Interview with Sara F. Hathaway, Book “Day after Disaster”

 

 

Episode 13

Why are hydroelectric generators so highly recommended?

Micro-hydro is one of the most efficient forms of electrical power generation.

Lowest Cost per Watt of any other power generation.

It is fairly easy to predict what your output would be year round, which can result in smaller battery sizes.

They do have some problems:

It only provides power with good flow with a decent amount of head pressure, which means it will cause problems for low flow or low elevation locations.

Often I have seen that the spring or river needed is a long distance from the home it is meant to power.  This gets extremely expensive with wiring because copper is so expensive

They are mechanical in nature, so they do break after a while.

What are the basic mechanics of hydroelectric generators?

Water is used and directed into blades called a turbine.

The turbine spins and is connected to a shaft which spins a motor, sometimes direct coupled and sometimes using belts for converting low speed high torque inputs to high speed low torque outputs to the motor.

How is the power converted from the generator to a useable current?

The generator, if bought is usually a DC alternator generator.  This is just an AC generator with a one way switch on each phase.

If built, the generator is usually AC, but then sent to a rectifier to convert it to DC.

The DC is then usable by an inverter/charger which decides to either convert the DC to AC to be used, or to dump it to a battery bank for storage.  This same device can convert the stored  capacity to AC to be used when generation is down.

Sometimes the controller will have to dump excess to a resister element.  There are actually hot water heater elements that were designed to convert this wasted energy to heat such as the 600 Watt 12 Volt DC Submersible Water Heater Element that I found on amazon, you can actually use an ac heater element, but as you drop voltage on those elements, you almost reduce the wattage rating by 25%!

There are other ways to use a basic charge controller and consumer grade inverter as well.  It would be a little cheaper if you knew what to look for, but it can be a little more complex.

What would be an easy way to create this system in a long term survival situration with only the materials you could scavenge?

I have seen things built in buckets, using CDs and styrophone, and even articulated PVC devices, but I don’t think most of these are feasible for the type of systems I would build.

Probably the best build would not be what you would call “easy.”

One of the best builds would be a large waterwheel with a gear-ratio change driven by belts or handmade gears.

The awesome thing about waterwheels is that you can couple them up to an alternator or even a mill for grinding grain.

The same wheel could be used to drive a pump that will pump water a long distance… at low flow rates.

If you were wanting something you could use until that was built, you could probably modify a bicycle to run an alternator, with a battery bank, and be very careful how you use your power.

In our current world, if you wanted to reduce your electric bills by using hydro-electric power, what type of system would you build?

The very first thing I would do it to make my home more efficient first.  Biggest bang for your buck.

Then I would look at what my situation is.  

Water flow

spring, river, waterfall.

Is it year round or seasonal

How far am I from the source?