CPD Programme 100
64 50
32 25 16
10 8
5 4
3 2
1.5 1
1
Chart created by John Curzon-Siggers derived from performance data published by manufacturers
1.5 2 3 5 6 7 10 Water fl ow rate in litres/sec Head-fl ow ranges for micro-hydro turbine, with electrical output Figure 3: Turbine performance for micro-hydro installations
distance from the turbine to the bottom of the draft pipe where the water is released back into the stream through the tailrace. The static head can be determined by using topographical maps or preferably, for design purposes, by practical onsite measurements. The potential generating power from a
hydro generation plant is established by calculating the energy released by the falling body of water of mass, m (kg), over a height, h (m static head) Energy = m⋅g⋅h = ρ⋅V⋅g⋅h (Joules) Where ρ = density of water (kg/m3 volume water (m3
), V = ), and g = acceleration due
to gravity, and so the power (watts) associated with fl owing body of water will be determined by the volume fl owrate of water, Q (m3/s) and so Power = ρ⋅g⋅h⋅Q (watts).
This is the potential power available from
the fl owing water dropping over a head, h, but real installed systems will have losses due to friction in the trash rack, Penstock, etc., turbine effi ciency and generator effi ciency. The overall efficiency of a system would normally range between 40 percent and 70
www.cibsejournal.com
percent. A well-designed system will achieve an average effi ciency of 55%.
Pnet = η⋅P = η⋅ρ⋅g⋅h⋅Q (watts), where η is the ‘effi ciency’ of the overall water, turbine and electrical generator system
And substituting in standard approximate values for ρ and g
Pnet = η⋅10⋅h⋅Q (kW) So, for example, taking 50 litre/s fl ow from
a stream with a head of 3m @ 50% overall effi ciency would provide the power = 0.50 x 10 x 3m x 0.050m3/s = 0.75 kW and assuming that this fl ow is constant throughout the year, the potential yearly energy in kWh would be 0.75kW x 24 hrs/day x 365 days/yr = 6570kWh/yr. This could meet the electrical power requirements for a small family house. © Tim Dwyer
Further reading This article has outlined the principle sections that make up the mechanical side of a micro-hydro installation. There are some excellent free resources available to provide
a thorough grounding in the complete application of micro-hydro technology. Examples are: A Guide To UK Mini-Hydro Developments, British Hydro Association,
www.british-
hydro.org; Micro-Hydropower Systems – A Buyers Guide, Natural Resources Canada; and Guide on How to Develop a Small Hydropower Plant, ESHA 2004,
www.esha.be/ To see a practical implementation of a micro-hydro installation employing a Kaplan turbine, visit
www.youtube.com/ watch?v=4teOp0YYmwY
References 1. Good practice guidelines to the environment agency hydropower handbook, Environment Agency, 2009
2. England and Wales Hydropower Resource Assessment, DECC October 2010
3. Micro-Hydro Systems, Centre for Alternative Technologies, 2010
www.cat.org.uk/information/pdf/ MicroHydroSystems.pdf
February 2011 CIBSE Journal 57 15 20 30 40 50 60
approx. electrical output in watts 3200w 1600w
800w 400w
200w
100w
Single nozzle Pelton wheel
2 nozzle Pelton Turgo wheel manufacturer A 4 nozzle Pelton
Turgo wheel manufacturer B
Banki-crossfl ow 180mm wide
Banki-crossfl ow 300mm wide
Water head in metres
Page 1 |
Page 2 |
Page 3 |
Page 4 |
Page 5 |
Page 6 |
Page 7 |
Page 8 |
Page 9 |
Page 10 |
Page 11 |
Page 12 |
Page 13 |
Page 14 |
Page 15 |
Page 16 |
Page 17 |
Page 18 |
Page 19 |
Page 20 |
Page 21 |
Page 22 |
Page 23 |
Page 24 |
Page 25 |
Page 26 |
Page 27 |
Page 28 |
Page 29 |
Page 30 |
Page 31 |
Page 32 |
Page 33 |
Page 34 |
Page 35 |
Page 36 |
Page 37 |
Page 38 |
Page 39 |
Page 40 |
Page 41 |
Page 42 |
Page 43 |
Page 44 |
Page 45 |
Page 46 |
Page 47 |
Page 48 |
Page 49 |
Page 50 |
Page 51 |
Page 52 |
Page 53 |
Page 54 |
Page 55 |
Page 56 |
Page 57 |
Page 58 |
Page 59 |
Page 60 |
Page 61 |
Page 62 |
Page 63 |
Page 64 |
Page 65 |
Page 66 |
Page 67 |
Page 68 |
Page 69 |
Page 70 |
Page 71 |
Page 72