Justin Broadbent from ISO Energy explains the options available for extracting energy from water on your plot of land.
Interview with Justin Broadbent
Water gives more energy than wind because of its density
There is a long history of using watercourses to drive mechanical objects in the UK. Although grain grinding was wind-powered, the mills of the early Industrial Revolution were driven by water because of the amount of power in it.
Extracting heat from water can be simple and efficient
If you have a small stream running through your garden, the simplest and most worthwhile thing you can do is extract energy in the form of heat. Justin says, “If you have the right spot and you have the right watercourse, then it is fantastic.”
Any water can be used for energy extraction
A large pond can be used for extracting heat; the amount of energy depends on the size of the pond and the heat load required. A flowing river has a constant temperature of 7 to 12 degrees, and a pond can get much warmer.
If there’s a flow in and out of the pond, the energy is effectively being replaced all the time. With a stream, the energy is quickly replaced so more heat can be extracted.
Choose the correct heat extraction device
In a pond with fairly slow running water, Justin would install a simple mechanism that extracts heat using coils of plastic pipe.
In slightly flowing water he would use ‘Energy Blades’. These banks of stainless steel ‘radiators’ extract an enormous amount of energy. Justin explains, “Almost whatever you take out, as long as you don’t actually freeze the water, two seconds later, there’s new fresh water coming down the stream.” Such systems can be scaled up to extract hundreds of thousands of kilowatt-hours a year, by putting in banks of multiple radiators.
You may need planning permission
In an area of outstanding natural beauty you must obtain planning permission for works like these. Additionally, Justin says you would need permission from the Environment Agency to dam a river or stream, but not if you wanted to put an Energy Blade in the water as it’s easily removable.
Expertise is necessary but installation is relatively straightforward
Justin says that extracting heat from water is cheaper and more efficient than from the ground, which is not as straightforward. He says it’s worth employing professionals but essentially, if you’re fortunate enough to have a stream, you can easily install an Energy Blade for two to three thousand pounds. To do the same in the ground, he estimates a cost of five or six thousand pounds.
Heat extraction doesn’t have to be hugely invasive
Some of Justin’s clients make a feature of how they’re heating their house, for example diverting part of their stream, and adding a canal and viewing walkway. But you can simply put the energy blade in the stream and dig a small trench back to your heat pump.
Hydroelectric generation ideally needs both volume and flow of water
To generate electricity from water, you need the water to drop enough between the top and bottom of the stream. The greater this ‘flow’ or ‘head’, the more power you can generate. Justin summarises, “In an ideal world you have head and volume and then you can build a traditional turbine. If you don’t have the head, then you have to have even more volume.”
Traditional hydro systems are built near big mountain rivers in places like the Alps, Scotland and Wales. The right features are not easily found in the south of England and where they do exist you’d be unlikely to get planning permission.
If you can’t have a turbine, look for old water mills
In Southern England, generating electricity from water is rare. However, Justin’s company has converted several mills where turbines can’t be used but the volume in the hill stream is sufficient to drive an ‘Archimedes Screw’, where the flow of water turns an electrical generator.
The same feed-in tariff for photovoltaic cells applies to an Archimedes Screw
Some of these systems generate a constant 15 to 20 kilowatts of electricity an hour. As this is far more than a single house needs, you can sell the surplus back to the electricity companies. Justin adds, “If you have photovoltaic panels on your roof, they might produce a few kilowatts. Well, an Archimedes Screw should be able to generate tens of kilowatts. Much more efficient.”
These are low maintenance, robust systems
Energy blades are fairly static and require very little maintenance. As they are stainless steel they don’t rust and have quite a long lifecycle. Furthermore, they are protected by guards built on the front.
Likewise, Archimedes screw systems are heavy but fairly basic, just needing the bearings replaced when they eventually go and some maintenance of the gearbox.
Environmental considerations can add costs
Heat extraction in streams won’t affect wildlife, as the amount of energy taken out is so small in relation to the volumes involved. A pond cooling may affect wildlife slightly, but Justin is reassured that those species survive lower temperatures in Scotland.
Justin explains that you can’t block a stream completely to use the power of the water. One common, though costly, method to ensure that fish, eels and animals can get by is to use a ‘fish pass’. A maze of gradual drops allows fish to swim upstream, avoiding the mechanism.
You get less return on investment with a smaller system
There’s not much difference in the cost of a small system producing five kilowatts and one giving 10 to 20 kilowatts of energy, because of the costs of getting permissions, civil engineering and manufacturing. Justin explains that his company rarely works on systems that are producing less than 20 kilowatts. “Suddenly you’ve found that it’s all going to cost £150,000 and you’re only going to make £5,000 a year out of it. It doesn’t pay back.”
|5 kilowatt Archimedes Screw||£15,000|
|20 kilowatt Archimedes Screw||£60,000|
|Planning permission / consultant’s time||£40,000|
It’s worth investigating how to use any water source on your plot
You may be able to generate electricity or heat, or even both, from water on your land.
With current government incentives (those for generating electricity normally last 20 years, and about seven years for heat), Justin calculates you can get your money back on a heat system within three to five years, followed by hugely reduced running costs.
And you might even be able to get government incentives to support the construction of the system. “So, it’s definitely worth doing,” Justin says, “So long as the government grants are out there.”
Find out more
Visit the website of ISO Energy