Estimation of Greenhouse Gas Emissions and Reductions of Hydropower Plants for Electricity Production in Iran

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1^th International Conference on Water, Environment and Sustainable Development, 27-29 September, 2016

University of Mohaghegh Ardabili, Ardabil, Iran

Estimation of Greenhouse Gas Emissions and Reductions of Hydropower Plants for Electricity Production in Iran

Shahriar Mehrvand

¹

, Razi Sheikholeslami

²

, Abolfazl Shamsai

³

1- M.Sc., Sharif University of Technology, Tehran, Iran [email protected]

2- PhD student, Global Institute for water security, School of Environment and Sustainability University of Saskatchewan, Saskatoon, Canada

3- Professor, Sharif University of Technology, Tehran, Iran Abstract

Energy consumption in Iran has risen due to the increasing population and economic growth in the last decades. Iran is heavily dependent on fossil fuels and has a large potential of renewable energy sources and hydropower. In this paper we calculate the Greenhouse Gas (GHG) emissions and reductions of hydropower plants in Iran for the year 2015. To calculate the emissions we review the studies in the field and apply the results of World Nuclear Association (WNA) report. To calculate the GHG reduction we use RETScreen software developed by Natural Resources of Canada (NCR). The results indicate that hydropower plants of Iran caused 9977111 tons of equivalent CO2 reduction in 2015. This shows that hydropower plants have important role in reducing air pollution and preventing global warming and should be exploited to its potential capacity.

Keywords: Hydropower plants, Greenhouse Gas, Life Cycle Assessment, Renewable Energy.

1. INTRODUCTION

Many developing nations continue their existence under conditions which have seen little change, and have reaped far fewer beneﬁts from the Industrial Revolution and electriﬁcation than their fully industrialized counterparts. The modern uses of and access to electrical power are key to both the industrialized nation’s ability to further satisfy increasing demand in the production of goods, and the developing nation’s capability to increase its position in the globally-competitive economic marketplace. Thus, for developing countries to succeed, it can be reasonably expected that their rapid economic growth will be accompanied by a commensurate increase in electricity demand. Worldwide, the net consumption of electricity is expected to more than double from its consumption of 14,781 billion kilowatt hours (kWh) in 2003 to 30,116 billion kWh by 2030 [1]. Hydro-electric power, using the potential energy of rivers, is by far the best-established means of electricity generation from renewable sources. It supplies over 16% of world electricity (99% in Norway, 58% in Canada, 55% in Switzerland, 45% in Sweden, 7% in USA, 6% in Australia) from over 1060 GWe installed capacity (2015). Half of this is in five nations: China (212 GWe), Brazil (82.2 GWe), USA (79 GWe), Canada (76.4 GWe), and Russia (46 GWe)¹.

Fuel sources to satisfy production demand for such an increase will be put under intense economic pressure due to increasing extraction and processing costs, expanding global fossil fuel consumption, and environmental considerations [2]. Key to understanding the future role of small hydropower in the global electricity market is an assessment of the effects of an increasing electricity consumption coupled with a decreasing fossil fuel supply.

Any water resources development of which a hydropower scheme may form part has environmental and social impacts, which must be taken into consideration at the initial planning stage. Also, legal and political implications must be carefully considered.

Concerns over environmental issues and future energy security have boosted governments' interests in looking at the potential of renewable energy sources (RES) to meet the rising energy demand. Although RES are generally more expensive than traditional fossil fuels, they are recognized for entailing lower environmental and social impacts (European Commission, 2003, 2005)[3].

1 www.world-nuclear.org

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Non-conventional projects, such as wind, solar, biomass, wave and geothermal power plants are less common. However, large hydropower projects, despite their ability to provide large quantity of electricity with low greenhouse gas emissions, are often criticized for disrupting ecosystems, spoiling landscapes and causing other environmental and social impacts [4]. Anthropogenic greenhouse gas (GHG) emissions are the most signiﬁcant driver of climate change and global warming. CO2 is the primary GHG emitted through human activities and the largest human source of CO2 emissions is from the combustion of fossil fuels. Due to global warming, increase in sea levels, increasing risk of river and coastal ﬂooding, sudden changes in the weather, decrease in crop yields, decrease in hydropower potential, and increase in risk of biodiversity loss and epidemic illnesses occur [5]. Thus it seems necessary to consider environmental issues in developing electricity production plants.

