Dairy farm set to save thousands thanks to solar thermal installation

The recent energy crisis has pulled into sharp focus for all businesses the rising cost of gas and electricity; but for dairy farms, where the energy need has always been high, the current spikes in unit costs could force thousands of UK farmers out of business. 

With the government’s energy price guarantee set to end in August, the global supply of gas still disrupted and energy firms enjoying record profits, a fall in utility bills for farmers is unlikely to happen any time soon.

For such farms to survive, there needs to be a dramatic rethink on how they get their energy, and this is something a Dairy Farm near Bala, North Wales, has done, with the support of Remote Power UK, and their partners at Horisun Renewable Energy.

Rhiwlas Farm has 450 cows on a daily milking cycle and was seeing an electricity bill nearing £12,000 per year.

The majority of the electricity usage was in the 900L Cotswold Dairy Heater which uses two 6kW immersion heaters to heat the tank to 85 degrees Celsius daily, for wash downs.

Already in place at Rhiwlas was an FGAS heat recovery system and milk heat exchangers, as you’d expect, but the farm needed a more cost-effective way to get that heat into the store in the first place without having to compromise or replace any existing equipment.

The solution – solar thermal 

You probably know that solar energy can be turned into electricity by using solar panels, but there’s another popular application to the sun’s power. Solar thermal panels can turn sunlight into heat (instead of power).

Whilst everyone has heard of standard solar panels (solar PV), solar thermal actually carries a number of benefits for dairy farmers, including:

• They are more efficient than PV panels, because heat waves carry more energy than sunlight, and because there is no process of transformation into electricity.
• They are cheaper, meaning they have a shorter payback period than PV panels.
• They work in cold climates, overcast weather and strong wind, and incorporate an energy storage system.
• They require little to no maintenance, so the only expense you’ll have to worry about is the installation cost.

Solar thermal panels heat water using evacuated tube technology which makes them approximately 65% efficient, compared to Solar PV which is only approximately 17% efficient.

This process of converting electricity to heat suffers efficiency losses, whereas the heat produced by a solar thermal system is used directly within the hot water tank.

For example, 1kW of sunlight captured using PV panels will only convert to approximately 0.17 kW of heat in water, whereas 1kW of sunlight captured via solar thermal will equate to approximately 0.65 kW of heat in water.

You would need to quadruple the area of Solar PV to achieve the same gain as Solar Thermal.

If water heating is the desired outcome there is no more efficient and affordable renewable technology on the market than solar thermal.

The solar thermal system is set to save approximately £1400 per year on water heating costs. At the current tariff rate that will see a return on the initial investment of £12,000 in 8 years.

It will be faster if (when) gas and electricity prices from energy firms rise.

In the month of May this year alone, it has generated just under 1000kWh of heat.

Farmer Ian said: “I am delighted with the system. I wish we had thought of it sooner. Why these systems are not more commonplace on dairy farms, I don’t know?

“Perhaps it is because farmers are not aware it is an option or think they need to spend a fortune on Solar PV [electric] panels instead?”

The installation at Rhiwlas Farm

4x Navitron evacuated tube solar collectors, totalling x120 tubes in banks of x30, were installed on the south facing roof of the dairy.

Giving an aperture area of 11.32 m2 absorbing the sun’s rays during daylight hours 365 days a year.

Inside a pumping station sends the heat generated from the solar panels primarily to the 900 litre Cotswold tank via a 20kW heat exchanger externally fitted.

This pump is operated by a temperature difference controller which looks at the temperature on the panels against the temperature in the store and as long as it is 10 degrees higher than the tank, starts pumping that heat in.

Also installed was a 320 litre thermal store with a diverter valve, operated by the same controller. This acts as both a heat dump and a buffer vessel and is integrated with the existing heat recovery system.

When the Cotswold tank has reached the desired 85 degrees Celsius needed for wash downs, the solar heat is diverted to the thermal store.

When the Cotswold needs re-filling, water from the heat recovery unit also passes through the new thermal store to act as a pre-heat.

Meaning the requirements for heating the Cotswold are already partly satisfied before it has even started, further lessening the requirements of the immersion heaters if and when they need to be used.

Horisun Renewable Energy are specialists in solar thermal technology and have been involved in the industry since it became a mainstay on the UK market in the early 2000s.

They offer solar thermal systems, solar PV and heat pumps nationwide on both a domestic and commercial scale.

Chris Steele, installation manager for Horisun Renewable Energy said, “We were delighted to work on this project with Remote Power UK and Rhiwlas and get to spend some more time in Wales.

“I have always maintained that solar thermal should be considered a no-brainer where large hot water needs must be met. It is great to see this dairy farm getting on board with the technology.”

Horisun Renewable Energy company can be contacted on 01572 725511, via email at info@horisun.co.uk or via the website www.horisun.co.uk

You can read more about the installation at Rhiwlas via the blog on our website or by watching the video case study on YouTube put together by Stoves & Solar, the UK’s leading suppliers of solar thermal equipment.