Tilaran – ICE – Alternative Energy – Wind and hydroelectric power engineering – Dimitri
After arriving late in Tilaran, we spent the first of three nights at Guadalupe Hotel. We woke up early to a delicious Costa Rican breakfast. The group saddled up in the minibus and left for the tour of Instituto Costarricense de Electricidad (ICE – pronounced ee-say), Costa Rica Electrical Institution.
ICE, built in 1978, is the main energy producer and electrical network for Costa Rica. Their mission is to produce electricity that is environmentally safe and to satisfy the needs of customers along with remaining as Costa Ricas highest producer. This company basis their service on alternative energy resources. ICE is segregated into 4 plants: Arenal, Corobici, Sandillal, Tejona. These plants are not only engineered for green energy but they have to be able to withstand natural disasters such as earthquakes, which can be felt roughly, 20 times a year.
Last year ICE produced 7,178 GWH of Costa Ricas 9,722 GHW demand. Of the energy produced by ICE the is production of electricity is split as such: 72% hydroelectric, 15% Geothermal, 12% Combustion (only non alternative energy – used as a back up when others are not available), 1% win.
Even though ICE is a leader in alternative energy, production hydroelectric and wind energy present environmental impact. In 1949, ICE became a public business and at this time only 10% of the Costa Rican citizens had access to electricity; now, in 2012, almost 95% of citizens have access. At Arenal, we learned about ways other dam methods of hydroelectric production and with those different types the hydroelectric cycle the worst affects on the environment is during a “clean out,” removal of sediment. In this situation, the reservoir is drained to remove sediment that collects at the inlet, which is flushed down stream causing significant damage. This task happens once every two years and the community must be involved. Since the water levels are lower the community is negatively affected but a positive for the community is the abundance of fish that are unable to escape and easy to catch. On the contrary, the elimination of water causes the wildlife to depreciate . Thus, one method is to capture the fish and restocked after water level is restored. While the water is down, the sediment is flushed from the inlet to undo the restricted flow of tunnels leading to turbines. Ecological engineers constructed a less invasive procedure that eliminates the “clean out” process. Instead, at the inlet a bucket resembling an excavator’s, lowers to tunnel where the sediment settles and removes the debris without having to lower the water level. The option of a no clean out system makes production of hydroelectric energy have less environmental impact factors.
The hydroelectric turbine systems used by ICE are referred to as a Francis turbine, this style has a vertical axis and horizontal turbine blades. Water from the Arenal reservoir travels 12 km (about 8 miles) and drops 200 m (about 650 ft) over its duration. Embalse Arenal (artificial lake of Arenal) is the only reservoir that is not dependent on rain fall, it is still able to function during the absence of rain which occurs during the dry season. The reservoir collects rain fall throughtout year and has rivers supplying the 1990 million cubic meter of usable water. This potential energy flow down the tunnels to Arenal were it turns its first phase of turbine, then the returns to regular flow rate and to travel to Corobici and finally to Sandillal, which also has its own reservoir. Embalse Sandillal (artificial lake of Sandillal) uses the Francis turbine but the reservoir is dependent of daily rain fall, the fall back to Sandillal is during the dry season the plant cannot run constantly due to lack of supply. Sandillal is a much smaller reservoir with 5 million cubic meters and the drop of water is 50 meters (about 160 ft). The average flow of both systems is 100 cubic meters per second.