Water has been a source of energy for thousands of years, from the water wheels used by the ancient Greeks to the colossal hydropower dams in South America and China. Dams that use a stream of water to turn a turbine and create electricity are common around the world, producing zero-carbon, reliable power for cities. Hydropower is now the largest source of renewable electricity in the world, accounting for 1,200GW of installed capacity, or 17% of global electricity.
However, there are vast networks of water that until recently have been ignored as a source of potential power. Cities and towns have miles of drinking water and sewage pipes running beneath them; in the US alone, there are 1.2 million miles of drinking water pipes.
Now, micro-hydropower technologies are beginning to harvest the energy from these networks using specially designed in-pipe turbines. Portland-based company Lucid Energy is generating power in several US cities using its micro-hydro, in-pipe turbine systems, called LucidPipes. These can replace pressure-release valves in drinking water networks, capturing energy that has previously been wasted.
In 2015, Lucid became the first micro-hydro company to sign a power purchase agreement, and began selling its energy to the grid. This is a big step forward for micro-hydro, which has previously been used predominantly in trials or on a small scale, generating energy to offset water suppliers’ large energy demands.
Utilising the water that flows beneath our feet seems like a no-brainer, but can we expect the technology to take off?
Simple, efficient turbines
In-pipe turbines can be placed in gravity-fed water networks, common in towns and cities where reservoirs are used for storage. As the water travels through the system it builds up a lot of speed, creating pressure. Currently, this is controlled using pressure-reduction valves, which release the energy potential as heat, wasting it instead of capturing it.
Technology systems like the five-bladed LucidPipe can be placed at these valves. As the water travels through the spherical turbines, they spin, turning a generator and creating electricity.
Jonathan Fink, vice president for research and strategic partnerships at Portland University, told The Guardian that the LucidPipe technology is “pretty much a win-win”. “Like a lot of cities, water coming into Portland is gravity-fed, and [the water utility has] to slow down the water as it comes down the hill. Typically, the energy [of the rushing water] is lost as heat. With Lucid’s technology they can convert it into electricity,” he said in 2015.
Whilst seemingly a simple concept, the importance of water networks means that these turbines must not affect supply or transport in any way. Lucid claims its technology does not impede the movement of water, and can continue turning 24 hours a day, at a constant rate.
The city of Portland in Oregon began using LucidPipes in 2015, as part of a $1.7m project. There are now 50 pipes installed in the city, generating 1,100MWh of electricity annually. This is enough to power roughly 150 homes in the city.
Elsewhere, a number of companies have developed and tested similar in-pipe technologies. Soar Energy has installed turbines in Oregon and Hawaii, whilst Halifax in Nova Scotia became the first Canadian city to take advantage of in-pipe hydropower in 2014. It installed a system capable of generating 32kW within a drinking water distribution control chamber, which powers around 30 homes and generates $29,000 in revenue annually.
In Richmond, Utah, New York-based Rentricity successfully completed a trial of a micro-hydro turbine within an irrigation system in 2017. “The addition of the microgrid to generate power from the pressurised irrigation water while continuing to serve our shareholders just made perfect sense!” said Terry Spackman, president of Richmond Irrigation Company.
In Europe, Scottish Water launched a £20m in-pipe hydropower scheme in 2012. Turbines were placed in water and wastewater treatment plants, lowering the power cost of water treatment by 10%.
A clean and consistent opportunity
As the world becomes increasingly urbanised and the demand for energy grows, even small-scale renewable sources of power are increasing in demand. Whilst micro-hydro may not provide the big payloads of hydropower dams, it offers a local solution that takes full advantage of previously wasted resources.
Most of the projects in place around the world use the energy generated to offset that required by the water systems’ operations themselves. 20% of the electricity consumed in California, for example, is used by the state’s water sector, where it is needed for groundwater pumping, water treatment and water recycling.
The large energy requirements of the water sector are costly and can place a strain on grid systems, many of which are already struggling with increased demand. It is hardly surprising, therefore, that companies such as Scottish Water have turned to in-pipe micro-hydro technologies, along with wind and solar, to compensate.
Unlike large-scale projects, micro-hydro doesn’t have a detrimental impact on local environments. Despite being a carbon-neutral source of power, hydropower often comes under criticism for damaging the ecosystems that surround dams by diverting water and altering water planes.
Hydropower is also expected to falter in coming years, as the world becomes hotter and droughts more common. African nations in particular are predicted to suffer devastating blackouts if they continue to rely heavily on large-scale hydropower. As such, diversification to include technology such as solar and wind, but also small-scale technologies like micro-hydro, will be essential for energy security.
With just 50 LucidPipes, the company is able to power 150 homes. There are, however, almost 300,000 households in Portland, so to power the whole city using these turbines would require 100,000 systems; combined, these could place a strain on water pressure levels, an effect that would be exacerbated in even larger cities.
This issue could result in micro-hydro never becoming a major power source, but the technology could undoubtedly play an important part in the energy mix. As demand grows, scavenging as much waste energy as possible will increasingly become a necessity. Micro-hydro provides an opportunity for carbon-neutral power that is consistent and predictable, should water networks choose to retrofit.