Sustainable Technology:

During the summer of 2006, Chloe Weck and Nick Strand were presented with a research grant by the Technogenesis program at Stevens Institute of Technology. The grant was given to the students to pursue research in determining the best source of alternative energy for the small community of Jarabacoa in the Dominican Republic while having applications to any developing community.

During the first week of research, we traveled to the Dominican Republic with a small group of Stevens students eager to get involved in the project. During our travels, we found many projects that would benefit the small, growing communities. It was difficult to decide which project to undertake as we wanted to help everybody, but one community in particular stood out.

The community of El Dulce consists of sixty-five homes and lies along a mountain river in Jarabacoa, Dominican Republic. Some of the mountain communities in the region receive power, when they can afford it, from government funded power lines running through their land. El Dulce is not one of these communities. The community members wanted to create their own source of alternative energy and they wanted our help.

Our challenge was to design a source of alternative energy keeping simplicity and sustainability in mind. Our first action upon returning home was to determine the feasibility of the project and investigate all options. There are many alternative methods of producing power such as harnessing biomass energy, geothermal or nuclear energy - fission and fusion, hydro power, wave energy, solar energy, and wind energy. The amount of power we needed to create, the geographic location, and our cost constraints limited the types of energy production available to us. After applying these constraints there were three possible sources remaining: hydro power, wind, and solar energy.

Wind energy seemed attractive at first, but after further research several factors ruled this option out. There were locations in the surrounding areas of the community with a seemingly large amount of wind, but in order to determine the feasibility of implementing a wind turbine, a year-long study should be carried out. Another limiting factor to harnessing wind energy was the extremely high costs associated with a powerful wind turbine. Solar energy was a promising possibility due to the abundance of sun in the Dominican Republic. This option was soon ruled out due to its low efficiency/power-output per dollar. As well, maintenance was required to keep the solar panels running at the best possible efficiency and one of our constraints is to minimize the amount of maintenance.

After all of the previous options were essentially ruled out we adopted the idea of a hydro-electric energy system. Several of these systems are already in place in the Dominican Republic due to the fact that while many of the poorer communities may have power stations nearby, the government chose not to bother running power lines to their houses. After further research, it was discovered that PVC piping for the system can be purchased from a Dominican company called Ferretería Americana, allowing easy access to possible replacement parts.

Hydro-Electric energy generation was chosen not only for the reasons above but also because the system as a whole is modular, meaning that if more power is needed in the future a second turbine can simply be added. As of now, the energy requirement given to us is 20kW.

Hydro power is defined as the use of water to power machinery or make electricity. Hydropower uses a fuel—water—that is not reduced or used up in the process. Because the water cycle is an endless, constantly recharging system, hydropower is considered a renewable energy.

When flowing water is captured and turned into electricity, it is called hydroelectric power or hydropower. There are several types of hydroelectric facilities; they are all powered by the kinetic energy of flowing water as it moves downstream. Turbines and generators convert the energy into electricity.

The size of the hydroelectric system is determined of the amount of power it is capable of producing. Although definitions vary, the United States Department of Energy defines large hydro power as facilities that have a capacity of more than 30 megawatts, small hydro power as facilities that have a capacity of 100 kilowatts to 30 megawatts, and micro hydro power as facilities that have a capacity of up to 100 kilowatts. Our 20kW system will therefore fall into the micro-hydroelectric category.

Hydroelectric systems are also characterized by the water intake. The most common type of hydroelectric power plant is an impoundment facility. An impoundment facility, typically a large hydropower system, uses a dam to store river water in a reservoir. Water released from the reservoir flows through a turbine, spinning it, which in turn activates a generator to produce electricity. The water may be released either to meet changing electricity needs or to maintain a constant reservoir level.

A second method is a pumped storage facility where energy is stored by pumping water from a lower reservoir to an upper reservoir. During periods of high electrical demand, the water is released back to the lower reservoir to generate electricity. Lastly, a Run-of-river, or diversion, systems channel a portion of a river through a canal or penstock directly to the turbine. Our set up will be similar to the diversion system shown to the right.

Micro-hydro systems like these are designed to operate for a minimum of twenty years if they are properly looked after. By charging a small usage fee, communities can accumulate enough money to pay for the replacement of the unit at the end of its useful life. Once the system is in place, they should continue to function indefinitely without any more external funding. Unlike traditional power stations that use fossil fuels, micro-hydro generators have practically no effect on the environment, and because they don’t depend on dams to store and direct water, they’re also better for the environment than large-scale hydro-electric stations.

The feasibility of a hydroelectric system depends on the location. The chosen water source must be able to provide the desired amount of power. To determine the potential power the head and flow rate must be determined.

The head is the vertical distance from the top of system where the water enters the pipe or penstock to the bottom where it is released back into the river. The difference in height is critical to the power output. The greater the head, the higher the potential for harnessing power.

The flow rate is the volume of water which flows past any given point in the system within the period of one second. The greater the flow rate, the higher the potential for power.

The potential power is calculated by multiplying the head, flow rate, and force gravity. The actual power output in is equal to the potential power multiplied by the efficiency of the hydroelectric system. The chosen site can easily provide the power needed for a 20kW system.

The main design components of a hydro system are the penstock and the turbine. The penstock is any artificial method by which water is transported to the turbine from the highest point in your system with the minimum of obstruction and resistance.

Our Penstock will be in the form of PVC pipes and will be protected at the intake by a screen. Sizing the penstock involves a tradeoff since the smaller the pipe, the cheaper its cost. However, friction losses increase as pipe diameter decreases. So, the longer the penstock, the larger the pipe needs to be.

Often the most expensive component in any hydroelectric plant is the turbine. The turbine is a sophisticated rotor that extracts power from moving water. Some specifications and costs of turbine-generator systems can be found in the appendix of this report.

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