fully satisfies the electricity requirement of the indoor environment <NUM>. This can be assured since the heat supply open loop <NUM> is able to add the necessary heat flux for backup power generation from ambient air <NUM> or another hot fluid source <NUM>. As the cryogen consumption is controlled following the electrical load requirement, cold energy that still available at the exit <NUM> of the preheater <NUM> is not needed for internal use and can be subject to loss or to optional storage or to optional external use. The cold recuperators <NUM>, <NUM> connected to the conventional cooling system <NUM> are then inactive. In the cooling system first heat transfer loop <NUM>, all the required cold energy for the cooling load is received from the heat supply open loop <NUM> via the cooler <NUM> while the chiller <NUM> and its related heat rejection process (i.e. cooling system second heat transfer loop <NUM>) are inactive.

<FIG> depicts the exemplary dual stage system <NUM> of <FIG> configured as a standalone cryogenic energy system <NUM> operated under electrical-load-following control strategy, under partial-setup use where stage HP <NUM>, <NUM>, <NUM> is out of service. Electrical-load-following is a convenient control strategy to generate backup power since, during a power outage, the cryo-cogenerator <NUM> must provide a net power output fully satisfying the electricity requirement of the indoor environment <NUM> (e.g. IT load in a data centre). If stage HP <NUM>, <NUM>, <NUM> is out of service (e.g. partial failure, maintenance issue or other situations), only stage LP <NUM>, <NUM> will be functioning. Therefore, the bypass of stage HP <NUM>, <NUM>, <NUM> is activated to skip the superheater <NUM> and turbine HP <NUM>. The cryogen <NUM> is consecutively pressurized in the motor-pump <NUM>, gasified in the preheater <NUM>, heated up in the evaporator <NUM> and the reheater(s) <NUM>, expanded in the turbine LP <NUM>, cooled down further in the preheater <NUM>, and then exhausted <NUM>. The generator coupled to turbine LP <NUM> delivers power output that fully satisfies the electricity requirement of the indoor environment <NUM>. This can be assured since the heat supply open loop <NUM> is able to add the necessary heat flux for backup power generation from ambient air <NUM> or another hot fluid source <NUM>. As the cryogen consumption is controlled following the electrical load requirement, the cold energy still available at the exit <NUM> of the preheater <NUM> is not needed for internal use and can be subject to loss or to optional storage or to optional external use. The cold recuperators <NUM>, <NUM> connected to the conventional cooling system <NUM> are then inactive. In the cooling system first heat transfer loop <NUM>, all the required cold energy for the cooling load is received from the cryogenic open loop <NUM> via the evaporator <NUM>; the chiller and its related heat rejection process (i.e. cooling system second heat transfer loop <NUM>) are inactive.

<FIG> depicts the exemplary dual stage system <NUM> of <FIG> configured as a standalone cryogenic energy system <NUM> operated under thermal-load-following control strategy when the heat supply open loop <NUM> is active. Thermal-load-following is a convenient control strategy to reduce the cryogen consumption and operational costs when backup power is not a requirement. It is also adapted to generate decentralized power or backup power for particular end-users <NUM> where the electricity requirement is much lower than the cold energy requirement. If the heat supply open loop <NUM> is the only driver for power generation, this loop <NUM> remains also active under thermal-load following-control strategy. Both of the transfer-expansion stages <NUM>, <NUM>, <NUM>, <NUM>, <NUM> are functioning to assure nominal operation. Therefore, the bypasses of both stages <NUM>, <NUM>, <NUM>, <NUM>, <NUM> are inactive. The cryogen <NUM> is consecutively pressurized in the motor-pump <NUM>, gasified in the evaporator <NUM> and the optional superheater <NUM>, expanded in the turbine HP <NUM>, reheated in the reheater(s) <NUM>, expanded again in the turbine LP <NUM>, reheated in the first cold recuperator <NUM> and then exhausted. The generators coupled to the turbines <NUM>, <NUM> deliver power outputs that cover a part-load of the electricity requirement of the indoor environment <NUM>. Since the recovery and use of the cold energy from the exit of stage LP <NUM>, <NUM> is particularly suitable under thermal-load-following control strategy, the first cold recuperator <NUM> is activated to reduce the cryogen consumption and operational costs. In the cooling system first heat transfer loop <NUM>, all the required cold energy for the cooling load is received from both the heat supply open loop <NUM> via the cooler <NUM> and the exit of stage LP <NUM>, <NUM> of the cryogenic loop <NUM> via the first cold recuperator <NUM>; the chiller and its related heat rejection process (i.e. cooling system second heat transfer loop <NUM>) are inactive.

