Navitron Renewable Energy and Sustainability Forum

SOLAR THERMAL => Solar Cooking (using vacuum tubes or more conventional methods) => Topic started by: Ivan on July 16, 2007, 12:57:45 AM



Title: Solar Tea, Coffee and Soup at Lower Brockhampton
Post by: Ivan on July 16, 2007, 12:57:45 AM
Here's Navitron practicing what it preaches! As 'Compostwoman' mentioned, we attended the Green Event at Lower Brockhampton Sat 14th July. After a dull start, we had glorious sunshine for the rest of the day. We started filling the solar kettles at around 9.30 and by 10am most were filled. There is considerable expansion in the water volume, so if you don't want them to overflow as they get hot, fill them to approx 1" below the upper limit of the black selective coating.

By 12.30 the water was hot enough to start serving. The soup was cooked directly in the tube, and worked very well - but obviously rather more effort to clean!
We served quite a number of cups of tea, coffee and tomato soup, but there were also quite a number of people who were 'suspicious' of the solar method and politely declined!

The solar-drinks raised quite a few eyebrows, and it was difficult to convince people that the water had not been heated by conventional kettle attached to our 440W PV array, which grid-fed approximately 3kW of electrical power into the National Grid during the event.

Two tips for experimenters:

1. Once water reaches boiling point, it's advisable to remove tube to a shaded location, as boiling can result in hot water being splashed over some distance
2. If you are not planning to decant entire contents of tube, beware of leaving part filled tubes in sunshine. Although the above point will not be a problem, there will be a small 'steam-blast' as you start to pour boiling water out of the tube - the boiling water comes into contact with very hot glass, which causes some to turn to steam as you start to pour. Again, removing to a shaded location once the tube has reached boiling point will minimise this issue.




Ivan


Title: Re: Solar Tea, Coffee and Soup at Lower Brockhampton
Post by: Ivan on July 16, 2007, 01:01:04 AM
Steve K of Navitron serving solar-heated drinks to bemused visitors
(http://www.navitron.org.uk/solarheat/solar_kettle/steve_serving_small.jpg)