Mission 2

So thanks to university debating which recently sent me to India, I am in a somewhat good position to visit Uganda before I make my way to Turkey for an exchange program in Istanbul. I will be in Uganda for just 1 week and so it will be exciting to see how the group and the grid is going.

This is a draft list of things that I will do over this week.

• Document any expansions on the grid since leaving Uganda.
• Interview some of the grid clients who use lights at night.
• See what new practices in grid maintenance have emerged or which practices have deteriorated.
• Make preparations for the boost and buck converter upgrades (more on this below).
• Reconnect them with internet. Apparently they lost connection due to issues with their plan - sure this is something they could sort out.

Boost and Buck Converters:

Since the grid we are running is only 12 V there is very large loss incurred when running current over long distance. Power lost will be the voltage drop over the wire multiplied by the current. Since we are using a low voltage we need a relatively high current to get the target amount of power. This theory can be condensed by the following equations:

V = IR .... 1

P = IV .... 2

Sub 1 into 2 and we get: P = I²R. To minimize power loss we need to minimize current. A great demonstration of this principle is here, a video by Julian Ilett.

We have ordered a DC to DC boost converter which steps voltage up and also a buck DC-DC converter which steps voltage down. Both of these work by using a MOSFET to periodically switch an inductor. By changing a pot on the board you can change the frequency of switching and therefore change the output voltage.

It is unlikely that we will have the circuits delivered to the FSD Masaka office by next week so we will just teach the Lwemodde youth group how these circuit work and suggest ways to implement them into their grid. When they arrive they can instal the converters. The basic idea will be to power buildings very close to the power station with the standard 12 V directly from the battery. For areas further away we will step the voltage up to 32 V and then step it down in another part of the village to 12 V and distribute from there.

Some interesting innovation will need to come with this upgrade. Perhaps some isolators for our power lines. May not be necessary at 32 V but it is good preparation if we ever step up to a higher voltage. We will need to make boxes for the step down converters and ensure that they are not tampered with. The converters will need to be strategically placed for efficient distribution and we will need to prove good heat dissipation for safety. Hopefully those massive heat sinks prove effective. Throughout the week I will be blogging to track all progress and learn how the grid has operated since myself and Lydia left the area.