A range of options on renewables

There are lots of renewable energy options available for dairy farmers. Jim Campbell, of the renewable energy team for SAC Consultancy takes a look

Before thinking about renewables it makes good sense to look at your energy usage and take steps to minimise it where possible. In the dairy industry savings can be made in heating water, cooling milk and driving the vacuum pump – particularly when your system is getting on in age.

Fitting a variable speed controller to the vacuum pump, for example, can cut its electricity demand by 50%. With current incentive schemes, payments can be received for energy produced from renewables whether or not the energy is used on site. However, there is no point in producing it to waste it in inefficient equipment when you could be getting an extra payment to export it.

Incentive schemes

The incentive payments available are Renewables Obligation Certificates (ROCs), Feed-in Tariffs (FiTs) and Renewable Heat Incentive ( RHI ) payments. Following recent changes, for new projects ROCs will generally only apply to larger schemes of more than 5MW installed capacity.

Feed-in Tariffs payments will apply to smaller scale renewable electricity projects and RHI payments will apply to renewable heat projects.


Choosing the most suitable technology for your site will depend on a number of issues including;

❚ The resource available for each particular technology.

❚ The constraints applying to that technology at your site.

❚ The balance between your demand profile and the likely generation profile of the technology.

Solar photovoltaics (PV)

A 50kW PV installation on a southerly facing roof is likely to have an annual yield of about 40,000 kWh in the UK, but a site- specific yield estimate should be carried out which will consider the orientation and pitch of the roof and the location of the site. Installed cost for this size of system is currently about £60k and at current tariff and energy prices this will be paid back in less than 10 years. Payback will be reduced where more of the energy is used on site. PV’s biggest output will be in the middle of the day in the summer months and therefore refrigeration loads are quite well matched with PV output.

Wind energy

On a good site a 50kW wind turbine will yield 130,000kWh with payback within six to eight years. However, it is important to have some confidence in the wind speed at your site before committing to a project. This size of installation is likely to cost in excess of £250k. Planning approval for a wind turbine can be difficult to obtain and effort spent at the feasibility stage is well worthwhile.

Anaerobic Digestion (AD)

Feedstock supply is one of the most important issues when considering an AD plant. Cattle slurry is a convenient feedstock and the resultant digestate has some benefits over raw slurry as a fertiliser. However, slurry on its own will provide a low gas yield and to justify the cost of the plant, an additional higher value feedstock is desirable. Maize or grass silage are the most likely candidates on a dairy farm and obviously crop grown to feed a digester is not available as stock feed.

A use for the heat produced by the plant will also improve the viability, RHI payments being available for heat exported from the plant as well as FiTs for electricity generated. When considering an AD installation it is crucial to consider in detail how it will integrate with the overall farm business.


For a viable hydro scheme the combination of head and flow has to be sufficient and the environmental constraints acceptable to the regulators. A head of less than 3m is unlikely to provide a reasonable financial return for a small scheme. For a low head scheme (up to 10m) the drop needs to be over a single weir (preferably already existing) or waterfall or at least over a very short stretch of river.

High head schemes on steep hill streams are generally cheaper to install as the turbine will be much smaller for the same output. Costs are very site specific as are yields and the cost per kW installed tends to increase as scale decreases. Ten year paybacks are considered reasonable for hydro, but life expectancy is generally long.


A biomass boiler (wood pellet or woodchip) for farmhouse heating and provision of hot water for a dairy would be eligible for the current RHI scheme. When compared to oil or lpg the additional capital cost of a biomass boiler could be saved within six or seven years with RHI payments continuing for 20 years.

FiTs rates

    FiTs are paid in two parts; the generation tariff which is payable on all energy generated even if used on site, and an additional export tariff for energy fed into the grid. Payment rates depend on the type of technology and the scale of your installation. The rate you get is set on the date that your installation becomes registered with the regulator, OFGEM and is paid for 20 years, being index linked over this period. The rate for new entrants is reduced according to the anticipated installed capacity across the country as calculated during the preceding time period. For PV the time period is three months and for other technologies it is one year. For current rates refer to the OFGEM website at www.ofgem.gov.uk

Solar thermal

A solar thermal installation properly sized to match your hot water demand is eligible for RHI payments and will reduce the energy requirement from conventional fuel sources. Most of the time in the UK climate a boost from another heat source will be required to achieve the temperature required to avoid the risk of legionella in stored water.

Access Options

Problems like grid connection and planning permission can add considerable cost and time delays to a project and with changing tariff rates, what started out looking like a no-brainer can easily become border line by the time it is completed. Advice from an independent consultant at an early stage is highly recommended.

Renewable Heat Incentive

    The RHI is a scheme designed to encourage the installation of renewable heat technologies by making a payment for every unit of heat produced over a set time period. The scheme includes biomass boilers, solar thermal panels and ground source heat pumps, as well as some larger scale technologies. There are two RHI schemes:

    Non-domestic RHI:

  • Open to renewable installations heating businesses, commercial buildings and domestic houses on district heating schemes (almost any building with an eligible heat use that isn’t a single, domestic property).
  • Opened in November 2011
  • Makes a payment for every unit of heat produced, for 20 years (index-linked).
  • Where a scheme provides hot water for a dairy and heat for a farmhouse it would fall under the non-domestic scheme.
  • Current rates can be found here;
  • Domestic RHI:

  • Eligibility will be linked to the Green Deal – more on the Green Deal can be found here: www.decc.gov.uk/en/content/cms/tackling/green_deal/green_deal.aspx
  • Equipment and installers will need to be MCS certified.
  • Payments are likely to be over 7 years and made on a deemed basis (a calculation of the expected heat usage rather than actual heat usage) unless a fossil fuel system is also installed or retained, in which case a heat meter is likely to be required
  • Proposal that installations larger than 45kW will be excluded from the scheme.
  • The scheme will open for applications in summer 2014.

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