The work-horse on the EPI playground, now manufactured by Playworld Systems, Inc., is a platform merry-go-round that allows many children to ride while a few take turns pushing. The generation train starts with the kinetic energy of children at play, which turns a hub bearing to which the entire deck of the merry-go-round is attached. A drive shaft from the hub connects to a helical gearbox operating as a speed-increaser. The high-speed output shaft then turns a permanent rare earth magnet windmill generator. The efficiency of this generator is over 70%.
After the energy is stored in the battery, the battery is used to charge the lanterns that students are able to take home at night for study groups. The custom LED smart lantern, designed by Energizer Battery, Inc. exclusively for EPI, has a nickel-metal hydride (NiMH) battery pack capable of providing over 40 hours of bright light between recharges. A computer chip in each lantern manages recharging from the large storage battery, as well as power to the LED bulbs. The lantern service life is expected to be greater than five years. Visit their site here and click on the "Our Video" box at the bottom right to see some of the amazing projects Energizer supports, including EPI.
Once the electricity is generated, it is sent via underground wires to a power enclosure, designed by the renewable energy solutions company Goal Zero, where it is converted to direct current and used to charge a large storage battery. In the enclosure, a state of the art MPPT (maximum power point tracking) power controller effectively manages the charging and discharging of the storage battery, ensuring long battery life. A solar panel is also connected to the power enclosure for educational purposes and to prevent battery discharging during school breaks. The CIGS (Copper Indium Gallium Selenide) solar panel provides about 20% of the total system energy when school is in session.
Most often, the schools in which EPI functions are comprised of nothing more than cement buildings, chalkboards, and wooden desks. Because they lack school supplies, and because they are rarely in contact with such amenities as electrical and mechanical devices, the students of these schools often have difficulty grasping the theoretical concepts of science. The electricity-generating playground equipment of EPI is the perfect science lab for the principles of general physics, energy transfer and many other scientific topics! What’s more, EPI has teamed with Loose in the Lab to supply EPI-sponsored schools with a full science module, complete with science lab equipement. The EPI lab includes such supplies as: thermometers, measuring tapes, solar cookers, magnets, compasses, solar cells, and wires. Most of the children in EPI schools have never seen items such as these.