<FIG> depicts the exemplary dual stage system <NUM> of <FIG> configured as a standalone cryogenic energy system <NUM> operated under thermal-load-following control strategy when the heat supply open loop <NUM> is inactive and stage HP <NUM>, <NUM> is used. Thermal-load-following is a convenient control strategy to reduce the cryogen consumption and operational costs when backup power is not a requirement. It is also adapted to generate decentralized power or backup power for particular end-users <NUM> where the electricity requirement is much lower than the cold energy requirement. If the heat supply open loop <NUM> is not the only driver for power generation, this loop <NUM> is inactive under thermal load following control strategy. Stage HP <NUM>, <NUM> is involved and the bypass of stage LP <NUM>, <NUM> is activated to skip the reheater <NUM> and turbine LP <NUM>. The cryogen <NUM> is consecutively pressurized in the motor-pump <NUM>, gasified in the evaporator <NUM>, expanded in the turbine HP <NUM>, reheated in the first cold recuperator <NUM> and then exhausted. The generator coupled to turbine HP <NUM> delivers power output that covers a part-load of the electricity requirement. Since the recovery and use of the cold energy from the exit of stage HP <NUM>, <NUM> is particularly suitable under thermal-load-following control strategy, the first cold recuperator <NUM> is activated to reduce the cryogen consumption and operational costs. In the cooling unit firs heat transfer loop <NUM>, all the required cold energy for the cooling load is received from both the gasification process at the evaporator <NUM> and from the exit of stage HP <NUM>, <NUM> via the first cold recuperator <NUM>; the chiller <NUM> and its related heat rejection process (i.e. cooling system second heat transfer loop <NUM>) are inactive.

<FIG> depicts the exemplary dual stage system <NUM> of <FIG> configured as a standalone cryogenic energy system <NUM> operated under thermal-load-following control strategy when the heat supply open loop <NUM> is inactive and stage LP <NUM>, <NUM> is used. Thermal-load-following is a convenient control strategy to reduce the cryogen consumption and operational costs when backup power is not a requirement. It is also adapted to generate decentralized power or backup power for particular end-users <NUM> where the electricity requirement is much lower than the cold energy requirement. If the heat supply open loop <NUM> is not the only driver for power generation, this loop <NUM> is inactive under thermal-load-following control strategy. Stage LP <NUM>, <NUM> is involved and the bypass of stage HP <NUM>, <NUM> is activated to skip the superheater <NUM> and turbine HP <NUM>. The cryogen is consecutively pressurized in the motor-pump <NUM>, gasified in the evaporator <NUM>, expanded in the turbine LP <NUM>, reheated in first cold recuperator <NUM> and then exhausted. The generator coupled to turbine LP <NUM> delivers power output that covers a part-load of the electricity requirement. Since the recovery and use of the cold energy from the exit of stage LP <NUM>, <NUM> is particularly suitable under thermal-load-following control strategy, the cold recuperator <NUM> is activated to reduce the cryogen consumption and operational costs. In the cooling unit heat first transfer loop <NUM>, all the required cold energy for the cooling load is received from both the gasification process at the evaporator <NUM> and the exit of stage LP <NUM>, <NUM> via the first cold recuperator <NUM>; the chiller <NUM> and its related heat rejection process (i.e. cooling system second heat transfer loop <NUM>) are inactive.

