Case Studies of Environmental Impact Assessment:
Air Quality Issues

To provide practical guidance and document environmental impact assessment practice in the domain of air quality, AIR-EIA provides a collection of typical case studies in common, standardised framework for better comparability.

EIA Case study: TPS Donaustadt: district heating

Category: Thermal Power Station

Summary:

The impact assessment was developed for the new (planned) 350 MW gas fired plant (gas/steam turbine) which will supply up to 250 MW of district heat.

With an efficiency of up to 86% (power and heating combined), it will be one of the most modern and efficient plants in operation: older power plants reach an efficiency of around 40%.

The new block 3 of the Donaustadt TPS complements the existing blocks in Vienna's three major power stations, including Simmering (5 blocks with a total of 1050 MW electrical, and heat capacity of up to 630 MW) and the TPS Leopoldau with 155 MW electrical and 170 MW thermal.

Legislative framework

BGBl. 1995/679

Bundesgesetz über die Prüfung der Umweltverträglichkeit und die Bürgerbeteiligung (Umweltverträglichkeitsprüfungsgesetz - UVP-G)

Key features:

The technical planning data for the new, third block for Donaustadt (current capacity in blocks 1 and 2 is 304 MW electrical) are as follows:

Gas turbine	electrical output	heat output	efficiency (without heat coupling)	efficiency (with heat heat coupling)
240 MW	350/300 MW	0/250 MW	58 %	86 %

The building and emission data base covers more than 7,000 blocks, and includes data for SO2, NOx, CO2, CO, PM10, heavy metals (lead and cadmium), and HCH0 and PAH. Residential and commercial use, heating systems (individual or central) and fuel types (solid (coal), liquid (oil) and gas), all expressed as fractions of the total energy consumption, are recorded for each building.

Problems encountered:

Very restricyed access to the available data and study results; since the assessment is closed, no more public access to the relevant docuemtnts is being granted.

EIA study results:

The main issues was to demonstrate the effects of

• an additional stack and emissions from the new power plant block;
• the reduced emissions from the building blocks now connected to the district heating scheme.

1. simulation of the status quo;
2. simulation of the new TPS design;
3. simulation of the reduced block emissions;
4. impact analysis or building of the deltas: 1 + 2 -3

Modeling approach:

To support the sudy, a special application of the AirWare air quality assessment and management information system was configured. It includes the following major modules and functions:

A building heating data base that manages the energy and emission data for individual buildings or blocks of buildings. The data include basic information on the building or block of buildings, energy data, and heating system (fuel and type) specific emission rates for a group of substances.
A scenario editor that supports the selection of a long-term meteorological (frequency distributions) scenario; a building block selection. The selection of buildings (that will or will not contribute to the emission scenario) can be based on their attributes, using a multi-criteria filtering and ranking approach, or manually, from the map display. Selecting a building represents its connection to the district heating system, and thus switching off its individual emissions. A special case it the automatic multi-criteria selection (up to the available heating capacity provided by an appropriate power plant or set of plants) of buildings, sorted by user defined selection criteria, including proximity to an existing or planned pipeline system.
The basic simulation module; this involves the simulation of a base line scenario (no buildings connected), the selected scenario (some buildings connected to the power plant), and the simulation of the power plant itself. The emission and dispersion simulation is based on a Gaussian long-term model (ISC-3/AERMOD with complex topography corrections), and a long-term weather scenario (frequency distributions) for the default period of October 1 to March 31 (compatible with 96/62/EC and COM(97)500).
An assessment module, that compares the two scenarios, with and without the district heating scheme, and calculates the resulting difference in terms of ambient air quality and population exposure.

Conclusions

All scenarios show a marked improvement of the overall air quality due to the substitution of local household emission (emitted at a low height) with the district heat supplied by the TPS. Depending on the weather situation, the improvement is largely local, that is at and around the areas connected to the district heating supply, but it is big enough to influence the overall immission situation (global average and maximum concentrations observed).

The additional emission introduced by the TPS are negligible in comparison, due to both:

• the much higher efficiency of the new plant;
• the high stack and its location.