Central plant with asset allocator
A central plant includes an asset allocator configured to determine an optimal allocation of energy loads across central plant equipment. The asset allocator identifies sources configured to supply input resources, subplants configured to convert the input resources to output resources, and sinks configured to consume the output resources. The asset allocator generates a cost function and a resource balance constraint. The resource balance constraint requires balance between a total amount of each resource supplied by the sources and the subplants and a total amount of each resource consumed by the subplants and the sinks. The asset allocator determines the optimal allocation of the energy loads across the central plant equipment by optimizing the cost function subject to the resource balance constraint. The asset allocator is configured to control the central plant equipment to achieve the optimal allocation of the energy loads.
1. A central plant configured to serve energy loads of a building or campus,
the central plant comprising:
central plant equipment configured to consume input resources from one or more utilities to produce output resources provided to the building or campus; and
a central plant controller configured to determine an optimal allocation of the energy loads across the central plant equipment by:
identifying one or more sources configured to supply the input resources, one or more subplants configured to convert the input resources to the output resources, and one or more sinks configured to consume the output resources;
generating a cost function comprising a cost of purchasing the input resources from the sources;
generating a resource balance constraint that requires balance between a first amount of each resource and a second amount of each resource, wherein:
the first amount of each resource comprises a sum of a total amount of the resource supplied by the sources and a total amount of the resource supplied by the subplants; and
the second amount of each resource comprises a sum of a total amount of the resource consumed by the subplants and a total amount of the resource consumed by the sinks; and
solving an optimization problem to determine the optimal allocation of the energy loads across the central plant equipment, wherein solving the optimization problem comprises optimizing the cost function subject to the resource balance constraint;
wherein the central plant controller is configured to provide control decisions to a building management system configured to control the central plant equipment to achieve the optimal allocation of the energy loads.
2. The central plant of claim 1 , wherein:
each of the sources represents one of the utilities;
each of the subplants represents a subset of the central plant equipment; and
each of the sinks represents one of the energy loads of the building or campus.
3. The central plant of claim 1 , further comprising storage equipment configured to store and discharge one or more of the resources, the storage equipment comprising at least one of thermal energy storage or electrical energy storage.
4. The central plant of claim 3 , wherein:
the central plant controller is configured to define one or more storage elements configured to store and discharge one or more of the resources; and the resource balance constraint requires balance between:
a total amount of each resource supplied by the sources, supplied by the subplants and discharged by the storage elements; and
a total amount of each resource consumed by the subplants, consumed by the sinks, and charged by the storage elements.
5. The central plant of claim 3 , wherein the central plant controller is configured to add one or more continuous decision variables to the cost function for each resource stored or discharged by each of the storage equipment.
6. The central plant of claim 3 , wherein the central plant controller is configured to:
identify an operational domain for the storage equipment; and
add one or more constraints to the optimization problem, wherein the constraints depend on the identified operational domain and comprise at least one of:
a constraint linking decision variables adjacent in time; and
a constraint linking a state-of-charge of the storage equipment to a charge or discharge rate of the storage equipment.
7. The central plant of claim 1 , wherein the cost function further comprises revenue generated by using the central plant equipment to participate in an incentive program, the revenue subtracting from the cost of purchasing the input resources from the sources.
8. The central plant of claim 1 , wherein the central plant controller is configured to:
generate connections between the sources, subplants, and sinks, the connections defining which of the subplants are capable of receiving the input resources from each of the sources or from other subplants and which of the subplants are capable of providing the output resources to each of the sinks or to other subplants; and
use the connections to generate one or more terms of the resource balance constraint.
9. The central plant of claim 8 , wherein the central plant controller is configured to:
determine at least one of a distribution cost or an efficiency associated with each of the connections, each distribution cost defining a cost of transporting a resource along one of the connections, each efficiency defining a resource loss incurred when transporting a resource along one of the connections; and
modify at least one of the cost function to include the distribution costs or the resource balance constraint to account for the resource losses.
10. The central plant of claim 1 , wherein the central plant controller is configured to add one or more continuous decision variables to the cost function for each resource produced or consumed by each of the identified subplants.
11. The central plant of claim 10 , wherein the central plant controller is configured to:
identify an operational domain for each of the subplants, each operational domain defining a relationship between an amount of each resource consumed by the subplant and an amount of each resource produced by the subplant;
add one or more integer decision variables to the cost function in response to the operational domain having multiple convex regions; and
add constraints linking the continuous decision variables to the integer decision variables to force the central plant controller to choose values of resources consumed and produced that exist only in the operational domain when solving the optimization problem.
12. The central plant of claim 1 , wherein the central plant controller is configured to add one or more decision variables to the cost function for each of the identified sources and each of the identified sinks.
13. A method for optimally allocating energy loads of a building or campus across central plant equipment configured to serve the energy loads, the method comprising:
identifying one or more sources configured to supply input resources, one or more subplants configured to convert the input resources to output resources, and one or more sinks configured to consume the output resources;
generating a cost function comprising a cost of purchasing the input resources from the sources;
generating a resource balance constraint that requires balance between a first amount of each resource and a second amount of each resource, wherein:
the first amount of each resource comprises a sum of a total amount of the resource supplied by the sources and a total amount of the resource supplied by the subplants; and
the second amount of each resource comprises a sum of a total amount of the resource consumed by the subplants and a total amount of the resource consumed by the sinks;
solving an optimization problem to determine an optimal allocation of the energy loads across the central plant equipment, wherein solving the optimization problem comprises optimizing the cost function subject to the resource balance constraint; and
providing control decisions to a building management system configured to control the central plant equipment to achieve the optimal allocation of the energy loads.
14. The method of claim 13 , wherein:
each of the sources represents a utility;
each of the subplants represents a subset of the central plant equipment; and
each of the sinks represents one of the energy loads of the building or campus.
15. The method of claim 13 , further comprising using storage equipment to store and discharge one or more of the resources, the storage equipment comprising at least one of thermal energy storage or electrical energy storage.
16. The method of claim 15 , further comprising defining one or more storage elements configured to store and discharge one or more of the resources;
wherein the resource balance constraint requires balance between:
a total amount of each resource supplied by the sources, supplied by the subplants and discharged by the storage elements; and
a total amount of each resource consumed by the subplants, consumed by the sinks, and charged by the storage elements.
17. The method of claim 13 , wherein the cost function further comprises revenue generated by using the central plant equipment to participate in an incentive program, the revenue subtracting from the cost of purchasing the input resources from the sources.
18. The method of claim 13 , further comprising:
generating connections between the sources, subplants, and sinks, the connections defining which of the subplants are capable of receiving the input resources from each of the sources or from other subplants and which of the subplants are capable of providing the output resources to each of the sinks or to other subplants; and
using the connections to generate one or more terms of the resource balance constraint.
19. The method of claim 18 , further comprising:
determining at least one of a distribution cost or an efficiency associated with each of the connections, each distribution cost defining a cost of transporting a resource along one of the connections, each efficiency defining a resource loss incurred when transporting a resource along one of the connections; and
modifying at least one of the cost function to include the distribution costs or the resource balance constraint to account for the resource losses.
20. The method of claim 13 , further comprising:
identifying an operational domain for each of the subplants, each operational domain defining a relationship between an amount of each resource consumed by the subplant and an amount of each resource produced by the subplant; and
using the operational domains to generate additional constraints on the optimization problem.