Review on the externalities of hydropower: A comparison between large and small hydropower projects in Tibet based on the CO2 equivalent
Introduction
Externality is an inefficiency that appears when part of the costs or benefits of an activity are external to the decision maker’s calculations. In other words, part of the benefits shared by or part of the costs threw to those who play no part in the decision [1]. When it comes to hydropower development, the plant construction cost and hydroelectricity benefit, which are imposed on the hydropower enterprise directly, are the main costs and benefits in the general cost–benefit assessment; however, little attention is paid to many of the costs imposed on the environment [2], [3], [4]. To conduct a complete assessment of the externalities, this paper defines which as the costs and benefits that impose a burden on the environment and external community (Fig. 1).
An installed capacity of 10 MW is often set as the demarcation between large hydropower projects (LHPs) and small hydropower projects (SHPs) [5], but different countries set different upper limits to classify hydropower [6]. 50 MW is the latest hydropower classification norm in China [7]. A hydropower project exceeding 50 MW is often involved with a high dam (>30 m) construction to form an artificial reservoir, while hydropower below 50 MW is often in the form of run-of-river or a low dam (weir) with flow diversion [8]. Therefore, this paper adopts 50 MW as the standard by which to differentiate LHPs and SHPs. Both LHPs and SHPs are bracing for a new round of construction as energy demands increase and technologies develop. In this context, the installed capacity of them will also increase. For example, geographic information systems (GIS) and remote sensing (RS) have been introduced into the process of exploring hydropower sites and their maximum hydropower potentials [9], [10]. Generally, LHPs generate greater electrical power than SHPs as a result of its greater installed capacity. However, high dam removal efforts are receiving increasing support from a public concerned with river ecosystem restoration in recent years [11]. In this context, LHPs face significant challenges from issues regarding environmental and societal externalities, which has led to greater appreciation of SHPs [12], [13]. However, SHPs also face many doubts from issues regarding cumulative environmental problems when SHPs are put to widespread use [14].
Because of the issues described above, a comparison of the externalities between LHPs and SHPs is required. Many countries around the world make a high priority in developing hydropower under the increasingly tense circumstances of traditional fossil energies [15], [16], and the low-carbon economy requirement also trigger the development of hydropower [17]. As a result of the different operational approaches, different levels of externalities are embodied in LHPs and SHPs [5]. Therefore, a comparison between the externalities of LHPs and SHPs can clarify which approach contributes more to environmentally friendly hydropower development.
To conduct a quantitative comparison, it is essential to transform the quantification of the different externalities into the same units. Considering that these externalities all directly or indirectly contributed to GHG activity, it is feasible to transform them into CO2-e. For example, hydropower reservoir emits GHG directly via the decay of flooded vegetation, meanwhile, its flood control function can offset some other shadow flood control projects, and then offset GHG emission by shadow project construction indirectly.
Section snippets
Review of the externalities of hydropower
Cascaded hydropower development will cause a one-time impact from each individual hydropower plant and a cumulative impact from the cascaded hydropower plants. The civil works and reservoir impoundment are the two main sources of environmental and societal impact for a single hydropower plant. Therefore, this paper reviewed the inventory of externalities for hydropower by civil works, by reservoir impoundment and by cumulative impacts, and then established a general externalities inventory for
Externalities transformation based on CO2-e
Externalities inventory of hydropower has been established in the form of different dimension, and it is necessary to uniform the different dimension for the comparison. Transforming the externalities into CO2-e activity is a fresh attempt to link the environmental issues and carbon footprint calculation of hydropower. CO2-e activity includes carbon emission, carbon reduction and carbon neutral, which depends on the own features of the impacts. Therefore, the total externalities of hydropower
Study area and data source
As a hydropower reserve base for China, the hydropower theoretical potential and technical potential are 2.01×105 MW and 1.10×105 MW, respectively, in Tibet, ranking them first and second place among the provinces in China, respectively [58]. Tibet is very likely to be the main hydropower development area in China after 2020, and hydropower development in Tibet will contribute to the “west-to-east power transmission” policy and contribute to the achievement of the low-carbon goals in China [59].
Conclusions
Transforming the externalities of hydropower into CO2-e values is a new approach that enables the efficient assessment of the externalities, which allows a feasible overall comparison of different externalities among different hydropower patterns, and proposes a new attempt to perfect the carbon footprint calculation of hydropower.
Low-carbon potential of hydropower has been overestimated when combining with net carbon emission by externality. Externality and carbon activity is intrinsically
Acknowledgement
The work reported in this paper is funded by the National Science & technology Pillar Program, China (no. 2012BAC05B02), the Fund for Innovative Research Group of the National Natural Science Foundation of China (Grant no. 51121003) and the State Environment Protection Commonweal Special Program, China (no. 201209032). The author gratefully acknowledges the funding support.
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