Civil Works at Kigogo

Once we got back from Kigali with all the materials (and Alison!) we made some final touches on the system at Kigogo and reopened it for business. I’ll explain some of the problems of the system and how we went about solving them.

The main civil works issues that Kigogo had when we arrived in Banda were as follows:

1. Water overflowed at several points along the channel in the rainy season, which caused hillside erosion

2. The site operator had no robust way to control flow into the system; his method of stoping flow to the settling tank was a combination of mud and leaves inserted into the channel

 

After brainstorming, weighing specification importance and comparing design alternatives like we’ve been taught at Thayer 🙂 we decided to construct a spillway just before the most severe point of rainy season overflow. The spillway was designed to let 12 L/s continue towards the settling tank while sending the remaining water back to the river. Downstream of the spillway, a sluice gate allows the site operator to fine tune the amount of water continuing to the settling tank and also stop the water completely when the system needs to be turned off.

 

Beginning to build the overflow at Kigogo
Beginning to build the overflow at Kigogo
Laying the base of the overflow
Laying the base of the overflow
Finishing the base of the overflow and checking the slope
Finishing the base of the overflow and checking the slope
Pete touches up the overflow
Pete touches up the overflow
The completed overflow structure! It is sized and sloped so that the necessary  amount of water continues down the channel and eventually to the turbine while all excess water flows over the small lip, into a pipe and back into the existing stream. By dealing with this excess water in a controlled manner upstream, we hope to prevent water from spilling on to the hillside and creating erosion downstream.
The completed overflow structure! It is sized and sloped so that the necessary amount of water continues down the channel and eventually to the turbine while all excess water flows over the small lip, into a pipe and back into the existing stream. By dealing with this excess water in a controlled manner upstream, we hope to prevent water from spilling on to the hillside and creating erosion downstream.
Another view of the completed overflow
Another view of the completed overflow

 

The overflow pipe transports extra water in the channel down to the existing stream.
The overflow pipe transports extra water in the channel down to the existing stream.
This is the bottom of the spillway, where the water is retuned to the stream. The water has a high velocity and must be slowed down so that it does not effect the stream. The area is in the photo is in the process of being filled with rocks that dissipates the water's high energy.
This is the bottom of the spillway, where the water is retuned to the stream. The water has a high velocity and must be slowed down so that it does not effect the stream. The area is in the photo is in the process of being filled with rocks that dissipates the water’s high energy.

 

The finished product seems to work pretty well. The real test will be during the rainy season though. We hope to get some pictures and reports of how it’s working in a few months. We did get great feedback from the community already though. When I was buying eggs, the shop owner told me, “God bless you, Kigogo is amazing.”  June also got several handshakes and blessings at the opening of the Kigogo, when the site successfully charged all types of batteries faster than it ever had before. It is exciting to see the community respond positively to our work!

 

How a Hydro Site Works

I realized as I was writing a post about civil works construction that it might be good to refresh the readers on the technical workings of our hydro systems. To briefly explain, we have two pico hydro sites in Banda, Rwanda and one in Rugote, Rwanda, each of which generate under 1kW of continuous electrical power to charge batteries. The power is generated by diverting some water from a steam on top of a hill and sending that water, at high velocity, through a turbine at the bottom of the hill.   Here are some pictures and captions to help explain each component of the system in more detail:

This diagram from the DOE provides a good overview of the components that I'm about to describe. Please note a few differences in terminology. What they call Canal, I call Channel and what they call Forebay, I call Settling Tank. Also note that our systems charge batteries and do not transmit power through power lines like on this diagram.
This diagram from the DOE provides a good overview of the components that I’m about to describe. Please note a few differences in terminology. What they call Canal, I call Channel and what they call Forebay, I call Settling Tank. Also note that our systems charge batteries and do not transmit power through power lines like on this diagram.

