Learn About Solar
1. What are the basic components of a solar power unit, and how do they function? (Collector panels, inverter, batteries, switches and wiring, etc.)
Photovoltaic panels turn sunlight into electricity. A charge controller manages the charging, making sure that the batteries do not get overcharged. Current advancement in electronics provide maximum power point tracking (MPPT), taking advantage of every electron available. Batteries are the "weak point" of any solar power system. Deep cycle batteries designed especially for solar are the best option for energy storage. Fuel cells have potential for future storage. Breakers provide over current protection. Inverters turn DC power stored in batteries or provided by solar panels into AC power — so lights, household appliances, computers, other electronics can be used.
2. What size panels are typically installed, and how much power (kWh) is produced from eight hours of sunlight? Are there different types of panels?
SonLight Power usually uses what is commonly called thin-film modules — which do not have glass in the module — but are encapsulated in a clear polymer. Our current design uses 3-90Watt panels — which are designed especially for us — and fold up, fitting three to a box which weighs less than 50# and is less than 62" — so we can take them as luggage.
The amount of power produced depends on the "solar window" of any particular location. Locations in Central America average around 6 "full sun" hours per day. Full sun hours are defined as the amount of solar ionization provided at solar noon — for 1 hour.
There are many types of panels . . . based on different manufacturers' designs. However the three general varieties are: single-crystal, poly-crystal and thin film. Thin film is less efficient per square foot, but does absorb infa red waves, making them more efficient in cloudy weather.
3. Is the voltage 120V, so any modern electronic device can be used? How many light fixtures can be served by one unit?
Solar panels produce DC power, usually 12V or 24V, but the systems SLP installs always uses inverters to make AC power — due to the conformity principle — and the requirements of DC wiring and the availability of DC appliances. Sine Wave inverters, more expensive than modified sine wave inverters, provide clean power which can be used effectively for all electronic applications and tools.
SonLight Power installs a variety of sized installations, but our standard "school" install provides a 300W inverter — which can run quite a few 23W bulbs (compact fluorescent), a TV/DVD player, a fan and even a laptop computer for most of the 5-hour school day.
4. What is involved in the actual installation? How important is the location, height, and angle of the solar panels installed on a roof or pole?
SonLight Power does pole mounts only — in places where the roofs are not made to US code or better (concrete roofs are okay), due to past accidents.
Rails are spliced together to hold the panels and bolted to a top of pole mount welded in country to our specifications. Importance of angle depends on latitude. In locations within 10-15 degrees of the equator, a straight up (horizontal) mount is okay. It is best to angle the panels toward the equator at an angle = the latitude. In North America it is best to adjust the angle 2-4 times a year. In our smaller installs the panel are wired together in a combiner box. Then "home run" wires go down to the charge controller — then to the battery (with proper breakers in between). The inverter is then wired to the battery. Lights, other appliances wired to inverter.
5. What is the cost for materials for one of your units?
The standard SLP kit costs about $3,500, including in country costs of batteries and the pole, and some shipping. We install the larger systems in area (orphanages, clinics, larger schools) that need more power. The cost ranges upward of $10,000 including investment into efficiency. The system we installed in the City of Refuge orphanage in Rosirita Mexico cost about $30,000, including $20,000 in solar panels donated. The system decreased generator usage from 6-8 hours per day to 1-2 hours, saving the install cost in less that two years.