Many authors have studied hydropower plants from environmental aspects. In 1996, Proops et al. examined the UK economy wide, lifecycle implications of eight forms of electricity generations for the emission of three air pollutants, CO2, SO2 and NOx using input-output analysis for life cycle assessment in three phases of generation stations: construction, operation and decommissioning, which are limited to individual energy sources [6]. In 2004, Denholm et al. studied greenhouse gas emissions from utility scale energy storage systems including pumped hydro storage using life cycle assessment and calculated greenhouse gas emission for pumped hydro storage plant [7]. In 2006, Dos Santos et al. conducted an experimental study to measure gross greenhouse gas fluxes from hydropower reservoir and compared it with thermo-power plant.

Hydro-power plants studied in this research generally posted lower emissions than their equivalent thermo- based counterparts, especially those plants with greater power densities (capacity/area flooded – W/m2) [8].

In 2007, Weisser reviewed the results of the past greenhouse gas emission life cycle analysis for electric supply technologies and results indicate that the most signiﬁcant greenhouse gas avoidance can be made from technology substitution. The introduction of advanced fossil fuel technologies can also lead to improvements in life-cycle GHG emissions. Overall, hydro, nuclear and wind energy technologies can produce electricity with the least life-cycle global warming impact [9]. In 2014, Zhang et al. studied feasible potential for hydropower development regarding environmental constraints and transformed environmental effects of the power plants to equivalent CO2 for impacts around the plant and reduced downstream flow for impacts of downstream [10]. In 2015, Zhang et al. proposed a method to calculate the embodied carbon budget for large hydropower plants that takes into account carbon reductions due to the provision of extra services, and carbon emissions due to the decrease in adjacent ecosystem services in addition to traditional accounting system for carbon emission from plant construction [11]. In 2015, Bauer et al. presented a comprehensive greenhouse gas emission calculation for various types of fuels and energy sources using both process chain analysis and Input/Output method for life cycle assessment and suggested an emission range for each one[12].

2.

Environmental impacts inventory of hydropower plants

A small hydro development will impact its environment in various ways; the extent and nature of these impacts will vary depending on the type of development, the species present, and the site. Many of the potential negative impacts can be mitigated through careful planning, construction, and operation of the project.

The most significant environmental impacts of a hydro project are usually associated with the flooding of land to create a reservoir. This can result in the loss of agricultural land, the flooding of dwellings and archeological sites, loss of fish habitat and spawning areas, and drowned forest. In places where the land is acidic rock with soft acidic water, such as the Canadian Shield, the creation of new lakes and reservoirs can permit submerged vegetation to release mercury compounds - dangerous pollutants - into the water. The decomposition of submerged vegetation also releases methane and carbon dioxide, both greenhouse gases.

Clearing the forest in the area to be flooded can partially mitigate these problems.

Fortunately, most small hydro systems are run-of-river plants that do not cause significant flooding; the creation of new reservoirs is rarely financially feasible for projects of this scale. The creation of a head pond or small reservoir meant to smooth flows may cause minor flooding, but this will generally be limited to rapids just upstream of the dam. Sometimes small hydro projects make use of an existing lake or reservoir for water storage. While flooding is avoided, in projects meant to operate primarily during the times of peak electrical load, the water level upstream of the dam and the flow through the tailrace and downstream of the project may fluctuate. In a large storage reservoir, this fluctuation is usually slow, and not a problem.

Downstream of the turbine, these fluctuations may be rapid, and more objectionable.

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Dam or diversion weir construction has negative environmental consequences beyond flooding. The dam presents a barrier to fishes. Fish passages and fish diversion structures are used to address this problem.

Similarly, the dam may be a barrier to navigation in the watercourse, and will affect canoeists and kayakers who use the river for recreational purposes. Sedimentation of the watercourse can occur during construction if the construction is not done with sufficient care. River diversion tends to result in a loss of fish habitat between intake and tailrace, where channels may dry up, although maintaining a reasonable residual flow can mitigate this. Other aesthetic impacts include the presence of the civil structures in the landscape and transmission lines between the project and the load or the existing grid.

