While climate systems are incredibly complex, the causes of contemporary climate change and many of the potential impacts are now well understood. The atmospheric concentrations of several greenhouse gases (e.g., carbon dioxide, methane, and nitrous oxide) have increased to unprecedented levels, in at least the past 800,000 years, and carbon dioxide levels are now hovering around 400 ppm, a concentration beyond the 350 ppm concentration now widely recognized as a target level to preserve our social systems. As a result, it is unequivocal that there is a warming of the climate system, including the atmosphere and oceans, and it is consensus that human influence has been the dominant cause of warming since the mid-20th century. We understand, with varying degrees of certainty, that this warming has and will continue to cause snow and ice melt, sea level rise, ocean acidification, loss of permafrost, increased severity of storm events, significant changes in precipitation patterns, biodiversity loss, spread of certain insect-borne diseases, and the displacement of human populations and cultural loss. And the positive and negative feedback loops inherent in the climate system could very well accelerate these impacts.1 It is also worth noting that there are major inequities intrinsic in contemporary climate change. Relatively few of us have enjoyed the lifestyle associated with high greenhouse gas (GHG) emissions, and, of course, not everyone is experiencing the burdens of climate change equally. As one metric, climate change threatens to cause the largest refugee crisis in human history. By 2050 more than 200 million people, largely in Africa and Asia, will potentially be forced to seek refuge in other places. Hundreds of millions more are expected to experience hunger and other life-altering hardships due to climate change.2
There are hopeful signs that we are altering the course of climate change; for example, last year the global economy grew by close to three percent, but energy-related carbon dioxide emissions remained constant and renewables accounted for nearly half of the new power generation capacity.3 And, just months ago at the COP21 meeting in Paris, the ministers from 195 countries adopted, by consensus, a legally binding agreement to fight climate change. The COP21 accord aims to help the world abandon fossil fuels within this century.4 The reality at this moment, however, is that we continue to rely largely on coal, oil, and natural gas, the highest life cycle GHG emitting energy sources.5 In fact, globally 68 percent of electricity generation still comes from fossil fuels,6 and energy demand continues to grow by about two percent per year.7 There also remains the fact that 1.3 billion people worldwide still lack access to electricity, while 2.7 billion must rely solely on traditional biomass to meet their energy needs. Another one billion people have access to poor quality electricity or can only obtain it intermittently from unreliable grid networks.8
Envisioning and achieving a more sustainable energy future will, therefore, require us to simultaneously address energy-related social and environmental inequities while improving our energy efficiency and production all around the world. And, we must move on this work quickly, recognizing that we need to analyze each choice as holistically as possible, while accepting that no solution is perfect—there will always be some level of environmental, social, and/or economic impact.
Small hydropower has been gaining ground as a renewable energy source that could play a significant role in both reducing our fossil fuel use in many developed and developing countries and in helping some regions of the world that are currently handicapped by inadequate electricity supplies.9 While there is no international agreement on what constitutes small hydropower, and the upper limit can vary between 2.5 and 100 MW depending on the country and state, the most widely accepted value is 10 MW.10,11 And, indeed, much of the literature on the assessment and impacts of small hydropower uses this definition.
