German poultry producers have for some years enjoyed government subsidies helping them invest in solar panels and wind turbines.

This has resulted in the German landscape becoming increasingly dotted with mirrored roofs, as the poultry sector becomes a significant generator of green energy.

Back in the UK, the lack of a similar scheme has been a major obstacle for producers wishing to use their roof space. But as Damian Baker of RenEnergy, Norwich, points out, this is set to change next April with the launch of the new Feed In Tariffs (FITS).

The government’s aim is to increase the uptake of small-scale renewable generation (<5MW) and help deliver the UK’s 2020 renewable energy targets.

Under the scheme, generators are guaranteed a fixed price for power generated over a 20 year period. Tariffs are available for wind, solar photovoltaic, hydro, anaerobic digestion, biomass and biomass combined heat and power (CHP). While still to be confirmed, the proposed tariff for a 4-10kW photovoltaic solar panel is 31p/unit.

So looking at a poultry unit with 100sq ft of roof space, the initial capital cost of installing 70 solar panels generating 11,000kW hours a year would be about £65,000, says Mr Baker.

“The 31p/unit tariff equates to an annual income of £3000 for generated power and if you use this energy yourself, you effectively get an extra £1300 in saving from not having to buy this power,” he explains.

His costings suggest that the solar system would pay for itself within 13 years and by the end of the 20 year period, it would have generated up to £40,000 of income.

Photovoltaic sun cells work by directly converting light into electricity at an atomic level. These panels are made from a material that absorbs photons of light and releases electrons. It then captures these free electrons, creating an electric current.

Multiple panels are arranged to form an array producing direct current (DC) which may be used directly or converted into alternating current (AC) via an inverter. Most “on grid” applications for commercial uses would convert the DC into single or 3-phase AC and are connected to the main grid supply via a generation meter.

“Panels are robust with a long life-span. All photovoltaic solar panel manufacturers guarantee output to remain at 80-90% over the 20 year period. All that is required is the occasional cleaning of the panels to remove dust,” says Mr Baker.

Looking at a smaller scale example of a single poultry shed, the capital investment would be £25,000 and it would pay back within 10-12 years.

Tariff rates are also available for wind energy. For a 1.5-15kW system, the tariff is 23p/unit generated and he calculates that it would pay for itself within 12-14 years.

However, he adds that by having moving parts, wind turbines do require more regular maintenance than solar panels.

He recommends combining both solar and wind, as they complement each other. “During winter when there is less sun, there is often more wind and so the combination gives you a more constant output of power.

“These tariffs come in April 2010, so producers need to start thinking about it now,” he says.

This is particularly the case as the tariffs will only apply to systems installed before April 2011. Systems installed after this will be subjected to lower, less generous rates.

Horizontal versus vertical

Broadly, there are two types of wind turbine: Vertical axis and horizontal axis, or VAWTs and HAWTs.

HAWTs have a horizontal rotor shaft with a generator at the top and the whole thing needs to be turned into the wind to function. Usually three-bladed, they use a gearbox to boost rotor speed to a level suitable for the generator.

Though efficient when turning, they need to be started (using additional energy) and require higher wind speeds to run than a vertical unit.

Vertical axis turbines are, on the whole, simpler pieces of kit. The main rotor shaft is arranged vertically, meaning the turbine doesn’t need to be pointed into the wind to function.

VAWTs are also bird and bat friendly, a big plus for planners. They are also relatively quiet. A 10kW turbine measures about 45dB when you’re standing next to it; move 20m away and the noise is negligible.

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