Energy System Features: Environmental & Economic Impacts
Environmental Impacts of Energy Systems
1 Chemical Contamination
Physico-chemical pollution associated with energy production stems mainly from the combustion of coal, oil, and gas. We can categorize this pollution based on the type of pollutants produced.
Greenhouse Gases: CO2, CO, and CH4
Certain gases in the atmosphere allow solar radiation to reach Earth but trap some of the reflected radiation, causing a warming effect that can lead to climate change. CO2 is the most significant greenhouse gas, primarily originating from the use of fossil fuels as an energy source. As a product of combustion, it’s always present. The most effective way to reduce these emissions is to increase energy efficiency, thereby decreasing emissions per unit of energy generated.
Coal emits the highest amount of CO2 per kWh.
- Energy Conversion: 40% (refineries, power plants, and heat)
- Industry: 22%
- Transportation: 20%
- Other: 12% (agricultural, commercial, and residential)
Air Emissions: SO2 and NOx
Produced by the use of fossil fuels, these gases are associated with impurities in the raw material. Electricity generation and heat production for industrial processes account for 90% of these emissions. SO2 causes metal corrosion and respiratory irritation, which can be fatal. SO2 reduction is possible by removing sulfur before or during combustion. High concentrations of NOx produce urban haze or smog, causing breathing problems and eye irritation. Reducing these oxides can be achieved by modifying combustion conditions, such as lowering the temperature. Both oxides are considered contributors to acid rain: they transform into sulfates and nitrates in the upper atmosphere, react with water to form acids, and eventually fall as rain.
Particles
Particulate emissions are associated with combustion. However, using electrostatic precipitators and electrofilters achieves removal efficiencies between 95% and 99%. Particulate emissions remain an environmental problem for developing countries with less stringent environmental legislation. The most dangerous particles, from a health perspective, are between 0.01 and 1 mm in size.
2 Radiological Contamination
Source: Nuclear energy. The amounts of various radioactive contaminants depend on the reactor type, its design, and the specific effluent treatment installed. Coolant contamination occurs through activation. Achieving very low emission levels requires reducing radioactivity in the primary coolant circuit (reactor) through efficient continuous purification. During normal operation, nuclear plants release small amounts of radionuclides as liquid effluent, vapor, or gases. Radiation damage is associated with two types of effects: stochastic (cancer and genetic errors, with no threshold dose) and non-stochastic (biological changes occurring only above a threshold dose). Reducing radionuclide release requires an adequate effluent treatment system, present in almost all nuclear power plants.
3 Thermal Pollution
Due to steam condensation in electricity generation systems, waste heat is released into the environment. The water used for cooling, when returned to its source, experiences a temperature increase. This increase can be minimized by using closed cooling circuits with cooling towers.
4 Noise Pollution
Only wind and geothermal energy production are considered significantly noisy.
5 Land Occupation
Hydroelectric plants, while cleaner chemically (no pollutant release), require altering river courses and flooding large areas, impacting existing ecosystems. Mini-hydro plants mitigate this issue by requiring smaller infrastructure. Wind and solar power also require significant land occupation. Wind farms, with numerous turbines, can cause bird deaths and are sometimes considered aesthetically unappealing. Nuclear, fossil fuel (coal, fuel oil, and gas), and geothermal plants have a moderate land occupation, while other energy sources have the least impact.
Economic Aspects of Energy Production
Cost and Types
A product’s cost is the sum of expenses incurred during production. For power plants, the product is the electrical energy supplied to the grid (kWh). Internal costs relate to economic costs directly associated with the production process:
- Depreciation costs of investment: Fixed annually.
- Fuel costs: Variable.
- Operation and maintenance (O&M) costs: Fixed (staff) and variable (lubricants, waste management, etc.).
Internal cost analysis typically excludes transmission and distribution costs, energy losses in the network, and taxes, focusing on the cost of energy (kWh) at the point of exit from the power plant. External costs relate to the social cost of environmental impacts caused by emissions and waste, often passed on as eco-taxes.
Specific Investment Cost of an Installation
The cost base of a plant represents its cost if built and paid for instantly, including direct costs (land, civil works, installation, and equipment) and indirect costs (engineering services, inspection, etc.). The total investment cost equals the cost base multiplied by a factor that increases with higher financing costs and longer construction periods. Dividing the total investment cost by the plant’s rated power (e.g., in kWe) gives the cost per unit of installed power, a crucial parameter that varies significantly between plant types.
Specific Fuel Costs
This is calculated by dividing the total annual fuel cost by the annual energy generated. It varies significantly depending on the plant type and size, being negligible for hydroelectric plants, low for nuclear plants, and very high for coal, fuel oil, and gas-fired thermal plants.
Specific O&M Costs
Obtained by dividing the total annual O&M cost (staff and ancillary costs) by the annual energy generated. This cost doesn’t change significantly with plant size or between different plant types.
Total Cost
The total cost of generation is the sum of investment, fuel, and O&M costs.