According to comprehensive assessments, there is a global potential of 173 GW of small hydropower, and only 75 GW have been installed to date. Approximately 65 percent of this global potential is in Asia, 16 percent in Europe, 13 percent in the Americas, five percent in Africa, and one percent in Oceania. Over the past decade, many countries have executed fairly aggressive policies to promote the design and implementation of small hydropower projects given the purported minimal environmental, economic, and social impacts of small hydro, especially compared to more conventional energy sources.12 Because of this global push, there is a burgeoning literature assessing critical questions regarding the comprehensive costs associated with small hydro. Evaluating these questions has proven challenging given the complexity of methodology,13 variation of impacts based on design and ecosystem sensitivity,14 and variation in input to and oversight of the design, implementation, and operations of small hydro.15 There also have been comparisons of small hydro to not only other renewable energies and more conventional sources, but also analyses of the accumulated impacts of many small hydro projects compared to the equivalent production of several large-scale hydro projects.16,17
The balance of the most comprehensive and data-intensive studies point to the potential of small hydro as an important component of a cleaner, more just energy future. For example, one total life-cycle assessment found small hydro produced far fewer gCO2-equiv/kWh than more conventional sources of energy (e.g., coal, oil, natural gas),18-20 and, depending on the assumptions about reservoir emissions and the type of turbine installed small hydro outperformed even photovoltaic, nuclear, and, in some cases, wind in terms of greenhouse gas production.21,22 In addition, it appears that reducing gCO2-equiv/kWh also leads to a reduction of most other environment impacts (e.g., abiotic resource depletion, acidification, eutrophication, human toxicity, eco-toxicity, etc.).23 Small hydro, and, in particular run-of-river small hydro (that is, hydropower where there is little to no water storage associated with the dam), also minimizes, in comparison to larger-scale hydro, the changes in stream flow, modifications to thermal regimes, sediment buildup, alterations to aquatic communities, and risk to the downstream natural and built environments should there be a failure to the dam.24-26
Economically, small hydro can offer enhanced price stability,27 competitive costs,28,29 and low energy payback times (that is, the years necessary to recover primary energy consumption throughout a project’s life cycle by its own energy production).30 Another important benefit is that this technology has been around for a long time, and, hence, equipment is readily available, and parts are durable.31 In addition, small hydro can smooth variations in supply from other, more intermittent, generation sources, and it can provide important flexibility given that production can be shifted to periods of higher energy demand. And, given that small hydro is a domestic, distributed power source, it contributes to national security and can dispatch, with minimal startup time, to a grid for blackout periods.32,33
While few studies discuss the additional social consequences of small-scale hydro, those that do point to several benefits including the ability to bring small hydro to rural environments and the reduction of population displacement and cultural loss that is often associated with other forms of energy production, including large hydro. In addition, small hydro has been associated with fewer point sources of pollution, fewer downstream hazards, and reduced impacts to crop yields and overall quality of life.34-36 To realize these comprehensive social benefits, however, there must be proper oversight, community engagement, and consultation.37
It should be recognized that there is a seemingly competing stance on small hydropower—that is the vocal call for the removal of dams. Part of the confusion lies in the fact that in some literature, all dams, large and small, are lumped under a single heading. The reality, however, is that not all dams are created equal. In general, a large dam will have greater impact than a small dam, a dam in a critical ecological area will have greater impact than one placed in a less critical area, and dams that create significant reservoirs will have more impact than a dam operated in a run-of-river mode.38 Even those who are most focused on stream restoration recognize that dams are an important part of an energy portfolio that better addresses greenhouse gas emissions. We should focus on removing the most problematic dams in terms of environmental impact, age, and safety,39 and dams should be considered, and ideally coordinated, in the larger context of regional watersheds.40 But the refurbishment, and even the construction of new, low impact dams that are sited, operated, and mitigated responsibly, could make important contributions to our future energy mix.41
Case Study: Small Hydro at Skidmore College in Saratoga Springs, New York
While small hydropower figures (again defined as up to 10 MW) are difficult to assess in the United States given the state-to-state variation in the definition of small hydro, it is clear that the installed capacity of ~6,785 MW is only a fraction of the potential capacity.42 Multiple reports have been issued that indicate literally thousands of additional sites for small hydro development in the United States, including numerous run-of-river opportunities,43 and conservative estimates of potential small hydropower range from 8,000 MW to upwards of 30,000 MW.44,45 At roughly 800 homes per MW of capacity, small hydro could power between 6.4 to 24 million homes based on the approximations above.46 Perhaps the most intriguing subset of this possible growth is the additional and new power from existing infrastructure including conduits, locks, non-electrical producing dams, and milldams.47-49 While the environmental tradeoffs of each of these existing sites must be evaluated, not only in the context of the individual project, but in the more regional context of surrounding watersheds,50 we offer here a case study of the revitalization of an old milldam that illustrates the possible multifaceted benefits of such an endeavor.
