In rural areas where there is no electric grid, operating cell towers can be an expensive venture requiring diesel-run generators. Even when there is a nearby grid available, the costs to connect these sites can still be high. Because of the sparse population, the economics of wireless coverage in rural areas are already tenuous.
To meet these challenges, Crossflow Energy, a leading clean energy technology company based in the UK, has developed a cell tower with a unique wind turbine that is integrated with battery and solar technology to create an autonomous hybrid energy system. Known as the Eco Tower, it combines the complementary benefits of wind and solar to maximize clean energy generation and reduce the operating expenses of the tower.
“Although you will always need a backup generator, what we’re trying to do is minimize refuelling,” explained Rebecca White, Commercial Director, Crossflow Energy. “That’s where the Eco Tower fits in and makes real economic sense.”
For maximum economic benefit, the Eco Tower is ideally deployed in off-grid, new-build sites, or in places where there is a weak or unreliable grid, but where wind and solar resources are adequate. The Eco Tower can provide 100 percent of a tower’s power, with at least 80 percent coming from clean energy generation on a small rural site. Wind and solar can be used to keep the battery charged and then the balance of power can come from the grid, a diesel generator, biofuel, a fuel cell, or even a micro turbine genset.
“At some of the sites we’re seeing in Europe, we can reach almost 100 percent renewable energy generation,” White said. “Those sites save on the costs of both the fuel and the logistics associated with fuel storage and fuel transportation. The reduction of carbon, whether it is direct emissions or the supply chain’s emissions, is increasingly important to the telecom sector.”
The Differentiator
Many small wind turbines are designed like windmills and operate at high speeds, which can cause fatigue issues and costly failures when used to power remote tower sites. That challenge is what inspired the development of the Eco Tower. It uses a Savonius design, which is typically a vertical-axis wind turbine used for converting the force of the wind into torque on a rotating shaft, although the Eco Tower uses a horizontal axis.
It is the Eco Tower’s highly reliable, yet simple design with low rotational speed and minimal vibration, that addresses any primary operational, maintenance, footprint, environmental or ecological concerns associated with conventional turbine technologies used in the telecom sector.
The Crossflow Energy turbine rotor incorporates a patented asymmetrical S-shaped shield, designed to create a low-pressure area behind and below the rotor that encourages the wind to travel though the turbine rather than around it. The hybrid lift and drag aerodynamics, combined with the shield, enables the turbine to be significantly more efficient than existing slow rotating turbines, and comparable in terms of energy output to high speed turbines.
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“We want reliable robust wind turbines that can be put in remote environments,” White continued. “Slow rotation results in less wear and fatigue on the whole structure. It has a regular maintenance interval of 12 months, with a major maintenance interval of five years.”
Along with reducing breakdowns, the low speed of the Eco Tower wind turbine means it cannot be heard above the sound of the wind. “That helps us to get planning acceptance,” White said. “The ‘solid’ design of the wind turbine also means that it poses no threat to birds and bats and is filtered out by radar as static clutter.”
Managing the power output of a wind turbine can be a challenge because of the variable speed of the wind, and therefore the energy generated can fluctuate hugely, according to White. “Anyone can buy a small wind turbine, but getting the most out of that wind turbine, integrating it with other generation and storage technologies, and managing its power output is where the real challenge lies,” White explained. “We’ve worked really hard to manage the transient output from the wind to seamlessly integrate it as you would any other energy source,” she said.
To make a compelling business case for a wind turbine in a particular location, an annual average wind speed of about 13-14 MPH is needed. To decide whether a certain location is appropriate for the Eco Tower, the power curve of the wind turbine, the 20-year historical wind data on that site and solar radiation data are plugged into micro grid software. This will provide the expected energy generation on a monthly basis over the course of a year, which is then compared with the power demand of the site.
“Users of the Eco Tower will be able to see, for example, that with a site that was traditionally powered by a diesel generator, how much renewable energy they would get and how much less diesel fuel they would burn. Additionally, the calculations will show the reduction in carbon dioxide emissions at the site,” White said.
Conclusion
While the Eco Tower can get a great deal of its power from the wind, Crossflow Energy has developed an Integrated Renewable Energy System, a modular energy management system that is technology agnostic. It can integrate and manage the output of any small energy generation source, whether it is a wind turbine, a fuel cell, a biofuel generator, a solar array or the electric grid. Using multi-generation sourcing allows the most renewable energy to be captured to power the site. This stand-alone solution is complementary to the integrated Eco Tower solution and is aimed at sites with higher loads or the retrofit of existing sites, providing a highly renewable, reliable, and very competitive off-grid energy solution compared to others on the market.
“At the end of the day, what the end user wants is maximum generation of clean energy, and they want it multi-source, as much as possible, to displace the burning of fossil fuel. You need to harvest and use all the clean energy you can,” White concluded.
For more information, contact Crossflow Energy: https://crossflowenergy.co.uk/contact-us/.
By J. Sharpe Smith, Inside Towers Technology Editor
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