<FIG> depicts the exemplary single stage system <NUM> of <FIG> configured as a hybrid cryogenic energy system <NUM> where the chiller <NUM> of the conventional cooling system <NUM> is bypassed. The hybrid cryo-cogenerator <NUM> is a multi-energy vector. Under hybrid operation, the cryo-cogenerator <NUM> is coupled with an external fuel-based power generation process or other process <NUM> that supplies hot fluid to the system <NUM> via the heat supply open loop <NUM>. The ambient air intake <NUM> is inactive and the involved hot fluid from the external process <NUM> passes from the active line <NUM> to the heat supply open loop <NUM> to provide heat flux at high temperature to the cryogenic open loop <NUM>. The cryogen <NUM> is consecutively pressurized in the motor-pump <NUM>, gasified in the evaporator <NUM> and the optional superheater <NUM>, expanded in the turbine <NUM>, reheated in the first cold recuperator <NUM> and then exhausted. The generator coupled to the turbine <NUM> delivers power output that covers a part-load of the electricity requirement of the indoor environment <NUM>. The high-temperature heat supply from the external process <NUM> is able to increase the turbine inlet temperature, which results in a high performance of the hybrid cryo-cogenerator <NUM>. Cold energy recuperation is applicable if the turbine inlet temperature and accordingly the turbine outlet temperature do not get too high. At a relatively low turbine outlet temperature, the first cold recuperator <NUM> is activated to exploit the cold energy still available at the exit of the turbine <NUM>. In the cooling system first heat transfer loop <NUM>, all the required cold energy for the cooling load is received from both the heat supply open loop <NUM> via the cooler <NUM> and the exit of the turbine <NUM> via the first cold recuperator <NUM>; the chiller and its related heat rejection process (i.e. cooling system second heat transfer loop <NUM>) are inactive.

<FIG> depicts the exemplary single stage system <NUM> of <FIG> configured as a hybrid cryogenic energy system <NUM> that uses both the chiller <NUM> of the conventional cooling system <NUM> and cold energy recuperation from the cryogenic loop <NUM> for cooling the indoor environment <NUM>. The hybrid cryo-cogenerator <NUM> is a multi-energy vector. Under hybrid operation, the cryo-cogenerator <NUM> is coupled with an external fuel-based power generation process or other process <NUM> that supplies hot fluid to the system <NUM> via the heat supply open loop <NUM>. The ambient air intake <NUM> is inactive and the involved hot fluid from the external process <NUM> passes from the active line <NUM> to the heat supply open loop <NUM> to provide heat flux at high temperature to the cryogenic open loop <NUM>. The cryogen <NUM> is consecutively pressurized in the motor-pump <NUM>, gasified in the evaporator <NUM> and the superheater(s) <NUM>, expanded in the turbine <NUM>, reheated in the first cold recuperator <NUM> and then exhausted. The generator coupled to the turbine <NUM> delivers power output that covers a part-load of the electricity requirement of the indoor environment <NUM>. The high-temperature heat supply from the external process <NUM> is able to increase the turbine inlet temperature, which results in a high performance of the hybrid cryo-cogenerator <NUM>. Cold energy recuperation is applicable if the turbine inlet temperature and accordingly the turbine outlet temperature do not get too high. At a relatively low turbine outlet temperature, the first cold recuperator <NUM> is activated to exploit the cold energy still available at the exit of the turbine <NUM>. In the cooling system heat transfer loop <NUM>, the required cold energy for the cooling load is received from the gasification process at the evaporator <NUM>, from the exit of the turbine <NUM> via the first cold recuperator <NUM> and the chiller <NUM> of the conventional cooling system <NUM>. As the chiller <NUM> is used, the heat rejection process (i.e. cooling system second heat transfer loop <NUM>) is active.

<FIG> depicts the exemplary single stage system <NUM> of <FIG> configured as a hybrid cryogenic energy system <NUM> that uses both the chiller <NUM> of the conventional cooling system <NUM> and cold energy recuperation from the cryogenic loop <NUM> for the heat rejection process (i.e. cooling system second heat transfer loop <NUM>). The hybrid cryo-cogenerator <NUM> is a multi-energy vector. Under hybrid operation, the cryo-cogenerator <NUM> is coupled with an external fuel-based power generation process or other process <NUM> that supplies hot fluid to the system <NUM> via the heat supply open loop <NUM>. The ambient air intake <NUM> is inactive and the involved hot fluid from the external process <NUM> passes from the active line <NUM> to the heat supply open loop <NUM> to provide heat flux at high temperature to the cryogenic open loop <NUM>. The cryogen <NUM> is consecutively pressurized in the motor-pump <NUM>, gasified in the evaporator <NUM> and the superheater(s) <NUM>, expanded in the turbine <NUM>, reheated in the second cold recuperator <NUM> and then exhausted. The generator coupled to the turbine <NUM> delivers power output that covers a part-load of the electricity requirement of the indoor environment <NUM>. The high-temperature heat supply from the external process <NUM> is able to increase the turbine inlet temperature, which results in a high performance of the hybrid cryo-cogenerator <NUM>. Cold energy recuperation is applicable if the turbine inlet temperature and accordingly the turbine outlet temperature do not get too high. At a relatively low turbine outlet temperature, the second cold recuperator <NUM> is activated to exploit the cold energy still available at the exit of the turbine <NUM>. In the cooling system heat transfer loop <NUM>, the required cold energy for the cooling load is received from the gasification process at the evaporator <NUM> and the chiller <NUM> of the conventional cooling system <NUM>. As the chiller <NUM> is used, the heat rejection process (i.e. cooling system second heat transfer loop <NUM>) is active. In the cooling system second heat transfer loop <NUM>, the cold energy recovered from the second cold recuperator <NUM> is used together with the cooling tower <NUM> for the heat rejection process.

