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Commercial Solar Thermal: Dairy Farm Case Study

120x Evacuated Tubes

Rhiwlas, Bala, North Wales

cows in a field

Acres: 170

Number of Cows: 450

Wash-downs: Daily

cows ready for milking

Existing water heating system:

900 litre Cotswold Dairy Heater using 2x 6kW Immersion Heaters

Temperature Required: 85 DegC

Daily Electrical usage: 200 kWh

Annual running cost: £12,0000 at 17p per kWh

preparing a heat exchanger


To install Solar Thermal to supply hot water and offset electrical heating cost.

solar thermal panels being installed

Equipment to be installed:

4x Navitron 5830AL Evacuated Tube Panels

320 litre buffer tank / heat dump

20kW Heat Exchanger

Controller and Pumping Station

Heat Meter

a thermal store being installed

a 20kw heat exchanger

System before installation:

heat recovery schematic

Schematic of Solar:

solar thermal schematic

How it works:

The solar thermal primarily heats the 900 litre Cotswold Tank via heat exchanger to 85 degC. Once satisfied the heat is diverted via 3-port valve to the 320 litre thermal store. Water from the heat recovery unit is passed through this thermal store to collect any additional heat within before being sent to re-fill the 900 litre accumulator thus acting as a pre-heat.

navitron solar collectors installed on a dairy

Peak Output: 7404 W

Total Aperture Area: 11.32 m2

Zero loss collector efficiency 0.654 n0

Total Annual Irradiance for 1 m2 on 15 degree pitch: 1106.47 kWh

Expected Annual Savings: £1392.55

Expected Year of Return (on current utility tariff): 8

Equipment Supplied by: Stoves & Solar

Video Case Study...

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