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Technical Analysis & Presentation Essay Example
 Category:Engineering and Construction
 Document type:Article
 Level:Undergraduate
 Page:1
 Words:735
MicroHydro System
The objective is generation and storage of electrical energy in very efficient and manner and the system should be cost effective. This involves creating a dam on a creek where water accumulates. Periodically water , at a controlled flow rate, is to be directed through pipe to a turbine so that there is to be generated electricity that will then be stored in batteries.
The components to be looked at are as follows

A concrete dam that is constructed across a valley where a creek currently flows

Water delivery to turbine consisting of pipe work and nozzle

A Pelton Wheel turbine

An electrical generator

Battery Storage

Filter, enclosures and ancillary fittings
Dam location and sizing
The source of water to be utilized to generate power is a permanent creek which flows through a valley on the property. The flow rate of the creek varies with seasonal rainfall, but the lowest average flow rate (to be used for all design calculations) is 5 L/s. The valley is approximately semiconical in shape, where the slope of the valley of 30 degrees defines an angle of the cone. The minimum depth of the dam must be 1 m to allow for an intake filter. The dam wall is keyed to be keyed into the slope in a trench 0.5 m deep.
The thickness T of the dam wall is calculated from
T=R/50+0.1 where are is the dam radius including key of 0.5m
R is the maximum height of the dam to be used which is given as 8.5 that includes the key of 0.5m
Therefore T=8.5/50+0.1= 0.27m
Calculating volume of water
Maximum height of water = Maximum dam height (H) –key (0.5) –dam thickness (0.27)
=8.5 0.50.27=7.73m
Volume of water = _{}
Where h is the height of the cone half of which gives the maximum water volume
Setting Q
Choosing a discharge of _{}
At this discharge and using a total volume of water per day of 432m^{3}
Total time of pumping will be = _{}
USING a discharge value 0.2
Total time of pumping will be = _{}
Using the 65mm diameter pipe velocity in pipe is calculated as
Area A of pipe = _{}
Velocity v=0.01/0.003317=3.0m/s (for 0.1 _{})
Using the same procedure the velocity were calculated in excel and are as in table below
Diameter 
Area pipe 
Headloss/m 

0.003317 
3.015113 
0.11376717 

0.006359 
1.572698 
0.02332083 

0.010382 
0.00706816 

0.015386 
0.649942 
0.00271182 
From the table the best pipe would be the 65mm diameter pipe as it has relatively moderate speed and is the cheapest
Total pipeline length = _{}
Head loss using headloss/m of 0.11m/m = 72.2×0.11= 7.9m
Total head H = s*Sin 30 =100sin30 = 50m
Thus available head at nozzle = 50m7.9m = 42.1m
Establishing nozzle velocity u
Using Q=0.02_{}
Velocity v=0.02/0.003317=60.3m/s (for 0.02 _{})
Using the same procedure the velocity were calculated in excel and are as in table below
Diameter 
Area pipe 
Headloss/m 

0.003317 
6.030227 
34.03028595 

0.006359 
3.145396 
6.975777572 

0.010382 
1.926481 
2.114244273 

0.015386 
1.299883 
0.811166696 
From the results in table 2 it can be seen that a discharge of 0.02_{} results to very high head loss that cannot be accommodated over the 72.2m length pipeline. We proceed with 0.01_{}
Selecting turbine
The relationship between peripheral velocity of the turbine u and the diameter of the turbine is given by
Where N is rpm and D is the diameter of the turbine to be used
For optimal performance of turbine u is to be 48% nozzle velocity (approximately half of nozzle velocity)
Thus with nozzle velocity of 28m/s u=14m/s
The ideal rpm of the turbine is to be 2000 to 7500rpm and for this case we choose a speed of 2000rpm
Now using this parameters and substituting in equation above
This shows that the 125mm diameter turbine is suitable for use but it will operate at a higher speed above 2000rpm
The speed of operation when 125mm turbine can be calculated from
can be can calculated using the 1
This shows that 125mm turbine is suitable since the speed of 2140rpm is with the recommended range of 2000rpm and 3000rpm
The lower speed is also suitable because it ensures that the rate at which the turbine is wearing out is low.
Power output from turbine
Assuming maximum power output of 90% from turbine we have
Turbine power = _{}
Electric generator selection
The maximum power output from generator =_{}
This shows that the smallest electric generator will be suitable