The hydropower sites which are easiest to exploit are those with a big height difference between water levels at either sides of the barrier.The higher the build up of water, the greater the pressure and the more kilowatts of energy generated. This height difference is known as the ‘head’ height. Systems with higher heads tend to be very economical, but we’re running out of suitable sites in the UK. In spite of the big appetite for small, local low head hydropower sites, in the past technology has not been available to harness the energy created at these sites effectively. The water often runs too slowly to generate electricity alone, and therefore requires a gear box. The increased number of moving parts makes these systems expensive to maintain, and prone to difficulties. Hydroventuri have developed a unique air turbine suitable for use at low head sites.This system is much simpler, has a lower capital cost, a lower running cost and is far less likely to go wrong. Hydroventuri Ltd are currently working on a test site in Derby, and hoping to usefindings from tests conducted there to inform a larger project in the Orkneys.