Small hydropower, of course, started with the wooden waterwheel, and prior to the Industrial Revolution, waterwheels of various types were used throughout Europe, Asia, and North America for centuries, mostly for milling grain. Towards the end of the 19th century, many mills were replacing their waterwheels with highly efficient turbines for larger-scale supply of electricity,51 and as a result, in some countries there is a significant pool of refurbishable infrastructure.52,53 For example, there are thousands of small hydroelectric plants throughout Europe and the United States.54
Similar to other regions of the United States, small dams were critical to industrial production in New York State during the 1800s and early 1900s, but use of these dams was curtailed in the mid-20th century when most utilities refused to buy power from private sources. Those utilities that did purchase power paid such low rates that it did not benefit private owners to stay in business.55 More recently, however, there have been several changes that have helped to revitalize the small-scale, distributed energy market, and two major legislative changes stand out as making innovative, small hydroelectric partnerships possible and productive.
The first is the National Energy Act (NEA) of 1978, which was essentially a legislative response to the 1973 energy crisis. NEA included a variety of energy efficiency programs, tax incentives, tax disincentives, energy conservation programs, alternative fuel programs, and regulatory and market-based initiatives aimed at reducing the United States’ dependence on foreign oil. A subdivision of the NEA, the Public Utilities Regulatory Policies Act (PURPA), was aimed specifically at promoting energy conservation and greater use of domestic and renewable energy. Essentially PURPA once again created a market for small-scale producers by compelling regional utilities to purchase this power at favorable rates.56 While the usefulness of PURPA has arguably come to a close,57 it played a critical role, as you will see, in keeping potentially useful infrastructure at least partially intact.
The second piece of legislative change came in June 2011 at the state level, when New York expanded net metering (when a customer-sited renewable energy system is connected to the regional grid through the customer’s utility meter) and established remote (or virtual) net metering (meaning that electricity can be generated in one location and credited toward consumption at another location). When originally passed, remote net metering in New York was focused on wind, solar, and farm waste, but in August 2012, New York enacted legislation expanding remote net metering to include non-residential small hydro systems.58
Skidmore College is a small liberal arts college in Saratoga Springs, New York, that began exploring small hydro opportunities about three years ago as part of a commitment to reduce greenhouse gas emissions and develop a diversified renewable energy portfolio. The school’s portfolio already included significant geothermal, solar thermal, and solar photovoltaic installations, and the redevelopment of small hydro facilities in the region sparked further interest. The College partnered with Gravity Renewables on the project because of the comprehensive service they could provide (Gravity is an investor-backed owner, operator, and developer of small hydroelectric power plants in the United States) and because of their emphasis on education and the restoration of historical sites.
After looking at several small, low impact dams, the school’s focus quickly became a run-of-river weir, originally built in the early 1800s, that sat on an existing fault line and waterfall called Chittenden Falls on the Kinderhook Creek in Stockport, New York (Figures 1 and 2).
Years of inadequate funding threatened the future of the historical dam, and the facility had the potential to soon become both an environmental and social liability for the surrounding area. Gravity Renewables purchased and revitalized the facility, with Skidmore minimizing the risk for the company by signing an Operating Agreement to purchase the power produced by the facility for twenty years. This project was the first remote net metered hydroelectric project in the nation, and it is expected that the Chittenden Falls facility will ultimately produce close to 4 MWh per year, enough to meet approximately 18 percent of Skidmore’s electricity demand.
