Thermal Energy Storage System and Heat Pump Cycles for Industrial Heat Generation

Abstract

Provided herein are methods and systems for generating industrial heat. The methods may comprise storing, by a thermal energy storage system, heat generated by one or more heat pump cycles as thermal energy in a thermal storage assemblage, and generating, by the thermal energy storage system, an output fluid flow of fluid that has absorbed heat from the heated thermal storage system.

1 . An energy arbitrage system connected to an electric grid and configured to generate steam supplied to a facility, the energy arbitrage system comprising:
 a cascading heat pump system configured to generate the steam, wherein:
 the cascading heat pump system is connected and powered by at least the electric grid, 
 the cascading heat pump system comprises a bottom heat pump cycle and a top heat pump cycle coupled by an intermediate heat exchanger configured to transfer heat from a first working fluid in the bottom heat pump cycle to a second working fluid in the top heat pump cycle, 
 the bottom heat pump cycle comprises a first economizer and a bottom-cycle compressor to increase pressure of the first working fluid and to absorb heat from an ambient air source, and 
 the top heat pump cycle comprises a second economizer, a steam generator, and a top-cycle compressor to increase pressure of the second working fluid and to transfer heat to a feed stream comprising water in the steam generator, thereby generating the steam; 
   a boiler configured to generate steam; and   a control system in communication with the cascading heat pump system and with the boiler, wherein:
 the control system comprises a processing device and a computer-readable medium with one or more executable instructions stored thereon, and 
 the processing device is configured to execute one or more instructions to perform operations of (a) receive a steam demand from the facility, (b) generate and send a first set of instructions to the cascading heat pump system to provide for a first portion of the steam demand from the facility, and (c) generate and send a second set of instructions to the boiler to provide for a second portion of the steam demand from the facility. 
   
     
     
         2 . The energy arbitrage system of  claim 1 , wherein:
 the bottom-cycle compressor comprises two bottom-cycle centrifugal compressor stages arranged in series, and   the top-cycle compressor comprises two top-cycle centrifugal compressor stages arranged in series.   
     
     
         3 . The energy arbitrage system of  claim 2 , wherein the second economizer is configured to:
 split the second working fluid into a second primary fluid stream and a second secondary fluid stream,   expand the second secondary fluid stream of the second working fluid to a lower pressure using a first expansion valve of the top heat pump cycle,   absorb heat in the second secondary fluid stream of the second working fluid and   reject heat from the second primary fluid stream of the second working fluid to the second secondary fluid stream of the second working fluid, and   direct the second secondary fluid stream of the second working fluid to an inlet of a second stage of the two top-cycle centrifugal compressor stages.   
     
     
         4 . The energy arbitrage system of  claim 1 , wherein the boiler is selected from the group consisting of a natural gas boiler, a coal boiler, a biomass boiler, a waste-product boiler, and an additional heat pump system. 
     
     
         5 . The energy arbitrage system of  claim 1 , wherein the steam, generated in the steam generator of the cascading heat pump system, has a target steam saturation temperature of at least 120 degrees Celsius. 
     
     
         6 . The energy arbitrage system of  claim 5 , wherein pressure of the feed stream in the steam generator is greater than or equal to pressure of the steam at the target steam saturation temperature. 
     
     
         7 . The energy arbitrage system of  claim 1 , wherein the first economizer is configured to:
 split the first working fluid into a first primary fluid stream and a first secondary fluid stream,   expand the first secondary fluid stream of the first working fluid to a lower pressure via a first expansion valve of the bottom heat pump cycle,   absorb heat in the first secondary fluid stream of the first working fluid, and   reject heat from the first primary fluid stream of the first working fluid to the first secondary fluid stream of the first working fluid.   
     
     
         8 . The energy arbitrage system of  claim 1 , wherein the second portion of the steam demand is generated when the first portion of the steam demand is less than the steam demand. 
     
     
         9 . The energy arbitrage system of  claim 1 , further comprising a renewable energy source, wherein the renewable energy source is connected to the cascading heat pump system and configured to supply electric power to the cascading heat pump system and to provide electricity to an electric grid. 
     
     
         10 . The energy arbitrage system of  claim 9 , wherein the processing device of the processing device is further configured to:
 send instructions to the renewable energy source to supply excess electricity that is not required by the cascading heat pump system to the electric grid, and   send instructions to the cascading heat pump system to draw electricity from the electric grid if the renewable energy source supplies an insufficient amount of electricity.   
     
     
         11 . The energy arbitrage system of  claim 9 , wherein:
 the control system is in further communication with the renewable energy source and configured to control electricity supplied to the cascading heat pump system, and   the processing device is configured to execute the one or more instructions to perform further operations of:
 receiving information associated with an amount of electricity produced by the renewable energy source, and 
 sending instructions to the renewable energy source to supply electricity to the cascading heat pump system. 
   
     
     
         12 . The energy arbitrage system of  claim 1 , further comprising an energy storage system, functionally coupled to and configured to supply power to the cascading heat pump system. 
     
     
         13 . The energy arbitrage system of  claim 12 , wherein the energy storage system is a thermal storage system, operable to store energy as heat. 
     
     
         14 . The energy arbitrage system of  claim 13 , wherein the thermal storage system comprises one or more storage vessels operable to store heated fluid. 
     
     
         15 . The energy arbitrage system of  claim 14 , wherein the heated fluid is steam. 
     
     
         16 . The energy arbitrage system of  claim 15 , wherein the thermal storage is configured to supply the steam directly to one or more of the facility and the thermal storage. 
     
     
         17 . The energy arbitrage system of  claim 12 , wherein the energy storage system comprises one or more batteries operable to supply electricity to the cascading heat pump system. 
     
     
         18 . The energy arbitrage system of  claim 1 , wherein:
 the processing device is further configured to calculate performance of the energy arbitrage system using one or more metrics selected from the group consisting of:
 a heat pump efficiency, defined as steam output divided by electricity input, and 
 a boiler efficiency, defined as the steam output divided by natural gas input; and 
   the processing device is configured to generate the first set of instructions and the second set of instructions based on the one or more metrics.   
     
     
         19 . The energy arbitrage system of  claim 1 , wherein:
 the processing device is configured to further receive one or more inputs selected from the group consisting of a power purchase agreement (PPA) rate, a grid electricity rate structure, and a fuel price; and   the processing device is configured to generate the first set of instructions and the second set of instructions based on the one or more inputs.   
     
     
         20 . The energy arbitrage system of  claim 1 , wherein at least one of the first working fluid or the second working fluid comprises a fluorocarbon, a hydrofluoroolefin, a hydrofluoroether, a hydrocarbon, carbon dioxide, ammonia, or water.