Co-product

The production of a co-product from a module specified by entering the percentage fraction of the total energy input recovered from each process in a module. One co- product can be produced from each module and each process may produce different fractions. To use this feature, check the Co-product box on the Module Properties screen and select a fuel in the Co-product field. The co-product fuel must not be listed as an output fuel so it cannot be used to meet export targets, nor can additional "gap-filling" imports be specified to make up any shortfalls. Surpluses of co-product fuels are assumed to be wasted.

When a co-product fuel is defined, an additional data entry table appears in which you can enter the percentage of the energy in the input fuel which can be recovered as the co- product. Different values can be entered for each process, but the values must be less than 100% minus the percentage energy efficiency of each process.

11.3.16 Feedstock Fuels

Processes can have any number of feedstock fuels. Feedstocks are the fuels converted within the process itself, such that the efficiency of a process is defined as the ratio of the total energy content of all output fuels produced by the process divided by the total energy content of all feedstock fuels consumed. For each feedstock fuel, its fuel share is the percentage share of energy input it provides to its parent process. Typically, most process will have only one feedstock fuel, and hence the fuel share should be set to 100% in Current Accounts. Note that feedstock fuels are distinct from auxiliary fuels. Feedstocks are the fuels converted within the process, while auxiliary fuels are specified as energy consumed per unit of energy consumed or produced in a process. Auxiliary fuels reflect subsidiary fuel consumption in a process. They are NOT converted in a process, and hence their energy content is not included in how the overall energy efficiency of the process is calculated.

For each feedstock fuel you can also specify environmental effects, by creating a link on the Environment tab to a technology listed in the TED database.

calculated. Auxiliary fuels are a useful of way of representing subsidiary or own-use energy consumption in a Transformation process, such as electricity used in an oil refinery or own-use of electricity in a power plant.

For each auxiliary fuel you can also specify environmental effects, by creating a link on the Environment tab to a technology listed in the TED database.

11.4 Outputs

Use the Output Fuels Properties screen to set the basic properties of each fuel produced by a module. There are no particular limits on the number of output fuels from each module. Notice though that all processes in a module produce the same set of output fuels, and each process produces those fuels in the same proportions.

11.4.1.1 Fuel

Select a fuel produced by the module from the fuels pull down menu. Fuels correspond to the ones listed in the Fuels Screen.

11.4.1.2 Production Priority

When a module has more than one output fuel, and if the module Dispatch Rule is not set to Run to Full Capacity, then one or more of the output fuels can be selected as a priority fuel. Processes will then be dispatched to meet the sum of domestic requirements + export targets - minimum imports for only the priority output fuels. Non-priority fuels are regarded as by-products of a module. That is, they are produced according to the Output Shares you enter, but processes are not dispatched specifically to meet their requirements.

If a module has only one output, or if the module dispatch rule is set to Run to Full Capacity, the Priority Fuel field will not be displayed. Also, if you set the Output Shares option to Proportional to Requirements (by leaving the box empty on the Optional Data Screen in the Module Properties Wizard), then priority fuels again need not be specified, since outputs will be produced in the same proportions as the module fuel requirements.

Consider the following example of a refinery producing 1200 units of three fuels: kerosene, gasoline and fuel oil, of which gasoline and kerosene are priority fuels, and fuel oil is a by-product. In the table shown below, note that the output mix from the refinery does not match the requirements for the fuels produced. The requirements for one of the priority fuels (gasoline) is met exactly, while a surplus of the other (kerosene) is produced. You can specify what happens to this surplus by setting the Surplus field to Export Surplus or Waste (see below). The requirements for fuel oil are not met.

11.4.1.3 Surplus Production

Surplus outputs can either be assigned to exports or can be left unused (wasted). You can use this feature to simulate cases such as the flaring of natural gas where useful energy is not fully utilized. Surpluses can arise either when a module is set to operate at full capacity (regardless of requirements) or when a module has two or more outputs that are priority fuels. In this latter case, a surplus occurs because the output mix from (say) a refinery is likely to be in different proportions than the requirements for the fuels produced. In such cases, the requirements for one of the fuels will be met exactly, and the rest will be met in surplus.

11.4.1.4 Shortfall in Production

Where shortfalls of outputs exist they can either be filled by additional "gap- filling" imports or some requirements will simply remain unmet in the module. The occurrence of shortfalls in a module does not necessarily indicate that overall supply does not meet demand. You may wish to simulate a system of modules in which two or more modules produce the same output fuel. For example, electricity generation may be simulated in both a central generating module and in an isolated or cogeneration module. In these cases, a shortfall in the first module may be filled by the output from the second module.