Exploring the long history of the dam at Chittenden Falls became a fascinating industrial archeological research project that revealed the deep connections between the facility and the surrounding community. The region where the dam is located, the Hudson River Valley, was at the forefront of the Industrial Revolution in America, and 19th century waterways in the Valley were dotted with the sluiceways, penstocks, waterwheels, weirs, minor dams, and turbines that helped power this transformation. Stockport’s available waterpower from Kinderhook, Claverack, and Stockport creeks, and its close proximity to a major transportation artery, the Hudson River, gave the town a natural advantage over more inland locations, especially prior to the development of rail transportation (Figure 3). Three major manufacturing entities were organized in Stockport by 1809, and the Kinderhook Creek was cited as “one of the best streams for mills in the United States” in 1824.59
From 1809 through the mid-1900s, the Chittenden Falls powered an economic base for the region, including the production of high-quality paper (Figure 4), nails (Figure 5), straw wrapping paper, textiles, wire fencing, and paper board.60 A fire swept through the mill in 1962, and it sat in ruins until, prompted by PURPA legislation, it was purchased by Paul and Adelaide Eckhoff and their five daughters. In the summer of 1979, Paul and his family founded Chittenden Falls Hydro Power, Incorporated, and began the costly and time-consuming work of restoring the facility.61
The family continued their restoration work, even renovating one of the older structures to accommodate microresin manufacturing, until Paul’s passing in 2006. The facility then passed briefly through several hands prior to the partnership between Skidmore College and Gravity Renewables.62
This small hydro project is a rich case study in sustainability in that it simultaneously addresses environmental, economic, and social concerns. From an environmental perspective, the dam at Chittenden Falls sits on a nearly thirty-foot natural abutment and waterfall. The dam is classified as a small, low impact dam by the Federal Energy Regulatory Commission (FERC), which means that this structure poses little threat to the surrounding natural and built environments. And, as discussed above, run-of- river small hydro projects such as this outperform essentially all other forms of electricity production in terms of life cycle GHG emissions and most other environmental impacts correlate tightly with GHG emissions.63,64 Economically, this facility provides important benefits to the Stockport community by contributing to the town’s tax base (both school and property taxes), local employment, and other local spending, and can lead to more predictable electricity pricing for Skidmore. From a social perspective, revitalizing these facilities contributes to both the aesthetic and vigor of the local community. Too often, old industrial sites, such as this, fall into ruin and become targets for vandalism and potential community safety issues. The Chittenden Falls dam is part of the architectural history of the Hudson Valley, and we discovered, somewhat unexpectedly, a deep intergenerational pride in this facility, not unlike what we see with the family dairy farms that dot the Upstate New York landscape. The restoration of this cultural icon has already been met with much encouragement and gratitude. The work related to the dam has also forged a new community of collaborators including people from Skidmore, Gravity Renewables, and Columbia County. As is the case with the school’s other sustainability projects, this small hydro project is a pedagogical tool that has and will be used in a variety of courses across Skidmore’s campus, hence tapping the exponential power inherent in educational institutions.
This case study also represents a segment of small hydropower that has the potential to develop relatively quickly. Although recent laws (e.g., the Hydropower Regulatory Efficiency Act, the Bureau of Reclamation Small Conduit Hydropower Development and Rural Jobs Act) have helped alleviate barriers to small hydropower development, the licensing process remains lengthy and costly for most projects.65 The FERC licenses for facilities like Chittenden Falls have already been established, and many of these licensed facilities could, with reinvestment, see a boost in power production. Other licensed facilities are essentially sitting idle and are at risk of being taken offline completely. And while it is true that these licensed facilities will require relicensing at some point in the future, the relicensing process tends to be shorter and less costly. In addition, if a facility is operational, there is a steady revenue stream throughout the process. State-level regulations on remote net metering are also evolving fairly quickly. The number of states with remote net metering policies jumped from 10 to 16 in the past two years, and many of these states (e.g., those in New England) have a high proportion of historic milldams.66 These federal and state regulatory changes, combined with more ubiquitous renewable portfolio standards and goals, are opening the door for more innovative operational partnerships around restoration projects like Chittenden Falls, and small hydropower in general.67,68 While there are some milldams that are beyond cost-effective refurbishment and/or may need to be removed for particular environmental or social reasons, the sheer number of facilities and the possible multi-faceted benefits of restoration make small, historic hydropower facilities ripe for further exploration.
To learn more about the small hydro project at Skidmore College, please see https://academics.skidmore.edu/blogs/microhydro/.
We’d like to thank the following people for their dedication in bringing the Chittenden Falls small hydro project to fruition and/or their help with the research related to this project: Omay Elphick, Director of Business Development for Gravity Renewables and alum of Skidmore College; Connie Frisbee Houde, History Collections Technician at the New York State Museum; Mike Hall, former Director of Financial Planning & Budgeting at Skidmore College; Paul MacCormack, Gravity Renewables Operator of the Chittenden Falls micro-hydro facility; Diane Shewchuk, Executive Director and Curator at the Columbia County Historical Society; all the staff associated with the Skidmore Sustainability Office; and Colby Kellogg-Youndt.