Contents
Site location with measurement positions
i. The volume flow rate of the river
ii. The mass flow rate of the river
iii. The gravitational potential energy lost by the river water each second in the valley.
v. The volume flow rate of Leat 1 – supplying waterwheels 1 & 2
vi. The mass flow rate of Leat 1
vii. The gravitational potential energy lost by waterwheels 1 & 2 each second in the valley.
ix. The volume flow rate of Leat 2 – supplying waterwheels 3 & 4
x. The mass flow rate of Leat 2
xi. The gravitational potential energy lost by waterwheels 3 & 4 each second in the valley.
xiii. The volume flow rate of Leat 3 – supplying waterwheels 5 & 6
xiv. The mass flow rate of Leat 3
xv. The gravitational potential energy lost by waterwheels 5 & 6 each second in the valley.
Total potential for the entire area of the valley surveyed
xvi. The total gravitational potential energy lost through all of the water wheels.
xvii. The proportion of the total gravitational potential energy lost at the water wheel sites
xviii. The potential amount of electricity that could be generated each year
Introduction
The Old Gunpowder Works at Kennal Vale have been untouched since the early 20th century when they closed due to the invention of dynamite.
This report looks at the possibility of the Old Gunpowder Works producing electricity and specifically considers the potential energy that could be harnessed if the water wheels are reinstated with no need to rework any other existing infrastructure.
Due to the location and the dilapidated condition of some of the works a few assumptions were made. Some calculations in this report are estimates but this should not affect the final results significantly. All estimations are clearly outlined throughout the report.
Site location with measurement positions
Figure 1. Map showing the Old Gunpowder Works, Kennal Vale, Ponsanooth.
OS map coordinates for Kennal Vale, Gunpowder Works: SW747372.
Point A – Shows the location of the main river readings.
Point B – Shows Leat 2 this is situated between water wheels 1,2 & 3,4.
Point C – Shows Leat 3 this is situated between water wheels 3,4 & 5,6.
Instruments used
Flow meter – This was used to measure the flow (speed) of the river and Leats.
Meter rule – This was used to measure the depth of the Leats.
50 meter tape – This was used to measure the river and the Leats width and drop.
The River
Figure 2. Showing the river section at Point A.
The following data was recorded at Point A (see figure 1) on Friday the 19th of September 2010. The river was swollen due to several days of heavy rain and this made it too dangerous to record the full width of the river which was 4 meters.
|
Reading |
Width / m |
Depth / m |
Velocity ms-1 |
|
|
(+/- 0.02) |
(+/- 0.02) |
(+/- 0.02) |
|
1 estimate |
0.50 |
0.14 |
1.34 |
|
2 estimate |
1.00 |
0.17 |
1.38 |
|
3 |
1.50 |
0.19 |
1.39 |
|
4 |
2.00 |
0.28 |
1.38 |
|
5 |
2.50 |
0.33 |
0.42 |
|
6 |
3.00 |
0.36 |
0.59 |
|
7 |
3.50 |
0.50 |
0.70 |
|
8 |
4.00 |
0.47 |
0.25 |
|
Mean |
|
0.31 |
0.93 |
Figure 3. River readings Kennal Vale, Point A.
Figure 4. Cross sectional area of the river at point A
i. The volume flow rate of the river
To calculate the volume flow rate at point A the following formulae is used:
Q (Volume flow rate) = W x D x v
W = Width m
D = Depth m
v = Velocity ms-1
Q = 4 x 0.31 x 0.93
Volume flow rate for the river = 1.153 m3s-1
ii. The mass flow rate of the river
m (Mass flow rate) = ρ x Q
Density of water x Volume flow rate = 1000 x 1.153
= 1153 kgs-1
iii. The gravitational potential energy lost by the river water each second in the valley.
Egrav = m * g * ∆h
= 1153 * 9.81 * 30
Gravitational potential energy lost = 339328 Watts
The Leats
iv. Leat 1
Leat 1 was unsafe to access due to erosion and undergrowth. So calculations are taken from Leat 2 Point B.
|
River Measurements LEAT 1 – Taken from Point B on Map |
|||
|
Width m |
Depth (m) |
Velocity m/s |
|
|
1 |
0.20 |
0.120 |
0.00 |
|
2 |
0.40 |
0.125 |
0.00 |
|
3 |
0.60 |
0.138 |
0.24 |
|
4 |
0.80 |
0.145 |
0.26 |
|
5 |
1.00 |
0.140 |
0.31 |
|
6 |
1.20 |
0.130 |
0.39 |
|
7 |
1.40 |
0.140 |
0.32 |
|
8 |
1.60 |
0.145 |
0.30 |
|
9 |
1.80 |
0.155 |
0.21 |
|
10 |
2.00 |
0.150 |
0.09 |
|
Mean |
|
0.139 |
0.21 |
Figure 5. Leat 1 readings taken at Point B.
v. The volume flow rate of Leat 1 – supplying waterwheels 1 & 2
Q (Volume flow rate) = W x D x v
Q = 2 x 0.139 x 0.21
Volume flow rate for Leat 1 = 0.058 m3s-1
vi. The mass flow rate of Leat 1
m (Mass flow rate) = ρ x Q
Density of water x Volume flow rate = 1000 x 0.058
= 58 kg/s
vii. The gravitational potential energy lost by waterwheels 1 & 2 each second in the valley.
