The answer to our energy conundrum is elementary
Water and wind are the two vital elements that can be harnessed for small-scale, sustainable power generation, says Anthony Harrington
WITH interest in small-scale hydro power generation schemes on some of Scotland’s fastflowing streams and rivers continuing to grow, this microgeneration strategy has a great future ahead of it.
Andy Knight, managing director of TSL Contractors, reckons his firm has an exciting pipeline of work and has already completed six schemes.
Small-scale hydro schemes, he points out, are generally a partnership between the client and the developer, who prepares the necessary hard structures and pipe runs, plus the building that will house the turbine.
“Usually the turbine itself is procured by the client from one of the mainstream turbo suppliers and we assist with the installation,” he explains.
The basic pattern is for the contractor to build any required access roads, to lay the concrete barrier across the river and to construct the pipe run that will parallel the river and channel water directly to the turbine. The drop between the start of the intake pipe and the point where the pipeline connects to the turbine house is known as the “head”.
The amount of power produced by the scheme is a function of the combination of the head and the pressure, or flow volume, of the river.
“Hydro schemes are based on the idea of about 40% efficiency in power output, which means that the scheme is expected to run at full capacity about 40% of the time,” Knight explains.
The concrete barrier across the river is generally a very low affair, rising no more than a metre or so above the surface and is there just to create a modest head of water. Therefore there is very little visible impact on the landscape. What it does is to provide some stability to the flow but if Scotland is experiencing a dry summer the hydro scheme will produce little or no electricity until the autumn and winter rains get the river or stream flowing again.
Similarly, a really cold winter that caused the river to freeze over would also bring power production to a close.
This could be a major drawback on a scheme’s viability were it not for the fact a significant part of the demand for electricity comes during the winter, to provide heating, at which time the rivers are usually pretty full.
“The average scheme is about 500KW, though small scale hydro installations can range from as little as 50KW to 2MW.
“A 50KW scheme will comfortably meet the electricity requirements of several houses,” Knight says.
A ball park figure for a hydro scheme of 500KW would be a capital expenditure of around £1 million to £1.5 million, while a larger scale scheme, of the order of 2MW in capacity, would cost anything up to £3 million, Knight says.
The government’s feed-in tariff is critical for most hydro schemes to get off the ground, and there is some concern in the sector as to how the coming general election might influence future pricing of the feedin tariff.
“If the feed-in rates were to be drastically reduced, that would definitely make a difference to the future of small scale hydro,” Knight says.
There are a lot of schemes currently in the planning stage and demand should stay brisk for several years to come, provided the government does not change the rules of the game, he notes. In all, TSL has now com- pleted six schemes, with four more under way and three others in the planning stage. The company is about to expand its business to the east of Scotland with the appointment of a new key person to head up its construction business in the area surrounding Aberfeldy.
“We continue to grow but as well as demonstrating we are an extremely professional and capable company, we don’t want to forget our roots as a familybuilt company committed to the community from which it has grown,” Knight says.
A BreAth of fresh Air
By comparison with hydro power generation schemes, which are obviously completely dependent on access to a river capable of meeting the scheme’s flow requirements, micro generation from small-scale wind turbines is much more widely available as a solution. Paul