Hydro Turbines

Green Energy > Hydro Turbines

Water is a renewable energy source that’s hard to beat

Modern day hydro-power systems, like the water wheels of old, harness the force of flowing water by channelling it through a turbine (water wheel) and converting the resulting movement, via a generator, into clean and renewable electricity to run appliances, charge batteries or add to a power grid.

Small-scale (micro) hydro turbines refer to systems with an output of 100kW (100 electrical units per hour) or less which rely on a source of naturally running water situated reasonably close to the user. The need for nearby water inevitably prevents their use in the majority of locations, but where geography allows small scale hydro turbines can generate impressive amounts of energy and provide a good financial saving in comparison to other renewable technologies.

Power and payback

The power and efficiency of hydro power is largely governed by the flow rate of the water (per second) and the height (or head) from which the water flows. The distance from the water source to the end-user point, and the size of the turbine, are also important factors.

The actual output will depend on how efficiently the turbine converts the power of the water into electrical power. Maximum efficiencies of over 90% are possible but for small systems 50% is more realistic. Renewable Energy UK explains in more detail how to calculate the potential power of a proposed location.

Hydro electric systems are generally divided into three categories of low, medium and high head. For medium heads, there’s a fixed cost of around £10,000 and then about £2,500 per kW up to around 10kW. A typical 5kW domestic scheme might cost from £25,000 for an average home, though this may vary depending on the site and the equipment used. (See here for more information.) Costs fall in proportion to the increased size of the project, and of course there are grants available. NIE incentives include a grant of up to £5,000 (£1,000 per kW).

A typical standalone (non grid-connected) 5kW domestic project, with an initial outlay of between £20,000 and £25,000 (excluding external financial assistance), might expect to enter a payback period of around 10 to 12 years. Larger projects can expect a proportionally quicker return however the payback time will depend on the size of the project, it’s location and the price of electricity. The payback time for a grid-connected system, which exports power to the grid, will be shorter. Some useful information can be found here.

The pros and cons

Hydro power is generally low maintenance, long-lasting (typically 25 years) and a great option for remote locations that are off the grid. Small hydro power systems can generate up to 100kW of electricity, which beats the capabilities of wind and solar power, and their positioning at ground level minimises the aesthetic impact.

Hydro energy produces power at all the right times, maintaining consistent output during the winter when demand for heating is highest. It also continues through the night, enabling users to reliably charge batteries overnight and more accurately predict long-term payback.
On the downside, turbines can be noisy and the initial outlay expensive, but the biggest drawback to hydro power is the need to be close to that critical source of flowing water.

In the end

Micro hydro systems are neither cheap nor quick to install, but for those who have the vision to think long term (and also have a nearby water source), the rewards can be considerable. Compared to other renewable technologies, hydro power offers the most consistent and reliable source of good, clean energy. It’s a realistic alternative to the grid and helps to substantially reduce greenhouse gas emissions, while grid-connected users can further enjoy the feel-good factor of transforming their electricity bills into invoices.