Egrav = m * g * ∆h
= 58 * 9.81 * 6
Gravitational potential energy lost = 3414 Watts
viii. Leat 2
|
River Measurements LEAT 2 – Point B on Map |
|||
|
Width m |
Depth (m) |
Velocity m/s |
|
|
1 |
0.20 |
0.120 |
0.00 |
|
2 |
0.40 |
0.125 |
0.00 |
|
3 |
0.60 |
0.138 |
0.24 |
|
4 |
0.80 |
0.145 |
0.26 |
|
5 |
1.00 |
0.140 |
0.31 |
|
6 |
1.20 |
0.130 |
0.39 |
|
7 |
1.40 |
0.140 |
0.32 |
|
8 |
1.60 |
0.145 |
0.30 |
|
9 |
1.80 |
0.155 |
0.21 |
|
10 |
2.00 |
0.150 |
0.09 |
|
Mean |
|
0.139 |
0.21 |
Figure 5. Leat 2 readings taken at Point B.
Figure 6. Cross sectional area of Leat 2 at point B.
ix. The volume flow rate of Leat 2 – supplying waterwheels 3 & 4
Q (Volume flow rate) = W x D x v
Q = 2 x 0.139 x 0.21
Volume flow rate for Leat 2 = 0.058 m3s-1
x. The mass flow rate of Leat 2
m (Mass flow rate) = ρ x Q
Density of water x Volume flow rate = 1000 x 0.058
= 58 kg/s
xi. The gravitational potential energy lost by waterwheels 3 & 4 each second in the valley.
Egrav = m * g * ∆h
= 58 * 9.81 * 5.61
Gravitational potential energy lost = 3192 Watts
xii. Leat 3
|
River Measurements LEAT 3 – Point C on Map |
|||
|
|
Width m |
Depth m |
Velocity m/s |
|
1 |
0.10 |
0.200 |
0.10 |
|
2 |
0.20 |
0.204 |
0.13 |
|
3 |
0.30 |
0.230 |
0.19 |
|
4 |
0.40 |
0.210 |
0.22 |
|
5 |
0.50 |
0.215 |
0.22 |
|
6 |
0.60 |
0.205 |
0.12 |
|
7 |
0.70 |
0.190 |
0.05 |
|
8 |
0.80 |
0.175 |
0.02 |
|
9 |
0.90 |
0.150 |
0.01 |
|
10 |
1.00 |
0.110 |
0.01 |
|
Mean |
|
0.189 |
0.11 |
Figure 7. Leat 3 readings point C.
Figure 8. Cross sectional area of Leat 3 at point C.
xiii. The volume flow rate of Leat 3 – supplying waterwheels 5 & 6
Q (Volume flow rate) = W x D x v
Q = 1 x 0.189 x 0.11
Volume flow rate for Leat 3 = 0.021 m3s-1
xiv. The mass flow rate of Leat 3
m (Mass flow rate) = ρ x Q
Density of water x Volume flow rate = 1000 x 0.021
= 21 kg/s
xv. The gravitational potential energy lost by waterwheels 5 & 6 each second in the valley.
Egrav = m * g * ∆h
= 21 * 9.81 * 5.61
Gravitational potential energy lost = 1156 Watts
Total potential for the entire area of the valley surveyed
|
Water Wheel |
Height of Leat /m |
|
1 & 2 |
6 |
|
3 & 4 |
5.61 |
|
5 & 6 |
5.61 |
Figure 9. Height of the drop from the Leats to the water wheels.
xvi. The total gravitational potential energy lost through all of the water wheels.
Waterwheels 1 & 2 = 3414 W
Waterwheels 3 & 4 = 3192 W
Waterwheels 5 & 6 = 1156 Js-1
Total Leats energy lost /s = 7762 Watts
xvii. The proportion of the total gravitational potential energy lost at the water wheel sites
Total River energy = 339328 W
Total Leats energy lost = 7762 W
Total River / (Total River + Leats) x100
(7762 /(339328 + 7762)) x 100 = 2.2%
xviii. The potential amount of electricity that could be generated each year
At 100% efficiency
Total Leats energy per second = 7762 Watts
Energy = P x t
Amount of Energy for 1 Day = 7762 x 3600 x 24
Amount of Energy extracted in 1 Day = 6.70×108 J
Amount of Energy in 1 Year = 6.70×108 x 365
Total Energy in 1 Year = 2.45×1011 J
Convert from Joules to Kwh 1kWh = 3.6 MJ
2.45×1011 / 3.6×106 = 68056 kWh
68056 @ 30% efficiency = 20416 kWh
According to British Gas 0.15p is the average price per kWh
15 x 20416 = £306240
Brief report
The fieldtrip conditions on the day the measurements were taken, meant that accessing the river and Leats were difficult. This was due to high amounts of rainfall affecting the width and flow of the river, thus making accurate measurements of Leat 1 and the River dangerous.
The first measurements were recorded at Leat 2 as Leat 1 was inaccessible. It was decided as both Leats have similar characteristics that these measurements would also be used for Leat 1.
The width of the river was recorded using a 50m tape and the flow meter was placed at 0.5m intervals underwater around half the depth of the river. This data was recorded (see figure 3.) only to the first three meters as the river was too dangerous to proceed any further. The remaining width of one meter was estimated.
The Leats were measured using a 1 meter rule and the flow meter was placed at 0.10m intervals along the rule. The flow readings were recorded at approximately half the depth of the Leats.
The Leat heights were again estimated as they were inaccessible due to erosion and weather conditions.
Conclusion
The validity of the results cannot be relied upon as there is so much room for inaccurate recording. This is due to several factors including human error, conditions on the day and the inaccessibility of the surrounding area.
If the Leats were reinstated to their original condition this would allow much more potential to produce electricity and gain more financial impetus.