The level of environmental impact and impact assessment requirements therefore tend to vary with the type of project, the species presents, and its location. A run-of-river project at an existing dam has very minor impacts. A run-of-river project at an undeveloped site will have impacts associated with the construction of the dam or weir. A water storage project involves a much larger dam, causes flooding, and will be subject to a much more rigorous environmental impact assessment.

The boundaries for estimating the carbon footprint of a product or enterprise include three scopes (on-site direct emission, on-site indirect emission and off-site indirect emission) and four classes for GHG activity, which include energy consumption, material production, service provision and land appropriation. If a product involves one or more of the four activity classes, then it has carbon-related behavior. Products include both goods and services. A complete inventory of carbon budget for a typical large hydropower plant is shown in table 1 [11].

Table 1- inventory of carbon budget for a typical large hydropower plant Main products Carbon related

behavior

By-products Carbon related behavior Water regulation (-) Decrease shadow water

supply projects

Increase soil conservation project

(+)

Increase soil conservation project Flood control (-) Decrease shadow ﬂood

protection projects

Environmental pollution (+)

Increase pollutants treatment project Shipping facilitation (-) Decrease shadow road

Transportation Fish habitat destruction (+)

Increase ﬁsh conservation project Microclimate

regulation (-)

Decrease shadow air-

conditioning projects Human habitat destruction (+)

Increase immigrants relocation project Hydroelectricity

production (+)

Hydropower plant construction & On-site

emissions by ﬂooded vegetation

Reservoir sedimentation (+)

Increase dredging project

Land appropriation (+) Decrease net ecosystem productivity

Life-cycle assessment (LCA), an approach utilizing process chain analysis specific to the types of fuels used in each process, allows for the full accounting of all such emissions, also when they take place outside of the national borders. Thus, LCA considers not only emissions from power plant construction, operation, and decommissioning but also the environmental burdens associated with the entire lifetime of all relevant upstream and downstream processes within the energy chain. This includes exploration, extraction, processing, and transport of the energy carrier, as well as waste treatment and disposal. The direct emissions include releases from the operation of power plants, mines, processing factories, and transport systems. In addition, indirect emissions originating from manufacturing and transport of materials, from energy inputs to all steps of the chain, and from infrastructure are covered [12].

Each GHG has a different, quantitative effectiveness in trapping heat at the earth’s surface; that effectiveness is referred to as the substance’s global warming potential (GWP). In addition, each GHG degrades

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chemically over time in the atmosphere or is gradually absorbed by the ocean or another terrestrial geochemical cycle. Thus, GWP must be defined for a specific point in time after the emission of the GHG, similar to forecasting the economic value of an inventory of perishable goods. For example, during the first year after emission, a ton of CH4 emitted into the atmosphere has 72 times the GWP as a ton of CO2 emitted at the same time, while it has only 21 times the GWP of CO2 over a 100-year period after emission. This is because CH4 cycles out of the atmosphere faster than CO2. Over 500 years, the ratio is 7.6.

Using a chosen time period and the resulting GWP values, it is possible to determine the GWP of a mix of gases emitted by a power plant or its fuel cycle and to convert that total to a so-called CO2 equivalent (CO2eq or CO2e). CO2 equivalent is a measure used to compare the emissions from various greenhouse gases based upon their global warming potential (GWP). CO2 equivalent for a given amount of a gas is derived by multiplying the weight of the gas emitted by that gas’s GWP.

In 2013, the ecoinvent association founded by institutes of the ETH domain and the Swiss federal offices for life cycle assessment. Bauer et al. analyzed two types of hydropower plants (storage and run-of-river) in the ecoinvent LCA database. For the run-of-river power plants, a representative sample of four run-of-river power plants in Switzerland and one in Austria was used. Lifetime was assumed to be 80 years for the fixed structures and 40 years for other parts. Net average efficiency is 82% (best efficiency can be 88%). For the storage plants, a representative sample of 52 Swiss concrete dams with a height of more than 30 m was considered for calculating the average. Lifetime was assumed to be 150 years for the dam, 40 years for the turbines and pipes, and 80 years for the rest of materials. Net average efficiency, including pipe losses, is 78% (best efficiency can be 84%). The data refer to plant construction of a mix of dam types built between 1945 and 1970; therefore, they might not be fully representative for more modern construction or for a specific dam type or for an individual unit. The data have been extrapolated to preliminary describe dams in other alpine and non-alpine countries.

