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Hydro-electric power is the absolute daddy of small scale renewable energy. And of the large scale, come to think of it. For those of you lucky enough to have a stream in your grounds that has at least 2m drop over its length and over 20 litre per second flow, you should be able to produce a constant stream of cheap, reliable electricity. There may be some variation between summer and winter due to flow rates, but as long as the stream doesn’t dry up nor will your electricity. It is best to measure flows in winter and summer, as this will allow you to choose the most efficient turbine for your situation.
There are some additional things to think about. The stream is best located reasonably close to the point of use, as otherwise transmission losses will mount up. If your house is remote from the national grid, you will need batteries to store power for times of high use: there is no point having a massive turbine if most of the time the electricity is not needed, but a small one may not be able to provide peak use requirements directly. If your house is connected to the grid, it may be sensible to put in the most productive turbine possible for the stream, as you can sell excess electricity to the grid and make a profit. You should be able to get the going price per unit (about 10p per kWh at time of writing), and the Feed In Tariff scheme (FIT) will pay you an extra 3p for every kWh you sell to the grid.
The system works by water from upstream of the turbine rushing down pipes and into the turbine, where it spins the dynamo to create electricity. The more water there is and the higher it falls from, the more power there is to generate electricity.
The system needs to collect cleanish water from upstream, so will need some sort of sluice to divert water into the pipes and a filter to keep out the fish etc. It also needs to discharge the used water back into the stream, and to do all this without disrupting the stream flow or causing erosion. To this end you will need to get an abstraction licence from the Environment Agency, but for small projects of up to 20kW this should not be too onerous.
A detached house apparently needs a 5kW turbine to provide all its electricity needs. However, there is not a lot of information on this out there. A hydro-turbine will run 24 hours a day, 7 days a week and an average three bed house uses around 5,000 kWh per year. There are 8736 hours in a year, so surely a turbine capable of producing 1kW all year round will provide much more electricity than an average house would need? I presume therefore that the 5kW figure includes running the heating and hot water systems, rather than just supplying electricity for lighting and appliances etc. Our average house would use about 25,000 kWh for all its power needs, so this seems more reasonable.
Cost seems to depend a lot on the amount of design and civil engineering works required to get the system up and running. The general wisdom says that low head systems, which run on water falling about 2m between inlet and outlet pipes, will cost £4,000 per kilowatt of installed generating capacity. Medium head systems, which run on water falling about 10m, cost a minimum of £10,000 plus an additional £2,500 per kilowatt of installed generating capacity.
However, there are apparently fairly effective and robust turbines for sale for low and medium head application for around £1,000 per kilowatt. The companies selling them seem kosher and technically competent, with some degree of DIY possible, so it may be possible to get a viable system up and running for a lot less that the £20,000 or so that is usually touted as the minimum.
Most micro-turbines will not need much maintenance, but greasing the nipples on the bearings is probably worth doing every month for most models. More involved servicing will probably be required periodically.
Payback is rather hard to calculate. I will assume that the £20,000 normally quoted gives a 5kW capacity. If this is only enough to provide electricity for a largish detached house, then it will probably save around £800 a year on bills and bag you around £1,000 in FIT payments. This gives a payback of around 11 years. However, if it covers all electricity and heating needs, then savings will rise to nearer £2,000 and payback reduced to 7 years (heating is no covered by FIT - it only pays you for the electricity you produce). If anyone knows more, please share your knowledge with us in the Forum.
Companies that caught my eye when researching this are:
Navitron have some useful information and inexpensive products that appear to be perfectly adequate. If you give them a ring they will help you choose the best turbine for your situation, but they presume that you know what to do with it. If you don’t and need help designing and installing the system as a whole, they can give you the name of a local installer who will know what to do.
Powerpal appear to have a good range of robust turbines at low cost, some of which produce AC 230V power that can plug directly into your household ring main. The Powerpal posse are also experienced engineers practicing worldwide, so should be able to help out with design and installation in whatever way you need.
Hydrogeneration come across as being a bit more polished, with more emphasis on their feasibility studies, design of appropriate systems and engineering works needed to install it. This probably results in some upfront costs and a higher overall spend, but with a top quality result giving maximum performance for the location. This is probably the option for those of you that know nothing about hydro-electric, don’t want to research it and don’t want to do any DIY on the project.
Alternatively, you can do a regional search for certified microgeneration installers at greenbook. They also have lists of certified microgeneration products.
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