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Introduction to Run of the River Micro Hydropower
Micro hydro power can be used to supply your home with renewable energy in the form of electrical power. The amount of power produced by the device depends on the stability of the flow of water, in terms of a fast and steady flow.
Once a suitable site has been found, planning permission must be sought from the local council and the environment agency. They will want to know what impact the scheme will have on the local flora and fauna as well as the locals. They will also require the design of the system including the projected capacity. Several energy suppliers should also be contacted as they may purchase any surplus electricity you generate.
This is another article in my series on the use of domestic renewable energy, and we shall examine the surveying of a suitable river site, the type of water turbine to use for optimum efficiency, and how a micro hydropower system operates.
So we begin with having a look for a suitable site along a fast flowing river near to your home.
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Selection of a Suitable Site
There are a number of criteria to meet when selecting a site as follows,
- Is the river close to your home?
You will need a local access to the river to transport and install the components your micro hydropower unit. You will need to consult the land owner(s) regarding access. Also and you don’t want to be too far away as it will need careful attention during commissioning and the initial operating period.
- Is the river consistently fast flowing all year round?
This will require you to have details of the rivers characteristics which can normally be obtained from the local environment website. There will obviously be locations where the flow velocity will increase as the river deepens, narrows, or changes it incline.
- Are fish in the river, or are any protected species of wildfowl or flora close by?
Talking to the local anglers will give you the information on the fish frequenting the river, spawning times of the year etc. Also a good chance to sound them out for reactions and making offers such as fish restocking and building a few fishing huts along their chosen stretches of the river.
The local wildlife association will have the info on the wildlife and any wild plants, but be prepared for some opposition from them towards your proposals.
- Will you be able to export power back to the grid?
If so you will need to consult the District Network Operator (DNO) at an early stage, to discuss terms and conditions etc.
After answering all these queries with a successful outcome, it is worthwhile to engage a professional hydro power engineer who specialises in micro projects. He can survey the site in a few days and his report if positive can be added to your planning application. It won’t be cheap but can save valuable time and money further down the line (costs estimate between £500 and £1000)
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Selection of Micro Hydropower System and Turbine
There are numerous micro power systems operating in all parts of the world, the popular ones are listed below:
- High and Medium head systems
These include canal and penstock systems
- Low head systems
Mill leaf systems
- Run of river systems
Small Barrage Systems
In this article we will use a run of river system as it is much easier to get planning permission for a simple system, such as a run of river system. This does not require a section of the river to be diverted across the land to run your system and will have the least effect on the river and surrounding ecosystem, only requiring a small barrage to one side of the river.
Typical Run of River Build Method
A temporary barricade is placed across the area where the device is going to be installed.
This will divert the water long enough for you to scoop away the sediment from the bottom of this part of the river, allowing a concrete plinth to be installed. Once the plinth has hardened, the permanent barrage in the form of an L shape can be fitted behind the temporary barrage and the turbine and generator bolted to the concrete plinth.
This L shape barrage can be fabricated from steel plate, the rear plate incorporating the turbine and the generator. This plate can be held in place using vertical steel guides to facilitate removal of the whole unit for maintenance. The device is then connected to the transformer/ voltage regulator which should include an isolation breaker.
A mesh screen is now fixed across the inlet channel to your turbine, preventing fish being drawn into the turbine as well as collecting any debris brought down by the river.
If the river is a salmon run, then a very fine mesh with than 12mm spacing is required by law to prevent smolts (young salmon) being caught up in the system.
The temporary barrage can then be removed to supply the turbine with water.
The turbines best suited to a run of river system are reaction turbines which are totally submerged in the river. These include various propeller types and Francis turbines.
We shall use an open flume type of Francis turbine, which is one of the oldest but reliable water turbines with many still in use after fifty or more years of trouble free operation. It consists of an open wheel which is fully submerged in the water current which causes it to rotate, driving a power generator.
The water leaves the turbine through a conical outlet pipe connected to the tailrace which returns the water back to the river.