Direct GHG emissions from reservoir lakes due to digestion of biomass depend to a large extent on the surrounding climate and the type of biomass flooded by the lake: while they tend to be small in an alpine and moderate climate, these emissions can be substantial in tropical areas.

According to the study of Bauer et al., for direct GHG emissions from Norwegian and Swedish reservoirs, averaging around 6 g CO2-equiv.kWh-1, were considered, also for all non-alpine regions except Finnish reservoirs, for which 30 g CO2-equiv.kWh-1 were assumed. Direct GHG emissions from tropical reservoir lakes were estimated as roughly 150 g CO2-equiv.kWh-1. The results for cumulative GHG emissions show a range of almost 10 g CO2-equiv.kWh-1 for alpine reservoir plants to160 g CO2-equiv.kWh-1 for tropical hydro reservoirs. In the case of run-of-river, results are of the order of 5 g CO2-equiv.kWh-1.

A recent literature survey conducted by Raadal et al. concluded that the range of life-cycle GHG emissions for reservoir plants is about 5–150 g CO2-equiv.kWh-11 and almost 0–12 g CO2-equiv.kWh-1 for run-of- river plants, the difference depending on the plant and site characteristics (type of dam, height/width of dam, capacity of reservoir, location, installed electric capacity, load factor, and dedicated transmission lines).

However, small hydro may have somewhat higher GHG emission factors.

The equivalent CO2 emission ranges and averages reported by for main recent studies are shown in figure 1.

Figure 1. equivalent CO emission ranges and averages

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In this paper, we use the average CO2 equivalent of 26g presented in WNA report to calculate the total emission of GHG emission by hydropower plants in Iran. Next we calculate the avoided CO2 equivalent emission by hydropower that could be produced by the alternative plant.

3.

Calculating CO2-eq reduction

The software used in this research is RETScreen which is developed by Natural Resources Canada (NRC) in order to build the capacity of planners, decision makers and industry to implement renewable energy and energy efficiency projects. This objective is achieved by: developing decision-making tools (i.e. RETScreen Software) that reduce the cost of pre-feasibility studies; disseminating knowledge to help people make better decisions; and by training people to better analyze the technical and financial viability of possible projects.

RETScreen 4 is an Excel-based clean energy project analysis software tool that helps decision makers quickly and inexpensively determine the technical and financial viability of potential renewable energy, energy efficiency and cogeneration projects¹.

The software, provided free-of-charge, can be used worldwide to evaluate the energy production and savings, costs, emission reductions, financial viability and risk for various types of Renewable-energy and Energy-efficient Technologies (RETs). The software (available in multiple languages) also includes product, project, hydrology and climate databases, a detailed user manual. The program used for hydropower assessment consists of Excel spreadsheets linked to Visual Basic code, and provides an extremely user- friendly interface. Seven project worksheets are used in this model; Energy Model, Hydrology Analysis and Load Calculation, Equipment Data, Cost Analysis, Greenhouse Gas Analysis, Financial Summary, and Sensitivity and Risk Analysis.

As part of the RETScreen Clean Energy Project Analysis Software, an Emission Analysis worksheet is provided to help the user estimate the greenhouse gas emission reduction (mitigation) potential of the proposed project. This Emission reduction analysis worksheet contains five main sections: Settings, Base case electricity system (Baseline), Base case system GHG summary (Baseline), Proposed case system GHG summary (Project) and GHG emission reduction summary. The settings section is used to indicate whether or not the optional Emission Analysis worksheet is used and to select the preferred type of analysis. It also provides GHG global warming potential factors. The Base case electricity system and Base case system GHG summary sections provide a description of the emission profile of the baseline system. The Proposed case system GHG summary section provides a description of the emission profile of the proposed project. The GHG emission reduction summary section provides a summary of the estimated GHG emission reduction based on the data entered by the user in the preceding sections. Results are calculated as equivalent tons of CO2 avoided per annum.

