Site Visits on Independence Day

Sesotho word(s!) of the day: Khotso, Phula, Nala - Peace, Rain, Prosperity

Independence Day

October 4 is independence day in Lesotho. A day usually occupied by attending and feasting on a traditional braai (barbeque) and enjoying plenty of Maluti brew. (Maluti brewery is the biggest brewery in Lesotho, and is named after the Maloti (pronounced maluti) Mountains) This independence day was distinguished from most others as the day that the Government of Lesotho unfirled the new "Peace" flag.



Yup, the Government of Lesotho changed the flag of Lesotho. The previous flag had the three colors of the new flag, but arranged in diagonal stripes, with a shield, a spear, and a traditional weapon crossed together in the upper left-hand corner.

The new flag retains the three colors that symbolize Khotso, Phula, and Nala, but replaces the war symbol with the traditional Basotho Hat. This is the new peace flag. THis flag has been excepted with mixed reviews from the Basotho. Some like it, some don't really care, and some have complaints about the hat. The biggest complaint is that the hat on the flag is black, whereas the hat in real life is light brown - made out of thatches.


Site Visits

On Independence Day, the Solar Turbine Group bowed out of all braais, and went on the road to conduct site visits. We visited all three sites under consideration for the deployment of our pilot systems: the village of Ha Teboho, the clinic at Ha Nohana, and the high school in Bethel.

The village of Ha Teboho is an ideal site - a fairly level ground, a perfectly-sized clearing just adjacent to the gravity-fed water pump that supposedly never runs dry, and an almost unobstructed horizon. Our site visits involved taking measurements, noting the angle of the horizon, measuring the flowrate and temperature of the water available from the tap, and speaking with the chief.

Site and Water Source

Site Assessment in Action

Matt and the Chief

The clinic at Ha Nohana is in desparate need of electricity. The clinic currently has no source of electricity, which forces the doctors to perform emergency procedures that must be addressed at night in the dark, with the assistance of a headlamp and a parafin lamp. As one of the physicians says, this situation is clearly "sub-optimal". This site, however, is a distinctly more challenging site. The ground is uneven, several new buildings are planned for the grounds of the clinic, which would take up most of the open sites, the horizon is blocked to the west by a giant moutain, and the location of the water and electricity load are less than ideally located. So we took measurements of several areas, and will find the best that will work!

Water Source and Clinic

Uneven Ground at Ha Nohana

Mountain Obstructing the Horizon

Bethel high school is more in need of hot water. The school currently has a generator that pumps electricity into its underground grid to power the school buildings. Their electricity usage per day is quite high, as they run over 20 computers pretty much all day long. To meet these needs, the school runs the generator from about 8-4 and again from 6-8 to meet the electricity needs for evening studying, cooking, and cleaning. The school also has dormatories with no hot water. It gets extremely cold in Lesotho in the late fall / winter / early spring months, and the unheated water is often even dangerous to bathe in. To suit these needs, the system we design for this site will produce hot water for the dorms and electricity to reduce the load on the generator, but certainly not displace it. Site prep at the high school will be very straight-forward. The site is level, unobstructed, and has good proximity to both the water source and to the electrical grid into which the system will feed.

Design Sessions

Sesotho word of the day: Phula - rain

The Solar Turbine Group has spent the last few weeks up in the mountains putting out heads together to improve the design of our system. During this time, we were inondated by typical thunderstorms that roll through the country, and sneak up out of no where. It really is true that the weather in the mountains can change in an instant! (even more suddenly than even in michigan or in boston!) According to Tumelo, the Basotho are afraid of the rain -- i can see why: it seems that rain in Lesotho is ALWAYS accompanied by thunder and lighting, and in a mountainous country like Lesotho, with no trees or tall things around, you definitely feel like you are inside the storm!

So, where we left off with the design of our system can be summarized by the following pictures and descriptions.

System Protoype at MIT, August 2006

As shown above, the system is made up of two basic components: an array of 4 parabolic mirrors and the Organic Rankine Cycle (ORC).

Parabolic Mirrors

The parabolic mirrors track the sun and focus the sun's energy onto a focal point inside the parabolas. Through the focal point of each parabola runs an absorber pipe that absorbs this concentrated energy. All of the absorber pipes are connected to eachother in series to form the thermal fluid loop. A thermal fluid (this summer we used glycol) travels through the thermal loop and gets hot. The figure above shows one parabola that is turned toward the East to capture the morning sun. The silver wheel at the far end is part of the tracking drive train, the black pipe is the absorber, and the valve at the close end is for draining the thermal fluid loop of its fluid. You can also see the absorber reflected in the mirror, and the strip of light that is focused on the bottom side of the absorber.

Organic Rankine Cycle

After the thermal fluid runs through the thermal fluid loop and is heated up, it enters into a heat exchanger, where it transfers its thermal energy to the working fluid of the ORC. In the ORC, the hot working fluid exits the heat exchanger and enters an expander. The expander spins an alternator (from a car) that charges a deep-cycle battery. The working fluid then exits the expander and goes into a condenser. This summer, we had a two-stage condenser: the first stage was another heat exchanger with a gas-fired fridge, and the second stage was an air-cooled radiator. (In lesotho we will use water to cool the system, so the system will also provide hot water)

ORC

Fridge and Radiator

After the working fluid goes through the condensers, it enters a pump, then returns to the thermal fluid heat exchanger to get heated up again. And around and around we go.

This prototype was built by our group this summer (shown below) in a parking lot at the West end of the athletic fields at MIT. The system is run intermittantly by our team members at MIT as they perform tests on the system.

From Left to Right, Alex, Libby, Perry, Sam, Sorin, Matt, Amy, Simmons Hall