Availability node

Availability nodes are routing technologies. The aim of incorporating this type of nodes is to reduce the required number of links if you have multiple conversion technologies for a single energy carrier. Consider, e.g., a system in which you have 10 electricity generation technologies having electricity as output. This could be a combination of Source and NetworkNode. You have furthermore 10 technologies requiring electricity as input as combination of NetworkNode and Sink.

If you plan to allow for electricity transfer from all gebeneration to demand nodes, you would require in total $10 \times 10 = 100$ links. If you use the Availability instead, this would reduce to $10 + 10 = 20$ links. significantly reducing the pre-processing requirement. In the latter case, all nodes are connected to the Availability node.

Usage of `Availability`

It is still possible to have direct connection between individual nodes for given resources. This allows, e.g., to investigate the trade-off between off-grid and on-grid electrolysis. In this case, the electrolysis node should not have an input connection with the Availability node, but with the electricity source node. Similarly, the electricity source node should not be connection to the Availability node.

The Links are only transferring a Resource if it is specified as the output of the origin node and the input of the destination node. This implies you can even have multiple connections from a node and avoid transfer via the Availability node. This is especially relevant for retrofit CO₂ capture.

Introduced type and its fields

The GenAvailability node is implemented as a reference node that can be used for an Availability. It includes basic functionalities common to most energy system optimization models.

The fields of a GenAvailability node are given as:

id:
The field id is only used for providing a name to the node.
input::Vector{<:Resource} and output::Vector{<:Resource}:
Both fields describe the input and output Resources as vectors. This approach is different to all other nodes, but simplifies the overall design. It is necessary to specify the same Resources to allow for capacity usage in connected nodes.

Constructor `GenAvailability`

We require at the time being the specification of the fields input and output due to the way we identify the required flow and link variables. In practice, both fields should include the same Resources. To this end, we provide a simplified constructor in which you only have to specify one vector using the function

GenAvailability(id, 𝒫::Vector{<:Resource})

Mathematical description

In the following mathematical equations, we use the name for variables and functions used in the model. Variables are in general represented as

$\texttt{var\_example}[index_1, index_2]$

with square brackets, while functions are represented as

$func\_example(index_1, index_2)$

with paranthesis.

Variables

The variables of Availability nodes include:

Constraints

Availability nodes do not add by default any constraints, except for the constraints introduced in the function create_node(@ref). This constraint is given by:

\[\texttt{flow\_out}[n, t, p] = \texttt{flow\_in}[n, t, p] \qquad \forall p \in inputs(n)\]

This implies that standard availability nodes serve only as energy balance nodes for all other nodes.