Farming out small hydro advice

30 June 2011



The Applegate Group and Colorado State University have teamed together to produce a report on the potential for small hydropower production at existing irrigation facilities in this state.


In the US state of Colorado about 5% of electricity is currently provided by hydropower. Since settlement in the 1800s Coloradans have been utilising the geography and hydrology to exploit this renewable resource. Traditionally, most hydropower has been developed on large dams and related structures; few small dams, canals and conduits have been utilised.

Simultaneously, there has been a significant public push toward clean and renewable energy sources. Colorado House Bill 10-1001 increases the Renewable Energy Standard from 20 to 30% for investor owned utilities by 2020. This includes a requirement for one-tenth of that renewable electricity to come from distributed generation. The Governor’s Energy Office of Colorado (GEO) has been leading a renewed effort to increase small hydro production, which has been recognised as a desirable source of renewable energy, particularly since it is less variable than most renewable resources. The GEO has introduced programmes to address these issues, including a Renewable Energy Development Team and a FERC streamlining pilot project. In addition, the Colorado Department of Agriculture offers research grants through their Advancing Colorado’s Renewable Energy (ACRE) programme to promote energy-related projects beneficial to Colorado's agriculture industry.

The Applegate Group and Colorado State University teamed together to study the development of agriculturally related small hydro in existing irrigation infrastructure. The study intends to provide information on state-wide small hydro development to agricultural water users and policy makers, including guidance on site types, equipment and interconnection.

The Applegate Group is a water resources engineering firm that specialises in raw water conveyance and storage infrastructure as well as water rights, planning and development. Applegate’s clients are both public and private entities who own and operate irrigation and municipal water supply systems. A number of these clients have expressed an interest in producing hydroelectric power but were generally hesitant to invest without more information. Colorado State University’s Engines and Energy Conversion Laboratory supports an extensive power engineering education and research programme. CSU researchers are actively studying the integration of distributed renewable energy resources into regional and island power systems.

The study

There are almost 3.5M acres [1] of irrigated land in Colorado supplied with water by canals, ditches and pipelines. This extensive statewide water supply system is fragmented geographically and operationally. The study, Exploring the viability of low head hydro in Colorado’s existing irrigation infrastructure, focuses on low head technologies which can be productively installed in these existing constrained waterways – a hydropower area that appears to be lacking in overall knowledge. A number of low cost, low head turbines have recently been introduced to the market but are unknown to Colorado’s water users. There is limited knowledge of the viability of these low head turbines in typical irrigation structures which are often both low-flow and low-head.

There has also been no systematic identification of attractive sites within irrigation systems, and no developed process to easily classify and assess sites for development. The study also focuses on sites within existing infrastructure due to the ease of permitting and developing projects within an existing canal or conduit. It is important to note that this study investigates only a portion of the hydropower potential in Colorado. Sources that do not meet the constraints of this study were not assessed nor were efficiency enhancements at existing hydropower facilities – even low head facilities.

The purpose of this study is to help educate agriculturally-related water users on the opportunities that may exist to implement low head hydropower on their systems. The study has three goals:

1. Research available low head technologies.

2. Match those technologies with typical irrigation structures by studying two project canals.

3. Estimate a state-wide potential for low head hydropower.

The results of the study will be conveyed through a final report submitted to the Colorado Department of Agriculture, and posted on a website dedicated to low head hydropower in Colorado. The project team has also held a number of workshops, and presentations and has written a number of conference papers and articles to disseminate this information.

The Ditch and Reservoir Company Alliance (DARCA) of Colorado provides a platform for the transfer of information and is a strong supporter of this study. As an organisation its mission is to become the definitive resource for networking, education and advocacy. Membership includes all types of irrigation enterprises - ditch companies, reservoir companies, laterals, private ditches, and irrigation districts. The project team led an all day workshop prior to the annual DARCA convention, focused on low head hydropower. The workshop was very well attended and received, highlighting the interest that exists in Colorado’s irrigation community. Attendants heard from engineers, turbine manufacturers, regulators and developers of low head hydropower.

