Micro hydro – is it worth it?

“Is micro hydro worthwhile?”

This is a question I get asked a lot. Finding an answer is rarely straightforward.

Part 1: Resource investigations

My reply will begin to counter with a stream of questions something like “Is it a fast flowing river; is there a good fall?” This will be followed by “What do you want to do with the power; Have you done any research, How will the project be paid for?”

More often than not, a location and opportunity spotted have set someone’s synapses firing and expectations are already heightened… I am thinking, I do hope I’m not going to be the one who has to pour a bucket of cold water over the proceedings.

OK, we’ll start with an easy one … “Where are you?”

The World Wide Web provides opportunities to start digging. After all, you’re reading this marvellous blog aren’t you?? Even whilst on the phone, digital maps and satellite images then provide  a means to swot up quickly on the site. As I have come to learn, hydropower is all about location, location, location.

You may have already taken measurements to estimate the size of your ‘head’.   Precise knowledge of the change in water level across the available land and, for lowland sites, how this varies will solve the first part of this puzzle. [… no, I don’t want to know the diameter of your cranium.]

For an upland site with a fall across it of more than ten metres, we could take a look at a contour map to begin to get a feel for the change in levels and gradient, referred to as the ‘head’. Contour maps can be found on-line for some countries. For a lowland site browsing a satellite image could be useful to get an understanding of how the waterways connect and sometimes divide… we might then venture onto Street View and attempt to peer over a bridge or fence to look at a weir before we visit in person. A weir is one obvious place where an abrupt change in level occurs. If some water is diverted into a channel at this point (leat, goyt, laid etc) with an old watermill at the end, then the level change further downstream is likely to be greater.

More questions might spring to mind at this point during the interrogation: “Do you own the land? Where is the boundary?” […in other words can we stretch the layout to gather more ‘head’, do you need to talk to the neighbour or are you already part of a community of several land-owners with a shared vision of luxurious water-powered retirement?]

The conversation about head could progress on to talk of survey equipment, dumpy levels, and even altimeters for rapid estimates of level changes at upland sites.

Micro-hydro Stream

“We have a lot of water and it is always flowing” …. so no worries there then?

Er…, not quite.

Let’s start with the river; does it have a name?

If it is a big one there should be a gauging station somewhere where water flow rates are measured. Now that would be something useful; historical data going back decades in some cases! Surely that must give some indication of what the future holds? Well we’ll keep our fingers crossed on climate change… Some generous governmental organisations make this data available for free … the collection and admin is paid for by your taxes after all. You may be able to locate the date by searching the National River Flow Archive for historical records.

“Have you tried to measure the flow?” If the river is fairly small you may be able to float an orange between two points and work it out that way (search for ‘velocity–area flow measurement‘). If it is a small stream, trying to divert the flow into a large receptacle could give you an idea of what the stream is doing today. If the bucket fills instantly before being promptly swept from your grasp then initial indications are good.. well, we’ve got to start somewhere and it might as well be by getting soaking wet, right?

We’ll get on to flow splits, efficiency, generators and all the rest of it in due course, but at least that has hopefully got you looking for those rubber boots and checking the fruit bowl.

Don’t forget, to begin with its all about the the head and the water flow at the location. The more precise information your can gather about these the better.

In Part 2 we’ll take a look a what kind of marvellous machine might help us harness some of the energy from all that water rushing past your feet.

Phil Maher

Useful links

www.getamap.co.uk – Online ordnance survey maps for UK

Google Maps – Satellite images and street view

Google Earth – Satellite images and elevation profiles

National River Flow Archive – UK Gauging Station information

Hydromatch DIY guides – Flow and head measurement guides