New-gen Electrical Gear for Rural Markets

How charge controllers and photovoltaics lowered the cost of lighting for 50 families in a remote Guatemalan village.

In La Nueva Providencia, a village of 50 families in central Guatemala, candles and kerosene have been the primary sources for lighting for years. Candles don’t provide much light, yet they’re costly – as much as 90 cents a day in a region where daily wages are around $4 when work is available.

Years ago, their prospects for getting electricity would have been bleak. But a number of altruistic engineers are bringing help to those who need it. Since 2002, volunteers have worked through a group called Engineers Without Borders USA. EWB has gotten solid support from philanthropic  engineers – it has worked on 350 projects in over 45 developing countries, changing the lives of millions of people.

The situation in La Nueva Providencia caught the attention of the Marquette University Chapter of EWB. Engineering students at the Milwaukee school decided to use their skills to alter the situation. Marquette is one of the many universities supported by Siemens Cooperates with Education. Siemens provides equipment at low or no cost, and some employees serve as mentors for students.

At the start of the La Nueva Providencia project, the students determined that each home would be wired for three lights and an electrical outlet for small household electronics such as TVs, DVD players and radios owned by many residents.

Their initial step was to install enough solar panels to provide two to four hours of electricity to each home every day, splitting the delivery fairly evenly between mornings and evenings. Along with street lights, this translates to energy consumption of five to 10 kilowatt-hours per day and future use of 20-30 kwhrs per day. It is expected that each family could use the TV for 90 minutes in lieu of 80 percent of the lighting in the home.

This yielded a peak demand of approximately 100 watts per home for a total of five kilowatts for the village. Initially, the Marquette students planned to leverage a spring-fed river for hydroelectric power, but it was deemed insufficient for peak demands. They decided to augment the hydroelectric turbine with solar systems.

After further analysis of the challenges of installing a turbine system in the rugged terrain surrounding the village, the team opted to start with photovoltaic generators and install the turbines later.

Those plans were developed using a phased approach. This strategy requires additional trips, but it splits the tasks into a manageable series of projects the Marquette students could fit into their schedules. To date, the five phases of the installation have an estimated cost of around $40,000.

The initial PV system produced approximately four to six kwhrs per day or approximately 20 percent of daily consumption. An expansion added an additional 20 percent of the energy initially required by the system.

The first phase of PV system installation consisted of 15 – 170 watt panels connected for 105 volt operating output. They are connected to a charge controller that supplies regulated power to a bank of 12 – 105 amp-hour batteries. These nickel metal hydride batteries are in turn connected to a 2,500 volt-ampere (va) inverter to power the electrical system.

These system components were chosen to allow flexibility in expanding as the system grew during the phased implementation. That made it simpler to connect more solar components to add nine 235-watt panels, another charge controller and 2,500va inverter.

The final implementation will result in four 2,500va inverters connected to create a 120/240 volt power system with a peak capacity of 10 kilovolt-amperes. The system will be managed by a controller to balance power from inverters and coordinate charge controller output.

Throughout these phases, the size of the community was a challenging factor. La Nueva Providencia has approximately 1,400 feet of pathways, which are now illuminated with pole-mounted street lights.

The team members put termination boxes for individual homes on each street light pole. That minimized the amount of trenching that will be necessary and will allow for more connections to each home.

To avoid unequal use of the resources, volunteers installed a relatively small circuit breaker in the circuit on each house. This provides protection and limits the energy usage so one homeowner can’t access significant portions of the limited system capacity. Each home also receives a ground fault circuit interrupter electrical outlet for safety.

Beyond the desire to create a stable system to provide electricity, one of the key goals was to ensure that the system would continue to reliably deliver power over the long term. So far, that’s been achieved.

The roof-mounted solar panel  has provided reliable operation, but the charging connector and the nickel metal hydride (NiMH) batteries require replacement after 18 months. That’s one reason that maintenance costs were calculated to be $1,200 per year over the expected 25-year life of the system.

This covers cost associated with both the PV system and hydroelectric system. When this total cost is divided among the families, it’s affordable. The average cost per family was determined to be $2 per month, or $24 per year. Eliminating candles and kerosene wicks will potentially save every family an average of $23 per month while eliminating the safety risks and adverse health effects attributed to the open flame.

Marquette’s La Nueva Providencia highlights the effectiveness of programs developed by EWB with help from corporations like Siemens. The system had generated over 2,200 kwhrs in the first 22 months after its installation. That’s an average of 3.25 kwhrs per day. It’s been reliable throughout this period and was not damaged during heavy storms resulting from tropical storm Agatha which damaged surrounding areas in May, 2010.

 

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