Hong Kong has a network of water mains travelling over 4,847 miles, which is comprehensively monitored to make sure its water supply remains clean and well maintained. Water mains need power for those devices. Conventionally, they are powered by putting small turbines in pipes to produce electricity from drinking water.
Good news: Specialists in hydrodynamics, mechanical engineering, and renewable energy have created highly efficient devices to harness the power of water, specifically to tap the power of wasted water pressure. The system consists of an external hydroelectric generator and highly efficient spherical water turbine that dips into flowing water and reclaims residual pressure. When water passes through, the turbine drives a central rotating shaft and a micro generator to produce electricity.
The key lies in intelligent design to extract energy from flowing water. In optimal scenarios, the turbine only takes away a fraction of kinetic energy. It strikes an accurate balance between water volume, water pressure, and consumption of hydrokinetic energy, which boosts efficiency without reducing the momentum of running water to guarantee a reliable water supply. Turbine blades are carefully sized to intersect the largest possible area of water flow and minimize water bypassing.
“We’re capturing energy that would otherwise be lost,” says Priddy, director of operations for Lucid Energy, a Portland start-up.
Source: Lucid Energy
In January, Lucid became the first company in the U.S. to install a commercial micro-hydro energy system, flipping the switch on 1,100 megawatts of renewable energy. Torrents of water rush beneath cities all over the world. In Portland’s case, the water moves at an average rate of 39,000 gallons per minute. Lucid harnesses that energy with a system that’s striking in its simplicity.
For example, twenty feet below a street in Portland, Oregon, and inside city-owned water pipes, are four keg-size turbines that look like giant egg beaters-only they churn out hydroelectric power. The only technology inside the water pipes are five-bladed spherical turbines, 42 inches in diameter, made of stainless steel and composite fiber. Most of the other parts-seals, bearings, grid connections-sit outside them. “The whole system is designed so water delivery is never disrupted.
Lucid’s system works in gravity-fed pipes, which makes them a good fit for western and northeastern states, where water rushes downhill into showers and sprinklers. Sensors in the pipes provide data on water pressure and quality, which can forewarn of burst pipes or water contamination. A pilot project in Riverside, California, in 2012 demonstrated the safety and potential of the system. As a result, the company’s turbines are certified for use in pipes that carry municipal drinking water, as well as industrial, irrigation, and wastewater.
These systems can be installed with third-party financing. Harbourton Alternative Energy provided the capital for the $1 million installation cost in Portland. The city, the Portland Water Bureau, and investors will share revenue generated by the turbines for the next 20 years.
The LucidPipe™ Power System can reportedly operate across a wide range of flow conditions, volumes, and velocities. The amount of electricity generated is a function of the rate of flow and the pressure inside the transmission pipe. For example, in a standard 60-inch-diameter pipeline, with flow velocity of seven feet per second and 92.3 ft of head (40 psi) of excess head pressure, a single LucidPipe unit could produce up to 100 kW of power while extracting about 11.5 feet of head (5 PSI) from the system. One mile of 42” diameter pipeline could produce as much as 3 megawatts or more of electricity.
A second company, NLine Energy, presents a similar energy management proposition: The problem – or opportunity – is inefficient water transmission. NLine notes that for every one foot of elevation difference, water gains .433 pounds per square inch (psi) of pressure. In areas of high elevation difference, it is common to have elevation drops in excess of 200 – 500 feet within a water distribution network. Problems arise for water agencies if pressure accumulates in a distribution system.
In order to mitigate excess pressure, a network of pressure reduction valves (PRVs) has been installed throughout water distribution systems to lower the pressure to optimal levels. Excess pressure, in the form of heat and noise, is vented into the atmosphere. PRVs do not perform useful work with the energy they remove from the system.
To harness this wasted energy, NLine’s Water to Energy Recovery System (WATERSSM) is installed to capture the wasted energy at PRV sites and convert it into renewable electricity. WATERSSM consists of a turbine-generator, energy storage devices, electronic controls, bypasses and fail-safes, environmental and security equipment, sensors, communications and data equipment, and an information collection, control and reporting system capable of operating either manually or autonomously.