 

Step 1, Intake: Hydo sites generate electricity by harnessing the energy of water flowing from a high point to a low point. The first step to harnessing this energy is to divert a small portion of a stream. In this picture you can see an intake, which is designed to divert the proper amount of flow. In this case, we are doing construction on the system, so water is not flowing through the intake, but normally, about 10% of the water enters the cement intake in the photo and continues on to the channel.
Step 1, Intake: Hydo sites generate electricity by harnessing the potential energy of water at the top of a hill. The first step to harnessing this energy is to divert a small portion of a stream. In this picture you can see our intake, which is designed to divert the proper amount of flow from the stream. In this case, we are doing construction on the system, so water is not flowing through the intake, but normally, about 10% of the water enters the cement intake in the photo and continues on to the channel.
Step 2, Channel: Once the proper amount of flow is diverted from the stream, it must be transported to a suitable spot on the hillside so that the settling tank, penstock and powerhouse can be constructed. The channel is just a gentling sloping, man-made stream that transports the water.
Step 2, Channel: Once the proper amount of flow is diverted from the stream, it must be transported to a suitable spot on the hillside so that the settling tank, penstock and powerhouse can be constructed. The channel is just a gentling sloping, man-made stream that transports the water.
Step 3, Settling Tank: At the end of the channel, the settling tank separates out sediment from the water that is about to be sent to the turbine. Large sediments can damage the turbine. The settling tank is essentially just a big tub where sediments fall to the bottom, and clean water enters the penstock.
Step 3, Settling Tank: At the end of the channel, the settling tank separates out sediment from the water that is about to be sent to the turbine. Large sediments can damage the turbine. The settling tank is essentially just a big tub where sediments fall to the bottom, and clean water enters the penstock.
Step 4, Penstock: The penstock is a pipe that transports water from the settling tank down the hillside and to a nozzle that shoots high speed water into the turbine blades. Unlike the channel, the penstock is steep and totally closed by high-pressure piping. It is difficult to get a picture of an installed penstock since they are normally underground, but this picture of us installing an overflow pipe is almost exactly what a penstock installation would look like. Imagine a settling tank at the top of the pipe and an nozzle and turbine, enclosed by a powerhouse, at the bottom.
Step 4, Penstock: The penstock is a pipe that transports water from the settling tank down the hillside and to a nozzle that shoots high speed water into the turbine blades. Unlike the channel, the penstock is steep and totally closed by high-pressure piping. It is difficult to get a photo of an installed penstock since they are normally underground, but this picture of us installing an overflow pipe is almost exactly what a penstock installation would look like. Imagine a settling tank at the top of the pipe and a nozzle and turbine, enclosed by a powerhouse, at the bottom.
Step 5, Nozzle and Turbine: At the bottom of the penstock, high pressure water is shot into the turbine blades to spin the turbine. You can see the end of the penstock coming through the powerhouse walls and into the turbine. Unfortunately the turbine casing keeps the nozzle and turbine blades hidden.
Step 5, Nozzle and Turbine: At the bottom of the penstock, high pressure water is shot into the turbine blades to spin the turbine. You can see the end of the penstock coming through the powerhouse walls and into the turbine. Unfortunately the turbine casing keeps the nozzle and turbine blades hidden.
Step 6, Electricals: The electrical system takes mechanical energy of a spinning turbine and turns it into electrical energy stored in batteries. Maybe a more electrically inclined traveller can post a review of the electrical system at some point.
Step 6, Electricals: The electrical system takes mechanical energy of a spinning turbine and turns it into electrical energy stored in batteries. Maybe a more electrically inclined traveller can post a review of the electrical system at some point!
Step 7, Powerhouse: The powerhouse is just a place to put the turbine and the electrical system.
Step 7, Powerhouse: The powerhouse is just a place to put the turbine and the electrical system.

 

I hope that this was educational! Please comment with any questions that you have!

Joey

Don’t Expensive Us!: Shopping in Kigali

While our concrete structures (which I’ll explain in the next post) were drying at the Kigogo site, Max and I traveled to Kigali with Pete, our Rwandan foreman, to buy several materials and pick up Alison from the airport. Up to that point, we had stuck to our aggressive project timeline, but after a few hours in Kigali we realized that staying on schedule was about to end.

 

Home Sweet Kigali!
Home Sweet Kigali!

We arrived on Wednesday afternoon and shopped for four hours. We found nothing that we needed and also discovered that Thursday was a national holiday, so everything would be closed. Perfect…so much for leaving on Friday…

Thursday we went to the Gikongiro Metal Market just to see if anyone was around on the holiday. The market is usually a pretty chaotic and exciting place. On the east side, you can find heaping piles of steel stock and welders doing work in only their sunglasses.

The cautious ones wear two pairs of sunglasses.
The cautious ones wear two pairs of sunglasses.