To sum up, the cryogenic energy system <NUM> provides combined generation of cooling and power to i) data centre and/or ii) other end-users / indoor environments <NUM> according to various/flexible control modes. The cryogenic energy system <NUM> can operate as a backup power generator (cryo-genset) or during on-grid conditions under either an electrical-load-following control strategy or a thermal-load-following control strategy or other strategies. The cryogenic energy system <NUM> can operate in either a standalone mode or in a hybrid mode with a fuel-based process (e.g. combustion engine process, fuel cell) or other process (e.g. solar, geothermal, etc.) <NUM> coupled <NUM> via the heat supply open loop <NUM>.

The heat supply open loop <NUM> is implemented as a part of the cryogenic energy system <NUM>. It can use the outside ambient air <NUM> as a free and available hot fluid source, is especially suitable for electrical-load-following control strategy, thus enabling use of the cryo-system <NUM> in a standalone configuration as a backup power generator. It can also involve other sources <NUM>, <NUM> of hot fluid instead of ambient air: i) glycol-water mixture or other fluid <NUM>; ii) flue gases <NUM> in the case of hybrid operation with a combustion engine process; iii) exhaust gases and vapour / stack coolant outlet / surplus fuel return <NUM> in the case of hybrid operation with a fuel cell process.

The heat supply open loop <NUM> can be used as the only driver of the gasification and power generation processes in the cryogenic open loop <NUM>, under the different control strategies. In this case, the heat supply open loop <NUM> serves as an intermediate heat transfer open loop between the cryogenic open loop <NUM> and the conventional cooling system <NUM> : it is directly or indirectly connected to the cryogenic open loop <NUM> through the heat exchanger(s) of the transfer-expansion stage(s) (evaporator <NUM> and optional superheater <NUM> in case of single stage system / evaporator, optional superheater <NUM> and reheater(s) <NUM> in case of multistage system) and connected to the conventional cooling system <NUM> through one heat exchanger (cooler <NUM>).

In case of an important thermal load (e.g. waste heat from server racks in a data centre <NUM>), the removed heat can be used together with the outside ambient air <NUM> as dual hot sources for the cryo-cogenerator <NUM>. It can be subject to direct or indirect heat transfer to the cryogenic open loop <NUM>. In particular, if backup power is not a requirement, the heat supply open loop <NUM> is inactive when the standalone cryo-cogenerator <NUM> operates under thermal-load-following control strategy.

The cryogenic open loop <NUM> can have a multistage layout (<NUM> stages or more) as shown in <FIG> that offers various/flexible configurations, i.e., all the transfer-expansion stages can operate in series (nominal operation) while assuring the redundancy of each other (as each stage can also operate independently).

The cryogenic energy system <NUM> can include an optional topping closed cycle as shown in <FIG> using another cryogen for power generation, making the system <NUM> a parallel or serial-parallel cryogenic cascade (e.g. nitrogen-based bottoming open cycle + argon-based topping closed cycle; hydrogen-based bottoming open cycle + nitrogen-based topping closed cycle; hydrogen-based bottoming open cycle + argon-based topping closed cycle; nitrogen-based bottoming open cycle + hydrocarbon-based topping closed cycle; hydrogen-based bottoming open cycle + hydrocarbon-based topping closed cycle).

