Comparing to Solar
An important factor we need to consider is the cost and feasibility of our microhydro system compared to solar power. The Philippines is a tropical island, so it has a lot of access to flowing water and abundant sunshine. And with the cost of solar as low as it is, we will also consider it as a solid possibility for our project.
The Power of Microhydro
A simplified equation to get the power output from a microhydro system is:
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[(net head (in ft.)) * (flow (in gallons/minute))] * (.1) = Power (in Watts)
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Where the net head is the height difference between the water source and the turbine, and the flow is the amount of water flowing through the turbine per second.
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If we assume a net head of 130 feet, a flow intake of 1000 gallons per minute, and an overall efficiency of 53%, we get 1040 Watts of power. Over one year, running continuously, this gives about 9110 kWh of electricity.
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(image from https://www.borgenmagazine.com/micro-hydro-power-rural/)
The Cost of Microhydro
There are a number of required components to create independent DC microhydro generation. Some form of generator is necessary obviously, but this generator does not output usable power. There are also the pipes and wires needed to transport both the water and the electricity to and from the system. A rectifier is necessary to convert the three-phase AC power into DC power, which is then fed into a charge controller which provides a constant output to a battery bank and if necessary a dump load as well. Batteries will also be needed to store the generated electricity for later use.
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The generator and turbine would cost an estimated $1200; the rectifier would be about $20; the charge controller would cost about $150; the batteries would cost approximately $1200; and the water pipes and electric wiring would cost about $600. All in all, the raw cost of these materials for a system which would be capable of producing up to 1 kW is approximately $3200.
The Power of Solar
The Philippines gets about 2100 hours of sunlight per year. A 1 kW photo-voltaic solar system would then generate 2100 kWh of electricity per year. Of course this is also scalable and it's difficult to pin down exactly how big of a solar system we would be comparing to, but we'd like to compare a 1 kW microhydro system to a 1 kW photo-voltaic system.
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(image from https://www.zdnet.com/article/dial-a-photon-cell-phone-and-small-solar-panel-buy-african-power/)
The Cost of Solar
NREL quotes installed DC solar at approximately $2.70 per installed Watt. Add the price of a charge controller, batteries, and wiring and the total for a 1 kW system is approximately $4,400.
The Comparison
For a 1 kW system with similar storage the initial prices do not seem so different. Micro hydro at $3200 and solar at $4400 respectively, maybe solar could be worth the little bit of extra money? After all you don't need to do nearly as much setup work for the same power system. However, solar only converts energy while the sun is shining, giving about 2100 hours of full sunlight equivalent per year. Contrast this with the 24 hours per day or 8760 hours per year that a micro hydro generator is able to operate. This means that you can receive approximately four times as much energy per year from micro hydro as you could from a similarly sized solar installation.
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The result of this is over a 15 year lifespan, the solar will cost $0.14/kWh while the micro hydro costs less than $0.03/kWh, a factor of almost five times. So, while microhydro may be more difficult to implement due to the construction of the water pipes, it ends up being a cheaper option than photo-voltaic solar panels.