Green Energy Solutions

Using a rotodynamic pump running in reverse, as a cost effective and very efficient form of hydroelectric generation, is an excellent way to recover energy from flowing water. Hydraulically, such a pump operating as a hydro-turbine can handle a higher volume of water than when operating as a pump. This increased unit volume flow inside the pump results in a higher quantity of water kW than can be produced when operating conventionally as a pump. Thus (when running in reverse operation as a turbine) the machine operates at a higher efficiency. A rotodynamic pump is therefore a very useful hydro-turbine, utilising well proven existing technology.

Using conventional pumps as turbines economically facilitates between 20 kW and 500 kW of electricity to be generated, which can be used locally, or fed back into the grid network reducing the overall cost of energy for the user. Equipment in this generating range are defined as “micro hydro systems” and are used for both industrial applications and to supply small communities. The primary advantage of such systems, when compared to other renewable energy technologies,  is that they can provide a constant and/or predictable power supply, whereas other technologies (specifically wind and solar power) provide intermittent or unpredictable energy.

Bedford Pumps Ltd's Fish Friendly range of pumps and turbines, operating in the head range 1-12m with flow rates 0.3-5.0 m³/sec, are a compact, efficient alternative to Archimedes Screw type pumps and turbines. The machines incorporate an integral induction motor/generator, hence substantially reducing the size of the civil footprint required for a micro hydro system. The pump and generator have an ingress protection level of IP68, thus are totally flood proof and indeed submersible.

“Fish Friendly” Pump / Turbine Design Philosophy

Although ill-defined, the term ‘Fish Friendly’ implies a machine which avoids or minimises damage to aquatic fauna. In order for the migratory eel to pass through any form of rotodynamic pump, it is recognised that conventional pump/turbine designs require substantial modification and the range and extent to which a pump can be utilised is in fact relatively narrow. The particular elements within the pump to achieve these aims is obviously subject to company intellectual property, but can be briefly summarised as follows:

To achieve a Fish-Friendly status, the essential elements for pumps include:

• Relatively low impeller peripheral speed.
• High hydraulic-efficiency. Energy loss into the fluid causes erratic stream-lines, adverse pressure gradients and turbulence imposing unnecessary shear-stresses.
• Substantially increased spatial clearances between the impeller and guide-vane casing. Any static vane, of whatever angle that is located closely behind the rotating impeller is a potential shearing surface and threat to fish.
• Internal areas which might trap debris are to be avoided. Static diffuser vanes should be so designed as to not trap vegetation and other suspended solids.