Emission Class

Description: class of generator emission (e.g. NoX, SoX, CO2, etc.)
Detail:

See also Emission Property Reference for a detailed list of properties for this class of object.

Introduction

Various activities including the generation of electricity by fossil-fired plant produces a range of combustion by-products such as NOx (NO and NO2), SOx (SO and SO2) and CO2:

  • A database may include production details, constraints, and taxes on any number of emissions.
  • Emissions can be produced, absorbed (scrubbed), constrained, and penalized across all or any subset of generators and/or fuels.
  • Constraints can be placed on the total of any emission and/or on a subset of producers across any time period including multi-annual constraints.
  • There is no limit to the number of emission limits modeled.
  • Emission grandfather rights can be modeled.

Units of Emission

There is no assumed unit of emission in the simulator, however, the display of units of emission production and other input and output parameters can be set in the Units of Data settings. When specifying the rate of emission production, the "unit of emission" is used, and when reporting emissions in summary (daily, weekly, etc) the "1000 emission units" is used in display. Note that if the unit of emission is pound (lb), the "1000 emission units" setting should be "000's lb" (or equivalent), not short or long tons (since a short ton is 2000 lb, and a long ton is 2240 lb). Alternatively, the production rates can be manipulated so that when multiplied by 1000, the total production is in equivalent tons i.e. by dividing the production rates by 2, so that summary emission data are shown in short tons.

Emission Production

Emissions are associated with Generation by adding Generator objects to the Emission Generators collection and/or Fuel Offtake by the Emission Fuels collections and the following properties:

Emissions associated with Generator Units Started are modeled with the Emission Generators Production at Start property.

The emissions associated with a specific Fuel and Generator can be scaled using the Generator Fuels Emission Scalar property. See that topic for more details.

The sales and purchases into markets e.g. energy markets can contribute to or abate emissions if you define either the Emission Markets Sales Coefficient or Purchases Coefficient.

Abatement

The abatement of emissions is modelled either:

Abatement objects provide detailed modelling of the physical and cost aspects of abatement technologies as well as allowing the simulator to optimize the choice of technologies employed from a set of defined alternatives.

Incremental Cost

The incremental cost of emissions on Generation is a function of the Shadow Price and defined production rates net of any removal rate or other scaling. This incremental cost is reported as Generators Incremental Cost and forms part of the SRMC. This dispatch effect of emissions can be adjusted with the Generators Shadow Price Scalar property.

Constraints

Basic constraint on the total Production can be entered with the property Max Production which has variants for day, week, month and year types.

More complex emission constraints are created using Constraint objects. To define a constraint on:

In the latter case the simulator uses the list of generators included in the constraints as a filter, so only the emissions of those generators are counted in the constraint (otherwise the constraint would include all emissions). This second method also ensures that only the emission included in the constraint is only one constrained (otherwise it would include all emission types produced by the generators).

The Constraint class provides interval, day, week, month and year period types and also Custom period type, which allows you to create a single constraint that spans any time period whatsoever e.g. you might have a limit on the total emissions of a Generator or group of Generators across several years. Such multi-annual constraints are best handled by LT Plan which can be used to decompose very long-term constraints into equivalent annual limits for MT Schedule.

Because these emission constraints are fully integrated into the mathematical programming problem, the dispatch and pricing outcome will reflect the economic impact of the constraints. This means that, when an emission constraint is binding, lower emitting plant will be favoured over high emission plant, thus the merit-order of generators will change. However generators in many schemes that implement the Kyoto protocol incumbent generating companies are given grandfather rights to emit. This allocation of rights can be modeled using the Company Emissions property. These allocations pass back to the company and affect Net Profit. When running models this will result in generator bidding behaviour reflective of the net position with respect to emissions e.g. a high emitter may retain its place in the merit order if its allocation of emission right is high enough.

Emission Taxes/Prices

In addition to or instead of modelling physical emission limits, emission taxes/prices can be modeled either by:

Price is treated as the 'accounting price' for emissions. This is the price used to compute cost assigned to generators for their emissions, but it is distinct from the Shadow Price which is the 'dispatch price' meaning that this is the price used to adjust generator offer prices to account for emissions. The following table describes the effect of setting either or both of these properties:

Emission Price Emission Shadow Price Emission Constraints Emission dispatch Emission accounting
Emission.Price
Emission.Shadow Price Emission.Shadow Price
Emission.Shadow Price Emission.Price
Constraint shadow price Emission Price
Constraint shadow price Constraint shadow price + Emission Shadow Price
Constraint shadow price Emission Price
Constraint shadow price Constraint shadow price

Auxiliary Use and Loss Factors

It is important that your emission constraints, production rates, and shadow prices are consistent with your model's assumptions about auxiliary use.

The following note applies if you define either generator auxiliaries, or use Marginal Loss Factor at the generator level, and use the default settings of Load Metering Point, which is that generator offer quantities are generator-terminal, but offer prices are sent-out. For example, the Australian NEM uses generator-terminal loads for dispatch, and thus there is an implicit assumption in the load data about how much generator auxiliaries are included. This has an important impact on emissions modelling because emission constraints are imposed in the optimization on gross (generator-terminal) generation and fuel use, but generator offer prices are calculated on a net (sent-out) basis.

In the case where you input the Shadow Price of the emission then the simulator can correctly computes the effect of that shadow price on the sent-out generator offer prices. Thus in this case the system energy price will correctly reflect the marginal cost of emissions.

However, in the case where you input a quantity constraint on emissions, the shadow price on that constraint is not known a priori and thus the simulator cannot pass through the affect of auxiliary losses on to the generator offer prices that is implied by that emission limit. There will therefore be some mismatch between the energy prices and the emission shadow prices (in general the emission price will be overstated, and the energy price understated).

To compensate in this case you could either:

  1. Pre-compute the amount of emissions attributable to auxiliary use, and subtract them from the constraint limit, and then change the coefficients for generator emissions in the constraint to account for this auxiliary loss factor; or
  2. Calculate markups for each generator to reflect the anticipated shadow price of the emission. This adjustment is given by:

? × ei × (1/li - 1)

where:

? is the emission shadow price
ei is the emission production rate of generator i on a per megawatt basis
li is the loss factor of the generator which is the production of Marginal Loss Factor and Aux Incr.