Optional additive fluid (at desired conditions) <NUM>, <NUM> can be injected to the cryogenic open loop and mix with the cryogen at the entrance of the turbine(s) <NUM>, <NUM>. The use of this additive (e.g. helium, hydrogen or any other suitable additive) <NUM>, <NUM> is able to increase the enthalpy drop within the turbine(s) <NUM>, 410and thus reduce the cryogen <NUM> consumption. This option can be used as a trade-off between the total storage volume for cryogen <NUM> (land space) and the operational cost.

In implementations of the cryogenic energy system <NUM> when the heat supply open loop <NUM> is the only driver used for power generation (e.g. as shown in <FIG>, <FIG>, <FIG>, <FIG> and <FIG>), the cooler <NUM> (heat exchanger connected to the heat supply open loop <NUM>) and one optional cold recuperator <NUM> (heat exchanger connected to the exit of the last turbine <NUM> or <NUM> in the cryogenic open loop <NUM>) are in series in the conventional heat transfer loop <NUM> in connection with the cooling unit(s) <NUM> (e.g. water loop) i) to by-pass the main cooling facility <NUM> (e.g. the chiller(s)) or ii) to share the cooling load with the main cooling facility <NUM> (i.e. the two heat exchangers <NUM>, <NUM> and the main cooling facility <NUM> are in series).

In implementations of the cryogenic energy system <NUM> when the heat supply open loop <NUM> is not the only driver used for power generation (e.g. as shown in <FIG>, <FIG>, <FIG>, <FIG>, <FIG>, <FIG> and <FIG>), in the conventional heat transfer loop <NUM> in connection with the cooling unit(s) <NUM>, one optional cold recuperator <NUM> (comprising a heat exchanger connected to the exit of the last turbine <NUM> or <NUM> in the cryogenic open loop <NUM>) is either in series directly with the evaporator <NUM> (heat exchanger part of the cryogenic open loop <NUM>) or in series with an intermediate heat exchanger <NUM> of the intermediate heat transfer loop <NUM> or a topping cycle heat exchanger <NUM> of the topping closed cycle (e.g. as shown in <FIG>). These two heat exchangers <NUM>, <NUM> in a serial arrangement can either i) by-pass the main cooling facility <NUM> (e.g. the chiller(s)) or ii) share the cooling load with the main cooling facility <NUM> (i.e. the two heat exchangers <NUM>, <NUM> and the main cooling facility <NUM> are in series).

In some embodiments (additional functionality), the cryogenic energy system <NUM> may comprise one second optional cold recuperator <NUM> (heat exchanger connected to the exit of the last turbine <NUM> or <NUM> in the cryogenic open loop <NUM>) that can fully or partially support the heat rejection process when the chiller(s) <NUM> is operating together with cryo-cogenerator <NUM> (i.e. the cold recuperator <NUM> can either by-pass or share the load with the cooling tower(s) <NUM>).

The flux exhausting <NUM> from the last cryogenic turbine <NUM> or <NUM> can be exploited according to different modes, either as a hot flux that serves to preheat and gasify the cryogen <NUM> within the cryogenic loop <NUM> at the preheater <NUM> or as a cold flux that serves to support a cooling part-load at one or more cold recuperators <NUM>, <NUM>.

When the cryo-cogenerator <NUM> operates in standalone mode, the preheating process (i.e. recovery of heat from the exit of the last cryogenic turbine <NUM> or <NUM> to preheat the cryogen <NUM> via a preheater <NUM> located in the cryogenic loop <NUM>) is particularly suitable under electrical-load-following control strategy to reduce the cryogen <NUM> consumption and operational costs (e.g. when backup power is needed).

When the cryo-cogenerator <NUM> operates in standalone mode, cold energy recuperation (i.e. recovery and use of the cold energy from the exit of the last cryogenic turbine <NUM> or <NUM> (or from the preheater <NUM>) via a cold recuperator <NUM> located in the cooling unit(s) heat transfer loop <NUM>) is particularly suitable under thermal-load-following control strategy to reduce the cryogen <NUM> consumption and operational costs (e.g. when backup power is not a requirement). Under hybrid operation, cold energy recuperation can be suitable under the different control strategies even when backup power is required.

