By Lise Houston

Natel Energy in Alameda, Calif., is dedicated to advancing hydropower technology to make it more environmentally friendly and cost-effective, as well as flexible enough to be a go-to source of power for operators in rivers of all sizes throughout the U.S. and around the world. With a name appropriately coined from the phrase “natural electric,” Natel is focused on enabling a distributed or decentralized hydropower model featuring systems of smaller projects-– that maintain river connectivity –– networked together as “virtual power plants” or VPPs, as opposed to the current approach of large centralized dams, which can be damaging to wildlife and the adjacent ecosystem.

Founded by Gia Schneider and Abe Schneider, siblings who gained a deep appreciation for the power of rivers and the beauty of their ecosystems during family camping and fishing trips as children, Natel is advancing its vision of “Restoration Hydro,” combining low environmental impact with high economic value. This can be a boon to organizations looking to decarbonize their operations further and transition to a low- or zero-carbon grid.

“More than half of U.S. waterways are degraded, as are countless watersheds, rivers and wetland ecosystems around the world,” noted Gia Schneider, Natel chief executive officer. “With the right technology and attractive business case, the restoration of these critical ecosystems is not only possible but economically justifiable, with a sustainable, distributed hydropower backbone supporting a renewable, decarbonized electrical grid — without the need for large dams.”

Natel Energy has developed a new small hydropower turbine technology that offers an environmentally friendly and compact, modular hydro generation system. This article discusses the technology and its potential future applications.

Fish-safe technology

Natel understood that a huge economic barrier to the practical deployment of renewable hydropower lies in the danger to fish represented by spinning turbine blades. Ecosystem damage can be costly, as is initiating incumbent screening and other mitigation procedures, and permitting can be a challenging process.

Natel’s technical team, led by President and Chief Technology Officer Abe Schneider, rethought and redesigned the conventional axial-flow propeller turbine, creating a new design that features blades with thick and forward-swept leading edges.

“The design creates a pressure zone around the blades’ leading edges that acts like an ‘airbag’ for passing fish, minimizing impacts and allowing them to safely pass through the area,” he explained. The same phenomena also makes the turbine blades more resistant to damage or performance deterioration from entrained debris.”

This design enables fish safety and high efficiency, while also allowing high turbine rotational speeds. At any given head, the Restoration Hydro turbine is similar in diameter, speed and power output to a conventionally designed propeller turbine. However, unlike a conventionally designed propeller turbine, it is safe for fish passage. For example, a 1-MW Restoration Hydro turbine for use at 6 m of head would have a diameter of about 1.9 m and would rotate at about 200 rpm.

This new design would make the turbine nearly universally applicable. Sized suitably, it would allow even small utilities to effectively supplement their power generation mix with clean, reliable hydropower. Further, to make the technology even more practical for prospective power generators, Natel sought to create a turnkey system featuring the new turbine, along with all machinery and equipment needed, that could be offered en masse in scalable sizes to its customers. A search for complementary technical partners began.

Selecting a collaborator

“To do what we wanted to do was not like ordering parts from the hardware store,” noted Abe. “There was a lot of custom engineering work that needed to be done. And we needed a partner willing and able to work with us.”

Abe explained that a key component of Natel’s strategy for a systems approach started with a regenerative variable frequency drive (VFD), which enables the turbine-generator to supply electricity to the grid continuously.

“Not all drives can do this. Many variable frequency drives can’t withstand continuous reverse operation. We found that Danfoss is one of the few industrial-scale VFD manufacturers that is capable of making a regenerative drive that is proven and reliable,” explained Abe. “Their VACON? drive systems are designed, tested, certified and supported to run even up to 100% of the time in regenerative mode.”

Additionally, what made Danfoss stand out even further from the other VFD suppliers Natel spoke with was the company’s willingness to go beyond existing products and put together the system that would help bring the Natel vision of Restoration Hydro fully to life.

“We spoke with a number of quality companies but chose Danfoss due to a mix of their technical expertise and the fact that their team was so proactive and cooperative, willing to collaborate with us,” he said. “Danfoss shared our vision for the future — to create a flexible hydropower system that could be scaled as needed for different customers. They weren’t just looking for a one-off product sale.”

Ultimately, Abe notes, Danfoss brought together technologies that could both handle the speed of the generator and the regeneration of the electricity in one “comprehensive box” — a “packaging” that is a convenience for Natel and for future customers and will help drive commercialization and acceptance.

Installing the new system

In September 2020, the team installed the first system, with a capacity of 300 kW, on an irrigation canal near Madras, Ore., generating power with water from the Deschutes River. This powerplant is owned by Natel, and the power is being sold to PacificCorp under a power purchase agreement.

During the commissioning process, Natel’s engineers were able to rely on technical support from the Danfoss team. “We would do different things and see how the drive responded, looking at all the data. The Danfoss engineers knew their equipment very well and were able to help fine-tune drive parameters over the phone and get it to perform just right. We were very impressed,” Abe said.

“How is it performing? The team got the go-ahead approval from the utility to export power to them and within a day we were at the maximum rated capacity of the plant — 300 kW. And it’s been operating reliably since then.”

Scalability for future systems

Danfoss is able to offer scalability for future systems of various power sizes. VACON NXP inverters and converters are available up to 5 MW in power that use the same software and control interface regardless of power size. Therefore, interfacing, communicating and application programming remains consistent from a small power system to a large power system.

Natel is pursuing nearly 100 turbine deployment opportunities in the U.S., Europe and southeast Asia. In fact, several projects are already contracted or in the negotiation stages, and numerous others are in the pipeline.

“We expect several projects to be under way in 2021, with many more in 2022 and beyond. In fact, our goal is to ramp up to hundreds and then thousands of turbine systems per year,” said Gia. “And with Danfoss supporting us on the drive end, we are confident in meeting — or exceeding — all the goals that we have set.”

Lise Houston is regional manager with Danfoss.

More data on the Danfoss VACON drive

The application discussed in this article uses Danfoss’ NXP family of inverters and converters in a common DC bus arrangement, which enables the NX modules to take energy from the turbine at different speeds and loads. So, as flow naturally changes, energy is generated at variable frequencies, resulting in maximized power and efficiency regardless of whether or not they are at a fixed 60 Hz. This capability is enabled by an NXA grid converter module that can take the fixed DC power created by the NXI inverter module and deliver it back to the grid in a controlled manner. The system also includes an NXB brake chopper module to handle any excess energy anomalies that can occur during operation. All components were easily integrated into the DC common bus system.