"Basically, we would be installing a turbine generator on our water system," said city Public Works Director Carey Meyer.
An 11-page feasibility study of the project, prepared by Meyer in partnership with Homer Electric Association, calls for three small turbine engines to be installed inside the city's two 12-inch main water pipes at points where water pressure is already high. There are seven places in the pipes where the pressure is so high -- in excess of 100 psi -- that pressure reduction stations have been built to relieve it. Now, according to the study, three of those points, chosen in part for their proximity to existing overhead power lines, could be tapped to produce electricity.
But is it safe to install turbine engines inside pipes carrying treated drinking water?
"The idea of generating power through water pipes is not new, but it is unusual to be doing this on a drinking water system," said Meyer. "My understanding is that there are innovations that make that more feasible now than it may have been in the past."
While no hydropower project using the power of treated drinking water has yet been built in Alaska, a handful of them, including a successful multi-turbine system built into the water pipes of Boulder, Colo., have been constructed in the Lower 48.
Ensuring the project would not negatively affect Homer's water supply will be the primary focus of pre-construction, said Meyer. Approval from the National Sanitation Foundation would have to be granted, he said, along with permits from the Alaska Department of Environmental Conservation and the Federal Energy Regulatory Commission.
"There's lots of stuff in water systems, including valves and meters," said Joe Vogel, senior engineer and project manager for Bristol Environmental and Engineering Services, the company that will conduct pre-construction services. "Homer, because of the unique water system, is one of the few places where you could even do something like this."
Bristol Environmental, a subsidiary of Bristol Bay Native Corporation, is the company that originally drafted Homer's water and sewer master plan and Vogel has been working on the city's system for more than 15 years. The company was awarded the pre-construction contract by the Homer City Council at their Nov. 24 meeting and has already drafted a model of how the turbines would work.
"It's going to be a very interesting project," said Vogel. "It's a very exciting use of alternative energy."
Meyer estimates the turbines could each generate 85,000 kilowatt hours per year, enough to power roughly 10 homes, and would save about $10,000 in energy costs. The total estimated cost of the project, including pre-construction, is $364,000.
Pre-construction costs were funded by a $31,200 grant form the Alaska Energy Authority and a $7,800 local contribution, split evenly between the city and HEA.
The power generated by the turbines could be fed directly into the existing HEA power grid.
"We've been thinking that we'll be able to put it on the grid at these three locations and then the city could trade that power with HEA for power the city uses at city buildings," said Meyer. "That's the general approach, anyway. We'll formalize that next year when we have a firmer idea whether this is a good idea or not."
Meyer hopes to have a final design for the project by the beginning of next summer.
Source:homernews.com
