Sunday, 26 April 2009

Watermill research latest

The quest for finding a suitable turbine for our old watermill site continues. I have been reading about horizontal watermills in Bethold Moog's seminal work: The Horizontal Watermill: History and Technique of The First Prime Mover (1994, The International Molinological Society).

It seems that their a fair bit of debate about the first origins of watermills, but it is around a few hundred years b.c., probably around present day China. The technology gradually spread West, and by the 3rd century it moved from modern day Middle East to North Africa and around the same time to Southern Europe. Around the 8th/9th century a dotted line shows transfer of the technology moving NW from the Black Sea towards Scandanavia, and another line folliwng the Celtic trade routes, up to Ireland and Northern Scotland, including the Shetland Islands where writers have been inspired by them since the 1700s.

These were all horizontal watermills, similar to the type shown here (by a Galician architect). They used a vertical shaft to transfer power to the grinding mills in the room above.

The vertical watermill (with horizontal shaft) developed later, could be used in areas of higher flow and larger head (height difference) and probably delivered more energy to the shaft. Some were used for cutting wood. This shot taken in the early 20th centry on the Minho river (Northern Portugal, 2mins from where I am sitting!)

My research (for MSc thesis) is about the viability of using the traditional horizontal and vertical mill sites that are dotted around Portugal and many other parts of the world, to generate useful energy. That means electrical power, but also mechanical energy that can be useful in today's modernised / industrialsed economy.

There are important differences here. In Nepal and Northern India, horizontal watermills are still very much in use due to the lack of rural electrification /a national grid. I was amazed to see how similar in design the Nepalese "Ghatta" wheel was to some of the Portuguese mills. Even the grinding stones are similar.

Since the 1980s the Nepalese Centre for Rural Technology and various other partners have been trying to improve the efficiency of these old watermills.
The key difference here is that people were still using the mills, so there was a real social and economic drive to keep them working, get them performing better. They found that the efficiency of the systems were low: at around 20%. That means most of the energy captured from the falling water was being lost throughout the system. By improving the shaft, the rotor (horizontal spinning bit), introducing bearings (rather than river stones) and other changes, they were able to reach 50 to 60% efficiency. This may be a far cry from the 85 to 90% efficiency of a modern hydro electric turbine, but it's a major improvement nonetheless.

Ashden Awards have produced a short film about these projects in Nepal, and funded their further development. Nice film, watch it here

It mentions the addition of a small dynamo, or generator attached to the mill stone. I looked into this more and more, and found a plethora of experiments with hand-made spinning mill stone generators. UK Based IT Power participated in a project in Northern India to identify feasible upgrade to their local "gherat"mills.

The outcome of both projects has been an "Improved Watermill", otherwise known as a "Multi Purpose Watermill". This has got to be the best way forward: produce power with a small generator, but have the capacity to add in various other mechanical services. These could include: grinding grains, pressing oil (think olives for Portugal!), turning a potters wheel, a sharpening stone, a wood turning thing, a laithe (?). Of course the output of the electric generator would drop when you turned on one of these other systems, but power would have been stored in batteries, and would continue to run all night when other work is resting, so it wouldn't matter.

Of course such multi purpose watermills are not available in Europe to buy off the shelf. You would have to make it yourself.

But let's compare these with what's on the market for basic electricitiy generation. Finding a micro turbine for the kind of low head settings found in most watermill sites can be difficult. There aren't many systems out there, probably because the amount of energy that can be produced is quite little, around 4MWh/year, which is more or less the consumption of a modern house.

It's late already, so I'll summarise these in the next post...

Monday, 6 April 2009

Up for air

It's been almost a month since Paulo (straw and earth building maestro / permaculture teacher) and Ruth (desert environmental school and permaculture student) arrived to help get our field camp up and running. This is supposed to be an area to accommodate a few people. A proper outdoor kitchen, somewhere to keep things clean. A toilet and shower. A bath (outdoors, log fired) a herb garden and the other essentials.

But how it has consumed all of our energy and every living moment of the days! Watermill research, thesis, blog, emails and any other contact with the outside world has fallen away...

Natalie joined the gang a week or so later, a fellow student at the CAT's environment and energy studies course.

Then my mum, Stephanie, and the kids off school, and we have a proper work site cooking along.

First major endeavour: finish that compost toilet. My Romanian uncle in-law always talks about how a toilet is the first thing you need on any building site. And after a few meals on a basic camp fire, I know what he means.

But there are outdoor toilets, latrines, holes in the ground and then compost toilets. These are completely different creatures. In fact, the creatures are what we want to cultivate in the compost version, and maintaining a good balance of carbon based substances to the nitrogen and phosphates that we deliver so regularly down the chute. Also, air. If we deprive the little bugs of oxygen, the mix becomes anaerobic and stinks big time. If it becomes too dry, it also stops the bug party and stops breaking down properly. And can also smell.

There is a lot of research and excellent publications that describe this process (and compost toilet design) in detail, but probably the best and most accessible (like free) is the humanure handbook, which is online as a PDF.

Read it and weep - at how poorly educated we have all been, all these years, about the phenomenal waste of treated drinking water we merrily flush down the pan, or the lost opportunity of viewing our waste as a valuable resource for restoring fertility and life to the soil (if it's properly composted).

I think back to the thousands of latrines I have organised or funded in disaster or post-disaster areas, like Liberia, Bosnia, Aceh, Somalia, Maldives, Eritea or Albania, etc. where we (NGOs / UN) have erected latrine blocks - on alters to the Guru of Smell. And often of public health hazard. Never in all these countries, had we considered human waste as anything but a public health nuisance. Even in the arid areas where good loamy soil is much needed to get a few trees re-established or to bring on some above ground crops.

Or in small island states (like the Maldives) where local septic tank run-off is polluting the precious fresh water resource just underground. ANd where the land is so salinated it too is desperate for some less sandy soil. Instead of compost (or better, biogas toilets) we pipe it out to sea, or make a thicker septic tank and hope for the best.

This used to get me very flustered: surely the international humanitarian community could incorporate this and a thousand other really basic ecological construction and clean energy design solutions ? Surely local universities and Governments in the disaster affected areas need access to this information, to make an informed choice?

These were some of the drivers for setting up RESET in 2007, and many of us tried to get the word out in lectures and training talks. And many are still very active, and RESET is running some training courses this summer in fact. Meanwhile, I am learning to love our bugs, and what they like to eat down there in the cool home we ave made for them, where they consumer our waste in silent and odourless darkness.

Quick summary of process:

- structure build from reclaimed wood from the main house, and some bits of pruned olive trees
- Two chambers, each about 1 square meter. For rotation, when the first if full. When second is full, first will be composted.
- We lined the chambers with a clay-sand-straw-water (cob) mix, to give it thermal mass - to regulate temperature differences, considering the extreme summer heat and cold nights.
- vent pipe installed to allow any methane to escape.

For pictures of construction of toilet, see here