By Lesley Thomson (Civil Engineering) – University of Manchester

Development of a large [1.0-1.5 GW] thermal power station on a new green-field site to replace the generating capacity of several older and smaller electricity generating plants. Located near to or within a major urban area and are to be decommissioned within the next five years.


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Thermal power stations are facilities that produce electric energy from thermal energy released by combustion of a fuel or consumption of a fissionable material. (McGraw-Hill, 2003) The construction of a thermal power station, of any size, will always be a controversial issue. Not only do power generating units require huge capital investment and various natural resources, but their presence both during construction and operation can cause numerous detrimental environmental impacts. The fundamental issue that societies have with thermal power stations is the consumption of the fuel and the subsequent emissions and waste. However, the environment is affected throughout the entire lifecycle of such a project; from the initial design stage, during the construction of the various infrastructures necessary for a thermal power plant, throughout its operation and finally, during decommissioning. This report will look at the key environmental impacts from the three of the four main stages; design, construction and operation.

It is in agreement that the larger the power plant, the greater the risk of environment deterioration. As such, the construction of power stations with a capacity of 50 MW or more, as in this case, requires consent from the Secretary of State for Trade and Industry.(Agency, 2001) Once approved, plans for new thermal power stations are often met with bad press from the public, so the positive impacts should not be overlooked in the full environmental investigation. Ultimately, the end result of all projects is to benefit society. Therefore, the positive and negative impacts that arise in each of the stages should be critically assessed, and how they affect the environment around the project and elsewhere in the system, so a round judgement can be made as to whether the project is environmentally viable.

DESIGN STAGE

The design stage does not so much directly affect the environment, but rather it is important with regards to the consideration of the environmental impacts that can result from the other stages of the lifecycle. This section of the report will describe, with examples, how successful design can lead to efficiency, and subsequently, a decrease in negative environmental impact.

The design process of a thermal power plant should use all relevant, current technologies and practices to produce a design that will have the minimal environmental impact both during construction and operation. The environmental consequences of a thermal power plant are both plant and site dependent, and should be designed so accordingly. For example, the design of the infrastructure for this particular power plant on a green-field site will be different to one located on a brown-field site. Green-field site development can be optimised for efficiency, improved maximum output and lowest cost-of-operation as there has been no lasting environmental damage from previous construction. (Vessel, 2013) However, the fact that the site is free from existing damage will also be a constraint as well as an opportunity, as there will be more regulations regarding the land, and this must also be considered during design.

The impetus for the design process should be the anticipated environmental impacts from the later stages such as construction and operation. The design must first conform to the constraints of the brief and environment, and then try reduce the environmental impacts where possible. If they can’t be reduced, consideration and regulation are needed for those that are unavoidable. In order to do this successfully, it is essential that a full environmental analysis is carried out for each stage. In doing this, all the negative impacts and their magnitude are known, reduced where possible, and prepared for.

The design of the new, larger thermal power plant will more efficient than that of the old, smaller electricity generating plants as newer technologies and practices are available. The increased efficiency will provide an overall reduction to the environmental impacts for the same generating capacity once the old plants have been decommissioned. The construction of a new larger power plant, rather than refurbishment of the existing plants, is also an opportunity to use “whole-system” design approaches. This method highlights efficiency as the primary design objective, whilst ensuring the reliability of the plant, minimising costs during the operation and lifecycle. (Vessel, 2013)

The design stage is also an opportunity to discuss and consult the design approaches towards the anticipated negative environmental impacts. “Early consultation with the Environment Agency, and other relevant organisations, will enable the identification of environmental issues and constraints and the avoidance of sensitive areas, thus reducing the need for redesigning and mitigating avoidable impacts at a later stage.” (Agency, 2001)

A final comment is that whilst the design stage is primarily concerned with the consideration of future environmental impacts, extensive geotechnical evaluation and site investigations are essential to successful design, which may cause minor environmental disturbance. For example, sediment loading during the preparation of the site may cause disruption or remove habitats of the surrounding flora and fauna.

To conclude, successful design work, site investigations, scoping and interactions with relevant organisations will lead to a reduction in damages to the environment.

CONSTRUCTION STAGE

The construction stage refers to the building of the infrastructure that forms a thermal power plant. As the design of a plant is both plant and site dependent, so is the constructed infrastructure. However a typical power plant will compromise of the following principle components; facilities for preparing and storing working materials, facilities for burning fuel and generating steam, facilities for generating electricity and available heat, facilities for treating exhaust gases and solid and liquid residues and cooling facilities. (Sciences, n.d.) During the construction of these facilities, the main environmental categories likely to be impacted are water, land, air and flora and fauna. This section of the report will describe the critical impacts from the construction of the infrastructure with regards to these four categories.

