Recent innovations and trends in in-conduit hydropower technologies and their applications in water distribution systems.

Water conduits have a large untapped potential to recapture energy for small hydroelectric generation, which can substantially reduce grid electricity consumption and/or provide renewable energy to water agencies. Over the past decade, there has been a recent technological renaissance in off-the-shelf "water-to-wire" turbine technologies including reaction, impulse, and hydrokinetic turbines that target the sub 1-MW in-conduit hydroelectric market. However, adoption of small hydropower technologies remain limited in water and wastewater utility sector, possibly due to the lack of market penetration and exposure. Moreover, information about newly developed small hydropower technologies in the last 5-10 years for in-conduit applications are highly dispersed in the literature. As such, this paper is a comprehensive review on recent technological innovations and trends in hydropower generation from water conduits. Sixteen turbine technologies (eight conventional turbines and eight emerging turbines) are assessed and compared based on their potential benefits and challenges, technology readiness levels, as well as potential sites for installations in diversion structures, potable and irrigation water distribution systems, and wastewater outfalls. Although conventional turbines are considered to be more robust, the modular design of the newer turbines potentially offers a more cost effective solution and better scaling-up capability. Selected case studies on the application of conventional and new turbines for pipelines are also are also reviewed and discussed.