What do our minimum measurements represent and how to visualize them?
x1000 each second
First of all, 1 m³/s (cms) is equal to 1 cubic meter per second, 1000 liters per second, 264 gallons per second, 35.3 cfs or cubic feet per second (ft3).
This is the minimal amount of water a Turbulent turbines needs. Most of our turbines will use more water to operate.
But how much is this?
Imagine a 1 liter (32 oz) bottle of water. 1 000 of these need to pass every second through the turbine in order to work.
Not every minute, not every hour, not every day, but every second! Depending on where you live in the world, this may seem like a lot of water or a bit of water. It all depends on the size of the natural environment (rivers) that you are used to living nearby.
This amount of water, 1 m3 or 1000 liter, can also be visualised as a pallet of water bottles, like the pallets in your local supermarket.
How much water is 1m³/s? (minimum requirement)
Head values (height difference):
How much head is 1.5m? (minimum requirement)
First of all, 1.5m of head (height) is equal to 150 cm, 5 feet or 60 inches.
This is the minimal amount the water needs to drop between the upper water level and the lower water level of the micro-hydropower project.
This difference can be a direct drop (waterfall, weir) or a steady drop (cascading rapids) in river or canal.
Most of our turbines will use a larger height difference (so called head) to work.
But how much is 1.5m?
Imagine standing on a paddle board (SUP).
If an adult woman or man is not able to see over the waterfall, the weir or the cascading rapids , it’s a good site.
Hence, when you still can see the upstream part of the river from where you are on your paddle board on the downstream part of the river beneath the waterfall or cascading rapids, it’s not a good site.
To go a bit deeper...
Why do we need a height difference?
Any object with mass m at a height h above the earth’s surface has, what is called, gravitational potential energy U = m . g . h
(g= gravity of the earth = 9,81m/s2)
This potential energy of any object with mass m can be transferred into kinetic energy by releasing the object from its position at height h. It falls towards the earth. We can observe this energy (object picks up speed and hits the floor) and also feel this (a brick falls on your foot).
If we want to extract energy from water in rivers and canals, then water is our object. Water flows from upstream higher level to downstream lower level. Now, if the water nears a site in the river or canal where it suddenly falls down (“a waterfall”), then potential energy is converted into kinetic energy at this site. With a turbine installed at this site, one is able to capture this kinetic energy by absorbing the speed of the water falling down.
There are several technical ways to do this, hence there are different types of turbines and hydropower installations. At Turbulent we developed an ingenious installation with a vortex generator inside a circular basin, which efficiently captures kinetic energy but still allows fish, debris and sediments to pass through the turbine. This is known as environmentally friendly hydropower.
Why do we need at least 1 m³/s and 1.5m height difference?
Turbulent works with nature. Working with nature also means working according to the laws of physics. The natural power P at a site with height difference h and water flow rate Q is the product of 4 factors :
P = ⍴ . g . h . Q
⍴ is the volumetric mass density of water, which is 1 000 kg/m3
g is the gravity of the earth, which is 9.81 m/s2
Nature gives us the mass density of water = 1000 kg/m3 and the gravity of the earth g=9.81 m/s2 , so we have ⍴ . g = 9810, which is approx. 10 000, as a gift from nature to the natural power P that we are able to harness. Basically we get 10 000 Watt or 10kW for free from nature.
To get to the total amount of natural power from falling water we must multiply 10 000 with the water flow rate (Q) and the height difference h. Everybody immediately understands that multiplying with a number lower than 1, either height h or flow rate Q, we would really be wasting the gift of nature, 10 000 (10kW). And, because turbines and generators are not able to absorb and convert all the kinetic energy from the falling water - there will be some efficiency losses and technical constraints - lets keep height well above 1.5 m, and flow rate higher than 1 m3/s