My interest in small scale hydroelectricity was born at my summer home in the Catskills of upstate New York in the US. My house is set on several acres with a steep hill and small waterfall just outside. The waterfall’s source, a spring high above the house, offered enough head and flow for a small impulse style hydroelectric generator. Using an existing cistern formerly used to supply the house, I ran a 2in pipe down the hill achieving a head of about 15m. When I narrowed the aperture at the bottom of the pipe I achieved a strong steady stream of high pressure water. I was in business. I still had to build the generator, but I knew that I had the power to drive it.

After experimenting with several design concepts, I came up with a hydroelectric generator housed in a five gallon bucket and made almost entirely from PVC and hardware acquired at the local home centre. The power was produced using a permanent magnet alternator (PMA) driven by a turbine made from PVC inside the bucket. Made from 8 ?in, 45 degree PVC couplings cut in half and mounted on a hub, the turbine had a total of 16 spoons.

To drive the turbine, I created a manifold at the top of the generator and split the flow into four parts culminating in nozzles arrayed around the turbine. Though not terribly efficient, I was able to achieve more than the 13.7V necessary for a 12V system. I realised that because of its simplicity, ease of construction and the fact that it was relatively cheap to make, the generator might be useful in the developing world where many communities do not have access to the electricity grid. Though I didn’t know it at the time, my new interest would gain momentum and I began a journey that would ultimately take me to the highlands of western Guatemala.

Developing power

My tenure with an NGO called Appropriate Infrastructure Development Group (AIDG) began when I learned of their work. I realised that my efforts at small scale hydro would be a nice fit with their work bringing electricity to rural areas in the developing world.

Based in Boston, with field offices in Haiti and Guatemala, AIDG works to promote green technologies to underdeveloped countries and to incubate small businesses to manufacture these technologies. Focused on clean water, clean air, sanitation, and energy, AIDG seeks to provide services by developing systems that are affordable to people with modest means. They develop clean burning cook stoves, biodigesters, water filtration, wind and hydroelectric power and solar hot water systems. By incubating small local businesses to manufacture, maintain and distribute the systems within the communities that they serve, AIDG offers both the hope of better services for the underserved and the prospect of income-generating projects for the businesses that they help create.

In January 2008 I began work with AIDG in Guatemala. The small community of La Florida in western Guatemala was chosen as my test site as it had recently lost what little electrical services it had. It also had the abundant water and mountainous terrain necessary for small scale hydroelectricity. The people of La Florida, with around 100 families, had to travel an expensive and time consuming two hours by bus to a town with electricity to pay a service to charge their phones.

There are no land lines in these areas and cell phones provide critical contact with the outside world. They are important economically as well, as they enable small farmers to seek the best price for their crops (in this case coffee) and often cut out the middle man. Also, cell phones have become an important way for people to transfer money when buying and selling goods. They are a life line to people in remote areas for contact with family, the market and medical services.

I proposed to install a system at La Florida to charge cell phones. The challenge was to make the entire installation (generator, penstock, trashrack and associated electronics – regulator, battery and inverter) cheap enough so that the operator of a charging service would have a reasonable chance of making a profit, while paying back the cost of the generator and installation over time.

Tying into an existing canal cut into the side of a mountain at La Florida, we used a five gallon bucket fitted with hardware cloth as a trashrack. At the bottom of the bucket we plumbed the top of the penstock and installed a plastic valve for service. With the help of a local farm boy and machetes provided by the community, we cut our way through the jungle down the mountain to our generator site. At close to 60 degrees of incline this was no easy task. Once the area was cleared we began laying pipe. To secure the pipe, it was tied off to trees along the route. At the bottom of the initial descent more pipe was laid across a relatively flat area and an additional drop in elevation was achieved by crossing a small road and descending still further into the valley below. In all we laid about 90m of 2in pipe for a total head of a little more than 29m. At the generator site we installed another valve for service.

With economy in mind, the system uses only one standard automotive battery. Systems of this size typically use a large bank of deep cycle batteries that are quite expensive. To make the system affordable we would use only one lead acid battery. The battery is never discharged significantly because the system uses only as much energy as it can produce in real time. More batteries and greater capacity can be added later but to put the system in the hands of our constituency it needed to be as cheap as possible. Because the system is on line all the time, if the load is equal to or less than the energy produced by the generator, the battery is never depleted very much, giving it the same lifespan as if it was in an automobile.