Challenges and opportunities

There are many challenges related to successfully implementing a hydroelectric facility in a Colorado irrigation canal, including seasonality, locations remote from power service, the variable nature of the flow and reservoir releases. There are also opportunities afforded by the existing engineered infrastructure of irrigation systems. Pipelines and drop structures are already in place but many are in need of modernisation. Hydropower could be incorporated into the structure during heavy maintenance work. Irrigation operators are generally interested in finding additional revenue sources to augment their finances and reduce shareholders’ annual assessments. These physical opportunities joined with the interest of the organisations may support such development projects.

Permitting delays and regulatory complexity have long retarded new hydropower development. Most irrigation system sites are quite small. Permitting costs do not scale well to small sites, creating disproportionally high up-front costs that often kill economic viability or dissuades potential investors from seriously considering small hydropower projects.

To address this issue, Colorado, acting through the Governor’s Energy Office (GEO), signed a memorandum of understanding with the FERC to streamline and simplify the authorisation of small scale hydropower projects – particularly targeted at existing structures and man-made waterways. This trial rule change may significantly lower permitting barriers for small hydropower.

Electrical interconnection also presents both challenges and opportunities. Ideal hydropower sites – like ideal wind or photovoltaic sites – are those with ready access to electrical service. Pulling new electrical service over any distance is often cost-prohibitive for small renewable systems. Conversations with one utility indicate that systems as large as 500KW can be connected at the distribution level in modern distribution systems. However, on remote rural feeders sizes may be more restricted. Many utilities limit distributed generation to 10-15% of the peak load on a feeder.

Traditionally, hydropower systems have utilised synchronous generators, or occasionally induction generators, coupled directly to the power system. While more efficient than inverter-based systems, such generators are more difficult to control and produce larger fault currents – surge currents during shorts or other system issues. Therefore, the study authors expect utilities to steer small hydropower systems toward inverter-based generation. Inverters are generally equipped with solid-state synchronisation, remove control capabilities and produce far less fault current than similarly sized generators – all of which ease interconnection complexity.

Progress

An interim report was published in September 2010. The report addresses the project’s first goal, researching available turbine technologies. Over 20 low head turbines that may be appropriate for sites in Colorado, with required conditions and contact information, have been identified. The final report, due in May 2011, will include these turbines and a few more.

Estimating the potential of all of the irrigation canals has proven problematic. The intent of this study was to obtain a realistic estimation of hydropower potential by directly identifying specific sites, rather than using a GIS data, as has been done in other studies. Mailed, emailed and hand delivered surveys were provided to over 250 irrigation entities with a decreed diversion flow rates over 100cfs. Only about 10% of those surveys have been returned, and those that were returned required some level of persuasion by the study authors. Reasons for the low return rate are hard to identify. Clearly, the survey requests specific, technical, information from operators who may not be comfortable with technical requests. These entities are also thinly staffed, and often overloaded with tactical issues. The low return rate is ironic, given the high interest in hydropower by many irrigation entities.

The team has learned that, to truly assess small hydropower potential state-wide, a researcher will need to travel the state and visit each canal that has promising overall characteristics. This approach, or perhaps another approach of mid-level detail, should be explored further.

Overall, the project has been a success in raising awareness and educating irrigation entities about the opportunities that exist in small hydro. The final report will provide practical resources for those considering development. Estimating the overall state-wide potential has proven more difficult than expected, but the study indicates that potential does exist in a number of irrigation systems. These sites can be developed with minimal impact and the project will benefit a number of agricultural producers. Existing irrigation infrastructure deserves focused attention in the future development of low head hydropower in Colorado.

The authors are Lindsay George, Applegate Group, 118 W 6th Street, Suite 100, Glenwood Springs, CO 81601, US, Email: [email protected]; and Dan Zimmerle, Engines and Energy Conversion Laboratory, Colorado State University, 430 N College Avenue, Fort Collins, CO 80524, Us, Email: [email protected]


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