Steerable rock-drill digs uphill and in curves
Construction of hydroelectric power plants generally means high environmental impact. One aspect is the need for the creation of destructive roads from the bottom to the top of valleys. An alternative to such roads is to start drilling at the bottom of a valley, going upward. Nevertheless, such drilling is very difficult using current equipment, which is prone to breakage and jamming. Repairs are expensive and time-consuming. The EU-funded ECO-DRILLING project developed equipment suitable for such drilling applications. The concept is a new technology that permits drilling of a tunnel 0.5 m to 1.5 m wide over long distances in controlled curved pathways, including upward. The team developed the concept to the prototype and commercialisation stages. The drill is intended for boring penstocks, which are important parts of hydroelectric power stations. A penstock leads water from the intake in a river or reservoir to the generator turbine in the powerhouse. The project’s drill system is suitable for ‘high-head’ power plants. Such plants feature high pressure – due to the steep angle between the water source and turbine – and limited water flow.
Electric drill
“The ECO-DRILLING solution incorporates an electric drilling motor directly attached to the drill bit,” explains project coordinator Askjell Tonstad, CEO of lead project partner NORHARD. “It also includes a non-rotary drill string, which minimises the friction between the drilling string and the rock.” This helps the system achieve high energy efficiency. Since the system uses a non-rotary drill, cables for energy transmission and high-capacity data exchange can be attached to the drill string. This allows the drill head to be operated and steered by an operator on the surface. Integrated with the drill head is a laser-optical gyro unit, which provides advanced positioning and navigation capability. The steering is accurate to 1 metre per kilometre drilled. Thus, the operator can drill along predefined trajectories including curves. The project also developed an efficient software system for monitoring, control and operational support.
New possibilities
Other advantages of the ECO-DRILLING system include its modular form, which makes it transportable in pieces along basic roads or via helicopter. This feature eliminates the need for extensive road infrastructure, saving costs and minimising environmental impact. Researchers substantially improved both the technology and the system’s operational performance. Prototype testing demonstrated increased range of drilling distance and better mobility compared to earlier versions. Many small hydro plants have been planned for construction in Norway. The ECO-DRILLING technology now makes them technically, economically and environmentally feasible. “We plan to take advantage of the situation to build up capacity and strengthen our already-strong position in this market and utilise this platform in our further internationalisation process,” adds Tonstad. The team negotiated a 6-year agreement with one of Norway’s major builders and operators of small hydro plants, for the supply of a complete drilling unit. Construction of the new unit will commence immediately post-project in 2020. Researchers also plan to introduce the technology to other tunnelling and underground infrastructure markets such as district heating, underground cables, water supply and waste water. Building hydropower stations in an environmentally friendly way will foster the increased production of clean hydropower. This will help the EU meet its renewable-energy goals.
Keywords
ECO-DRILLING, drilling, electric, upward, hydropower, penstock, steerable, low-impact, curves, hydroelectric