Once the generator was installed, a dump load regulator, battery and inverter were wired to the generator. After hooking up a couple of power strips for the phone chargers, we slowly opened the valve to the generator. Everything seemed to work perfectly. I was getting a mere 60W, but it was enough energy to charge many cell phones simultaneously without depleting the battery. My I-pod needed a bump so it would be the guinea pig. It didn’t catch fire and was fully charged in short order.

After determining that everything was working well, we gathered the cell phones from the community. We were able to charge ten cell phones at a time without discharging the battery. At an average of an hour’s charging time per phone, if ten phones are being charged at a time, the system could charge 240 phones in a 24-hour period. More than enough for La Florida.

Once on site, the entire installation took two people less than a day to finish. At the time of the installation, the generator cost around US$350 and a car battery about US$75. We made a dump load regulator for US$30 and the 100W inverter that we used was also about US$30. The PVC pipe and valves were expensive at US$200. With the trashrack, the entire system cost about US$700.

If financed over a one-year period , say 5% interest, the hydroelectric system would cost US$2 a day in principle and interest. If the proprietor of such a service were to charge an average of 20 cell phones a day at 25 cents per charge, that would be a profit of more than US$3 per day. That is more than US$1000 a year of income. If one is living on US$6 a day, or US$2190 a year, as many people in Guatemala do, US$1000 represents a major pay raise and could make a big difference in someone’s life.


Since the installation at La Florida we have made some important breakthroughs. One of the biggest challenges for energy schemes in the developing world is making systems that are affordable to people who make almost nothing. At US$700, my system compares well with equal sized wind and photovoltaic systems, but because our constituency are under constant economic pressure, the prospect of incurring a debt of this size is difficult for them to imagine.

The challenge then was to make the generator even cheaper. The generator that I developed in the US, though relatively inexpensive at around US$350, was still a bit pricey. The vast majority of the cost associated with the generator, the permanent magnet alternator that I got in the US, was too expensive. Plus there was the cost of shipping. My thought was to build my own PMA using materials readily available in Guatemala.

I settled on the Nipo Denso alternator from Toyota’s 22R engine as it is the most common alternator in the developing world. It is the alternator found in most Toyota light trucks ubiquitous in Guatemala.

Rebuilding the rotor inside the alternator from scratch, we made a rotor using neodimium magnets arrayed around a core made from sheet metal laminates. The core was then attached to a spindle of the same size as the factory rotor and installed in the alternator. After bench testing the PMA it proved to be an excellent fit with the rpm’s that I could achieve with the generator. The cost with labour to manufacturing the new PMA was around US$200, about US$100 less than the cost of the PMA from the US and it could be manufactured locally.

The only element of the generator that could not be sourced in Guatemala were the Neodymium magnets. Though the magnets would have to be shipped from the US, shipping the magnets was a lot less expensive than buying and shipping the entire PMA, plus the PMA could be built by locals benefiting the local economy. Xela Teco, an alternative energy business incubated by AIDG in Guatemala could build the entire generator including the PMA in Guatemala. If mass produced the generator could be produced cheaply and benefit a lot of people.

Ongoing work includes the prospect of creating micro utilities in which super efficient LEDs could be used to light several homes using the generator. The operator would charge a monthly fee and make a modest profit while paying back the generator over time. Another prospect that we are exploring is the charging of small batteries. Used in flashlights and radios, these batteries represent a major expense to individuals and blight to the environment when they are disposed of on the land. Again, the operator would charge a small fee and both the producer and consumer would benefit.

Looking for partners

I returned to Guatemala in January 2009 to continue our work developing small scale hydroelectric power. This year we hope to do several permanent installations of the generator, training operators and providing the necessary credit for them to get started.

Developing countries are being hit particularly hard by today’s economic realities. It is more important than ever to find solutions to the world’s energy needs and small scale hydroelectricity offers a clean affordable solution that makes sense. AIDG is always looking for partners in our endeavours and we welcome any contribution and support.

If you want to contact AIDG, see what we do, or find out how to contribute to our work, visit or contact

Sam Redfield is a freelance lighting technician for film and television in New York City, US and volunteers for AIDG for part of each year.