Philadelphia is looking for a few good ideas to harness the potential energy flowing through the city's waterways.

The Philadelphia Energy Authority, along with the city Water Department, has issued a formal "request for information" about possible projects. Ideas could involve hydroelectric energy, kinetic energy, or thermal energy from the city's rivers, streams, or existing water infrastructure systems, said Alon Abramson, a project manager for the Energy Authority.

The nonbinding proposals, to be submitted by an April 27 deadline, may help the city shape a formal bidding process later to embark on one or more projects.

"We're keeping it as broad and as vague as possible," said Abramson. The Energy Authority, which aims to leverage $1 billion toward energy efficiency and clean energy in the city over the next decade, says the deadline provides sufficient time for companies to develop proposals, or to inspire universities to organize class projects to research potential power systems.

"The goal is to determine which low-impact hydrokinetic generation designs and/or heat pump technologies might be cost effectively used to generate power and/or heating and cooling from waterway sites for direct local use, for integration into the power grid, or in a microgrid application," the city's proposal says.

Lance Haver, City Council's director of civic engagement, thinks the process could be an opportunity to move forward on a hydroelectric project that would add value to the Flat Rock Dam on the Schuylkill, where the Water Department plans to repair the 20 percent of the dam that it owns. (The state owns the western side.)

Haver believes the project, coupled with a restoration of water flow to the stagnant 1.6-mile Manayunk Canal, could provide an innovative energy producer to power part of the Manayunk commercial district.

"If one of them has the right technology, the authority has the ability to finance the construction based upon a power purchase agreement with the businesses on Main Street," Haver said in an email. "The proximity to the power source, both thermal and electric, may make this type of development `a wave of the future.' "

The city's current design to restore the dam and install a canal intake include leaving space for a hydroelectric system, said Lance Butler, a Water Department senior scientist. The Schuylkill's flow might support a 2-megawatt power system, he said.

"Our goal here was to make it hydro-ready for another interested third party," Butler said.

Hydro power has a long history in the city: The Wissahickon watershed is littered with the ruins of 19th-century water-powered mills, and the Fairmount Water Works employed a hydro-powered pump to lift water from the Schuylkill to the reservoir formerly located on the Art Museum site.

Philadelphia Hydro-Electric Corp., created in 1909, envisioned building a power plant at the Flat Rock Dam to supply the city's emerging electrified mass-transit system, but the generator was never constructed, Butler said.

Haver, the city's former consumer advocate, cites small-scale hydro systems installed on a Phoenix, Ariz., waterfall and in a city's drinking water system or in-stream turbines submerged in canals and rivers as examples of the types of projects that might find a home in Philadelphia.

While small-scale hydro projects often generate public excitement, many never get off the ground because they can't make money, especially in a low-energy price environment. Such was the case with an innovative pilot project the Water Department explored five years ago to extract thermal energy from the warmth of the city's sewage.

"Most projects require low or subsidized installation costs to receive a viable financial return on investment," said a 2015 report commissioned by the Pennsylvania Environmental Council exploring the financial feasibility of low-impact hydro projects.