Solar thermal system to heat oil at food factory
Novel solar thermal technology is being used to heat oil for making potato crisp
Technology developer Rackam Solar, a spin-out from Sherbrooke University in Canada, said that its system — being installed at a plant near Valencia — can be used for any industrial thermal process, including pasteurisation, cleaning, drying and sterilisation.
The company believes there is a gap in the solar thermal market for process industries, especially those that use lots of heat such as the paper, food and chemical sectors, in between the relatively mature sectors of domestic water heating and grid-scale energy generation.
Rackam’s system uses parabolic aluminium mirrors mounted onto an epoxy base to focus and concentrate energy from the sun to a central tube containing either water or oil as a carrier medium.
The fluid, which in the case of oil can be heated to 220°C, is then pumped downstream to be used directly; passed through a heat exchanger to a second medium; or stored for later use in a ‘thermal battery’ consisting of a phase-change material. A simple suntracker sensor and mechanical device allows the mirrors to follow the sun.
‘We are reaching efficiencies of 57 per cent at the output, which is quite high if you compare that with PV [photovoltaic] cells that typically run below 15 per cent,’ Rackam director Samuel Richard told The Engineer.
In the Papes Safor food production plant, a total of 280m2 of mirrors will be installed in six 14m-long rows along the roof. The carrier oil will be taken to a heat exchanger where it will transfer energy to the frying oil.
The facility currently burns 235,000 litres of diesel a year in order to heat the frying oil, but aims to reduce that by around 30 per cent, thereby saving €30,000 (£24,000) a year.
The total cost of the project is €150,000 (£122,000) and Rackam believes that the plant will see a return on its investment in slightly more than five years.
‘The reality is most of the projects that we’re going to have are going to be retrofits,’ said Richard. ‘Of course, if we had the opportunity to start from scratch and were able to put our constraints into consideration at the design stage, that would be easier and potentially cheaper for the customer.
‘That way, it would reduce their traditional boiler size, whereas when we’re retrofitting we’re not going to change their boiler system — it doesn’t make sense.’
Ultimately the aim would be to persuade food production companies, for example, to set up in locations best suited to solar thermal and fully integrate the technology.
‘If we’re competitive doing retrofit, that will make us even more attractive for future projects,’ said Richard.