 

Separated by a gigantic pile of sawdust, the west side is home to several woodworkers creating surprisingly intricate parts. In the middle, rows and rows of tiny shops are crammed full of completely random and totally unorganized parts. And throughout the market, middle-men badger you, trying to earn a portion of profits, or at least get a tip for helping you find something.

Gikongiro Metal Market. See if you can spot the huge pile of sawdust.
Gikongiro Metal Market. See if you can spot the huge pile of sawdust.

Being the holiday though, the market was almost totally empty. We talked to a few middlemen and found out that the drainage pipes that we needed for our overflows don’t really exist in Rwanda or are very expensive. PVC pipes of the same size were actually less expensive. Again, wonderful… Bad news and still no purchases…at least we had time to play board games at our hostel. Max and I had been pulling pretty long hours in Banda, so a full night of sleep and day off wasn’t the worst thing in the world.

Max and I got some time off during Rwandan Independence Day
Max and I got some time off during Rwandan Independence Day

Our luck started to change on Friday though. I went to one part of town and found several small parts while Alison, Max and Pete went to the Metal Market and actually got great prices on PVC pipe by sending in Pete to shop around before revealing that he as with Max and Alison. The shop owners tend to hike up their prices considerably if they are selling to muzunguzs.

A day in the market
A day in the market

After a full day of shopping, we had almost everything and celebrated by going to the 4th of July party at the US Embassy. I’ve  been out of the US for several months, so the stereotypical American 4th of July celebration was exactly what I wanted. It came complete with cornhole, a dunk tank, grilling, baseball and fireworks (on a projector screen hahaha).

After that, we went on a late night run to a westernized supermarket in attempt to find a plastic backing for our electrical systems. Options in the hardware stores were limited and very expensive, as plastic is a rarity in Rwanda (plastic bags are actually illegal). While I was looking through cutting  boards and placemats, Alison and Max found our solution: bright green plastic tables. Check out the next posts, you’ll see them working out quite well.

Sorry electricals team. This is what we got you when you asked for a plastic box
Sorry electricals team. This is what we got you when you asked for a plastic box

Saturday was supposed to be easy. We just needed to have the supply truck pick up everything that we had ordered; we planned for it to leave for Banda by 2pm. As is often the case though, nothing was ready on time, people tried to charge us extra money, and after a headache of a day, the truck left at 7pm. It got to Banda at 2am and promptly broke down as it departed back to Kigali.

 

Playing the waiting game on Saturday afternoon.
Playing the waiting game on Saturday afternoon.
Loading up the truck with Kigali lights in the background
Loading up the truck with Kigali lights in the background
Are you surprised that this truck broke down?
Are you surprised that this truck broke down?

Back in Kigali, Max, Alison and I wanted more than anything to get down to Banda, but we had a few small errands to run on Sunday morning. I went to the Metal Market to attempt to buy expansion bolts without Pete to speak Kinyrwanda and negotiate prices (since he had gone to Banda in the truck). Since it was Sunday morning, the market was quite empty, so I reluctantly had to accept the help of a rather annoying english speaker who I knew would try to rip me off.

Check out the small shops in the background
Check out the small shops in the background

He brought me to a shop that sold the bolts I needed, spoke with the shop owner in Kinyrwanda and reported the price of 1000 RWF per bolt to me. But that wasn’t right… I thought out loud, “wait a second, the shop owner just said maganakane [400 RWF] for each bolt!” I had picked up just enough Kinyrwanda in Banda to understand their brief conversation and to realize that I was about to be ripped off. The man was stunned at first, and although I ended up costing him a profit of 600 RWF per bolt, he took it in stride and joked with me. As I was counting to make sure that they gave me all 50 blots, he blatantly said “You can trust us! We will try to charge you extra money, but we won’t lie to you!” And as I was leaving the market he said, “I can help you next time you come back. Now I know that you know Kinyrwanda. I will not try to expensive you!”

After picking up some materials to fix the broken down supply truck (sorry to the driver who was stuck in the rainforest that whole time!) we finally hit the road! We all couldn’t wait to get back to Banda after too many days in the big city.

 

Joey

Check Out New Posts and Photos!

Hey everyone, thanks for being patient in waiting for hydropower blog updates. Internet in Banda is obviously not the best, but I just completed my stay in Rwanda a week ago and am now traveling in Europe with some legitimate Internet. I’ll be putting up several new posts to get you all caught up, and I’ll be adding photos to previous posts. Be sure to check it all out.

 

Joey