Under hybrid operation mode, the cryo-cogenerator <NUM> is coupled <NUM> with a fuel-based power generation process (e.g. internal combustion engine, fuel cell) or other process <NUM> via the heat supply open loop <NUM>. The air intake <NUM> is inactive and the involved hot fluid <NUM> (e.g. exhaust gases and vapour, fuel, refrigerant) passes through the heat supply open loop <NUM> to provide heat flux at high temperature to the cryogenic open loop <NUM>, thus increasing the turbine inlet temperature in each expansion stage. This enables reduction of the specific consumption of cryogen <NUM> compared to the standalone cryo-system <NUM>. For certain involved hot fluids <NUM> such as stack coolant or surplus fuel from a fuel cell process, the fluid <NUM> is not discharged at the exit of the heat supply open loop <NUM> but is subject to recirculation (not shown).

Under hybrid operation mode, the cryo-cogenerator <NUM> is multi-functional and multi-controllable. It can be used as a backup power generator when the cryo-system <NUM> operates under thermal-load-following control strategy or other particular control strategies. For high source temperatures, the operating conditions and accordingly the turbine(s) <NUM>, <NUM> inlet temperature(s) can be varied according to the needs (e.g. operational cost, emission level limit, etc.). From certain high turbine inlet temperatures, the cold energy recuperation at the exit of the last cryogenic turbine <NUM> or <NUM> is no longer applicable and the resulting regime of the cryo-system <NUM> can no more fully support the required thermal load. In this case, the conventional chiller(s) <NUM> is/are supplied by the hybrid cryo-cogenerator <NUM> to add cold energy.

Advantages of the cryogenic energy system <NUM> include the following:.

The cryogenic energy system <NUM> described in the various embodiments above is a novel zero-emission polygeneration alternative that can be proposed to various electricity and cold energy consumers. It can serve as a cryo-genset (backup power generator) in replacement of the traditional polluting and noisy diesel genset. Besides, the use of the cryo-system <NUM> during particular on-grid conditions (e.g. grid peak demand, high electricity price) could be considered as an energy saving strategy for certain consumers, such as data centres located in hot and humid climates (e.g. tropical climates) or in air-polluted regions where airside free cooling is not favourable. Besides data centres, the cryogenic energy system <NUM> could be applicable in building cooling, refrigerated warehouses and any other cooling process where the use of chillers, air coolers or equivalent facilities are required.

The cryogenic energy system <NUM> draws heavily on established components from the power generation and industrial gas sectors. This provides a shorter system validation and lower technology risk than most new technologies being introduced in the clean tech and data centre space. The integration and retrofitting of the cryogenic energy system with existing conventional cooling systems can thus be performed on a very large scale.

Claim 1:
A cryogenic energy system (<NUM>) for cooling and powering an indoor environment (<NUM>), the system (<NUM>) comprising:
a cryogenic open loop (<NUM>) comprising a cryogen source to supply a cryogen (<NUM>) and at least one transfer-expansion stage in fluid connection with the cryogen source, each transfer-expansion stage comprising at least one heat exchanger for heat transfer therein from a hot fluid (<NUM>) to the cryogen (<NUM>) and a power unit (<NUM>), for expansion therein of the cryogen (<NUM>) that has been heated in the at least one heat exchanger to generate electricity, the at least one heat exchanger including an evaporator (<NUM>); and
a heat supply open loop (<NUM>) configured to provide the hot fluid (<NUM>) for heat exchange with the cryogen (<NUM>) in the at least one heat exchanger, the heat supply open loop (<NUM>) comprising an exit (<NUM>) for the hot fluid (<NUM>) that has been cooled by the cryogen (<NUM>) in the at least one heat exchanger;
the cryogenic energy system (<NUM>) configured to perform heat removal from a first heat transfer loop (<NUM>) of a conventional cooling system (<NUM>) of the indoor environment (<NUM>) for at least partially cooling the indoor environment (<NUM>), the first heat transfer loop (<NUM>) transferring heat obtained from air in the indoor environment (<NUM>), wherein the heat removal comprises one of:
heat transfer from the first heat transfer loop (<NUM>) to the cryogen (<NUM>) in the evaporator (<NUM>); and
heat transfer from the first heat transfer loop (<NUM>) to the hot fluid (<NUM>) in the heat supply open loop (<NUM>) that has been cooled by the cryogen (<NUM>) in the evaporator (<NUM>).