The essential journalist news source
Back
22.
September
2016.
Solar thermal hot water within the food industry

[image]

 

PR37875

22 September 2016

 

Paul Sands of Stokvis Energy Systems examines how solar thermal hot water can best be utilized within the food industry.

 

Taking Storage Out Of The Firing Line

 

[image]

Stokvis Econoplate plate heat exchangers with solar panels,

solar store, pump and controls.

 

With the exception of mushrooms, pretty much everything we consume depends on the sun to help it grow and ripen. All life on Earth, is to a huge extent, dependent on the energy we receive from the star at the centre of our solar system; yet there is still more benefit to be derived from this vast fusion reactor, that bathes the planet with light and heat.

 

Since early Victorian times, industrialists built the roofs to their factories featuring ‘north-lights' to provide optimum amounts of free illumination, while good architectural design today helps most types of building benefit from passive solar gain.

 

However, the UK is still lagging behind most of its European partners in the uptake of solar energy; either solar thermal or photo-voltaic, and more understanding of the technology is essential if best use is to be made of this truly renewable resource; particularly with respect to process water.

 

In the domestic environment, solar collectors are normally linked via a pump-station, to a twin-coil cylinder which will also be fed from a conventional boiler or, perhaps, a heat-pump. This arrangement is perfectly satisfactory in many ways, and can provide the average household with up to 60 per cent of its hot water needs during the year.

 

When looking at commercial applications for food production or food processing plants, the dynamics of demand are very different, and the way the solar energy inputs into the equation needs to be reconsidered.

 

Production facilities are likely to be operating over long working hours, possibly with a two or three shift system. This will almost inevitably mean using very large amounts of hot water at medium to high temperature, for washing vegetables, animal carcasses and equipment, or actually mixing it into processed foods.

 

Again solar panels will only be able to meet part of the demand, although the way the system is designed and set up can make a big difference to efficiencies; and consequently fuel or cost savings.

 

Commercial premises will almost certainly be equipped with modern boilers running on gas, or some other form of fossil fuel, to offer reliability of both heating and hot water. But having even the latest modulating gas boilers firing into large buffer vessels as a means of providing process water does not present the optimum answer.

 

Even well insulated storage vessels will lose heat whether water is being drawn off or not, causing the boiler to cycle on and off, as the temperature drops. Having solar coils connected into the system here will not alter the situation. Fuel will still be wasted in maintaining the temperature, while there is also a need to provide a boost to kill the Legionella bacteria on a regular basis.

 

It is far more efficient to have an array of solar panels storing the free energy collected within what serves as a preheat storage vessel. This way incoming potable water from the mains or a borehole can be raised from around 10 to the temperature required, or if the Solar gains are not adequate, some temperature in between. Then when the temperature of the water requires raising to the required set point, the boiler in conjunction with a plate heat exchanger (PHE) achieves this efficiently and instantaneously.

 

What is more, because both modern modulating gas boilers and the PHE units feature low water content, there is very little thermal inertia and energy efficiency is therefore optimized.

 

A further benefit of not storing the water to feed around a plant is that it almost completely eliminates the risk of Legionella contamination. This is because the instantaneous temperature rise through the plate heat exchanger will kill any bacteria and the need to regularly raise the temperature of a store to above 60 degrees centigrade for a prescribed period.

 

The type of evacuated tube solar collector supplied by Stokvis is very simple to orientate for optimum performance, irrespective of the roof configuration. This offers an energy yield far in excess of the 528 kW/hr per square metre normally taken as an industry standard. In fact it is 61 per cent higher at 850 kW/hr over an average year. The installation can then be designed to fit the space available and the demand.

 

Enough solar energy reaches the surface of the earth every half hour to match mankind's consumption for a whole year. It all comes down to the economic realities of harnessing the raw heat or light and combining a solar thermal system with plate heat exchangers to supply hot water to the food industry is one of the more efficient means of doing so.

 

For further information on Stokvis Energy Systems, call 020 8783 3050 or visitwww.stokvisboilers.com.

-end-

Issued on behalf of:-                                

Stokvis Energy Systems                                  
96R Walton Road                                            
East Molesey                                                  
Surrey KT8 ODL                                              

Tel: 020 8783 3050 
e-mail:info@stokvisboilers.com

With compliments:-                                

Taylor Alden Limited
Unit 2 Temple Place
247 The Broadway
Wimbledon
SW19 1SD
 
Tel : 020 8543 3866
e-mail : margaret@tayloralden.co.uk