One of the primary benefits of using the RETScreen software is that it facilitates the project evaluation process for decision-makers. The Emission Analysis worksheet, with its emission related input items (e.g.

fuel mix) and its calculated emission factor output items (e.g. GHG emission factor), allows the decision- maker to consider various emission parameters with relative ease. However, the user should be aware that this ease of use may give a project developer a too optimistic and simplified view of what is required in setting a baseline for a proposed project. As such, it is suggested that the user take a conservative approach in calculating the baseline emission factor for the project, particularly at the pre-feasibility analysis stage.

RETScreen takes into account the emerging rules for carbon finance, including the Kyoto Protocol. The Emission Analysis section was developed in collaboration with the United Nations Environment Programme (UNEP) and the Prototype Carbon Fund (PCF) at The World Bank. The Kyoto Protocol is the protocol to the United Nations Framework Convention on Climate Change (UNFCCC) that was adopted in 1997 in Kyoto at the third Conference of the Parties (COP 3). The Kyoto Protocol commits industrialized countries (defined as Annex I countries) to legally binding greenhouse gas (GHG) reduction targets during the period between 2008 and 2012. These commitments are on average 5% below 1990 emissions levels.

1The program, user’s manual and documentation including complete list of costing equations can be downloaded from http://www.nrcan.gc.ca/energy/software-tools/7465.

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RETScreen allows the user to evaluate proposed projects in both domestic and international markets, including projects that fall under the Kyoto Protocol's Clean Development Mechanism (CDM) and Joint Implementation (JI).

4. Energy status in Iran and carbon budget calculation of hydropower plants in Iran¹ The energy consumption in developed and developing countries is high. The per capita consumption of energy in agriculture, household and commercial and public, transportation and industry is 3.2, 1.8, 1.6 and 1.5 times of global average consumption respectively. Comparing the per capita energy consumption by fuel sources it is concluded that natural gas and petroleum and its derivatives consumption in Iran is 5.9 and 1.6 times of global average consumption respectively. Iran has the first rank in electricity production among neighboring countries and 14th in the world. The capacity of power plants in the 2015 has reached 74.1GW and the total electricity production has reached to 272.8 TWh. Figure 2 shows the share of each sector in electricity production.

Figure 2. share of each sector in electricity production in Iran [2015]

The total electricity produced by thermal and hydropower plants and renewable energy sources from 2011 to 2015 in Iran is illustrated in figure 3.

1 All of data used and presented here is obtained from the annual report of Ministry of Power for the year 2015

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Figure 3. Total electricity produced by thermal and hydropower plants and renewable energy sources from 2011 to 2015 in Iran

According to this report, the share of hydropower plant in electricity production is almost 5% in recent years and considering the existing hydropower potential in Iran, it is expected that the share of hydropower and renewable sources in general will increase in next years. This increase in exploitation of hydropower should be analyzed from environmental aspects as long as economical aspects. To calculate the GHG emissions we choose the value reported by WNA which is 26 g CO2-equiv.kWh-1. This value seems rational because of climate and vegetation in Iran. Taking into account 14012×10⁶ KWh of total electricity produced by hydropower plants in 2015, we obtain 364312 tons of equivalent CO2. In order to calculate GHG reduction of the hydropower plants of Iran for the year 2015 using RETScreen, we have to choose a baseline. The baseline will consist of thermal plants with a fuel combination of 57% natural gas and 18% gasoline and 25%

fuel oil. These combinations are obtained from the fuel sources of thermal power plants in Iran. The result of RETScreen run using the above mentioned data is illustrated in figure 4.

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Figure 4. Result of RETScreen run calculating GHG emission reduction

We can see that the hydropower plants in Iran in year 2015 prevented the emission of 9977112 tons of equivalent CO2 and this is equivalent to 1827310 cars and light trucks not used. This amount of CO2 is very high and if more hydropower plants are developed, an enormous amount of GHG emissions will be prevented.

5. CONCLUSION

The results of this study indicate that hydropower plants play an important role in GHG emissions reduction in spite of the fact that these plants have emissions due to the construction phase and biomass degradation.

Our study shows that hydropower plants of Iran in 2015 caused 9977111 tons of equivalent CO2 gross annual GHG emission reduction which is equivalent to 1827310 cars and light trucks not used. The results indicate that hydropower plants and renewable energy sources should be developed and exploited to their potential capacity to reduce the GHG and as a consequence prevent global warming.

6. R

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