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Applying micro-hydro power generation
Sunlight and wind are seen as key providers of renewable energy, but what potential does naturally flowing water have to provide green power?
what about harnessing the power of rivers and streams? In appropriate locations, hydro- electricity can provide a highly cost-effective solution with low maintenance requirements. This article offers an introduction to the use of hydro and an overview of the mechanical side of micro-hydro power generation.
T
Hydro-electricity Hydro-electric power generation may be broken down into four general categories according to power output: • 10MW: full-scale hydro • 300kW to 10 MW: mini-hydro • 50W to 300 kW: micro-hydro • Under 50W: pico-hydro Of the 170 hydro schemes currently receiving payments under the FIT scheme, all but three are micro-hydro schemes. One of the key attributes of micro-hydro schemes is that only a portion of the waterway’s flow is used to generate power, so allowing the normal ecological activities to continue with relatively little impact. The planning rules guided by the ‘Good practice guidelines to the
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he introduction of feed-in tariffs (FITs) in the UK has given a boost to the installation of solar panels and wind turbines to generate electricity. But
Environment Agency hydropower handbook’1 strive to ensure that the environment is largely unaffected; and unlike solar and wind power, the resulting electricity will be produced 24 hours a day (although the amount may vary with season).
The systems can supply DC (for battery charging) or AC (powering appliances) for ‘off-grid’ use, or they can feed back into the grid (just as with photovotaic panels and wind turbines). A micro-hydro system may be as simple as a ‘zero-head’ propeller-type device close-coupled to an encapsulated generator submerged in a free-running stream providing power for riverside lighting. This would require no particular civil engineering infrastructure and only very basic, low-cost electrical conditioning equipment to provide power for charging batteries. However, most micro-hydro systems divert part of the flow from the waterway (stream or river) to pass through a turbine and then return the water (still using no reservoir of water). These are known as ‘run-of-river’ schemes and require some civil and/or mechanical engineering works. Water flow rates of less than 0.5 litres per second (l/s) with a ‘head’ of water as low as 1,000mm can usefully produce power.
Hydro power generation The total amount of electricity generation capacity in the UK from hydro power (reservoir and run-of-river schemes) is nearly 1.5GW.2
This is just under 1.5% of the
UK electrical power requirement, and it is estimated that there is potential to increase this to 2.5%. As an indicator of potential, the recently published Hydropower Resource Assessment Report identified (Figure 1) far more suitable sites than were previously thought feasible in England and Wales. In October 2010 the UK government announced that ‘remanufactured equipment’ would also be eligible for FITs, so long as this equipment had not been generating energy after 31 March 1990. This opens up the potential use of disused installations that were previously associated with mills and industrial sites that, before the introduction of FITs, had not provided an economically feasible proposition. The generation tariff for hydro installations (that have been installed under the auspices of the Microgeneration Certification Scheme) is shown in Figure 2. To put this in some context: the total cost of installing a system producing, say, 5kW might be around £25,000. There is an economy of scale here, as much of the basic
February 2011 CIBSE Journal
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