وضعیت، روندها و اهمیت نیروی هیدرولیک آمریکایی در دورنمای تغییر انرژی
Abstract
1- Introduction
2- Methodology
3- Results and discussion
4- Conclusions
References
Abstract
Despite the considerable contribution of hydropower in driving the American economy for over a century, the rationale for hydropower in the U.S. energy mix needs to be reassessed in the context of advanced science and technology. Other alternative-yet-cheaper energy resources have been identified and hazards associated with aging hydro-dams have escalated in recent years. Furthermore, research has shown more negative environmental consequences associated with hydro-dams—and dams in general. To compare the contribution of hydro-electricity to the total energy production in the U.S., and to identify its regional distribution and contemporary patterns, we conducted a systematic analysis of large-scale multi-year data from U.S. federal agencies and tallied the nameplate capacities of major hydro-dams against their existing energy production values. We found that despite continuous efforts at upgrading hydro-facilities, since 2000 the mean contribution of hydroelectricity has remained less than 10% of the total generated energy in the U.S. and has been declining since then. Based on our results, we conclude that reservoir- and dam-based hydroelectricity may not be an efficient energy resource—at least from the American perspective, and perhaps it is timely to consider promoting other non-conventional renewable resources for energy production.
Introduction
Hydropower has been an integral component of American electricity production for nearly 130 years and has played a substantial role in the nation's industrial revolution [1]. Differences in regional precipitation and runoff, river morphologies, local settlement patterns and concordant energy needs and alternatives, and the nature of hydropower facilities has varied widely across the conterminous U.S. However, over time as energy demand has outstripped the feasibility to bring additional hydropower capacity online, the contribution of hydropower has declined in the nation's energy mix while, at the same time, annual total and per capita electricity usage in the U.S. has been increasing [2]. The feasibility of satisfying expanding energy needs from alternative renewable energy sources (e.g., wind, solar and biomass fuel) has been increasing with the rapid decline of their costs and improvements in their efficiency. Indeed, the leading U.S. federal labs have reported a consistent annual decline of the levelized cost of energy (LCOE) for land-based- and offshore-windfarms, and utility-scale solar installations in recent years. For instance, the LCOE value of a typical land-based wind project in the U.S. declined from $71/Megawatt hour (MWh) in 2010 to $49/MWh in 2016, and it declined from $225/MWh in 2010 to $173–207/MWh in 2016 for a typical offshore windfarm [3,4]. Hydroelectricity generation from impounded water is still viewed as providing a high level of energy supply services, probably because even in the recent context of other non-traditional sources becoming cheaper, it contributed a substantial 16.4% of the global energy mix in 2016 with an estimated total installed capacity of 1096 GW [5]. From the energy production perspective, three main types of hydro-projects, namely reservoir-based, run-of-river and pumped-storage have been identified; each with its own inherent merits and demerits. Perhaps the most important appeal of a hydroelectric plant is its capacity to load balance instantly as the electricity demand varies on a diurnal basis [6]. Initially, hydropower was promoted as a “carbon-emission free” energy resource and a panacea to mitigate atmospheric pollution; however, recent studies, emerging from tropical to temperate areas—including the U.S., have debunked those assertions by reporting significant emission of greenhouse gases (GHGs) from reservoirs into the atmosphere [7,8].