AMJET Turbine Systems, LLC (ATS) has utilized composite marine water jet technology to create a new low head hydro turbine/generator. Low head hydropower (axial flow) is the inverse of a marine water jet. ATS has a sister company, American Hydro Jet Corporation (AHJ), that has designed and built water jets for large yachts, see figure 6 below. The flow direction and rotation are reversed but mechanical loads, stresses and hydrodynamics are the same and basic construction developed by AHJ is now used by ATS.
When ATS observed the present state of hydropower design and was considering entering the field, the common response was that Hydro was a Mature Industry and for any chance of success we better think “Outside the Box”. A review of the industry revealed that it consisted of many “boxes patched together” that produce a heavy weight system with large footprint and heavy foundation and powerhouse, at high cost. (Fig.1 below) The ATS approach became to search out different technologies and combine them and avoid the traditional “boxes”, thinking “Inside the Box” and create ONE BOX containing all mechanical, hydrodynamic and power generating functions of these traditional boxes and simplify these functions by reducing the number of moving parts to ONE.
Eliminating
mechanical flow controls: wicket gates(8) and controllable pitch runner(1) the related hydraulics(6), the gear speed increaser(3), a separate generator(4), the generator coupling(5), the governor and synchronizing switch gear(7), civil works and heavy foundation to support and hold in alignment all separate components(11), overhead crane to lift, install and service components(9) and a powerhouse building to contain all of the above(10).
Reducing
mass and footprint 3X to 5X; time to replace or service to ONE day with built-in lifting guide(12); cost and weight by composite construction for lower; mass produced, with per-application power selection at final assembly.
The hydrodynamics of a given turbine can change flow rate in 2 ways
- Change rotational speed (the AMJET way) or
- Change diameter of the turbine (Conventional way). Every varying application requires a different turbine diameter.
- Every turbine needs the capability to change flow rate to adapt to actual dam requirements. The conventional way is by adjusting mechanical hydrodynamic surfaces to lower flow requirements to maintain constant speed but with loss of efficiency.
BENEFITS
- Instant electronic synchronization
- In-line flow-through design, for shorter time, more compact and efficient installation
- Simple support structure for servicing/replacing in one DAY
- Up to 5x lower weight and 5x smaller footprint
- Composite construction of structural turbine parts
- Reduced dam civil engineering and construction costs
- Shorter dam installation time
- Modular design enables volume production and power level selection at final assembly.
- Operates above or under water at any angle of operation
TRADITIONAL SYSTEM
The constant speed requirement relating to the generator matching the grid frequency operates in phase-locked manner. Therefore only one optimal set of performance point specifications (sweet spot) exist with all other lower performance parameters taken as a function of this optimal performance point. To match all other operating conditions, flow direction-altering mechanical controls namely runner pitch control and stator pitch (wicket gate) control are used, driven by a governor, that lowers turbine efficiency. The governor also sets rotational speed for synchronization.
AMJET VARIABLE SPEED SYSTEM
The variable speed system relies on a fixed optmimal hydrodynamic design that operates at high efficiency at any runner speed. The electronic torque control, part of the DC rectifier, controls the rotational speed to obtain maximum efficiency at any head (max. current at max. voltage). Therefore the performance curve uses head (horizontal axis) as the master variable and output, flow, rotary speed, torque and efficiency as the dependent variables (vertical axis). See chart below of the ATS-63 with head horizontal and Power (kW), Flow (cfs) and Efficiency (%) on the vertical scale
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