The surrounding water, and elsewhere in the water cycle, is affected by a number of different actions in the construction/commissioning phase. The earthworks and landscaping, and general works next to or near water courses, is one of the critical factors causing the water conditions to change. This is mostly in a detrimental manner that must be accounted for in the design process. It can affect the surface water hydrology and channel morphology by increasing the sedimentation of water courses and changing flow velocities, which results in an increase in flood risk, erosion and subsequent changes in bed and bank stability. The groundwater hydrology is also impacted as a potential reduction in the water table can be predicted, alongside changes to the groundwater distribution and flow. As a result the surface water and groundwater quality is decreased due to pollution from suspended material and disturbance of contaminated soil. This affects the general water course, and places elsewhere in the system. Other factors that affect the water related impacts include use of vehicles and machinery, test abstraction and discharge materials management. These add to the undesirable but mostly unavoidable effects such as increased surface run off from soil compaction, variable flow rates in source and recipient water courses and pollution from leaks and spills of materials respectively. (Agency, 2001)

The surrounding land is another receptor of impact during the construction phase. The particular parts affected can be divided into three subcategories; landscape, soils and geology. Excavations and earthworks impact all three of these through the creation of new landforms, erosion, removal and alteration of soil, and removal of rock by excavation. Not all of those impacts resulting from excavations and earthworks are negative impacts. For example, if the removal of soil is regarding that which is contaminated, this results in the improvement of the development potential of the site. Another factor worth noting is that the use of vehicles and machinery can cause impaction, erosion and contamination to the soil, and this should be minimised wherever possible. (Agency, 2001) A final comment is that the surrounding landscape is also impacted by the construction of the roads needed for the transportation of materials, machinery and labour.

The air quality is another key environmental concern during construction. The local air quality is impacted by the use of vehicles and machinery, which results in emissions from construction site traffic and will generate dust. Detrimental impacts will also arise from the project commissioning leading to elevated levels of harmful exhaust gas emission such as SO­x, NOx and CO2. The release of CO2 will cause a subsequent impact to the atmospheric cycle and detriment the regional/global air quality by contributing to the greenhouse effect, which is met with vast social adversity, as it is a leading world problem. (Agency, 2001) Ultimately, the impact on air quality from construction will be similar to that of most large-scale structures; it is the waste emissions during the operation stage that cause the biggest controversy.

A final topic that encounters great social hostility is the impact of construction on the surrounding flora and fauna; particularly when concerning a green-field site as the local habitats have not been previously disrupted. The aquatic and terrestrial ecology are impacted through a number of actions during construction such as installation of abstraction and discharge equipment, drainage works and use of vehicles, materials management, and earthworks and excavations. The critical impact during construction is the degradation of habitats. This can be a result of removal or disruption through changes to the landscape of noise generation, increased sediment loading or streams or the potential risk of spills or leaks from materials. (Agency, 2001) The removal and disruption of pre-existing natural habitats is a critical impact to attempt to minimise in the design and construction stages.

The construction stage imposes many environmental impacts in the form of both negative and positive. However most are unavoidable and are not specific to thermal power plant construction, but would arise from many types of structures being built on a green-field site.

OPERATION STAGE (first 20+ years)

There are masses of environmental objections to the development of a thermal power plant. Unlike other structures, the operation of a thermal power plant produces environmentally harmful emissions as a result of the energy production through consumption of a form of fuel, as well as the negative impacts from ‘everyday’ operational use of the infrastructure. Therefore the environmental assessment of the operation stage is very important with regards to the full investigation as to whether the project is environmentally viable. Like the construction stage, the critical impacts are going to be described for the same four main categories; water, land, air, and flora and fauna.

One of the main environmental impacts with regards to the water at the site, and elsewhere in the water cycle, is the resulting effect from the process discharge. Changes are observed in the temperatures between recipient and cooling waters for both the surface water hydrology and quality. This has a subsequent impact on the local water chemistry due to the temperature changes and contaminants in discharges. The result of site drainage is also a very influential factor causing many activities and impacts. These include an increase in surface runoff from soil compaction, rapid transfer of rainwater to water courses via drains, changes to flow and deposition regimes in the downstream water course, possible pollution from contaminated run-off and increased flood risk. (Agency, 2001)

The critical environmental impact with respect to the land is the visual impact, especially to a green-field site. Thermal power plants are not considered elegant or visually stimulating designs by most and therefore the development on a site without previous construction is usually met with opposition from local communities.

The impact of operation on the local and subsequent regional/global air quality is arguably the biggest detrimental effect that a thermal power plant has on the environment as it is specific to this type of structure.  The particulate and noxious gas emissions from thermal power plants primarily and directly pollute the air. (Sciences, n.d.) The combustion emissions are dependent on the type fuel, but can release harmful pollutants such as particulates, heavy metals, SOX, NOX, CO2­, PM10 and other gases. Any form of polluting emissions into the atmosphere are considered a negative environmental impact, however the presence of CO2 is particularly critical. It contributes both to the greenhouse effect and the formation of acid rain, and should be critically controlled at all times.

Finally, the impact upon the flora and fauna should be considered as the waste from a thermal power plant is usually toxic. Abstraction and discharge may cause potential entrapment, or alteration of habitats through changed temperature or water chemistry. Another cause for environmental concern is that the waste disposal activities may affect local habitats and species through disturbance due to noise pollution, and pollution as a result of toxic harmful waste, such as exhaust gas. (Agency, 2001)

Most of these impacts are unavoidable resultants of thermal power production, however they should be minimised and controlled to avoid unexpected environmental deterioration.

By Lesley Thomson – University of Manchester


Agency, E., 2001. Scoping the Environmental Impacts of Thermal Power Sations (non-nuclear) , s.l.: s.n.

McGraw-Hill, 2003. McGraw-Hill Dictionary of Scientific and Technical Terms. 6th ed. s.l.:McGraw-Hill Companies, Inc.

Sciences, C. F. E., n.d. 41. Thermal Power Stations. [Online]
Available at: http://ces.iisc.ernet.in/energy/HC270799/HDL/ENV/enven/vol220.htm
[Accessed 1 November 2013].

Vessel, R., 2013. Utilities Can Improve Power Plant Efficiency and become Emission-Compliant in the short term, s.l.: Power Engineering.

The content of articles and other projects is for informational purposes only and does not constitute professional advice.